B.
Back to back : The distance measured between the inside edges of the two wheels on an axle. This measurement is very important to see if your rolling stock will run through a piece of track that has check rails.
Backdrop : A painting or scenic photograph on the wall behind the layout. It can be as simple as a cloudless sky or it can echo the scenery of the layout and create an illusion of great distance.
Backscene : Printed or photographic scene on the wall behind the layout. Creates an illusion of distance.
Baker Valve Gear : A steam locomotive valve gear similar to Walschaerts valve gear, but one where sliding surfaces are eliminated.
Balance Weight : Weights cast into or secured to the coupled wheels of a steam locomotive to counterbalance the reciprocating and rotational out-of-balance forces.
Ballasting : The prototype track is laid on a bed of loose rock chippings, to provide drainage and support for the sleepers. In the model version this may be simulated by a foam rubber inlay or to be much more realistic, loose chippings held together with a dilute PVA mix.
Banana Van : A goods van incorporating steam heating to promote the ripening of fruit (especially bananas) during transit.
Banker : A banking locomotive was often used to assist trains up particularly steep or long banks, or gradients. Many banks had locomotives permanently allocated for this purpose. Trains would stop at the bottom of a bank, and the banker would buffer up to the rear (but not couple on). The train would then ascend the bank with the bankers assistance, and at the top the banker could drop off without the train needing to stop.
Baseboard : The platform on which a model railway is built.
Baseplate : The plate upon which flat bottom rail is laid so that it can be fastened down. Referred to as 'chairs' in model railway parlance.
Bay Platform : Terminating platform alongside the main through platform. Used mainly by local trains or for unloading parcel vans. Sometimes used for stabling locomotives.
Bell Code : The sequence of bells (block bells) used to communicate between signal boxes using a standardised code.
Bell Crank : A pair of cranks, free to rotate on the same spindle, with the crank arms secured approximately at right angles to each other.
Benchwork : Supporting framework for a model railway layout. L girder and open grid (sometimes called butt joint) are two popular types.
BFK : Brake First Coach.
Big End : The end of a connecting rod which connects to the crank pin on the driving wheel.
Big Four : Slang term for the four large railway companies which were formed from numerous smaller companies at the 1923 grouping:
Great Western Railway, London Midland and Scottish, London North Eastern Railway and Southern Railway.
Birdcage Brake : Type of Brake coach having a raised lookout for the guard to look along the train above the roofs of the other carriages.
Block Bell : Bells which are used for communication between signal-boxes.
Block Instrument : An electrically operated indicating device used in a signal-box. The instrument is connected with a similar device in an adjacent signal-box, and can be set to indicate whether or not the block section between the two signal-boxes is occupied by a train.
Block Post : A location under the control of a signalman, which may consist of a station, sidings, or simply a length of track where trains can be held for train-operation purposes.
Block Section : The length of track between the most advanced starting signal controlled by one signal-box and the outermost home signal controlled by the next signal-box. Entrance to this section of track is controlled by a signal which for safety reasons is normally at danger and hence the section remains "blocked" by this signal until a "line-clear" telegraphic-message is obtained from the block post in advance. With automatic signals, a block section is controlled automatically by train detection or remotely by centralised train control.
Block Train : A train, either passenger or goods, which is designed to run into and out of various locations without rearrangement of the rolling stock.
Bo-Bo : A diesel wheel arrangement indicated two four-wheeled driving bogies.
Bogie : Movable wheel unit on rolling stock connected to the underframe by means of a pivot. Enables far greater weight to be carried on even short wheel based rolling stock.
Bolster Wagon : A flat open wagon having horizontal bolsters (relatively narrow boards projecting above the surface of the wagon and running across the width of the vehicle). Thus the load was carried resting only on the bolsters, lifted clear of the base of the wagon. These allowed a rail, for example, to be carried on two "single bolsters" (four wheel wagons with a single bolster each). The bolster allowed freedom for the load to pivot as it went around corners.
Bracket signal : A semaphore signal array with two or more arms indicating different routes ahead. Often termed a junction signal.
Brake Coach : Carriage having a hand-brake for the use of the guard. Usually also has a luggage area, often with a pair (or two pairs) of double doors. (N.B. original spelling was "Break", although universally changed to Brake during the 19th century.)
Brake Hanger : A component of a railway vehicle which consists of a vertical bar which is pivoted at its top end; has a brake block attached near its middle; and has a brake operating mechanism connected to its bottom end.
Brake Van : A special vehicle which is fitted with brakes which can be applied from inside the vehicle. Can be a smallish van attached to the back end of goods trains to accommodate the guard, or a special coach added to passenger trains (full brake). Is also used to refer to the guards compartment of a brake coach.
Branch : A portion of railway that diverges from the main line to serve a town or industry.
British Rail : Formed in 1948 by nationalizing the existing `Big Four' railway companies, Great Western Railway, London Midland and Scottish, London North Eastern Railway and Southern Railway.
British Rail operated the entire national railway network until privatization in 1995, since when various sections have been sold to other operators.
Broad Gauge : A railway line laid to a gauge significantly wider than standard gauge.
Most significant use was the Great Western Railway which was originally laid to 7 foot gauge and was commonly referred to as Broad Gauge. In 1854 the GWR was regauged to the new standard gauge of 4 foot 8½ inches.
Ireland also uses 5 foot 3 inch gauge.
Brunel, Isombard Kingdom : The first Chief Mechanical Engineer of the Great Western Railway. He designed the entire line from Paddington to Bristol, followed by the Bristol and Exeter and then the South Devon. Advocate of the 7ft `broad gauge'. Famous for several other civil engineering works, including Box Tunnel and the Royal Albert Bridge over the Tamar at Saltash. He also designed steam ships, notably the Great Eastern and Great Western. Born 1807. He died in 1859, aged 52.
Buckeye : Modern automatic coupling hook.
Buffer : Sprung protruding devices at the extreme ends of railway vehicles, used to absorb the forces of acceleration and braking between vehicles.
Buffer Binding : The state of affairs where a curve is so sharp that one buffer of each of two adjacent vehicles compress together so much that they derail one of the vehicles.
Buffer Locking : The state of affairs where a curve is so sharp or the change of radius is so sudden that one buffer of each of two adjacent vehicles are displaced so much that they no longer touch; and, when the vehicles straighten up, the buffer heads of one vehicle slip behind those of the next vehicle.
Building Papers : Paper that has been printed to make it look like brickwork, roofing tiles etc. Very useful for scratch building or creating scenic details such as arches etc.
Bullhead Rail : This is rail having the same profile for upper and lower portions of the rail.
Bullied Valve Gear : A steam-locomotive valve gear, which in principle is similar to Walschaerts valve gear, but where the combination lever and eccentric rod are driven by chains from the driving axle. Named after its designer O.V.S.Bullied.
Bus : A main wire, or trunk wire, running under a model railroad. Shorter branch wires, such as track power feeders, are connected to it.