"mark" wrote in message
...
My original jeep CJ-7 frame has rusted out and I was thinking of
building a new one from aluminum. Would 2 X 4 X 1/4 wall (if that is
even available) box tubing have the equivalent strength of the stock
1/8" wall steel frame? I would like aluminum because it will last
forever, no need of any paints etc..., very easy to work with and
cheaper than building a steel one and having it galvanized. My second
choice would be stainless 1/8" box tubing.

This looks familiar, Mark. Didn't you post this same question here three or
four years ago? Someone posted something similar.

Anyway, as Joe Gwinn says, aluminum has 1/3 the stiffness of steel, roughly
1/3 the strength for low alloys of each, and weighs 1/3 as much. A box
section tube doesn't take advantage of aluminum's low density, so there is
no weight advantage in using aluminum in this way. To get equal strength in
the same section (2 x 4), the aluminum tube will have to have walls that are
3X as thick as the steel one.

I don't know Jeep frames but if the frame isn't boxed (in other words, if
it's a U-channel or top-hat section rather than a rectangular tube), and if
you use box-section aluminum to replace it, it will be a great deal stiffer
and stronger. But that's because the tube is stiffer and stronger, not
because it's aluminum.

All in all, aluminum sounds like it's a lot more trouble than it's worth.
Welding that thick section and producing a *strong* weld with it will be no
picnic, unless you're an expert. It will cost a lot more for the material. I
can't speak for the galvanizing but I thought that hot-dipping a frame was
supposed to be a reasonable cost proposition.

I'm sure you'll get other opinions.

--
Ed Huntress