RCO Training – Mechanical Practice Test

In a belt drive, the belt’s linear speed is the same on both pulleys, so the product of rpm and pulley diameter is constant: n1 × D1 = n2 × D2. Solve for the driven rpm: n2 = n1 × (D1/D2).

Here, D1 is 120 mm and D2 is 240 mm, so D1/D2 = 0.5. With the driver at 1800 rpm, the driven rpm is 1800 × 0.5 = 900 rpm. The larger driven pulley halves the speed, so it rotates at about 900 rpm.