|Type and origin|
|Builder||BREL Crewe Works|
|Gauge||1,435 mm (4 ft 8 1⁄2 in) standard gauge|
|Wheel diameter||3 ft 4 in (1.016 m)|
|Length||17.79 metres (58.4 ft)|
|Width||2.74 metres (9.0 ft)|
|Locomotive weight||70.25 tonnes (69.14 long tons; 77.44 short tons)|
|Fuel capacity||990 imp gal (4,500 l; 1,190 US gal)|
|Prime mover||Paxman 12VP185 or MTU 16V4000 R41R
Originally Paxman Valenta 12RP200L
|Alternator||VP185: Brush Traction BA1001B
MTU: Brush Traction BA1001C
|Traction motors||GEC G417AZ (43124-43152)
Brush Traction TMH68-46
Both frame mounted, four off.
|Transmission||Engine driven alternator and rectifier supplying DC to traction motors|
|Multiple working||Within class only|
|Maximum speed||in service: 125 mph (201 km/h)
Record: 148 mph (238 km/h)
|Power output||Engine: 2,250 hp (1,678 kW)
At rail: 1,320 kW (1,770 bhp)
|Tractive effort||Maximum: 17,980 lbf (80.0 kN)
Continuous: 10,340 lbf (46.0 kN) @64.5 mph (104 km/h) 
|Train heating||Electric Train Heat|
|35 long tons-force (349 kN)|
East Midlands Trains
Virgin Trains East Coast
Great Western Railway
National Express East Coast
|Axle load class||Route availability 5|
The class is the fastest diesel locomotive in the world, with an absolute maximum speed of 148 mph (238 km/h), and a regular service speed of 125 mph (201 km/h). There are claims that this diesel rail speed record has been broken twice unofficially: by the TEP80 Russian train in 1993 achieving 271 km/h (168 mph), and the Talgo XXI Spanish train reporting 158 mph (254 km/h) in 2002.
In the early 1970s the British Railways Board (BRB) made the decision to replace its main-line express diesel traction. Financial limitations were tight, so mass electrification was not possible. As a result, a new generation of high-speed diesel trains had to be developed.
Experience with the high-speed Class 55 Deltic locomotives had shown that a low axle weight was essential to avoid damage to the track at sustained high speed, and that high-speed engines were the only way to provide a good enough power/weight ratio for diesels. To power the HST at up to 125 mph (201 km/h), each power car had a new diesel engine, the 12-cylinder Paxman Valenta, running at 1,500 rpm and developing 2,250 bhp (1,680 kW). The 70-tonne weight of the power car gave it a 17.5-tonne axle loading.
The prototype set was developed at the Railway Technical Centre, Derby, the power cars having been constructed by BREL Crewe Works and the British Rail Mark 3 passenger cars by BREL at Derby Litchurch Lane Works. The engine used in the prototype power cars was the Paxman 'Valenta' 12RP200L, which developed 2,250 horsepower (1,680 kW). The electrical equipment was supplied by Brush. The power cars had a main driver's position at one aerodynamically shaped end with the other flat and gangwayed end having only an auxiliary driving position for shunting purposes.
The two prototype power cars emerged from the works in June and August 1972 and were initially numbered 41001 and 41002, but after a short period the entire set, including the passenger coaches, became reclassified as a diesel-electric multiple unit: British Rail Class 252. The power cars were given the coaching stock numbers 43000 and 43001. After proving trials on the Eastern Region the prototype High Speed Diesel Train (HSDT) was transferred to the Western Region, where it was deployed on Paddington Bristol/Weston-super-Mare services.
The design was successful and led to production orders being placed for similar trains for the Western, Eastern, Scottish and London Midland Regions. The production power cars featured a redesigned front end without conventional buffers, although a rigid drawbar can be used to connect an HST to an ordinary locomotive. Following the introduction of production HST sets, the prototype unit was withdrawn, the power cars passing to the Research Division at Derby. Of the ten prototype coaches, two were adapted for use in the Royal Train, five were modified for use with the production HSTs, and three were transferred to Departmental stock.
The 197 power cars produced are numbered 43002-43198. 43001 was applied to the second of the two prototype power cars, while the first of the pair (now preserved at York) became 43000, which is unusual because BR TOPS classification numbered its locomotives from 001 upwards (this was because it was not, at the time, classified as a locomotive).
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In 1987, as electrification of the East Coast Main Line was under way, British Rail realised that the new Mk4 carriages for the Class 89 and 91 locomotives were not going to be finished in time for the introduction of electric services on the East Coast Main Line so, in late 1987, a total of eight Eastern Region power cars (Numbers 43013/014/065/067/068/080/084/123) conversions (on 43014/123) were carried out at the Derby Engineering Development Unit, whilst the other six (43013/065/067/068/080/084) were converted by the diesel repair shop at Stratford to have the lower valancing removed and buffers fitted.
