I finally found some time to return to the "transformer" styled mechanism. This is version 3 which is the first rolling / walking / rolling mechanism.
To roll, I added the wheels, tires (33mm ID, 3.5mm section, o-rings) and axles.
The mechanism is propelled by an N20 30rpm 6vdc gear motor, powered by a 3.7vdc 100ma LiPo battery, and uses a compression spring (32mm length, .5mm section, 8mm OD) in the transmission mechanism. The remaining 24 (unique) components are entirely 3D printed.