Race chassis

[husaberg]

The pic Mike showed me at Levels of a 500 Yamaha frame "swiss-cheesed" was from Paul Treacy's collection and unfortunately isn't in the book.
But it did indicate the lengths they were prepared to go to in search of hard data.

Honda (More likely Kanemoto)did something with i think Biaggi's NSR250, that basically involved cutting out sections of the cross members, Bits of frame spars and engine/swingarm plates. I think they even unhooked the engine so it was not a stressed member.
From what i understand Max would not even tell Erv what he prefered for suspension, tires setting or anything until just before the race. Just in case it leasked out:nya:
I have a piece on it somewhere, Caladora who rode very different sweeping lines never had the same problems with the same bikes.

[Grumph]

According to Mike in the book, Cadalora was different to everyone. Very light on brakes on corner entry. Running alongside Rainey, the telemetry was vastly different. Rainey, very high brake pressure, Cadalora, very light pressure. Totally different style.

[Manu24]

(Advice from husaberg, I publish here)

Hola, mi nombre es Manu y yo soy de España, hace un par de años, he hecho a mi equipo ktuning.es una bicicleta de carbono, ahora les presento la siguiente evolución 80cc motor de 2 tiempos, espero que sea de su agrado, saludos !

https://www.facebook.com/Ktuning.es/
www.ktuning.es

328718328719328720328721328722328723

[guyhockley]

Team Roberts stuff, the picture of the storage rack on the second page shows the stages of fabrication of the frame spars (pre John Barnard). Also, note the rejected carbon swinging arm.

[husaberg]

Team Roberts stuff, the picture of the storage rack on the second page shows the stages of fabrication of the frame spars (pre John Barnard). Also, note the rejected carbon swinging arm.

Anyone able to franslate froggy to the Queens tongue.
I give up is all i know.


(Advice from husaberg, I publish here)

Hola, mi nombre es Manu y yo soy de España, hace un par de años, he hecho a mi equipo ktuning.es una bicicleta de carbono, ahora les presento la siguiente evolución 80cc motor de 2 tiempos, espero que sea de su agrado, saludos !

https://www.facebook.com/Ktuning.es/
www.ktuning.es

328718328719328720328721328722328723

Nice suff.

[Manu24]

My opinion, is that making a carbon motorcycle, inside a motogp team is impossible, they move huge budgets of money that is not yours, that means they must have results to keep getting this money from the sponsors. Carbon is a very big jump, everything is different, and it needs years until you reach a result that improves what already exists. But I am convinced that this will arrive, you just have to watch the automobile industry, or cycling, even the rest of sports. I am convinced that the time and dedication that I am going to give to my project, will not be in vain.

[Frits Overmars]

Anyone able to franslate froggy to the Queens tongue.Yep. But wouldn't you be more interested in a Spanish-English translation? I could do that too, if only there were more hours in a day.
But hey, Google is your friend. And Google Translator is always good for a giggle :p.

[Frits Overmars]

My opinion, is that making a carbon motorcycle, inside a motogp team is impossible... Carbon is a very big jump, everything is different, and it needs years until you reach a result that improves what already exists. But I am convinced that this will arrive...It has already been done decades ago, Manu. For example the Armstrong-Rotax 250 and the Heron-Suzuki 500. And of course the Ducati MotoGP.
Ducati gave up on carbon because they found it too difficult to design in the necessary amount of lateral flex that their front tire required.
But I think there is a better solution now: https://www.kiwibiker.co.nz/forums/showthread.php/145224-Race-chassis?p=1131030204#post1131030204
so we may see carbon GP-frames return in the not too distant future.
328757 328758

[Manu24]

It has already been done decades ago, Manu. For example the Armstrong-Rotax 250 and the Heron-Suzuki 500. And of course the Ducati MotoGP.
Ducati gave up on carbon because they found it too difficult to design in the necessary amount of lateral flex that their front tire required.
But I think there is a better solution now: https://www.kiwibiker.co.nz/forums/showthread.php/145224-Race-chassis?p=1131030204#post1131030204
so we may see carbon GP-frames return in the not too distant future.
328757 328758


I know those bikes, but they are very old, the world of composites changes every little time, in all this time has been much advanced. Carbon is not a metal, the position of the fibers, the type of fabric, resin used, resin ratio and fiber reinforcement, and of course the design, make it can be a disaster or an exceptional piece, only curing can change the result.

This means that a few tests are not sufficient for such a volume of variables. Just have to see in motogp, all these years of experience of aluminum, and still continue to discard many chassis in each test that do not work well.

Ducati of motogp, did not have carbon frame, simply did not have frame! A piece joins the engine with the steering shaft. If they had asked me before I would have told them that the carbon does not work well, kidding, they sure know a lot more than I do, but my prototypes will make me learn.

Finally I feel my English of google translate. I prefer to continue making motorbikes instead of learning another language

[Bert]

Good work Manu.
I've been following your facebook page for a while now, with interest.

Did it start as a school/uni project?

:niceone:

[guyhockley]

(Sorry, Husaberg, another foreign language one...but it is a picture gallery)

http://www.classic-motorrad.de/galerie/displayimage.php?album=23&pid=12482#top_display_media

The timeline is interesting - did he know about the Britten, or parallel development?

[Grumph]

(Sorry, Husaberg, another foreign language one...but it is a picture gallery)

The timeline is interesting - did he know about the Britten, or parallel development?

Possibly a bit of both...The Britten was publicised around 1989 but didn't go funny front end till the "slimline" in 91/92.
That front I'd reckon owes more to the european versions which were around before then.

John never claimed the layout was original, always quoted the Vincent as inspiration for the "frameless" style.
That one very definitely has a separate frame.
Nicely done though.

[husaberg]

Possibly a bit of both...The Britten was publicised around 1989 but didn't go funny front end till the "slimline" in 91/92.
That front I'd reckon owes more to the european versions which were around before then.

John never claimed the layout was original, always quoted the Vincent as inspiration for the "frameless" style.
That one very definitely has a separate frame.
Nicely done though.

I think the linkage ratios for and aft on the britten owe a little to Mike Watts and Mike/Murray? Aktin?akin? input.
Before they built the wisbone girder fork John obtained Hossacks (edit Claude Fior)Fax number from Alan Cathcart and sent him a fax asking for feedback/help/pointers he never did recieve a reply.

[husaberg]

It has already been done decades ago, Manu. For example the Armstrong-Rotax 250 and the Heron-Suzuki 500. And of course the Ducati MotoGP.
Ducati gave up on carbon because they found it too difficult to design in the necessary amount of lateral flex that their front tire required.
But I think there is a better solution now: https://www.kiwibiker.co.nz/forums/showthread.php/145224-Race-chassis?p=1131030204#post1131030204
so we may see carbon GP-frames return in the not too distant future.
328757 328758

Cagiva as well,
328810

Ducati had a Ciba Geigi M board frame built in the 70's for the TTF3.
328812328813
https://www.kiwibiker.co.nz/forums/showthread.php/145224-Race-chassis?p=1130363245#post1130363245
https://www.kiwibiker.co.nz/forums/showthread.php/145224-Race-chassis?p=1130363685#post1130363685

Here is the armstrong
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[husaberg]

(Sorry, Husaberg, another foreign language one...but it is a picture gallery)

http://www.classic-motorrad.de/galerie/displayimage.php?album=23&pid=12482#top_display_media

The timeline is interesting - did he know about the Britten, or parallel development?

here is some in JAPANESE AND NORWEIGAN
Hejira
Hejira is arabic meaning fly like the wind

http://www.hejiraracing.co.uk/publications.html
328819328820

[crbbt]

From what I've learnt at uni about compersite is that as soon as the force is not anglined with the direction of the fibre. It's relatively useless and has limited work cycles.

However there is a machine that lays single strands at a time. Not a cheap piece of equipment yet or quick

[husaberg]

From what I've learnt at uni about compersite is that as soon as the force is not anglined with the direction of the fibre. It's relatively useless and has limited work cycles.

However there is a machine that lays single strands at a time. Not a cheap piece of equipment yet or quick

John Britten invented the cats craddle carbon string method
Cheap as chips.
Make sure you use anodised alloy fittings
It works like this
http://l7.alamy.com/zooms/0522f70a9b8546e38b48068b173af0c4/mid-section-view-of-a-mans-hands-making-a-cats-cradle-with-string-et71n2.jpg
You do a wet lay of the CF string over the inlay bobbin fittings then cover with Prepreg sheet. in the desired directions
the string is the bones the Fibre sheet is the Skin/exoskeleton
If you look at these two pictures you can see some of the string lines
https://s-media-cache-ak0.pinimg.com/736x/ee/8d/fa/ee8dfaeb2b5d1eb94c5bb486beb0c250.jpg
http://www.sportrider.com/sites/sportrider.com/files/styles/medium_1x_/public/146-9504-web9.jpg
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Cycle World Archives
More than 20 years later, we're still enamored with John Britten's creation.
His “skin and bones” chassis fabrication was like nothing else seen previously. Placing aluminum spools at two wide lugs on each of the engine’s cylinder heads and around the steering head, he then wound carbon-fiber roving from spool to spool to produce the triangulated “bones.” Then he sheeted-in the spaces between the bones with carbon fabric. Wetted-out and cured, this made a compact and rigid whole. He credited the similar (steel) chassis of the Vincent Series-B as inspiration.

“I find that working with direc­tional materials has given me a real distrust of metal. Metals don’t seem solid to me anymore. I think of them as like very tightly packed sand.”
Wanting to avoid the frictional lock-up of telescopic forks during braking, he fabricated a carbon girder fork, which riders could easily accept because in its initial travel it felt just like teles (he knew a failing of many alternative bikes was that they spooked their riders by behaving oddly).
He and his group poured and machined their own engine castings, which are very smooth and of graceful organic shape, like tree trunks. He said nature had been an endless source of ideas.

[crbbt]

You have any information of that husa? Goggle took me to a very strange place

Should have waited for that 😂

[husaberg]

You have any information of that husa? Goggle took me to a very strange place

Should have waited for that 😂

Its also shown in the Britten video if you can find the full length version
He boasted he never even half used the full spool he was given by a boat builder

[jasonu]

From what I've learnt at uni about compersite is that as soon as the force is not anglined with the direction of the fibre. It's relatively useless and has limited work cycles.

However there is a machine that lays single strands at a time. Not a cheap piece of equipment yet or quick

Do they teach spelling at uni?:yes:



sorry, couldn't resist...

[husaberg]

Do they teach spelling at uni?:yes:



sorry, couldn't resist...

Trump is your elected president.
I could actually have resisted, But I didn't.:bleh:
328841
He could be the spokesman for KTM if this president thing fall through.

[crbbt]

Haha nah. All about autocorrect these days #geny

[Grumph]

From what I've learnt at uni about compersite is that as soon as the force is not anglined with the direction of the fibre. It's relatively useless and has limited work cycles.

However there is a machine that lays single strands at a time. Not a cheap piece of equipment yet or quick

Chris Haldane found out the hard way that John didn't understand directional fiber at first. The first version of the bottom wishbone broke when Chris was testing. John I believe blamed Chris for wheelying it....Chris won the NZ F1 title on his OW with a broken collarbone a few weeks later...

[husaberg]

Chris Haldane found out the hard way that John didn't understand directional fiber at first. The first version of the bottom wishbone broke when Chris was testing. John I believe blamed Chris for wheelying it....Chris won the NZ F1 title on his OW with a broken collarbone a few weeks later...

My previous post should have said Claude Fior rather than Hossack.
You could say that some of the development was "suck and see" i guess at times it sucks to be the test pilot.
In an article John gave 4 reasons for the Girder compared to his previous WP fork
First was to eliminate stiction 20KG on the WP. (insignificant on the girder only the bearings)
then eliminate fork flex which can lead to chatter (ironic considering)
The oportunity to use double wishbone geometry which allowed him to dial in both prodive and antidive in different parts of the suspension travel. (On the V1100 The first 80mm travel was prodive the last 40 was antidive.)
It was lighter and as it was at the extreme end of a motorbike so it also decreased the polar moment.

[Michael Moore]

When did Britten use a girder fork? I've only seen photos of a telefork and the Hossack/Fior-style FFE (funny front end).

[Grumph]

When did Britten use a girder fork? I've only seen photos of a telefork and the Hossack/Fior-style FFE (funny front end).

John described it as a girder - presumably to avoid the comparisons you and Husa have mentioned....Certainly each leg was a CF girder.

At a club night here there was a film shown of what went on at Daytona - incl an interview with John by the track announcer. There was quite a bit of muttering in the ranks from those who knew the people who had worked on the bike. The public face of the project was exclusively John. It was not until a local journo did an article for the HOG magazine about 3 years later that the number and names of those behind the scene became public.
Any credit for the source of the suspension layout came very much later and reluctantly. By that time most of the team wanted to ditch it anyway....

[husaberg]

John described it as a girder - presumably to avoid the comparisons you and Husa have mentioned....Certainly each leg was a CF girder.

At a club night here there was a film shown of what went on at Daytona - incl an interview with John by the track announcer. There was quite a bit of muttering in the ranks from those who knew the people who had worked on the bike. The public face of the project was exclusively John. It was not until a local journo did an article for the HOG magazine about 3 years later that the number and names of those behind the scene became public.
Any credit for the source of the suspension layout came very much later and reluctantly. By that time most of the team wanted to ditch it anyway....

Bob at link i feel was always sold rather short. along with Mike Brosnan and the many others. But Mike was especially when earlier versions were actually called the Brosnan Britten.
Link likely missed out of significant sales of electronics which were at the time world leading.
I guess its easier to sell the story if its david vs goliath rather than a team of daves.

[Michael Moore]

OK, just another example of sloppy terminology then. It annoys me, words have meanings, and a girder fork is quite a different thing from a Hossack/Fior FFE, even if they look somewhat similar from a distance in a dark room filled with fog. :)

cheers,
Michael

[Grumph]

OK, just another example of sloppy terminology then. It annoys me, words have meanings, and a girder fork is quite a different thing from a Hossack/Fior FFE, even if they look somewhat similar from a distance in a dark room filled with fog. :)

cheers,
Michael

Or side on with the "steering head" area obscured...From memory there was never a clear, naked, side on pic published till after John's death.
He was very sensitive about that.

[Michael Moore]

Being secretive about using someone else's good idea doesn't make much sense to me. If I can use an idea and credit the clever person who originated it, I'm still getting benefit of using the idea, and the clever person might be sufficiently pleased with getting the credit that they'll give me some more good ideas in the future.

Did Britten keep the bike covered up anytime it was not out on the track? If not, and random people could walk up and look, then where's the secret? Did the scrutineers have to sign NDAs? I suspect few people are fooled, they just wonder "why's he being so secretive about something so obvious?"

People can be so odd.

cheers,
Michael

[husaberg]

Being secretive about using someone else's good idea doesn't make much sense to me. If I can use an idea and credit the clever person who originated it, I'm still getting benefit of using the idea, and the clever person might be sufficiently pleased with getting the credit that they'll give me some more good ideas in the future.

Did Britten keep the bike covered up anytime it was not out on the track? If not, and random people could walk up and look, then where's the secret? Did the scrutineers have to sign NDAs? I suspect few people are fooled, they just wonder "why's he being so secretive about something so obvious?"

People can be so odd.

cheers,
Michael

John banned side on pics, reporter can be very accomidating when they want a story.

[Grumph]

Being secretive about using someone else's good idea doesn't make much sense to me. If I can use an idea and credit the clever person who originated it, I'm still getting benefit of using the idea, and the clever person might be sufficiently pleased with getting the credit that they'll give me some more good ideas in the future.

Did Britten keep the bike covered up anytime it was not out on the track? If not, and random people could walk up and look, then where's the secret? Did the scrutineers have to sign NDAs? I suspect few people are fooled, they just wonder "why's he being so secretive about something so obvious?"

People can be so odd.

cheers,
Michael

Due to the tight packaging in that area, it was very hard to see anything at all....I put that as the reason as when I first scrutineered that version at a NZGP meeting, I found that the steering damper was being used as the steering stops. It had been raced in that form at a number of NZ meetings before that one and it had never been picked up previously - or as has been suggested since, people didn't know what they were looking at...
The team manager at the IOM, told me privately when they got back that he'd heard the chief scrut say to his 2IC, "where the hell do we start on this"...

[Michael Moore]

I've added a page for Norman Hossack's bikes on my website:

http://www.eurospares.com/hossack.htm

Norman sent me some more photos he had and I decided there was enough material to consolidate it on one page. I've also included a couple of defunct webpages that Steve Burge, owner of Hossack #3, had made that I had saved for reference, though unfortunately I do not have all the photos to fully recreate those pages.

Some of the new photos are of the Hossack Ogier Laverda that was raced with some success by Alan Cathcart. I'd only found 2 or 3 photos of the bike in magazines so it was nice to get more information on it.

cheers,
Michael

[Frits Overmars]

Being secretive about using someone else's good idea doesn't make much sense to me. If I can use an idea and credit the clever person who originated it, I'm still getting benefit of using the idea, and the clever person might be sufficiently pleased with getting the credit that they'll give me some more good ideas in the future.

Did Britten keep the bike covered up anytime it was not out on the track? ... Did the scrutineers have to sign NDAs?I can very well understand being secretive about using someone else's good idea. If the idea really is that good, you try to keep your competitors from finding out about it as long as you can. Having said that, I fully agree that credit should be given where credit is due.

Scrutineers don't sign NDAs. If you won't let them check your bike, you're not going to race, simple as that. But scrutineers have a general obligation to keep their mouth shut about anything they see. It doesn't always work that way in practice...


John banned side on pics, reporters can be very accoaidating when they want a story.I know both sides of the medal. In the 1970s, when Yamaha first used an exhaust power valve on their 500 cc works bikes, I impersonated a technical editor for a living. All Yamaha team members had strict orders from Japan that no pictures of the bikes were to be taken. They draped blankets over the bikes at every pit stop, and anybody carrying a camera made them quite nervous.
When I entered the Yamaha works tent, the first thing I did was handing my cameras over to the chief mechanic, so he could have piece of mind.
The next evening he invited me to take pictures of the bikes, indicating which angles were allowed and which had to wait. I was the only one with these pictures for quite some time and I had a good relation that served me well until he was promoted back to Japan.

[Frits Overmars]

Being secretive about using someone else's good idea doesn't make much sense to me. If I can use an idea and credit the clever person who originated it, I'm still getting benefit of using the idea, and the clever person might be sufficiently pleased with getting the credit that they'll give me some more good ideas in the future.

Did Britten keep the bike covered up anytime it was not out on the track? ... Did the scrutineers have to sign NDAs?I can very well understand being secretive about using someone else's good idea. If the idea really is that good, you try to keep your competitors from finding out about it as long as you can. Having said that, I fully agree that credit should be given where credit is due.

Scrutineers don't sign NDAs. If you won't let them check your bike, you're not going to race, simple as that. But scrutineers have a general obligation to keep their mouth shut about anything they see. It doesn't always work that way in practice...


John banned side on pics, reporters can be very accoaidating when they want a story.I know both sides of the medal. In the 1970s, when Yamaha introduced an exhaust power valve on their 500 cc works bikes, I impersonated a technical editor for a living. All Yamaha team members had strict orders from Japan that no pictures of the bikes were to be taken. They draped blankets over the bikes at every pit stop, and anybody carrying a camera made them quite nervous.
When I entered the Yamaha works tent, the first thing I did was hand my cameras over to the chief mechanic, so he could have piece of mind and I could have a chat.
The next evening he came and invited me to take pictures of the bikes, indicating which view angles were allowed and which had to wait. I was the only one with these pictures for quite some time and we had a good relation that served me well until he was promoted back to Japan.

[Michael Moore]

Frits, your race activities were at a significantly higher level than mine and money/careers were at stake. It doesn't matter how many wonderful secret ideas I have, I'm still not a fast rider so all they really end up doing is make me feel good. :)

If a tuner comes up with something that gives an advantage, they'd of course want to keep it for them self as long as possible. But that is keeping their own idea secret, not someone else's. If they come up with a modification/improvement of someone else's idea, then that mod seems fair to me to hold close.

cheers,
Michael

[Grumph]

I can very well understand being secretive about using someone else's good idea. If the idea really is that good, you try to keep your competitors from finding out about it as long as you can. Having said that, I fully agree that credit should be given where credit is due.

Scrutineers don't sign NDAs. If you won't let them check your bike, you're not going to race, simple as that. But scrutineers have a general obligation to keep their mouth shut about anything they see. It doesn't always work that way in practice...


Very true...as it happens when the bike came back for recheck, I was busy with a lad from a well known race family here in NZ who was trying to convince me to pass his TZ with his wet rims fitted - less discs....Some mothers do 'av em...So my off sider passed it. The team member who made the steering damper had waited till John was out of sight and come over to thank me. They'd been trying to get John to fit steering stops for months apparently.
Odd setup where you have to wait for officials to sort out a basic error in construction.

No one was interested in why it had failed. That was the season here where John had been paid by MNZ to front the bikes at NZ championship events - and it had just got out a day or so before...His competitors were enraged that they were paying him to race against them....

[husaberg]

Very true...as it happens when the bike came back for recheck, I was busy with a lad from a well known race family here in NZ who was trying to convince me to pass his TZ with his wet rims fitted - less discs....Some mothers do 'av em...So my off sider passed it. The team member who made the steering damper had waited till John was out of sight and come over to thank me. They'd been trying to get John to fit steering stops for months apparently.
Odd setup where you have to wait for officials to sort out a basic error in construction.

No one was interested in why it had failed. That was the season here where John had been paid by MNZ to front the bikes at NZ championship events - and it had just got out a day or so before...His competitors were enraged that they were paying him to race against them....

Lots of people used to use the circlip on a rear disc master cylinder as a brake stop as well.
*I note the steering damper broke at Monza locking the steering.
I think the main problem is illistrated by how the complete spars would likely have to be remade to accomidate a sterering stops as you can't just weld on some stops.
https://www.nzonscreen.com/title/britten-backyard-visionary-1993
I picked Shands voice well before i seen him;)

oh here is one on Bamboo dick
https://www.nzonscreen.com/title/richard-pearse-1975


Britten's girder forked parallelogram
John Britten recently died of cancer in late 1995. Although his death is considered by some to be the greatest loss to modern motorcycling, his legacy lives on in his V-1100 supertwin race bike. For most of the motorcycles featured in this paper, their alternative front suspension systems are their raison d'etre. Not so for the Britten. While the Britten has an alternative front suspension system, it has a whole host of other technological marvels as well.
The first iteration of John Britten's race bike used a traditional White Power upside-down telescopic fork. In a move for more rigidity, suspension geometry flexibility, and the ability to separate suspension and braking forces, Britten created a new front end. Britten's handmade alternative front suspension is a modern redevelopment of Norman Hossack's girder/wishbone parallelogram suspension or systems designed by Claude Fior. The Hossack design was an update of the Vincent Girdraulic fork which itself was an update of systems used at the dawn of motorcycling (Alan Cathcart, Superbike Magazine, January 1993). This fourth design iteration was chosen, much like the SaxTrak, because of the versatility of the geometry. But it is a girder fork nonetheless.

Britten had four reasons for scrapping the proven race-quality White Power telescopic fork. He wanted to eliminate sliding friction under braking, raise rigidity, create an adjustable system, and reduce weight. While achieving all of these goals, Britten also managed to reduce wheel chatter common on telescopic forks, enhance braking, and improve handling (Cameron, 1992:36).

Because the girder design uses rotational bearings in place of telescoping bearings on traditional forks, bearing area and motion is significantly reduced and stiction under braking is almost eliminated. The telescoping action of traditional forks means that the front wheel is constantly accelerating or decelerating relative to the bike itself. This relative motion of the wheel and tire must either be absorbed by the tire, the fork or the brakes and often manifest itself as a "chatter" in any or all of those components. The wide expanses of carbon fiber and the girder design assure that unlike traditional systems, the front wheel position relative to the bike is constant even with extreme suspension movement. This creates a more stable platform under extreme forces (better braking) and a more direct feeling as rigidity is increased (better handling).

In order to create an adjustable system, Britten knew that a double wishbone system would be the most flexible design. Either length or angle of either wishbone in the parallelogram could be changed to affect the handling of the suspension. Britten's system can be set up for no dive under braking, pro-dive or anti-dive or a combination of any of these. At the moment current racers, having grown up on telescopic forks, like the reassurance of dive under braking. Thus Britten has set up the forks currently to dive for the first 80mm of travel and then rise for the last 40mm (Cameron, 1992:38). But as racers begin to understand the strengths of Britten's design, the fork geometry can be setup for any desired action: constant wheelbase, pro-dive, anti-dive, no-dive or any combination of these. Single wishbone systems, such as the Bimota Tesi, are not nearly as adjustable by design. The two purpose-built racebikes discussed here (the Saxon-Triumph and Britten) both have adjustable steering geometry to make a bike that can be competitive at different kinds of racetracks. By design, materials and construction, Britten was able to lighten the weight of the whole front end, reducing polar moment and making for lighter steering and better handling overall.

The Britten girder fork also has another key benefit it shares with all of the alternative suspension systems discussed in this paper. It too suspends with a modern nitrogen-charged Ohlins monoshock, probably the best developed if not most researched suspension device made. Thus it too does away with the problems of trying to make both forks in a telescopic system do the same thing at the same time. The one shock is easily adjustable, accessible, rebuildable, and lighter than the suspension systems held within the fork tubes of a traditional system.

The faults in the Britten girder parallelogram suspension are few. One issue in common with the SaxTrak and Telelever designs discussed above is that the braking forces do not have the shortest or most direct path to the frame. In all three cases, forces acting on the tire and wheel must travel some distance up mock fork tubes or a carbon fiber girder to reach arms that attach to the engine or frame. The later discussed RADD and Tesi systems have the shortest path possible for braking forces into the frame and do so at a lower height on the bike, lowering the center of gravity and easing steering. The low weight of the Britten system in addition to the rigidity of the materials make that fault almost imperceptible. Britten has shown us that an updated version of the girder fork that was used at the dawn of motorcycling is still a viable option that has many benefits of traditional telescopic forks.

More than any other motorcycle in the world, the Britten V-1100 showcases the integration of a host of design features that, given a clean sheet of paper and an unlimited budget, designers would unerringly adopt as the best way to achieve a given design target. Features that for commercial or marketing reasons, they are simply unable to adopt themselves. Alan Cathcart, Superbike, May 1993, p.42.


Extract from an article first published in “Fast Bikes” magazine.
© Ian R Cramp September 2000


People in pubs are very quick to condemn telescopic forks, and they usually have any number of perfectly sound reasons to back up their views – too heavy, stiction, lack of rigidity, poor geometry, etc etc. However, the telescopic front fork has been with us in a relatively unchanged form for about 50 years, so there must be something good about it. As is so often the case in engineering, some solutions don't look particularly good, but when there is no "good" answer to be found, you have to go for the one that is the least bad. Maybe this is the case with a tele – it has its faults, but it does the job, and nothing else has threatened it despite the best efforts of whole pubs full of engineers for decades.

I therefore started my investigation into my funny front end from the opposite direction – by having a good look at conventional forks, and working out what were their good points, which had made them so popular for so long. I decided, after a great deal of thinking and research, that the most important thing of all was the way you could mount clip-ons directly to the fork tubes. Being able to feel what the front tyre is doing is crucial to controlling a bike, and any system which has a sloppy linkage between the tyre contact patch and the handlebars is therefore an instant non-starter. The Bimota Tesi was particularly shite in this respect, and so was the first Elf, though the Elf team soon learned from their mistakes and their later versions had a much more direct and rigid steering link which was nowhere near as bad.

Secondly, whilst telescopic forks are heavy, a fair proportion of that weight is sprung. Weight is always a bad thing on a bike, but unsprung weight is double-bad. If you look at many really quite well thought out funny front end designs (like the BMW Telelever and the Tryphonos, for example) you see that they carry much more unsprung weight; things like the steering head, bearings, clamps, and other stuff which are mounted on sprung parts of the bike in a conventional setup become unsprung in these arrangements. Not good.

Another key advantage of forks is their geometry. People can write whole books about offset, trail, and the simple up/down travel of a tele, but the bottom line is that it appears to work better than anything else using current technology. Aha, the pub philosophers say as they prop up the bar, but as you brake and the front dives, so the rake, trail, and wheelbase change. Well, yes, but so what? It seems to work pretty well, so what the hell? It can't be denied that some other systems, with different (they say "better") geometries, which maintain a constant trail or a constant castor or a constant this and a constant that, nevertheless feel rather weird to the fellow holding the bars. Since absolute confidence in the ability of the bike to react as it intuitively should at all times is the most vital part of riding quickly on unfamiliar roads, systems like this were to be rejected out of hand as far as I was concerned.

A big problem with bikes is that they need a lot of suspension movement, and this makes it very difficult to find any suspension system, other than teles, with the right geometry. Modern racing cars have so little suspension movement that there are actually not even any balljoints on the ends of an F1 car's wishbones – the flex of the joint itself is all that's required. By contrast, bikes have about ten times as much movement for each end, and this means big problems for geometry. For example, if a car's wishbone is two feet long, it will always be sitting at pretty much the same angle when the end moves half an inch or so. The opposite applies to a bike. Taking the rear swinging-arm as an example, it must allow about six inches of travel, and as it's only a foot and a half long, it must move through about 15 degrees of arc – therefore having a huge effect on the geometry of the rear end. The longer you make the arm, the less is the angle it must move through – which is why we have a trend towards longer and longer swinging arms, and why the Yamaha YZF-R1 therefore has a stacked gearbox.

Now, as the arm gets longer, the path through which the wheel spindle moves becomes straighter. If you could make the swinging arm infinitely long, the spindle would move through a straight line – just like a telescopic fork! Years ago, there were actually rear ends like this on bikes before swinging arms became the norm – the Norton plunger or the Triumph sprung hub for example. The problem with having straight-line motion of the rear spindle, however, is that the chain tension changes too much with suspension movement. The angularity problem associated with front swingarms also applies to leading and trailing link type front forks, which are surprisingly popular; ten million Honda C50s can’t be wrong, and Moto Guzzi fitted them to their GP bikes for years with some success. I’m not sure about this, but I believe that Bob MacIntire had leading-link forks fitted to the Gilera on which he set the first ever 100mph TT lap (don’t all write in if I’m wrong – the only reason I don’t know for sure is that one of those pub bikers borrowed the book and hasn’t given it back). JPS Norton-Cosworth Challenge bikes had a similar Earles-type set-up, which can be examined minutely at the National Motorcycle Museum, and systems were fitted to TZ350s as late as the 1980s by privateer riders who were only too happy to put the standard teles in the bin.

Nevertheless, in light of what I've already said about steering links, geometry, and unsprung weight, I didn't consider having any sort of swinging-arm or link on the front; and anyway, it's already been done. Designs like the Bimota Tesi and the ASP are shite, but something like the Tryphonos project was as good as these things can get. There was no point in my trying another.

Since I wasn't keen on going for teles, there was only one other choice really – the girder fork, as fitted to millions of bikes before the last war, and still very often seen in 1951, the notional "styling date" for my bike. To be honest, I often wonder why designers abandoned girder forks in the first place, as they're fine bits of kit. My trusty 1929 Velocette with its spindly girders that look like drinking straws is still plenty good enough for a knee-down now that it can be treated to modern tyres and tarmac. The conventional girder fork reached its apogee of development in the 1950s with the Vincent Black Lightning (this is the bike in the famous picture of the herbert doing 150mph on the Bonneville Salt Flats by lying flat and wearing only his swimming trunks). The Vincent’s girder fork legs were aluminium forgings – the perfect material for the job, though I thought I could make steel tube ones which would be stronger and just as light.

The bike industry abandoned girder forks more or less by accident. There was nothing wrong with them at all really, but no-one bothered to fit them with good geometry or good damping (the technology of the time just wasn’t up to it, and with crap roads and tyres, no-one could go fast enough to notice). When Norton came along with their telescopic “Roadholder” forks, everyone assumed that the reason they were better than the girders of the day was simply because they were telescopic. Not so; it was that the package allowed enough space for the designer to get a half-reasonable spring-damper unit on the front end of a bike for the first time. Also, I'm sure that the public were influenced by the idea of buying a bike with what they thought was the same sort of suspension as Geoff Duke was using on his Norton GP bike, and all of the British manufacturers immediately jumped on to the fashion bandwagon. Italians were not influenced by the fashion in the same way, and they went on to kick Norton’s arse with link-type suspensions for several years.

Because girders faded away rather than being superseded, a few enlightened frame constructors have continued to use them in conjunction with the modern damping systems now available, which would have transformed the old ones. Hossack, Cobas, and ROC all had a go with varying degrees of success, but it was the Britten which really put girder forks back on the map – with a system which differs only in detail from the Vincent of fifty years before, with the aluminium forgings replaced by carbon fibre. Ironically, it was the carbon bits that gave the most trouble, with some frightening structural failures occurring before the design team got their act together.

A crucial advantage of girders is that, because their movement is controlled by a couple of links (like wishbones), you can vary the geometry quite easily by changing the length and angles of these links. Rising-rate, falling-rate, anti-squat, anti-dive; rake, trail and offset either increasing, decreasing, or staying the same – all are more or less possible by changing the lengths and angles of a couple of links by a few millimetres or a few degrees. This is known in engineering as a four-bar link set-up, and it has been used to bore the arses off engineering students for centuries.

The four-bar link is basically one fixed axis with a bar on each end, with the ends of those two bars joined by another link. By changing the lengths of the bars, an infinite variation of displacements, velocities, and accelerations is possible – turning the four-bar link into (for example) the double-wishbone set-up of a racing car, or the parallelogram rear suspension of a modern-day Moto Guzzi – or a front girder fork.

Now, it so happens that when I was studying dynamics of mechanical systems at university, I was tortured at length with learning the ramifications of these great variations. I studied the geometries, the displacements, the velocities, the accelerations (both linear and angular) and I derived all sorts of equations for maximising, minimising, and optimising any or all of them. It wasn't boring in the way that watching a girder rust is boring, it was more like being methodically and rhythmically beaten over the head with a rusty girder. I was mightily pissed off, but I continued to wrestle with it manfully because, in my youthful naivety, I really thought that I would need to know all of it to become an engineer, and it would ultimately be very handy. Imagine my surprise when, nearly fifteen years later as I looked at this front end, it actually was – just about the first time that anything I was taught in university (apart from in the boxing club) has ever been of the remotest use.

Because of what I said earlier about forks, I thought that it would be smart (and safe) to fix the geometry of my girders so they moved the front wheel in exactly the same way as a set of telescopics. This would mean that I wasn't sticking my neck out too much, and also that the front end would have the same sort of feel that riders are used to. It would have been an easy job to design such a system, but the large suspension movement of a bike caught me out yet again – the front wheel has to move about six inches up and down, and modern spring/damper units only have about two inches of travel, so that means you need some sort of link in the system – you can’t just bolt the bottom of the shock to the fork and the top of it to the top yoke. This threw a surprisingly big spanner into the works, and I had to study (and reject) many ways of getting round it before I came up with an acceptable solution.

A spin-off from the solution I settled on – using the bottom link as a rocker to act on the bottom of the shock – was that the front end became genuinely rising-rate, that is geometrically rising-rate, without the need to put progressive springs and damping in like they do with some teles.

A good rising-rate characteristic is vital on a front end. It must provide the lightest of springing and damping to cope with keeping the bike pointing in the right direction when hard on the power (so there’s hardly any weight on the front and the tyre is barely skimming the surface), and also it must be beefy enough to absorb bumps even when hard on the brakes, when the back wheel is off the deck and the nose is trying to bury itself into the ground. The conventional solution, largely pioneered in the 1970s by Kenny Roberts Snr, Yamaha, and their Ohlins partners, centres around dual-rate springs (soft for most of their travel, but much harder for the last bit) with the latest refinement being dual-rate damping (ie damping which can be set to respond to high-speed and low-speed movements differently). Obviously, this works very well indeed, and with a set of forks costing eight grand it bloody well should do, too. I was hoping that my scheme could be just as good, but lighter and more rigid, as well as looking the part for a classically-styled bike and being able to use a £600 over-the-counter shock absorber to do all of the springing and damping required.

