I was wondering how the rubber bands many people use on the DR4B is used to power the lift. Also what are other common uses of rubber bands.
On lifts, rubber bands usually act like energy storage devices. Energy is stored in rubber bands when they are stretched. When the robot is low, the rubber bands are in a stretched condition (storing energy). When the robot needs to lift up, the rubber bands are contracting and therefore contributing their energy to assist the motors during lift. When the robot lowers, gravity helps the motors lower the robot, and this descent helps stretch the rubber bands again and thus stores energy in them again. When used this way, rubber bands help smooth out the stress on the motors.
Yup. You can think of it in terms of forces if you'd prefer, but you get to the same spot either way. Here are a few other uses:
As for uncommon uses, there is a really awesome robot that runs off of entirely potential energy stored in elastics; no batteries, no brain, no motors. It could run a fairly nice autonomous routine for In the Zone before losing its energy. I think it's the coolest thing I've seen made with VEX EDR parts. There is a video somewhere on the forum.
A non robot use is to put them on the end of a tool to get more grip on a stripped screw head.