Re: Tensile stregth of bolt. (Trying to learn)

One more question, If I wanted to take my 10 foot sections and
extended them 2 feet to make a 12 fott trailer, would you do it? I
mean, would Just *** welding the tubing fully make it a reliable
joint? Or shoudl I play it safe and just make it a 10 foot trailer?

10' is a very good length for a trailer. If you can live with that, I
think it'd be best.

With that said, you can probably get away with extending to 12', but I
would put the joint in the portion of the trailer behind the axle:
leave the section between the hitch and the axle one piece.

Personally, I'd probably not bother joining two pieces of tube for the
back 2', but add angle, maybe 3' long so it overlaps a foot, then the
strength of the angle helps you rather than relying on the strength of
the joint.

If you decide for looks or load that you want the tube to run all the
way to the back, then I'd do one of the following:

Gind the edges of the tube at an angle almost the full thickness of
tube wall, so just a little flat is left to get the pieces to line up
where they touch. Fill this "vee" with weld. It's simply, quick and
easy if you have a 4-1/2" grinder. If you don't, get one--they really
are that useful.

If that sounds like too much work, then I might tack the sections of
tube together with a couple of rod stubs or bit of scrap here and
there to leave a gap all the way around, then fill the gap with weld.
The big danger here is getting distortion from different shrinking
rates as the metal cooled, since there is nothing supporting the gap.
So if you do this, consider doing an inch at a time on each side of
the tube and then keep going on to the next side, so that you're
putting less total heat into each joint at once. Clamping the whole
mess to an angle to keep it straight as it cools can help too.

Another way to do it might be to use pieces of flat stock or cut-off
scraps of tube, and cut them down so that they just fit inside the
tube. Leave maybe 3/16 to 1/4" between the two tube ends with your
added pieces showing through the gap, and weld these backing pieces in
until you've completely filled the gap.

The advantage of all of these over a plain *** weld is that besides
being stronger in general, if you then grind them flat, you still have
most of your weld strength. Grinding flat would allow you to apply
another piece over the joint, maybe just a 2-1/2x8" piece of 1/8" or
so, without leaving gaps under it where it has to go over a big heavy
weld where a lot of water can collect and rust can start. Ideally,
this added piece would either have the ends tapered to points, or only
be welded on the long sides (along the corners of the tube) to reduce
the stress and metal changes at vertical welds, possibly defeating the
purpose of adding the piece. If the ends are taperd, these added
patches are often called "fishplates". You could also add a short
piece or two of angle along the joint to achieve much the same effect.

--Glenn Lyford
.