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Machines & Mechanisms

How does a zipper work? A zipper is two rows of interlocking teeth and a slider with a Y-shaped channel. See it closing and opening in an x-ray 3D animation. How does a pin tumbler lock work? A cylinder lock is held shut by spring-loaded pin stacks that cross the shear line. See in an x-ray 3D animation how the right key lines up every gap so the plug can turn. How does a speedometer work? A classic speedometer uses a spinning magnet that drags an aluminium cup with eddy currents against a hairspring. Modern cars count pulses from a wheel sensor instead. How does a piano key make a sound? A piano key is a lever that throws a felt hammer at the string. Just before it hits, the escapement lets go, so the hammer flies freely, bounces straight back and lets the string ring. A damper lifts off while the key is down. How does a sewing machine make a stitch? A sewing machine uses two threads. The needle pushes a loop of the top thread under the fabric, a spinning hook carries that loop all the way around the bobbin, and when it is pulled tight the two threads lock together inside the fabric.