Race chassis

[cotswold]

stolen photo's from FB

[WilDun]

Probably I was getting off track, sorry about that!
I remember at the start of the thread you talked about a simple tubular backbone frame, saying that you thought that it would be great for buckets.
How much harder (or easier) would it be to construct a mono frame like you have just posted - how well would that stand up to the kinds of stresses involved on our street circuits?
I think Michael Moore was right about tubular steel - he said it was the easiest and most forgiving material, (I don't think it would be as easy to dent!).

[Grumph]

Depends really on what your home workshop is like as to which chassis construction method works for you.
I don't have a folder - but do have welding gear. Don't want to work with composites either...

FWIW I'm told the LCR failure at Wanganui was that it punched the front shock mounting out the bottom of the monocoque.
Points up how important it is to feed the loads into a monocoque appropriately - and over a large area if possible.
LCR are not novices at that method of construction - but I bet they never anticipated an F1 outfit built for the tracks of Europe would run on the streets of Wanganui...The 600 LCR which was there was fine - but it's built to run at the IOM.

[Michael Moore]

I suspect that most any type of frame will be adequate if properly designed and built.

Tubular steel seems pretty accessible to DIY builders. Various people have built riveted alumin(i)um sheet chassis for bikes and small race cars, not to mention for homebuilt aircraft. But it looks like you need a reasonable amount of knowledge of both how to feed loads into the sheet as well as what makes for good riveted joints.

You can do welded alumin(i)um frames if you are good at welding that material and you've got some idea of what kind of alloy and rod to select AND you keep in mind that alumin(i)um is 1/3 the stiffness of steel and often has a much lower fatigue limit (remember BSA's expensive in both money and championships experience with building titanium frames that were largely copies of their steel frames).

Composites that are glued seem to be another big jump on the amount of knowledge needed, and not near as accomodating to the "let me look around and see what other people are doing so I can copy them, with maybe a bit of an extra safety factor added" method of design.

So you've got to ask yourself "do you feel lucky (knowledgeable)?"



But what do I know, I'm just a DIY enthusiast who doesn't want to risk my life any more than necessary.

cheers,
Michael

[richban]

So you've got to ask yourself "do you feel lucky (knowledgeable)?"



But what do I know, I'm just a DIY enthusiast who doesn't want to risk my life any more than necessary.

cheers,
Michael

I here you Michael. Sitting here with a broken back having yet another feeling sorry for self beer. I will be making sure anything I design will go to the people that know about these things for a safety check. Then the only dangerous piece of the puzzle will be the lump of meat trying to ride it.

[Grumph]

Well, I've now read Mike Sinclair's book - and I have more questions...I must find a way of backing Mike into a corner and getting some answered.
Looking at the nuggets of info in there, there's a potential paper to be written by Mike and Tom O'kane on chassis dynamics. I'll suggest it to Mike but getting Tom to find time might be harder.
It was most interesting to discover why the carbon fiber frames didn't work also...

One major question raised is tyre internal damping (presumably carcase design). Mike is sure the current generation of MotoGP tyres have it due to the lower pressures they're running.
I'd like to know how far down the manufacturers tyre ranges the built iin damping extends.

[husaberg]

Well, I've now read Mike Sinclair's book - and I have more questions...I must find a way of backing Mike into a corner and getting some answered.
Looking at the nuggets of info in there, there's a potential paper to be written by Mike and Tom O'kane on chassis dynamics. I'll suggest it to Mike but getting Tom to find time might be harder.
It was most interesting to discover why the carbon fiber frames didn't work also...

One major question raised is tyre internal damping (presumably carcase design). Mike is sure the current generation of MotoGP tyres have it due to the lower pressures they're running.
I'd like to know how far down the manufacturers tyre ranges the built iin damping extends.

No idea but the Suzuki GP 500 that Roberts jr ran would not work with the 16.5 tyres.
traditionally the Michelin and dunlops have very different constructions.
From memory back in the 500GP days one(i think Michelin) used to have a very stiff carcass and relied on soft rubber while the other (i think)Dunlop was a soft carcass with a harder rubbber to get the required operating temps.
The Dunlops would slide and have better feel at the limit, while the Michelin generally had better grip but let go suddenly.
Dunlop generally had better fronts and Michelin had better rears. from what i understand current Bridgestone are made similar to Dunlops and use the same design philosophy.
one a side note
The Showa and the Ohlins forks and dampers also used to very different valving techniques to achieve a similar outcome.

