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Calling-on Signal

Used to indicate that a driver may move passed a stop signal at danger to a predetermined location, or the adjacent signalbox from where he would receive further instructions.


The amount that one running rail is raised above the other on curves to improve stability. Usually expressed in inches. Sometimes known as "Super-elevation".

Cant Deficiency

Expressed in inches, it is a measure of the extra cant that would have to be added to the rails around a particular curve at a particular running speed to completely cancel out the lateral cornering force.

Cant Rail

In the construction of a railway coach, the timber or steel rail running along the top of the body-side. It is "canted" in that the top is angled to match the roof profile.

Caprotti Valve Gear

Type of steam locomotive valve gear utilising poppet type valves. Invented by the Italian engineer, Arturo Caprotti, it was claimed to improve engine efficiency. In practice it proved hard to maintain and was not as efficient as long-travel piston valves.

Cardan Shaft

A power-transmitting shaft which has a universal joint at each end.

Carello Italiano

See: Mogul Locomotive.


A passenger carrying railway vehicle. Also commonly referred to as coaches. The coach shown is based on the LMS/BR SERIES III coach, these were built in the 1930's and still used by BR into the mid - late 1960's.
Photograph courtesy of

Carriage Body

Originally the term given to each individual compartment of a carriage, but later referring to the whole of the part above the sole-bar. The term was used since the first railway carriages were assembled by bolting together what were usually manufactured as individual stage-coach bodies onto a single under-frame.

Carrying Wheels

Any locomotive wheels which are normally not driven.

Cartazzi Axle

A two-wheeled truck with side movement imparted by diagonal slides.

Catch Handle

The small spring-loaded locking-lever or `catch' at the end of a points or signal operating lever. The catch must be raised before it is possible to move the lever proper.

Catch-Handle Locking

A system of interlocking in a lever frame, where the mechanism is activated by raising the catch handle rather than moving the lever proper.

Catch Points

Catch points are used to deliberately derail vehicles running away in the wrong direction on a running line.

See also: Trap Points.


That part of the overhead wiring on electric railways, which hangs between the supporting masts and from which the dropper wires are hung.

Cattle Dock

A short platform in a goods yard incorporating penned enclosures from which livestock can be loaded on to trains.

Cattle Truck

A covered goods van with open slatted sides, designed particularly for the transport of livestock.


The area alongside and below the level of a railway track into which rain water is drained.

Chain Shunting

A system of shunting (illegal in some countries) in which a locomotive on one track hauls vehicles on adjacent track by means of a long chain.


A metal casting which is bolted to a sleeper and grips the rail to hold it in place.


That part of a railway vehicle comprising the main frame, trucks (if any), wheels, draw-gear, buffing gear and engine (if this is mounted on the main frame).

Chauldron Wagon

A primitive coal wagon used in the early days of railways with a capacity of 36 bushels.


A guiding rail, located between the two running rails, and set close enough to one of the running rails to make contact with the back of a flange. Hence, such contact will prevent the opposite flange from making hard contact with the running rail on a sharp curve; or prevent the opposite flange from taking the wrong route at a rail crossing.


The tube on top of a steam locomotives smoke-box through which the exhaust gases to escape to atmosphere.

Clack Valve

A one way valve used to allow water to enter the boiler while preventing the steam escaping.


A thin covering, usually of sheet metal, over a steam-locomotive's boiler lagging.

Clearance Volume

This is the cylinder and connecting pipe volume at the beginning of a piston stroke just before the steam valve is opened. It is important to minimise this volume as this reduces the steam pressure that acts on the piston. See: Steam Engine Performance.

Clearing Point

A position 440 yards in advance of the outermost home signal of station limits, and to which position the line must be clear before a train can be accepted into the block section in rear.


Raised centre section of a carriage roof, usually with ventilation and glazing, to admit extra light into the centre of the coach. Particularly used in the days of oil lighting, it was discontinued in the early years of this century in view of the increased cost and complexity of construction and maintenance.


Incombustible impurities in coal can form lumps (clinker) blocking the flow of air through the fire, thus reducing steam production. Clinker must therefore be broken up whenever it forms so that it can drop through the grate, or be removed via the fire-hole.

Co-Acting Signals

Signals in which the indication is duplicated in two different positions on the same post.


A passenger carrying railway vehicle, or a goods or guards vehicle with the appearance of a passenger vehicle. Also commonly referred to as carriages.
Photograph courtesy of coachkits.

Coaching Stock

Any vehicles, passenger or otherwise, which is designed for use in passenger trains.

Coaling Stage

A platform on which coal is stacked ready to be loaded onto a locomotive. This could be a small platform just a few feet above rail level, or a large tower holding several wagon loads of coal.

