British Rail Class 25
Encyclopedia
The British Rail
British Rail
British Railways , which from 1965 traded as British Rail, was the operator of most of the rail transport in Great Britain between 1948 and 1997. It was formed from the nationalisation of the "Big Four" British railway companies and lasted until the gradual privatisation of British Rail, in stages...

 Class 25 diesel locomotive
Diesel locomotive
A diesel locomotive is a type of railroad locomotive in which the prime mover is a diesel engine, a reciprocating engine operating on the Diesel cycle as invented by Dr. Rudolf Diesel...

s were also known as Sulzer Type 2 and nicknamed Rats, as it was alleged they could be seen everywhere in Britain, and hence were "as common as rats". In total, 327 locomotives of this type were built between 1961 and 1967.

Background

The Class 24
British Rail Class 24
The British Rail Class 24 diesel locomotives, also known as the Sulzer Type 2, were built from 1958 to 1961. One hundred and fifty-one of these locomotives were built at Derby, Crewe and Darlington, the first twenty of them as part of the British Rail 1955 Modernisation Plan. This class was used as...

 locomotives were the precursor of the Class 25 design but after the delivery of their first few units it became apparent that the speed ceiling of 75 mi/h was unduly restrictive and the provision of a bit more power would be advantageous. In the course of normal development the power output of the Sulzer
Sulzer (manufacturer)
Sulzer Ltd. is a Swiss industrial engineering and manufacturing firm, founded by Salomon Sulzer-Bernet in 1775 and established as Sulzer Brothers Ltd. in 1834 in Winterthur, Switzerland. Today it is a publicly owned company with international subsidiaries...

 six-cylinder engine had been increased by 90 hp to give a continuous traction output of 1250 bhp at 750 rpm by the introduction of charge air cooling
Charge air cooler
A charge air cooler is used to cool engine air after it has passed through a turbocharger, but before it enters the engine. The idea is to return the air to a lower temperature, for the optimum power for the combustion process within the engine.Charge air coolers range in size depending on the...

 and the first locomotives to use this became known as Class 25 locomotives.

The Class 25 locos were primarily designed for freight work
Freight train
A freight train or goods train is a group of freight cars or goods wagons hauled by one or more locomotives on a railway, ultimately transporting cargo between two points as part of the logistics chain...

, but a significant number were fitted with boilers
Steam generator (railroad)
Steam generator is the term used to describe a type of boiler used to produce steam for climate control and potable water heating in railroad passenger cars...

 for heating passenger trains. Throughout the 1970s they could be found at work across the whole of the British Rail network although the Eastern and Southern Regions never had an allocation. Though regular performers into the early 1980s on Crewe
Crewe
Crewe is a railway town within the unitary authority area of Cheshire East and the ceremonial county of Cheshire, England. According to the 2001 census the urban area had a population of 67,683...

Cardiff
Cardiff
Cardiff is the capital, largest city and most populous county of Wales and the 10th largest city in the United Kingdom. The city is Wales' chief commercial centre, the base for most national cultural and sporting institutions, the Welsh national media, and the seat of the National Assembly for...

 passenger trains, they are best known in that respect for their use on the summer Saturday trains to Aberystwyth
Aberystwyth
Aberystwyth is a historic market town, administrative centre and holiday resort within Ceredigion, Wales. Often colloquially known as Aber, it is located at the confluence of the rivers Ystwyth and Rheidol....

, a task they relinquished in 1984. The final Class 25 locomotive was withdrawn from service in March 1987.

Class 25/0

Number sequence (original) D5151–D5175, (TOPS) 25 001–25 025


The first 25 locos became known as Class 25/0 and were built at the BR Darlington works using the newer 1250 hp "B" engine, modified generator assembly and traction motors. This increase in power was obtained from an air/water free flow intercooler fitted between a higher capacity pressure charger and inlet manifold, included within the normal cooling circuit to maintain simplicity. The cylinder head was also modified and strengthened.

