Has any one stiffened there subframes or rocker panels with high density structural foam? I know it is popular with the imports. Anything to make a gen 3 more rigid is a good thing. If this has been done please speak up! The idea is to inject high density structual foam into the frame or unibody voids. The foam expands into the void and increases the strength of the frame members. Strength without adding much weight.

 

Sorry, nice try, but that won't work like you think it would. I have been in construction for 20yrs. That expansive foam crap will help with sound deadening, and helping prevent a body panel from colapsing on impact- but wont hold even a bit of structural flex resistence.

 

thats probably why the import kids like it... so their systems have more boom boom..

 

I'm not talking about the foam you would buy at the hardware store you get in an aresol can. I'm talking about the high tech stuff used in the manfacturing of composit aircraft wings that will handle over 4g's loading. I DO believe this stuff can offer a considerable amount of structural enhancement. Are we blessed with the presence of any areo engineers reading this post that would like to offer some input? Experimental aircraft builders?

 

Some of the members over on Corvetteforum.com have tried it, but I've never seen any one post any definite results from it.

 

Its been used in boating for years, but they only use it in waterproof cavitys. Which leads to my major concern. If it holds in moisture or even water for that matter its gonna rust your subframe from the inside out which isnt going to be good for rigidity. While it may help some i would go with subframe connecters, or if you already have them, custom subrame connecters to tie the frame together better.

 

*cough* roll cage *cough*

 

Sounds like a great idea on paper but like you said, it's new for cars so who knows if it'll be able to help with measurable results.
As for holding in moisture, I don't think that'll be an issue if the foam has a good bonding to the metal as it should if it's to increase the strength of the rails.
I bet it'll work but the use could better be developed if our cars had been designed it's use in mind. I bet a large frame thin wall with structural foam would be really ridged.
You'd have to have the welding of the SFCs before the foam.
Does anybody have any links to what stuff needs to be used? I can do some static tests to verify any expected results.

 

http://www.itwfoamseal.com/auto_aftermarket.htm


I think this is made especially for cars.

It comes in different densities as well.

Sport Compact Car also employed some of it in their Project 300ZX Twin Turbo and reported some success:

http://www.sportcompactcarweb.com/pr...scc_proj300zx/

At the bottom of the article. He also points out that this isn't the same kind of stuff you get at hardware stores, etc.

I'm really wanting to try it myself.

 

From the SCC article.


It's only $34 per kit but you need probably four kits to do it.

I'm thinking about buying one kit and injecting it into some objects and trying to bend them and such, like coke bottles or
tubes or something.


I'm broke though after buying the S&W SFCs and I'm having them installed next week (after coming back from F1 @Indy!) so I'll have some pics of that.

Go for it JPrevost.

 

I still am not buying the idea- I'll tell why-

The article makes claims to a better feel of the car, yet posts no before or after test results as to performance of the vehicles handling.

Secondly, years back I did this to a modified VW Karmann Ghia that I built. I completely filled the quaterpanel cavities and front subframe spaces with the standard "hardware store expansive foam"- same damn stuff, don't let them kid you(try to clean that stuff off you. And it does dry properly contray to the articles info). What it did do was inprove the comfort level of the ride from sound deadening. Just like a surfboard (made of structural foam) it has no tortional strength- it only withstands collapsing forces buy filling up an otherwise cavity. Foam is an insulator and is used in upper end vehicles as a road noise supressor to detatch the occupants from the outside world noises.

 

It's not easy to quantify a chassis rigidity increase, or do all those mods at once like they did and differentiate the foam's effects.

I don't know. Saying any foam=any foam is kinda like saying any steel=any steel, or any analogy you want. Guaranteed to be more complicated than that.

I don't think your experience is equivalent, vsixtoy. Kojima seemed to emphasize the foam's nastiness, so either you got the same foam with totally different properties or one of you is lying. And I will take the word of a mechanical engineer (Kojima, the article's author, also author of many sound performance books) and another SAE engineer (the foam reference guy for ITW mentioned in the SCC article) over that of someone who tends to make ambiguous quasi-arguments.

