How a Diesel-Electric Locomotive Works

I'm Jake O'Neal, creator of Animagraffs, and this is how a Diesel-Electric  Heavy Haul Freight Locomotive Works. Diesel-electric locomotives have remained popular  for over 60 years. As a measurement of capacity, they can take a 2,000 pound (907 kg) chunk  of freight nearly 500 miles (804 km) on 1 gallon (3.

8 L) of fuel, which is 3 to 4 times  more efficient than a semi-trailer truck. Let's start with the body and frame. Most modern freight locomotives are  hood units, with a slim middle section and walkways on the outside of the body, allowing visibility in both directions.

The nose portion is full width or "wide cab". They mostly run short hood forward, as  designated by a decal letter "F" for "front". Metal body panels can be opened or removed  for maintenance or emergency access.

Main sections are the nose and operator's cab, auxiliary or "aux" cab which is  packed with electronic components, the engine, and radiator cab at the rear with various cooling  components and the onboard air compressor. The body and critical components are  supported by a thick steel or steel alloy platform called the underframe. A pilot or cowcatcher sits at the front to deflect obstacles that could  derail or damage the locomotive.

There's an overhang called the anti-climber that prevents deflected objects  from flying into the cabin. Concealed collision posts on each side further  protect the cab in the event of an accident. There's a unique ID number  displayed on the front and sides.

A set of air horns sits on top of the body, and there's an electronic speaker attached  to the underframe to emit a bell sound. A large manual handbrake wheel  is visible near the rear. Coupling Locomotives can couple with other locomotives, or train cars.

There are various coupler types. Our  locomotive has a more complex "Type F" coupler, versus the simpler Type E style on our train car. Type F, for example, has robust side features to prevent vertical movement in accident conditions, where Type E requires no such protections.

Couplers are designed to work  by bumping into one another. They'll couple in various arrangements,  for example with both couplers open, or one closed and one open. Knuckles are shaped to guide each other and  also ride along the opposite coupler surface.

that presses against the knuckle thrower which in turn moves the lock. The lock rides along an internal channel, and also rests on a sloped  feature at the back of the knuckle so that it naturally slides into locking position  as all parts reach the end of their travel. For uncoupling, there's a manually operated  bar called the pin lifter or cut lever.

When rotated, parts operate in a reverse  sequence to coupling. The lock rides upwards, pressing the knuckle thrower which  rotates the knuckle into open position. The coupler is attached to the draft  gear assembly, which provides a kind of suspension between train cars.

During impact coupling, also known as a "buff event", the coupler  is forced backwards against the draft gear, which compresses an internal  stack of rubbery discs. The draft gear's rearward travel is  stopped by thick metal tabs at the back. When train cars pull away from each  other, also called a "draft event", the surrounding yoke pulls the draft  gear against a block at the front, causing the internal discs to again compress  and absorb potentially harmful forces.

When cars are coupled together, a hose is also  connected to supply air for individual car brakes, and a cable for cars equipped with electronic brake support devices. More  about these systems later. When multiple locomotives are coupled, the MU  or "multiple unit" connector brings mechanical, engine, and electrical systems under  control of the lead locomotive.

The connector sits in a dummy  receptacle when not in use. Three additional hoses synchronize  braking operations between locomotives. There's the main reservoir hose, the  actuating hose, and the brake cylinder hose.

Engine A 12-cylinder, twin-turbo, 4-stroke diesel engine, called the “prime  mover,” is the power source for this locomotive. Fuel is supplied from reinforced-wall tanks  mounted beneath the underframe. These tanks can carry 5,300 gallons (20065 L) of fuel.

The fuel injection system has a pump  for each cylinder bank, with multi-walled tubing between cylinders  designed to handle high pressures. To decrease noise levels and increase efficiency,  as many as 8 different injections of fuel are made during a single combustion cycle, as  determined by sensors in the fuel system. Engine support components are mounted nearby, including a lube oil tank and oil  filters, fuel filters, and more.

Turbocharging This engine has two turbochargers to efficiently supply  the engine with more air for combustion. There's a charge air cooler nearby to cool  turbo air before it reaches the engine, since cold air is more dense and better suited  to the goal of pumping more air into the engine. The charge air cooler has two  sides, one for each turbo.

These turbos are arranged in what's called  a compound-sequential configuration, which functions as follows. At lower RPMs, exhaust gases can more easily spin up the smaller turbo,  whose compressor wheel begins to take in air. Air enters through a side port and flows through the large turbo before entering the small turbo.

It's then cooled on its way to the engine intake. The large turbo is not yet fully powered. As RPMs  and resulting available exhaust energy increase, a valve opens, spinning up the large turbo.

While the small turbo is easier to rotate  at lower RPMs, it's also designed to handle higher overall pressures. As such, the large, low pressure turbo now directly feeds all of  its air to the smaller, high pressure turbo, and the whole system delivers maximum  airflow to the engine for peak performance. To dramatically reduce certain  pollutants in exhaust gases, these diesel engines are equipped with an  EGR, or exhaust gas recirculation system.