The BTH
British Thomson-Houston
British Thomson-Houston was a British engineering and heavy industrial company, based at Rugby, Warwickshire, England. They were known primarily for their electrical systems and steam turbines. They were merged with the similar Metropolitan-Vickers company in 1928, but the two maintained their own...

 generator, type RTB 15656, was rated as 817.5 kW, 750/545 V, 1090/1500 A at 750 rpm, only slightly different from that used in the earlier Class 24s. (Note all Class 25 locomotives used a generator designated as BTH RTB 15656 but its rating and characteristics changed over time). The generator supplied four BTH 137BX traction motors connected in parallel and rated 245 hp, 545 V, 375 A at 560 rpm with a gear ratio of 18:79 (to give a 90 mi/h maximum speed). Maximum tractive effort was 39000 lbf (173.5 kN) and continuous tractive effort was 20800 lbf (92,523 N) at 17.1 mi/h, the latter standard for all Class 25s. Power at rail was 949 hp, now available between 9.3 and 77.6 mi/h. For the first fifteen locomotives fuel capacity was 520 gallons (design type 25 AV) and the final ten had larger 620 gallon fuel tanks installed (design type 25 BV).

Class 25/1

Number sequence (original) D5176–D5232, (TOPS) 25 026–25 082


The Class 25/1 locomotives were built at BR Darlington and Derby
Derby Works
The Midland Railway Locomotive Works, known locally as "the loco" comprised a number of British manufacturing facilities in Derby building locomotives and, initially, rolling stock in Derby, UK.-Early days:...

 locomotive works. They featured the new AEI
Associated Electrical Industries
Associated Electrical Industries was a British holding company formed in 1928 through the merger of the British Thomson-Houston Company and Metropolitan-Vickers electrical engineering companies...

 253AY traction motor, a result of the collaboration between BTH, MV
Metropolitan-Vickers
Metropolitan-Vickers, Metrovick, or Metrovicks, was a British heavy electrical engineering company of the early-to-mid 20th century formerly known as British Westinghouse. Highly diversified, they were particularly well known for their industrial electrical equipment such as generators, steam...

 and American builder Alco
American Locomotive Company
The American Locomotive Company, often shortened to ALCO or Alco , was a builder of railroad locomotives in the United States.-Early history:...

. This smaller, lighter motor was an attempt to market a traction motor to a worldwide audience, especially to the metre gauge lines. For Class 25 locomotives these lighter motors meant the discontinuance of other weight saving measures being built into the design. They were highly rated in an attempt to overcome the loss of tractive effort normally found on starting. The field divert system was also modified to allow increased capability throughout all the speed ranges.

The main generator was a 12-pole machine with the rating changed to 819 kW, 780/545V, 1050/1500A at 750 rpm. (The continuous rating has also been quoted as 819 kW, 630V, 1300A). The four traction motors were now connected as series parallel pairs being rated at 234 hp, 315V, 650A at 460 rpm, with a gear ratio 18:67. Pairs of motors connected in series provided a higher maximum tractive effort (usually quoted as 45000 lbf (200.2 kN) although 47000 lbf (209.1 kN) could be achieved) but the downside being that a series pair connected machine was more prone to slipping than one with an all parallel grouping. Full power was available between 7 and 77.5 mi/h, an improvement over Class 25/0 locomotives with all other ratings unchanged from the earlier series. The traction motor’s continuous rating of 650 amps was not far removed from its one hour short term or 'emergency' rating of 680 amps, and this could only be monitored manually. On heavy trains close monitoring of the ammeters was necessary to avoid motor damage. Though the body shell remained similar to D5151 there were a number of refinements. The air horns were relocated to either side of the headcode panel. The cab skirt and body fairing were discontinued, though the support lugs remained. A new driving control panel was fitted. The fuel and water tanks were also redesigned with a fuel capacity of 510 gallons (also quoted in sources as being 500 or 560 gallons).

There were initially two variants of this sub-class. The vast majority were boilered and designated 251 AV. The four without train heating were designated 251 BV. In due course, when it was decided to fit dual braking to a number of locomotives, those previously 251 AV became 251 CX and one of the 251 BV (25032) became 251 DX.

Class 25/2

Number sequence (original) D5233–D5299, D7500–D7597 (TOPS) 25 083–25 247


The Class 25/2 locomotives featured restyled bodywork and two-tone green livery similar to that carried by the Brush Type 4 (Class 47
British Rail Class 47
The British Rail Class 47, is a class of British railway diesel-electric locomotive that was developed in the 1960s by Brush Traction. A total of 512 Class 47s were built at Crewe Works and Brush's Falcon Works, Loughborough between 1962 and 1968, which made them the most numerous class of British...

