Most standard 60HZ AC motors come in approximately 3600 RPM or 1800 RPM. The barrel sander needs to spin at about 30 RPM. To achieve this, the following approximate pulley sizes will be used:
- 1800 RPM motor
- Shaft to 2″ Pulley
- Belt to 7.5″ pulley
- Shaft to 1.75″ pulley
- Belt to barrel (approx 23″)
- End Result is approx 30 RPM
(This was from memory so might be fractionally off).
Here is a render of the pulley assembly (draft):