Friday, February 13, 2009

The Fire Piston

Doesn't look like much, but it's actually way cool ->
(click on picture to see it work)

The fire piston is a clever little device for starting a fire when you're say, in the woods and don't want to use a match. Basically, it's a small, handmade piston and cylinder. You place some easy to ignite tinder in a cavity in the end of the piston and smack the piston down inside the closed cylinder. The air inside heats up and viola! the tinder ignites.

Sounds simple, and it is, but actually making one took more time and care than I expected. I used a number of different materials for the piston and found that I could make a working piston out of either hardwood or hard plastic. The tricky part was making a good seal, and making the cylinder end air tight.

The fire piston demonstrates the ideas of 19th century scientists Rudolph Clausius, James Joule, and Julius Meyer. Basically, it shows the relationship between work and heat. Work and heat are the same thing, said those scientists, which was in contrast to the then current notion that heat was a "thing," a mysterious quantity called phlogiston or caloric. Nope, said Clausius, heat is simply the what happens when you do mechanical work in a closed system.

See a movie of my fire piston in action at

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