). The majority were built at BR Derby although some came out of the Darlington works. The redesign principally affected two areas, the cab and the location of the air intakes. The gangway doors fitted to the earlier examples were rarely used, their presence adding to the complaints of noise and draughts in the cabs. The removal of the air filters from the side air louvers to the cantrail was the result of a comparison carried out at Inverness between a batch of Derby built Type 2s and a batch of BRCW
Birmingham Railway Carriage and Wagon Company
The Birmingham Railway Carriage and Wagon Company was a railway locomotive and carriage builder, founded in Birmingham, England and, for most of its existence, located at nearby Smethwick, with the factory was divided by the boundary between the two places...

 Type 2s (Class 26
British Rail Class 26
The British Rail Class 26 diesel locomotives, also known as the BRCW Type 2, were built by the Birmingham Railway Carriage & Wagon Company at Smethwick in 1958-59. Forty seven examples were built, and the last were withdrawn from service in 1993...

 and Class 27
British Rail Class 27
British Rail's Class 27 comprised 69 diesel locomotives built by the Birmingham Railway Carriage and Wagon Company during 1961 and 1962. They were a development of the earlier Class 26; both were originally classified as the BRCW Type 2.- Usage :...

), the tests targeting the air quality within the engine room. These tests revealed the location of the grilles on the Derby build allowed for much more debris to reach the filters (especially the lower ones), clogging them quicker, leading to poorer air quality within the engine compartment, and so potentially affecting performance and engine wear. With such a large order to be completed it was felt that a redesign of these areas would have a cost savings in the long run, in addition to a better working environment within the cabs, and with a general less cluttered look about the locomotive's exterior.

There were six variants of this sub-class, reflecting that locos were boilered and/or vacuum braked and/or dual braked. Boiler fitted locomotives included the first five (252 AV) and final thirty Class 25/2 (252 DV). Only members of the latter batch were modified for dual brake operation becoming 252 CX with the exception of 25242 that had had its boiler removed and was designated 252 FX. The non-boilered vacuum braked locos were 252 BV and when dual braked became 252 EX.

Class 25/3

Number sequence (original) D7598–D7677 (TOPS) 25 248–25 327


The final batch of locomotives were designated Class 25/3 and was to be built by BR Derby
Derby
Derby , is a city and unitary authority in the East Midlands region of England. It lies upon the banks of the River Derwent and is located in the south of the ceremonial county of Derbyshire. In the 2001 census, the population of the city was 233,700, whilst that of the Derby Urban Area was 229,407...

 and Beyer, Peacock and Company
Beyer, Peacock and Company
Beyer, Peacock and Company was an English railway Locomotive manufacturer with a factory in Gorton, Manchester. Founded by Charles Beyer and Richard Peacock, it traded from 1854 until 1966...

 of Manchester
Manchester
Manchester is a city and metropolitan borough in Greater Manchester, England. According to the Office for National Statistics, the 2010 mid-year population estimate for Manchester was 498,800. Manchester lies within one of the UK's largest metropolitan areas, the metropolitan county of Greater...

. However, because of financial problems Beyer, Peacock was unable to complete the final 18 locomotives and these were transferred to BR Derby for construction.

Though these locomotives still carried a RTB 15656 generator, this variant was a ten pole machine with a modified assembly incompatible with earlier equipment. The regulated (full hp) part of its characteristic was substantially the same as before but the unloading point, that is the point at which full power could no longer be utilised, was altered to 900 A, 910 V (819 kW) from 1,050 A, 780 V (819 kW). Only two stages of field weakening were employed, previous machines had six, and this provided ‘full power’ at speeds between 7 and 80 mi/h, and maximum tractive effort was reduced to 41500 lbf (184,601.2 N).

