Millwright Certification Power Transmission and Drive Systems 2 — Questions and Answers
Question 1: What is the main advantage of a synchronous (timing) belt over a standard V-belt?
- Lower cost
- No slip — positive engagement between belt teeth and sprocket (Correct answer)
- Higher speed capability only
- Requires no tensioning
Correct answer: No slip — positive engagement between belt teeth and sprocket
Synchronous belts mesh with toothed sprockets for positive, slip-free power transmission, maintaining exact speed ratios.
Question 2: A chain drive produces excessive noise and vibration. The MOST likely cause is:
- Incorrect lubricant viscosity
- Worn or elongated chain links (Correct answer)
- Oversized sprockets
- Mismatched chain pitch and sprocket pitch
Correct answer: Worn or elongated chain links
A worn or elongated chain increases pitch length, causing it to ride up on the sprocket teeth and creating impact noise and vibration.
Question 3: Which type of gear is used to transmit power between shafts that are parallel but offset?
- Bevel gear
- Helical gear (Correct answer)
- Worm gear
- Miter gear
Correct answer: Helical gear
Helical gears on parallel shafts (including double helical/herringbone) transmit power smoothly between parallel shafts, including offset parallel arrangements.
Question 4: When installing a flexible jaw coupling, the correct gap between the two hubs is determined by:
- The manufacturer's specification for axial float (Correct answer)
- The operator's preference
- The diameter of the coupling bore
- The rotational speed of the shaft
Correct answer: The manufacturer's specification for axial float
The axial gap (also called float or end play) between jaw coupling hubs must match the manufacturer's specification to allow for thermal expansion and shaft movement.
Question 5: To increase the speed ratio of a V-belt drive without changing the belt length, a millwright should:
- Increase the diameter of the driver sheave (Correct answer)
- Decrease the diameter of the driver sheave
- Increase the diameter of both sheaves equally
- Add a second belt alongside the first
Correct answer: Increase the diameter of the driver sheave
Increasing the driver (input) sheave diameter increases the peripheral speed difference, resulting in a higher speed ratio at the driven sheave.
Question 6: What is 'backlash' in a gear set?
- The clearance between mating gear teeth (Correct answer)
- Gear tooth breakage from overload
- Misalignment between gear shafts
- Noise caused by bearing failure
Correct answer: The clearance between mating gear teeth
Backlash is the small clearance between mating gear teeth, necessary for lubrication and thermal expansion but excessive backlash causes impact loads.
Millwright Certification Power Transmission and Drive Systems 2
What is the main advantage of a synchronous (timing) belt over a standard V-belt?