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.

I say go for it and tell us if you notice any differences.

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.

myduster360 said:

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.

Click to expand...

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.

1SavCuda said:

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.

Click to expand...

Exactly!

myduster360 said:

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.

Click to expand...

50lbs of weld wire...thats funny.

At 30 lbs/cuft for the foam your adding at least 50 lbs in the rockers alone. The way your talking it sounds like it would be a few hundred pounds of foam before it was all said and done.
Plus as I said before I believe you'd have to have pristine metal to get proper adhesion of the foam so you'd be taking the car down even further to get it to that point. Would be a complete waste of time otherwise.
Not saying it has no benifits, but I dont see the return on time/money invested on a 40 year old car.

I'll stick with welding in some 2x3 and tubes to get rigidity.

LOL,,,,,,some of these "yeah but" and "what if" excuses are pretty laughable even if I didn't have a BS in mechanical engineering.

Total cost is currently estimated to be ~$150.
That'll get me total cured volume ~2ft3 of the 8lb/ft3 density foam.

I'll post the % improvement in torsional rigidity.

You ask for opinions then call them laughable. Good luck. BS in schooling or not.

Absolutely,,,,,I appreciate everyone's input but can't contain my eye rolls & face palms after reading from the misinformed and self-identified "experts" preaching fire and brimstone,,, lol.

Moving on:

This method of quantifing torsional rigidity seems reasonable.

1. Level car on 4 stands with tires off
2. Add Ballast to left rear corner to allow removing stand from right front.
3. Measure chassis height at right front and zero dial indicator
4. Add known mass to unsupported rf (F) and record deflection(d).
5. Measure distance to nearest side stand(L)

Torsional rigidity is founder by finding the torque applied to the chassis and dividing the angular deflection.

K^2 = F × L/tan(d/L)

Repeat test for the other side.

Or you could drive the car into a solid steel wall at 50 MPH???

Sorry....couldn't help myself


Gotta keep things light or it's no fun!!!

Treblig

Interesting concept. Have you ever chatted with a body shop tech about the inner structure foam used now days? What a pain it is to work with. Don't get weld or open flame close to it. Nasty smoke when it lights on fire. It's also tough to remove so repairs can be made.

The original question was "have you ever thought about it."
The answer seems to be yes, many people have thought about it. In reality you have done more than thought about it and this thread seems to have convinced you to proceed.
More power (mo' par ?) to you for being creative in your approach. Far be it for me to criticize another's ideas and concepts. I just simply stated my experience of the product and its application.
By all means post your results and procedures including your list of materials and process. Please let us know the results after a few years to see if it's a viable, long term and cost effective option.
Good luck.

Test #1 RESULTS:



I gotta stop drinking before lunch!!!

Treblig

Much better results with TEST #2:

What information is available regarding out gassing?

MOA said:

What information is available regarding out gassing?

Click to expand...

30 parts foam to 5 parts GasEx.

This is just my 2 cents and someone else might have already made the statements but...i didn t read this whole thing. I work on cars at the bodyshop everyday. Been seeing a lot of pickups with foam in the wheelwells on the bedsides rustin out right where the foam is. As far as structural foam goes..look at the 2009-now rams. Rockers are completely filled with it and the rockers are so far the worst spot for rust on them. Ruating from the inside out just like thebedsides. Holding moisture is what i m getting at.
On the other hand. If u can properly treat the metal on the backsides of these areas...i think its a great idea
Catch 22

myduster360 said:

LOL,,,,,,some of these "yeah but" and "what if" excuses are pretty laughable even if I didn't have a BS in mechanical engineering.

Total cost is currently estimated to be ~$150.
That'll get me total cured volume ~2ft3 of the 8lb/ft3 density foam.

I'll post the % improvement in torsional rigidity.

Click to expand...

myduster360 said:

Absolutely,,,,,I appreciate everyone's input but can't contain my eye rolls & face palms after reading from the misinformed and self-identified "experts" preaching fire and brimstone,,, lol.

Moving on:

This method of quantifing torsional rigidity seems reasonable.

1. Level car on 4 stands with tires off
2. Add Ballast to left rear corner to allow removing stand from right front.
3. Measure chassis height at right front and zero dial indicator
4. Add known mass to unsupported rf (F) and record deflection(d).
5. Measure distance to nearest side stand(L)

Torsional rigidity is founder by finding the torque applied to the chassis and dividing the angular deflection.

K^2 = F × L/tan(d/L)

Repeat test for the other side.

Click to expand...

Hey whatever, your car. You obviously aren't all that familiar with the product you're planning to use since you're calling people names rather than posting a technical response based on the material properties of the foam. I mean, if there's a reason backed up by material properties why you're not worried about surface adhesion to 40+ year old surface rusted metal and voids that contain drains and built up dirt then by all means share. Instead you just say you're not worried about it and our concerns are laughable? Ok, sure. Your degree in engineering doesn't change the fact that you aren't taking into account that you're not replicating the papers you're using to back up your idea. I didn't even need my BS in aerospace engineering to figure that out. It's right in the papers. The adhesion properties are discussed and pointed out as being the reason why the real life testing didn't match the FEA models in two of the three papers you posted, so the engineers that are familiar with the product and it's application, and did the actual testing, thought it was a worthwhile consideration. But what do they know right?

