[Ari Allyn-Feuer]

The forklift trolley is shown in the center, with a pinion gear driven by a 48:1 RS-540 tranny. It grips a rack milled into the surface of the rail the trolley slides on. The rail itself has another motor and a similar rack milled into the channel stock the rail slides in.

Both of them have quadrature encoders (Grayhill 63 series) tracking their movement, and limit switches at the bottom to set them up in the right spot. The righthand operator can press a button and the trolley moves to the proper level for low, middle, or high rungs, or the ground.

Ari.