On Wed, 16 Apr 2008 07:43:15 -0700 (PDT), stryped
wrote:

I am just thinking here about that trailer. I may never build it but
if
I did get materials and did try to make it out of that 2x2 or 2x3
square tubing, what if I mafe a triangle gusset for each corner on the bottom.
Drilled through the top tubing through the gusset, then installed a
grade 5 carriage bolt or something. Then welded the whole thing also? I
guess I am trying to "over engineer' it. I can weld, but have never had
training. I have never had anything really come apart that I have
welded, but on something like a trailer, I would like to take every
precaution I could.

You never just drill through both walls of structural tubing and put
a bolt through side to side - that collapses the tubing, and when it
is deformed the strength goes away. You need to put a sleeve of pipe
or heavy round tubing through the holes and seal weld the sleeve at
both ends where it passes through the chassis.

This puts the clamping force of the bolt into the sleeve and not the
chassis tubing, and the chassis tubing will retain it's shape and
therefore strength.

If you want to attach something bolted, the other acceptable methods
are welding on a flat strap stock bracket with a hole, or welding a
nut to the rail and attaching with a bolt, or placing the sleeve on
the side of the tubing and welding the sides down...

Fort the corners, I would use fishplates along the sides of the
tubing to overlap the mating welds, not gussets that cut across the
inside of the mating angle.

Fishplates are always cut with a diamond profile on the ends
That spreads out the strength along a longer weld path, straight cut
ends [ ] just move the stress instead of spreading it out.

Hey Stryped: See if there are any Welding or Metal Fabrication or
Industrial Design classes at your local High School Adult Extension,
Community College or University Extension, etc. There are SO many
little details to doing this right, and we'll all get carpal tunnel
from the typing if we try to explain it all.

And if we miss something critical or you don't understand it, you
could still end up with a 'two piece trailer'. Which would be bad.

-- Bruce --