Chassis strenghtening and soundproofing - foaming

[L36328]

Here's a mod which will improve both the handling and the soundproofing of your ride - foaming the chassis.

Below is an extract of a writeup on chassis foaming from Sportcompactcar web, under their Project Nissan 300 Part 5.

" Foam-Filling the Chassis
In any high-performance car, it is impossible to make the chassis too stiff. The stiffer the chassis, the higher its natural frequency, making the energy imparted to it by bumps less likely to excite the body's structure. A stiffer chassis enables the use of stiffer springs and shocks without hurting the ride. This is because a stiff, non-flexing chassis transfers more force into the suspension where it can be dissipated by the springs and shocks instead of transferring the force to the occupants. A stiff chassis is also more responsive to roll rate tuning for balancing understeer and oversteer. This is one of the reasons why automotive engineers are continually investigating ways to stiffen chassis without adding weight.

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.

To get the correct foam for our project, we contacted Art Goldman, Foamseal's automotive product manager and author of an SAE (Society of Automotive Engineers) paper on the use of structural foam for the stiffening of automotive unibody structures. We used Foamseal's two-component foam kit, p/n 11-22 to fill the main members of the chassis. Like we mentioned earlier, Foamseal is the supplier that I-CAR, a national certification group for quality auto repair, recommends for the repair of damaged, foam-filled chassis. The Foamseal kit uses a two-part catalyzed polyurethane foam, which quickly cures into rigid, waterproof, closed-cell foam. To prep the car, we carefully masked off all painted areas anywhere where the foam could drip. As this sort of foam is a thermosetting catalyzed plastic, we realized it could be icky if it spilled on paint or any part of the car's interior. This foam is nasty stuff. It is impervious to all known solvents and cleaners.

Rubber gloves must be worn. Get some of it on your hands and it will stay there for more than 3 weeks--don't ask how we know. Do not get this stuff on your paint. Wear old clothes; we ruined ours while learning how to handle the product. We injected the foam into the rocker panels and frame rails of Project Z through existing bolt and drain holes. When injected, the foam reacts like shaving cream and quickly expands to fill the empty space. You can judge how much foam to add by watching its expansion progress through some of the holes. Once injected, the foam expands and begins to cure in about a minute so you need to work fast and plan how you inject the foam before you start.

The life of the foam kit is limited to a few hours once the seal is broken. We filled all of the Z's unibody frame members using five foam kits. When foaming a chassis, you must remember the wires and other lines that pass through the chassis must be relocated or they will be entombed forever.

We were amazed at how this simple procedure improved the performance of the car. The chassis now almost feels like it has a roll cage. A sloped driveway can be driven up sideways with nary a creak. Even though the Z already has a pretty tight chassis, it feels more solid. The ride has improved and road noise has been reduced noticeably. We bet that the car will be even more responsive to chassis tuning measures in the future. If you are a slalom racer, a road racer, have a lowered car or even just want a smoother ride; foaming is a worthy, easy-to-do modification. Foamseal has foams in densities as high as 10 lbs per square foot if you desire to make things even stiffer.

Do not--I repeat--do not attempt to use cheap, hardware-store canned foam. This is not the same thing, and if injected into your chassis, will form a gummy mass that won't dry. Foamseal foam is a professional grade foam, which although it is a little unforgiving to cleanup mistakes, has superior mechanical properties and catalytic curing so it will dry even in an enclosed space...."

[L36328]

Not all foams are created equal. Note the different densities.

DSC00696 - diff type of foam.JPG

B-pillar, unfoamed. Note the empty hollows.

DSC01112 - unfoamed B-pillar.jpg

B-pillar, foamed.

DSC01119 - foamed B pillar2.jpg

Injecting foam into the B-pillar. Foam expands and oozes everywhere, so tape up all them holes!

DSC00780 - B pillar.JPG

Foaming is not just for Japanese cars...
DSC00841 - foaming aston sill4.JPG

[BMWjiggaB]

Where did you get that can of foam from??? Im interested in doing that myself also!

[leedawg]

Yeah thas what im wondering where to get ahold of these products. Looks amazing and im all about making the chassies quiter than they are right now.

