Leonel

Just a quick suggestion.I think it would be aemsowe if motors got a second mode, where instead of moving the frames in the direction of the arrow, the motor and all frames attached to the motor move in the opposite direction.  You could even change the arrow on the motor from green to red to indicate the mode.This would allow you to make tracks out of frames, and have motors travel along them.  It would also make for more compact caterpillar engines (the ones that allow you to move things indefinitely in a given direction).Elevators made this way would look wicked cool as well, and you could put the controls for the engine on the same part that it makes move.