We just learned about the Leaf Spring.
Another part of a steam locomotive is the Driving Wheel.
When the steam power moves the pistons, it is connected to rods that turn the wheels.
Only some of the wheels are connected to these rods, and they are called the driving wheels.
The other wheels are just holding up the train and they turn just because the driving wheels are pulling the train along.
This is the same for most other things with wheels too, like the pedals on a bicycle usually only turn the back wheel of the bike.
(from: wikipedia - driving wheel)
Kid Facts - Blast from the past: Gasket
