I was looking through the ‘Deuces” thread and I became a bit confused as to the layout of a locomotive. Actually, it is the flow of air through the engine. Obviously, the cab is up front with the controls. In the back of the cab, I would expect many of the circuit breakers and electronic components. Then the generator set, the engine itself and the radiators in the rear. I imagine things like compressors are put any place there is an available square inch. I have never been inside of a locomotive, so much of this is new to me. Here is where I am confusing myself. On top I see 2 sets of fans, 1 set of 2 and the other a set of 3.The back set of 3 I assume are the radiator fans. Air is being drawn in through the side, through the radiator and out the top. Air flow to the engine itself is what I do not understand. I see that some locomotives have vertical openings mid engine and some are angled. I assume this is either for a clearance issue or a larger air box. Next to the turbo, the engine and compression gases would discharge the exhaust out the top. I am assuming that the air intake is on the side to prevent soot from being drawn in the radiator and coating the radiator. I know this will reduce heat transfer capabilities. Also this will limit hot exhaust gases from being drawn back into the compression cycle as heat robs horsepower. If this is basically correct, then what is the purpose of the first group of 2 fans and what do they actually do?
The first 2 fans on the blister, are the dynamic brake fans. When trains are traveling down grade, the traction motors produce electricity, which is disipatted through the dynamic brake grid as heat, and vented with the fans. this action is used to retard the speed of the train without wearing out the brake shoes.
On your standard SD40-2 for instance, the air intake for the power plant itself is right behind the cab. Then it is taken in thru the cylinders and such, and then out the exhaust on top and forward of the dynamic brake housing. The generator is in front of the power plant, in between it and the cab, under the air intake, and the air compressor for the air brakes is towards the back of the engine, hooked to the back of the power plant. Now, the newer locomotives, have a different layout, depending on manufacturer.
Thank you for explaining this to me. I have heard of dynamic brakes but need to do some reading. Sounds to me like the traction motors are working as generators during this type of braking and the load on the traction motors causes the actual slowing of the train. So in theory, the higher the load placed on the traction motors, the higher the rate of slowing of the locomotive. Does this sound accurate? Working in a technical line of work, how would I get a copy of an operating manual or tech manual on a locomotive to get a better understanding? It works for me with everything I work on.
Yes, but only up to a point. The traction motors can only generate so much resistance before the wheels begin to slip. So engineers who handle heavy trains coming down long, steep grades have to judiciously use both dynamics and airbrakes to prevent a runaway train. Brake failures on long stretches of steep downhill (such as the descent from the Cajon Pass) have in the past resulted in some horrific runaway train accidents.
