Leeson Gear Motor, 90VDC, 30:1 ratio, runs @ 60rpm, 56 lb-in torque.
I think the above has home made welding positioner written on it.
From what I gather, it is not the highest amount of torque (there seem to be lots with about double that) but there is at least one commercial model available that has exactly that.
From reading the rpm needs to be dropped quite a bit further, I was thinking of a belt drive (chain?) with a very large pulley having a large center hole so as to allow for tubing to be dropped through enabling flanges to be welded to pipe.
Knowing next to nothing about electrics, the first questions would be is the above motor appropriate? How complicated is it so as to eventually run off 115v and have control over varying the speed?
Aiming to have about 3rpm and lower final drive. Have to do a bit more reading but that 3rpm may end up being a bit high [bookmarked a lot of builds yesterday, have not had time to read fully and recall there was one with a speed chart on it (diameter v. rpm needed)]