Colour-Light Signal

Signals which are indicated by colour lights only, and which are bright enough to be observed in daylight.

Combination Lever

A rod on Walschaerts valve-gear joining the radius rod, valve rod and union link.

Combination Link

A rod on Walschaerts valve-gear joining the radius rod, valve rod and union link.


Seating area in a carriage separated off from other passengers by partitions. In a corridor coach, the compartment only occupies part of the width of the coach and has a door leading from it into the corridor

Compartment Coach

Carriage with seating arranged in compartments. (cf. Open coach)


Carriage with seating for passengers of different classes.

Compound Engine

To maximise efficiency on steam locomotives, some were designed to use steam at high pressure in one or more cylinders. Exhaust steam from those cylinders then drove other low-pressure cylinders before finally being exhausted to atmosphere.

Condensing Locomotive

A steam locomotive in which the exhaust steam is condensed and then pumped back into the boiler.

Conjugated Valve Gear

A valve gear in which the movement of the inside valve of a three-cylinder steam locomotive is derived via a system of levers from the two outside valve-gears.

Connecting Rod

The rod transmitting thrust from the pistons to the crank pin of the driving axle.


A locomotive, which according to the Whyte classification is of the 2-8-0 wheel arrangement.

Contact Wire

That part of the overhead wiring in railway electrification to which the pantograph of the moving vehicle makes contact.

Continuous Brakes

Brakes that are connected to adjacent vehicles in a train to form one continuous braking system controlled from the locomotive, thus providing an adequate braking force no matter the length of the train. Continuous brakes are arranged so that if vehicles become accidentally detached from the locomotive the brakes are automatically applied. Brake application devices are also available to the guard and in passenger vehicles for emergency use, but only the driver can release the brakes.


A department of a railway organisation which makes decisions and directs the movement of trains and train workers.

Corridor Coach

A railway coach with an inter-connecting passageway between compartments.

Corridor Connection

A narrow flexible section at the end of a coach designed to be secured to a similar section on another coach, thus providing a passageway between coaches.

Corridor Tender

A tender incorporating a passageway through it and a corridor connection to the coaches to which it might be attached.

Cossart Valve-Gear

Valve gear with four piston valves per cylinder operated by rotary cams.


A wedge used to secure a removable bearing or lever.

Coupled Wheels

Wheels of a locomotive which are forced to run in synchronism by mechanical connections.

Coupling Rod

These couple driving wheels of the same size together to spread the tractive effort over the coupled wheelbase.


Compartment in a railway coach with seats on one side only. In a Pullman car, however, used to refer to a private, usually four-seat, compartment.

Crane Tank

A tank engine which incorporates a small crane on its front or rear.


A rod or arm secured to an axle or rotating spindle, with the rod extending outwards at right angles to the axle or spindle.

Crank Axle

A locomotive driving axle with one or more U-shaped cranks extending from the part of the axle between the wheels.

Crank Pin

A rod or shaft extending out at right angles to a crank, and in line with, but offset from, the axle or spindle to which the crank is secured.

Crocodile Truck

Another term for a well wagon.

Cross-Country Line

A railway route which inter-connects two or more main trunk routes. Some routes which are cross-country lines according to this definition, but are of minor importance, might be known as branch lines.


A device connected to the outer end of a piston rod and which slides between guides to keep the rod correctly aligned to the cylinder during it's travel. The little- end of a connecting rod is also connected to the cross-head.


One rail crossing another on the same level.

Crossing Angle

The acute angle that one rail makes relative to the other at a crossing.


Two inter-connecting sets of points which allow a vehicle to cross from one track to a parallel track.

Crown Plate

The plate forming the firebox crown of a steam-locomotive boiler.

Crown Plate

The arched top plate of horn blocks.

Crown Stays

Strengthening stays between the inner and outer firebox crown plates.


Usually quoted as a percentage, this is the point in a piston stroke at which the supply of steam to the cylinder is cut off by the closing of the valves. Maximum cut-off (typically 75%) is used for starting a train and is reduced as the train accelerates and less effort is required. The amount of cut-off used is controlled by the driver via the reversing lever, or screw reverser in later designs. This process is also referred to as "notching up".


A hollow cylindrical-shaped device in which the power of a reciprocating engine is developed. In the case of a steam engine, it is here that the power of the steam is converted to mechanical motion.

Cylinder Drain Cocks

When a steam locomotive has been standing for a while, steam may condense in the cylinders as they cool. The resulting water, being incompressible, can result in damage to the cylinders and pistons when the locomotive then tries to move away. To prevent this, cylinder drain cocks are fitted; controlled from the cab, they should be opened while the locomotive is standing and not closed until after the locomotive starts to move. It is these that produce the typical large cloud of steam from the front of a locomotive when it first begins to move.