Basically, there is a string that is fixed to the front arm; as the front arm goes down, the spring attached to the string is extended, and the force of the sprint perfectly counters the force of gravity on the front arm, so the front arm is "floating" in the air.

Uhh may 21316 Team Alpha graciously ask for ur cad for the pulley system? We're trying to experiment with counter spring mechanisms and we cant find a way to change the direction of the string/cable that optimally.

axon