Train Parts Names and Functions

Understanding the various train parts names and their functions is key to appreciating the engineering marvel of railways. From the powerful locomotive to the intricate braking systems, each component plays a vital role in ensuring safe and efficient operation. This guide explores the essential parts of modern diesel-electric locomotives, steam engines, and the rolling stock they pull.

Key Locomotive

The locomotive is the heart of the train, generating the power needed to move thousands of tons. While designs vary, several core components are universal. These train parts names are fundamental to any discussion of railway mechanics.

The Engine and Power Assembly

In modern diesel-electric locomotives, the primary power source is a large diesel engine. This is not the same as a car engine; it’s a massive prime mover designed for continuous, heavy-duty operation.

• Diesel Engine: A reciprocating internal combustion engine that burns diesel fuel. It doesn’t drive the wheels directly. Instead, it turns a large alternator.
• Alternator/Generator: Connected to the engine’s crankshaft, this component converts the mechanical energy from the engine into high-voltage electrical power.
• Rectifier: In locomotives with AC alternators, a rectifier is used to convert the alternating current (AC) into direct current (DC) needed to power the traction motors.
• Power Assembly: This is the core of a diesel engine cylinder. It consists of the cylinder head, cylinder liner, piston, and connecting rod. A large V16 engine, for example, would have 16 power assemblies.

Traction Motors and Bogies

Traction motors are the components that actually make the train move. They are powerful electric motors mounted on the train’s bogies.

• Traction Motors: These motors receive electrical power from the alternator and convert it back into mechanical energy. A gearbox connects the motor to the axle, turning the wheels. A typical six-axle locomotive has six traction motors, one for each axle.
• Bogie (or Truck): This is the undercarriage assembly containing the wheels, axles, and traction motors. A bogie is designed to pivot, allowing the locomotive to navigate curves smoothly. Most modern locomotives use two three-axle bogies.
• Wheels and Axles: The steel wheels are pressed onto a solid steel axle. The profile of the wheel is slightly conical, which helps steer the bogie through turns and keeps it centered on the track.
• Journal Bearings: These are the bearings at the ends of the axles that support the weight of the locomotive and allow the axles to rotate with minimal friction.

The Braking System

Controlling the immense momentum of a train requires a robust and fail-safe braking system. The air brake system, invented by George Westinghouse, is standard across the industry.

• Air Compressor: Driven by the diesel engine, this component compresses atmospheric air and stores it in reservoirs on the locomotive.
• Brake Pipe: A continuous pipe that runs the length of the entire train, connecting every car. It is kept charged with compressed air (typically at 90 psi).
• Driver’s Brake Valve: Located in the cab, this valve allows the engineer to control the brakes. By reducing the pressure in the brake pipe, the engineer signals the brakes on each car to apply.
• Brake Cylinder: On each car, a reduction in brake pipe pressure causes air from an auxiliary reservoir to flow into a brake cylinder. This pushes a piston that uses a system of rods and levers (brake rigging) to press brake shoes against the wheels.
• Dynamic Brakes: A supplementary braking system on diesel-electric and electric locomotives. When engaged, the traction motors act as generators, converting the train’s kinetic energy into electricity. This electricity is dissipated as heat through large resistor grids on the locomotive’s roof, creating a powerful braking effect without wearing down the mechanical brake shoes.

Steam Train Parts Names and Functions

Steam locomotives operate on entirely different principles and have a unique set of parts. Understanding these historic train parts names provides insight into the golden age of railroading.

The Boiler and Firebox

The core of a steam locomotive is its boiler, a massive, pressurized vessel that turns water into high-pressure steam.

• Firebox: A combustion chamber at the rear of the boiler where fuel (coal, wood, or oil) is burned. The intense heat it generates is the starting point for all the locomotive’s power.
• Boiler: A horizontal cylinder filled with water and hundreds of tubes (fire-tubes) running through it. Hot gases from the firebox pass through these tubes, heating the surrounding water to create steam.
• Steam Dome: Located at the highest point of the boiler, this dome collects the “dry” steam, separating it from boiling water before it is sent to the cylinders.
• Superheater: A set of tubes that routes steam back through the hot fire-tubes. This process further heats the steam, increasing its energy and efficiency before it enters the cylinders.

The Motion and Running Gear

This is the assembly of rods and wheels that transforms the steam’s power into motion.

• Cylinders and Pistons: High-pressure steam from the boiler is fed into large cylinders. The steam expands, pushing a piston back and forth within the cylinder.
• Crosshead: A connecting joint that slides along a guide. It links the piston rod (coming out of the cylinder) to the main rod.
• Main Rod: A large, heavy steel rod that connects the crosshead to one of the driving wheels (the “main driver”). It converts the piston’s linear motion into the rotational motion of the wheels.
• Driving Wheels: The large, powered wheels of a steam locomotive. They are connected by coupling rods to ensure they all turn in unison.
• Valve Gear: An intricate system of levers and rods (like the Walschaerts or Baker valve gear) that controls the timing of steam entering and exiting the cylinders. It essentially acts as the locomotive’s transmission, controlling its direction and power output.
• Blastpipe: Directs the exhaust steam from the cylinders up the smokestack. This creates a draft that pulls air through the firebox, making the fire burn hotter as the locomotive works harder.

Essential Freight and Passenger Car Components

While unpowered, the cars that make up a train consist of several important parts.

Couplers and Draft Gear

Couplers are the devices at the end of each car that link them together to form a train.

• Knuckle Coupler: The standard coupler in North America (also known as the Janney coupler). It features a pivoting “knuckle” that locks automatically when two cars are pushed together.
• Draft Gear: A shock-absorbing system located behind the coupler. It is a combination of springs and friction plates that cushions the pushing and pulling (buff and draft) forces that run through a train, preventing damage to the cars and their cargo.
• Buffers and Chain Coupler: The standard system in much of Europe. It consists of two sprung buffers on each end of a car and a heavy-duty chain with a hook to link the cars.

Bogies and Wheels

Like locomotives, all rail cars ride on bogies (trucks).

• Side Frames: The two cast steel sides of a freight car truck that hold the wheelsets.
• Bolster: A central beam that rests on springs between the two side frames. The car body sits on the bolster via a center plate, which allows the truck to pivot.
• Springs: Large coil springs (and sometimes friction wedges) that provide suspension for the car, protecting both the car and its contents from shocks from the track.

Frequently Asked Questions About Train Parts

Q1: What is the main component of a train?
A1: For a locomotive-hauled train, the main component is the locomotive (or engine), which provides the power. It contains the diesel engine, alternator, and traction motors that are essential for movement.

Q2: What are the wheels on a train called?
A2: The complete assembly is a wheelset, consisting of two steel wheels pressed onto a solid axle. On a locomotive, the powered wheels are called “driving wheels.”

Q3: What is the front part of a train called?
A3: The metal frame at the very front of a locomotive is called a pilot, or more commonly, a “cowcatcher.” Its purpose is to deflect any obstacles off the track that could derail the train.

Q4: How do train brakes work?
A4: Most trains use an automatic air brake system. A reduction in air pressure in the continuous brake pipe signals each car’s brakes to apply. This fail-safe design ensures that if the train separates, the brakes apply automatically.

Q5: What connects train cars together?
A5: Train cars are connected by couplers. In North America, automatic knuckle couplers are standard. The assembly also includes a draft gear, which acts as a shock absorber for the forces between cars.