I'll keep an open mind about it until some unbiased individual does a definitive test with that particular brand, that modification by itself.

 

In a final bit of reengineering to stiffen the body, we injected the chassis with catalyzed rigid structural polyurethane foam. 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. Since we cannot retool custom parts to redo the Z's body, we figured that this would be an excellent, low-cost way of greatly increasing chassis stiffness. Injecting foam is not a new technique for chassis stiffening. The Infiniti Q45 uses this sort of foam in some of its chassis members to increase stiffness, as do a few other premium cars. In fact, the foam we chose is the foam recommended to repair damaged Q45s.


As a mechanical engineer i say Yes!

 

Seems like an interesting, inexpensive mod. Besides the frame rails, you could inject it into your STB, SFC's, roll cage, sway bars, the seat rails under the carpet, panhard bar, LCA's, box the upper panhard brace and inject it, and so on..... in theory, of course. I would be interested to see some real world results form an F-body owner, and apart from any other mods. If enough folks said "wow, this stuff really works!", then I'd sure do it too.

Note the bit about entombing your wiring...... I've never really looked in my chassis, is there wiring routed thru the third gen frames?

 

I'm a year away from getting my ME degree and have been apart of the SAE for a couple years now. Just a little background from my side of things; I've also been apart of our FSAE (Formula) project now for a couple years as engine team leader and am responsible for a lot of other parts of the car. We placed 10th this year in a pool of 140 and that's against some very strong engineering schools. We also hold the acceleration event record and won that event last year with a motor I built (along with awesome team-mates). This isn't a bragging contest because hey... I don't get paid to do this project . Anyways, this year there was a new award being given out for usage of structural foam! If it doesn't work to stiffen the car or have the ability to do so then trust me when I say the award would NOT be there. It's an F1 car without the aero (low speed autocross competition) and so everything is ment for speed not noise and comfort!
I've got the facilities to test the strength of these foam injections so I will report the results as soon as I get a hold of the product and have some time to setup. I can say with some confidence that in a thin wall large open cavity that the foam will help substantially neglecting weight penalty... but come on, how much could foam actually add to the vehicles weight?!?! Not to mention the weight is low and near the center of the car lowering the CG and decreasing it's yaw inertia . All good things when you consider our weight bias and front overhang.
Thanks for the link Rembrandt. This should be a fun little side project.

 

not the same stuff.

with the foam you used, i could crush it with my fingers.. matter of fact, i use it to shape custom foam bumpers for my RC cars.

with real structural foam, its much much stiffer. mercedes and some exotic cars already use it for structual stiffening. (not sound deadening)

 

if you look at it you'll realize we dont have frames. Fbodys are unibody cars. there is no frame.

 

I not talking about the cheap DAP white door and window sealant foam. There is a polymere industrial foam that has been on the market for years that is extremely expansive and very rigid- and no it won't squish with your fingers,. Matter of fact it needs to be trimmed and shaped with powertools.

You inject the stuff i'm talking about into a drywall type structure (basic home wall) and it will bulge and physically break the drywall outward in is so strong and expansive.

Pervost- A great test would be to inject the foam into a 36MM hollow f-body swaybar and take torsional readings to see if any gain is present from the hollow state. This test would tell you in a heartbeat just how effective it would be.

 

Then where would we inject this stuff, besides the other places I mentioned?

 

Well I called a buddy of mine to find out what the name of the expansive foam I'm talking about - turns out he tells me that you can't buy that type of foam anymore here in the great BS state of Calif. they stopped selling it a few years back because of EPA restrictions. So I have to admit that the article is correct in saying you can't buy it in hardware stores- not the same stuff (At least not here in Calif.) but you could once upon atime. (How come the older I get, I grow more fond of the "Once upon a time")

 

im praying for the day that the aftermarket automotive community wakes up and moves out of cali.

or for it to drop in the ocean... i think vegas would make a cool coastal town.

