Improving Chassis Stiffness by Foam Injection
Improving Chassis Stiffness by Foam Injection
(OP)
Hi
I am trying to wade through some hype on a product called foam-seal which some people are saying increases chassis stiffness by a huge amount. (i've heard claims of up too 300% in some cases!!)
The product is a 2 part polyurethane foam which is injected into the rails, expands, fills all the voids then hardens. Even the conservative estimate was I believe 30% more stiffness for the lowest density foam (2lbs/ft^3).
I understand the principles behind a foam core in a sandwich laminate and I suppose it works the same way, but I have a few reservations.
First I would think the foam must adhere completely to all sides of the walls for it to be any benefit and I am wondering how the foam can do this in metal that has been enclosed for possibly years and is not prepped?
Second if used in say 2"x6" rect. tube steel with a wall thickness of 0.125" and a length of 10 feet can any usefull stiffness increase be expected assuming good adhesion on all sides?
Thanks for any help you can offer.
I am trying to wade through some hype on a product called foam-seal which some people are saying increases chassis stiffness by a huge amount. (i've heard claims of up too 300% in some cases!!)
The product is a 2 part polyurethane foam which is injected into the rails, expands, fills all the voids then hardens. Even the conservative estimate was I believe 30% more stiffness for the lowest density foam (2lbs/ft^3).
I understand the principles behind a foam core in a sandwich laminate and I suppose it works the same way, but I have a few reservations.
First I would think the foam must adhere completely to all sides of the walls for it to be any benefit and I am wondering how the foam can do this in metal that has been enclosed for possibly years and is not prepped?
Second if used in say 2"x6" rect. tube steel with a wall thickness of 0.125" and a length of 10 feet can any usefull stiffness increase be expected assuming good adhesion on all sides?
Thanks for any help you can offer.





RE: Improving Chassis Stiffness by Foam Injection
Dan - Owner

http://www.Hi-TecDesigns.com
RE: Improving Chassis Stiffness by Foam Injection
Maybe they meant fill in everything outside the tubes.
RE: Improving Chassis Stiffness by Foam Injection
RE: Improving Chassis Stiffness by Foam Injection
If the frame was aluminium that was microns thick, and therefore exceptionally flimsy, then the foam would have a significant increase, however if the frame was heavy wall chrome molly tubing, I doubt the increase would be measurable.
Polyurethanes are very good adhesives and stick well to most metals. Some generate significant pressure as the foam expands on cure. This pressure increases stiffness just like air in tyre, and like air in the tyre does not need a bond to get some (but not optimum) effect.
Regards
eng-tips, by professional engineers for professional engineers
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RE: Improving Chassis Stiffness by Foam Injection
Have you ever seen what happens to a couple of vaccum packed magazines? They become as stiff as a board. The foam deal maybe like doing that in reverse.
RE: Improving Chassis Stiffness by Foam Injection
-b
RE: Improving Chassis Stiffness by Foam Injection
-b
RE: Improving Chassis Stiffness by Foam Injection
Ford Australia used a foam filling in one of their production cars to help get through crash tests not long ago.
Perhaps an email will help give you some clarification on the points you era talking about.
Apart from reading about it in a magazine I have no other knowledge of the "how to" and the results.
Pete.
RE: Improving Chassis Stiffness by Foam Injection
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.
RE: Improving Chassis Stiffness by Foam Injection
So this process will do nothing except maybe some noise reduction.
Thanks again for the help.
RE: Improving Chassis Stiffness by Foam Injection
Two large flat sheets of any material will be greatly stiffened by a foam core. But there are other ways of stiffening such as ribs, curvature, corregation, etc. A tube is already stiffened by its shape and adding foam will have minimal effect in mast cases.
Sheet metal can be stamped to shape very economically and therefore that is the most common method of forming stiff structures.
RE: Improving Chassis Stiffness by Foam Injection
compositepro
I was talking about the specific case which I mentioned in my original question i.e. rect. tube steel 2"x6"x10' with 1/8th wall. and as you mentioned later in your post a tube will not really benefit.
RE: Improving Chassis Stiffness by Foam Injection
I believe Toyota and Nissan have been using the process for a while now in their luxury cars.
RE: Improving Chassis Stiffness by Foam Injection
If your spotwelding was amazingly bad it might help to improve the integrity of the spotwelds.
It will certainly reduce panting of the skins of box sections. This could increase the overall stiffness of the car.
It will prevent transmission of noise along the tube.
Cheers
Greg Locock
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: Improving Chassis Stiffness by Foam Injection
Dan - Owner

http://www.Hi-TecDesigns.com
RE: Improving Chassis Stiffness by Foam Injection
Cheers
Greg Locock
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.