After being fitted with buffers, these power cars began work as surrogate DVTs to work with the Class 91s and 89. The locomotives, working with conventional Mk3 stock, worked on the line between 1987 and 1991, when the last Class 91 locomotives entered service. As well as buffers being fitted to these powercars, special remote control equipment was also added to the locomotives so they could be controlled by the locomotive at the front. Once these locomotives left DVT duties, the remote equipment was removed.
After privatisation, these power cars joined the Virgin Trains fleet working both Virgin Cross-Country and Virgin West Coast routes, where they displaced loco-hauled stock. All the units were repainted from their original Intercity colours to the Virgin Red livery. Later, Virgin Trains gave up the HSTs when new Virgin Voyager units were delivered, and nearly all of these power cars went into storage at Long Marston yard.
After years of storage, several of the powercars were bought by Midland Mainline to be part of 'Project Rio', special services running from St Pancras Station to Manchester while major engineering works were undertaken on the West Coast Main Line. These units were kept in the de-branded Virgin Trains livery throughout their time with Midland Mainline and put back in storage once Project Rio had finished in 2006.
43013 and 43014 joined Network Rail's New Measurement Train in 2003 and have continued to work with this service ever since. Both of these units have now had MTU engines fitted.
43080 was leased to GNER as a one-off powercar, working as a spare unit that could be easily called for if a HST failed. For most of its time with GNER, it was based at Craigentinny yard in Edinburgh and was painted into GNER colours. This locomotive's lease ended in 2006 and it was returned to storage at Long Marston.
In 2007, the Train Operating Company Grand Central Trains took an interest in the stored powercars and amalgamated them into their fleet of three HST sets. In total, 43065/067/068/080/084/123 were bought by the company and now run high speed services between Sunderland and London Kings Cross. HSTs 43084 and 43123 were the final operational Paxman Valenta power cars, being re-engined in 2010 with the MTU treatment. While at the works being re-engined, Grand Central added the orange stripe that appears on their Class 180 units, re-painted the front ends (this making them look more like the non-buffered HSTs), and re-numbered the power cars into the four-hundreds. These are the current numbers: 43465 (065)/467 (067)/468 (068)/480 (080)/484 (084)/423 (123). The re-numbering of 43123 was confusing to some enthusiasts, as they sometimes believed it was originally 43023 because 400 was added to the numbers of the other power cars, yet only 300 to this particular power car.
British Rail experimented with Mirrlees Blackstone MB190 engines in four Western region examples (43167–43170) between 1987 and 1996, but this experiment was unsuccessful and the standard Paxman Valenta engines re-installed. These four locomotives have since all been re-engined with the MTU 16V4000 engine. 43167 is now 43367 and operates with Virgin Trains East Coast, whilst 43168-43170 are still in service, in the former Western region area under First Great Western.
Paxman began development of the Valenta's successor, the VP185, in 1987. The suggestion that British Rail participate in a trial of the new VP185 engine in the IC125 was first mooted in January 1991, and a formal agreement for the trial was signed in May 1993.
A qualifying requirement for the trial was that the engine should undergo a British Rail Type Test which was carried out between December 1993 and February 1994. The test involved completion of 3,000 cycles, each of 10 minutes duration, with four minutes at the maximum power of 2,611 kW (3,501 bhp) and six minutes at idle, simulating the typical 'on-off' nature of IC125 duty. The test was much more severe than operational duty, where the train operates at a maximum of 1,678 kW (2,250 bhp). The successful results of the test cleared the way for installation of a VP185 in Power Car 43170 at Plymouth Laira Depot for in-service trials in the summer of 1994. Power car 43170 entered service on 22 September 1994. 43170 was given the nameplate "Edward Paxman".[clarification needed]
During the late 1990s twenty-five HST power cars were re-engined with Paxman 12VP185L engines in order to improve fuel consumption and reduce emissions, but these engines have proved less reliable in service than hoped. However, the 12VP185L was introduced fleet-wide within the Australian XPT series.
The very last VP185 engine to be manufactured at Paxman's Colchester Works was despatched from the factory on 15 September 2003 for duty with Midland Mainline. When it comes into service Midland Mainline will be operating eighteen power cars re-engined with the 12VP185, with a rating of 1,678 kW at 1,500 rpm. Midland Mainline saw a programme completed in 2004 to convert 14 power cars to VP185 engines to supplement the four already converted during 1994/95, and this led to 43043/045/048-050/052/055/060/061/072/073/076/082 joining 43047/059/074/075 with this engine type.
Today there is not one production power car remaining that is still fitted with a Paxman Valenta engine, although the 125 Group's Project Miller have reinstalled a Paxman Valenta in the surviving prototype powercar, 41001 (formerly 43000).
In 2007 Brush Traction and Hitachi, Ltd equipped Paxman-Valenta-powered 43089 and a semi-permanently coupled Mark 3 coach with a diesel-battery hybrid power system for experimental trials. The power car was named "Hayabusa" (Hayabusa, はやぶさ, Japanese for Peregrine falcon, project name 'V-Train 2'). It has since been returned to normal service with East Midlands Trains.