And yeah, you're not the only one that's seen a torsional rigidity equation. Actually testing the car appropriately to use that equation properly is a different story. Your method will work, but I'm sure you're aware that a single test won't provide you with a margin of error, making it a pretty useless test. You're not going to see massive amounts of deflection measuring the car with the method you're suggesting, so even a small margin in measurement will change your percentages pretty significantly. It's not a bad way to test the torsional resistance if you lack better equipment, but it's not as accurate as other methods either. You'd have to repeat the same measurement at least 10 or so times to give a decent margin of error, assuming the measurements are close.

I'm not trying to preach "fire and brimstone", but your application is different and has issues that need to be addressed before you can just say it's gonna work great. Ignoring those issues could mean the whole operation is useless at best, wasted effort with an added disadvantage of not being able to weld on those areas later without catching the whole mess on fire.

But go ahead, by all means. If you're going to bother testing make sure you get enough data to do some basic margin of error calculations though, otherwise it's just a waste of time. Kind of like the USCT and XV videos. They're neat and all and they show that something happened, but they're not particularly useful for actual data. And unless you test a car that's had frame connectors and torque boxes added to compare to yours you won't really show that adding structural foam is the better way to go, just that it does something. But even the bolt in MP frame connectors do something, so the bar set is pretty low.

Most of the late models I've been into, and it's been many, in addition to the foam there is also plastic gussets in place whether it's in a sail panel or rocker adding some kind of mechanical advantage. The adhesive properties of the foam make them a bear to get loose when replacing panels. I don't see a retrofit being worthwhile other then sound deadening. The stuff will make a tin can sound solid.

72bluNblu said:

Hey whatever, your car. You obviously aren't all that familiar with the product you're planning to use since you're calling people names rather than posting a technical response based on the material properties of the foam. I mean, if there's a reason backed up by material properties why you're not worried about surface adhesion to 40+ year old surface rusted metal and voids that contain drains and built up dirt then by all means share. Instead you just say you're not worried about it and our concerns are laughable? Ok, sure. Your degree in engineering doesn't change the fact that you aren't taking into account that you're not replicating the papers you're using to back up your idea. I didn't even need my BS in aerospace engineering to figure that out. It's right in the papers. The adhesion properties are discussed and pointed out as being the reason why the real life testing didn't match the FEA models in two of the three papers you posted, so the engineers that are familiar with the product and it's application, and did the actual testing, thought it was a worthwhile consideration. But what do they know right?

And yeah, you're not the only one that's seen a torsional rigidity equation. Actually testing the car appropriately to use that equation properly is a different story. Your method will work, but I'm sure you're aware that a single test won't provide you with a margin of error, making it a pretty useless test. You're not going to see massive amounts of deflection measuring the car with the method you're suggesting, so even a small margin in measurement will change your percentages pretty significantly. It's not a bad way to test the torsional resistance if you lack better equipment, but it's not as accurate as other methods either. You'd have to repeat the same measurement at least 10 or so times to give a decent margin of error, assuming the measurements are close.

I'm not trying to preach "fire and brimstone", but your application is different and has issues that need to be addressed before you can just say it's gonna work great. Ignoring those issues could mean the whole operation is useless at best, wasted effort with an added disadvantage of not being able to weld on those areas later without catching the whole mess on fire.

But go ahead, by all means. If you're going to bother testing make sure you get enough data to do some basic margin of error calculations though, otherwise it's just a waste of time. Kind of like the USCT and XV videos. They're neat and all and they show that something happened, but they're not particularly useful for actual data. And unless you test a car that's had frame connectors and torque boxes added to compare to yours you won't really show that adding structural foam is the better way to go, just that it does something. But even the bolt in MP frame connectors do something, so the bar set is pretty low.

Click to expand...

I agree ... The newer adhesives/ fillers/ silicone for new car bodywork, is unbelievable... I need to update, myself...
I will leave it, at that...

GeorgeH said:

Most of the late models I've been into, and it's been many, in addition to the foam there is also plastic gussets in place whether it's in a sail panel or rocker adding some kind of mechanical advantage. The adhesive properties of the foam make them a bear to get loose when replacing panels. I don't see a retrofit being worthwhile other then sound deadening. The stuff will make a tin can sound solid.

Click to expand...

So foam was meant to flow in and around these plastic gussets or were the gusseting more to contain the foam in a certain area? Do you have an pictures of what your referencing?

If the best outcome had is sound deadening, nothing wrong with that.

Most of the foam in new cars is for energy absorption (occupant protection in a collision) and sound control.

Different densities of foam are used. For occupant protection it's ridged foam. For sound and panel flutter it's often a flexible foam.

The plastic gussets mentioned above, snap into the inner structure and work as a barrier to control the foam when it is applied. They prevent the foam from going where you don't want it it go.