In B3.1 you don't have a rotation wheel so if you're using that you will have to set the position of the "arms" manually at 0 90 180 -90 0 as shown in the disgram I posted on 6/4. (unfortionately the transfer arm position at 0 (D) is hidden in the diagram.) this way isn't so hard except that you have to precisely place the arms or they will wobble. parent relationship starts at the outermost wheel and work towards the piston. That way you can figure out a way to make piston work harder in low gear when you add a transmission. . . . But this brings up the question of a transmission. A train engine would have to have at least two gears and a way to make it go in reverse. There does not seem any to do that except inline between the steam piston and the transfer arm. Im not sure that bryce can represent this without cheating, but it's something to think about. - MIT eat your heart out.