Even though I had most of the basics of the design sorted in less than a day, I spent more than a week agonising over various aspects, and I’m still not happy about some of them. It makes sense to get your worries in sooner rather than later, because it’s a lot easier moving a line across a CAD screen than it is chopping bits of steel and moving them around when you find out, too late, that you’ve made a cock-up. For this reason, I like to put in a great deal of effort at the design stage, keeping the famous British Army dictum in mind – train hard, fight easy. Cutting metal is when the bullshit must stop – as you’ll find out in the next exciting episode, when my lily-white hands move off the keyboard and get down to some honest toil in the welding shop.


http://www.cycleworld.com/2015/03/23/history-simplicity-and-effectiveness-of-motorcycle-telescopic-fork-tech-editor-kevin-cameron
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[Grumph]

Lots of people used to use the circlip on a rear disc master cylinder as a brake stop as well.
*I note the steering damper broke at Monza locking the steering.
I think the main problem is illistrated by how the complete spars would likely have to be remade to accomidate a sterering stops as you can't just weld on some stops.
I picked Shands voice well before i seen him;)

I understand the team had steering stops worked out and ready to fit - unknown to John.....
I wrote the rule on brake pedal stops in the MNZ book....
Shand's been quoted once above plus was responsible for the fight over appearance money. Lot of people never fogave him for that.

[husaberg]

I understand the team had steering stops worked out and ready to fit - unknown to John.....
I wrote the rule on brake pedal stops in the MNZ book....
Shand's been quoted once above plus was responsible for the fight over appearance money. Lot of people never fogave him for that.

I hate that rule:lol:
As i recall the MNZ's stance was the extra bums on seats more than paid for the Britten apperence money which was to cover travel etc.
More of a worry was the changing of the rules that allowed the bikes to race in the then superbike class.
But yeah i can confirm the two Johns were mates.
Some pics the first two are not britten the first is Hossac but esentially the same. esp the second one
328921328920

328918328919328922

[Michael Moore]

The upper left one with the Middleton link is CAD by Peter Fouché from the FF list.

There's a fair bit of Norman's stuff on the new page on my website (mentioned a few posts earlier) that hasn't been seen before.

[husaberg]

The upper left one with the Middleton link is CAD by Peter Fouché from the FF list.

There's a fair bit of Norman's stuff on the new page on my website (mentioned a few posts earlier) that hasn't been seen before.

Oh i just went off the pic name.
with regards to the front end i think John never wanted side on pics was to do with the time it took him to figure out the link lengths and leverage ratios.
I see personally very little difference between the Britten from end and a Web fork. Other than damper and materials. and a few details
or a vincent set from later.
328938328939328940
here is an early Fior pic
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I don't recall John ever saying anything other than they were an updated vincent fork as was the chassis.
As i said earlier he even asked Fior for help.
The Britten to me wasn't about any one detail but a huge array of neat and clever stuff molded into into one cohesive vision that was actually sucessfull.
http://www.racecraft.de/Projects/Girder-Fork/girder-fork.html
These below are for a mountain bike but i sure like them, they look conventional as well.
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[Frits Overmars]

I see personally very little difference between the Britten from end and a Web fork. Other than damper and materials. and a few details or a vincent set from later.There is a fundamental difference: a Web fork like the Vincent has steered suspension; a Hossack fork like the Britten has suspended steering.

[Michael Moore]

Norman's later street bikes (like his current 800 Ducati) has both, since the damper attaches to the upright and pivots with it instead of attaching to the a-arm.

http://www.eurospares.com/graphics/Hossack/IMG00278-20140124-2008a.jpg

That does have the advantage of not feeding suspension loads into the lower ball joint, instead they go straight to the wheel bearings. I suspect it was also done when radiators started getting in the way of mounting dampers on the lower a-arm.

cheers,
Michael

[Frits Overmars]

Norman's later street bikes (like his current 800 Ducati) has both, since the damper attaches to the upright and pivots with it instead of attaching to the a-arm. http://www.eurospares.com/graphics/Hossack/IMG00278-20140124-2008a.jpg
That does have the advantage of not feeding suspension loads into the lower ball joint, instead they go straight to the wheel bearings. I suspect it was also done when radiators started getting in the way of mounting dampers on the lower a-arm.Found it.
The ratio from wheel travel to shock travel appears to be about 1, and suspension units hardly offer more than 50 mm travel, so this would severely limit wheel travel, wouldn't it? It would also sacrifice the possibility of obtaining progressive suspension behaviour despite using a linear schock. And you need progressiveness up front.

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[Michael Moore]

FYI Norman's earlier patent is GB2121364a. On the most recent bike, his 800 Ducati, I think he's using an Ikon (Koni copy I think) from Australia. It doesn't seem a problem to get the small body dampers (Falcon, Ohlins, Penske, Noleen, anyone that does VMX dampers) with 100mm of travel.

There are always trade-offs, the prioritization of them can sometimes vary between people.

[husaberg]

There is a fundamental difference: a Web fork like the Vincent has steered suspension; a Hossack fork like the Britten has suspended steering.

Yes i kind of understood that, but what i was more getting at is it was a progressional evolution of the girder design, rather than a revolution.
Look at swingarms, dual shock, cantalever, non linkage, linkage. Its a natural progession.

https://2.bp.blogspot.com/-FUzoHIqJrr4/VZa4uMR5uLI/AAAAAAAAAwQ/HGq6P-kd7pw/s1600/Suspension_2.jpg
To me all the wishbones are at the wrong end. ie they should be closer to the wheel.
A simple mid 60's greeves style leading link seems to offer much greater oportunities for unsprung weight reduction.
http://www.greevesmotorcyclesltd.com/bikes/tfs_frame_1.jpg

[Michael Moore]

The LLF, especially one with shorter links, offers less wheel path control than a dual-link/dual a-arm system like a Hossack or the girder. The LLF gives you an arc, the length of the link determines how flat that arc might be, and the relative heights of the axle and link pivot determine the ultimate wheel path. With the deformable quadrilateral you get more options (good as well as bad) on where the wheel goes. The distance the axle is from the pivots on the upright can have a big affect on things as a little change in the link geometry can be amplified quite a bit if the axle is farther away. I think LLFs have a lot to offer vs teleforks, but both are steered suspension systems.

The automotive suspension illustration is a suspended steering system and so is different from a girder which is a steered suspension system.

If you've got to have a steering head on the frame (one that is a big part of the structure and not just something light to support bars that link to the upright) on a relatively short travel (RR) chassis then the girder might well have some advantages over teleforks if properly designed and built. You could eliminate a lot of the sliding friction, there's more control over wheel path, the upright might be less flexible than telefork legs, and you can adjust dive/squat reactions. How things balance out between steered mass/radius of that mass, unsprung weight, etc is going to depend on the details.

cheers,
Michael

[Grumph]

I suspect neither you nor I, Michael, are dealing with up to date USD forks on a regular basis - and I certainly was not aware of how far the anti friction developments have gone. You really must get a copy of Mike Sinclair's book, he goes into good detail about how internal friction was reduced as the USD forks were developed.
There's still returns to be had from "conventional" fork developments for a while yet.

[husaberg]

The LLF, especially one with shorter links, offers less wheel path control than a dual-link/dual a-arm system like a Hossack or the girder. The LLF gives you an arc, the length of the link determines how flat that arc might be, and the relative heights of the axle and link pivot determine the ultimate wheel path. With the deformable quadrilateral you get more options (good as well as bad) on where the wheel goes. The distance the axle is from the pivots on the upright can have a big affect on things as a little change in the link geometry can be amplified quite a bit if the axle is farther away. I think LLFs have a lot to offer vs teleforks, but both are steered suspension systems.

The automotive suspension illustration is a suspended steering system and so is different from a girder which is a steered suspension system.

If you've got to have a steering head on the frame (one that is a big part of the structure and not just something light to support bars that link to the upright) on a relatively short travel (RR) chassis then the girder might well have some advantages over teleforks if properly designed and built. You could eliminate a lot of the sliding friction, there's more control over wheel path, the upright might be less flexible than telefork legs, and you can adjust dive/squat reactions. How things balance out between steered mass/radius of that mass, unsprung weight, etc is going to depend on the details.

cheers,
Michael

I think you are missing what i am saying Michael.
The car suspension pic was to illistrate their is nothing amazing about the concept of either the britten or the Hossac
i just feel the links are at the wrong end. in regards to unstrung weight.
There is nothing i can think of to stop someone adding parallelogram link to a leading link.
Its likely even been down before they were all the rage in the 50's and 60"S. Grumph?
nor is a single link any worse than a tele fork.
I personally don't see suspended steering as being a great advantage as it has to steer a wacking great gyro anyway. that would be the greatest force to overcome rather than a few kgs.
A alternative Front suspension to me, needs to be light, perferably lighter than a conventional fork, adjustable geometry and fixable, but more importanley to me it needs to feel not funny.

[Grumph]

I think you are missing what i am saying Michael.
The car suspension pic was to illistrate their is nothing amazing about the concept of either the britten or the Hossac
i just feel the links are at the wrong end.
There is nothing to stop someone adding parallelogram link to a leading link.
Its likely even been down before they were all the rage in the 50's and 60"S. Grumph?
I personally don't see suspended steering as being a great advantage as it has to steer a wacking great gyro anyway.
Front suspension to me needs to be light perferably lighter than a conventional fork adjustable and fixable, but more importanly it needs to feel not funny.

If you want the links at hub height, you're looking at a "headless" frame IMO. It's been done but without noticeable success.
Raises too many packaging problems IMO.

[F5 Dave]

Careful. The feet forward zealots will be along shortly.

[husaberg]

If you want the links at hub height, you're looking at a "headless" frame IMO. It's been done but without noticeable success.
Raises too many packaging problems IMO.

I was more thinking a 4 link leading link steered from the steering head.
with a rocker arms for the shock much like the last RC250's had prior to the Prolink.
I think that orange German MX bikes that used Rotax and i think maico engines had something similar.
KRAMER i can't find a pic of that either.

[guyhockley]

One possible advantage of girder front ends, steered or not, could be variable stiffness between fore'n'aft and lateral? Something like MotoCzysz tried with their front fork, a 6:1 ratio was claimed, I think.

[Michael Moore]

I looked at a 125GP Ohlins fork, must have been 15 years ago, and was impressed at how little friction it had.

But teleforks are one of those things that if a person were starting with a clean sheet and not 70 years of legacy production/development they would probably not be high on the list of good engineering solutions. I can build a Hossack FFE with a good modern damper in my garage, high-quality teleforks would have to be bought in.

Unsprung weight is important, but steered mass is also important, and complexity/ease of construction is important, and wheel path is important and . . . .

As Tony Foale says when he starts his seminars, the only thing you can't change is "just one thing".

I've got a couple of FF projects in the planning/accumulating parts stages, though I don't think I qualify as a zealot quite yet. I want to see if there's a reason for zealotry first. :)

cheers,
Michael

[F5 Dave]

Ohh, ohh. Is it long wheelbase and rearward weight distribution?
If there's a photo make sure to cultivate a suitable beard.

[Michael Moore]

A track bike a couple inches longer than a MotoGP bike, under 200 pounds, RS125 wheels (Dymag)/brakes (Brembo CNC/billet 4 piston caliper), 50hp KTM 250SX engine, Hossack FFE, probably Penske dampers front and rear. Basically a Gurney Alligator with FFE and a lot less weight. A near 50/50 distribution seems likely, depending on how much an airbox interferes with my nether regions. As usual with my bikes, I'll be the limiting factor on how fast it goes, but I do intend to get someone reasonably fast to give it a try.

My beard is and has been for decades quite suitable, at least as an exemplar of hirsute elegance!

:)

[husaberg]

A track bike a couple inches longer than a MotoGP bike, under 200 pounds, RS125 wheels (Dymag)/brakes (Brembo CNC/billet 4 piston caliper), 50hp KTM 250SX engine, Hossack FFE, probably Penske dampers front and rear. Basically a Gurney Alligator with FFE and a lot less weight. A near 50/50 distribution seems likely, depending on how much an airbox interferes with my nether regions. As usual with my bikes, I'll be the limiting factor on how fast it goes, but I do intend to get someone reasonably fast to give it a try.

My beard is and has been for decades quite suitable, at least as an exemplar of hirsute elegance!

:)

What is the penske actually like? they looked like a nice quaility bit of kit when they csame out in the mid 90's, i remember Rob Muzzy using one, then they sort of faded into obscurity?
Def never seen one in Kiwiland. Did they just go back to just doing car stuff?
Personally teles do a lot of things badly, but i think they looked the part back in the 50's and had room for dampers. The problem is they have now been that highly devleoped replacing them is going to be a big ask even for a better solution.

[Michael Moore]

That's the first time I've heard anyone refer to Penske as having become obscure as that isn't the case in the USA.

FWIW, there's a guy on my chassis list who is a machinist for Penske, mainly on the F1 dampers. Ian Drysdale paid him a visit last summer when he was over here (Dave has one of Ian's V8 engines). Ian is definitely no slouch as a machinist, but he said that the level of work Dave was showing him left him slack jawed.

Sure, the F1 stuff is probably a step or 5 above what we mere mortals can afford. But Dave once told me when I was asking about how Penske compared to some of the other similar big names that "I build these things and know what I've got to do to hold the tolerances I have to hold, and it is not easy". The other brands were OK, but he didn't seem to think their, shall we call them, general public dampers were built to as high a standard as the Penskes aimed at the same market. No castings to save money, everything is machined from solid, etc.

Now I expect that if you are a MotoGP team that Penske, Ohlins, WP and probably several others can all supply equally wonderful dampers, but those are limited production to a high standard and probably even higher cost. For a standard 2 way adjustable at around $900 each there seem to be a lot of choices, and I expect that all of them would work well enough that my limited ability wouldn't be able to distinguish between them in a blind test, presuming they are all set up properly to begin with.

I'm probably going to buy Penske because they are made here, every one of them is made to order, they are all run on a dyno to check them before sending out, and lots of suspension shops are familiar with them. I also like that Penske actually encourages owner maintenance of the dampers and provides manuals for that purpose, and it doesn't seem like they need a drawer full of special tools to work on them.

But if my local suspension guru really liked Ohlins, or JRi, or Elka, or Wilburs, or WP or or or . . . . I'd give serious thought to buying what they preferred to work on and felt most comfortable tuning, because at my level any good damper is probably going to be way better than I need.

[husaberg]

That's the first time I've heard anyone refer to Penske as having become obscure as that isn't the case in the USA.

FWIW, there's a guy on my chassis list who is a machinist for Penske, mainly on the F1 dampers. Ian Drysdale paid him a visit last summer when he was over here (Dave has one of Ian's V8 engines). Ian is definitely no slouch as a machinist, but he said that the level of work Dave was showing him left him slack jawed.

Sure, the F1 stuff is probably a step or 5 above what we mere mortals can afford. But Dave once told me when I was asking about how Penske compared to some of the other similar big names that "I build these things and know what I've got to do to hold the tolerances I have to hold, and it is not easy". The other brands were OK, but he didn't seem to think their, shall we call them, general public dampers were built to as high a standard as the Penskes aimed at the same market. No castings to save money, everything is machined from solid, etc.

Now I expect that if you are a MotoGP team that Penske, Ohlins, WP and probably several others can all supply equally wonderful dampers, but those are limited production to a high standard and probably even higher cost. For a standard 2 way adjustable at around $900 each there seem to be a lot of choices, and I expect that all of them would work well enough that my limited ability wouldn't be able to distinguish between them in a blind test, presuming they are all set up properly to begin with.

I'm probably going to buy Penske because they are made here, every one of them is made to order, they are all run on a dyno to check them before sending out, and lots of suspension shops are familiar with them. I also like that Penske actually encourages owner maintenance of the dampers and provides manuals for that purpose, and it doesn't seem like they need a drawer full of special tools to work on them.

But if my local suspension guru really liked Ohlins, or JRi, or Elka, or Wilburs, or WP or or or . . . . I'd give serious thought to buying what they preferred to work on and felt most comfortable tuning, because at my level any good damper is probably going to be way better than I need.

Looking at their distributer map it looks like they have concentrated on the US market.
328967

[Grumph]

They hit the UK market hard in the 90's. V & M used them to win a couple of British titles I believe.

Where I think things fell down was that a lot of the UK magazine projects get shocks on favourable terms for the publicity value.
The Penske distributor apparently didn't want to play at that game. So you very seldom read about them now outside the US.

[Michael Moore]

I suspect that Penske might have a little barrier to sales outside the USA from their "made to order, tested before shipping" business model. I thing it is going to be a lot easier to have a large number of pre-boxed "standard" dampers stored on shelves in another country for sale vs setting up a custom assembly/dyno test operation.

It looks like Ohlins has a "budget line" manufactured in Thailand or similar location, Penske has a higher bottom limit to what they make and a narrower target market/focus.

There seem to be lower barriers to entry in the performance suspension market these days. I periodically run across yet another new brand. If you add in the firms that go only after automotive or ATV markets there are even more people making suspension parts.

[Michael Moore]

http://www.bsaotter.com/scorpion_sportsters_march_1963..html

has some photos of the Scorpion fabricated steel sheet frames that I'd not seen before (including one in scrambles trim) and a period article says the frame was made of 16g material. 2" x 5" deep at the head stock tapering out to 4" wide (probably the underseat/vertical box area).

Look around the rest of the site for interesting trials frame info.

[Grumph]

I got into conversation with a guy who I'd known for years about frames a few years back and that one came up. He knew all about it as he'd helped to build the prototype. He's since died but you'd be surprised how many Kiwis were in the UK in the early 60's involved with motocross and trials. One chap I knew had been the welder at the Rickman Bros factory for about 4 years. Apparently it was a job that was handed from Kiwi to kiwi...Another here still active worked for Cheney for a couple of years then moved around as and when the little independents could afford to pay wages - usually when an order came in, LOL. It was all hand to mouth stuff at the time which suited the Kiwis who usually didn't want to be tied down - and wanted time off to ride or do some Continental meetings.

