RAIL FIXTURES & FASTENINGS
All those fittings which are required for connecting the rails end to end and for fixing the rails to the sleepers in a track are known as fixtures and fastenings.
They include -
1) Fish plates
2) Spikes
3) Bolts
4) Chairs
5) Keys
6) Blocks
7) Bearing plates
The different functions of these fitting are :
1) To keep the rails in the proper positions.
2) Connection of rail to rail.
3) To set points and crossings properly
4) To allow for expansion and contraction of rails.
The various types of fixtures and fastenings listed above are briefly described below :
FISH PLATES : These plates are used to maintain proper alignment of the rail line. They maintain the continuity of the rails and also allow expansion or contraction of rails caused due to temperature variations.
Generally these plates are made of mild steel and 20 mm in thickness.
They are 45.6 cm long and provided with 4 no. of 32 mm diameter holes at 11.4 center to center.
Indian railways generally adopt following two types of fish plates :-
1) Bone shaped fish plate
2) Increased depth fish plate
Bone shaped fish plate is used for connecting flat footed rails. The increased depth fish plate is generally used for connecting Bull-headed rails.
SPIKES : They are used to hold the rails to the wooden sleeper. A good spike should have following qualities :
1) It should have sufficient strength to hold the rail in position.
2) It should help in maintaining proper gauge.
3) It should be easy to fix and replace from the sleepers.
Indian Railways use following types of spikes :-
1. Dog spikes
2. Screw spikes
3. Round spikes
4. Standard spikes
5. Elastic spikes
BOLTS : They are used for connecting :
1) Fish plates to the rails at each rail joint.
2) Chairs or bearing plates to timber sleepers.
3) Sleepers to bridge girders,etc
The different types of bolts used in Indian Railways are :
1. Hook bolts
2. Fish bolts
3. Fang bolts
4. Rag bolts
Hook bolts are used for fixing timber sleepers to bridge girders. They are popularly known as dog bolts.
Fish bolts are used to connect fish plates to the rails at rail joints.
Fang bolts are used for fixing side chairs to the sleepers.
Rag bolts are generally used to connect longitudinal timber sleeper or concrete sleepers to the walls of ash pits.
CHAIRS : They are used to hold the double headed and bull headed rails in required position. They are made of cast iron having two jaws and a rail seat. In order to fix the double headed or bull headed rail to a chair, the rail is placed between the two jaws of the chair.
KEYS : They are small tapered pieces of timber or steel to connect rails to chairs on metal sleepers.
Types of keys generally used are :
1) timber keys
2) metal keys
3) Stuart's keys
4) Morgan keys
BLOCKS : They are inserted in between the two rails running close to each other and bolted to maintain the required distance They may touch either the webs or the finishing faces or both.
BEARING PLATES : They are the plates placed in between the flat footed rails and timber sleepers on a track. They serve as chairs for flat footed rails. They are made of cast iron, wrought iron or steel. Generally, they are of following types :
1) Flat bearing plates
2) canted bearing plates
Flat bearing plates are used at locations where rails are laid flat. Also they are used in turn out tracks under points and crossings.
Canted Bearing plates are used on soft timber sleepers beneath outside rail on curves, on sleepers placed on either side of rail joints, bridges etc. where rails are laid at an inward tilt of 1 in 20.
