How does a washing machine work?
A washing machine doesn't scrub your clothes. It lifts them and drops them about once a second, then spins them so hard the drum wall pushes 400 times harder than gravity. Take one apart in 3D and see why it shakes, walks and loves concrete.
▶ Play with it · Read the 60-second explainer · Watch the 40-second video
- A drum inside a drum. A front-loader has a perforated steel drum that spins inside a still outer tub that holds the water. The tub hangs on springs, sits on dampers and carries concrete. A motor turns the drum, directly or through a belt, while valves, a pressure sensor, a heater and a pump handle the water.
- Clothes get clean by falling. Lifters carry the wet clothes up the side and gravity drops them back through the water, about once a second. Above the critical speed ω = √(g/r), about 60 rpm for a 50 cm drum, they would stick to the wall, so machines wash at 40 to 55 rpm.
- Detergent grabs grease by its tail. Surfactant molecules have a water-loving head and an oil-loving tail. The tails dig into grease, roll it up and carry it away inside a micelle. Warm water and enzymes help; hard water's calcium fights back, so powders add a builder to catch it.
- The spin: 400 times gravity. To swing clothes in a circle the drum wall must push them with a = ω²r. At 1,200 rpm that is about 4,000 m/s², roughly 400 g. Water has nothing pushing it round, so it flies straight out through the holes. Faster spins leave less water, but each step gains less.
- Why washers shake and walk. A 1 kg clump of wet clothes at 1,000 rpm pulls on the drum with about 2,700 N. Springs, dampers and 20 to 25 kg of concrete keep the tub from passing that to the floor. The machine checks for imbalance, spreads the load or spins slower, and if too much force still gets through, it walks.
- Heating is the big energy cost. Warming 15 litres from 20 to 40 °C takes about 0.35 kWh, far more than turning the drum. A cold wash saves most of the energy. Front-loaders use about 45 to 60 litres a cycle; top-loaders, which float the clothes, often 100 to 150.
| Term | Meaning |
|---|---|
| Drum and tub | The perforated steel drum holds and spins the clothes; the still outer tub around it holds the water. |
| Lifters | Ribs inside the drum that carry clothes up so they can fall back through the water. |
| Critical speed | The drum speed at which clothes stay pinned to the wall all the way round: ω = √(g/r), about 60 rpm for a 50 cm drum. |
| Surfactant | A molecule with a water-loving head and an oil-loving tail: the working part of soap and detergent. |
| Micelle | A tiny ball of surfactant molecules, tails in and heads out, that can carry oil away in water. |
| Centripetal acceleration | The push towards the centre that keeps something moving in a circle: a = ω²r. |
| Resonance | The speed at which a tub on springs naturally shakes the most, around 200 rpm in a front-loader. |
| Counterweight | Concrete bolted to the tub so an uneven load moves it less. |
| Specific heat | The energy to warm 1 kg by 1 °C: 4.19 kJ for water, which is why hot washes cost so much. |
From beating clothes on river stones to drums that spin 1,000 times a minute: the machine that gave people back their washing day.
- 1797 · America's first washing patent, lost in a fire (Nathaniel Briggs, New Hampshire, USA)
- 1832 · A boiler that saved lives (Kitty Wilkinson, Liverpool, England)
- 1876 · A woman's washer at the World's Fair (Margaret P. Colvin, Battle Creek, Michigan, and Philadelphia, USA)
- 1890 · The world's biggest open-air laundry (The dhobis of Mumbai, Mahalaxmi, Mumbai, India)
- 1907 · Electric motors take over the turning (Hurley Machine Company and the 1900 Washer Company, Chicago, Illinois, and Binghamton, New York, USA)
- 1937 · The first automatic washing machine (Bendix Home Appliances; John W. Chamberlin and Rex E. Bassett Jr., South Bend, Indiana, USA)
- 1946 · The washday miracle (David Byerly and Procter & Gamble, Cincinnati, Ohio, USA)
- 1989 · Washing machines arrive in Indian homes (IFB, Videocon and others, India)
The full story, with 30 moments, charts, people and 37 sources: glassbox.how/e/washerclear/history. The data lives in history.json.
Made with the Glassbox studio from this box's storyboard (window.glassbox.director). Free to reuse under CC BY 4.0.
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|---|---|---|
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| File | What |
|---|---|
index.html, css/app.css |
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js/app.js, js/stage.js, js/ui.js, js/kit.js |
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