[chrisc]

Does anyone have this book I could borrow? Pleeeeeassssseeee. I've read the first one and loved it.

John bradley
The Racing Motorcycle: A Technical Guide for Constructors: Vol 2

[Michael Moore]

Greg, it would be nice if people wouldn't take all their interesting information with them when they die. I'd have been pleased to hear the recollections he had about Scorpion and other cool stuff that happened in the days of yore, and also find out if he had some old photos to share.

[Grumph]

Greg, it would be nice if people wouldn't take all their interesting information with them when they die. I'd have been pleased to hear the recollections he had about Scorpion and other cool stuff that happened in the days of yore, and also find out if he had some old photos to share.

Yeah, there's been two or three guys like that who someone should have sat down with a tape recorder. And that's just local to me in the South Island.
Talking to the one or two I see occasionally, pics were something they never thought about at the time. Some of the guys who went over in the 70's and later had cameras and have pics - but the early guys in the main don't have them.
I knew two guys who went over in the late 50's and wound up working for F1 car teams. No pics either of them - it just wasn't something they thought about.
Even George Begg who went over to work for Mclaren to learn more for his own builds doesn't seem to have taken many pics...
If camera phones had been around, much of that history would have been better recorded.

[Grumph]

Does anyone have this book I could borrow? Pleeeeeassssseeee. I've read the first one and loved it.

John bradley
The Racing Motorcycle: A Technical Guide for Constructors: Vol 2

Depends what you can offer as security for it's return.....

I had to build a man a bike to get this copy.

As an aside, IMO Vol 2 is really all you need if you think you already know the theory...

[timg]

Depends what you can offer as security for it's return.....

I had to build a man a bike to get this copy.

As an aside, IMO Vol 2 is really all you need if you think you already know the theory...

I know Chris. Races buckets and RS125's so he's a good guy :rolleyes: And he's a scrawny wee runt so breaking his legs won't be hard if he screws up :laugh:

[Grumph]

I know Chris. Races buckets and RS125's so he's a good guy :rolleyes: And he's a scrawny wee runt so breaking his legs won't be hard if he screws up :laugh:

I know who he is - and the fact he races 125 and buckets says he's small, lol - From the Canterbury point of view he's the "other" Cain..

Will you stand guarantee ? I need a fence built.....

[timg]

I know who he is - and the fact he races 125 and buckets says he's small, lol - From the Canterbury point of view he's the "other" Cain..

Will you stand guarantee ? I need a fence built..... Nah, I'll break his legs to match his other broken bits :bleh:

[chrisc]

Yeah I'm pretty broken at the moment hence all the thinking about bike building :wacko:

I totally appreciate your hesitation to send me these priceless religious artifacts! I'll happily send you lots of money as a bond, which you send back when I get the book to you again. Timg has also offered free wristies at every race meeting you attend. Thanks Timg!

On another note, I had no idea Kymco of all manufacturers developed a Moto3 bike a while back. Cool!


https://www.youtube.com/watch?v=-PqF2RTs9ts


https://www.youtube.com/watch?v=Eyg6u727FI0


https://www.youtube.com/watch?v=6WWihaPf8Wg

[monkeyfumi]

It was more of a badge engineering exercise.
The engine was done by Oral engineering, and slotted into a (now redundant) Aprilia RSA125 chassis

[F5 Dave]

Hey sorry to hear you are bust. Spent some time there myself (hence the 50 being sold to some prat up norf) and its a bit tedious. Heal like a starfish.

[chrisc]

It was more of a badge engineering exercise.
The engine was done by Oral engineering, and slotted into a (now redundant) Aprilia RSA125 chassis

Watch the videos. First gen was RSA chassis, then they made one themselves. But yeah, Oral engineering was driving it. Hopefully they integrate into Kymco somehow so we actually see the technology spread, which is good for all of us.


Hey sorry to hear you are bust. Spent some time there myself (hence the 50 being sold to some prat up norf) and its a bit tedious. Heal like a starfish.

Yeah it sucks, I've missed 5 weekends of racing in a row but I've taken a shit load out of it. Spent a lot of time watching people ride the tracks and found a lot of places I can go faster, so I'll back myself to pick up the pace when I next get on the bike. Always a silver lining... unless it's a 2 stroke which then it's usually a red Elf 909 lining.

I purchased a potential donor bike for a RSX50 project I'm hoping to get off the ground. Might be twisting your lads ears about chassis soon.

https://c1.staticflickr.com/4/3773/32548258524_2f2d65dd68_c.jpg (https://flic.kr/p/RAbki7)IMG_4485 (https://flic.kr/p/RAbki7) by Chris Cain (https://www.flickr.com/photos/sonscc/), on Flickr

Anyway, enough of my distraction!

[F5 Dave]

Too much rain today. I should have been out riding my 300 GasGas today. Its awesome.

[Michael Moore]

http://www.bsaotter.com/scorpion_sportsters_march_1963..html

Some additional photos and measurements/detail information on the Scorpion frame has been added by Charlie. It is at the bottom of the page.

cheers,
Michael

[husaberg]

http://www.bsaotter.com/scorpion_sportsters_march_1963..html

Some additional photos and measurements/detail information on the Scorpion frame has been added by Charlie. It is at the bottom of the page.

cheers,
Michael

In the villiers book there is a picture of the road racer version it looked very neat.
Oh and here it is on the site. I think any were made though.
http://www.bsaotter.com/media/images/user-images/14844/Image18-10-2015at11.45-edit.jpg
The MX version up the top looks like bits of Greeves DMW Butler and Dot all thrown together.
My father has a Butler. prior to making complete bikes . He used to make a lot of fibreglass for different manufactuers.

[Grumph]

If I'd seen that roadracer I may well have copied it for Peter Pastars Starmaker....I'd looked at the Cotton frame for the motor and I'd had an AJS Stormer through the workshop which had been converted to a roadracer - which I didn't much like.
So I did a "freehand" version of the AJS frame layout juggled around to suit a roadrace application.
But I'd been doing Aermacchi replica spine frames for years so if I'd seen that one it would have been attractive...

[Michael Moore]

Greg, I like the looks of that bike.

The Scorpion RR frame looks like a Triumph T140 without the lower cradle tubes. Bending a big tube like that is going to be hard for a DIY person, welding a top and a vertical tube together (like the drainpipe Dunstall twin) would be easier.

[Grumph]

Greg, I like the looks of that bike.

The Scorpion RR frame looks like a Triumph T140 without the lower cradle tubes. Bending a big tube like that is going to be hard for a DIY person, welding a top and a vertical tube together (like the drainpipe Dunstall twin) would be easier.

Thanks - it finished up very pretty and looking very period which was the aim. It's badged as an AJS and more than one person has said to Peter "didn't know that the roadrace version of the Stormer was ever sold"....LOL Goes quite well too.

Bending big tube isn't a problem for me. There's an exhaust manufacturer in ChCh with a mandrel bender - and dies for tube up to 6 inches dia...
I know of a guy who was making Manx replica frames here who was getting them to bend up all the bits required. He'd just ring them up and order up the required number of kits. One benefit of living so far from the rest of the world Michael, is that when people buy in something like a mandrel bender they get the most versatile/largest possible as you never know what you're going to have to do....

[guyhockley]

Seem to remember a Scandinavian member of MC-Chassis Design saying he had hydroformed a 90 degree bent sauna flue of 3 inch diameter in 16 guage...

[Michael Moore]

Guy, I don't remember that (but I can't remember every comment over 20 years of the list), but hydroforming would let you have a tapered tube if you wanted it, or even various localized increases/decreases in diameter.

[guyhockley]

The AJS Stormer frames looked like the spine was fabricated from 2 pressings or tapered from a thicker tube. I was looking at a Can-Am 175 racer a few years back and the frame design looked very similar.
Prefer the "Grumph AJS", nice piece of kit.

[guyhockley]

Guy, I don't remember that (but I can't remember every comment over 20 years of the list), but hydroforming would let you have a tapered tube if you wanted it, or even various localized increases/decreases in diameter.

Found it, but I got the details wrong...

"Date: Thu, 07 Jan 1999 07:33:06 +0200
From: Tomas Tallkvist
Subject: MC-Chassis Hydroforming

Hello !

The system I am using is based on an old Highpressure cleaner, connected to
the outlet,
it feautures a pressure reducing valve so you can adjust the pressure from
5-150 bar.

It works in the same manner as an hydraulic hand pump, but you are allowed
some "minor"
leaks without trouble !

When waterforming megaphones and 2 smoke exhaust systems, no more than 30
bar is used.

The only time I used over 40 Bar was when I made an nice 90 degree bent
chimney connection
tube of 110mm dia of 1,5mm sheet to the Sauna Oven !

The only thing with this technique is that it is hard to come up with
calculations how to
cut the sheet so the final form is the one that you looked for, a better way
is to just make
10-15 megphones and get some experience...

Simple, but it works !

Tomas"

[Michael Moore]

yeah, you've got to do a fair number of practice runs to get a handle on how much the end result of a turn varies from the angle on the pattern. I watched one video in which the exhaust tightened up and then unfolded some, that's not very helpful.

If you are going to do a fuel-containing spine/monocoque hydroforming would let you know for very sure if you had any leaks.

[Grumph]

The AJS Stormer frames looked like the spine was fabricated from 2 pressings or tapered from a thicker tube. I was looking at a Can-Am 175 racer a few years back and the frame design looked very similar.
Prefer the "Grumph AJS", nice piece of kit.

Thanks. The Stormer I had here for a rebuild had been converted to a roadracer early in it's life and apparently had Irish roads history. It had been bought by an Auusie on his big OE and taken back to melbourne. I think he'd worked for a precision grinding outfit as their name was on the side. It had a yamaha YZ rod and pin, a Wiseco piston made for an RM250 Suzuki - and finger transfers cut in the bore like a TD1C. It had ben bought by a Kiwi from his estate and had sat for years in NZ. I finished off the job of fitting one of the rare 6 speed Villiers boxes to it - different engine mounts needed.
It was frankly ugly with the std tank and a Dunstall/Chuck style of seat with an apron grafted on to span the gap seat to tank.
Once running it went very well indeed. It's changed hands and I've lost track of it since.

And yes, the top short spine was two pressings welded together to form a tapered box. I simply used a top tube of 2 in OD X 2mm wall MS. Good enough.

I seem to remember that Jeff Smith was involved with the early Can-Ams and liked the AJS frame a lot - enough to do a close copy anyway.

[Michael Moore]

Tony's TZ250/350 frames used a 16g x 2" spine. He told me that if he were (and he's not) to make another one for a modern vintage TZ running on today's tires he'd bump that to 2.25" (which would be about a 30% increase in stiffness or about 8-10% over the 2" x .08" tube)).

I've wondered if the AJS spine was two U-shaped pressings or a U shape added to a full tube, now I know.

[Grumph]

Tony's TZ250/350 frames used a 16g x 2" spine. He told me that if he were (and he's not) to make another one for a modern vintage TZ running on today's tires he'd bump that to 2.25" (which would be about a 30% increase in stiffness or about 8-10% over the 2" x .08" tube)).

I've wondered if the AJS spine was two U-shaped pressings or a U shape added to a full tube, now I know.

Just to be sure, I pulled out the Starmaker manual (hey, things seem to stick to my shelves...) and yes, a full length spine, steering head to rear bulkhead, tapered and in two pieces, seam welded.
Mine was a lot shorter as the pic shows. The clever bit I copied from the Stormer was the half round piece across the frame enclosing the front of the swingarm. If, like all Villiers, the engine mounts are narrow, this gives a very stiff point to attatch to.

[husaberg]

Some fella that worked at NVT wrote this

Dr. Bauer was the head of the Wolverhampton operation, where all the design and development took place for the AMC group. A very clever and erudite gentleman, but I thought out of his depth in an industrial organisation which was supposed to make products for profit. His specialty was combustion chemistry, I think.
When I was there, we were down to just Norton and AJS on the market, along with the Villiers range of industrial engines. We did make one "oddball" Matchless, a trials version of the Starmaker motocross machine for the ISDT in 1968.
Bob Trigg headed up the design team on both the Commando and the AJS motocross/trials bikes, sold in the US as the "Stormer". I believe the design was sold to a division of Bombardier (KTM?).
There was a strong family resemblance between the two frames, the only differences on the AJS being the way the top tube joined the headstock and no Isolastics. We had real problems with fatigue failures on the top tube.

Pretty sure Renyolds made the prototype and likely the frames as well as Norton didn't have welding facilities.
Latter Commando frames were made in Spain i think. Reynolds alledgedly made more money out of straightening themfor Norton after delevery than they ever did making ones for Norton, According to something Ken wrote

[guyhockley]

Tony's TZ250/350 frames used a 16g x 2" spine. He told me that if he were (and he's not) to make another one for a modern vintage TZ running on today's tires he'd bump that to 2.25" (which would be about a 30% increase in stiffness or about 8-10% over the 2" x .08" tube)).

I've wondered if the AJS spine was two U-shaped pressings or a U shape added to a full tube, now I know.

Tony told me that when I asked if I could make a copy - still haven't got around to it...
Nigel Leaper may have agreed as there was a blog detailing restoration of Vince (Fondseca) Caundle's ex works Waddon that has a 63mm spine and he measured several others at 55mm (2.5" and 2.25"?).
Also heard of a british racer (Simon something) who wrecked his Waddon, built his own replacement frame, then went on to make a "few" more, so who knows what's out there?
https://web.archive.org/web/20110524082819/http://www.waddon.me/about/

[richban]

Hi Guys.

So after getting all excited about building a mono. I have switched back to a tube steel version. Its something I can do with the tools I have so I am going to get one with it. I'm not using chomo. Its mild steel for this first attempt. I have the steel now. 5 dollars a metre cheap cheap. Its 25 x 1.2. Basic design below. For this first attempt I will use the RS50 swing arm.

329508


I started to machine a bit of steel for the head stock and cocked it up rather quickly. Turns out steel is actually not its more butter you just pulled out of the fridge. It grabbed and fung its self out of the lathe. Its bent.

329509

Now I am left wondering about my choice of material. As the head stock is quite important I am now wondering if there is a grade of steelbutter that is better the stuff I have. Sort of spreadable butter versus Old school hard as a rock straight out of the fridge butter. Or even better frozen butter. That shit is hard.

I did a little research around welding mild steel to Chromoly. Seams its ok as long as you heat the work before welding.

[Ultralightweght]

I'd use 1040 or 1030 grade- or phone milson metals and get some hollow bar - save heaps of time machining-the next thing to check is the tool geometry - it changes if your turning something soft like alum or plastic vs high tensile or brass/bronze etc-I'm assuming also the tool is not under centre as that will hook something out of the lathe- did you have tailstock in?

[richban]

I'd use 1040 or 1030 grade- or phone milson metals and get some hollow bar - save heaps of time machining-the next thing to check is the tool geometry - it changes if your turning something soft like alum or plastic vs high tensile or brass/bronze etc-I'm assuming also the tool is not under centre as that will hook something out of the lathe- did you have tailstock in?

Much thanks. Will give them a bell next week. No tail stock rpm way high. Disaster waiting to happen really. Learning some lessons so thats a plus.

[Grumph]

Much thanks. Will give them a bell next week. No tail stock rpm way high. Disaster waiting to happen really. Learning some lessons so thats a plus.

You don't need a fully machined one piece headstock. A piece of largish OD MS tube say 2mm wall with the ends squared will do. Then you make up bearing carrier inserts in either steel or alloy and press them in once the welding's done...
I've "pressed" them in with a m'f big G clamp no probs.
Ducati and others did it like this for ages with no problems

[richban]

You don't need a fully machined one piece headstock. A piece of largish OD MS tube say 2mm wall with the ends squared will do. Then you make up bearing carrier inserts in either steel or alloy and press them in once the welding's done...
I've "pressed" them in with a m'f big G clamp no probs.
Ducati and others did it like this for ages with no problems

That was the plan. Still is. The bit I had was 60.3 x 3.9mm. The plan was tidy up the inside 30mm in the tin the outer to make 2mm wall. Good to know thats how its ben done before.

I have one off these profile gauges on the way.

329529

[Grumph]

Never used or needed one of them. A good eye and steady hand with a disc grinder will do most of it - and a good selection of round and half round files too.

If you're using 1.2mm wall tube, make yourself a split wood block to hold the tube in the vice.
Piece of softwood - pine is good - bored 25mm to suit your tube, then cut down the length of the hole.
Use on each side of the tube when clamping it up to cut or grind.
Made out of a short piece of 50 X 50 dressed pine would work.

[richban]

Never used or needed one of them. A good eye and steady hand with a disc grinder will do most of it - and a good selection of round and half round files too.

If you're using 1.2mm wall tube, make yourself a split wood block to hold the tube in the vice.
Piece of softwood - pine is good - bored 25mm to suit your tube, then cut down the length of the hole.
Use on each side of the tube when clamping it up to cut or grind.
Made out of a short piece of 50 X 50 dressed pine would work.

Top tip. Will do.

[Michael Moore]

for thin wall tube snips are fast for roughing cuts.

http://tonyfoale.com/progs/tubemiter.exe

should help you make patterns for the tubes. After some practice you'll get better at eyeballing them.

[guyhockley]

https://www.youtube.com/watch?app=desktop&persist_app=1&noapp=1&v=cdhuYjbZJt4

[husaberg]

https://www.youtube.com/watch?app=desktop&persist_app=1&noapp=1&v=cdhuYjbZJt4

Seems to have a PDS shock and you would expect a Progessive spring.
http://racetech.com/articles/ktm.htm

[husaberg]

Never used or needed one of them. A good eye and steady hand with a disc grinder will do most of it - and a good selection of round and half round files too.

