Belt and Chain Drives Flashcards

If the driving pulley is larger in diameter than the driven pulley, the driven shaft will:

Answer: Rotate faster than the driving shaft

A smaller driven pulley must complete more revolutions to cover the same belt distance as the larger driver, so it rotates faster — acting as a speed increaser.

What is the effect of increasing the center distance between two pulleys in a flat belt drive?

Answer: It reduces belt slip by increasing the arc of contact on the smaller pulley

A greater center distance improves the wrap angle on the smaller pulley, increasing the arc of contact and the friction available to transmit power without slipping.

If a driving pulley's rotational speed doubles while all pulley diameters remain unchanged, the driven pulley's speed will:

Answer: Double as well

The speed ratio is fixed by pulley diameters, so any change in input speed produces a proportional change in output speed — doubling input doubles output.

A mechanic needs to transmit power between two shafts that are slightly misaligned. Which drive system best tolerates this condition?

Answer: Flat belt drive

Flat belts are flexible and can tolerate slight shaft misalignment that would cause rapid wear or failure in rigid drives like chains or gears.

In a timing belt (synchronous belt) drive, the primary purpose of the teeth on the belt is to:

Answer: Prevent slippage and maintain exact timing between shafts

Timing belt teeth mesh with grooved pulleys, preventing slippage entirely and ensuring an exact, fixed speed ratio essential for timing-critical applications like engine camshafts.

Why are chain drives preferred over belt drives in applications subject to heavy shock loads?

Answer: Chains have positive tooth engagement and do not rely on friction

Chains engage sprocket teeth positively and cannot slip, so they reliably transmit power even under sudden heavy shock loads that would cause friction-based belt drives to slip.

A belt drive uses a 4-inch driving pulley at 1,200 RPM connected to a 16-inch driven pulley. What is the output shaft speed?

Answer: 300 RPM

Output speed = Input speed × (Driver diameter / Driven diameter) = 1,200 × (4/16) = 300 RPM.