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A bank engine (United Kingdom/Australia) (colloquially a banker), banking engine, helper engine or pusher engine (North America) is a
railway Rail transport (also known as train transport) is a means of transport that transfers passengers and goods on wheeled vehicles running on rails, which are incorporated in tracks. In contrast to road transport, where the vehicles run on a p ...
locomotive A locomotive or engine is a rail transport vehicle that provides the motive power for a train. If a locomotive is capable of carrying a payload, it is usually rather referred to as a multiple unit, motor coach, railcar or power car; the ...
that temporarily assists a
train In rail transport, a train (from Old French , from Latin , "to pull, to draw") is a series of connected vehicles that run along a railway track and transport people or freight. Trains are typically pulled or pushed by locomotives (often ...
that requires additional
power Power most often refers to: * Power (physics), meaning "rate of doing work" ** Engine power, the power put out by an engine ** Electric power * Power (social and political), the ability to influence people or events ** Abusive power Power may a ...
or traction to climb a
gradient In vector calculus, the gradient of a scalar-valued differentiable function of several variables is the vector field (or vector-valued function) \nabla f whose value at a point p is the "direction and rate of fastest increase". If the gr ...
(or ''bank''). Helpers/bankers are most commonly found in mountain divisions (called "helper districts" in the United States), where the
ruling grade The term ruling grade is usually used as a synonym for "steepest climb" between two points on a railroad. More simply, the steepest grade to be climbed dictates how powerful the motive power (or how light the train) must be in order for the run ...
may demand the use of substantially greater motive power than that required for other grades within the division.


Historic practice

Helpers/bankers were most widely used during the age of steam, especially in the
American West The Western United States (also called the American West, the Far West, and the West) is the region comprising the westernmost states of the United States. As American settlement in the U.S. expanded westward, the meaning of the term ''the Wes ...
, where significant grades are common and trains are long. The development of advanced braking systems and diesel-electric or
electric locomotive An electric locomotive is a locomotive powered by electricity from overhead lines, a third rail or on-board energy storage such as a battery or a supercapacitor. Locomotives with on-board fuelled prime movers, such as diesel engines or g ...
s has eliminated the everyday need for bankers/helpers in all but a few locations. With the advent of
dynamic brake Dynamic braking is the use of an electric traction motor as a generator when slowing a vehicle such as an electric or diesel-electric locomotive. It is termed " rheostatic" if the generated electrical power is dissipated as heat in brake grid ...
s on electric or diesel-electric locomotives, helpers/bankers can also be used to provide more braking force on long downhill gradients. Bankers or helpers were historically positioned at the rear of the train, in which case they also protected against
wagons A wagon or waggon is a heavy four-wheeled vehicle pulled by draught animals or on occasion by humans, used for transporting goods, commodities, agricultural materials, supplies and sometimes people. Wagons are immediately distinguished from ...
or
coaches Coach may refer to: Guidance/instruction * Coach (sport), a director of athletes' training and activities * Coaching, the practice of guiding an individual through a process ** Acting coach, a teacher who trains performers Transportation * Coac ...
breaking away from the train and running back downhill. Also, in a pusher role, it was possible for the helper/banker to easily separate once the train had crested the grade. Once separated, the banker would return to a siding or stub so as to clear the mainline and get ready for the next train. A common practice with knuckle couplers was to remove the knuckle from the front coupler. The locomotive would be brought up behind the last car of the train while the train was moving slowly. The air brake hose would not be coupled. When the train no longer required assistance, the helper/pusher would slow, then reverse and coast back down the grade to its siding at the bottom of the grade. This practice was outlawed in North America after the end of the steam era. Special heavily constructed
caboose A caboose is a crewed North American railroad car coupled at the end of a freight train. Cabooses provide shelter for crew at the end of a train, who were formerly required in switching and shunting, keeping a lookout for load shifting, dam ...
s were sometimes used in helper areas. Ordinary cabooses were built as lightly as practical and might be crushed by the helper/pusher's force, which could be as much as 90 tons. The heavy cabooses allowed crews to avoid the time-consuming procedure of splitting the train just ahead of the caboose. Pushers/helpers were commonly designed to provide extreme power for very short runs; as a result they could not push at full power for very far before steam pressure dropped. If it could push enough to get the train to the top of the grade, then it could build up pressure while coasting back down and while waiting for the next train to come along. This practice was common in Europe. Since it was not possible to remotely control a
steam locomotive A steam locomotive is a locomotive that provides the force to move itself and other vehicles by means of the expansion of steam. It is fuelled by burning combustible material (usually coal, oil or, rarely, wood) to heat water in the loco ...
, each helper had to have a full crew on board. Careful coordination was required between engine crews to assure that all locomotives were operated in a consistent manner. Standard whistle signals were employed to tell the helper crew when to apply power, drift or
brake A brake is a mechanical device that inhibits motion by absorbing energy from a moving system. It is used for slowing or stopping a moving vehicle, wheel, axle, or to prevent its motion, most often accomplished by means of friction. Backgroun ...
. A misunderstanding of signals by a pusher locomotive crew could result in a major wreck if the lead locomotive applied brakes while the bank engine was still applying power. The usual result was that the train would experience a violent run-in (an abrupt bunching of train slack), resulting in the
derailment In rail transport, a derailment occurs when a rail vehicle such as a train comes off its rails. Although many derailments are minor, all result in temporary disruption of the proper operation of the railway system and they are a potentially ...
of part or all of the train. The town of Helper, Utah was named after these engines, as it was where helper engines were kept to assist on the climb to
Soldier Summit A soldier is a person who is a member of an army. A soldier can be a conscripted or volunteer enlisted person, a non-commissioned officer, or an officer. Etymology The word ''soldier'' derives from the Middle English word , from Old French ...
.


