How things work
How a washing machine works
A front-loading washer with one side and half of the front cut away. The clothes are not animated by hand: where they go is worked out from how fast the drum is turning.
Run a cycle
What the drum is doing
- Pull at the drum wall
- 0
- Clothes
- at rest
- Water in the tub
- 0 cm
- Clothes stop falling at
A lump of washing going around a circle needs an inward pull, and that pull grows with the square of the drum's speed. At the top of the drum, gravity supplies it. Once the drum is fast enough that gravity alone is not enough, the wall has to push as well, and the washing never leaves it. For this drum that happens just under 70 turns a minute.
What is simplified
- This machine has a belt drive: a motor under the tub turns a large pulley on the drum shaft. Many newer machines have no belt and mount the motor directly on the back of the drum.
- The clothes are a few soft lumps that follow the drum wall and the paddles exactly, then fall freely. Real washing slides, drags and tangles, so it falls a little earlier and less neatly.
- At spin speed the drum turns about 20 times a second, faster than a screen can show. Above 90 turns a minute it is drawn turning more slowly, with a blur. The forces and the readouts use the real speed.
- The holes in the drum are drawn larger and fewer than real ones so you can see through them, and the water in the hoses is shown as beads.
- Many machines also have a heating element in the bottom of the tub, a filter on the pump, and a second valve for the other drawer compartments. They are left out.
- A real spin starts gently and checks the balance of the load before going to full speed, and steps the speed up in stages. Here it climbs in one go.
In short
A front-loading washing machine has a perforated steel drum inside a sealed tub that never turns. A valve lets water in until a pressure sensor, fed by a tube of trapped air, says the level is right. During the wash the drum turns slowly, and paddles lift the clothes and drop them back into the water. A pump then drains the tub. In the spin the drum turns past 1,000 times a minute, the clothes press against its wall, and water escapes through the holes. The tub hangs on springs and dampers, with concrete weights, so an uneven load barely shakes the machine.