Foam cuts down vibration?

[USMC 500]

There is this foam in a can that once sprayed it expands and hardens.  Electricians use it to fill holes in studs that they have run wiring through in construction projects.  I hope everyone knows what I'm talking about .  Anyways, (in an old timers acent) "back in my good ol' day of racin'" I used to spray this foam into the frame of my KX500 and try to completely fill the frame.  Once it dryed and hardened I would cut the excess off where ever it came out and retap all bolt holes in the frame.  This action would cut down on the notorious 500cc 2-stroke vibration by a HUGE margine.  I would also install street bike bar end weights which would also cut down vibration at the handle bar.  I dont really understand the physics of this all but it worked great and it would cut down the rider fatiuge factor.  Has anyone heard of these methods or tried them?  Or am I just a nutcase that has landed on his head a few times too many?

[Dutch-K5 Fan]

You can buy inserts for the handelbars to reduce vibration.
I believ that because of the weight the bars can't(or at least a lot less) vibrate.

Construction foam( Purschuim in dutch):
Like on a guitar the frame is a resonance-box. With the foam you block the air to
to move and vibrate. And so elimenate resonance of the frame.

Sounds good to do.

Dutch

[bigbellybob]

i wonder how it would effect frame rigidity. i know mx frames are designed to have a little flex. now is this flex good or bad for handling? uni-body race cars fill the uni-frame like rails with some kind of expanding foam to stiffen the body witch helps the handling of the car. if a stiffer frame on a mx bike is better for handling, i would think the foam would also help the handling of the bike.

[Dutch-K5 Fan]

I think that the olderbike were rigid and benafit from les flex.
Remenber the first alu honda's and is 20 inch wheels. They were to rigid
and in mx bikes you need some i gues.
Sould construction foam be so strong that it makes the frame stronger.
Maybe in those race cars they use a stronger type of foam.
Don't know were you get the info from, but maybe you could find that out??


Dutch

[bigbellybob]

a link to look at i first seen it on a speed channel show. and yes the do use a application specific foam

scroll down to Foam-Filling the Chassis

http://www.sportcompactcarweb.com/projectcars/0006scc_project_nissan_300zx_part_5/index.html

[maddoggy]

the foam filled frame sounds like a reasonable idea, but stewart pointed out in a different thread that the crank not being in clock/timed or properly balanced is where the majority of k5 vibration comes from. i think i would chase the source of the vibes before i tried foam filling the frame. bigbellybob made a good point that the frames are designed to have a specific amount of flex, if you don't allow the flex/vibrations to go throughout the frame it will concentrate near the source and probably start breaking welds or the smaller tubes on the frame under the engine. no facts here just my opinion.   MADDOGGY

[Rd]

You can get the closed cell structural foam from good boating supply companies. If I remember correctly it comes in 3 differant densities 1lb,2lb and 4lb, The 4lb being the strongest. I have used the 2lb on some boating projects and believe it would be very tricky to get into a frame before it kicked and started getting rigid. You would probably be better off using a closed cell marine foam, because it is not supposed to absorb water like an open cell foam. The 4lb is some pretty rigid stuff.

[Good]

Interesting topic.

I too remember the CR250s being too rigid out of the box and I think it was McGrath who didn't like them and wouldn't ride them at first.

But, would this expanding foam add rigidity, or just dampen vibration?  Not talking the marine stuff, just simple expanding foam found at wally-world.  I wouldn't think it would make the steel frames as rigid as their aluminum counterparts, but the vibration issue might be worth looking into.  Great topic.

In the car stereo world, sound deadening is achieved by adding mass to door panels, etc.  It would be cool to inject some of that stuff into the frames.  The problem with that is mass generally = weight...

[GDubb]

I too remember the CR250s being too rigid out of the box and I think it was McGrath who didn't like them and wouldn't ride them at first.

I remember that too... he was having the new engines swapped into a modified '96 frame.


-G

[Speedway73]

The stuff you're talking about is called Great Stuff.

[USMC 500]

Interesting topic.

I too remember the CR250s being too rigid out of the box and I think it was McGrath who didn't like them and wouldn't ride them at first.

But, would this expanding foam add rigidity, or just dampen vibration?  Not talking the marine stuff, just simple expanding foam found at wally-world.  I wouldn't think it would make the steel frames as rigid as their aluminum counterparts, but the vibration issue might be worth looking into.  Great topic.

In the car stereo world, sound deadening is achieved by adding mass to door panels, etc.  It would be cool to inject some of that stuff into the frames.  The problem with that is mass generally = weight...

Cool I started a bitchen topic!....hooray for me   LOLLL!  I also have a 1997 (first year for aluminum frame) CR250 and yes, its rigidity is equal to a 2 year old loaf of french bread......very little (none) flex.

[Good]

Maybe AJ will chime in here, but I wonder what the best years were for the 500 swaps in those frames.  It is possible that that rigidity would be tamed or vice-versa with the 5s power.  Or might make it a horrible ride.

I always thought, though, that I'd like a stiffer ride.  Kinda like riding a meat cleaver vs one of those old floppy wood saws that hillbillies make music with. You don't see surgeons working with those things, nowadays anyway.

You know, once the ergos fit, it's like a scalpel, or something...  But, I'm faster on my '00 KX5 than I was on my '99 CR250 in all terrain.  My 5 just out-handles it, and maybe there was something wrong with my forks, but it's true...

That makes me wonder how that '09KX5AF handles...  I wanna ride one, BAD!!!

[Dutch-K5 Fan]

I too remember the CR250s being too rigid out of the box and I think it was McGrath who didn't like them and wouldn't ride them at first.

I remember that too... he was having the new engines swapped into a modified '96 frame.


-G

Mc Grath rode the 93 frame when he was at honda. Thats wy he went to Yamaha because he had
to ride the alu frame.

A bike most flex a bid, even road racers use flex in there frames. It's a bit of the bikes suspension when it's
on his side an rides over bumps.

And the foam idea is for reducing the vibes.

Dutch

[dsrtrider]

I read old articles where team green would run rubber bar snakes, weighted bar ends, carefully tighten bolts, and balance crank for their vibration reduction strategy

[USMC 500]

I too remember the CR250s being too rigid out of the box and I think it was McGrath who didn't like them and wouldn't ride them at first.

I remember that too... he was having the new engines swapped into a modified '96 frame.


-G

Mc Grath rode the 93 frame when he was at honda. Thats wy he went to Yamaha because he had
to ride the alu frame.

A bike most flex a bid, even road racers use flex in there frames. It's a bit of the bikes suspension when it's
on his side an rides over bumps.

And the foam idea is for reducing the vibes.

Dutch

History lesson time .............


Actually McGrath rode his 1993 CR250 in 93, 94, 95, and in 96 while Jeff Stanton, Steve Lamson, and Doug Henry (get well soon) rode the bike of the year.  Jeremy said that he liked the egronomics of his 1993 frame.  Then came the 1997 CR250 (same bike I still have ) which by coincidence (yeah right) was heavily based on the 1993 frame geometry.  The first year of the aluminum frame was super rigid and McGrath tried all types of suspension settings while testing the bike to get it to his standards......didn't happen.  So for the next year Jeremy jumped ship to Suzuki for personal reasons (he stated that the bike had nothing to do with it  ) and lost the SX title that year to our very own Jeff "Fro Daddy" Emig on the mighty KX250.  I guess the Suzuki was not what it was today because for 98 Jeremy jumped ship again to Yamaha.  Personaly I would have loved to see the kind of madness that a 500cc Supercross would have caused.