Any one try foam-filling their chassis?

[Big28 2gFWD]

hey wret here's a good idea for you. i know ## into autox, this is what i did to our shop
1g road race car. open ## door and look around the frame up the a-pillar, b-illar roof, etc....you see all those little dimples in there? drill them out with a 3/8" bit and fill them in with 3/8" rivets. they are all over the car, in the engine bay, trunk, shock towers, etc.. car became extremely rigid after i finished this. best part? the price...rivet guns go for about $25 and boxes of rivets are about $5 each(will take a couple) probably the cheapest handling mod u can do, took about 4 lazy hours to finish the entire car(left a few untouched however) good luck

 

[jtmcinder]

Before you do any of this to an autocross car, read the rules. You really don't want to run in F/Prepared or Modified.

- Jtoby

 

[zephyr_8]

big282gfwd-were you drilling the spot welds? I am curious as to what you are referring to.

 

[Big28 2gFWD]

no they are more like a dimple press(unsure of correct term) they are small circular indentations. oh and btw..wret, sorry forgot you were a convert, but im sure you know where to look regardless...

 

[95CarbonEclipse]

So... did anyone ever figure out the properties that make a foam good for an application like this? I'm not really into autoX, but that doesn't mean I wouldn't like a stiffer chassis. My main reason for doing this though is in-cabin sound reduction.

I'm not planning on going all out and filling every last nook and cranny in order to obtain optimal structural integrity, just a few easy to get to areas (i.e. rear support area between rear struts, rails that the front seats are bolted to, and maybe rear quarter panel open spaces) to improve ride quietness. My main concern is trapping moisture in the foam so I'd like to get the right type to ensure longevity. I'm already in the process of applying a layer of rubberized coating to the floor pan and trunk areas to help deaden noise even more.

Any ideas on where one could find this type of foam locally?

 

[TSIMonsteR]

I used some "great stuff" from home depot in my doors and hatch area. It decreased noise a good bit and my doors are much more solid. I bet it would work for this type of thing and is only $5 per can.

 

[turboglenn]

We foam fill a LOT of the extra spaces in our porsche club cars. After we get them below legal weight, we fill all unibody rails, quater panels etc with foam. We do cut a lot of supports out for weight though, so the foam in the quarter panels is to keep them from buzzing extremely loud and driving you nuts on the track.. Then we distribute weight accordingly to balance the car.

I've never heard of a Stiffening/handling advantage, but most of our cars are set up 55/45 with the bias towards the front. Usually we can get them perfectly 50/50 and adjust for drivers though, so they handle on rails anyway. I'd toss my DSM in a dith to own the car i get to drive on track days!!!!! It's only 412WHP, 1989 944s, fiberglass body, in cabin coil over adjustment, tthe works. This rich guy built it for his son and now his son changed classes and went to a Lotus. Now i get to drive it (the 944) now and then on track days if he's nice enough to bring it out for me and pay for the tires i go through , i can't even afford that. .. I'm just lucky to be able to and only have to pay my licensing and entrance fees (they're still HIGH AS HELL) I hope one day to at least get a permamnent ride, but we can all dream

EDIT: we use whatever foam we get the best deal on, sometimes great stuff, sometimes other brands, but then again, we're not claiming to gain anything from it, just trying to make the car quieter

 

[95CarbonEclipse]

That's exactly the info I was looking for.

TurboGlenn, do you pay any attention at all to how effective the foams you use are in resisting moisture? And, since "Great Stuff" was mentioned, what about this particular foam?

 

[turboglenn]

BY moisture are you reffering to it geting trapped between teh foam and panel causing rust? If so i wouldn't worry about it too much. You can even spray WD-40 or any other lube in the panel surfaces to make it easier to cut out on repairs ( and that would help prevent rust as well if that's your concern)

We use some weird penetrating oil we get by the gallon to coat parts that may need to be "realeased" for repair or repalcement.

ALso.. we put foam in gas tanks that aren't swapped for cells (mainly depends on class rules).. i'm doing my DSM's tank this summer (completely different foam though, buy it from "fuel safe") and it does wonders for the cars that starve for fuel in hard corners( i.e. 2g GS-T). I'm adding that along with a complex baffle system to let me run a low tank on the road course.

