The Free Piston Engine, which we’ve placed below the break. It’s a beautiful period piece of mid-century animation and jazz, but it’s also an introduction to these fascinating machines.

The up and down motion of the piston in the cylinder is transmitted ... Museum in London has the largest working Cornish Steam Engine in the World. It was actually built for the site to pump ...

But it also means that mixing the fuel and air can be tricky, which is why diesel engines have specially-shaped pistons. A diesel engine's piston head looks like someone took a scoop out of the top.