Tunnel crankshaft

A tunnel crankshaft is a type of crankshaft that is used in a car engine. It looks like a long piece of metal with the shape of a wide 'U'. Inside the 'U' are off-center wheel-like pieces called crankpins. As the engine runs, the crankpins spin around the crankshaft, like kids on a merry-go-round. Each time the crankpins spin around the tunnel crankshaft, the engine's pistons, valves and other parts move and help to make the engine run.