The latter half of the 1960s had seen the widespread introduction of solid state electronics and these locomotives incorporated a control system where speed was detected electronically rather than mechanically. A signal from a tachogenerator was used to close contactors in sequence at given speeds to activate the motor's field weakening process, rather than through contacts and relays as in earlier types. The control system ensured the traction motors and main generator were all operated within the continuous rating of the machines except in full field conditions when the driver was able to judge how long to remain in the short-term rating condition.
There were two variants of the Class 25/3 sub-class. Early 25/3 AV locomotives were fitted with vacuum brake
Vacuum brake
The vacuum brake is a braking system employed on trains and introduced in the mid-1860s. A variant, the automatic vacuum brake system, became almost universal in British train equipment and in those countries influenced by British practice. Vacuum brakes also enjoyed a brief period of adoption in...

s and in due course many of these were dual braked and redesignated 253 BX. By the time the last few locomotives were under construction dual braking had become the norm and ten of the last batch from Derby were built new as 25/3 BX locomotives for work out of Willesden
Willesden
Willesden is an area in North West London which forms part of the London Borough of Brent. It is situated 5 miles north west of Charing Cross...

 on the recently upgraded West Coast Main Line
West Coast Main Line
The West Coast Main Line is the busiest mixed-traffic railway route in Britain, being the country's most important rail backbone in terms of population served. Fast, long-distance inter-city passenger services are provided between London, the West Midlands, the North West, North Wales and the...

.

Class 25/9

At the end of 1985 twelve of the remaining Class 25/3 locomotives were designated as 25/9, the intention being that they would operate on traffic won for the Industrial Minerals Division of Railfreight
Railfreight Distribution
Railfreight Distribution was a subsector of British Rail created by the division in 1987 of British Rail's previous Railfreight sector. It was responsible for non-trainload freight operations, as well as Freightliner and Intermodal services. In its early years the division was occasionally...

 that included salt for road gritting from the ICI
Imperial Chemical Industries
Imperial Chemical Industries was a British chemical company, taken over by AkzoNobel, a Dutch conglomerate, one of the largest chemical producers in the world. In its heyday, ICI was the largest manufacturing company in the British Empire, and commonly regarded as a "bellwether of the British...

 mine at Winsford
Winsford
Winsford is a town and civil parish within the unitary authority of Cheshire West and Chester and the ceremonial county of Cheshire, England. It lies on the River Weaver south of Northwich and west of Middlewich, and grew around the salt mining industry after the river was canalised in the...

. The locos were selected from the available pool of Class 25 locomotives in March 1985 with the expectation of three more years of service before 10,000 running hours since last Works attention would be reached and their maintenance would be concentrated at Carlisle Kingmoor depot. At that point the expected cascade of motive power on BR as a whole would see them replaced by Class 31
British Rail Class 31
The British Rail Class 31 diesel locomotives, also known as the Brush Type 2 and originally as Class 30, were built by Brush Traction from 1957-62.- Description :...

 locomotives. However, the traffic they were designated for was not captured and in due course the sub-class were withdrawn along with the other members.

Train Heating Units

Three Class 25/3 locomotives were converted in 1983 for use as mobile generators to provide electric heating on trains where the hauling locomotive could not supply this. They were given departmental numbers 97250 / 97251 / 97252 (formally 25310 / 25305 / 25314). They were referred to as ETHEL units (Electric Train Heating Ex-Locomotives), and unofficially named Ethel 1, Ethel 2 and Ethel 3. They were painted in a blue/grey livery in an effort to match the coaching stock livery of the day, but this was not too successful. Ethel 1 was withdrawn in 1987, the other 2 in 1990. All 3 were scrapped in 1994.

Prototype

In 1962 Sulzer designed and began development of a prototype diesel engine for higher outputs based on the LDA range. Rated initially at 1700 hp at 850 rpm (with a development potential to 2000 bhp at 850 rpm) it was approximately the same overall size as the 6LDA28 and designated LDA28-R. BR was approached with the idea that one of the Derby Type 2s should be fitted with this engine but development work proceeded slowly and problems with the 12LDA28-C (used on the Class 47 locomotive) diverted resources. In the end development was terminated and the locomotive set aside for its use, D5299, was completed as a standard Class 25/2.

