Polycord welding

[jvriezen]

I've searched CD for poly cord welding info and I think I have the general technique down but they are based mostly on textual descriptions. Here is the technique I'm hearing.

1) Take care, use gloves, and don't get melted urethane on your skin.
2) Cut poly cord to length of about 3-5% shorter than length of run, even though mfgr says 10%.-- 10% is overkill and puts more tension on things than you want and just makes things more of a pain.
3) Joint cuts can be square cut or angle cut (not sure if it matters)
4) Heat/melt both ends by pressing against piece of aluminum, and heating opposite side of aluminum with torch. Or use heat gun, but that would seem to be more messy.
5) using angle alum as a guide to align, press ends together firmly for several minutes, then let set for several hours before using. Seems like a small u-channel or tubing that matches diameter may be even better for aligning.

A couple of questions:

Some writings seem to imply that the tubing should be stretched while welding. Not sure what is meant by this-- the only thing I can think of is that you put it around your pulleys and weld it into its final installation, stretching to make the ends meet-- makes sense if you can't install it otherwise after it is a loop, I guess, but in our case, we can weld separate from the bot and then install with little difficulty (I hope, or am I missing something?)

One poster suggested using a block (of alumninum?) and drilling a hole to match cord diam. and then splitting the block to aid in alignment.

It would be great if someone who has proven success with welding solid core could post a easy to follow video on how to do it (without buying a welding tool for several hundred dollars!)

Thanks.