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TRACK FITTINGS AND FASTENINGS
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FASTENING SYSTEM Rail fastening system is a means of fixing rails to sleepers Used to keep rails in proper position Important fittings are:
FISH PLATES SPIKES BOLTS CHAIRS BLOCKS KEYS PLATES
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FISH PLATES
Fishplate, splice bar or joint bar is a metal bar that is bolted
to the ends of two rails to join them together in a track
Maintain the continuity of rails & to allow for expansion
and contraction of rail due to temperature difference.
Maintain correct alignment of line both horizontally &
vertically.
Fishplate is a small copper or nickel silver plate that slips
onto both rails
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FISH BOLTS
BONE SHAPED FISH PLATE
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REQUIREMENTS OF FISH PLATES
They must support the underside of rail and top of the foot
They should allow free movement of rails for expansion &
contraction. For this They should not touch the web of rail
They should bear stresses due to lateral & vertical bending moments
They should hold ends of rail both laterally in line and vertically in
level
They should not wear due to impact, expansion & contraction
Length of fish plate should not exceed 457mm in India.
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FISH BOLTS
Holes are drilled through plates and web of rails and then
fish bolts and nuts are provided in these holes.
Alternate holes are made elongated and oval shaped so
that bolts in the rails will not be turned by vibrations.
Holes are made of larger diameter generally 5mm- 6mm
to allow for expansion & contraction.
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Bone shaped Fish plateRail
Hole for Fish bolt
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SPIKES To hold rails to wooden sleepers. A rail spike is a large nail with an offset head that is used
to secure rails and base plates to sleepers
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REQUIREMENTS
The spike should be
Strong enough to hold rail in position & enough resistance
to motion to retain its position
Cheap in cost
Deep as possible for better holding power
Easy in fixing and removal from sleepers
Capable of maintaining the gauge
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DOG SPIKES Commonly used Hold rail flanges with timber sleepers Shape of head of spike resembles ear of dog ,hence called
dog Spike Section of spike is square – shape & bottom part is either
pointed or chisel shaped Cheapest, easy in fixing and removing from sleepers Maintain better gauges
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DOG SPIKES
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Important points to be noted:
1. Driving:
Plays an important role in determining the holding power of spike.
Driven in a staggering manner. If spikes are placed opposite to
each other they have a tendency to split sleeper and have less
holding power
2. Blows:
Blows to spike should be centric & regular. Otherwise result in
larger holes.
DOG SPIKES
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3. Boreholes:
Spikes driven into bored holes have slightly smaller section
than boreholes & have greater holding power than when
driven without boreholes and also crushing of sleepers can be
reduced.
4. Number:
No. of dog spikes is 2 per each rail.
For heavy traffic ,upto 3-4.
On bridge sleepers, no. is 4 per each rail joint.
DOG SPIKES
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5. Auger Dog spikes are bored using 13mm auger. Holes are bored vertically through sleeper Verticality is essential otherwise connections will be
loose , gauge will be widened , hole become widened and sleeper will decay.
6. Plugging Due to heavy traffic, when dog spikes gets loose it is
driven out and hole is plugged with wooden plug. Another hole is bored and dog- spike is redriven there. Plugged holes are called spike killed holes.
DOG SPIKES
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SCREW SPIKES Tapered screws with V- threads used to fasten rails with
timber sleepers. Head is circular with square projection
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Holding power is double that of dog- spike Resist lateral thrust in better way More costly Gauge maintenance is more difficult Driving operations are similar to dog -spikes
SCREW SPIKES
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ROUND SPIKES
Head either cylindrical or hemispherical
Used for fixing chairs of bull headed rails to wooden
sleepers
Limited use only
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ELASTIC SPIKES To overcome the problems of dog- spikes head absorbs the
wave motion of rail without getting it loose. Provide better grip and result in reduction of wear and tear
of rail Commonly used in British railways
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BOLTS
1. FANG-BOLT
Alternative to round spikes
Not in much use due to difficulty in fixing and removing bolt
19mm in dia and of sufficient length to pass through sleeper
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2. FISH BOLT
Made of medium carbon steel
Length of bolt depends on type
of fish plate used
Too much tightening is prohibited as it prevents free expansion
& contraction of rails
Nuts are made of sufficient length to provide a good grip on the
bolt with square or hexagonal shape
BOLTS
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CHAIRS AND KEYS
For double headed & bull headed rails chairs are used to support
them in position
Made up of cast iron
Distribute load from rails to sleepers
Chairs have been fixed to the sleeper using wooden spikes screws,
fang-bolts or spikes
Chair consist of 2 jaws & a rail seat
Web of rail is held in inner jaw of chair and a key is driven
between rail and outer jaw of chair
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KEY
RAIL
CHAIR
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Chairs are fixed to sleepers using 3 spikes
Keys may be of wood or metal and may be either straight or
tapered
Wooden keys are cheap
Initial cost of steel keys is high. But life is about ten times more
than wooden keys. So steel keys are preferred
CHAIRS AND KEYS
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STEWART’S KEY
Stewart’s key: steel plate bend in the form of letter E and a
steel wedge.
Steel wedge to keep the key tight against rail web and outer
jaw of chair
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BEARING PLATES
Rectangular plates of Mild steel or cast iron
Used below flat footed rails to distribute the load on a
larger area of timber sleepers
Placed below rails carrying heavy vehicles at high speed
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Advantages:-
Distribute load to sleepers over a large area and prevent
sinking of rail in soft wooden sleepers
Prevent destruction of sleepers due to rubbing action of rail,
increase life of sleeper
Help in firm and perfect holding of spikes to sleepers which
prevent shifting of rails
Better maintenance of gauge
BEARING PLATES
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Disadvantages:-
Plates rattle when loose
When any hole for a spike is failed and a new hole is to be
made , all spikes in the bearing plate have to be pulled out
which affects good hold of spikes.
When bearing plates are loose , they admit moisture and
result in mechanical wear of sleepers
BEARING PLATES
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Thank you…