 

[95CarbonEclipse]

Rust was my main concern.

Last question (i think)... when applying the foam, do you tape/seal all the other holes up in order to prevent the foam from expanding outside of the boxed in piece of metal? If so, what works best; cardboard, tape??

 

[TunaTalon]

Bjones, in spite of your reservations, I'm sure someone here will try it. Can you recommend a way to objectively test the results? Something that could measure frame-flex before and after?

With a wheel out of balance the car will shake the most at the speed where the frequency of the imbalance of the wheel equals the native frequency of the chassis. (resonance) For my Talon with front and rear strut tower braces the maximum vibration comes on at 90 MPH or about 22 Hz.

To measure the effect of the foam put a big ugly wheel weight on one front tire and note the speed where the vibration peaks. Add the foam and repeat.

Taking into account the circumference of the tire convert the two speeds to frequency. If the foam works as expected the vibration will peak at a higher speed after the treatment.

 

[turboglenn]

Rust was my main concern.

Last question (i think)... when applying the foam, do you tape/seal all the other holes up in order to prevent the foam from expanding outside of the boxed in piece of metal? If so, what works best; cardboard, tape??

We put loom on all the wires and such that will be in the way, just so we can cut the loom away and have intact wires, lines or what ever's in there. Then just let it overflow out the remaining holes on the insides of the car and trim it with a razor knife or electric carving knife when it dries. If you plug off all the areas to keep it from expanding out some where it will sometimes bow the panel from pressure.

Just lay down plastic and/or spray a WD-40 or equivalent anywhere you don't want it to stick. Even when applied in the panel if it hasn't been rustproofed by paints we just throw some WD or similar in there, the foam will be held in place by all teh cracks adn shapes it expands into. Then as I said, just trim off the excess

 

[95CarbonEclipse]

Perfect! Thank you for the simple but effective walk through.

 

[architechnik]

On Street Tuner Challenge, a relatively lame show that comes on Speed Channel occasionally, I saw they used expanding foam epoxy for filling the chassis of an old Skyline R32 or something along those lines. They were concerned about the amount of power they were going to put into it and the relatively weak chassis for that year.

They had some large containers with measurement notches. Then they had specific amounts of liquid, a base and reactant, for the prime ratio. They then poured those two together and mixed them and the foam reacted after about six minutes to expand from less than a gallon of mixture to a volume of about six gallons.

The whole car was stripped and put on a chassis hoist attached at the front an rear that rotated the whole shell. After they tack welded and corner welded all the main points they guessed at how much volume the internal parts held. They taped up the ends and poured it in.

Now mind you, this was LIQUID going in, not expanding as soon as air hit it. The reaction caused a great deal of heat to be released and completely filled all the available area and poured out the ends. They did leave small holes drilled in the ends for air to escape.

EDIT: EDIT: Sorry on the last link, wrong car. Here's the link to mild description. XS Engineering - Information - XS News - Street Tuner Challenge on the Speed Channel

 

[turboglenn]

NO problem, i was shocked the first time i saw the cars in the shop with this in them and then even more shocked when showed how we apply it and then just cut and clean off the excess. It REALLY quiets panel rattle down to virtually nothing. Leaving you the ability to hear other issues in the suspension or drive line.

You should see the method we use for bleeding breaks between track days. They will get so hot that even racing fluid developes bubbles, so we put a hopper of fluid on the mater cylinder res. then loosen one bleeder at a time (2 to 4 per caliper on our braking systems) and let gravity bleed the air from the caliper where it developes. Much easier than the traditional pumping and bleeding then repeating till done. This way you just let fluid flow through the lines untill there's no air left. You flush them in a similar fashion as well

 

[romeen]

If you plug off all the areas to keep it from expanding out some where it will sometimes bow the panel from pressure.

Agreed. I've seen this happen with use of the Great Stuff brand. I was surprised at both the volume of expansion as well as the force that the expanding foam is able to exert. It can definitely cause bulges in body panels if not given a path for the excess to escape.

