[Tom Line]

We used size 25 chain to drive our first stage, with spectra pulling the second up and down.

We used bungee cord to counterbalance the stages the motors didn't have to lift the weight of the them.

One thing to note about using any time of spectra or other line - tieing a knot in it will reduce the strength on the order of 40%. So, for instance, if you had a piece of line with a breaking strength of 500 pounds, and tied a knot in it, the break strength at the point of the knot will only be around 250 pounds. That sounds like a lot, but we managed to break a piece of spectra line with a break strength of over 1000 pounds when we were lifting a trackball and then got hit from the side by another robot (hard). If you can find a local rigger or a West Marine, they can splice the rope for you and eliminate the sharp bends that you'll create by tieing a knot. Or if you can "wrap" the spectra around whatever you're tieing it to several times then tie a couple half hitches, you'll eliminate that problem.

Shock loads are killer. Forces in a 10 mph collision have been measured at over 8 g's in the auto industry. We go a lot faster than that.

Another thing to note is that most spectra will not have a cover on it like your standard "West Marine" line, and that it is very susceptible to chafe. Vectran less so but you will certainly pay through the nose for vectran or any other high-tech line.