Instructions
Plan out your toy carefully. Determine the size and number of gears you need. Ensure that all the gears can fit together so that your toy will move when you turn the gears.
Place a number of pegs out that are big enough to move the gear when turned. If you're using a plastic play set, it should come with these pegs. If not you may have to purchase them from a hardware store.
Arrange the pegs in any order, but ensure that you leave exactly enough room so that the teeth of gears interlock and move. Play sets are designed to turn no matter where you place the gears, but your homemade play set might need some tweaking in order to work.
Turn the gears by hand. You can stack these gears in different combinations and make a structure of moving parts. When one gear is turned, the rest will also move. This can create a nearly endless number of different toys.
Attach objects to the end of gears to create different objects. You can use glue or other adhesives to modify your play set and make specific objects. For example, use a few pipe cleaners to make a moving toy clock.