 

[95CarbonEclipse]

Good advice.

 

[roadrunner2176]

The expanding foam produces an exothermic reaction, if there was any moisture trapped, it would be evaporated and an airtight seal would be created.

I dont recommend foam as a chassis stiffening agent, it is very flammable before and after curing. Although it is strong, it also degrades or softens over time. Works wonders for sound deadening and back filling on sideskirts, fenders, bumpers, door panels, but as a chassis brace on a unibody sounds a little good to be true. If this was actually auseful chassis brace, don't you think that auto companies around the world would be using it everywhere.

Anyone remember those FORD quiet steel commercials when they show how they heat the frame and the foam pellets expand to seal and quieten the frame. I think thats as good as it gets for foam as any type of brace.

Quiet steel
YouTube - Ford F150 vs Other Trucks - Quiet Steel

Really bad example
YouTube - Mythbusters ABfoam prank

 

[95CarbonEclipse]

It sounds like the actual benefit of strengthening the chassis is still debateable but, if expanding foam in fact helped, what would be the area's that one would target on our cars?

The closer the weekend gets and the more I realize how simple it would be to foam fill other areas while I'm filling the interior spaces that I originally planned on doing, the more I think I might want to fill those other areas as well.

 

[architechnik]

Here's an interesting run-down from a collision information site.
About I-CAR - Current Events/News: e-newsletters: Advantage Online: May 10, 2004

This also has a few videos on the side panel for acoustical foam filler. The information includes ways to tell the difference between acoustical filler and structural filler.

Someone asked why they don't use it structurally if it could actually provide benefits. The answer is that they do. This solution is fairly new and most companies have not adopted it for all lines of vehicles. Newer vehicles do typically have it in areas that require a great deal of structural strength but are also typically areas of high weight.

Since the site mentioned above focuses on collision repair, they remind that areas that require welding might melt the foam and areas may be restored to look new, but often the structural foam underneath holds damage.


EDIT: Dow Jones' BetaFoam is a higher-density structural foam that, "provides stability and crash/energy management benefits to the A-pillar and longitudinal rails."

More information from SAE: Influence of Structural Foam Properties on the Performance of Automotive Body Reinforcements

And a little article here: Filing the Gaps: Straight facts about two-part dispensible foams - - SEARCH-autoparts.com

 

[Defiant]

If this was actually auseful chassis brace, don't you think that auto companies around the world would be using it everywhere.

Infiniti does, although undoubtedly more for sound than strength.

 

[roadrunner2176]

Infiniti does, although undoubtedly more for sound than strength.

Exactly, Infinity as well as other auto companies use it to dampen sound, as for support, not yet.

I don't think it's impossible to use foam as a support, but it makes for a better brace than anything. I see it's purpose more as a dampening agent and appearance factor than anything else. The foam can be hidden, and doesn't consist of an oil based rubberized spray adhesive for interior applications.

When you think of it filling a-pillars and door panels they will make the panels semi solid, but lets say you have a side impact and instead of the door skin and interior receiving the impact energy, the energy would be transfered through a solid core door and into you. This is why vehicles have crumble zones and bumpers are not solid.


Bad example, but our front and rear bumpers have a foam core, remove the core and theres about 1.5 inches of in-out play, with the core its firm, but it doesn't add any structural support, it provides a structural brace between the inside of the bumper and the bumper support.

 

[timloomis]

After cutting my old eclipse apart with a partner saw, I would recommend anything to add some strength to the unibody, . It's basically just those 2 gussets the have most of the strength in the car. I cut them and the car just buckled.

 

[95CarbonEclipse]

It sounds like the actual benefit of strengthening the chassis is still debateable but, if expanding foam in fact helped, what would be the area's that one would target on our cars?

The closer the weekend gets and the more I realize how simple it would be to foam fill other areas while I'm filling the interior spaces that I originally planned on doing, the more I think I might want to fill those other areas as well.

Does anybody have any good suggestions as to what area's on our cars could benefit from being foam filled (assuming that this would give structural integrity to the car)??? I've already started filling areas inside the cabin to help dampen noise.

 

[habitatguy187]

Bump!