Race chassis

[Kickaha]

Just completing BOB is becoming rather hard.

If you ride slower you don't have to concentrate as hard and it is a bit easier, haven't seen the results from BOB were they ever posted up anywhere?

Anyway I rode Brens TZR/FXR in the FXR cup a few years back,after the Timaru rounds we found a partially broken front engine mount so I took it off and got it welded it up

The next round was Ruapuna and with the only change being the front mount fixed it vibrated like a bastard, bad enough that my hands went numb/pins and needles
I made a pretty basic rubber mount just for the head mount which made it better but it still wasn't great

I think that motor was minus balance shaft

[husaberg]

(head steady's) who's on the what now? Do you mean steering damper? Well the engine that has the balance shaft still is a little smoother but the one without does vibrate a little. I will sold mount it to start with and see what happens. If it vibrates bad I will try rubber mounting. I hate vibration, it can really put you off the fun stuff.

Well I did catch Dave at the end of the race to put a lap on him. But I am sure he wasn't standing still. I like the hoogie vid as well shows my little crash rather well. This year I might need to get fit. Just completing BOB is becoming rather hard.

Head steady or head stay is what links the cylinder head to the frame. A conventional stressed engine doesn't have one. but they are real not a steering damper oh the young
But how the top engine mount is located can have a surprising effect on engine vibes.
This mainly applies to cradle frames (or frames with cradles) of course .
Are you were going to fabricate a cradle.Hense the no weld idea.



http://p1.bikepics.com/2011\09\19\bikepics-2274763-full.jpg

[richban]

The next round was Ruapuna and with the only change being the front mount fixed it vibrated like a bastard, bad enough that my hands went numb/pins and needles
I made a pretty basic rubber mount just for the head mount which made it better but it still wasn't great

I think that motor was minus balance shaft

Yeah I have seen and ridden a few bikes with the shaft pulled out. Not so good. My crank is supposed to be balance to compensate for that. It doesn't vibrate near as much as others. Nothing through the hands and feet. It might not be an issue.

[richban]

Head steay or stay a conventioional stessed engine doesn't have one but they are real not a steering damper oh the young

Young at 40 for sure. With all the wisdom you have, you must be ancient. I must say your magazine collection must be an impressive site. Some real gold in there.

[husaberg]

Young at 40 for sure. With all the wisdom you have, you must be ancient. I must say your magazine collection must be an impressive site. Some real gold in there.

You beat me with the editing there i took that out. PS put the young back in because gee 40 that's real old, hows your arthritis?
but have a look in a minute at a head steady.

On some of the old bike they were (allegedly) a necessity for good handling as well .

PS i am 38 my collection is nothing on my old mans.
Not must wisdom here just regurgitation still learning but a good memory for useless facts.where-as Grumph is a wise one.
Much like Yoda only taller with more swearing.

[Brian d marge]

Why , are my old tutors words ringing in my head when I read all this , Free-body, free-body,,free-body diagram, even those PB mag , more money than sense imho. ( those early CBRS were 85 Bhp , possibly HP cant remember now ) , he spent HOW MUCH , even then that was a lot .

As for vibration in frames , the engine and frame you could consider a "package" if you change the design , you most likely will have to change the balance factor or flywheel(s) weight ( clutch is also a flywheel)

From memory you have to dissapate the enerfy as quickly as possible , before it gets to the points of contact. You can do this by , increasing the mass , density , load path or by reducing the energy so slapping a engine that was desiged for a steel frame into an alloy frame will vibrate more untill you " bleed off " some of that energy , by either , rebalancing it ( sorry dont know off head which way heavier or lighter , have a gut feeling it might be heavier in order for the flywheel to store energy ,,someone can coeerect me ) or by modifying the engine mounts

For you me and the rest, steel is a lovely material , except that Those twin spar frames alloy frame , an old mod ( still done know???) was to house the fuel inside , thus negating the need for a gas tank in short races,

Stephen

The above is from memory , a old and very much abused one, so ......there ! , now off to drink beer and watch , the Edwardian farm , a great tv series!!1

[Grumph]

If I was a wise one I'd have money.....

Head steadies are a whole strange subject...in theory you can use the motor to triangulate the frame using lower mounts and a head mount. in days of old when motors were mounted in plates bolted into the frame this could make quite a difference, both to vibes and to frame stiffness. As frames have got stiffer and motors have been mounted more directly into them - frequently now, no plates at all - the need for head steadies has reduced. In some cases now it can actually increase the perceived vibration.
Do you know what the balance factor is on your FXR without the balance shaft ? i seem to remember talking to your bro at the BOB about it - I've rebalanced a few cranks.....and he knew that.

[richban]

If I was a wise one I'd have money.....
Do you know what the balance factor is on your FXR without the balance shaft ? i seem to remember talking to your bro at the BOB about it - I've rebalanced a few cranks.....and he knew that.

