Drivetrain & Transmission Flashcards
7 cards from real LEC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Drivetrain & Transmission flashcards as text
A locomotive's speedometer shows a speed 5 mph higher than GPS-measured speed. The MOST likely drivetrain cause is:
Answer: Worn or undersized wheel treads reducing the effective rolling radius
As wheel treads wear and diameter decreases, the wheel travels less distance per revolution, but the speedometer calibrated for new wheel size reads high.
What is the function of a 'split-field' arrangement in older DC traction motors during dynamic braking?
Answer: It reverses current through the motor field to convert motor operation to generator operation
In dynamic braking, reversing field current causes the motor to act as a generator, converting kinetic energy to heat in resistor grids to retard train movement.
What does 'wheel diameter compensation' in a locomotive control system account for?
Answer: Worn wheels of different diameters on the same locomotive causing unequal motor loads
When wheels on the same locomotive have worn to different diameters, compensation adjusts individual motor outputs to prevent overloading motors on smaller-diameter wheels.
In a locomotive consist (multiple units), how is traction power typically coordinated between units?
Answer: Multiple-unit (MU) control cables transmit throttle and brake commands from the lead unit to all trailing units
MU cables carry control signals (throttle position, brake commands, direction) from the controlling locomotive to all units in the consist, so one engineer operates all units.
What is the primary purpose of 'field shunting' (field weakening) in DC traction motor operation?
Answer: To reduce motor field strength, allowing higher motor speed above base speed for higher train speeds
Field weakening reduces the back-EMF generated by the motor, allowing it to spin faster at the same voltage, extending the locomotive's speed range beyond the base transition point.
When a locomotive is operating in 'Run 8' (full throttle) at low speed on a heavy grade, the traction motor current will be:
Answer: At or near maximum rated current, limited by the load regulator
At low speed under heavy load on full throttle, the load regulator maintains maximum allowable current through the motors to develop maximum tractive effort.
What is 'creep speed' in the context of locomotive drivetrains and track maintenance equipment?
Answer: A very slow controlled speed used for precise positioning or maintenance operations
Creep speed refers to very slow controlled movement, often just a few miles per hour, used for coupling operations, entering maintenance facilities, or precise track work positioning.