SACA Mechanical Power Transmission 5 — Questions and Answers
Question 1: A chain drive operates at high speed and begins producing significant noise and vibration. Which maintenance action should be checked FIRST?
- Replace the sprockets immediately
- Check and adjust chain tension and lubrication (Correct answer)
- Increase motor torque output
- Switch to a larger pitch chain
Correct answer: Check and adjust chain tension and lubrication
Noise and vibration in chain drives most commonly result from improper tension (too loose or too tight) or inadequate lubrication — both should be checked first.
Question 2: What is the function of a torque limiter (slip clutch) in a mechanical power transmission system?
- To continuously vary the output torque
- To disconnect the load when torque exceeds a preset value, protecting equipment (Correct answer)
- To increase torque at low speeds
- To synchronize two rotating shafts
Correct answer: To disconnect the load when torque exceeds a preset value, protecting equipment
A torque limiter automatically disengages or slips when torque exceeds its set point, protecting downstream components from overload damage.
Question 3: Which bearing type is best suited for applications with both radial and axial (thrust) loads simultaneously?
- Deep groove ball bearing (Correct answer)
- Needle roller bearing
- Cylindrical roller bearing
- Thrust ball bearing
Correct answer: Deep groove ball bearing
Deep groove ball bearings can handle combined radial and moderate axial loads, making them the most versatile and commonly used bearing type.
Question 4: In a helical gear pair, why does axial thrust force develop?
- Due to the tooth surface roughness
- Because the angled tooth helix generates a force component along the shaft axis during meshing (Correct answer)
- Due to thermal expansion of the gear material
- Because helical gears always operate at higher speeds
Correct answer: Because the angled tooth helix generates a force component along the shaft axis during meshing
The helical tooth angle causes the mesh force to have an axial component proportional to the helix angle's tangent, requiring thrust bearings to react this force.
Question 5: What is the primary advantage of a toothed (synchronous) belt over a standard V-belt in a precision positioning application?
- Lower cost per foot of belt
- No slip between belt and pulley, providing accurate speed and position synchronization (Correct answer)
- Higher speed capability at all loads
- Better performance at elevated temperatures
Correct answer: No slip between belt and pulley, providing accurate speed and position synchronization
Synchronous belts have teeth that mesh with pulley grooves, eliminating slip and providing a precise 1:1 relationship between input and output rotation.
Question 6: A gearbox nameplate states an L10 bearing life of 20,000 hours. What does L10 life mean in this context?
- The gearbox will last exactly 20,000 hours
- 10% of identical bearings will fail before 20,000 hours of operation (Correct answer)
- The bearing requires lubrication every 10,000 hours
- The bearing can carry 10 times the rated load for 2,000 hours
Correct answer: 10% of identical bearings will fail before 20,000 hours of operation
L10 (or B10) life is the time at which 10% of a large population of identical bearings would be expected to fail, meaning 90% survive to that point.
Question 7: When two meshing spur gears have different numbers of teeth, which property is the SAME for both gears?
- Pitch diameter
- Rotational speed
- Tooth pitch (diametral pitch or module) (Correct answer)
- Number of teeth
Correct answer: Tooth pitch (diametral pitch or module)
Mating gears must have the same diametral pitch (or module in metric) for their teeth to mesh properly, even though their diameters and speeds differ.
SACA Mechanical Power Transmission 5
A chain drive operates at high speed and begins producing significant noise and vibration.
Which maintenance action should be checked FIRST?