I've got one of those Toyota mini motorhome deals. It's older and the box needs replacing. The vehicle is extremely reliable and has decent gas mileage, so I want to keep it.
One of the absolute coolest vehicles I've ever seen is an "old-timey" looking motorhome, made to look like it was from the thirties. The front was a '35 International truck, set on a long Chevy 1 ton frame with dual wheels in back. The body of the camper part was made of sheet copper, with curves put in just the right places. Words don't begin to describe it. It even had one of those old time bicycles on back, the kind with a huge front wheel, and little bitty back wheel.
Anyway I want to make my replacement camper similar, only smaller and different materials. My existing one and the other guy's both are made from box-tube steel frame. What I'm wondering is: If I use sheet aluminum over steel frame, how bigga-deal is that, as far as bi-metal reaction goes?
I have a little wire feed welder, but converting it to aluminum welding sounds like more expense and learning curve than I want to deal with.
I thought of doing the roof with expanded PVC, but I'm not sure of the durability, or expansion/contraction factor. Whatever method I use, I'd rather not re-do it again 5 years from now.
Thanks for any help.
Posted by Joe Rees (Member # 211) on :
I'm certain if you rivet or screw aluminum to that steel frame you will have definite problems. Whats the chance of framing over the steel with wood and screwing your aluminum to that? Or use fiberglass panels.
Posted by Mike Pipes (Member # 1573) on :
It's simple.
Paint the steel AND the aluminum with a tough paint. There are bituminous paints out there for the very purpose of isolating dissimilar metals but any material that keeps the metals from directly contacting each other will suffice.
You can then fasten the two materials together using stainless steel hardware, which is compatible with both metals... or silicone it together.
Posted by Joe Rees (Member # 211) on :
Really Mike? I wouldn't think bituminous paint would stay intact with the chafing of vibrations between the materials, and I'm also surprised on the lesson of stainless steel - I know it's fine for touching aluminum, but I always the process between steel and aluminum was electrical in nature, and that stainless steel fasteners would act as a conductor to allow bad mojo between the two metals evwen if they didn't touch directly. It might be handy to know if I am wrong. Can you expound please.
Posted by Mike Pipes (Member # 1573) on :
If there's a lot of vibration and chafing, yes there will be problems if the paint wears off, but you can lessen those chances if you shim the two materials from each other using rubber or plastic shims, washers, spacers etc. Anything that keeps the two metals from touching (paint, plastic/rubber coating, etc) will work.
As far as the steel/stainless/aluminum thing.. it works fine as long as the environment isn't too corrosive. Stainless is less reactive than aluminum or mild steel so it almost acts as an insulator between the two, but a plastic or fiber washer should be used between the SS screw/bolt and the aluminum to prevent the paint from being scratched off the aluminum.. stainless and aluminum still react. Zinc would be a better choice depending on the environment (like a location near salt water).
The skyscrapers with the all glass exteriors (aka: curtain wall) are all assembled using aluminum framing members and stainless hardware, secured to mild steel support structure. Mild steel and aluminum are always isolated with a plastic shim, stainless makes direct contact with both, anything that's exposed to elements gets sealed up with silicone.
