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Gears
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Gears are just wheels with teeth. If power is provided to turn one gear, that gear
can turn another gear. The teeth on the gear that provides the power (input gear) engage or mesh with a second gear. The teeth on the gears act like tiny levers
and the second gear rotates. The second gear can turn a third gear and the third gear can turn another gear.
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The place where the power enters the system (ex: a motor or a hand crank) is called the input or driver
gear. The place where the power comes out of the system (ex: where a gear turns a wheel) is called the output or driven gear.
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It sounds simple enough,
but the combination of different sizes, types of gears and types of teeth can drastically change the output power to make one car faster than another, give a
bulldozer the power to push, or help a helicopter to fly. Gears are used in tons of mechanical devices. They do several important jobs, but most important,
they provide a gear reduction. With a gear reduction, the output speed can be reduced while the torque is increased.
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The ratio of the rotational speeds of two meshed gears is called the
Gear ratio.
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Gears are generally used for one of four different reasons:
To reverse the direction of rotation.
To increase or decrease the speed of rotation.
To move rotational motion to a different axis.
To keep the rotation of two axes synchronized.
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The teeth in the gears have certain advantages like:
They prevent slippage between the gears. Therefore, axles connected by gears are
always synchronized exactly with one another.
They make it possible to determine exact gear ratios. You just count the number of
teeth in the two gears and divide. So if one gear has 60 teeth and another has 20, the gear ratio when these two gears are connected together is 3:1.
They make it so that slight imperfections in the actual diameter and circumference
of two gears don't matter. The gear ratio is controlled by the number of teeth even if the diameters are a bit off.
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