The pulleys or cogs fit onto both the wheel and the motor shaft. They allow the timing belt to transfer power from the motor to the wheel.

Two types of pulley:

  • Wheel cog
  • Motor cog

Types of measurement:

  • Width (mm)
  • No. of teeth (T)
  • High Torque Drive (HTD) – the profile of teeth in the cog. This needs to match your timing belt.

The wheel cog needs to fit on the inside of one or more of the wheels. So for this, you will need a compatible wheel along with 5 or 6 bolts and a retaining plate on the outside. You can buy pulleys in kits that should say which wheel size they go with.

The motor cog needs to fit over the motor shaft. The motor shaft usually has a notch, and then the cog should have 1-4 screws which go between the teeth. You also want to make sure your belt has the same width as your cogs.