A valve allows exhaust from the left  cylinder bank to enter the EGR system, where it passes through a water cooling unit  before being mixed with fresh incoming air. Sending some exhaust gas back  through the combustion process lowers combustion efficiency in favor of  greatly reducing exhaust pollutants overall. Water To save costs and avoid potentially hazardous anti-freeze  leaks, water is used for various cooling duties.

A large tank holds nearly 400  gallons (1500 L) of water. An engine-driven water pump  supplies pressure to the system. There are large banks of radiators with  external shutters to help manage airflow.

A large fan pulls outside air past these  radiators as water courses through internal tubes. This cooling water flows to the engine, EGR  cooler, turbochargers, air compressor, and more. During colder weather, it also  runs through the fuel system pre-heater to warm the fuel before combustion.

If the locomotive is not running  and temperatures drop below 40° F (4. 5° C) automatic water dump valves open,  draining the system to prevent freezing. Electrical The diesel engine turns a massive alternator, which acts as a generator,  supplying electrical power to critical systems.

The alternator has its own dedicated  blower for cooling, with a side air intake. The locomotive isn't directly, mechanically driven  by the engine. Instead, large electrical motors, called traction motors, are  connected at each wheel axle, and provide the main driving  force to move the train.

These traction motors require fine-tuned speed  control. Without getting into too much detail, it's simply easier to regulate variable motor  speed with DC current as opposed to AC. As such, a fairly intricate conversion process takes  place from the alternator to the traction motors.

AC power from the alternator is converted to  DC power as it flows through rectifier banks in the auxiliary cab section of the locomotive. A DC link in this same system smooths out any uneven power from the alternator, and adjusts  power to the desired speed or frequency. Current then flows through inverters which convert  it back to AC as it's delivered to the motors.

New technology makes varying AC  current more doable, and this process may change in the near future. These traction motors generate a lot of heat during operation. There's  a dedicated air blower system with ducting and flexible connections to  deliver cooling air to each individual motor.

A bank of batteries sits under the aux cab. Apart  from expectable battery duties like starting the diesel engine, these batteries can also deliver  power for moving the locomotive small distances, for example, around a railyard without  having to start the diesel engine. Trucks The underframe rides on trucks or "bogies", which hold traction  motors, axles, wheels, and associated components.

A major consideration in truck design is adhesion, or ensuring wheels maintain maximum  contact with rails for traction. Primary suspension aids adhesion with  springs on both sides of every axle. A pair of dampers on one  side are sufficient to handle vertical shock absorbing duties for the bogie.

Secondary suspension includes a set of  dampers for rotation about the vertical axis. Flexible side bearers are pinned  to the underframe but allow bogies to shift underneath the heavy locomotive. Inside, there's a stack of rubber pieces  that make up a kind of tough spring.

Axles can also move back and forth slightly. This, with secondary suspension, ensures  bogies and wheels maintain maximum rail contact even if the front and back of  the long locomotive aren't in alignment, or on curved sections of track, where front  and back trucks, and axles within the trucks, might need specific, individual orientation  to keep proper contact with rails. A traction pin or rod solidifies the  connection between trucks and the underframe.

Safety hooks limit bogie movement at extremes. The traction motors are attached with bracketry  that allows the motor to move with the axle. A gear set transfers motor  power to the axle and wheels.

The trucks also feature a sand system for  increased traction during startup or braking, or when traveling at less than 15 mph (24 kmh). There are sand boxes at both sides, front  and back, with filler tubes for easy access. Sand nozzles at the front and back of each bogie  provide sand for either forward or reverse travel.

Nozzles blow sand at the  wheels and rail when in use. Braking The ability to efficiently haul incredible tonnage  comes with a serious technical challenge: stopping the train. There are two main  systems for braking: dynamic and pneumatic.

Let's start with the pneumatic or air driven  system, which actuates brake shoes at the wheels. The onboard air compressor supplies  compressed air which is stored in side tanks. The brake system draws from these reservoirs.

Air driven cylinders at the front  and back of the trucks actuate rods and linkages that drive brake shoes. One cylinder manages a single shoe, while another cylinder drives  two linked shoes at once. Still, there's only one brake shoe per wheel.

At the rear of the locomotive, there's a  brake pipe that delivers compressed air to every other railcar in the train. Each car has its own air reservoir to make sure there's always supply for  the individual car's braking needs. Modern locomotives have electronically  controlled pneumatic or ECP systems, where electronics add precision  control to braking procedures.

The brains of the system are  mounted underneath the cab. Each car has an identifying  unit and controller setup. There's an end of train device  connected to identify the very last car.

With all cars connected and properly sequenced by  the ECP system, more complex braking procedures can be performed. For example, brakes can be  applied progressively from the last car in the train forward so cars don't ram into each other. Now, let's look at the dynamic braking system.

