Chapter 28 Track-Train Dynamics

Problem  Lateral Forces High Center of Gravity Cars  Vertical Forces Loaded and Empty Cars

Types of Lateral Movement  Lateral Bending and Bending Stress  Lateral Movement  Tilt 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 track  Joints every 19.5 feet – induced oscillation  Car 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 mph  Use snubbing devices on cars  Use CWR Rock & Roll

Truck Hunting

Long Cars

Transportation Technology Center Pueblo, Colorado Test Tracks and Other Research Facilities