Walking Robot- the two candidates (frogbot)

We made a couple models for the frog concept. We first made models that followed our original design, in that a motor would rotate the robot's legs with feet that would lift up the body. We made two models for this concept:

The problem with these two models was that they were two similar to a wheel-like motion and that we weren't sure that the feet would be able to push the rest of the body up. We would definitely need to have a powerful motor for this robot. With these models would also have to change the shape of the body so that it doesn't obstruct the motion but just slides as the legs are pushing off the ground. The other models focus on different ways to get a hopping motion without relying on a circular motion.

This is the first one we came up with. Its legs are attached to the body but they are free to rotate. The leg has a foot that would push off the ground and make the frog jump. To achieve this, we need a motor that pushes the feet at the same time towards the ground, until the whole body is lifted and then brings them back to their original position. Here is a picture of the foam model:
The problem with this model is that the motor moves at the same rate and it would preferable for it to be more powerful when it pushes the legs downward. Professor Berg told us incorporate rubber bands in order to get this "burst of energy" that is needed for a hopping motion. He helped us to come up with this motion module with a rubber band. So as you rotate the oblong piece, it stretches the rubber band and at the point where the maximum distance has been reached, the rubber band helps the bar snap back to its original place. It is this snapping motion that is important for us and we decided to use it to create a hopping motion.
The frog's leg could be the bar that snaps back and after the motor pushes it down towards the floor and quickly moves back towards the body, it would make the frog leap forward. The motor needed for this motion would need to be very powerful so that it can resist against the rubber band.