Seven-year old Sawyer wants to know: how does an engine work? We learn about chainsaws from Ashleigh Belrose, an instructor the Center for Technology in Essex, Vermont.
Ashleigh teaches high school students interested in forestry management here in Vermont, where the podcast is based. One of the things she teaches them is how to use a chainsaw. A chainsaw has a simple engine.
"An engine is basically a series of controlled explosions. I know that sounds really scary, but they are controlled, that's the good part. Imagine yourself on a seesaw. If you're sitting on one end, you are going up and down and the force that's driving you, going both up and down, are your legs. Same thing in an engine.
"There's a cylinder, which means basically a hollow soup can shape. There's a piston that's fitted inside that cylinder. The piston is the head that goes up and down. It's air tight (so nothing can get passed it) that's fitted very snuggly inside the cylinder and it moves up and down. The way it does that is through those controlled explosions. That moves it up and down the cylinder and that movement of the piston is translated in different ways to the moving part of the vehicle. That's what makes your vehicle move...one or more pistons in the engine.
"A chainsaw has only one piston. The more cylinders you have, potentially, the more power you have.
"The piston goes up and down in the cylinder. When it goes down, fuel gets sucked in. With two stroke, the intake and exhaust are the same, and the compression and combustion are the same. So you have intake, as your in is coming in, it actually fills up and pushes the exhaust out. And then the compression happens because the piston moves back up in the chamber. All of the fuel that was just taken in is being compressed. When it gets to the top, there is a spark plug. That ignites; that's your power stroke. It pushes the piston back down, more fuel will come in, the exhaust from the last combustion will go out, momentum drives the piston back up to compression and combustion and that's how the engine goes.
"That's slowing it down, but that's the small components between, and that's how the fuel is used in the engine to make those controlled explosions."
-Ashleigh Belrose, Center for Technology Essex
See a video of Ashleigh with her model engine on our Facebook Page.