Mon Prof Augmenté
Rack and pinion
Age 14 · Technology
A round toothed wheel has its teeth sunk into the slots of a flat toothed bar lying under it. When the wheel turns on its axle, its teeth push the bar sideways along a straight line.
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In the picture
- The toothed wheel, called the pinion, turning on its fixed axle
- The curved arrow: the direction the pinion spins
- The meshing teeth: each pinion tooth drops into one slot of the bar
- The straight arrow: the toothed bar travels in a straight line
Examples
- Turning a car’s steering wheel swings the front wheels through a rack and pinion steering box.
- A motor on a sliding gate drives a small pinion along a toothed strip bolted to the gate.
Key takeaways
- A pinion meshed with a rack turns rotation into straight-line movement.
- One full turn of the pinion shifts the rack by the length of the pinion’s circumference.
Quiz: Rack and pinion (Age 14)
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In a rack and pinion, what happens to the motion that goes in?
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The pinion makes exactly one full turn. How far does the toothed bar travel?
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Why can the pinion drive the toothed bar along instead of just spinning on the spot?
The answers, each with its explanation, are in the app. This lesson has left the free week, so its quiz is part of the subscription.
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