We just learned about the Pulley.
Another part of a machine is a Shaft.
A shaft is a long pipe, rod or pole that is on the inside of some kind of bigger spinning wheel.
This can be part of a gear, sprocket or pulley.
When the gear spins around, it turns the pipe.
In some machines, the pipe is used to move something else farther away from the gear.
Like in a windmill, the big wheel outside that is moving has a long shaft attached to it.
The shaft goes into the building where it is hooked up to other gears to turn them and do something useful like grid up corn into flour.
When the windmill turns, the shaft spins, and the gears inside spin and do the work.
A car also has a shaft. When the car burns up gas it makes a shaft spin which then connects to other shafts that turn the wheels.
(from: wikipedia - shaft (mechanical engineering))
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