Education Gears

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When were gears first invented? Gears date back to the 3rd century B.C. when Greek inventors used them in water wheels and clocks. Sketches of various gear types from around this time can be found in Leonardo da Vinci's notebooks. How does a gear work? Each time power is passed from one gear wheel to another, you can choose to increase speed, force, or change direction. Here's how: • Increase Speed: When two gears are connected and the first one has more teeth than the second (typically larger), the second gear turns faster but with less force. For example, if the red gear (24 teeth) is turned, the blue gear (12 teeth) will spin twice as fast but with half the force. • Increase Force: If the second gear in a pair of gears has more teeth than the first (larger), it turns slower but with more force. Turning the blue gear makes the red gear turn slower but with greater force. • Change Direction: When two gears mesh together, the second one always turns in the opposite direction. If the first gear turns clockwise, the second gear must turn counterclockwise. Specially shaped gears can also be used to change the angle of a machine's power output. In cars, for instance, the differential (a gearbox) uses a cone-shaped bevel gear to turn the driveshaft's power through 90 degrees and turn the rear wheels. What's the catch? You might think gears are incredibly helpful, but there's a trade-off. If a gear gives you more force, it must give up speed at the same time. If it gives you more speed, it has to sacrifice force. That's why when going uphill in low gear, you have to pedal much faster to cover the same distance. When cruising on flat ground, gears give you more speed but reduce the force of your pedaling by the same amount. Whenever you gain something from a gear, you must lose something else to make up for it.