Preservation and current operation

Twenty Class 25s have survived in preservation, of all sub-types except Class 25/0.
Numbers carried
(Current in bold)
Name Location Current Status Livery
D5185 25035 Castell Dinas Brân
Castell Dinas Bran
Castell Dinas Brân is a medieval castle standing high on a hill above the town of Llangollen in Denbighshire, Wales. It is also the site of an Iron Age hill fort.-Early history:...

Great Central Railway
Great Central Railway (preserved)
The Great Central Railway is a heritage railway split into two adjacent sections, one in Leicestershire and the other Nottinghamshire.The Leicestershire section is currently Britain's only double track mainline heritage railway, with of working double track, period signalling, locomotives and...

Operational BR Green
D5207 25057 - North Norfolk Railway
North Norfolk Railway
The North Norfolk Railway – also known as the "Poppy Line" – is a heritage steam railway in Norfolk, England, running between the coastal town of Sheringham and Holt, It cuts through the countryside to the east of Weybourne with views of its windmill and passes through the well preserved country...

Operational BR Blue
D5209 25059 - Keighley and Worth Valley Railway
Keighley and Worth Valley Railway
The Keighley and Worth Valley Railway is a long branch line that served mills and villages in the Worth Valley and is now a heritage railway line in West Yorkshire, England. It runs from Keighley to Oxenhope. It connects to the national rail network line at Keighley railway station...

Operational BR Blue
D5217 25067 - Battlefield Line Railway
Battlefield Line Railway
The Battlefield Line Railway is a heritage railway in Leicestershire, England. It runs from Shackerstone to Shenton , via Market Bosworth, a total of...

Operational BR Green (Yellow Warning Panels)
D5222 25072 - Caledonian Railway
Caledonian Railway (Brechin)
The Caledonian Steam Railway Ltd is a private limited company formed by a group of steam railway enthusiasts, the Brechin Railway Preservation Society, with the object of operating a railway service on the former Caledonian Railway line between Brechin and Montrose, Angus, Scotland...

Awaiting Restoration BR Green (Full Yellow Ends)
D5233 25083 - Caledonian Railway
Caledonian Railway (Brechin)
The Caledonian Steam Railway Ltd is a private limited company formed by a group of steam railway enthusiasts, the Brechin Railway Preservation Society, with the object of operating a railway service on the former Caledonian Railway line between Brechin and Montrose, Angus, Scotland...

Awaiting Restoration BR Blue
D7523 25173 John F Kennedy Epping Ongar Railway
Epping Ongar Railway
The Epping Ongar Railway operates on a preserved railway along the final section of the old Great Eastern Railway and London Underground Central Line branch line between Epping and Ongar, with an intermediate station at North Weald...

Operational BR Two-Tone Green (Yellow Warning Panels)
D7535 25185 Mercury
Mercury (mythology)
Mercury was a messenger who wore winged sandals, and a god of trade, the son of Maia Maiestas and Jupiter in Roman mythology. His name is related to the Latin word merx , mercari , and merces...

Paignton and Dartmouth Steam Railway
Paignton and Dartmouth Steam Railway
The Paignton & Dartmouth Steam Railway is a heritage railway on the former Kingswear branch line between Paignton and Kingswear in Torbay, Devon, England....

Operational BR Two-Tone Green (Yellow Warning Panels)
D7541 25191 The Diana
Diana (mythology)
In Roman mythology, Diana was the goddess of the hunt and moon and birthing, being associated with wild animals and woodland, and having the power to talk to and control animals. She was equated with the Greek goddess Artemis, though she had an independent origin in Italy...

South Devon Railway
South Devon Railway Trust
The South Devon Railway Trust is a charitable organisation that operates a heritage railway from Totnes to Buckfastleigh in Devon, alongside the River Dart...

Awaiting restoration BR Green (Yellow Warning Panels)
D7585 25235 - Bo'ness and Kinneil Railway
Bo'ness and Kinneil Railway
The Bo’ness and Kinneil Railway is a Heritage railway in Falkirk, Scotland. It is operated by the Scottish Railway Preservation Society, and operates some 5 miles of track, virtually the entire Slamannan and Borrowstounness Railway that became part of the former North British Railway on the Firth...

Yard use (Awaiting wheelset overhaul) BR Blue
D7594 25244 - Kent and East Sussex Railway
Kent and East Sussex Railway
The Kent & East Sussex Railway refers to both an historical private railway company in Kent and Sussex in England, as well as a heritage railway currently running on part of the route of the historical company.-Historical Company:-Background:...