Don't know the balance factor. But can find out. Interesting stuff. I think it will be easy enough to get it mounted solid and see what happens. I am hoping the NSR will all be lighter and better than the FXR when complete. But a part of me thinks it will take a lot of development to get as good as the FXR is now. I have the FXR handling quite well now but the front end flex is quite substantial. It dose give a lot of feedback from the front but I am having trouble getting heat into the front tyre. Could the flex have anything to do with that? Or just bad suspension setup? Or pressure or all of the above.

[Bert]

..... I have the FXR handling quite well now but the front end flex is quite substantial. It dose give a lot of feedback from the front but I am having trouble getting heat into the front tyre. Could the flex have anything to do with that? Or just bad suspension setup? Or pressure or all of the above.

could be the 100kgs sitting on top of it

The reality is the the FXR was never made for the kind of abuse that you lot are giving them (in saying that it is a lot better than most); the NSR should feel amazing from the start. get back to your shed and get it finished for the GP.

[Moooools]

I have mounted 3 engines into aluminium frames now, always two lower rear mounts and a head steady to the back of the head, from a crossmember added across the frame.
Never had any issue with vibration. Having said that they were all untouched balancing wise.

I plan to do the same thing with project NSR/project Rich is doing it so I should too.

My TZR Chassis (that my brother is stealing off me) was very tall, and was nice as around Kaitoke.
But around Mt Welly it is a bit of a handful especially when it comes to the bumpy sections. The plan with the NSR will be to get the centre of gravity lower along with the seating position to get a bit more feel for what the bike is doing. The TZR feels a bit distant.

So the plan is for an MC21 Frame and swing arm with an CBR600F3 shock (or and MC21sp shock if I can find one) with my ZXR front end and my RS125 wheels. Just need a shock and seat unit to start the build.

All in good time. No really rush just yet. I might even let you finish first Rich.

[Brian d marge]

If I was a wise one I'd have money.....

Head steadies are a whole strange subject...in theory you can use the motor to triangulate the frame using lower mounts and a head mount. in days of old when motors were mounted in plates bolted into the frame this could make quite a difference, both to vibes and to frame stiffness. As frames have got stiffer and motors have been mounted more directly into them - frequently now, no plates at all - the need for head steadies has reduced. In some cases now it can actually increase the perceived vibration.
Do you know what the balance factor is on your FXR without the balance shaft ? i seem to remember talking to your bro at the BOB about it - I've rebalanced a few cranks.....and he knew that.

I'm I on every body's ignore list , or one can be bothered reading or is this a select club?
think about the manufacturing process and a head steady , if you can eliminate it .....it will?? ?

also , chucking a small motor designed to a large frame will do what?

back to Edwardian garden .....

Stephen

[husaberg]

I'm I on every body's ignore list , or one can be bothered reading or is this a select club?

I enjoy your posts

think about the manufacturing process and a head steady , if you can eliminate it .....it will?? ?

simplify it then redesign it to elininate it but some of the motors used for buckets were not designed for hanging from thier heads or designed with more attachment points.

also , chucking a small motor designed to a large frame will do what?

F-ing up the weight distribution. Amongst other things is possible

[Rick 52]

I enjoy your posts

This is a great thread , lots of good info ..all interesting stuff cheers fellas !

[Grumph]

I'm I on every body's ignore list , or one can be bothered reading or is this a select club?
think about the manufacturing process and a head steady , if you can eliminate it .....it will?? ?

also , chucking a small motor designed to a large frame will do what?

back to Edwardian garden .....

Stephen

Stephen.....you've gone a bit too inscrutable...spell out exactly what you're getting at please. Motor swapping from one frame type to another has been done since the Hildebrand and Wolfmuller first came on the market. The practicalities of it mean that until it's done and tested the average Joe won't know if the vibes are better or worse until he tries it. If you have access to massive computer capacity and the time by all means simulate it for us.....in the meantime, adjusting the balance factor until the PERCEIVED vibration is acceptable works for me....
Tying a motor in to a frame with a larger than normal number of mounts will all else being equal raise the resonant frequency of the whole thing...whether this actually helps reduce perceived vibration or the opposite depends on many things, most of which the builder can't change...One guy here with a BSA twin read some theory on the net and turned out with what looked like an Americas Cup keel on the underside of his motor - reckoned it was smoother....but he would say that wouldn't he.

[richban]

Tying a motor in to a frame with a larger than normal number of mounts will all else being equal raise the resonant frequency of the whole thing...

OK best guess. I have 2 choices with the front head mount. Front or rear of the head. Bigger triangle or Smaller triangle? I was thinking bigger and using the exhaust side mount figuring bigger triangle will distribute any vibe over greater area. But hey I have know clue really. Rear mount could come straight from the frame cross member and would be a little easier. Thinking out loud now. Maybe the small mounting config might be better as the motor its self might absorb more vibration. Not sure but we will see. I will post some pic's next week when I start on the mounts. I am sure the length of the mounts and design will make a big difference. Over thinking maybe.