"Richard Smith" wrote in message ...

"Jim Wilkins" writes:

This is a half section of my present gantry hoist track splice
design. C is the 4" channel, V the 3/8" thick central splice plate
between the channels, H the 3/8" thick horizontal splice plate under
the tension flanges and A the angle iron splice above the compression
flanges.

My question is how to weld the inverted T joint between V and H. I
think an inside fillet weld will deform H upward and require grinding
off the sharp and square lower corners of the channel. Is a row of
plug or slot welds in H a reasonable alternative to avoid distortion
and interference?

The 6" high vertical center plate V alone has nearly the same Ixx as
the two channels so I don't think welding it to H is essential but
connecting them should make the joint stiffer and one-man assembly
easier. The angle A on top bolts to V and C afterwards, and gives the
central hanger shackle pin more bearing area than V alone would.

VA
VA
VA
VAAAAAA
VCCCCCC
VC
VC
VC
VC
VC
VCCCCCC
HHHHHH

Is what you aim for structurally necessary or helpful is a good first
question given the work involved...

OK - using your notation and adding W for weld


...
VC
VC
VCCCCCC
WHHHHHW

So you now have the "H" as two strips with the inner edge bevelled
about 30deg.
Set with a root gap at least equal to the middle "V" plate. Wider and
you "get" some of the "C" channel.
Weld-up. Left and right corners and if necessary middle run for first
layer, then fill.

If "H" is a tension "doubler", not otherwise part of the beam "Second
Moment of Area", then just fillets at the ends would do?
Maybe small fillets along sides, out to edges of the "C" (channel)
sections?

-------------------
I was expecting to do just that until I cleaned up the rusty channels and
found that the flanges are square to the web and a one-piece H plate fits
flush on both sides.

This with an abrasive fiber pad stripped the rust remarkably fast and
effectively and was easier to control than a 7" angle grinder.
https://www.harborfreight.com/air-an...der-93629.html

The 100kg track and hoist assembly has to come apart for handling and
storage so the channels can't be welded to the splice.

If the angle between H and V initially matches the outsides of the channel,
would it increase or decrease after filling the gap?

If the angle opens a little the channel would still bear solidly on H at the
root which may be acceptable. If the angle closes the channel will contact H
at the outer edge and shift under load. I don't have a press large enough to
bend 3/8" plate.

I considered plug welds assuming I could fill a 3/8" hole in one pass and
the weld would shrink symmetrically as it cooled, and the surrounding solid
metal would minimize distortion.

The plates and channels would be clamped together with a gap between the
channels under the weld. I could stop drilling and filling if the plates
began to warp out of alignment.