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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…