A diesel engine can be either two-stroke or four-stroke and, except for its ignition, is much like
any other internal combustion engine. It is one of three types--V, vertical in-line, or horizontal--
depending on the arrangement of its cylinders.
The fuel system includes the fuel tank, fuel and ignition pumps, filters, injection nozzle, and
emergency fuel cutoff valve. The fuel tank has baffle plates to prevent surging and a pit to catch
sediment so that it can be drained out. In some locomotives, the fuel tank is above the pump and fuel
enters the pump by gravity. In others, fuel is pumped from the tank into the main pump by an auxiliary
pump. The fuel pump creates the injection pressure and determines the amount of fuel injected into the
cylinders by the injectors.
In an engine with a water cooling system, water is run through water jackets between the
cylinders and cylinder liners. The water is directed through a radiator to cool it. Louvers on the front of
the radiator can be opened and closed to regulate the heat escaping from it. Occasionally, an engine is
designed so that the pistons are cooled also by their lubricating oil. When this is done, a special oil
radiator, with its own cooling fan, is provided in addition to the water cooling radiator.
Lubricating oil should have some detergent properties so that contaminating materials can be
kept in suspension and filtered out by strainers, made of gauze, steel wool, or closely spaced plates.
Brakes for a locomotive can be the kind that control the locomotive, the train, or both. Air
pressure for the brakes is supplied by a compressor.
The weight of the locomotive is carried by the trucks, which also absorb lateral thrusts and
oppose the tilting tendency. A truck is made of frames, wheels, axles, journals and journal boxes,
bolsters, springs, bearings, and brake rigging. Most locomotives are equipped with chains to limit the
swing of the trucks in case of derailment. Locomotives larger than 40 tons use four-wheel rigid trucks,
four-wheel swing bolster trucks, or six-wheel swing bolster trucks.
Accessories supported by the locomotive engine include a bell, horn, speed recorder, windshield
wipers, sanding system, temperature controls, and engine and cab heaters.