Two-Way Redpower Inchworm Drive

[reptar]

Anybody have a design for one? I can make it go one way okay, but if I attach two drives together, it suddenly won't budge. I want to make nether travel safer, and a frame train would fit the bill, but I cant get it back to the station.

[Air_Gamer]

This is my own design, it simple to build, requiring no logic gates to move.

The motors on the bottom move the centre frames and the top motors over the red alloy wire, which then trigger to top motors to move the whole frame.