 

Hey, I'm a hardcore scubadiver- I'm ready. Just think of all the underwater salvage I could do for exotic car parts.

For the record- Hardcore means: Jumping off a perfectly good boat @ 3am in the middle of the ocean in 10ft visability with a flashlight by myself. Before anyone critic's me for being by myself, I carry underwater eletronic nav gear with me at all times as well as always having life support up top(other people) on the boat at all times in case of an emergency. I also have a sonor beacon on my body in case I don't return in a specified time frame.

 

ahh... so its easier to find the body. gotcha.

 

Thats exactly what I meant by that statement. After all, wouldn't you want to know what happened to a loved one if they disappeared in the ocean? -Its a big ocean.

I know your being playful, but its the honest truth.

One of the littler boats we use(tender) is a Boston Whaler which is constructed of structural foam. The boat is unsinkable.

 

Still waiting for a reply from foamseal. If it doesn't happen I'll get one of my professors to just buy some out of a research budget that was under. I'd REALLY like to test this stuff.

 

This is why TGO is a great board. You have people on both sides of the engineering fence working together to make the third gen camaro better. It's not that offen that someone can have an idea and ask a question. Then have a "ME" get involved and be willing to quantify the experiment. JPREVOST keep us informed with what you find out.

 

That's what they said about the Titanic.

 

Apparently GM agrees with you. They did just this to the 1992 F-Bodies. And yes, I believe it does make a difference. I've ridden in several 82-92 cars, and the two 92 models were much quieter inside.

 

i rather use some metal and weld then some foamy crap...

 

I haven't go to look into my 3rd gen in a week or two. Since our cars are unibody? What areas would use this foam on a stock body to stiffen the structure? I must just not be visualizing my car well enough.

 

The front subframe, the rear subframe, and the rocker panels for starters. If you want to get wild with the stuff then fill every void and cavity that wont be seen or interfear with any of the systems in the car. If you want the bonus of your stereo to sound better along with stiffening the chassis then fill the entire B-pillar around the rear speakers. If you have a t-top car then fill the b-pillars and across the roof to create a roll cage like structure tying the right and left b-pillars together. Are there any body shop people out there to offer any outher input on this subject?

 

Ah... and yes, welding in SFCs are definatly a must for a uni-body but the foam can then be added in after to help. This foam isn't your generic soft foam. This stuff is HARD and STIFF. Hence the hole point of it being called "structural" foam. It's kind of the best of all worlds. I still haven't gotten a reply from them and I left my number that they could reach me at. I guess I try again today.
The application of this stuff is limited to your imagination.
Some things I've thought up other than the sub-frames;[list=1][*]B-pillar[*]Kick panels[*]Front fenders near the horn[*]Front bumper cover to prevent sagging[*]Thin layer on the flat floor pan inside under the carpet[*]Thin layer on the door skin[*]Spare tire area[/list=1]
Weight is obviously of concern but another point to be considered is the trade-off with our uni-body. A race car has a full braced structure with fenders and sheet metal as the non-stressed skin. So if our cars are the other way around then stiffening the skin will result in a better handling car so what's better? A car that handles and weighs 10lbs heavier or a car that isn't as stiff but is 10lbs lighter?
Again, this is all in speculation that the foam does help. Can anybody come up with a way the foam might hurt your car's torsional stiffness?

 

If you stiffen just the front, and just the rear, no middle (IE, no subframes added). It could add more stress to that area??

 

http://www.rimmolding.com/composites/tech_foam.html


Quote:
Structural foams are defined by their density. Polyurethane foams range in density from as little as 2 pounds per cubic foot to as much as 55 pounds per cubic foot. Foams with a density of 15 pounds per cubic foot and greater are commonly called structural polyurethane foams.

