The Jalopy Journal
Discussion in 'The Hokey Ass Message Board' started by pzofsak, Aug 2, 2013.
Sounds like RUST waiting to happen
Sand would make it more rigid!!
shut down in 3-2-1
Manufacturers that spend billions in R&D do it all the time.
Especially to convertibles.
Ask a guy who does Demolition derbies, or look in the rules. If it did work, it would be banned I'm sure. Concrete and axle shafts were common , never heard of fom, although where I came from, Unit body cars were not used often.
As has already been stated, there are at least a dozen different types of "foam" being used in today's vehicles.....including pickup trucks. And to say all foam causes rust is just plain wrong.
Here is what I have learned over the years using 8lb urethane foam in unibody cars and boats.
It does add rigidity, provided you have enough surface area of bonded foam to steel. This is one of the reasons it works so well in unibody structures; lots of channels and pockets and lots of surface area. Done properly, it can actually make a HUGE difference. We've done some redneck testing using a jack and a tape measure. We jacked up a corner before and measured how far up we had to go before the other corner lifted off the ground, then did the same measurement after foam. On an E30 (87 BMW 325i). Before was 3.5", after was 1.5". Not definitive by any means, but sure does make a difference in NVH when you drive it.
Many boats use 4lb urethane foam for floor structures. You screw down your plywood and cut a few 2" holes. Pour in the foam and let it expand. It adds a ton of rigidity, supports the floor, and doesn't hold water.... at least for about 20-30 years. When I redid the floor on my 83 Baja, the foam under the floor was saturated. The stuff is incredibly strong; I had trouble breaking it up with a spade shovel, but it was exactly like cutting into an apple. It was about the same consistency, and just as juicy.
In your frame rails, you have long, skinny channels with very little bonding surface area. I don't think you would notice any difference at all. In fact, I'm toying with using foam in my 66 Bonneville, but I will use it in the "unibody" part; pillars, floor supports, trunk sides, etc. I think the frame would benefit from an X-member and/or boxing, but foam in the frame wouldn't do much.
Regarding rust: two-part urethane foam is closed-cell. It will not absorb water. However... after years of fatigue, vibration, and expansion/contraction with temperature changes, I have to think that it may very well begin to hold a little water around the edges. In the case of my boat as you can see, it did eventually take on water.
Yeah...thats the story...but oddly enough I cut open factory foamed rocker panels on fairly new cars and find lots of rust.
Cars leak and also create condensation.
Somehow it gets between the foam and metal and it rusts the body.
Seen it far too many times.
Yet closed cell foam doesn't hold water...therefore can't create rust.
Guess it depends on who people want to believe!
Scientists who create products for a particular purpose or people who see the real world results of those same products.
A couple of years ago we did a minivan with foamed rockers at work. Insurance called for a used rocker installation. Fair enough...
The local yard ultimately sent us 3 different rocker assemblies from 3-5 year old vans.
Upon clean up and inspection of each there was too much deep rust internally to make using them on the van acceptable.
Insurance relented and allowed a new rocker assembly.
It goes on and on.
Foam is there for NVH purposes. Easy to apply and foolproof.
BUT don't forget...job 1 isn't to create a vehicle that lasts a lifetime.
It's to create a comfortable vehicle with a finite lifespan.
Foam apparently does both.
The ability of Average Joe, or even Better than Average Joe, to properly apply foam inside of a bunch of blind crevices on a 40 year old frame are just about zero. A multi-million dollar auto factory applying foam in operating room conditions might be a different story. Maybe. Let's not forget, even BMW or Jaguar or Mercedes really doesn't care what the frame looks like 40 years from now.
One way for a tube or box section to fail is by having the wall buckle.
That can happen either from a bending load or a compression load if the wall thickness is "too thin." What is too thin depends on the geometry of the tube, basically length, but diameter enters into it too. I guess foam >might< help prevent buckling to some extent and raise the load that would make the tube buckle.
I'm guessing that was the logic behind foaming the acid dipped components.
'69 bonne filled with expanding foam huh.
That goddam chicken swore it would get shut down ever so slightly slower then an S10 chassis with a turbo ecotec swap question.
Isn't conforming to non-conformity still conforming?
4 pages? Even it worked you'd never know it. There are a thousand other ways to increase stiffness and improve handling, let's move on with life.
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Anyone ever seen the packaging peanuts that dissolve in water. They are so much fun. You can put them in the sink and turn on the water and they just melt away. Never put one in your mouth it turns into a nasty goo. Funnier if you talk someone else into putting it in their mouth.... The packaging peanut that is.
Precisely. The aim is twofold: 1. to separate reliability from durability and to ensure that the product performs consistently for the short time until it fails irreparably (both plastics and electronics have useful characteristics in this) and, 2. to capitalize on technological advantage by defining the product as something you and I can't make using common tools.
As a practical matter I don't think there is anything to be gained from foam in frame rails. The rails are already plenty strong enough in beam strength, but regardless of what you might pump inside them they would still not be quite rigid enough for handling purposes. The more you chase dynamic performance, the more roll control you want, the more differential F-R roll stiffness you incorporate to achieve it, the more you're asking of the frame. And that can be considerably more than drive shaft torque.
This is especially true of cars like this which were designed primarily with a comfy ride in mind. The rails are sized to the sorts of spring rates needed for comfort, not for staying flat in curves.
I'm a big fan of interconnected suspension which takes all the torsional inputs out of the frame, but it isn't as if there is a bolt-in kit or anything. It is quite possible to make that thing ride like a goose down pillow and corner like a Lotus 7, but it would involve venturing onto uncharted territory.
I won't apply any product I may have to remove at a later date so that includes foam, asphalt undercoating, por15, rockerguard etc. Also with foam you have no idea where it is going to land. I used to install urea formaldehyde foam insulation in houses,,the stuff would start creeping out everywhere,,even popped the drywall off a few walls from installing to much...
i had to fix a frame on a nissan pickup a friend of a friend had just bought that was foamed and sanded and undercoated over to look like it was good they caught it at inspection when i picked out all the foam there was only 2 sides of the frame left! scary shit but the foam was soaked moisture all inside the frame and it hadent rained in over a week. id never think about using it its a moisture trap
is foam traditional?
Foam against steel is the reason so many late model dodge rams are rusty piles of crap up here in the north. People expect their pickup truck to sound like a Bentley when they slam the door so they spray this junk in every orifice.
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