How a Diesel Locomotive Engine – Train Motors Works

diesel engine locomotive with electric traction

From powering passenger and freight trains to hauling heavy loads, diesel l locomotives are essential to the transportation industry – and understanding how they work is key to appreciating their importance! They are used to pull trains and can be found worldwide. Diesel locomotives have been in use for more than a century and are popular due to their efficiency and power. This blog post will discuss the different parts of a diesel locomotive engine and how they work together to create motion!

The heart of a diesel locomotive is its engine. This powerful device consists of several components, including cylinders, crankshaft, valves, fuel, cooling, and exhaust systems. To understand how a diesel locomotive works, it’s important to understand the roles these parts play.

Before we dive into the locomotive parts we just want to briefly touch on some high-level stats and common specs on these incredible power horses.

Electro-diesel electric locomotives and how many are produced to date

The most common electro-diesel electric locomotives are EMD (Electro-Motive Diesel) models, which account for more than 80% of the world market in diesel locomotives. These models feature modern engine designs with high levels of efficiency, reliable performance and low maintenance requirements. As of 2021, EMD has produced more than 35,000 diesel-electric locomotives and continues to lead the industry in production.

In addition to EMD models, numerous other companies produce electro-diesel electric locomotives including GE Transportation (formerly known as Alco), Wabtec, and Bombardier. These manufacturers offer various models of their own design, ranging from medium- to heavy-duty locomotives. The engines produced by these companies have become a popular choice for freight and passenger train operators due to their reliable performance, fuel efficiency, and low maintenance requirements.

Electro-diesel electric locomotive engine common specs

Electro-diesel electric locomotives are typically powered by 16-cylinder diesel engines with a displacement of 45 liters (2,750 cubic inches). A typical larger engine is capable of producing 3,000 hp (2.2 MW) at 900 RPM and can reach a top speed of 110 mph (177 km/h). It has a maximum tractive torque of 1,280 kilonewtons (kN) at 5 km/h and can pull 2,000 tonnes of freight.

The generator typically used is a three-phase alternating current machine that uses a squirrel cage rotor with permanent magnets. The electric motors are usually three-phase AC induction machines and have a maximum speed of 1,500 RPM. The engines are highly reliable and require little maintenance due to their self-lubricating design and durable parts. Additionally, they have low emissions compared to diesel engines of a similar size.

Largest and smallest diesel engines

motor with electric resistors for railways

The largest diesel-electric locomotives are used to haul freight across long distances. These hefty engines typically weigh up to 400 tons and can generate between 4,000 and 6,000 horsepower depending on the model. They feature multiple cylinders that are powered by an array of electrical components including traction motors, generators, and control systems.

The smallest diesel-electric locomotives, on the other hand, are primarily used to move short distances like in mining or agricultural operations. These engines typically weigh much less than their larger counterparts, ranging from 25 to 35 tons. They also generate far less power, with a maximum output of around 1,000 horsepower.

Now let’s move on to the parts and what different components of the locomotives are and how they work.

Traction motor

The traction motor is a crucial part of the diesel locomotive engine and is responsible for creating motion. It converts electrical energy into mechanical force, allowing the train to move forward. The traction motor consists of two primary components: an electromagnet and a set of brushes. Electromagnets create an electromagnetic field that provides the necessary force for movement, while brushes ensure power flows from the power source to the motor.

Traction motor types

The traction motor type depends on the locomotive engine’s size and power requirements. A direct current (DC) traction motor is typically used for small to medium-sized engines. This motor employs a DC voltage to power the magnets and create an electromagnetic field for movement.

DC traction motors

In DC traction motors, a direct current is applied to armature windings to create a rotating magnetic field. This magnetic field drives the rotor and produces torque for motion. Speed control can be achieved by changing the armature circuit’s resistance or by varying the voltage applied to it.

AC Traction Motors

Alternating current (AC) motors are often used for larger and more powerful locomotives as they can provide more torque when needed.

In AC traction motors, the power source (usually an alternating current generator) supplies a three-phase electrical current to the motor. This current is converted into a rotating magnetic field that powers the motor and provides torque. The speed of the motor can be controlled by varying the frequency of the AC voltage.

In AC traction motors, the power source (usually an alternating current generator) supplies a three-phase electrical current to the motor. This current is then converted into a rotating magnetic field that powers the motor and provides torque. The speed of the motor can be controlled by varying the frequency of the AC voltage.

In either case, the brushes ensure electrical energy is properly transferred from the power source to the motor.

Diesel-electric locomotives engine

high torque 6 axle rail wheel

The electro-diesel electric locomotive engine is a diesel-electric locomotive powered by both electricity and diesel fuel. This type of power plant combines the high efficiency of an electric motor with the reliability and maintenance advantages of a diesel engine.

The engine utilizes an electric generator driven by a diesel fuel combustion engine to generate electricity. This generated electricity is transmitted to the motors through a flexibly connected system of wires that allow for speed, direction, and braking control. The electric generator also recharges batteries on board the ms.

The valves control the flow of air, fuel, and exhaust into and out of the cylinders. They open at specific points in the combustion cycle to allow air and fuel to enter, then close again as soon as combustion is complete. Valves are essential for controlling how much power the engine produces and ensuring that it runs efficiently.

Electric generator Types

The engine’s efficiency increases when it is run at its optimal speed, usually around 900-950 RPM for most diesel engines used in locomotives.

Two main types of electric generators are used in locomotives: synchronous generators and asynchronous generators. Synchronous generators have an armature that rotates at a constant speed, while asynchronous generators are powered by an induction motor where the speed can vary. Synchronous generators tend to be quieter and more reliable than asynchronous ones, but they require more maintenance and are overall more expensive.

Advantages and Disadvantages

The main advantage of this type of locomotive is its fuel efficiency. The electric generator and motors are more efficient than traditional diesel engines, resulting in less fuel consumption and reduced emissions. This type of engine also requires less maintenance as the electric generator does not need to be regularly serviced as a diesel engine would.

The electro-diesel electric locomotive engine is commonly found in both passenger and freight trains. It is an efficient and reliable power source that is beneficial for the environment and provides cost savings in fuel consumption.


The crankshaft connects each cylinder by connecting rods that transfer energy from one part of the engine to another. It is responsible for turning the wheels of the locomotive and creating motion. The crankshaft also houses a flywheel, which helps maintain a steady speed and keeps the engine running smoothly even when load changes or terrain changes.

A typical EMD diesel locomotive engine has a crankshaft with eight main bearings. The bearings are typically filled with high-pressure oil, which helps to reduce wear and improve performance. Additionally, the crankshaft is designed to handle a maximum firing pressure of 350 psi (2.4 MPa) at 900 RPM.

The crankshaft also features counterweights which help to dampen vibration and keep the engine running smoothly. This helps reduce wear and tear on the engine’s components, improving its overall efficiency. Additionally, it reduces noise levels and improves fuel economy.

Diesel locomotive engine cooling systems

The cooling system helps keep the engine at an optimal temperature while running. It consists of a radiator, fan, and hoses that carry coolant throughout the engine. This coolant absorbs heat from the cylinders and dissipates it into the air or back into the atmosphere.

The cooling system consists of several parts, including radiators, fans, and oil coolers. Radiators are responsible for dissipating heat from the engine block into the atmosphere via airflow. Fans help to circulate air through the radiator, while oil coolers help to reduce engine oil temperatures by transferring heat from it to the atmosphere. By maintaining a safe operating temperature, these components ensure that excessive wear and tear on engine internals is avoided. In addition, some locomotives employ additional cooling systems such as water-cooled jackets or intercoolers, to regulate engine temperature in extreme weather conditions.

locomotive oil coolers

The oil cooler consists of a set of metal plates filled with fins, which increase surface area and help dissipate heat more efficiently. The system works by circulating hot engine oil through these plates where it is cooled by airflow passing through them. Once cooled, the oil passes back into the engine block, where it helps lubricate moving parts and provide essential cooling circulation. In addition, by keeping engine oil at a safe temperature, oil coolers ensure that excessive wear and tear on the internals is avoided.

Different locomotive Oil cooler types

Oil coolers come in several different types, such as bar and plate, tube and fin, and stacked-plate designs. As mentioned above the bar and plate oil cooler consists of a set of metal plates arranged in rows with multiple fins between them to increase surface area for efficient heat dissipation. Tube and fin oil coolers employ a set of tubes surrounded by several small curved fins that provide increased surface area for cooling air to pass through. Finally, stacked-plate oil coolers consist of two or more layers of metal plates with fins between them to help disperse the heat from engine oil more efficiently than other designs.

While each type has its own set of advantages and disadvantages, the most important factor when choosing an oil cooler is ensuring that it is suitable for the particular engine and its operating conditions. Factors such as engine size, heat production levels, and ambient temperature must be considered when selecting a cooler type.

Diesel locomotive brakes System

train coils and suspended brake system on reailway cars

Brakes are essential to any diesel locomotive, ensuring that the vehicle can safely stop in both regular operations and emergencies. Diesel locomotives use air brakes activated by compressed air stored in tanks on the vehicle. Upon braking, the compressed air is released from one tank while simultaneously being sucked into another tank which helps reduce the system pressure. This reduces the piston force within the brake cylinders, slowing down or stopping the train when needed. The compressor located on board the locomotive is responsible for replenishing the air tanks with compressed air when needed.

In addition to regular braking systems, some diesel locomotives are also equipped with dynamic brakes, which use motors to produce a braking effect. This uses the same principle as regenerative braking in electric

Dynamic Braking System

Dynamic brakes are an additional braking system found on many diesel locomotives. These brakes work by converting the kinetic energy of the moving train into electricity which is then dissipated as heat. This braking system utilizes electric motors to turn the wheels in the opposite direction, thus creating a retarding force that slows down the train. The electricity produced by this process is fed back into the locomotive’s traction motor and used to help power it up hills or over long distances. Dynamic brakes are especially useful on long downhill grades where they can provide significant braking force without putting any strain on the regular air brake system. They also add extra safety by allowing an emergency stop should something happen unexpectedly along the route. Although dynamic brakes do not reduce wear and tear on other components, they can improve the overall energy efficiency of a diesel locomotive.

