UNIT 2 Railway Engg

1. Unit 2: Railway Engineering

2. Features Rail Transport Road Transport
Tractive resistance The movement of steel wheels on steel rails has
basic advantage of low rolling resistance. This
reduces haulage costs because of low tractive
resistance.
The tractive resistance of a pneumatic tyre on
metalled roads is almost five times compared
to that of wheel on rails.
Right of entry A railway track is defined on two rails and is within
protected limits. Trains work as per a prescribed
schedule and no other vehicle has the right of entry
except at specified level crossings.
Roads, though having well-defined limits, can
be used by any vehicular traffic and even by
pedestrians they are open to all.
Cost analysis Owing to the heavy infrastructure, the initial as
well as maintenance cost of a railway line is high.
The cost of construction and maintenance of
roads is comparatively cheaper.
Gradients and
curves
The gradients of railway tracks are flatter (normally
not more than 1 in 100) and curves are limited up
to only 100 on broad gauge.
Roads are constructed normally with steeper
gradients of up to 1 in 30 and relatively much
sharper curves.
Flexibility of
movement
Due to the defined routes and facilities required for
the reception and dispatch of trains, railway can be
used only between fixed points.
Roads transports have much more flexibility
in movement and can provide door to door
sevices.
Environmental
pollution
Railway has minimum adverse effects on the
environment.
Road transport creates comparatively greater
pollution than the railways.
Organization and
control
Railways are government undertakings, with their
own organization.
Barring member state government transport,
road transport is managed by private sector.
Suitability Railways are best suited for carrying heavy goods
and large number of passengers over long
distances.
Road transport is best suited for carrying
lighter goods and smaller number of
passengers over short distances.

3. Rail Joints
Fish Plate
Fish Bolt
Gap
Rail
• Rail joints are necessary to hold the adjoining ends of the rails in
correct position; both in horizontal as well as vertical planes
• Between two ends a gap for expansion due to temperature variation
is provided
•Joints are weakest part in a railway track; almost 50% strength is
reduced

4. Types of rail joints
Supported joint Suspended joint
Welded joint: Life is more,
comfort in travel, creep is less,
continuity for electric traction,
better performance, maint. less
Bridge joint
Square Joints: for straight track, joints
are directly opposite to each other
Staggered Joints: On curved track
joints are not opposite to each other Insulated Joints: insulator is
added to break the current.
Bridge plate Welded joint

5. Welding of Rails
• Purpose:
To increase the length of rail by joining two or more rails
and thus to reduce the number of joints and requirement for
fish plates (Economy & Strength)

6. Advantages of welding of rails
1. It satisfies condition of perfect joint & hence increases the life
of rail and reduces the maintenance cost by 20 to 40%
2. It reduces the creep due to increase in length of rail
3. Expansion effect due to temperature is reduced
4. Due to discontinuity of joints, a source of weakness is reduced
5. Long rail length being heavier, dampen the intensity of high
frequency vibrations due to moving loads
6. Welding increases life of rails due to decrease in wear at joints

7. Short and Long Welded rails
1. SWR:
• It contracts and expands throughout its length due to temperature
variations
• These are welded into 3, 5 or 10 rail lengths (1 rail length is equal to
13m for B.G. and 12m for M.G.)
2. LWR:
• It is the one whose central part does not undergo any longitudinal
movement and only end portions are affected due to temperature
variations
• Minimum length of 200m for B.G. and 300m for M.G. functions as
LWR
• Maximum length is prescribed as 1km