Round Belting - Solid vs. Hollow, Polycord vs. McMaster

[Ian Curtis]

Originally Posted by artdutra04

Don't waste $500 on the McMaster "welding kit"; the solid core polycord can be welded with just a lighter. Just cut the cord 10% shorter than the actual distance necessary, melt the ends with the lighter, stick them together (use the inside of aluminum angle to keep them lined up), and wait five minutes. Now use a razor and trim off all the globs of melted cord around the joint so it is smooth and wait another half hour to let it cure and achieve full strength.

We found out on Saturday that 10% is pretty tight, and you can safely get away with much less. We had round belting on 3" diameter PVC rollers with grooves laid in for the belting to follow. These rollers were mounted on 1/2 steel shafts in plywood "bearings." The plywood supports were about 25" apart. Four urethane belts at 10% did a number of the shafts. We could clearly see the shafts bowing, and our 18V Dewalts had a hard time turning the assembly. To alleviate some tension, we moved the rollers closer together. The distance around the rollers was originally measured at 55 inches (so we cut the belts to be 49.5" long. We moved the rollers a good 2" closer, and found the belts were still taut, and had no problems with belts slipping, even when we jammed in seven balls and put a board across the top opening.

In short, we found cutting the cord at 10% shorter to be pretty aggressive. At 3% shorter (instead of 10%) the balls moved just as well, and the whole assembly ran much smoother.

Art, is there any reason for the half hour cure time? After five minutes or so ours were cool to the touch, and we haven't had any fail that were joined using your welding method.