Chassis stiffening through foam injection

[NoHachi]

Hiya,

We've all heard of the cheap way of stiffening a chassis through foam injection into boxsections of the unibody. Moto's car springs to mind. Sounds like a great solution for a street car where you don't want to have a rollcage threatening your coconut in a crash (rollcage without a helmet = coconut + steel basebal bat)
Have no experience on this matter, but have been interested in it for quite a while. Found some links that make for interesting reading. With all the new guys popping up on the forum, I hope that maybe some people will share any experiences that they might have.

http://www.sportcompactcarweb.com/projec...zx_part_5/
http://www.britishcarforum.com/bcforum/u...ain/26993/
http://www.marinefoam.com/liquid-sprayin-foam.html
http://www.miata.net/products/chassis/bellco.html
http://forums2.freshalloy.com/showthread.php?t=162693

*Edit: I'm adding any interesting links that others post to the list above. That way we have an easy list for reference. keep em coming guys!

[NickBW]

I've been looking into this as well. Only downside, other then adding abit of weight(which depends on how much and which grade you use) and that it is impossible to repair the foamed area if it ever gets damaged from a wreck. but at the same time, even with out the foam if the car got into a wreck that was bad enough to screw up the area that was reinforced by the foam I would ASSuME the chassis would be a near lost cause anyway.
Saw an interesting thread of some folks doing this to a nissan 240sx(200sx/silvia chassis.. what ever they call them over in europe) and they have some interesting tech that I found... rather interesting. lol
click

I'd love to see a more detailed account to someone doing this with an 86 with before/after rigidity numbers and weight.

[Lipinhu]

Quote:Structural foam, in the 2 lb per cubic foot density that we used, can stiffen chassis members up to 40 percent.

Higher densities of foam can increase stiffness by up to 300 percent

Who wants roolbars anyway...?

Tell me something, i´ll take our cars as an example once they rust everywhere, even in MAJOR STRUCTURAL MEMBERS, if some of these major structural members are foam filled, it can prevent rust too, making no room for the water and air exposure. Could this be correct?

I've been told that this foam filling can be quite dangerous, i dont know if it the case of this specific aplication nor the propeties os that specific foam, that when we are filling the members the foam tends to expand, and if the foam doesnt dry uniformly leaving no room to expand, it will brake some spot welds. But dono if its true and never worked with polyurethane foam in any kind of aplication.

Iteresting thread

[assassin10000]

Nice.

Andrew

[Ivan141]

Personally, I fear foam might accelerate rust in places that are hard to get too. Any moisture that gets in there will get trapped by the foam. Now see what a mess you get when you try to repair your chassis once it's filled with foam. On the other hand it is a nice increase in stiffness.

[assassin10000]

Ivan141 Wrote:Personally, I fear foam might accelerate rust in places that are hard to get too. Any moisture that gets in there will get trapped by the foam. Now see what a mess you get when you try to repair your chassis once it's filled with foam. On the other hand it is a nice increase in stiffness.

FOAM = good for track cars.

Not good for daily drivers, especially in wet/damp area's.

Andrew

[NickBW]

I believe ford uses foam in on certain spots on a few vehicles such as navagators and expedition and IIRC some BMW's make use of it as well.

Few of my concerns:
1)Although I've heard the foam(or at least the brand I looked into) has stuff in it that prevents corrosion I'd be worried about blocking drain holes. I've seen this come up a few times in the miata/mx5 camp.
2)I have "heard" with out any real confirmed proof, that many of these structural foams can or will break down with in a handfull of years. I'd love to see this confirm or denied though.
3)I've heard of some foams(great stuff ??) expand too much and can actually damage the chassis.
4)Perhaps not so much as a mark against using a foam, but a warning. Make sure the chassis is perfectly square before applying. I would assume this is easier said then done givin the fact that our cars have lived thru twenty years of life, bumpy roads, moisture and a few bangs here and there and they never were the most rugged chassis's on the block.

[robokill]

Hey, my dad used this technique when he was young. Seems to be able to really stiffen the chassis. If done correctly no air will be left and without air and water no rust. Its a 2 componment substance which hardens.

Putting it on the correct way is the hardest. It isn't bad for daily cars you just need to do it really well.


Nohachi i want to do the main frame unde the hachi with foam the rest i will cage also because of roll safety. I am still looking into some examples because of the wheigt

[NoHachi]

Weight is almost negligeable...it can never weigh more then the can it came out of. If you use the hard stuff, maybe 20kg as a maximum for an entire car.