[Grumph]

No ,but the Suzuki GP 500 that Roberts jr ran would not work with the 16.5 tyres.

Mike was still in the game then. He says in the book it came in after he left. So it's a 4T MotoGP development.

[husaberg]

Mike was still in the game then. He says in the book it came in after he left. So it's a 4T MotoGP development.

I am 100% The 16.5 tyre was in use in 500Gp rears in 2000
fronts i think even earlier.
Mike would know better than me, but Pretty sure he was with Willings at Suzuki at the time, turning the Suzuki into a Yamaha right down to exhaust pipes and porting.
They def had 16.5 tires then, and likely even before then.
http://www.motorcyclenews.com/news/2...-inch-matters/
https://books.google.co.nz/books?id=...nsr500&f=false
https://www.yamaha-racing.com/motogp...-fighting-form
Found this its rather cool to add the turntable.

[Grumph]

To clarify. The internal damping in tyres is a 4T MotoGP development . Independent of tyre size.

[husaberg]

To clarify. The internal damping in tyres is a 4T MotoGP development . Independent of tyre size.

No idea, but the different construction of the two leading tire makers then resulting carcass strength has always been a major point of difference.
Pretty sure thats why plenty of outstanding racer couldn't make a sucessful transition from the two different tires.
Beatie and Caladora spring to mind, as ones that stuggled to go from Michelin to Dunlop but they were both 250 esk riders. Even demi god Rainey struggled on Michelins.
Does the book cover anthing on transitional dynos?

[Grumph]

No idea, but the different construction of the two leading tire makers then resulting carcass strength has always been a major point of difference.
Pretty sure thats why plenty of outstanding racer couldn't make a sucessful transition from the two different tires.
Beatie and Caladora spring to mind, as ones that stuggled to go from Michelin to Dunlop but they were both 250 esk riders. Even demi god Rainey struggled on Michelins.
Does the book cover anthing on transitional dynos?

We're talking apples and oranges. The changes to tyre construction went far past the difference between Dunlop and Michelin. Tom O'Kane went to Dunlop and ran tyres on the rollers simulating chatter. He proved it involved the whole tyre and tread vibrating back and forth on the rim - not just the contact patch.
By introducing internal damping into the tyre you remove/reduce the unknown variable spring which has been the tyre.
Looks like all the companies got onto it around the same time but it seems to have been a very quiet introduction. Perhaps some of the current probs with Michelins come down to a different method of damping resulting a different frequency of response - and a different "feel". Because there is internal damping of the carcase, pressures can be lower, footprint bigger.

Dynos - Mike says great progress was made when Bud Aksland changed to an inertia dyno.

[husaberg]

We're talking apples and oranges. The changes to tyre construction went far past the difference between Dunlop and Michelin. Tom O'Kane went to Dunlop and ran tyres on the rollers simulating chatter. He proved it involved the whole tyre and tread vibrating back and forth on the rim - not just the contact patch.
By introducing internal damping into the tyre you remove/reduce the unknown variable spring which has been the tyre.
Looks like all the companies got onto it around the same time but it seems to have been a very quiet introduction. Perhaps some of the current probs with Michelins come down to a different method of damping resulting a different frequency of response - and a different "feel". Because there is internal damping of the carcase, pressures can be lower, footprint bigger.

Dynos - Mike says great progress was made when Bud Aksland changed to an inertia dyno.

I think the tyre construction differences actually lead to the tires internal damping progression.
There was a history of dunlop and other tires in Cycle world that covered it right back for the TT100 days. I was going to post it ages ago but not sure that i actually did.
I am not sure but i think the transitional dynos are a lot more complicated than an intertia dyno but i can't find out much about them, think like a inertia they use a roll on progression but i think there is a lot more to it.
I found the quote about how different Showa and Olhlins design philosphy works.
The major suspension makers have acquired their own separate traditions in such matters.long serving vetern race engineeer warren willings once described showa as the rigid suspension
This is because Showa prefers to support loads and control motions with spring stiffness,while Ohlins tends to seek softer spring rates while controlling motions dynamically with damping.

https://books.google.co.nz/books?id=...itions&f=false

I am pretty sure cameron covers the tire stuff later as well.

my understanding is the introduction of the 16.5 lead to it because it was more prone to causing chatter.

