"J.Kahn" wrote in
:

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...Links/Ac43-13-
1
B/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.


OK, I can buy all of that, but I don't know exactly what you mean by
truncated. Are you talking about the profile of the edges of the outer
tube, or do you mean the outer tube must be cut diaganally?