Dynamic braking happens inside the  powerful electric traction motors. To put electric motors in basic terms, the  core or rotor has a stationary magnetic field. It's surrounded by a dense set of  electrical windings called the stator.

Electricity traveling through a conductive  material creates a surrounding magnetic field (electromagnetism). The flow of electricity through the windings causes its magnetic field  to rotate, pushing the rotor in turn. Since the stator's magnetic field  is electronically generated, it can be controlled, and even reversed,  adding resistance against the rotor's spin.

This added resistance essentially converts  traction motors into electricity generators. The excess energy is passed to grids of resistors that bleed off braking energy  in the form of intense heat. The dynamic brake box isolates resistors into  their own ducted channel with cooling fans.

Resistors can get so hot  they emit a bright red glow. Dynamic braking adds stopping power to the train's braking process with few additional moving  parts, reducing wear and tear all around. This dynamic braking process shares  concepts with regenerative braking, where electric vehicles can use their momentum  to recover energy, for battery recharging, and so on.

Future freight locomotives may indeed  implement such capabilities to the dynamic braking system instead of releasing this energy as heat. Locomotives generally use a blended approach with both pneumatic and dynamic systems playing a  carefully orchestrated role in stopping the train. Now, let's head to the front of the locomotive  for a tour of the nose and operator's cab.

A door at the nose cab allows entry. Off to one side, there's an electronics cabinet with a head of train device which compliments the end of train device. There's an event recorder, a distributed power system radio module that gives remote control  over locomotives that are a part of the train, but not directly connected to the lead locomotive.

There's a yard download radio which allows wireless event recorder data  downloading, and a GPS module. At the other side of the entry  hallway there's a bathroom. And next to that, a small refrigerator.

Climbing the stairs into the operator's  cabin, there are switches for internal lights. From the back of the cabin we  can see the operator's console, and a crew member's console at the other side. Let's have a closer look at operator controls.

There are two smart displays that can show detailed monitoring of critical systems, with  rows of buttons at the bottom for interaction. Below that, the alerter button is part of  a safety system to ensure driver alertness. The alerter system sounds every few minutes  or so, depending on locomotive speed.

If the alerter button is not pressed within a number  of seconds, brakes are automatically applied. The horn sequencer button sounds the bell and  horn together at predetermined intervals if traveling at more than 0. 5 mph (0.

8 km/h). Individual bell and horn buttons are nearby. A switch panel houses various controls,  for example the dynamic brake switch to toggle the system on or off.

This  switch is on for the lead locomotive, but off for other locomotives  being controlled by the lead. Many other settings follow this pattern in  different lead or trailing configurations. The gauge light controls lighting  for various operator controls.

The call switch sounds an alarm bell in  the operator cabs of trailing locomotives. The reverser handle controls which direction  the locomotive will move when power is applied. This handle is removed when  the locomotive is parked, or in "helper" duty following a lead locomotive.

The reverser handle has built in  constraints to prevent damage. The throttle lever above can't  be moved from the "idle" position until the reverser lever is  moved from its center position. Conversely, if the throttle is  set at more than idle speed, the reverse handle can not be moved  from its forward or reverse position.

The handle is also locked if  dynamic braking is not off. The throttle handle manages engine speed and power  output to the wheels. It's essentially the train's gas pedal, where a steady, consistent power  output setting is ideal for most train operations.

The dynamic braking handle  controls dynamic braking force. There are redundant buttons for  the horn, alerter, and bell. There are also controls for the sand system.

There's a two-way radio receiver nearby. The lever beneath controls the pneumatic  brake system. There are various settings to manage brake system air pressure, in the  locomotive itself and in connected cars.

The independent brake lever below controls  air brakes for just this locomotive. There are rotating switches at the  bottom of the panel for the cab heater, and also front and rear headlight controls. Moving to the back wall, there's  an additional fold out seat.

Above that, a grouping of circuit  breaker modules and switches. In the middle, there's a  protected engine control panel. Let's look at the engine control switch.

For locomotives so equipped, the JOG setting  allows movement under battery power alone, without starting the engine. It's used for short  distances, like moving in or out of a repair shop. With START selected, the ENGINE START button is  pressed to initiate the engine start sequence.

ISOLATE leaves the engine running  at idle but disconnects the main generator, and power to the wheels, etc. The RUN setting is for normal operation. The MULTIPLE UNIT switch has  settings for linking multiple locomotives together in various configurations.

There are engine start and stop switches, and the last panel controls crosswalk or "ditch" lights at the front of the unit, number  sign lights, and lighting for other control areas. The AUTO STOP OVERRIDE button prevents the engine  from shutting down automatically for two hours. Now let's move to the crew member's  area.

There's an additional ergonomic seat for observing, training, and other purposes. There's a smart display at the left  side of the crew member's console. In the center, the emergency brake valve  initiates an emergency braking sequence.

At the front of the console there's a horn  pushbutton, and a heater control switch. Looking towards the front windshield, we see inward and outward facing  cameras for event recording.