Awaiting restoration N/A
D7612 25262 - South Devon Railway
South Devon Railway Trust
The South Devon Railway Trust is a charitable organisation that operates a heritage railway from Totnes to Buckfastleigh in Devon, alongside the River Dart...

Operational BR Two-Tone Green (Yellow Warning Panels)
D7615 25265 Harlech Castle
Harlech Castle
Harlech Castle, located in Harlech, Gwynedd, Wales, is a concentric castle, constructed atop a cliff close to the Irish Sea. Architecturally, it is particularly notable for its massive gatehouse....

Great Central Railway
Great Central Railway (preserved)
The Great Central Railway is a heritage railway split into two adjacent sections, one in Leicestershire and the other Nottinghamshire.The Leicestershire section is currently Britain's only double track mainline heritage railway, with of working double track, period signalling, locomotives and...

Awaiting repairs BR Blue
D7628 25278 Sybilla North Yorkshire Moors Railway
North Yorkshire Moors Railway
The North Yorkshire Moors Railway is a heritage railway in North Yorkshire, England. First opened in 1836 as the Whitby and Pickering Railway, the railway was planned in 1831 by George Stephenson as a means of opening up trade routes inland from the then important seaport of Whitby. The line...

Operational BR Two-Tone Green (Yellow Warning Panels)
D7629 25279 - Great Central Railway Nottingham Operational BR Two-Tone Green (Yellow Warning Panels)
D7633 25283 - Dean Forest Railway
Dean Forest Railway
The Dean Forest Railway is a long heritage railway that runs between Lydney and Parkend in the Forest of Dean, Gloucestershire. The route was part of the Severn and Wye Railway which ran from Lydney to Cinderford. The society that operates the line started steam locomotive operations in 1971, and...

Operational BR Two-Tone Green (Yellow Warning Panels)
D7659 25309 - West Coast Railway Company
West Coast Railway Company
West Coast Railways, also known as West Coast Railway Company, is a railway spot-hire company and charter train operator, based at Carnforth in Lancashire, on the site of the old Steamtown heritage depot...

Undergoing overhaul BR Two-Tone Green (Yellow Warning Panels)
D7663 25313 - Wensleydale Railway
Wensleydale Railway
The Wensleydale Railway is a railway line in Wensleydale and Lower Swaledale in North Yorkshire, England and the name of the company that operates services on the line....

Undergoing overhaul BR Blue
D7671 25321 - Midland Railway - Butterley
Midland Railway - Butterley
The Midland Railway – Butterley is a heritage railway, formerly known until 2004 as the Midland Railway Centre, at Butterley, near Ripley in Derbyshire.-Overview:...

Operational BR Blue
D7672 25322 Tamworth Castle
Tamworth Castle
Tamworth Castle, a Grade I listed building, is a Norman castle, located next to the River Tame, in the town of Tamworth in Staffordshire, England....

Churnet Valley Railway
Churnet Valley Railway
The Churnet Valley Railway is a standard gauge heritage railway to the east of Stoke-on-Trent in Staffordshire. The CVR has two main operational headquarters - Cheddleton station, where the motive power department is based and where the first trains ran, and Kingsley and Froghall station, where...

Awaiting repairs BR Blue Variant

The class returned to the main line in October 2007 when D7628 (25278) worked from the North Yorkshire Moors Railway
North Yorkshire Moors Railway
The North Yorkshire Moors Railway is a heritage railway in North Yorkshire, England. First opened in 1836 as the Whitby and Pickering Railway, the railway was planned in 1831 by George Stephenson as a means of opening up trade routes inland from the then important seaport of Whitby. The line...

 to and from Whitby station
Whitby railway station
Whitby railway station serves the town of Whitby in North Yorkshire, England. It is the terminus of the Esk Valley Line, connecting with the North Yorkshire Moors Railway at Grosmont, and provides mainline running for NYMR trains during the summer months...

.

Literature

  • Rail Express Magazine, Issues 1 and 2, June/July 1996
  • Ian Allan ABC of British Railways Locomotives, summer 1966 edition

External links

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