NXT Design of Yoshihito Isogawa
The above design is found in the book, "Lego Mindstorms NXT", by Yoshihito Isogawa. Others have created "inchworms", but Yoshihito's inchworm design is unique for its creativity and efficiency.
As seen in the above close-up, Yoshihito has used a rubber band and NXT parts to create a locking mechanism for both rear and front wheels. This locking mechanism engages and disengages as the worm moves forward, resulting in smooth movement with a minimum of motor thrust.