WTMA Belt and Chain Drives 2 — Questions and Answers
Question 1: An idler pulley in a belt drive system is primarily used to:
- Increase the speed of the driven pulley
- Maintain proper belt tension and prevent sagging (Correct answer)
- Reverse the direction of belt travel
- Reduce friction between belt and pulley
Correct answer: Maintain proper belt tension and prevent sagging
An idler pulley is a non-driven, freely rotating pulley that maintains proper belt tension and guides the belt path without transmitting power itself.
Question 2: In a compound belt drive, power is transmitted through:
- A single belt connecting all pulleys at once
- Multiple belts connecting intermediate shafts in sequence (Correct answer)
- A chain and belt combination
- Hydraulic coupling between pulleys
Correct answer: Multiple belts connecting intermediate shafts in sequence
A compound belt drive uses intermediate shafts with multiple pulleys and belts connected in series, allowing large overall speed ratios that a single belt drive could not achieve.
Question 3: Which type of chain is most commonly used for mechanical power transmission in machinery and bicycles?
- Roller chain (Correct answer)
- Leaf chain
- Bead chain
- Coil chain
Correct answer: Roller chain
Roller chains use cylindrical rollers that engage sprocket teeth smoothly and efficiently, making them the most widely used chain type for power transmission.
Question 4: The pitch of a chain is defined as the:
- Height of the chain links above the sprocket
- Width of the chain measured across the links
- Center-to-center distance between adjacent link pins (Correct answer)
- Number of links per foot of chain length
Correct answer: Center-to-center distance between adjacent link pins
Chain pitch is the center-to-center distance between adjacent pins, and it must match the sprocket tooth spacing exactly for the chain to engage properly.
Question 5: A step pulley (cone pulley) arrangement allows the operator to:
- Automatically increase belt tension under load
- Change the speed ratio by moving the belt to different diameter steps (Correct answer)
- Drive multiple machines simultaneously with one belt
- Reverse the drive direction without stopping
Correct answer: Change the speed ratio by moving the belt to different diameter steps
A step pulley has multiple diameters stacked together, and moving the belt to a different step changes the pulley diameter ratio, thereby changing the speed ratio.
Question 6: A 6-tooth sprocket drives a 24-tooth sprocket. The driven sprocket rotates at what fraction of the driver's speed?
- Four times faster
- The same speed
- One-quarter the speed (Correct answer)
- One-half the speed
Correct answer: One-quarter the speed
Speed ratio for chain drives = driver teeth / driven teeth = 6/24 = 1/4, so the driven sprocket turns at one-quarter the driver's speed.
Question 7: What is a major disadvantage of belt drives compared to chain drives under heavy loads?
- Belts require constant lubrication
- Belts can slip or creep under heavy or sudden loads (Correct answer)
- Belt drives are significantly noisier
- Belts are considerably more expensive to purchase
Correct answer: Belts can slip or creep under heavy or sudden loads
Belt drives depend on friction to transmit power and can slip or creep when loads exceed the belt's grip, while chain drives engage teeth positively and cannot slip.
WTMA Belt and Chain Drives 2
An idler pulley in a belt drive system is primarily used to: