The document discusses the components and stresses acting on railroad tracks. It describes the main parts of a track including rails, sleepers, ballast, and formation. Rails are joined with plates and bolts and fastened to sleepers. Sleepers transfer load to ballast which provides drainage and an even surface. Forces on tracks include vertical, lateral, longitudinal loads from trains. Wheels are coned rather than flat to reduce wear and allow lateral movement. Coning results in different tread diameters on inner and outer rails to prevent slipping.

1. Track or permanent way and
Track Stresses

2. Permanent way
• The track or permanent way is the railroad on
which trains run. It consists of two parallel
rails fastened to sleepers with a specified
distance between them.
• The sleepers are embedded in a layer of
ballast of specified thickness spread over level
ground known as formation.
• The ballast provides a uniform level surface
and drainage, and transfers the load to a
larger area of the formation.

4. The rails are joined in series by fish plates and
bolts and these are fastened to the sleepers
with various types of fittings.
Note: In the early days, a temporary track used to
be laid for carrying soil and other building
material for the construction of a railway line;
this temporary track used to be removed
subsequently.

5. Each component of the track has a specific
function to perform.
1. The rails act as girders to transmit the wheel
load of trains to the sleepers.
2. The sleepers are spaced at a specified distance
and are held in position by the ballast. The
sleepers hold the rails in their proper
positions, provide a correct gauge with the
help of fittings and fastenings, and transfer the
load to the ballast.
3. The formation takes the total load of the track
as well as of the trains moving on it.

6. Requirements of a Good Track
A permanent way or track should provide a
comfortable and safe ride at the maximum
permissible speed with minimum maintenance
cost. To achieve these objectives, a sound
permanent way should have the following
characteristics.
(a) The gauge should be correct and uniform.
(b) The rails should have perfect cross levels. In
curves, the outer rail should have a proper super
elevation to take into account the centrifugal
force.

7. (c) The alignment should be straight and free of kinks.
In the case of curves, a proper transition should be
provided between the straight track and the curve.
(d) The gradient should be uniform and as gentle as
possible. The change of gradient should be followed
by a proper vertical curve to provide a smooth ride.
(e) The track should be resilient and elastic in order to
absorb the shocks and vibrations of running trains.
(f) The track should have a good drainage system so
that the stability of the track is not affected by water
logging.

8. (g) The track should have good lateral strength so
that it can maintain its stability despite
variations in temperature and other such
factors.
(h) There should be provisions for easy
replacement and renewal of the various track
components.
(i) The track should have such a structure that not
only is its initial cost low, but also its
maintenance cost is minimum.

9. sleeper density
• Sleepers are laid to various sleeper densities
varying from (M + 7) to (M + 4) or 1540 per km
to 1310 per km depending upon the weight
and volume of traffic.
• Here M stands for length of rail in metres.
(M + 7) means 20 sleepers per rail length for BG
and 19 sleepers per rail length for MG.
M- Length of BG Rails = 13m
M- Length of MG Rails = 12m

10. Short welded rails (SWRs).
• The rails are welded together to form longer
rails and are laid progressively on the track in
order to reduce maintenance costs and noise
levels and thereby provide more comfortable
travel.
• The rails are welded in depots in three rail
panels, normally by the flash-butt welding
method, to form short welded rails (SWRs).

11. Long welded rails (LWRs)
• Long welded rails (LWRs) are also being
progressively introduced on various routes of
Indian Railways. Thermit welding is normally
done at the site to convert short welded rails
into long welded rails.

12. Forces Acting on the Track
A rail is subjected to heavy stresses due to the following
types of forces.
(a) Vertical loads consisting of dead loads, dynamic
augment of loads including the effect of speed, the
hammer blow effect, the inertia of reciprocating
masses, etc.
(b) Lateral forces due to the movement of live loads,
eccentric vertical loading, shunting of locomotives, etc.
(c) Longitudinal forces due to tractive effort and braking
forces, thermal forces, etc.
(d) Contact stresses due to wheel and rail contact.
(e) Stresses due to surface defects such as flat spots on
wheels, etc.

13. Coning of Wheels
• The wheels of locomotive are not flat but
sloped or coned at a slope of 1 in 20.
• The distance between inside edges of wheel
flanges (B) is generally kept less than the
gauge (G). This results in a gap of 1 cm
between flange and running face of rail.

14. Coning of Wheels

15. Theory of coning

16. If the tread dia. on both the rails is same then amount
of slip is:
Where, outer radius, R₂= R+(G/2)
R₁= R- (G/2)
G=Gauge
θ= angle at centre in radians.
Slip= θ×G
G=1.676 meters for B.G

17. Coning and canting of Wheels

19. Theory of coning
Advantages of coning:
✓ Reduce the wear and tear of wheel flanges and rails.
✓ To provide possibility of lateral movement of the axle with its
wheels.
✓ To prevent the slipping of wheels.
Theory of coning:
✓ On level track, as soon as the axle moves towards one rail, the
dia of the wheel tread over the rail increases, while it
decreases over the other rail. This prevents the further
movement and axle get back to its original position.
✓ Due to rigidity of the wheel base either the wheel must slip by
an amount equal to the difference of length or the axle move
slightly outwards to provide a tread of longer diameter over
the outer rail and smaller diameter over the inner rail.

20. Adzing of Sleepers:
In order to obtain an inward slope of 1 in 20 for the rail,
sleepers are adzed to form a table at this slope at the rail
seat.
This process is known as adzing of sleepers. Generally
adzing is done for wooden sleepers.
For smooth and comfortable journey accurate adzing is
required.
1 in 20
slope
1 in 20
slope

21. Use of canted base plate

22. Advantages of coning the wheels
 (i) Coning the wheels reduces the
depreciation of the wheel rims and
rails. Depreciation is caused because
of the friction action of rims with inner
faces of the rail top.
 (ii) Coning also gives an option of lateral
drift of
the hinge with is wheels.
 (iii) Coning also prevents, to some
extent, the

23. • Thanks