Structural Foam for chassis stiffening
Not seeing much to be scared of guys.
Few if any disadvantages of Structural foam if used with a little forethought.
If it provides ZERO added torsional rigidity and just quiets the whole car, would it still be a worthless effort? Don't guys wind up spending much more time & money just on Dynamat.
Seriously, if torque boxes provide some benefit, so too should foaming the rocker joints.
If spending countless days disassembling the car, cleaning out all the seam sealer and adding 50lb of weld wire makes you feel better, that's awesome, but I doubt that will ever happen.
I'll be seeing if I can kill 2 birds with 1 stone.
Yes, if there's no chassis stiffening IMHO it's a worthless effort to go through the trouble to use structural foam. Dynamat and similar products are easy to install, we know they work, and you're not dealing with any exotic chemicals or foams that could accidentally blow the joints of your car apart if you get your amounts and expansion rates wrong. I can't hear anything over my exhaust, stereo, and tinnitus anyway.
As for no disadvantages, how do you figure? How about
-added unnecessary weight to the car when it doesn't work
-potential for separating spot welds and deforming joints if expansion rates/volumes aren't controlled properly
-moisture trapping and drainage control issues, resulting in rust damage
-access holes added to closed structures for injection and foam control
-unknown longevity for structural improvement
-no external visual clues to indicate proper installation/adhesion
Once again, you have some test results that show that the structural foam can work if used properly (and it can!), but you aren't going to replicate the process behind those tests (extensive FEA). So, why do you think your results will be the same if your process isn't going to be? Foaming the rocker joints will only add benefit if the foam is properly applied, adheres, cures, etc. There's no doubt about whether or not torque boxes work, that's why the factory used them, they did the engineering. But unlike the foam you can look right at them and see if they're properly installed, and even fix them if they aren't. Squirting a bunch of foam in the joints is great, but once it's done you'll have no way to look at it and see if it adhered properly. You'd have to test before and after to see if there's any improvement, and then compare your results to the results in those papers to see if you got the results you anticipated. And if it didn't work, then what? As it is you're going to have to drill injection points into some of these joints, and figure out how to contain the foam to the areas you want it. That balloon trick is neat and all, but it will still take drilling more access holes. If the foam doesn't work, it's still in the chassis. And I bet some of it is probably flammable, so, if the foam doesn't work you're probably not going to go back and stitch weld those joints either.
One of the papers talks about adding 25 lbs to the chassis, and they got better chassis results with denser foam they just maximized for improvement vs weight so the lighter densities were used. Yeah, I'd rather add 50 lbs of welding wire knowing it'll work than add 25 lbs of foam and have no idea if it will or not. Maybe welding the chassis isn't as interesting or exotic as using structural foam, but everyone knows welding works in this application.
There is no doubt that structural foam works in the correct environment. That environment includes applications, chemicals, equipment and possibly curing ovens for curing that many of us don't have access too.
The papers don't mention specifically what chemicals or what blowing agents are being used, and how those chemicals are being applied, controlled and cured. Many of the tradenames are likely highly proprietary and not available for purchase without license.
I mentioned the cost aspect of this as well. I know many of these chemicals are quite expensive and they are not sold by the pint at the hardware store. You might even need a hazardous use permit to obtain them. Isocyanate is not something I would consider benign. How would you apply them and what is the cost of the equipment?
The papers do mention the long term effectiveness of the testing needs to be confirmed. Not sure that I would want to subject my little coupe to those rigors.
Just how strong does your car need to be? There are 8 second Barracudas and Darts that don't have the foam - at least I don't think they do. Autocross isn't my scene, but I don't know those guys use it either - or how much it would benefit them.
If strength and weight savings are your goal - there are more effective ways to achieve that on an A Body with more efficiency.
When I hear about foam in a car, I think of an amphicar. Although if someone wants to lend me their new Challenger or Ram truck, I will happily return it at the end of summer.
:steering:
Exactly! :thumbsup:
