Fortunat1 wrote:
clare at snyder.on.ca wrote in news:r3k3f35vka26ss9jq6k80m2cr1ef67usun@
4ax.com:


This is tubing, right? Drill a couple of holes and rosette weld, or
plug weld the sleave in place. It is now doing it's job Now weld the
ends of the tubes together. If the weld penetrates into the
re-enforcement sleave, good. If it doesn't the sleave is still in
there providing extra strength to the joint (done properly, the joint
is almost strong enough with just 4 plug welds per end)


This makes sense to me, however, looking in my books, it's stated pretty
clearly that the inner tube should be welded to the outers.
there's a copy of that text he

http://www2.tech.purdue.edu/at/cours...Ac43-13-1B/CH4
_5.pdf

Now, it would seem to me that penetration of the inner tube would add very
little strength at all, particularly if it was a good snug fit. Am I
reading this wrong?


I believe that you have to effectively have a full lap joint weld
between each outer tube and inner tube, AND the joint must be a
truncated cut and not just straight across in order to have sufficient
weld cross section since it's essential that the weld zone be much
stronger than the virgin metal up the tube.

The rosette welds done further up don't contribute that much strength
and are mostly (I believe) to prevent the inner tube from having an
unsupported length that allows "wiggling" of the inner tube in the outer
tube under stress. possibly leading to cracks in the main weld.

John