15. Tractive Resistances
1. Train Resistance
I. Speed Independent (Rolling) Resistances
II. Speed Dependent Resistances
III. Atmospheric Resistances
2. Resistance due to Track Profile
I. Grade Resistance
II. Curve resistance
3. Resistance due to Starting & accelerating
4. Wind Resistance
18. Track Modulus
• Load Per Unit Length of the rail Required to
Produce Unit Depression.
• Depends Upon:
1. Gauge
2. Type of Rail section
3. Type of sleeper and density
4. Type of ballast section
5. Subgrade
19. Track stresses
1. Wheel loads
2. Dynamic effect of wheel loads
3. Hammer Blow
4. Lateral Thrust due to Nosing Action
5. Pressure Exerted by the flanges of the wheels
on sides of rails
6. Stresses due to Irregularity of track
7. Additional stresses on curves
20. Hauling Capacity (H.C) &
Tractive Effort (Te)
• Load handled by the locomotive
• H.C is the Product of Coefficient of friction &
Weight on the driving wheels.
Average value of Coefficient of friction= (1/6)
23. Stresses in Rail
• Longitudinal Stresses due to Tractive Effort &
Braking Forces.
• Thermal stresses
• Due irregularity there will be heavy impact on
the rails.
• Minimum Ultimate Tensile Strength of Rail =
72.42 kg/cm2
24. Stresses in the Sleepers
• Stresses in sleepers depends upon:
• Wheel load
• Irregularities in the track
• Speed
• Dynamic effect of wheels on rails
• Elasticity of the rail
25. • Efficiency of Fastenings
• Design & Dimension of Sleeper
• Strength of Sleeper
• Track Modulus
• Stiffness of the rail
• Maintenance of track
26. Stresses in the Ballast
Stresses in Ballast depends on:
• Elastic Property of the sleeper
• Degree of compaction
• Nature of Ballast bed
• Bigger the cess & size of sleeper, lesser the
Pressure in ballast & formation.
27. Stresses in the Formation
• Stresses in subgrade is decreased by
increasing both depth & Size of the Ballast.
• Quality & Gradation of Ballast influences
ultimate pressure on formation.