LEC Suspension & Steering 2 — Questions and Answers
Question 1: What is the primary function of the equalizer bar in a locomotive truck suspension?
- To connect the drawbar to the frame
- To distribute weight evenly between adjacent axles (Correct answer)
- To limit lateral movement of the bogie
- To absorb traction motor torque
Correct answer: To distribute weight evenly between adjacent axles
The equalizer bar connects adjacent axle journals and redistributes weight so both axles share the load more evenly over uneven track.
Question 2: Which condition would most likely cause hunting oscillation in a locomotive at speed?
- Worn wheel flanges and excessive flange clearance (Correct answer)
- Over-tightened journal box lids
- High ballast tamping quality
- Freshly machined wheel treads
Correct answer: Worn wheel flanges and excessive flange clearance
Worn wheel profiles with excessive clearance reduce the self-centering conicity effect, allowing the wheelset to hunt (oscillate laterally) at higher speeds.
Question 3: A locomotive's truck is said to have 'rock and roll' motion. What does this describe?
- Longitudinal pitching over joints
- Combined lateral rocking and vertical rolling of the car body (Correct answer)
- Torsional twist of the main frame
- Vertical bounce at the coupler
Correct answer: Combined lateral rocking and vertical rolling of the car body
Rock and roll refers to simultaneous lateral (rocking) and rotational (rolling) oscillation of the locomotive body on its suspension.
Question 4: What is the purpose of the snubber (or friction damper) in a locomotive suspension system?
- To increase spring preload
- To prevent axle overheating
- To dampen vertical oscillations and prevent excessive bouncing (Correct answer)
- To align the truck with the rail
Correct answer: To dampen vertical oscillations and prevent excessive bouncing
Snubbers provide friction or hydraulic damping to dissipate energy from spring oscillations, preventing the locomotive from bouncing excessively.
Question 5: During a pre-departure inspection, you notice one side of the locomotive body is visibly lower than the other. What is the most likely cause?
- Asymmetric fuel load only
- Failed or collapsed suspension spring on the low side (Correct answer)
- Incorrect tire pressure
- Loose drawbar pin
Correct answer: Failed or collapsed suspension spring on the low side
A broken or collapsed suspension spring on one side removes its load-bearing contribution, causing that corner of the locomotive body to sink lower.
Question 6: What does the term 'truck center spacing' affect regarding locomotive dynamics?
- Maximum fuel capacity
- Coupler height above rail
- Ride stability and curve negotiation geometry (Correct answer)
- Traction motor gear ratio
Correct answer: Ride stability and curve negotiation geometry
The distance between truck centers determines how the locomotive body pivots on curves and influences the vehicle's dynamic stability and overhang.
Question 7: Which type of suspension spring arrangement is most commonly used in modern locomotive primary suspension?
- Leaf spring packs
- Coil springs (helical springs) (Correct answer)
- Air bellows only
- Rubber torsion bars
Correct answer: Coil springs (helical springs)
Modern locomotives predominantly use helical (coil) steel springs in the primary suspension between the axle journal and the truck frame for their consistent load-deflection characteristics.
LEC Suspension & Steering 2
What is the primary function of the equalizer bar in a locomotive truck suspension?