Modern practice

Nowadays helpers/bankers are often controlled by coded radio signals from the locomotive at the head end of the train, allowing one engineer (driver) to simultaneously control the helper(s) and the train being helped. If radio operation is not possible, electrical control might be used, by way of cables running the length of the train (especially in case of passenger trains). Alternatively, radio communication with the lead engine's driver facilitates manual operation, which is still the norm for bank engines at the end of freight trains in Europe.


At the front

In the UK, an engine that was temporarily attached to the front of a train to assist with the ascent of an incline was called a ''pilot locomotive''. This differentiated it from the ''train engine(s)'' that powered the train to its destination. A train with one or more locomotives attached to the front may be described as a " double header", "triple header", etc., depending on the number of helpers/bankers even when this lash-up of power was used for the entire run. These terms gradually fell out of general usage as
diesel locomotive A diesel locomotive is a type of railway locomotive in which the prime mover is a diesel engine. Several types of diesel locomotives have been developed, differing mainly in the means by which mechanical power is conveyed to the driving whee ...
s replaced
steam power A steam engine is a heat engine that performs mechanical work using steam as its working fluid. The steam engine uses the force produced by steam pressure to push a piston back and forth inside a cylinder. This pushing force can be tra ...
, and are not used for the common assemblage of several power units.


Mid-train

In countries where buffers-and-chain couplers are used, bank engines often cannot be added to the front of the train due to the limited strength of the couplers; In the case of standard UIC couplers and a maximum grade of 28
Per mille (from Latin , "in each thousand") is an expression that means parts per thousand. Other recognised spellings include per mil, per mill, permil, permill, or permille. The associated sign is written , which looks like a percent ...
(which is common, ''e.g.'', for lines through the
Alps The Alps () ; german: Alpen ; it, Alpi ; rm, Alps ; sl, Alpe . are the highest and most extensive mountain range system that lies entirely in Europe, stretching approximately across seven Alpine countries (from west to east): France, Sw ...
), the limit is a train weight of 1400 tons; if a train is heavier, bank engines have to be added in the middle or to the end of the train in order not to exceed the maximum load for any coupler. Adding locomotives in the middle of the train has the distinct advantage of applying the helper power to only part of the train, thus limiting the maximum drawbar pull applied to the first car of the train to a safe level. The narrow
gauge Gauge ( or ) may refer to: Measurement * Gauge (instrument), any of a variety of measuring instruments * Gauge (firearms) * Wire gauge, a measure of the size of a wire ** American wire gauge, a common measure of nonferrous wire diameter, es ...
portions of the
Denver and Rio Grande Western Railroad The Denver & Rio Grande Western Railroad , often shortened to ''Rio Grande'', D&RG or D&RGW, formerly the Denver & Rio Grande Railroad, was an American Class I railroad company. The railroad started as a narrow-gauge line running south from De ...
, in particular, used "swing helpers", which meant the helper locomotives were placed mid-train at a point where they were pushing and pulling an approximately equal amount of tonnage, said location being referred to as the train's "swing point". This was also done to balance out the "slack" in the train between the locomotives, the swing helpers, and the end train helpers just in front of the caboose. However, this arrangement requires splitting the train in order to add or remove the helper engine(s), which can be a time-consuming maneuver. However, on some American railroads it was necessary to an extent, because operating rules required end of train helpers to be added at the end of the train, but in front of the
caboose A caboose is a crewed North American railroad car coupled at the end of a freight train. Cabooses provide shelter for crew at the end of a train, who were formerly required in switching and shunting, keeping a lookout for load shifting, dam ...
. This was done for the safety of the train crew riding inside the caboose.


End of the train

To be able to add and remove helper locomotives quickly, which is especially important in Europe due to the high traffic density, they are usually added to the end of the train. Normally, they are coupled and the air hoses are connected, which is necessary for the air brake to work correctly ''e.g.'', in emergency situations, but in special cases trains are banked with uncoupled locomotives, which can be added or removed "in-flight." In the UK it was a usual practice for banking locomotives to follow and buffer-up to a slow-moving assisted freight train without coupling (as demonstrated in archive films of banking on the
Lickey Incline The Lickey Incline, south of Birmingham, is the steepest sustained main-line railway incline in Great Britain. The climb is a gradient of 1 in 37.7 (2.65% or 26.5‰ or 1.52°) for a continuous distance of two miles (3.2 km). Constructed ...
) before applying more power, thus precluding the need for a standing start. Following an accident in 1969 this practice was discontinued. This procedure is not performed in North America, as it would violate Canadian and United States safety regulations.


Accidents

*
Chapel-en-le-Frith Chapel-en-le-Frith () is a town and civil parish in the Borough of High Peak in Derbyshire, England. It has been dubbed the "Capital of the Peak", in reference to the Peak District, historically the upperland areas between the Saxon lands ( ...


See also

* Distributed power * Double-heading *
Station pilot A switcher, shunter, yard pilot, switch engine, yard goat, or shifter is a small railroad locomotive used for manoeuvring railroad cars inside a rail yard in a process known as ''switching'' (US) or ''shunting'' (UK). Switchers are not inten ...


References

{{Reflist Rail transport operations