In existing toys, there were a couple of examples I looked at. One was the flipping dog toy, which used a rack and pinion to compress a spring. The pinion (the gear) only has teeth in a specific part of the wheel so that when it rotates to the part that has no teeth, the built up spring tension is released and the rack impacts the ground and makes the dog jump!
One of the limitations of this design is that you can only jump at one height, so I looked into a scissoring mechanism that would give me this level of control:
This design led me to the delta robot, which consists of three main arms connected at the tip. The three arms allow the tip to move all directions in space. It's not limited to just an up and down motion like the scissoring mechanism above. This mechanism is typically used in 3D printers and "pick-n-place" machines:
My first experiments with 3D printing come in the next post! I start to test different designs, and need to get a bit creative with making my own parts.