What about strength? The flexural modulus of structural polyurethane foams increases as the density increases. An unreinforced structural polyurethane foam with a density of 15 pounds per cubic foot has a flexural modulus of approximately 30,000 psi. A foam with a density of 40 pounds per cubic foot has a flexural modulus of about 170,000 psi. The highest modulus for an unreinforced structural polyurethane foam is approximately 250,000 psi.

 

if i were to use it on my car, i would put it inside the stock vert bracing..

also, if i had SFCs, i might fill thoes with it too..


so id probly fill the factory bracing and the rear part of the front subframe where the SFCs attach...
up front, id brace behind the steering box....

 

Thats alot of weight added- More so than just adding a tubular safety cage(125lbs, and much stronger). 2 cubic ft would darn near fill up the SFC's alone, then add any cavities? You'll add up to about 200lbs+ very quickly.

My main concern even if it does work- is for how long? It would have to weaken and break down from flex stress, then you are in no way getting that out of the cavities of the vehicle. Also the cost of repair if the car were to be involved in an accident- You couldn't just cutout and replace a bodypanel with foam injected behind it filling the cavities.

 

i would be happy if it just made my car quieter!! I image it couldn't hurt in the less dense version if you used it with some restraint. I do not think i would fill frame rails or SFC's with it because it would make welding mods and repairs very difficult or impossible. I do like the b pillar idea though, maybe in the seat belt mounting area for the rear seats and the chanel that makes up the rocker panel. As stated above in thinwall structures it should give the most benefit. if nothing else a street car will probably FEEL better.

 

How did you come up with 2 cubic ft for SFC's? Those are some HUGE SFC's. My Alston's are only 36" long and the OD is 1.25" that's only 0.052 ft^3 so filling them with the heaviest foam would add ~2.8 lbs to the car. That's taking the OD as the ID but still that's next to nothing.
As for the whole car, I calculated out just doing the SFC's and frame cavities, it's ~44.4 lbs if using the strongest and heaviest. That's 3"x3"x36" rails each so x4 plus the SFCs. I think going middle grade structural and adding 25 lbs would probably be worth it vs a roll cage. Although in road racing there's no replacement (yet) for a good cage around the body .

 

How are you going to get the dirt and sh*t out first? Or just foam over it?

 

if you're really curious, why dont you write teh OEMs a letter asking them how its held up for them the last decade.

you can also ask for the mercedes benz repair procedure for their cars...

 

I'm not using it- so personally I don't have the interest to write them.

Ever get a quote to repair body damage on a Mercedes?

 

Torsional? No, that would be a negligible differnce between a hollow one and a hollow filled one. The centre hollow space is not terribly large, and the outer material of the bar has far more torsional strength than the inner material. That's why a hollow bar is a great idea. Secondly, the foam isn't going to shine in torsional strength really.

Tests of bending the bar would be one thing to check but swaybars are not created for that purpose.

To easily measure the flex strength of the foam, you're going to want 2 structures of exact size, one foam filled. And making the structures significantly stronger than the foam within would just make the project more difficult, thus making the swaybar a poor choice in this regard.

 

ive never got a quote to repair body damage on anything.

 

The foam would have to have a close chemical bond and very high resistance to torsional forces. This would equal more weight which is not a good thing. Anyway, the places that the foam could be put are fairly small in cross-sectional area and would not add much to rigidity or hold up under a lot of repeated load. Also if it is as stiff as claimed then it could also be too brittle and crack within the cavities and just become ballast for cornering.

If I'm wrong about any of this let me know, after all I'm just a student.

Personally I would just stick with SFC's.

 

Your concerns are all logical but keep in mind that this stuff isn't just "foam." This stuff is structural foam, not space filler foam. I've seen the stuff in building construction and it's strong stuff! There are different foams for compensation. One foam is not as stiff but like you said, it gives and bonds very well while the other is very stiff but if your car flex' a lot it'll crack the foam.
There is no substitute for SFCs on our cars but after SFCs the rails can be strengthened using the foam.
I expect a lot of skepticism but trust me that this stuff has a strong chance of improving the strength of our chassis.