Michelin first introduced its original 17in tyre back in 1984 – at a time when most teams ran 18in wheels. The 16.5s didn’t appear until the early ’90s. 1993 world champion Kevin Schwantz was one of the first converts and became the first rider to win using a 16.5in tyre on his Lucky Strike Suzuki at the 1994 British GP at Donington Park.
The smaller tyre was developed because riders wanted more grip to cope with ever-spiralling 500 power outputs. Tyre technology just couldn’t keep up with engine developments and riders were constantly highsiding. The results were frequently painful as tyres slid when riders powered out of corners and then suddenly snapped back into line – launching their victim over the top of the bike.
Michelin’s initial answer was to increase the tyre-to-Tarmac contact patch with a 19cm wide 17in tyre. One of these was used to good effect by Australian Daryl Beattie to win the 1993 German GP. But this wider tyre was heavier and technicians had to make radical changes to the suspension set-up.
Going for a smaller diameter tyre allowed Michelin to keep the wider contact patch and keep weight at previous levels. The 16.5’s profile is radically different to the 17’s with a triangular shape that puts more rubber on the track when the bike is cranked over on its side.
Michelin’s motorcycle competition chief Nicolas Goubert explains: " The 16.5s allow increased corner speeds. The larger contact patch also keeps temperatures more consistent, so riders can generally use a softer compound. "
So if 16.5s are that good why isn’t everyone using them?
Goubert has the answer: " The 17 offers better driving traction once the rider has lifted the bike back up and opened the throttle. Most riders still prefer this characteristic. "
And while 16.5s offer more grip in corners, it’s the 17s which turn in better because the tyres are narrower.
" There are still some aspects of the 16.5 on which we need to work, " Goubert admitted. " The extra rear-end grip can cause the front tyre to push, resulting in understeer. And the 16.5 can cause front-end chatter. "

The next devlopment was in 2005 when they even went further leading to even more chatter

Bridgestone, its factories far from Europe, had to aim its technology at developing tires with a wider performance range. Michelin went the other way, raising performance by narrowing operating range. This would be a crucial accident of history.
The following year brought more disturbances from tire development. At the end of 2005, Honda was out of traction—its bikes spun instead of going forward. Michelin replied with an even bigger, lower-pressure, softer-carcass rear that laid down an unprecedented footprint. Honda initially found chatter with this tire but overcame it. Yamaha’s early tests on the tire went well, but suddenly there was chatter that did not respond to its strongest countermeasures. At the first GP, Jerez, there were no Michelins on the front row. Bridgestone performance was not yet uniform; they performed best on high-grip tracks.
“Emergent properties” is a term used by evolutionists to describe novel results of an evolutionary line—results unpredictable from original conditions. Bridgestone’s concentration on wide range and Michelin’s upon narrow now essentially separated riders of each into distinct groups. When the Michelins worked, they performed incredibly well, leaving the Bridgestone riders behind. When Michelin missed the mark (resoundingly at Laguna Seca and Misano), they were useless. The result was no longer competition but rather taking turns.

found this

Adding a kilo at the extreme rear of the bike could damp out chatter, because the moment of inertia increases by the square of distance, so a small weight that far from the centre of the motorcycle would have a significant effect.
Marlboro Team Roberts learned this by coincidence in the late 1980s, during the very early years of datalogging. Wayne Rainey’s Yamaha YZR500 was equipped with a datalogger during practice, but not during the race, because it weighed a significant amount – about two kilos. Rainey would have a great two days of practice and go to bed full of confidence on Saturday night, while his mechanics removed the datalogger. The race would be completely different, Rainey would struggle with chatter, get beaten and return to his pit baffled. At first his crew thought he had got a bad tyre, but after three races they realised what was going on. The datalogger was housed in the set hump and cured any chatter.

There is scuttle butt that this is what the Dukes have on the rear of the latest motogp bike
the Rainey era anti chatter device
http://www.motorsportmagazine.com/op...versus-marquez

plus a thesis on chatter
https://www.researchgate.net/publica...ng_motorcycles

http://www.cycleworld.com/2012/04/26...hatter-chatter
Modern moto gp bikes have to be changed to suit the control tire some bikes will chatter more than others as will chatter will effect some riders yet not others its a dynamic interaction

[F5 Dave]

Have to replace my copy of Sinclair book. I'm troubled by guilt, blah blah blah, rightful owner, blah blah you know the sort of thing.

[guyhockley]

[QUOTE=Grumph;
It was most interesting to discover why the carbon fiber frames didn't work also...[/QUOTE]

It would be!

Please?