A belt moves power between shafts that are too far apart for gears. Pick your pulleys and spacing to get the ratio, the exact belt to buy, and a warning before it starts skipping teeth.
Drawn to scale · slowed so you can follow itBoth pulleys turn the same way — a belt, unlike a pair of gears, never reverses it.
Ratio
2.00:1
156 RPM at the output, with 2.00× the torque.
Belt to buy
This spacing needs a belt of 330.8 mm (110.25 teeth). Belts come in whole teeth, so pick one and set your centres to match:
110T belt119.62 mm centres
111T belt121.12 mm centres
Leave slotted holes or a tensioner — a little adjustment beats an exact number.
9.5 teeth engaged on the small pulley. Comfortably above the 6 you need to stop the belt skipping.