The HST, having been in operation since the late 1970s, is due for replacement by the Hitachi Super Express. The development cycle for the replacement series is such that the existing fleet may be required to operate through to 2019 or beyond.
In May 2011 the National Railway Museum (NRM) announced that the remaining HST prototype power car 41001 would undergo full restoration work. A long-term loan was agreed between the NRM and the 125 Group of volunteers for the locomotive and a Paxman Valenta RP200L engine. The replacement engine (no. S508) was required as the original Valenta engine (no. S183) had been sectioned for display purposes. The S508 engine was lifted into the locomotive at Neville Hill depot on 29 June 2012.
When Crewe Works built them, the InterCity 125 units were considered to be diesel multiple units, and were allocated Classes 253 and 254 for Western and Eastern Region services respectively. The locomotives were introduced in the Midland region later.
Until the HST's introduction, the maximum speed of British trains was limited to 100 mph (160 km/h). The increased speed and rapid acceleration and deceleration of the HST made it ideal for passenger use, and it slashed journey times around the country. The prototype InterCity 125 (power cars 43000 and 43001) set the world record for diesel traction at 143 mph (230 km/h) on 12 June 1973. An HST also holds the world speed record for a diesel train carrying passengers. On 27 September 1985, a special press run for the launch of a new Tees-Tyne Pullman service from Newcastle to London King's Cross, formed of a shortened 2+5 set, briefly touched 144 mph (232 km/h) north of York.
During 1987, eight HST power cars were converted for use as driving van trailers (DVTs) with Class 91 locomotives during trials on the East Coast Main Line. The power cars were fitted with buffers and Time Division Multiplex equipment that allowed them to directly control a Class 91, and were moved over to the ECML where they were used on workings with Class 89 and then Class 91 locomotives from London to Leeds. After the Mk 4 stock had been delivered, the HST power cars had the TDM equipment removed, and then reverted to their normal duties. The power cars used for this project can be easily identified as they are still fitted with buffers. They were then transferred to Virgin Cross Country, and put in storage when Virgin replaced its HST fleet with Bombardier's Voyager (though Arriva, upon later taking over the franchise, acquired 10 power cars, 4 of which were buffered). Grand Central bought six of these for services from Sunderland to London, the remaining two having been integrated into Network Rail's New Measurement Train.
After the privatisation of British Rail the HST sets continued to be used. 194 of the 197 locomotives built remain in service, the most at any one point in history.
|CrossCountry||10||All Class 43/2 with MTU engines.|
|Virgin Trains East Coast||32||All Class 43/2 with MTU engines.|
|East Midlands Trains||24||All Class 43/0 with Paxman VP185 engines.|
|Great Western Railway||119||All Class 43/0 with MTU engines and Automatic Train Protection.|
|Grand Central Railway||6||All buffered from previous use as surrogate DVTs. MTU engines.|
|Network Rail||3||New Measurement Train. Pool consists of 43013, 014, 062. All are in "Flying Banana" Network Rail livery, fitted with external video cameras and MTU engines. 013 and 014 buffered from previous use as surrogate DVTs.|
|Scrapped||4 (1 prototype, 3 production)||
|Preserved||1 (prototype)||43000 (formerly 41001) - currently located at the National Railway Museum in York, and may be united with a production Mk3 set and locomotive in the future.|
Built between 1975 and 1982, the fleet is now in its fourth decade, and a replacement for the High Speed Train is being sought. This project, the Intercity Express Programme (originally known as the HST2), is being spearheaded by the Department for Transport. A consortium headed by Hitachi will design and build the replacement Hitachi Super Express Train. Various formations are to be built, an electric version and a bi-mode diesel-electric in 5 or 9 carriage lengths. The initial batches will replace HSTs on the Great Western Main Line and East Coast Main Line Main Lines.
On the Greater Western franchise, the current fleet of HSTs is expected to remain in service until 2017, the scheduled date for introduction of the Intercity Express. Between 12 and 20 HST sets were to be retained and refurbished to carry on providing services between London and Devon and Cornwall, where no electrification is currently planned, and where the Class 800's engines would not be capable of negotiating the steep gradients along the South Devon Banks, through to the mid-2020s. A 2011 report concluded that the Mark 3 coaches could remain in service as late as 2035 with some minor rewiring and enhancements required under disability legislation. However, it was announced in March 2015 that, subject to approval and contract, the HSTs will now be replaced with a more powerful derivative of the bi-mode Class 800s.
To a lesser extent, high-speed DMUs from the Bombardier Voyager family as well as Alstom's Class 180 (Adelante) have replaced numerous HSTs, but all locomotives and sets have been bought back into service as a result of increasing demand. Some will be cascaded to Abellio ScotRail to replace the Class 170 units on InterCity services in the region.
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