Chapter 28

Track-Train Dynamics

Problem

Lateral Forces

High Center of Gravity Cars

Vertical Forces

Loaded and Empty Cars

Types of Lateral MovementLateral Bending and Bending StressLateral MovementTilt or Twist

Lateral Phenomena

Train Action

Derailment Wheel Climbing Rail Overturning

Brake Action – assumes status of a long and flexible beam in compression, a relatively unstable state

Quick take-up of slack in a long train can also exert lateral pressure

Train Action (Cont’d)

Reverse Curves

“Chording” the Curve

Truck Hunting

Derailment Causes

Operating Error (Transportation)

Mechanical Error (Mechanical)

Track Error (Engineering)

Or a Combination of Above

~ Conduct Root Cause Analysis ~

L/V Ratio

Ratio of the lateral component to the vertical component of the wheel load.

As ratio increases, tendency to derail increases

Lateral Slip

Load Application

Ballast Section Design

L/V Track Restraint Ratio

Track Design Factors

Train Forces

Car Weight

Problems from Modern Cars

Rock and Roll

More prevalent on jointed trackJoints every 19.5 feet – induced oscillationCar body springs have natural frequency of

oscillation At speeds between 12 and 20 mph

frequencies are additive If square joints – bounce Solutions:

Don’t set sustained speed limits between 12-20 mph

Use snubbing devices on carsUse CWR

Rock & Roll

Truck Hunting

Long Cars

Transportation Technology Center

Pueblo, Colorado

Test Tracks and Other Research Facilities