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."

Writer: caradiodoc
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.

Writer: Verruckt
Date: Oct 3 2013 6:30 PM

Green Venn Diagram

METAMIA is a free database of analogy and metaphor. Anyone can contribute or search. The subject matter can be anything. Science is popular, but poetry is encouraged. The goal is to integrate our fluid muses with the stark literalism of a relational database. Metamia is like a girdle for your muses, a cognitive girdle.