Polycord stretchers

[Amit3075]

Out team is based in Israel, so we will search the stores for this item. Thanks!

[M. Mellott]

McMaster also sells a Welding Kit for Urethane Belting which includes a unique clamp. This clamp holds both ends of the belt together while the belt is mounted on the pulleys. A modified soldering iron/plate is inserted between the ends (which melts both ends at the same time), then the iron is removed and the clamp squeezes and holds the melted ends together (note that while the belt is under tension, the joint is not while cooling/curing). After sitting sqeezed together for 5 minutes, the belt is supposed to be at partial strength and the clamp can be removed...just trim off the flash. The belt is at full strength in about an hour...or less in an emergency.

Please note that we did NOT pay the $700+ that McMaster charges...I don't recall where we got our kit, but it was about $100.

[Mike Marandola]

Like JesseK said, it is very important to use the manufacturer's data regarding belt length. Instead of using a welding kit we just melt both ends at the same time using a small butane torch and then press them together. The downsides to this method are that you won't be able to do it in the pit and it sometimes requires two people (an extra person to turn off the torch). To clean up the flashing, rolling the belt on a bench grinder works like a charm.

[JCharlton]

Originally Posted by Mike Marandola

Instead of using a welding kit we just melt both ends at the same time using a small butane torch and then press them together. The downsides to this method are that you won't be able to do it in the pit ...

I've said it before and I'll say it again: avoid the use of open flame with urethane belts, the fumes are not good. Instead - why not use a heat gun? Works just a well, won't fume, and you can use it in the pits. Expose just the ends of the cord from behind a shield of scrap, the ends will melt like a marshmallow when they're ready to connect.

[Mike Marandola]

Originally Posted by JCharlton

I've said it before and I'll say it again: avoid the use of open flame with urethane belts, the fumes are not good. Instead - why not use a heat gun? Works just a well, won't fume, and you can use it in the pits. Expose just the ends of the cord from behind a shield of scrap, the ends will melt like a marshmallow when they're ready to connect.

Thanks for the idea, I will try it out. Are there not fumes from any method that melts the urethane at the same temp?

[Tristan Lall]

Originally Posted by Mike Marandola

Thanks for the idea, I will try it out. Are there not fumes from any method that melts the urethane at the same temp?

Not necessarily. Flames will tend to cause chemical reactions and melting, while lower-temperature heat will mainly melt it.

A science lab hot plate (with a protective piece of metal on top) makes a good instant urethane melter for this application. I have never encountered objectionable fumes using that method.

[VioletElizabeth]

I seem to remember my team making a jig, placing the two ends of the cord in the jig, melting it, then clamping the top half down. This was my freshman year back in 2012 and I wasn't working on it, so my memory is somewhat fuzzy.

As for attaching them, it was the worst part of assembly, we had to get ratchet straps and get several people to make the polycord go on and I think we did it maybe twice, because it was such a pain we tried really hard to avoid it.