British railcars and diesel multiple units
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Diesel multiple units and Railcars are trains which does not have a separate locomotive. Railcars are single cars, multiple units are typically passenger trains with accommodation in every vehicle and a driving position at each end. The term is further classified by the method of propulsion e.g.: Diesel (DMU), Electric (EMU) or Diesel-Electric (DEMU).
This article describes the history, development and current use of railcars and diesel multiple units in Great Britain.
Origins
The GWR network included many minor routes and branch lines, and there was a need for more economical trains for lesser-used routes. Having borrowed an LSWR steam railmotor in 1903, the GWR developed their own range of steam rail-motors. These were single carriages, with a boiler and steam engine unit at one end, and a driving cab at both ends. As the railmotors could not haul additional vehicles, in the 1920s the GWR developed the auto-train for routes where the railmotor was insufficient. An autotrain comprised a suitably equipped steam locomotive that could be controlled from the driving cab of a special 'autocoach'. This arrangement avoided the need for the locomotive to run round the train at the terminus. Up to four autocoaches could be used in a train, with the locomotive in the middle, driven from either end like a multiple unit. Autotrains remained in use right through to the end of steam operation on British Railways in the 1960s.
As the last steam railmotors were being withdrawn in the mid-1930s, the GWR introduced a series of diesel railcars. Although most were single units, there were two sets of 'power twins' (pairs of single-cabbed railcars that operated together), a form of multiple unit that could be expanded to take additional centre coaches. The railcars were also successful and most survived into British Railways ownership, eventually being displaced in the late 1950s by the closure of unprofitable routes and the introduction of the 'first-generation' BR diesel multiple units.
The London Midland and Scottish Railway used a number of single diesel railcars and built a prototype streamlined multiple unit, prior to nationalisation.
First Generation DMUs
As part of the 1955 Modernisation Plan of British Railways, provision was made for a number of railcars or DMUs. The earliest of these were the "Derby Lightweights", built by BR's own Derby works, and they quickly became popular with crews (for the increased comfort compared to a steam loco), operating authorities (they were, and still are, cheaper to operate than a loco hauled train, and are much more flexible, requiring no run around) and passengers (they were much cleaner than the old steam hauled stock and if you were lucky enough you could get a view of the line ahead).
Over the next few years a number of different designs came about, though nearly all were able to operate together thanks to BR standardising on the 'Blue Square' coupling code for multiple working. Although there were a few design differences, the units could basically be classified as suburban (Doors for each seating bay, 3+2 seating in second class- an example is Class 118), Medium Density (2 doors per vehicle side, 3+2 bus style seating in second class- an example is Class 114), Cross Country (externally similar to Medium Density, 2+2 bus style seating in second class- an example is Class 120) and finally Intercity (Interiors to same standard as loco hauled stock- an example is Class 124).
Today around 300 vehicles survive in preservation, various vehicles (mainly 101s and 121/122s) survive in departmental use, and Chiltern Railways use a Class 121 on its Aylesbury-Princes Risborough Line.
The Southern Region of British Rail preferred Diesel Electric Multiple units for use on non electrified routes. Routes they were used on included London to Hastings (now electrified), London to Uckfield, Portsmouth to Southampton (now electrified) and Southampton to Salisbury. Each Unit consisted of a motor coach and a number of trailers in formations of between two and six coaches depending on the type.
By the early 1980s it had become apparent that the Modernisation Plan DMUs were showing their age, and needed replacement or refurbishment. As several were insulated with blue asbestos, which BR was obliged to eradicate from its stock, the problem was compounded. Many of the designs produced were of non-standard design meaning that the procurement of parts to keep the units running became increasingly hard. For the second generation, British Rail pursued two basic designs - the Class 14x Pacer series, which were based on Leyland bus parts and were intended to be low cost trains to be used on regional branch lines, and the Class 15x Sprinter series - based largely on the Mark 3 bodyshell design, and intended for more demanding commuter routes, and also medium distance inter-city work.
Second Generation DMUs
Pacer units
The Pacer series was the result of an experiment to see whether the possibility of using bus parts to create a diesel multiple unit was viable. The initial prototype, known as LEV-1, was a joint project by the British Rail Research Division and Leyland Motors using a bus body mounted on a modification of an existing freight vehicle underframe (HSFV1).
Sprinter units
Sprinters were intended for longer distance routes and were designed from the outset as rail vehicles - unlike the Pacers. Most were based on the Mark 3 bodyshell design with the exception of the single-car Class 153 and the later 158/159 units. Using technology proven on the continent in the form of Cummins engines and a Voith hydraulic transmission[disambiguation needed] gave the extremely high reliability required. There are 6 types of Sprinter (plus a prototype for a seventh type that did not make it into production). The first type to enter service was the BREL British Rail Class 150 with a high density layout suitable for short suburban services, quickly followed by the 150/2 with gangway between units and improved interior. For longer distance journeys there were the Leyland Class 155 and Metro-Cammell Class 156. These were fully carpeted with end doors, luxury unheard of at the time on the routes they operated. Some class 155 units were later split into two single car units with a new and very compact cab being grafted onto the inner ends forming Class 153. The conversion was undertaken by Hunslet. The class 153's are used on rural branchlines and for strengthening other services. For regional services the Class 158 was built. This offered near intercity levels of comfort with full air conditioning and a quiet interior. The last of the Sprinters to be built was the Class 159 for Network South East for use of the West of England Main Line between Exeter and London Waterloo. These were three car versions of the Class 158 with an upgraded interior.
Class 210
The British Rail Class 210 was a prototype DEMU. It was based on the then standard design of EMU (Classes 317 and 455) with a diesel engine mounted at the end of one of the driving cars. It was not a success due to weight and cost and the decision was made to order diesel hydraulic Sprinters.
Network Turbo
The Turbo family was originally a standardised model for diesel suburban services around London. There were two types, the first Class 165 was a two or three coach unit used on the Chiltern and Thames routes. This was followed by the Class 166 which featured air conditioning and seating more suited to longer distance services.
Privatisation
During the privatisation process, there was a gap of more than two years during which no new rolling stock orders were placed. The first new order placed was in May 1996 for a fleet of Class 168 Clubman DMUs for Chiltern Railways. These were a development of the Network Turbo design already in use by Chiltern and other operators, and themselves became the basis for the Class 170/171 Turbostar fleet which operate local and regional services throughout the country.
The Coradia is a family of multiple units produced by Alstom. The British diesel versions are the 100 mph Class 175 for First North Western's North Wales Services (later moving to Arriva Trains Wales) and the 125 mph Class 180 Adelante for First Great Western's semi-fast services. The (Class 185 Pennine) is in service on Transpennine Express services. The first train was unveiled in Germany in November 2005 and arrived in the UK a month later. The first train went into public service in March 2006 with deliveries of the 51 strong fleet continuing into 2006, and being complete in December 2006, now all 51 units are in operation
The Voyager family is a series of high speed DEMUs. Virgin Trains were looking to replace the Cross Country fleet as part of their franchise obligations. The new train had to replace a mixture of life expired loco-hauled trains and mid-life HSTs and have tilt for use on the West Coast Mainline. The result was the non-tilt Class 220 Voyager and tilting Class 221 Super Voyager. Midland Mainline and Hull Trains since ordered a non-tilt version. The Class 222 Meridian and Pioneer units replaced slower Turbostars on semi-fast mainline services.
References
Notes
Bibliography
General References
- Locomotives and coaching stock of 1986 (Platform 5)
- Locomotives and coaching stock of 1998 (Platform 5)
- Diesel multiple units 1979: (A.B.C)
External links
