CHAPTER 4

The Locomotive

Steam until mid 1950’s

Types of Locomotives

• Steam• Diesel-Electric• Electric• Hybrid

Two Factors Determine the Ability of a Locomotive toStart, Accelerate, and Obtain Top Speed

Tractive Effort

• The Ability to Overcome Resistance-Starting, Grade, Wind, Curve, Rolling

• Tractive Force = Weight of Drivers x Coefficient of Adhesion

Horse Power (mainly 1,500 to 5,000 hp)

• Rate of Doing Work

• Drawbar Horsepower: horsepower available to haul

Adhesion Control

• Grip Rail without Slipping

• Dependent on weather, rail conditions

• Controlled automatically in modern locomotive

• Sanding

Tractive Force vs. Tonnage and Grade

Performance Curve of the Locomotive (with train resistance for 420 tons trailing load of passenger stock)

Different Horsepower Ratings

• Not all engine power pulls train

• On average, 82% of power is left to pull train

Power Required vs. Speed and Grade

Diesel–Electric Locomotive

• Diesel Engine – Prime Mover

• Turbocharger / Electronic Fuel Injection

• Alternator / Generator / Fans / Batteries

• AC/DC Traction Motors

Locomotive Principal Components

Radial Trucks

Locomotive Controls

• Minimum Levers, but Connected to Circuitry

• “Microprocessor” Control

• Display Screens

• Interfaces with Primary Operator

Six Axle, approx. 390,000 pounds

vs.

Four Axle, approx. 260,000 pounds

Multiple Unit Arrangements Distributive Power / ECP

Mid-Train or Rear End

Slugs and Mates

No Prime MoverStore Excess PowerProvide Weight for Tractive Effort

Maintenance and Life Span

• Most New Locomotives can Self-Diagnose Problems

• Different Inspections Mandatory at Daily, 92-days, Annual, and Biennial Periods

• Remote Diagnostics

• Average Locomotive Service is 20-25 Years

• Used to be Returned to Manufacturer, but Now Sold to Smaller Railroads

Genset and Hybrid Locomotives (Mainly for Switching)

Genset – Multiple engine-generators per vehicle

Hybrid – Operates on batteries that are charged overnight