Dynamic brakes require careful control when operating to prevent overuse or sudden usage, which can damage the components and reduce the effectiveness of the braking process. Therefore, careful selection and maintenance of dynamic brakes are essential to ensure they are always running in peak condition when needed. Proper training for locomotive engineers is also necessary to ensure this system’s safe and efficient operation.

Fuel system

Another essential part of a diesel locomotive’s engine is its fuel system. This includes not only the fuel tank but also pumps, injectors, and filters which help provide clean burning fuel for efficient operation. The fuel system starts with diesel fuel being pumped

Typical EMD diesel locomotives have fuel tanks holding up to 1,250 gallons of diesel fuel. This fuel is then injected into the engine’s combustion chamber, which is combusted with air, generating power. The injectors used vary depending on the model of the machine, but all serve the same purpose of providing a fine mist of fuel which is then ignited by the spark plugs to create an explosion and generate power. In addition to efficient combustion, good quality fuel ensures that engine components are not damaged by impurities or poor lubrication caused by low-grade fuels.

Fuel pumps and their types in EMD locomotives

Fuel pumps are an essential part of a diesel locomotive’s fuel system. In EMD (Electro-Motive Diesel) locomotives, there are two types of fuel pumps: positive displacement and centrifugal.

The positive displacement pump forces diesel fuel through a set of valves that open and close to pressurize the fuel before it is injected into the engine. This ensures that the right amount of fuel is delivered at precisely the right time for efficient combustion.

On the other hand, the centrifugal pump uses rotating vanes to draw in diesel fuel and then throw it outward, where it can be pressurized before injection into the engine’s combustion chamber. This type of pump is often used in locomotives with high horsepower ratings since it can deliver more fuel at higher speeds.

Both types of fuel pumps require regular maintenance to ensure that they are functioning correctly and delivering the right amounts of fuel for efficient engine performance. It is also essential to use the correct grade of diesel fuel to ensure that the fuel pumps and other engine components are not damaged or degraded over time.

Each cylinder has its injector that is controlled by a computer. The injector sprays fuel precisely to ensure maximum efficiency and power output.

Diesel locomotive engine lubrication system and its components

engine gear and polly lubrication

The lubrication system typically consists of the following components: a sump, oil pump, filters, cooler, and oil lines. The engine stores its oil in the sump while the pump circulates it through the various components. Oil lines then carry the oil to each cylinder and other moving parts within the engine. Finally, filters remove any impurities or particles collected in the oil, while a cooler helps keep temperatures down to prevent excessive wear and tear.

In EMD (Electro-Motive Diesel) locomotives, the lubrication system is electronically controlled to ensure that all engine parts receive adequate lubrication at the correct times. The oil pressure sensor monitors the amount of oil flowing through each component and sends this information to the Electronic Control Unit (ECU). This then instructs the appropriate pumps and valves to open or close to maintain optimal lubrication levels.

The system also has numerous safety features designed to protect the engine from damage due to poor lubrication. For example, if it detects that the oil pressure is too low, it will shut down the engine until the issue is resolved. This helps ensure that the engine is correctly lubricated and prevents costly repairs from occurring due to a lack of oil.

The lubrication system also needs to be regularly monitored and serviced to ensure that it works correctly and delivers adequate levels of oil. This will help keep the engine operating efficiently while extending its life expectancy.

Diesel locomotive exhaust system

The exhaust system of a diesel locomotive is an important part that helps to reduce emissions and improve fuel efficiency. It consists of a series of pipes connected to the engine’s exhaust manifold, through which hot exhaust gases are expelled from the engine.

Exhaust systems typically employ several devices such as catalytic converters, mufflers, and resonators to help reduce noise levels as well as harmful exhaust emissions. The catalytic converter is designed to convert toxic gases into less harmful ones, while mufflers and resonators reduce the noise produced by the engine.

The diesel locomotive’s exhaust system plays an important role in keeping the engine operating efficiently and reducing its environmental impact. A well-maintained exhaust system helps to keep the engine running at optimal performance levels and ensures that emissions are kept to a minimum. Additionally, regular maintenance of the exhaust system can help reduce fuel consumption and improve fuel economy.

Finally, the exhaust system carries away any leftover gasses generated by combustion. This can include carbon monoxide, nitrogen oxides, and other pollutants filtered out before being released into the environment.

Now that you know the main parts of a diesel locomotive engine work, you can appreciate why these powerful machines are so important to the modern transportation industry. With their ability to generate large amounts of power and their efficiency, it’s no wonder why these engines are still in use today! Thanks for reading!

Need a bit of technical help finding your motor parts?

Simor Industrial solutions have years of experience in sourcing diesel locomotive parts for many customers around the world. If you require consultation or need technical assistance, do not hesitate to contact us.

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