If you're using 1.2mm wall tube, make yourself a split wood block to hold the tube in the vice.
Piece of softwood - pine is good - bored 25mm to suit your tube, then cut down the length of the hole.
Use on each side of the tube when clamping it up to cut or grind.
Made out of a short piece of 50 X 50 dressed pine would work.

Not sure if this was posted on he thread or not i watched it the other day.

https://www.youtube.com/watch?v=mHBanmfn_CA

[jasonu]

Hi Guys.


I did a little research around welding mild steel to Chromoly. Seams its ok as long as you heat the work before welding.

Steel to crmo no problem, just do it. Use ER70S filler wire. Don't over think it, just do it.

[jasonu]

Not sure if this was posted on he thread or not i watched it the other day.

https://www.youtube.com/watch?v=mHBanmfn_CA

I made a shit ton of these crmo aircraft motor mounts. We had ali tube cut patters we slide over the raw stock, draw around the edge, rough cut it with a vertical bandsaw then finish fit it using a 6" bench grinder on a solid floor mount with a grinding wheel dressed to a 1/2 round profile. Easy pesy. The way the guy in Husas vid is marking out his cuts is the way I did it if there was a new cut to make before I made a pattern.

BTW the big round donuts and the machined blocks are both mild steel and welded together fine, never had to or even thought of preheating them.

[Ocean1]

I made a shit ton of these crmo aircraft motor mounts. We had ali tube cut patters we slide over the raw stock, draw around the edge, rough cut it with a vertical bandsaw then finish fit it using a 6" bench grinder on a solid floor mount with a grinding wheel dressed to a 1/2 round profile. Easy pesy. The way the guy in Husas vid is marking out his cuts is the way I did it if there was a new cut to make before I made a pattern.

BTW the big round donuts and the machined blocks are both mild steel and welded together fine, never had to or even thought of preheating them.

Never learned the box and pour method eh?

[husaberg]

I made a shit ton of these crmo aircraft motor mounts. We had ali tube cut patters we slide over the raw stock, draw around the edge, rough cut it with a vertical bandsaw then finish fit it using a 6" bench grinder on a solid floor mount with a grinding wheel dressed to a 1/2 round profile. Easy pesy. The way the guy in Husas vid is marking out his cuts is the way I did it if there was a new cut to make before I made a pattern.

BTW the big round donuts and the machined blocks are both mild steel and welded together fine, never had to or even thought of preheating them.

there was one with the jig pattern as well on the same feed

https://www.youtube.com/watch?v=9yowlcqJjlo

this was cool as well


https://www.youtube.com/watch?v=TWQAYfGxsPE

[mr bucketracer]

Not sure if this was posted on he thread or not i watched it the other day.

https://www.youtube.com/watch?v=mHBanmfn_CAthis is pain full lol , get the right size milling cutter for tube , close chuck of lathe with milling cutter in it (-; , clamp tube in tool holder , set on center....set to what angle you need , i will let you guys work out the rest lol

[jasonu]

this is pain full lol , get the right size milling cutter for tube , close chuck of lath with milling cutter in it (-; , clamp tube in tool holder , set on center....set to what angle you need , i will let you guys work out the rest lol

Assuming one has a lath....




or a lathe:cool:

[Grumph]

Assuming one has a lath....




or a lathe:cool:

One has a lathe - but one does not have the dosh for a range of milling cutters...

I do do swingarm to crosstube profiling in a jig with a holesaw though. It's the only time I do - and that's simply to accurately get the legs the same length...

[Michael Moore]

Guy, thanks for the video link. I wonder if he looked at Hoyt McKagen's bikes/patent before he built his KTM?

http://www.eurospares.com/mckagen/hoyt001a5.jpg

http://www.eurospares.com/graphics/chassis/McKagenUS4627632A.pdf

It is nice to see someone do something different and actually get it to the track.

[guyhockley]

Guy, thanks for the video link. I wonder if he looked at Hoyt McKagen's bikes/patent before he built his KTM?

http://www.eurospares.com/mckagen/hoyt001a5.jpg

http://www.eurospares.com/graphics/chassis/McKagenUS4627632A.pdf

It is nice to see someone do something different and actually get it to the track.

Hoyt's bikes were what it reminded me of, I think Hoyt said he had a full foot of travel on his front end. Any idea what happened to his stuff after he died?
Harry Stitt has a trials version as well. What he doesn't seem to have, considering he looks about 14, is a webpage!

[guyhockley]

One has a lathe - but one does not have the dosh for a range of milling cutters...

I do do swingarm to crosstube profiling in a jig with a holesaw though. It's the only time I do - and that's simply to accurately get the legs the same length...

One of the british factories, I can't remember which one, possibly Velocette?, used to make cutters out of tube offcuts. Guess it wasn't one of those that hearth brazed straight end tubes into bloody, great chunks of cast-iron.

[Michael Moore]

You can also make different sized rollers for a belt sander so that roller OD + 2x belt thickness gives you the diameter in the tube.

I've used a boring head to single point the cut but it is slow.

I've found it helpful to offset the cut towards the end of the tube so the "points" don't taper to a feather edge, as I've had that edge get grabbed and folded into the cut by end mills. The thin bit of tube has to be clipped off anyway as it just burns up if you don't, so set the cut so that it stops just short of getting into the wall at the outside end.

[guyhockley]

http://jebustownmotorcycles.blogspot.co.uk/2014/01/harrys-frames-hes-getting-better-all.html?m=1

Looks like a bucket engine!

[Grumph]

Looks like a bucket engine!

Looks like a Suzuki TC120. The two cables going into the rear of the box suggest it's the dual range gearbox.
He does nice work. You can always pick work done with an inline fluxer too.
Wish filling them wasn't so expensive here....

[guyhockley]

http://jebustownmotorcycles.blogspot.co.uk/2015/06/triumph-frame-brace.html?m=1

http://jebustownmotorcycles.blogspot.co.uk/2013/01/harrys-frames.html?m=1

Couple more posts on that blog showing more of his stuff.

[guyhockley]

No comment...

[Grumph]

[QUOTE=guyhockley;1131No comment...[/QUOTE]

"Blade Runner" comes to mind.

[guyhockley]

One has a lathe - but one does not have the dosh for a range of milling cutters...

I do do swingarm to crosstube profiling in a jig with a holesaw though. It's the only time I do - and that's simply to accurately get the legs the same length...

From: http://enigma1050.co.uk/index.php/technical/the-frame/frame-build-part-two/

"Dave Pearce of Tigcraft reckons that the Stakesys Hole Saw Tube Notcher is the best two hundred quid he’s ever spent on a piece of tooling. When you join two pieces of tube, they have to meet precisely and this is where the notcher comes in.
“You can use a file and a hacksaw to achieve the same result,” says Dave, “But it takes forever and you end throwing a lot of tube away when you get it wrong.”
To use the notcher, you select a hole saw of the same diameter as the tube you want to prepare, set the angle of the tool to the work to the same as the angle of the tubes to be joined then cut the notch. The tool is powered by an electric drill. The shaft which holds the cutter rotates on needle roller bearings in a substantial aluminium alloy housing which ensures both accuracy and longevity."

329689

They have several models.

https://www.stakesys.co.uk/tube-notchers

[Grumph]

The problem with anything using holesaws is how the saw blade is held on the arbour. I've never seen one which used the two dog drive which didn't wobble. Any wobble and the cut is 1/ bigger and 2/off center.

[Michael Moore]

Another problem with the machine tool solutions is you need to know the angle you want to cut to and be able to set it accurately.

For a production series you'll have drawings and the proper tools to use. For a one-off that you are building around an engine/steering head placed on the frame fixture you might be able to easily do a number of 90 intersections for cross tubes with the hole saw/milling cutter, but the other tube ends, especially on tubes that have been bent to be "pretty close" may be faster to fit with saw/snips/files/grinder.

Dave is right that you can end up with more scrap by hand while you are getting the hang of things. I like to start with the longer tubes so if they are stuffed I can trim them back and have another try with them as a shorter tube.

A lot of it will depend on your hand/eye coordination and the ability to visualize how the profile will look.

If you have a very long/shallow cut, say something where the tube axes are only 20 degrees apart, you can easily run out of length on the cutter/saw arbor before you get the cut finished.

A few discreet taps with a small hammer don't seem out of order when that helps save a tube from being scrapped.

[Ocean1]

The problem with anything using holesaws is how the saw blade is held on the arbour. I've never seen one which used the two dog drive which didn't wobble. Any wobble and the cut is 1/ bigger and 2/off center.

You can cut the top out of them and weld them to a solid arbor, which you can then hold absolutely rigid in a big fuckoff collet chuck in t'mill. And the fuckers still sometimes spit teeth, fold up and turn your day to shit.

So I've acquired a small collection of rotabroaches, which work splendidly. Especially as I happen to have a 5" dual angle adjustable vice. I also have split half round jaws for 3/4", 1' and 1 1/4" tube. Anything else just gets a bit of solid up inside.

But then, most of my tube work is in 316...

The very best tube notcher I've seen was made out of a spindle moulder, with a belt roller taking the place of the cutter and an infinitely adjustable toolpost/tube clamp. Perfect.

[Ocean1]

For a production series you'll have drawings and the proper tools to use.

I have a very short attention span, there's just no way I'm hand fitting tube for more than two of the same jobs, it's going out to a laser cutting service.

Which, admittedly presupposes you've modeled the job in some appropriate system...

[Grumph]

You can cut the top out of them and weld them to a solid arbor, which you can then hold absolutely rigid in a big fuckoff collet chuck in t'mill. And the fuckers still sometimes spit teeth, fold up and turn your day to shit.

Agree - and I'm around 80km from the nearest stockist with no courier service. Disc grinder still looks good to me.

[husaberg]

Agree - and I'm around 80km from the nearest stockist with no courier service. .

Just get Mainfreight to pop one on a pallet and send it to you.:msn-wink:

[Grumph]

Just get Mainfreight to pop one on a pallet and send it to you.:msn-wink:

That's getting old...and i'm still waiting to hear if the Hayabusa engine I sent north has arrived in one piece.

I'm not optimistic...

[husaberg]

That's getting old...and i'm still waiting to hear if the Hayabusa engine I sent north has arrived in one piece.

I'm not optimistic...

Almost a week or over?
The hayabusa must be over 2 liters now.:laugh:

New imperial cantalever with a linkage and underslung braced swingarm unit construction 1930's
329734329735329736329737

[Grumph]

You forced me to hunt this out and post it.
The Bentley and Draper rear suspension set the cause of rear suspension back considerably.

[F5 Dave]

Ahh you'll never get it to handle right if there's a hinge holding the rear end on. Sheesh!

[husaberg]

Ahh you'll never get it to handle right if there's a hinge holding the rear end on. Sheesh!

One should always drive your Bentley Gentley

[guyhockley]

Over on the Old Multi thread, Husaberg posted some scans about Granby Yam 125s.

https://www.kiwibiker.co.nz/forums/showthread.php/151865-Old-multi-cylinder-bikes-of-the-50s-to-later-on-Japanese-British-Euro-etc?p=1131021058#post1131021058

Same Basic Spondon frame design, but presumably stretched a bit, and modded to detachable downtubes:

http://www.racingoutoftime.co.uk/?tag=silk-scott

[guyhockley]

Back to monoshock BSAs.

[husaberg]

Back to monoshock BSAs.

They made others later with DT175 engines (not a joke either)
BSA tracker /NTV rambler
http://automotoclassicsale.com/sites/default/files/ebay_111843131784_2.jpg
http://3.bp.blogspot.com/-xeHGNKtEUE4/T39ApQs25pI/AAAAAAAAAhA/TfB0kfupQ9Y/s1600/tracker2.jpg
http://i1060.photobucket.com/albums/t447/HowD1/CIMG0036.jpg



Or the Gt50 boxer/Beaver/Brigend
With a 50cc Moto Morini engine
http://2.bp.blogspot.com/-7RCvGPpKuyo/UQgVOYIxgPI/AAAAAAAAEoY/mvaL6_Qe3to/s1600/bsagt50.jpg
http://i4.photobucket.com/albums/y132/ayrton27/pb050288.jpg

But seriously Eric Cheney made a 2 shocked cantalever from in about 1971/73 for the new XL250 engine bike he made
It was a beautiful looking bike, like all of his other bikes.
329769
not so much in this picture though

[guyhockley]

Yeah, I meant "proper" BSAs :msn-wink:
Later than the one's you posted, there was BSA Regal in Southampton, who upset the purists by launching the SR500 engined Gold Star. I think it was in their window that they had a prototype (maybe called Barracuda?) that had a very Tony Foale/Waddon type frame, similar to the one at the start of this thread. Got any pictures of that? I would google it but I'm on phone data at the moment.
There was quite a lot of Yamaha content in later "british" bikes.
I used to live in Hampshire near Eric Cheney, never met him but knew people that remembered him from back when he worked for Les Archer. He had a reputation for being a bit "difficult". My boss knew him and the Archers and we also had dealings with Ken Heanes so I've seen a few Cheneys. Confusingly, there's an American flat-track frame builder with the same name.
There's a bloke who is or was restoring one of Phil Read's Cheney Yamaha road racers and he seemed to feel that Simon (?) Cheney wasn't up to his father's standard, sadly.

[Grumph]

One of the guys local to me who worked in the UK motocross scene tells a story of when he worked for Eric.
They'd been working to get a prototype finished and Eric got called away to London for a meeting.
The lads in the workshop got it finished as promised and then looked at it and thought "we've got the time, lets get some bits polished "
My friend took the alloy tank up the road to " A bunch of Pakis who did all our polishing" (his words)

When he went back to get the tank the following day, it was spread and distorted badly....over heated in polishing.

Apparently he worked most of the night to do another tank before Eric got back.
Eric's comments when he saw the finished bike were to the effect that it didn't look bad, but he didn't like the tank and they'd better have another go at it...

[husaberg]

Yeah, I meant "proper" BSAs :msn-wink:
Later than the one's you posted, there was BSA Regal in Southampton, who upset the purists by launching the SR500 engined Gold Star. I think it was in their window that they had a prototype (maybe called Barracuda?) that had a very Tony Foale/Waddon type frame, similar to the one at the start of this thread. Got any pictures of that? I would google it but I'm on phone data at the moment.
There was quite a lot of Yamaha content in later "british" bikes.
I used to live in Hampshire near Eric Cheney, never met him but knew people that remembered him from back when he worked for Les Archer. He had a reputation for being a bit "difficult". My boss knew him and the Archers and we also had dealings with Ken Heanes so I've seen a few Cheneys. Confusingly, there's an American flat-track frame builder with the same name.
There's a bloke who is or was restoring one of Phil Read's Cheney Yamaha road racers and he seemed to feel that Simon (?) Cheney wasn't up to his father's standard, sadly.

Those phil read bikes always looked great with the Dunstall forks and disks and the rear disc as well,
I never figured out what the rear was, some sort or airhearst Kart?
I wonder if Ferry Brouwer is still alive.
I read a story about Read a while back it seems his trick was to visit all the other pits and talk to the riders and raise Faux concerns about parts of the track.
It was said to work on most of the racers other than Hailwood who used to just tell him to "piss off"

[Frits Overmars]

Those phil read bikes always looked great with the Dunstall forks and disks and the rear disc as well,
I wonder if Ferry Brouwer is still alive.My mate Ferry is very much alive and enjoying it.
329800 329799 329801

[husaberg]

My mate Ferry is very much alive and enjoying it.
329800 329799 329801

Can you ask him what Phil Reads rear disc set up was on the cheney.
I do remember the yam 4 reps i never put two and two together

[Frits Overmars]

Can you ask him what Phil Reads rear disc set up was on the cheney.I seem to remember that the rear caliper came from Lockheed.


I do remember the yam 4 reps i never put two and two togetherCome again?

[husaberg]

I seem to remember that the rear caliper came from Lockheed. Come again?

The RA31.....

[Frits Overmars]

The RA31.....The RA31 125 cc-four was the first bike Ferry worked on for the Yamaha works team. It has been his favorite bike ever since.

[WilDun]

Frits, - Is he related to the young Dutch guy called Brouwer (correct spelling?) presently riding in BSB?

I see also that Rickman? are testing a Metisse frame for the Triumph Triple (Moto 2). - I guess Triumph will now take over the name of "villain" from Honda!

[Frits Overmars]

Frits, - Is he related to the young Dutch guy called Brouwer (correct spelling?) presently riding in BSB?I haven't got a clue. Not about BSB racing (it's all four-strokes, I've been told) and even less about who that young guy could be and if he might be related to Ferry.
Ferry and Margriet have one daughter; no sons.


I see also that Rickman? are testing a Metisse frame for the Triumph Triple (Moto 2). - I guess Triumph will now take over the name of "villain" from Honda!Would it surprise you to hear that I'm not that interested in Moto2 either? Maybe if they would turn an Aprilia RSA250 with 2017-tires loose on the Honda 600 cc four-stroke-class; that would be a giggle. And I don't see Triumph as the villain. You can't blame them for taking the opportunity to step in when the real villain steps out.

[WilDun]

I haven't got a clue. Not about BSB racing (it's all four-strokes, I've been told) and even less about who that young guy could be and if he might be related to Ferry.
Ferry and Margriet have one daughter; no sons.

Ok. so I guess I should rule out that connection!

The new 'Metisse" frame is really what interests me here, but there doesn't seem to be a lot of details available on that as yet.


Would it surprise you to hear that I'm not that interested in Moto2 either? Maybe if they would turn an Aprilia RSA250 with 2017-tires loose on the Honda 600 cc four-stroke-class; that would be a giggle. And I don't see Triumph as the villain. ...........

No Frits it wouldn't :)
When I first (almost) understood how a steam engine worked (when I was in primary school) I thought that if anything was not powered by steam then it wouldn't be any good, I then discovered the four stroke in the form of the Manx Norton, AJS, Gold Star etc. leading on to road racing, also motocross and speedway, a fantastic new world!
I discovered two strokes in a different way, (via the Mills .75cc diesel model aircraft engine) and thought, what if I scaled that up and put it in my bicycle? but found that BSA had already done that in the Bantam which led me on to the Bultaco and MZ. Two strokes! - definitely the engines of the future I thought.

