Mechanical and Electrical Systems 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 Mechanical and Electrical Systems flashcards as text
On a locomotive equipped with HTCR (High Tractive Effort, Controlled Response) or similar wheel creep control, what is the system designed to do?
Answer: Allow a controlled small amount of creep to maximize adhesion before reducing power
Creep control systems allow a slight, controlled amount of wheel-rail slippage to operate near the peak of the adhesion curve, maximizing tractive effort.
What is the function of the 'equalizing reservoir' in the 26-L or similar brake systems?
Answer: Serve as a reference volume that the engineer adjusts to control brake pipe pressure
The equalizing reservoir is adjusted by the automatic brake handle and serves as the reference pressure that the self-lapping relay valve uses to set brake pipe pressure.
If a locomotive's battery voltage drops critically low, which systems are at greatest risk of failing first?
Answer: Engine starting, control circuits, and event recorder
Engine starting, control circuits, cab displays, and safety recorders all depend on battery voltage and are first to fail when battery voltage drops critically.
What does an illuminated 'hot engine' or high-coolant-temperature light require the engineer to do?
Answer: Reduce throttle and monitor temperature; shut down if it continues rising
A hot engine indication requires reducing throttle to lower engine load and heat generation while monitoring temperature; continued rise warrants shutdown.
What is the primary purpose of 'sanding' the rails during locomotive operation?
Answer: Increase friction between the wheel and rail to improve adhesion
Sand applied between the wheel and rail surface increases the coefficient of friction, improving adhesion for both traction and braking.
In a two-unit consist, the trailing locomotive's traction motors are not responding to throttle commands from the lead unit. What is the most likely cause?
Answer: The multiple-unit (MU) control cable is disconnected or faulty
MU cables carry throttle, brake, and control signals between locomotives; a disconnected or faulty cable prevents the trailing unit from receiving commands.
Which gauge or indicator directly tells the engineer whether the automatic brake is releasing or applying in terms of brake pipe pressure?
Answer: Brake pipe pressure gauge
The brake pipe pressure gauge shows whether brake pipe pressure is increasing (release) or decreasing (application), directly indicating brake system status.