LEC Suspension & Steering 3 — Questions and Answers
Question 1: What is the role of the center plate (center bowl) in a locomotive truck assembly?
- It houses the traction motor cooling fan
- It is the pivot point that allows the truck to rotate under the locomotive body (Correct answer)
- It connects the brake rigging to the truck frame
- It supports the fuel tank
Correct answer: It is the pivot point that allows the truck to rotate under the locomotive body
The center plate acts as the pivot bearing between the locomotive underframe and the truck, allowing the truck to swivel as the locomotive negotiates curves.
Question 2: Lateral side bearers on a locomotive truck are set with a specific clearance. What happens if this clearance is excessive?
- The truck cannot rotate on curves
- Excessive body roll and instability at speed (Correct answer)
- Increased fuel efficiency
- Higher adhesion on grades
Correct answer: Excessive body roll and instability at speed
Excessive side bearer clearance allows too much body roll, reducing ride quality and potentially causing unsafe lateral dynamics at higher speeds.
Question 3: A locomotive engineer reports a 'stiff ride' with harsh impacts over track joints. Which suspension component is most likely at fault?
- Worn center plate liner
- Failed or hardened suspension springs or dampers (Correct answer)
- Loose bolster anchor
- Cracked truck frame
Correct answer: Failed or hardened suspension springs or dampers
Failed or hardened springs and dampers lose their ability to absorb track irregularities, transmitting impacts directly to the locomotive body as a harsh ride.
Question 4: What is 'truck warp' (or truck lozenging) and why is it a concern?
- Vertical displacement of the truck bolster
- Diagonal distortion of the truck frame causing unequal wheel loading (Correct answer)
- Lateral offset of the axles
- Torsional wind-up in the drive shaft
Correct answer: Diagonal distortion of the truck frame causing unequal wheel loading
Truck warp is a diagonal racking of the truck frame that causes two diagonally opposite wheels to be lighter on the rail, risking derailment.
Question 5: Which measurement is used to assess wheel tread conicity on a locomotive wheelset?
- Rail gauge measurement
- Wheel diameter difference between left and right wheels
- Tread angle and wear profile geometry (Correct answer)
- Flange height only
Correct answer: Tread angle and wear profile geometry
Tread conicity is defined by the profile angle and wear shape of the tread, which determines how well the wheelset self-centers and resists hunting.
Question 6: When a locomotive negotiates a curve, the outer truck axle must travel a longer path than the inner axle. How does the suspension accommodate this?
- The truck rotates about the center plate while fixed wheelsets follow their respective rail positions (Correct answer)
- The outer axle automatically extends outward
- The springs compress on the outer side only
- The traction motors disengage on curves
Correct answer: The truck rotates about the center plate while fixed wheelsets follow their respective rail positions
The truck swivels about the center plate pivot, allowing both axles to remain approximately perpendicular to the track while the body follows a different arc.
Question 7: What is the significance of the 'bolster' in a locomotive secondary suspension system?
- It connects the fuel injectors to the frame
- It is the structural member that sits on secondary springs and supports the car body weight (Correct answer)
- It provides electrical bonding for the truck
- It houses the journal bearings
Correct answer: It is the structural member that sits on secondary springs and supports the car body weight
The bolster is the cross-member that rests on the secondary suspension springs and transfers the carbody load to the truck, while also providing the center bowl socket.
LEC Suspension & Steering 3
What is the role of the center plate (center bowl) in a locomotive truck assembly?