What next? gas turbine/electric, then maybe a dramatic discovery which will consign them all to the rubbish bin? - doesn't matter, to me they all have their attractions!

But ....... Maybe I should just stick to hot air engines for the moment :laugh:

[guyhockley]

I wonder why?....

[WilDun]

Plentiful supply? cheaper than alcohol? :rolleyes:

Anyway, what is that picture - definitely somebody's idea from a few years back - or is it?

Afterthought:- maybe not such a fantasy nightmare after all, - sort of grows on you when you stare at it for a while!

[Grumph]

I wonder why?....

Because they had the frame ?

The only useful thing I get out of that is what looks to be a combined footrest/brake pedal assembly.
If I'm ever that short of space, I may use it.

[guyhockley]

Think it's mostly an Aprilia RS50, or was before a mad Frenchman got hold of it...
I presume the front master cylinder is in the handlebar.

[Grumph]

Think it's mostly an Aprilia RS50, or was before a mad Frenchman got hold of it...
I presume the front master cylinder is in the handlebar.

Cable to M/c under the tank. Brake hose comes out above the radiator.
Lot of early front disc setups were like that as there were no handlebar M/c's.
Then of course BMW carried it on for a while.

[F5 Dave]

And separate buttons for indicators. But they started the war.

[guyhockley]

Cable to M/c under the tank. Brake hose comes out above the radiator.
Lot of early front disc setups were like that as there were no handlebar M/c's.
Then of course BMW carried it on for a while.
Only saw the picture on my phone so I couldn't see much detail, I was kind of extrapolating from the reversed levers.
Years ago, we did a rod to car master cylinder on the top yoke for a motocross outfit (or it might have been grass-track sidecar...)

Found where the original picture probably came from:

http://artus.forumactif.com/t3466-aprilia-50-rs-revu

[guyhockley]

After making their glued'n'screwed, strips of ali frames for a while, CCM have remembered where they tidied away the tube bender...

[Frits Overmars]

After making their glued'n'screwed, strips of ali frames for a while, CCM have remembered where they tidied away the tube bender...Must be a work of art because no self-respecting technician would even dream of such improper use of steel tubing.

[ken seeber]

Must be a work of art because no self-respecting technician would even dream of such improper use of steel tubing.

Agreed, "steam punk" gone wrong.

[Grumph]

Agreed, "steam punk" gone wrong.

I know a couple of Steam Punk nutters who could produce something much better than that.

It doesn't appear to be getting many smiles from the crowd....

[WilDun]

Must be a work of art because no self-respecting technician would even dream of such improper use of steel tubing.

Nothing which looks "proper" will ever attract the hordes with their dollars, Harley honed that philosophy down to a fine art! .......... well, maybe John Britten had the ability to make "improper" looking stuff but managed to combine it with reason! - however, he didn't wait to see it through.

[philou]

Hello,

I am search information on the bending of extrud aluminum frame spar

[Grumph]

Hello,

I am search information on the bending of extrud aluminum frame spar

Putting it very basically - a little at a time, under a press.
If you can locate a copy of Bradley's book "The racing Motorcycle" Volume 2, there's a good description of how to do it in there.

[philou]

3 years I seek it :weep:

[F5 Dave]

I find a job goes much quicker if you don't try to do it properly.

[Ocean1]

Hello,

I am search information on the bending of extrud aluminum frame spar

Assuming you've got a suitable alloy, there's still quite narrow limits as to how far you can do that, mostly based on thinning out the outer bend radius wall thickness.

I can't help as far as Mr Bradley is concerned, but I'd like to know his technique.

What works for me on similar projects is: making inner and outer form tools to control expansion distortion, (bulging) and packing the extrusion with fine, dry sand, (with welded caps) helps control collapse of the walls.

I've used both a workshop frame press and a hydraulic pipe bender. Nice and slow and releasing the pressure occasionally has, for me helped reduce the liklihood of cracks. That, and keeping the whole assembly, (including form tools) warm.

It's almost certain that even if you don't stuff up the first attempt you'll learn how to do it with better results, so I'd suggest getting your hands on enough material to do a few. And make that your first operation, so when you bin it you haven't thrown away too much time...

[chrisc]

Go to 1.46 mark of this video for a glimpse of how Oral Engineering/Kymco did it for their Moto3 frame.


https://www.youtube.com/watch?v=-PqF2RTs9ts

[F5 Dave]

Engine looks overly complex and heavy for a small racebike.

[chrisc]

Engine looks overly complex and heavy for a small racebike.
I know right Dave, for one, they have these weirdly complicated valve things and it fires only half as often as it could. Weird. Must be a Chinese thing?

[Pumba]

Engine looks overly complex and heavy for a small racebike.

It's ok Dave. It will never catch on.


Sent from my iPhone using Tapatalk

[Flettner]

I'm late to this thread so possibly already talked about?
A mandrel tube bender is what you want. It can be made to bend all sorts of shaped tubes. It uses an outer and an inner shape, also a 'slug' in the middle held with a long rod from an anchor point down the straight unbent bit. Where the bend takes place, the tube is supported all around. Alloy tube is best softened (T 0) it will work harden a little at the point of bend, this helps it hold shape as it's drawn off the mandrel. After finishing and welding the frame it will need to be heat treated to T 6 again. Assuming you are using 6061.

[Grumph]

The problem with that Neil is that what frame sections can be obtained (in Europe) are odd shape and have internal divisions making mandrel bending difficult. Not impossible, granted. Plain rectangular tube is, by contrast, easy, as well as in plentiful supply.
The dedicated frame sections are also usually in a 7000 series air/time hardening alloy which means no heat treatment post weld.

I haven't yet seen the vid ChrisC posted, next time I'm on broadband I'll have a look. Bradley detailed the bending of frame spars in the book which was done in multiple bends under a press, going to around .020in deformation each press. Form tools were used too.

I'm actually suffering withdrawal symptoms, the book is on loan.....

[husaberg]

I haven't yet seen the vid ChrisC posted, next time I'm on broadband I'll have a look. Bradley detailed the bending of frame spars in the book which was done in multiple bends under a press, going to around .020in deformation each press. Form tools were used too.

I'm actually suffering withdrawal symptoms, the book is on loan.....

http://i.makeagif.com/media/4-25-2017/udEI7l.gif
If you rub a bit of bar soap on the tube when it turns black its but about ready to dissolve into a puddle.
http://makeagif.com/i/udEI7l

[Flettner]

The problem with that Neil is that what frame sections can be obtained (in Europe) are odd shape and have internal divisions making mandrel bending difficult. Not impossible, granted. Plain rectangular tube is, by contrast, easy, as well as in plentiful supply.
The dedicated frame sections are also usually in a 7000 series air/time hardening alloy which means no heat treatment post weld.

I haven't yet seen the vid ChrisC posted, next time I'm on broadband I'll have a look. Bradley detailed the bending of frame spars in the book which was done in multiple bends under a press, going to around .020in deformation each press. Form tools were used too.

I'm actually suffering withdrawal symptoms, the book is on loan.....

Bike frames (pedal) were made from 7000 series but it's fatigue resistance was not as good and older 7000 alloy bikes were not worth owning, they all cracked sooner or later. On the other hand 6000 series frames, although a little heavier, have much better fatigue resistance. many early units are still operating.
I wouldn't bother with 7000 series frames, just (expensive) trouble waiting to happen.
Interesting to note that all our Gyro Copter rotors, rotor heads and frames are all still made from 6061 T6. Frames and Rotor heads are bolted together with the rotors being bonded (and bolted at the hub also)
6061 T6 is good all round performer.

[husaberg]

Bike frames (pedal) were made from 7000 series but it's fatigue resistance was not as good and older 7000 alloy bikes were not worth owning, they all cracked sooner or later. On the other hand 6000 series frames, although a little heavier, have much better fatigue resistance. many early units are still operating.
I wouldn't bother with 7000 series frames, just (expensive) trouble waiting to happen.
Interesting to note that all our Gyro Copter rotors, rotor heads and frames are all still made from 6061 T6. Frames and Rotor heads are bolted together with the rotors being bonded (and bolted at the hub also)
6061 T6 is good all round performer.

Honda MX Frames are 7005 and it says to use a 5356 welding rod (According to HRC)
they are age hardened after welding.

Yamaha had a lot of trouble with their MX frames as well not the tubes and forgings but actually the welds
330364

[Muciek]

I have wanted to install eccentric bearing races into frame headstock so I can alter the rake angle there's plenty of space, but I'm wondering how I can do this easiest way so the forks would be pointing straight down not sideways , anybody have an idea how to do this?

[190mech]

The old CanAm motorcycles in the 70's and 80's had a replacable top and bottom eccentric that was keyed into the head tube,I'm sure pics could be found on google..

[mr bucketracer]

I have wanted to install eccentric bearing races into frame headstock so I can alter the rake angle there's plenty of space, but I'm wondering how I can do this easiest way so the forks would be pointing straight down not sideways , anybody have an idea how to do this?bimota do it the easyist way , barrel type roller at the bottom and a offset top , only have to change to top to re offset it

[WilDun]

Although we are not talking aluminium alloy here, I have heard that going back quite a few years there were some clever old guys who were very accomplished pipe benders who just used strategic heating and cooling alone to make the shapes required.
I guess it was time consuming in a factory situation - could this technique also be applied to extruded aluminium in our situation? - it's not really clear (in the video) whether Kymco actually used a lot of force or not.

Grumph maybe you can tell us how John Britten did it with his "artistic" exhausts.

I think Neil has gained a lot of experience with aluminium alloys in his aircraft construction.

[Grumph]

Although we are not talking aluminium alloy here, I have heard that going back quite a few years there were some clever old guys who were very accomplished pipe benders who just used strategic heating and cooling alone to make the shapes required.
I guess it was time consuming in a factory situation - could this technique also be applied to extruded aluminium in our situation? - it's not really clear (in the video) whether Kymco actually used a lot of force or not.

Grumph maybe you can tell us how John Britten did it with his "artistic" exhausts.

I think Neil has gained a lot of experience with aluminium alloys in his aircraft construction.

In the short time i worked for John, the pipes i was asked to work on were cut and shut welded, not very nice. I don't know who did the later ones, I've heard that Wob was involved. It's possible that a guy here in ChCh who was heat bending filled tube for car race pipes may have done them. He certainly did some nice work for other people.
I'm sure Neil has vast experience with alloy fabrication Will. The problem with bike stuff is that for preference your frame spars are not rectangular section - usually with what is the top outer corner beveled off. And usually with at least two internal dividers running the full length of the piece too. Looked at full frame post fabrication heat treatment years ago and realised it would need to be done in a jig to maintain alignment. Which raises differential expansion problems...So the 7000 series alloys which age harden post weld are ideal. Most alloy race frames now are 7000 series extruded spars welded to 7000 series pieces CNC produced.
FWIW I've arranged to let Neil have a look at Bradley's book before it comes home.

[husaberg]

I have wanted to install eccentric bearing races into frame headstock so I can alter the rake angle there's plenty of space, but I'm wondering how I can do this easiest way so the forks would be pointing straight down not sideways , anybody have an idea how to do this?
here is a Few
https://www.kiwibiker.co.nz/forums/showthread.php/145224-Race-chassis?p=1130370335#post1130370335
You are far more likely to notice a change in trial than rake.

[guyhockley]

I'm sure Neil has vast experience with alloy fabrication Will. The problem with bike stuff is that for preference your frame spars are not rectangular section - usually with what is the top outer corner beveled off. And usually with at least two internal dividers running the full length of the piece too.
According to Alan Cathcart, Mike Eatough (I think?) investigated various extrusions for the HD Superbike and concluded that none of them had any advantage over a plain rectangular tube. Packaging and/or ergonomics might dictate otherwise in some cases, I guess. John Bradley says Tigcraft used an industrial section and random-bloke-in-the-paddock told me it was something to do with truck bodywork...
One of the Paton V4 2 strokes had a frame from stacked tubes. I had a fractured, no common language, chat with the Paton bloke in attendance and they used 4 lots of 25 x 3 square to get a 100 x 25 "extrusion". I tried to ask if they did anything to the internal faces but it was beyond our level of communication. Later, I found an Italian magazine article that seemed to say it had 6mm thick webs. Material was something like Aerocordal... Roehr in the states does something similar with steel square section.
Team Roberts fabricated their frame spars from flat stock then bent with cerrobend or similar.
I'm away from computer and WiFi so this is all unverified memory, just like the old days!

[guyhockley]

I have wanted to install eccentric bearing races into frame headstock so I can alter the rake angle there's plenty of space, but I'm wondering how I can do this easiest way so the forks would be pointing straight down not sideways , anybody have an idea how to do this?
You want vertical forks?

[guyhockley]

The old CanAm motorcycles in the 70's and 80's had a replacable top and bottom eccentric that was keyed into the head tube,I'm sure pics could be found on google..
Think the CanAm, and Ducati, have larger than usual headstock's for their adjustable Gubbins?

[husaberg]

According to Alan Cathcart, Mike Eatough (I think?) investigated various extrusions for the HD Superbike and concluded that none of them had any advantage over a plain rectangular tube. Packaging and/or ergonomics might dictate otherwise in some cases, I guess. John Bradley says Tigcraft used an industrial section and random-bloke-in-the-paddock told me it was something to do with truck bodywork...
One of the Paton V4 2 strokes had a frame from stacked tubes. I had a fractured, no common language, chat with the Paton bloke in attendance and they used 4 lots of 25 x 3 square to get a 100 x 25 "extrusion". I tried to ask if they did anything to the internal faces but it was beyond our level of communication. Later, I found an Italian magazine article that seemed to say it had 6mm thick webs. Material was something like Aerocordal... Roehr in the states does something similar with steel square section.
Team Roberts fabricated their frame spars from flat stock then bent with cerrobend or similar.
I'm away from computer and WiFi so this is all unverified memory, just like the old days!

Honda always ran extruded sections for GP as well.later years.

The Fireblade from memory has a 4 internal section
The ROC frames that Roberts ended up using as Yamaha f-ed theres up for a few years were pressed in concrete formers churned out on CNC machines using a special froggy areospace alloy.
betting they never made any money out of them. carpental rings a bells as the name
The Harris frames were bent twisted and pounded with a lump hammer and lots of love by Alf Mossel.
150 seperate parts
https://www.kiwibiker.co.nz/forums/showthread.php/145224-Race-chassis?p=1130228780#post1130228780
Spondon used to sorse some extruded sections for some of there later frame.
NWS made them the same as Harris.
https://www.kiwibiker.co.nz/forums/showthread.php/145224-Race-chassis?p=1130228408#post1130228408

[guyhockley]

Various frame spars, mostly ali extrusions, but the small CBR600 one is steel and there are some fabricated ones, too.

[guyhockley]

Couple more including a swinging arm.

[Ocean1]

Girders are good where forces are largely in a single plane. Parallel ones are cheaper, but where loads aren't uniform they don't make much sense.

So if you're using a perimeter concept frame why would you use an extrusion instead of fabricating a beam based on the variable loads involved?

[Michael Moore]

why would you use an extrusion instead of fabricating a beam based on the variable loads involved?

If a production frame: cost. If a one off, easier construction if the extrusions are readily available to you.

[Grumph]

The GSXR frames pictured above point up how much going to the simpler beam frames saved in fabrication time - and cost.

The half - shell pressings which are then seam welded are probably cheaper initially than an extrusion - but still have to be seam welded.
Given that they can be produced in already curved form - and sized appropriate to the loads at any given point they are probably more cost effective than parallel extrusions which still have to be bent...

But later still are the current frames which are using more cast sections than before. They can be produced quickly and can be sized appropriate to loads as can be seen in the Buell ? frame Ocean put up. Bent sections can be accurately finished as cast. Fewer welds as the main pieces get bigger too. Even automated welds cost money.

Not a lot of this is appropriate to the home builder though...Unless you want to get into limited volume presswork.

[husaberg]

Various frame spars, mostly ali extrusions, but the small CBR600 one is steel and there are some fabricated ones, too.
The GSXR750 Srad had geometry entirely based on Kevins RGV500 of the time. likely a bit wider at the top.
http://www.vansingel.be/96frame.jpghttp://oldskoolsuzuki.info/wp-content/uploads/2015/10/12.jpg<img src="http://thumbs.picclick.com/00/s/MTIwMFgxNjAw/z/~O8AAOSwbwlXBVOo/$/Suzuki-Gsxr750-Srad-Good-Hpi-Clear-1996-Main-_57.jpg" height="370px"/>

One of the most hideous tails ever made though.

If a production frame: cost. If a one off, easier construction if the extrusions are readily available to you.

Yip, hence Honda's love for them.

[Ocean1]

If a production frame: cost. If a one off, easier construction if the extrusions are readily available to you.

Yes, cheap and easy.

But they often then spend a lot bending them and adding detail to accommodate design deficiencies caused by the use of parallel sections.


The GSXR frames pictured above point up how much going to the simpler beam frames saved in fabrication time - and cost.

The half - shell pressings which are then seam welded are probably cheaper initially than an extrusion - but still have to be seam welded.
Given that they can be produced in already curved form - and sized appropriate to the loads at any given point they are probably more cost effective than parallel extrusions which still have to be bent...

But later still are the current frames which are using more cast sections than before. They can be produced quickly and can be sized appropriate to loads as can be seen in the Buell ? frame Ocean put up. Bent sections can be accurately finished as cast. Fewer welds as the main pieces get bigger too. Even automated welds cost money.

Not a lot of this is appropriate to the home builder though...Unless you want to get into limited volume presswork.

Yes Buell XB series. Not a spectacularly light frame, but there isn't much on an XB that isn't either frame or engine, (shades of Collin Chapman). Dry weight around 178kg iirc.

Home build from pressed shells? Why wouldn't you? It's no more technically challenging than bending extrusions and fabricating / machining intersection pieces. Yes you have to make press dies, and there might be an hour's extra welding involved but the big advantage is the welds are all longitudinal and as far from the neutral axis as you can get, not laterally, across the highest load point cross section on the frame.

You don't have to cast the headstock either, probably better not to in fact, starting with a lump of 6" round 6061 would be better than the nearest casting equivalent from both structural and welding perspectives.

