I did the bodywork on a Pantera that was foamed it was a total rust bucket .They rust like hell without the foam.The bodys on them is a realy low quality hack job from the factory.But the foam had realy accelerated the breakdown. You could grab a beam with your hand and rip out a big cunk of rust and foam
I just reskinned the rumble seat lid on my 30 coupe and I put the expanding foam between the inner and outer skin to give some rigidity to prevent oil canning. Worked good there.
Around here the foam the factory put into lower body sections of then new cars made them rust out very fast. Closed cell...open cell...whatever...it made the areas rust and I don't really know how or why or even care for that matter. All that concerns me is it DID. In the Texas climate you might get away with it...but I do know this: IF you had it for sale and I went to look at it, foam inside the frame or anything else would be a total deal breaker. I wouldn't touch it with a 10 foot pole. Besides that...the car doesn't need it anyway.
Most expanding foam is very flammable, I was working on a 60 elky plasma cutting a quarter off some bodyguy (an I use that term lightly) had used foam to back up his hack job rust repair, well it sure scared the hell outa me when I hit It was like a flame thrower. Andy
Dont forget the damping is being changed as well as the rigidity. Typically cement is used on milling machines. I recommend you guys to buy a machinists handbook, lots of good info about this in that book.
If you want to spray anything inside the rails use fog oil to slow the rust . Why do you think todays cars are so quiet. Takes the drone out of all those cavitys. It may help a little in a crash in a new but who knows to what extent. It's the only things that makes that thin sheetmetal sound solid.
I think it would cause a rust problem no matter if the cells are open or closed. I would not trust it to form a permanent, water-tight seal. I'd expect mositure to get wicked or held betwene the foam and steel.
I work on new cars daily and i've seen rust forming after digging out that loaf of bread. I really can't understand why they do that. I guess it's all planned obsolesance. Surely they could come up with a better product than that.
I agree, dont plan to ever do any welding or grinding on your frame after you fill it with foam, all it takes is one spark to light that stuff up, and it burns fast! I have managed to light a few late model vehicles on fire that were filled with that garbage, It makes no sense to use it on an old vehicle, expecially inside a boxed frame where you can never remove it.
There's different kinds of foam. The only stuff that's going to provide any meaningful improvement in rigidity are the epoxy structural foams like some of the Henkel Terocore products. Once cured they're basically hardwood. They're used in various OE applications, stiffening pillars, the last Crown Vics had areas of the frame filled with it, BMW used something similar for warranty repairs of rear structures. It's a good idea, just takes a certain amount of logistical support to heat and pump the stuff in.
I can think of a couple of (at a REAL stretch) NON-OT cars that used foam in activities of their bodywork. It caused rust in all cases. I was/am into OT Jaguars that had foam filled front suspension crossmembers. They tended to rust out, the foam held moisture. Meanwhile, how on earth did a thread about a 69 Bonneville using modern suspension make it 3 pages?
I once restored a mid sixties Alfa spider that had foam in the sill areas (from the factory I believe) it was the most rotten car I have ever worked on. (I have restored some pretty rotted out cars) David
In the 60s Opel made a Record Coupe with a six cyl Engine. and the front crossmeber was to weak. The fix was to fill the xmember with Concrete.....Typical Gambia Motors quality repair
There've been foams used for sound insulation for a long time but those don't help structurally. The structural foams are a somewhat more recent development. I've always figured it'd be an interesting exercise to fill the pillars, halo etc. of something like an A Tudor with Terocore, box in the channels where necessary, it'd probably be both stronger and 'deader' than nailing in fitted wood.
JEM, this topic has brought some sound thoughts out on structures and the effects foam can inflict, or offer. I read it to see what our brain-trust had to say. The Morgan cars had wood in their frames, and it seems that foam might benefit there, if the geometry/size made good use of it. In a steel frame, properly designed, it might only quiet the drumming, without enhancing the stiffness.
the answer to the original question. foam does increase strength in uni-body and full frame BODY construction. The auto manufactures add these for collision energy management and sound deadening. The foam is used to transfer the energy in a collision away from the passenger compartment. It was also used buy some racers to stiffen uni-body drag cars who were not worried about preserving a car but winning races. Your full frame in that car would not benefit from the adding of foam in my opinion. If for some reason you have so much hp that support is needed than use steel.
Later model vws (70s and what not) had that stupid foam in the c pillars. Almost every single one of those rust out in that area, and it's not even near the ground. This sounds like a horrible idea.
I do contract work at the plant that makes Henkel automotive products. Pretty interesting stuff. Makes steel much more resistant to bending, flexing and deforming. And it does NOT absorb moisture. Good luck getting it in a frame rail, however... http://www.henkelna.com/product-search-1554.htm?nodeid=8797991731201
I heard about this years ago and filled the rockers of my unibody car. Unfortunately all the drain holes were blocked. Any water that got in couldn't get out. A few years later there were major rust outs. Factories do it but it's designed into the car.
Don't do it! foam holds moisture between it and the metal , it will create rust.I have cut many cars apart that had foam and seems like most had corrosion or rust issues. Your frame should be strong enough without it.
Here's some common examples of foam causing rust. 97-03 Grand Prix rear quarters by the gas tank door, and top center of arches 97-02 ford pick up truck box, rear wheel arch. Every one of those ever made has foam in those areas and everyone that sees moisture rusts . So maybe the foam itelf doesn't "absorb" the moisture, it justs holds moisture against the steel until the steel rots. There's a definite correlation between foam and rust.
Wow! This calls back those boats that were filled with urethane foam between the floor and hull. Over time they'd suck up enough water to increase the weight of the hull tenfold. Same thing happens to a lot of steel entry doors for houses. The bottoms rot out because the foam inside is holding water. Those old grey Stanley doors were famous for this. The only foam that will not hold water is the regular EPS (expanded polystyrene) white styrofoam, and some of the newer pink and blue sheet stock urethanes. Anything expandable is going to destroy your frame. It may take awhile but it will destroy it.
As others have already noted, whether the foam hold water or not does not matter. You know there will be plenty of places in a frame where the foam is not 100% bonded to the steel, and that's where water will sit. It'll get there from condensation, no need to drive the car through a river.
Bullshit. Somebody was smoking crack and publishing on the Internet. Foam has lots of air bubbles in it and air bubbles compress easily. More bullshit as I've opened rockers that some genius filled with foam to stop rust. The rust only got much worse due to the water not having a place to drain. More crack smoking and typing for sure.
I used that stuff back in the seventy's when we put in the Hurst T Tops in car"s . That how they got the cars to pass the crash test. I also used it in Van's to solid up the walls on the inside but that stuff is juust a mess, After awhile it breaks down and if you have to do a repair, ya got a can of worms to deal with !!
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