a: piston ~
b: a giant tennis racket
"Microscopically speaking, compressing a gas must involve a surface, let's say a piston, charging into the gas. During this process, the piston is like a giant tennis racket smashing back all the trillions of tennis balls, i.e. the gas molecules, that happen to collide into it."
Date: Apr 15 2017 8:05 PM
a: A piston ~
b: solid coffee can
What: "The pistons are like solid coffee cans that go up and down in the cylinders. When they go down, they suck in air and fuel. When they go up, they squeeze that stuff to one eighth the size, then that mixture gets ignited by the spark plug. There has to be a gap between the pistons and cylinders so it can slide freely, but that gap would let the mixture leak past the piston and become useless as far as generating power is concerned."
Date: Oct 3 2013 6:40 PM
a: Piston ring ~
b: a spring
What: "A piston ring is like a spring. Engine bores are not really round. Manufacturing imperfections, cylinder wear, and head bolt loads make cylinders out of round when you're looking at a micron scale." A discussion of piston rings is in the link.
Date: Oct 3 2013 6:30 PM
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