Thread: Oregon commuter
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Old 03-08-2012, 02:09 PM   #55 (permalink)
Electictracer
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Tango Charlie- Yes I do plan on the skin providing much of the strength for the frame. It would be an interesting experiment to to a before skin and after skin test, but I cant think of a way of doing it with wat limited resources I have at hand.

Quote:
Originally Posted by Ken Fry View Post
If you use the aluminum skin for triangulation, you may want to bond it in addition to rivets, etc. Otherwise the stresses concentrate around the corners.

On big bumps, the structure will try to bend in a way that puts both sides in compression up at the third tube up. On one side, this is resisted by a straight tube. On the other side is is resisted by a much more flexible structure (where the door goes) If the door has a beam in it, then you'll want a pretty good latch and hinge system to transfer the compression load without play.

If the door does not handle this compression load well, then the diagonals will tend to bend the second-tube-up on the door side. If this tube is stiffened by the aluminum skin below it, the local skin loads (near where the diagonals connect) can be higher than you might want, causing oil canning, etc.
Another great point Ken, I am concerned about the door cut-out on the left side. I have considered gusseting the triagle braces in the frame there with some thin steal plate welded in, but I cant decide if it is necessary or not, I probably should just do it. It seems like everything I do just adds more weight, and that is becoming a growing concern as I tally things up.

I had not thought about adhesives in addition to rivets. Some quick research revealed some very appealing products that not only increase joint strength, but provide the corrosion barrier necessary when attaching steal to aluminum sheeting. This might be as good or better then zinc chromate paint. BMW is doing this in their cars so it cant be all bad.

Thanks again for the great comments and encouragement, I am purposefully not buying more material so I'm not working in the garage when I should be studying for finals...
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