[Mr.M]

Have you or anyone else found any more technical articles on this? Like published ASME papers or anything?

[takem2church]

i am excited to do this also! thanks for the pics. if anybody actually happens to do this fairly soon do you think you could do a diy showing how to foam the chassis, not just the b-pillar. thanks a lot! hopefully i can get this done in the upcoming months

[Jester4176]

This stuff is kind of pricey. Maybe a GB can be arranged? At $40 a kit, cost will add up quick.

http://www.foamseal.com/auto_after_ordering.htm

[BMWjiggaB]

So how much will a kit do??? I tried calling them today and just got an answer machine so....idk how much it will cover. Today i was laying down some dynamat and once you remove the carpet, you can see a bunch of rubber plugs that open up into a gap in the floorboard. Same thing in a few other places also.

[auto3251]

intresting...

[CRYPTiC]

Who wants to be a guinea pig and try this out for the rest of us?

[takem2church]

Who wants to be a guinea pig and try this out for the rest of us?

+1000

[beatniks325]

interesting, might use this stuff to fill some loud spaces in my E21.

keep us posted, someone buy it

[ichiwan2]

interesting, might use this stuff to fill some loud spaces in my E21.

keep us posted, someone buy it

With the e21, u could also fill the rear quarter-panel with the PU foam - I also did the side sills, B-pillars and some cross members on mine. Body feels a lot tighter and does not roll so much, less creaks when going up/down ramp at an angle. Car also much quieter - can hear engine better.

[Yahweh]

Can this create rust?

[L36328]

No, it does not absorb water, if that's what you mean.

However, one needs to avoid foaming up channels meant to drain water, and this takes some experience.

[nozatechm3]

I was thought about that after insulating house with can foam from Home Depot..

[robisconfusedd]

how much weight would you assume this adds?? not much hopefully?

[Roktgr]

Foamseal has foams in densities as high as 10 lbs per square foot if you desire to make things even stiffer.

how much weight would you assume this adds?? not much hopefully?

Read much...


I disagree with the above statement that you cannot have chassis that is too stiff. That the same problem you can run into with too many gussets, they stiffen the joint and therefore more stress will be taken up in that joint and can cause failures. I don't think this will be a problem with this stuff but just a useless fyi.

[L36328]

how much weight would you assume this adds?? not much hopefully?

Not much.

[L36328]

I was thought about that after insulating house with can foam from Home Depot..

I wouldn't use house insulation foam for the car though. Different specifications.

[RAD82]

Not too sure this is a good idea for everyone, as I've been told by people in car audio using this for soundproofing, to stay away from the expanding foam. Apparently that in places like kick and door panels, the expanding foam can cause the outer skin to expand and warp.
Wether that's true or not i don't know, but not willing to try it out.

[Mad Machine]

the expanding foam sold by lowes and home depot is the same stuff the OP said to stay away from. Not only can it expand enough to warp sheetmetal, but it will never compleatly dry in an enclosed area (it needs are to dry) and it absorbs water, which can and will lead to rust.

I have been looking into structural foam for my V6 Fiat spider project. Being an older roadster, all the stiffness I can get into that chassis is good.. thanks for the write up and how to get it.

[Tefal]

Read much...


I disagree with the above statement that you cannot have chassis that is too stiff. That the same problem you can run into with too many gussets, they stiffen the joint and therefore more stress will be taken up in that joint and can cause failures. I don't think this will be a problem with this stuff but just a useless fyi.

Correct, that is why not even Rally cars are "fully seem welded", They leave a gap in between the welds otherwise it becomes too stiff and the body cracks plus if they have a accident it is more difficult to straighten the shell. A FULLY seem welded shell(leaving no gaps) is no stronger than a fully stitch welded shell.

[BMWMPow3r]

This stuff is kind of pricey. Maybe a GB can be arranged? At $40 a kit, cost will add up quick.

http://www.foamseal.com/auto_after_ordering.htm

the link is dead.

does this stuff come in a can? does it have to be mixed?

[ZeitGeist]

Is it me, or does that aston carpet look like home carpeting? Man I better start playing the stock market, playing basketball, or singing or something lol.