Now the swingarm I probably would stick with extrusions....

[WilDun]

.........frame Ocean put up. Bent sections can be accurately finished as cast. Fewer welds as the main pieces get bigger too. Even automated welds cost money.

Call me old fashioned, but cast frames would still worry me (cracking and shattering), however I do realize there have been big advances in casting technology and materials.

What interests me most is the type of casting technique employed, obviously it's not something someone with a home foundry could do (really defeats the purpose for homebuilt machines) - very interesting just the same!
Is it done by 'shell moulding' with resin sand or 'squeeze casting in metal dies' and what type of alloy is used? - probably needs to be ductile and also weldable (as well as castable!) - I guess it's heat treated after welding also ??
It all seems pretty expensive to me and would obviously have to be produced in large quantities with expensive specialized machinery to be viable!

I would be inclined to agree with the pressed shell idea too!

As always, I could be wrong.

[husaberg]

Call me old fashioned, but cast frames would still worry me (cracking and shattering), however I do realize there have been big advances in casting technology and materials.

What interests me most is the type of casting technique employed, obviously it's not something someone with a home foundry could do (really defeats the purpose for homebuilt machines) - very interesting just the same!
Is it done by 'shell moulding' with resin sand or 'squeeze casting in metal dies' and what type of alloy is used? - probably needs to be ductile and also weldable (as well as castable!) - I guess it's heat treated after welding also ??
It all seems pretty expensive to me and would obviously have to be produced in large quantities with expensive specialized machinery to be viable!

I would be inclined to agree with the pressed shell idea too!

As always, I could be wrong.

Greeves I beams downtube Sand cast.
330497
Norton 750 Cosworth Challenge had a rather nice cast alloy swingarm with a real neat Chain and Sprocket set up disc was outside the chain so it was QD wheel and Sprocket
330498330499330500330501
Honda did quite a few Castec frames VTR250 and NSR125
Likely investment casting or die and investment casting
330502
I have a hollow section cast swingarm made by renthal for my Husaberg its about 1 kg lighter than my already light fabricated std swingarm

[F5 Dave]

The Japs banged on at the time (early 2000s) of development of a new high pressure/purity method which made this all more feasible

[Ocean1]

The Japs banged on at the time (early 2000s) of development of a new high pressure/purity method which made this all more feasible

New alloy? Or new moulding process?

There's more or less a continuous range of processes from cast to wrought to forged. But the big improvements in strength occur around the points where the material gets hot enough to form distinct crystals as it cools, (cast), the point where the crystals are stretched and elongated without getting hot enough to actually re-melt them (wrought) and then again when the material is less hot again, and more pressure is used to shape it, (forged). The extra strength comes from aligning the grain structure of those crystals with the shape of the product, and with some tweaks to the forging process even better aligned with the expected loads.

I'm really impressed with the fact that what I already instinctively knew as a kid, that hitting something really really hard makes it better turns out to be correct in the real world. Turns out I wasn't right about much else.

[Grumph]

Back to the half pressings....I have two FZR250 frames here (thanks again Neil) which are superb examples of just what has been said.
Curved pressings - about 3mm thick - seam welded. But not continuously, some areas are just spot welded. Considerable overlap too.
I'm unsure about the steering head, it could even be forged. Other bits are definitely diecast.
No internal ribbing in either frame or swingarm - obviously for a 250/4 they didn't consider it necessary.
Quite light, simple and probably much cheaper to make than the part extrusion, part pressed, part cast frames of the bigger FZR's

[Ocean1]

No internal ribbing in either frame or swingarm -

I've added serious rigidity to hollow sections before now by filling them with epoxy/microspheres.

Might add a couple of Kg to a typical bike frame. Can't supply actual numbers but I reduced the wall thickness of a structure dramatically using that system.

[Grumph]

I've added serious rigidity to hollow sections before now by filling them with epoxy/microspheres.

Might add a couple of Kg to a typical bike frame. Can't supply actual numbers but I reduced the wall thickness of a structure dramatically using that system.

Guy I know who builds drag car frames recommends foam filling frame tubes. He did quote me the figures for improved stiffness but it was a while ago...

I know at least one of his foamed frames has survived a brake failure at the end of the Ruapuna dragstrip. End over end and the pilot walked away.

[guyhockley]

Bimota, supposedly, had a frame that was internally pressurised to support the extremely thin wall tubing. I'm sceptical, I think it had a valve for pressure testing for cracks plus a bit of racers' bullshit.
Weirdly, my phone's spell checker changed Bimota to Nikita!

[guyhockley]

Back to the half pressings....I have two FZR250 frames here (thanks again Neil) which are superb examples of just what has been said.
Curved pressings - about 3mm thick - seam welded. But not continuously, some areas are just spot welded. Considerable overlap too.
I'm unsure about the steering head, it could even be forged. Other bits are definitely diecast.
No internal ribbing in either frame or swingarm - obviously for a 250/4 they didn't consider it necessary.
Quite light, simple and probably much cheaper to make than the part extrusion, part pressed, part cast frames of the bigger FZR's
The FZR250 frames sound similar to the ZX600 section I posted, then. Presumably ali but some early Yam Deltabox frames are aluminium looking but actually painted steel. Latest R1 I've peered at under the fairing looks to have a fully cast frame in 2 half sections bolted together.
Aprilia RS125 road bikes have had a swinging arm like that for years as well as fully cast frames. They also have a plate on them giving their torsional stiffness.

[Ocean1]

Guy I know who builds drag car frames recommends foam filling frame tubes. He did quote me the figures for improved stiffness but it was a while ago...

I know at least one of his foamed frames has survived a brake failure at the end of the Ruapuna dragstrip. End over end and the pilot walked away.

Walking away is always an excellent idea.

One of the products I developed that used epoxy/microspheres was a deep water float. Was good for 4000 meters, 6000psi in the old money, and I had someone trying to sell me some syntactic foam which is apparently the duck's nuts for stuff like that. They use it a lot in advanced naval applications, I don't think anyone else can afford it.

One of the problems with using any of the high compression strength stuff in a bike frame is you wouldn't get any second chances with it, throw it down the road once and you'd have no idea if the core had been compromised.

[guyhockley]

http://m.ebay.co.uk/itm/APRILIA-RS125-frame-with-sub-frame-swingarm-early-model-1992-/152364603012?_trkparms=aid%253D222007%2526algo%253 DSIC.MBE%2526ao%253D1%2526asc%253D20150519202351%2 526meid%253D8256a1f943a84e78a4eb1e5fef881ecd%2526p id%253D100408%2526rk%253D9%2526rkt%253D25%2526sd%2 53D112304479034&_trksid=p2056116.c100408.m2460

[Ocean1]

Bimota, supposedly, had a frame that was internally pressurised to support the extremely thin wall tubing. I'm sceptical, I think it had a valve for pressure testing for cracks plus a bit of racers' bullshit.
Weirdly, my phone's spell checker changed Bimota to Nikita!

Not uncommon for big crane booms. There's an old American Crane and Hoist beastie around NZ somewhere that had every tube in it's rig sealed and pressurised with argon, transducers from every one back to a PLC in the cab. Any pressure drop triggered an override which put the load down on a pre-designated clear zone.

Can't recall what the pressure was, pretty sure it wasn't enough to represent much by way of structural improvement.

[guyhockley]

Greeves I beams downtube Sand cast.
330497


Looks like there is a story behind that particular frame.
Greeves are back in production, apparently:
http://www.greevesmotorcyclesltd.com/frame.html

[TZ350]

330529 330530

Late model NSR125 die cast frame sides bolted up around the headstock.

[Michael Moore]

Offenstadt and Shepherd did cast frames and swing arms, and the small block Guzzis came with cast swing arms.

[Frits Overmars]

330529 330530
Late model NSR125 die cast frame sides bolted up around the headstock.That Honda frame looks an awful lot like an Aprilia frame.
330537

[F5 Dave]

Both designed and made in Italy.

[Flettner]

You know, you could sand cast that quite easily for a bucket sized frame. Cast in CC601 then heat treat to T6. But a set of press tools with sheet would work very well also.
I'm assuming the bushing (bearing housing) that is bolted into the head stock could be offset bored for head stock angle adjustment?

[Grumph]

You know, you could sand cast that quite easily for a bucket sized frame. Cast in CC601 then heat treat to T6. But a set of press tools with sheet would work very well also.
I'm assuming the bushing (bearing housing) that is bolted into the head stock could be offset bored for head stock angle adjustment?

My thought on the adjustment was, if the piece is symmetrical top/bottom, but the steering axis is offset 1 degree from C/L, inverting the bolt in piece gives a 2 degree variation in rake. That's usually enough.

[Flettner]

I'm thinking frame stiffness, north to south real stiff, east to west some compliance? Or has this already been covered. These frames shown above are wide to go around carbs etc on four cylinder engines. If your engine is much thinner ie single or V twin the spars do not need to be pushed out so wide?

[Grumph]

I'm thinking frame stiffness, north to south real stiff, east to west some compliance? Or has this already been covered. These frames shown above are wide to go around carbs etc on four cylinder engines. If your engine is much thinner ie single or V twin the spars do not need to be pushed out so wide?

Compliance has been mentioned...I've quoted the Roberts team as knowing what stiffness parameters they wanted - and in which planes - when they ordered up the frames for the triple.
Got shot down - in a good way, LOL - as it would seem the opinion is that stiffer is better, at least for small homebuilts.
I'd really like the chance to back MIke Sinclair into a corner and hammer out some guidelines as he appears to have measured the stiffness of nearly everything he's ever worked on.

In my experience with larger heavier bikes, there's enough unwanted compliance from flexible wheels and forks that making it as stiff in the chassis as possible will at least make it rideable.

[husaberg]

Compliance has been mentioned...I've quoted the Roberts team as knowing what stiffness parameters they wanted - and in which planes - when they ordered up the frames for the triple.
Got shot down - in a good way, LOL - as it would seem the opinion is that stiffer is better, at least for small homebuilts.
I'd really like the chance to back MIke Sinclair into a corner and hammer out some guidelines as he appears to have measured the stiffness of nearly everything he's ever worked on.

In my experience with larger heavier bikes, there's enough unwanted compliance from flexible wheels and forks that making it as stiff in the chassis as possible will at least make it rideable.

http://www.cycleworld.com/2015/10/16/motogp-racing-chassis-flex-and-stability-are-key-to-winning-races#page-3

“Chatter, stability, chassis flex, and engine characteristics are mysteriously entangled. There is no textbook.
As tires evolve, chassis must evolve. When Michelin brought a big new rear tire in 2006, it set every chassis to chattering. The usual emergency fixes (like lead-filled axles to tune out certain flex frequencies) worked for Honda but not for Yamaha. Valentino Rossi was stopped by chatter for four races, and only reverting to the 2005 chassis enabled recovery. Chatter, stability, chassis flex, and engine characteristics are mysteriously entangled. There is no textbook. The ’06 championship was lost.


No chassis can be perfect—just better or worse. Motorcycle roadracing might have once been a noble contest of engine power and durability, but with engine development now frozen in-season it has become a struggle to produce chassis properties that riders can use to race hard all the way to the last lap. Chassis and suspension function as a filter system, softening or stopping inputs that fatigue the tires, letting through inputs that riders need to know where the edge is.


In 2007, the problem was Casey Stoner on the 800cc Ducati with revolutionary Bridgestone tires. When Rossi switched to Bridgestones, weight had to be shifted rearward on the Yamaha and its center of mass raised to transfer weight forward quickly on braking. Yamaha’s 2008 chassis’ lateral stiffness cut another 10 percent (making it now just two-thirds as stiff as the 2004 baseline), and with refined electronics and Bridgestone tires Yamaha riders dominated 2008–2010
http://www.insidemotorcycles.com/blogs/item/400-controlling-flex-in-motogp.html

In the current issue of Inside Motorcycles, I wrote about the 2012 MotoGP bikes and touched on chatter and chassis flex. I addressed chatter in my previous blog, and will go into more detail about chassis flex here. Chassis designers have long known that some flex is a good thing as it acts as the motorcycle's suspension at extreme lean angles. With tires getting grippier and wider over time, motorcycles are getting increasingly more lean angles and the importance of chassis flex increases accordingly.
Incorporating flex into a chassis is not easy, as strength and stiffness are still desired in some directions while flex is advantageous only in certain directions. Typically, manufacturers express chassis rigidity in three ways: vertical, lateral and torsional. The chassis is generally desired to be stiff vertically, to absorb braking and acceleration forces, while some flex is desirable in the lateral direction to act as suspension. Torsional stiffness keeps the wheels in line, but some twisting can also translate to lateral movement at the contact patch. Yamaha published a graph showing the M1's changing chassis rigidity over the past few years, with vertical stiffness increasing and lateral stiffness decreasing - just what you would expect as tires get stickier and the bikes lean further.

https://motomatters.com/analysis/2011/08/08/the_trouble_with_the_ducati_desmosedici_.html

As tuneable flexibility has become increasingly important, the attractiveness of alternatives to aluminium has also grown. Traditional aluminium has the benefit of being light and easy to work with, but as MotoGP chassis designers push the limits, they also run into a few limitations. Engineering in flex is a matter of designing chassis elements with a specific thickness and shape, but the underlying properties of aluminium mean that at some point, achieving the precise amount of flexibility required means sacrifices strength. The way to get around this problem is by making elements longer, allowing a mass (usually, the mass of the engine) to use the greater leverage provided by a longer element (such as an engine spar connecting the engine to the main chassis beam) to provide the flexibility without sacrificing rigidity.
When the rest of the world switched from perimeter steel tube frames to aluminium twin spar frames, Ducati took a different but still ingenious approach. Instead of wrapping the engine in aluminium box section, Ducati welded up short sections of light steel tubing to create a trellis frame. The advantages were that the chassis was relatively easy to tune, by changing the diameter and position of the individual tubing sections and redistributing the load and the flexibility, and Ducati persevered with the design for six years until they dropped it in favor of carbon fiber.


The problem is not that CF is too stiff, but that the feedback it provides differs so completely from conventional aluminium. The property most often quoted is hysteresis, which in this instance, refers to the rate at which absorbed energy is returned. One of the benefits of CF is the fact that it can be made to damp vibration, its hysteresis meaning that the energy absorbed from an input (such as striking a bump) is released in a much more controlled fashion. Tap an aluminium tube and it rings like a bell; tap a CF tube and it emits a dull thud.
This is a property that Ducati had hoped would help them solve the problem of chatter (or extreme vibration over bumps) but it had an unintended side effect. Just as with the original attempts at using carbon fiber for chassis, starting with the Cagiva back in 1990, the damping also removes some of the feel from the front end. When used to build swingarms - as Aprilia had been doing for their 250cc racers for several years - this damping helps remove unwanted vibration, but at the front of the bike, that vibration also contains valuable information. As Guy Coulon once explained to me on the subject of unconventional front suspension systems, what is required of a racing motorcycle is that the information from the tarmac should pass directly into the rider's brain with as little interference or loss of data as possible. Any system which removes or alters that information means that the rider has to learn to interpret the feedback almost from scratch. All of the experience gained in his many years of racing is of little value in interpreting what he is feeling.
This is what caused the Cagiva to fail back in the early 1990s. The riders, brought up on a generation of steel and aluminium chassis, simply could not understand the feedback they were receiving from the machine. And this seems to be at least one part of the problem with the Ducati Desmosedici: the carbon fiber subframe connecting the front forks to the front of the engine may be damping the vibrations too much, reducing the amount of information traveling from the front tire up into the rider's brain. Alternatively, it may be returning too much information, providing more feedback than most riders are used to receiving. Filtering out this new (and not necessarily useful) information may be what is confusing the riders about the feel.
http://motodna.net/motogp-tech-talk-swingarms/

The chassis should bend like a tree according to Yamaha legend Engineer Masao Furusawa.
A longer chassis creates a long lever, which allows flex to be designed more gradually, accurately and effectively.
So just how do MotoGP Engineer’s work out the right amount of strength, stiffness, flex and in what plane or direction?
Well, Engineers increasingly evaluate huge amounts of data in MotoGP, which can be measured, quantified and related to the bikes performance.
However it’s difficult to quantify what the rider feels and it’s this conundrum that ensures race engineering remains a balance between an empirical art and science.
Subsequently the factories go through an incredible amount of research and development to settle on the motorcycles overall handling performance.


Flex is the chassis ability to absorb force, bend in different directions and return to its original position.
Lateral means sideways, so lateral flex is bending in the side or the bikes vertical plane namely when the bike is cornering on extreme lean angles

Lateral stiffness is a trickier one to balance; too much and the bike will suffer a lack of grip at extreme lean angles. RSV4 frame has more lateral flex than the RSV-R for this reason.
330538330539

https://www.kiwibiker.co.nz/forums/showthread.php/145224-Race-chassis?p=1130236080#post1130236080


I'd argue that a fexible arm actually makes a bike more prone to highside...until they redesigned it the Britten arm was very flexible.
After so many years, Andrew or one of the others may be prepared to go public on what we regularly saw when they tested at Ruapuna.
The only thing that saved innumerable highsides was the ability to keep the rear spinning...if the rider was brave enough.


Not a flexible arm in itself but a small amount of only lateral flex. The idea as i understand it is to both be able to feel the limit and absorb some of the force rather than have it break fee on the limit and then slide and catch which is the start of most classic highsides.
I am not saying they dont make them strong what i am saying is what i understand they don't try to achieve ultimate rigidly against sideways force.Like they did in the 90's.
All the alloy MX frames are also designed with flex in them as well for a less rigid feel from what i understand as well.
After riding a 97 CR250 framed bike i can understand the MX bit. Every bike subsequent to this model has been progressively pared done for more flex.
Although this saves weight and helps the suspension work better no doubt as well.

When Kenny Roberts junior went to Suzuki he tested the bike and asked for a less stiff chassis
Suzuki obliged
he tested it and it was worse
Willings asked if they had tested the stiffness Suzuki said no. So they tested it.
It turned out the less stiff chassis was actually considerably stiffer.

