Rotary to Random Linear Motion for an automaton

I am creating an automaton that is a seal, with front flippers on a pedestal, and a spinning ball on its nose. I have a need for both rotary motion (to spin the ball) and random distances of linear motion (to control the seal's body). This video simply documents the test build of the concept. I'm pleased that it works. The next step will be to shrink it down and package it so that it can be used in the automaton.