hss slip connection

huangyhg

hss slip connection
looking for ideas-
i've got hss5x3x1/4.  i need to join the ends of the hss together, keeping both in the same axis.  i need a slip joint between them of about 1 inch.  this joint needs to keep both hss in line, but be allowed to move along their axes.  the slip connection needs to be inside the hss walls.  no exterior connections can be seen.
i was thinking of splitting an hss 3 1/2x2 1/2x3/16 in half, and welding the halves to the inside of the hss5x3.  the next hss then slips over these halves and creates my slip joint.  however, i'm concerned about the corner radiuses of the two different hss lining up.  chances are, they wont.
any other ideas?
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seems to me you could just weld 4 plates to inside of one tube.  the plates would stop short of the tube corners.
how about angles welded to each side inside of one hss with a length protruding to pick up the other?  instead of a split hss inside, can you specify a bent plate that is bent to the inside dimensions and radii of the 5x3?
i thought about the plates on the inside.  my concern is that the only weld holding these plates on is a single bead.  when the hss's want to move out of plane, wont these plates want to rotate about the axis of the bead of weld?  or am i being to concerned about it?
perhaps you could weld 4 - 1/2" dia. smooth steel dowels in each corner.  but that would allow a clear view through the joint which may not be acceptable visually.
what if - in your first idea - you use a hss 3 1/2 x 2 1/2 x 5/16" tube instead - the thicker tube would have a larger corner radius (2t) than the thinner outer tube and you would probably avoid all conflicts there.
you could take a 4"x2-1/2"x1/4" tube and weld a 1-1/2"x1/4" plate to the top and bottom of the short side, making a 4-1/2"x2-1/2"x1/4" tube.  slip it inside of the 5x3x1/4" and weld it.  you may have to use plug welds.  if you weld the 1/4" plates continuous and grind them smooth it should leave a nice finish and not allow your larger tube to have misalignment.