[RoboChair]

Originally Posted by Paul Richardson

Consider also that you can allow yourself to use weaker material by decreasing the load applied. Adding a spring will add some weight, but it may allow you to save some weight elsewhere (chain weight, motors, and gearbox for example).

Also, if you are having trouble with belts as an alternative to chain, you can also try a simple string winch. You can find cord and wire in long lengths for cheap that are very strong for their weight.

Alternatively you could use a Constant Force Spring such at what McMaster sells.

http://www.mcmaster.com/#constant-force-springs/=whvq22