[Frits Overmars]

I'm assuming the bushing (bearing housing) that is bolted into the head stock could be offset bored for head stock angle adjustment?That is what we tried on an Aprilia RS50 moped frame. Worked well.


Chassis designers have long known that some flex is a good thing as it acts as the motorcycle's suspension at extreme lean angles. With tires getting grippier and wider over time, motorcycles are getting increasingly more lean angles and the importance of chassis flex increases accordingly.Everybody calls it flex; I'd rather call it lateral springing. And springs have a tendency to spring back, bringing an unwanted resonance into the frame.
What's needed is lateral suspension, i.e. springing with damping. If you can incorporate that, the frame and wheels can and should be as rigid as possible.

[guyhockley]

Offenstadt and Shepherd did cast frames and swing arms, and the small block Guzzis came with cast swing arms.

I slightly helped out a racer called Danny Pullen at a couple of belgian classic meetings. At the time he had a Shepherd Suzuki (GT250 based frame) and a TZ with a Shepherd cast frame. If I remember correctly, he said he was in partnership with frenchman and they had started to reproduce the cast frames but were having trouble getting the swinging arms to come out properly. Think they may have had the original moulds, but I'm not sure. Anyway, this was a few years back, I don't have any contact details and Google came up with very little except he now seems to be racing road bike based 250 and 500 Suzukis. Not heard of any new Shepherd frames...

[husaberg]

Here is the Husaberg cast swing arm 2001
Don't be fooled by the pic its all one piece made by renthal (in Ireland i think.)
quite a few cracked (due to a poor material batch) and were replaced under warranty
330569330570
With the 1kg heavier traditional fabricated 2000 version.
330571

I would say KTM ones are made the same as the cast Husaberg.
330573330572

Yip http://motocrossactionmag.com/bike-tests/2011-ktm-150sx-motocross-test-perhaps-the-best-bike-for-riders-looking-to-maximize-the-fun-of-racing

Swingarm updates were made possible by an updated manufacturing process called “single component casting,” which eliminates welding. Additionally, KTM refined the swingarm’s flex properties and its shock mounting position.

[Ocean1]

Flex is the chassis ability to absorb force, bend in different directions and return to its original position.
Lateral means sideways, so lateral flex is bending in the side or the bikes vertical plane namely when the bike is cornering on extreme lean angles.


Not sure that makes perfect sense. But I'll just point out that the XB swingarm I posted earlier was mounted on the engine, which was isolated from the frame via rubber mounts and some tricky wee tie rods.

I wonder if that's why, with no linkage and nothing special by way of a rear shock that back end performs remarkably well....

[Muciek]

Hi, I have a question regarding tires in bikes, we race here mostly with 18" rims (classic bikes) and is there any rule of thumb how to choose tire for a bikes? For example 90-110 kg and 30-40 of hp? Is there a benefit to use for example rear 120 tire instead of 90? Any info or guidelines would be appreciated. Cheers

[guyhockley]

Here is the Husaberg cast swing arm 2001
Don't be fooled by the pic its all one piece made by renthal (in Ireland i think.)
quite a few cracked (due to a poor material batch) and were replaced under warranty


I would say KTM ones are made the same as the cast Husaberg.


Yip http://motocrossactionmag.com/bike-tests/2011-ktm-150sx-motocross-test-perhaps-the-best-bike-for-riders-looking-to-maximize-the-fun-of-racing

That's really nice work. I presume the holes are for the cores. My neighbour's daughter has a KTM road bike and that has a cast arm but quite different (and easier/cheaper to make, I guess).
Picture stolen from Ebay.

[F5 Dave]

Hi, I have a question regarding tires in bikes, we race here mostly with 18" rims (classic bikes) and is there any rule of thumb how to choose tire for a bikes? For example 90-110 kg and 30-40 of hp? Is there a benefit to use for example rear 120 tire instead of 90? Any info or guidelines would be appreciated. Cheers
Always build your racebike from the tyres up. Choose the best tyres available within the rules, then go from there.
I used to run 90 section front slicks on the back of my 50. A lot of us did. But it became apparent that around a kart track at least, those with 115 could lean on them harder without falling off and were faster. I converted and benefited.

[Grumph]

Hi, I have a question regarding tires in bikes, we race here mostly with 18" rims (classic bikes) and is there any rule of thumb how to choose tire for a bikes? For example 90-110 kg and 30-40 of hp? Is there a benefit to use for example rear 120 tire instead of 90? Any info or guidelines would be appreciated. Cheers

Your weight and power figures are right where my Aermacchi replicas sit.
Most customers have used 90/90 fronts and 100/90 rears - occasionally 120 section - and been quite happy with that.
Most Classic rules specify rim widths - usually WM2 or 3 - which will limit your choice of sizes anyway.

One customer was able to buy Avons left from a test session where Schwantz evaluated a huge number of tyres using a 500 manx Norton.
The pair he's got were deemed too soft for a 500 - they're perfect for a 350 macchi.

[husaberg]

Not sure that makes perfect sense. But I'll just point out that the XB swingarm I posted earlier was mounted on the engine, which was isolated from the frame via rubber mounts and some tricky wee tie rods.

I wonder if that's why, with no linkage and nothing special by way of a rear shock that back end performs remarkably well....

As were Norton Commandos
Plenty of bikes including the RS125 NF4 the Ducati supermono have no linkages.
330609330613
Husasberg and KTM dirt bikes They have a PDS shock though
330614
Most GP race bikes went to linear rate linkages anyway, as far as i know.
Properly set up with decent dampers a twin shock can also be excellent, ALA Norton rotary race bike, But fashion dictates monoshock must be better.
330608

[Grumph]

I wouldn't be so quick to use the Norton rotaries as an example of good twinshock practise.

AFAIK, they went twinshock because they reckoned the single damper was overheating behind the rotary. Then went back to single...

Peter Williams is reported to have laughed and said "they haven't learned anything in 20 years"

[husaberg]

I wouldn't be so quick to use the Norton rotaries as an example of good twinshock practise.

AFAIK, they went twinshock because they reckoned the single damper was overheating behind the rotary. Then went back to single...

Peter Williams is reported to have laughed and said "they haven't learned anything in 20 years"

I thought it was because Colin Seeley wanted them.
Ken McIntosh wasn't convinced that mono were better.
Those moriwaki Honda CBX750 and NS250 went well with twin shocks.
330620330621
Mounted through and under the swingarm.
Can't find a pic of the 250....

[Ocean1]

As were Norton Commandos

Swingarm mounted on isolated engine you mean?


Plenty of bikes including the RS125 NF4 the Ducati supermono have no linkages.
Husasberg and KTM dirt bikes They have a PDS shock though
Most GP race bikes went to linear rate linkages anyway, as far as i know.
Properly set up with decent dampers a twin shock can also be excellent, ALA Norton rotary race bike, But fashion dictates monoshock must be better.


Aye. None of my current rides have linkages. No real preference, just coincidence. On the other hand I don't do much serious vertical shit nowadays.

One of the more practical negatives with linkages is you've got more bushes/bearings to wear, which causes a lot more hysteresis in the system. So unless you're really on top of your maintenance I doubt a casual rider would benefit. And I've rebuilt my share of completely fucked linkages that owners thought "might need a bearing" but were still considered to "feel good".

It's also quite possible to get some progressive travel without a linkage, if a bit tricky.

What I was really interested in was the observation that controlled lateral movement was the hot mumble, that the Buell system seemed to address that and seemed, (to a rank amateur) to perform accordingly.

And yes, the last thing you could want as a design engineer is a Dedicate Follower of Fashion...

[husaberg]

Swingarm mounted on isolated engine you mean?...

yip



And yes, the last thing you could want as a design engineer is a Dedicate Follower of Fashion...

There is the rub if you are a designer if what you design isn't considered fashionable you might not have a job. uless its for a museum
I admire clever stuff the most, thinks that works great and is also pretty to look at. as a whole complete form

I could spend hours looking at the details on a works Ducati race bike or a 1950's Ferrari.

[Ocean1]

yip

Wonder if carefully though out rubber swingarm bushes might not be a better idea. Far lower maintenance and real easy to change for tuning.


There is the rub if you are a designer if what you design isn't considered fashionable you might not have a job.

My old man was a product design engineer. He always said there was nothing more redundant than a successful development engineer.

The other thing about competition design is that the real objective isn't just to win, it's to win using bikes that look like next years production model. And the accountants have a lot more influence on that second bit than any engineer does on the first bit.

[Frits Overmars]

Properly set up with decent dampers a twin shock can also be excellent.Until you fit pressurized twin shocks in the old-fashioned position near the rear axle; the gas pressure alone already gives too much preload.


It's also quite possible to get some progressive travel without a linkage.Yep, you can achieve up to 15% progressiveness that way, which is enough for road racing.
Omitting the linkage saves weight and components, and avoids wear and extreme forces acting on the frame.


What I was really interested in was the observation that controlled lateral movement was the hot mumbleTry searching for "Suspension Smith". I haven't got a link handy but I will post it when I find it.

[husaberg]

Wonder if carefully though out rubber swingarm bushes might not be a better idea. Far lower maintenance and real easy to change for tuning.



My old man was a product design engineer. He always said there was nothing more redundant than a successful development engineer.

The other thing about competition design is that the real objective isn't just to win, it's to win using bikes that look like next years production model. And the accountants have a lot more influence on that second bit than any engineer does on the first bit.

Not only that but the sales guys have a lot of influence hence Honda pro-arm on a NSR250R and NSR500V.
On the other side KTM with its mainly black bikes with steel frames and non linkages being made in odd displacements made themselves a huge niche.

What I was really interested in was the observation that controlled lateral movement was the hot mumble

Sorry i missed that. i think its only an issue of bikes and demi gods at the limit on very very sticky tyres at big lean angles.
its all explained in the links i posted.
https://www.kiwibiker.co.nz/forums/showthread.php/145224-Race-chassis?p=1131044358#post1131044358

[Ocean1]

Yep, you can achieve up to 15% progressiveness that way, which is enough for road racing.
Omitting the linkage saves weight and components, and avoids wear and extreme forces acting on the frame.

Try searching for "Suspension Smith". I haven't got a link handy but I will post it when I find it.

I will. In the meantime I found this interesting...

http://dirtbikemagazine.com/ktm-suspension-shootout-pds-vs-linkage/

[Ocean1]

Sorry i missed that. i think its only an issue of bikes and demi gods at the limit on very very sticky tyres at big lean angles.
its all explained in the links i posted.
https://www.kiwibiker.co.nz/forums/showthread.php/145224-Race-chassis?p=1131044358#post1131044358

So I saw, hence the comment.

And yes, my assessment is necessarily that of an amateur. Nonetheless my experience with those Buells is that they seem to offer better feedback than conventionally mounted rears.

[husaberg]

So I saw, hence the comment.

And yes, my assessment is necessarily that of an amateur. Nonetheless my experience with those Buells is that they seem to offer better feedback than conventionally mounted rears.

I am a PRO, Googler

[Frits Overmars]

I am a PRO GooglerHuh? You google, dressed in miniskirt and high heels? Does it help?

[Michael Moore]

A certain amount of rear suspension design is dictated by packaging/mass centralization concerns. If there's a more important component that gets a higher priority then the suspension can be relocated, and with linkages many different configurations can give very similar suspension curves. Having linkages may be of more use on long travel dirt bikes or heavy tourers where you want more progression than a RR bike might need.


Yep, you can achieve up to 15% progressiveness that way, which is enough for road racing.
Omitting the linkage saves weight and components, and avoids wear and extreme forces acting on the frame.

The person who got me started building frames remarked that if the subframe was strong enough to support the rider it was probably strong enough for twin dampers located in the conventional position. A conventional swing arm can be just stiff enough for the loads coming up through the tires and the rest of the chassis and not need to be hugely stiffer because of large bending loads being put in by a heavily leveraged suspension.

[guyhockley]

Just to add that there have been twin shocks with linkages - Maxton and others.

[monkeyfumi]

Until you fit pressurized twin shocks in the old-fashioned position near the rear axle; the gas pressure alone already gives too much preload.

Yep, you can achieve up to 15% progressiveness that way, which is enough for road racing.
Omitting the linkage saves weight and components, and avoids wear and extreme forces acting on the frame.

Try searching for "Suspension Smith". I haven't got a link handy but I will post it when I find it.

http://pbmagforum.co.uk/index.php?/topic/49010-hossacked-blade/&page=30#index.php?/topic/49010-hossacked-blade/&page=1&_suid=1493760038720034993366612351673

This is Laurie's build thread (you will have to sign up to the PB forum to view) It started as a hossack conversion to a modern Fireblade (he has done several evolutions of girder/hossack style front ends) then progressed into looking at lateral damping. He is a clever cookie.

[Grumph]

Wonder if carefully though out rubber swingarm bushes might not be a better idea. Far lower maintenance and real easy to change for tuning.

Ever ridden a featherbed with slogged out swingarm rubber bushes ? I have and most surprisingly it wasn't bad at all...

At the time I raced a good manx and a friend turned up with a 650SS. Try this he said....There was about an inch of sideways movement at the rim.
Nice bumpy uphill curve past home - and it stayed on line. Weird.

[Ocean1]

Ever ridden a featherbed with slogged out swingarm rubber bushes ? I have and most surprisingly it wasn't bad at all...

At the time I raced a good manx and a friend turned up with a 650SS. Try this he said....There was about an inch of sideways movement at the rim.
Nice bumpy uphill curve past home - and it stayed on line. Weird.

Don't think so. But now that I think about it I did rebuild a minibike with rubber swingarm bushes, originally built by the old man with bronze.

Had all of 4" travel, wheels made out of Caterpillar pistons and wheelbarrow tyres, so I can't say whether the rear suspension improved at all or not.

I do recall that the telescopic forks were held together by the springs, you just screwed them onto bosses at either end, a feature that eventually caused me to lose the front wheel on a jump, (and several hours consciousness).

[husaberg]

Huh? You google, dressed in miniskirt and high heels? Does it help?

Come again , What sort of website did I just log into......

[philou]

Hand-formed sheet on wooden die

330724

[WilDun]

That is a good looking chassis - and made without dies (ie expensive steel press dies).

[husaberg]

Hand-formed sheet on wooden die

330724


That is a good looking chassis - and made without dies (ie expensive steel press dies).

It is a thing of beauty
This one has 28 diferent hand formed pieces in the head stock alone
Which formed a forced air system along with one of the frame rails
https://www.kiwibiker.co.nz/forums/showthread.php/145224-Race-chassis?p=1130228408#post1130228408

These ones were also hand formed, plus judious use of a press too i think
https://www.kiwibiker.co.nz/forums/showthread.php/145224-Race-chassis?p=1130228780#post1130228780

[Flettner]

Hum, I have the 'book'

[Grumph]

Hum, I have the 'book'

Well there's your tea breaks and lunchtimes spoken for, for some time.....

[philou]

Hum, I have the 'book'

Hello,

Is it really good?

Can you describe the method of forming the frame spar ?

[guyhockley]

We moved back to the UK after 28 years abroad a while ago. For various reasons, incompatibility with british stuff, helping my son etc. I left a lot of gear behind, so almost starting from scratch. Currently (not really started) using a 3m square workshop attached to the house. Apparently, it's dashed bad form, what, to store acetylene in a residential area. Has anyone advice, experience, caveats to offer on using propane for bike frames (say; 3/4" or 19mm to 4"(!) 100mm x 16swg or 1,6mm steel), please?

(Also posted this on the Ask an engineer thread)

[EssexNick]

I think the problem is more "workshop attached to the house" than anything else. A separate building made of brick or concrete should be ok but it's a gray area.

[Grumph]

My local (rural..) engineering co uses oxy/lpg - but only for cutting and pre heating/bending. They glue everything electrically.

I've seen them use it and asked at the time about any advantages. Price is the big one, much cheaper than acetylene.
Disadvantage seems to be somewhat higher gas usage than acetylene for the same heat.
I'd assume that once tip sizes and pressures were sorted, it would be usable for bronze welding.
No idea how compatible an in-line fluxer would be.

[WilDun]

My local (rural..) engineering co uses oxy/lpg - but only for cutting and pre heating/bending. They glue everything electrically.

I've seen them use it and asked at the time about any advantages. ........... No idea how compatible an in-line fluxer would be.

I bet the Vapoflux would cost an arm and a leg even if it was compatible with LPG and cancel out any savings! - then I could be wrong, I only used the stuff (way back), I didn't have to buy it.

[guyhockley]

Thanks everyone, I think I'll probably give it a go. As an apprentice I used various brazing methods from hearth/forge, town gas and air to OA, but that was a long time ago. Also used a carbon-arc "torch" to build a racer back in the 80s.
Bloke in the local gas suppliers said he's heard that oxygen consumption is much higher, but, still worth trying, I think.
Baby TIG on the wishlist, too.

Back to actual chassis (chasses?), I posted this scan on ESE for the crank picture but I thought the bolt in bracing was interesting and the apparent lack of support for the SA pivot a bit puzzling...

[Grumph]

Obviously stiff enough...I'd pick that there's some cancelling of at least vertical loads at the pivot with the lower shock mount apparently sharing the pivot pin.

[speedpro]

Wheel exerts upward force on swingarm which is resisted by suspension strut. Swingarm pivots about suspension strut connection point exerting downward force on swingarm pivot. Suspension struts under compression through bellcrank compress shock therefore also exerting a downward force of swingarm pivot. At rest all downward force on swingarm pivot is balanced by upward force on bellcrank pivot.

Looks to me like suspension compression forces result in an extension force in the frame between the swingarm pivot and the bellcrank pivot. With the geometry of the various bits this results in a force trying to rotate the bellcrank pivot about the swingarm pivot.

Without the usual pivots at the lower end the forces on the swingarm pivot and bearings will be a lot less.

Or have I got it all wrong?

[F5 Dave]

Sounds good. As long as you don't have to lean the bike over for any reason.

[Frits Overmars]

Sounds good. As long as you don't have to lean the bike over for any reason.A reason might be that a racing track has more corners than straights, and for negotiating corners without leaning over you'd need more wheels...:msn-wink: