This was a group project for a mechanical systems design class during my senior year of college. Our task was to make a mechanism that jumped one meter high without any external energy storage (e.g. a person loading springs on the mechanism).
In our design, a motor drives a gear train which moves the jumper's two legs. As the legs move from their original vertical position to horizontal, they stretch rubber bands. In the gear train, we removed certain segments of gear teeth so that when the legs reached horiztonal they would disengage with the motor. This mechanism allowed the rubber bands to release their stored energy, snapping the legs back to vertical (180 degrees from their starting point), and propelling the whole thing into the air.
Since we only had a few weeks to design, build and test, we built as many prototypes as we could, testing out different gear ratios, motors, leg shapes, 3D prints, and elastic materials.
Sometimes had to scavenge for miscellaneous gears
Small motor
Plastic, what can you do
We found that these curved feet worked best - they maintained contact with the ground the longest which caused it to jump straight.
Although our jumper did not achieve the highest jump in the class, we were proud of our design. The release mechanism was one of the most challenging parts of the task and ours was very reliable and functional. Almost all other groups converged on a single, different design whose release mechanism was a rubber band being cut by a blade that was mounted on the jumper.