Track-Train Dynamics: Understanding Lateral Forces and Derailment Risks

1. Chapter 28 Track-Train Dynamics

2. Problem • Lateral Forces • High Center of Gravity Cars • Vertical Forces • Loaded and Empty Cars

3. Lateral Phenomena • Types of Lateral Movement • Lateral Bending and Bending Stress • Lateral Movement • Tilt or Twist

4. 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

5. Train Action (Cont’d) Reverse Curves “Chording” the Curve Truck Hunting

6. Derailment Causes • Operating Error (Transportation) • Mechanical Error (Mechanical) • Track Error (Engineering) • Or a Combination of Above ~ Conduct Root Cause Analysis ~

7. L/V Ratio • Ratio of the lateral component to the vertical component of the wheel load. • As ratio increases, tendency to derail increases

9. Lateral Slip

10. Track Design Factors • Load Application • Ballast Section Design • L/V Track Restraint Ratio

11. Train Forces

12. Problems from Modern Cars • Car Weight

13. Rock and Roll

14. Rock & 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 12-20 mph • Use snubbing devices on cars • Use CWR

15. Truck Hunting

18. Long Cars

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