Fishplate
Encyclopedia
In rail terminology
Rail terminology
Rail terminology is a form of technical terminology. The difference between the American term railroad and the international term railway is the most obvious difference in rail terminology...

, a 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
Rail tracks
The track on a railway or railroad, also known as the permanent way, is the structure consisting of the rails, fasteners, sleepers and ballast , plus the underlying subgrade...

. The name is derived from fish, a wooden bar with a curved profile used to strengthen a ship's mast. The top and bottom edges are tapered inwards so the device wedges itself between the top and bottom of the rail when it is bolted into place. In rail transport modelling
Rail transport modelling
Railway modelling or model railroading is a hobby in which rail transport systems are modelled at a reduced scale...

, a fishplate is often a small copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...

 or nickel silver
Nickel silver
Nickel silver, also known as German silver, Argentann, new silver, nickel brass, albata,, or alpacca, is a copper alloy with nickel and often zinc. The usual formulation is 60% copper, 20% nickel and 20% zinc. Nickel silver is named for its silvery appearance, but it contains no elemental silver...

 plate that slips onto both rails to provide the functions of maintaining alignment and electrical continuity.

History

The device was invented by William Bridges Adams
William Bridges Adams
William Bridges Adams was an author, inventor and locomotive engineer.-Overview:He is best known for his patented Adams Axle — a successful radial axle design in use on railways in Britain until the end of steam traction in 1968 — and the railway fishplate...

 in May 1842, because of his dissatisfaction with the scarf joint
Scarf joint
A scarf joint is a method of joining two members end to end in woodworking or metalworking. The scarf joint is used when the material being joined is not available in the length required...

s and other systems of joining rails then in use. He noted that to form the scarf joint the rail was halved in thickness at its ends, where the stress was greatest. It was first deployed on the Eastern Counties Railway
Eastern Counties Railway
The Eastern Counties Railway was an early English railway company incorporated in 1836. It was intended to link London with Ipswich via Colchester, and then on to Norwich and Yarmouth. Construction began in late March 1837 on the first nine miles, at the London end of the line.Construction was...

 in 1844, but only as a wedge between the adjoining rails. Adams and Robert Richardson patented the invention in 1847, but in 1849 James Samuel
James Samuel
James Samuel was a railway engineer who was appointed engineer to the Eastern Counties Railway in 1846. He held two important patents: the first mechanism for the compounding of steam locomotives, granted in 1850, and the railway fishplate of 1844. In both cases, however, the invention was the...

, the engineer of the ECR developed fishplates that could be bolted to the rails.

Electrical connection

When railway lines are equipped with track circuit
Track circuit
A track circuit is a simple electrical device used to detect the absence of a train on rail tracks, used to inform signallers and control relevant signals.- Principles and operation :...

s, or where the line is electrified for electric traction, the electrical connection provided by fishplates is poor and unreliable and has to be supplemented by bonding wire fixed to the two rails either side of the joint by spot welding or other means.

Welded rail

Even though fishplates strengthen the weak points represented by rail joints, improvements can still be made. For example, the joints can be welded together using the thermite welding process.

Turnouts

The moving blades of a set of points can be connected to the stock rails by looser than normal fishplates. This is called a heeled switch. Alternatively, the blade and stock rail can be a one piece heel-less switch, with a flexible thinned section to create the moving heel.

Examples of fishplates

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