After made a little arm robot on a RC vehicle, my little daugher destroyed the servos in less than 5 minutes :-(
I thought of a solution to avoid this and I try to add a belt-type elastic element between the servo and the actuator: it seems to work pretty well but I have not yet test in 'real conditions'.
I also experimented a kind of 'rocker' to simplify the mechanics (no complex joints).
I will try to make at least two RC units to be able to play robot-football with a ping pong ball but we can imagine many applications...
2x geared DC motors
2x micro Servos type SG90
1 elastic (minimum length 20mm)
2x rubber rings (wheels)
3D printed parts: frame, wheels, rocker, pulleys, geared pliers
electronics: your choice
last but not least: a lot of patience!