The winding machine

Each of the four cable lines has a corresponding set of three sheaves in the carbarn attached to the museum. The three are known as an idler sheave (the closest set of wheels), a driving sheave (the second large set of wheels on each line), and a tension sheave (the furthest back). These three sheaves are used to move a single loop of cable through the underground channels.

According to the museum, "each cable has its own electric motor, which turns the driving sheave by means of a gear reducer. Each gear reducer contains three pairs of gears, which allow the sheave to turn at a slower speed than the motor.

The driving and idler sheaves work in conjunction to move the cable under the streets. The motor powers the driving sheave, which moves in the opposite direction from the idler sheave, which offers more surface contact for the cable, according to the museum. "As the cable loops in a figure-eight pattern, there is more friction on the cable, and the friction between the cable and sheaves allows the cable to move."