[Aren_Hill]

Bike's usually have the spring loaded tensioning setup, this is because the chain is only ever going one direction with force, meaning the spring takes up tension on the side that is always slack.

Robot drivetrains dont do this for the reason they run both directions and placing a spring loaded tensioner would yield situations in which the motor would be pulling in chain directly against the spring and when this happened slack would develop in the other areas of the chain run giving increased likelyhood of chain popping off.

Using a spring loaded idler to reduce harmonic bouncing of the chain over long spans though is a good use though.