Bicycles again. Just because extensible cranks are staples of the perpetual motion brigade, doesn’t mean they aren’t useful.
Today’s invention is a set of extensible crank arms for a bicycle.
The right crank is shown as telescoping outwards on the downstroke to provide a greater turning effect. The left one is shown having withdrawn to normal length -to allow the pedals not to hit the ground.
Controlling this lengthening might be done using a cam on the frame or, more simply, by allowing the power stroke to push the pedal outwards and having an internal, longitudinal spring return it on the upstroke.
The riding action would be a little more asymmetric than normal, but the effect on hillclimbing would be significant.