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How Washing Machines Work


Drive Mechanism
Gearbox, pump, tubs and rubber seal
Gearbox, pump, tubs and rubber seal

The drive mechanism on a washing machine has two jobs:

  • To agitate the clothes, moving them back and forth inside the wash tub.
  • To spin the entire wash tub, forcing the water out.

There is a really cool gearbox that handles these two jobs, and it uses the same trick as the pump does. If the motor spins in one direction, the gearbox agitates; if it spins the other way, the gearbox goes into spin cycle.

First, let's see how everything is hooked up:

In this picture, the frame has been removed. You can see the pump mounted to the outer tub, and the gearbox, which holds the inner tub. A piece of rubber seals the outer tub to the gearbox. The inner tub is mounted to the gearbox on the other side of the seal.

Inner tub
Inner tub

The inner tub has been removed from the outer tub in the picture above. It is resting on the gearbox, and the plastic agitator is visible in the center of the tub.

Gearbox
Gearbox

Here you can see the top side of the gearbox with the seal cut and the inner tub removed. The inner tub bolts to the three holes in the flange of the gearbox. You can see from the buildup of crud on top of the gearbox that it has been exposed to wash water for many years. A hollow tube extends from the center of the gearbox. Inside this tube is a splined shaft -- the spline on top of the shaft hooks into the plastic agitator.