Why the APT failed
In the late-1960s, BR began to plan for 100mph-plus high speed trains. In this extract from his latest book about the Advanced Passenger Train, DAVID CLOUGH reveals the thinking and politics behind the origins of both the APT and the more conventional HST
David Clough introduces his latest book, which reveals the politics behind the origin of the APT.
The origin of the Advanced Passenger Train (APT) can be traced to British Rail’s recruitment of Alan Wickens to carry out research into vehicle riding, initially with short-wheelbase freight wagons.
The work on vehicle dynamics also encompassed study of the interface between a steel rail and two flanged steel wheels joined by an axle. An experimental two-axle highspeed freight vehicle (HSFV-1) next provided a model for vehicle stability, and this ran satisfactorily on the test rig at 140mph.
Trials had established the speed at which a vehicle could traverse a curve of a specified radius without derailing, and this was at a much higher speed than was acceptable to passengers. This is because of the lateral acceleration (sideways motion) experienced by passengers during cornering, which imposes a lower limit on cornering speed than the risk of derailment. Limiting tilt to well below the angle at which overturning would occur would enable the vehicle to negotiate curves faster than without tilt, and also mitigate the effects of lateral acceleration felt by passengers.
Arising from this research, in 1966 Wickens proposed examining the potential for running passenger rolling stock at higher speeds. This was in line with BR’s desire for cutting intercity journey times, notably on the East Coast Main Line.
Realising that a single vehicle would not permit investigation into interface issues, the proposal was developed into the design of a complete train that would run at higher speeds on existing track, and whose cost would be within existing limits. Thus was born the experimental Advanced Passenger Train project - APT-E.
Objectives for the train were to include a 50% increase in maximum speed, a 40% increase in curving speed, to run on existing track with existing signalling, and to achieve a similar cost per seat-kilometre as existing trains. By the end of 1967, APT’s major
Objectives for the train were to include a 50% increase in maximum speed, a 40% increase in curving speed, to run on existing track with existing signalling, and to achieve a similar cost per seat-kilometre as existing trains.
concepts had been identified as follows:
A lightweight construction, with the weight per passenger to be about a quarter that of a conventional train.
A gas turbine power plant driving all axles of the power car through a mechanical transmission (or electric power units).
The braking system to be a combination of hydro-kinetic braking for high speeds and friction braking at low speeds, and incorporating plasma torch technology. Aerodynamic design. Estimated journey times between Euston and Glasgow were produced for a 14-car trainset making two intermediate stops. With 8,000hp available and running at up to 155mph, the non-tilt trainset would take 280 minutes, while the tilt version could shave this to 240 minutes. Limiting speed to 125mph and using only 4,000hp of tractive power, the journey times were extended to 285 and 255 minutes respectively.
In June 1968 Wickens presented a paper on APT to an international conference on high-speed railways, held in Vienna. At this event, Japanese Railways admitted its Tokaido Shinkansen line was experiencing heavy track wear, which was what BR’s specification for APT aimed to overcome by incorporating the Wickens research.
With first use on the East Coast Main Line in mind, gas turbine propulsion was envisaged. The APT was planned to have a maximum axle load of 11 tons, which would significantly benefit track maintenance costs. Although of eight coaches, because of its light gross weight it would need installed power of only 3,000hp, while its suspension would obtain stability at speeds up to 155mph on existing open track.
The aerospace industry techniques of stressed-skin aluminium construction to be used in APT’s bodywork would cut tare weight per passenger by about two-thirds, compared with a locomotive-hauled formation of six orthodox 64-seat coaches. An eight-car set with two power cars and six trailers was planned to seat 288 First Class or 384 Second Class passengers in equivalent seating space to that of prevailing BR Inter-City stock.
A most taxing item in the BR specification was that APT must negotiate main line curves without flange contact, to reduce both the vehicle and track maintenance costs of very high speed. This was to be obtained by the adoption of an articulated train, where the ends of adjoining vehicles shared a common bogie - this was to offer a significant reduction of lateral stresses on the track, and lessen the risks of derailment.
BR Research’s view was that neither friction nor disc brakes would meet the APT’s need for lightweight and low maintenance cost equipment, nor the stipulation that an APT must be capable of deceleration from 155mph to a stand within prevailing braking distances for orthodox BR 100mph trains. Consequently the designers opted for the first rail use of the hydrokinetic (or water) brake, supplemented by disc brakes in the low-speed range.
At the same 1968 Vienna conference, representatives from French and German Railways were relaxed about the funding of their own development programmes for high speed, the inference being that their governments would bankroll the work. As will now be seen, this was not so for BR.
At this stage it is important to appreciate that the 1962 Transport Act laid responsibility for railway research with what is today the Department for Transport (DFT), and also placed financial constraints by virtue of a commercial remit on BR. This situation was a deterrent towards long-term speculative research by BR, and was regarded as the responsibility of the Government, which also had responsibility for roads and air research. This can be seen in the government
funding of the supersonic Concorde plane project.
A change of emphasis came with the 1968 Transport Act, which imposed a duty on the BRB to promote research along lines settled from time to time by the Minister, who was empowered to provide financial assistance.
By the end of 1967, the Research Department had estimated the cost of the development of APT to the end of its prototype stage (put at five years) as £ 4.82 million. Despite government overtures, BR was “very doubtful” about the merits of spending so much money on a project that was not expected to realise a financial return for many years. Nevertheless, with the DFT willing to fund half the cost, in November 1968 the BR Board was asked to agree to pay for its share of the project - and duly agreed.
While BR’s ‘precarious’ financial position and the tough financial remit set by government were judged to be factors in BR’s reticence to agree to APT thinking, it was evident to the DFT that rivalry on the BRB between the Research Department and the Chief Mechanical & Electrical Engineer (CM & EE) was also a factor. Scientist Dr Richard Beeching, who might have been a strong patron, was long gone from the BR chair.
The project was to consist of three phases. The first was to take two years (1969-1971), and include the building of APT-POP (an unpowered developmental train) and the APT-E to be used in a programme of laboratory and track tests. Phase 2 was to be spread over the following three years, and comprise the construction and development of two prototype gas turbine APTs. Finally, Phase 3 was to run concurrently with the last two years of Phase 2 and involve the production of an electric APT.
On January 14 1969 the BRB authorised a research project that comprised several specific parts, such as suspension, transmission and power equipment. On May 1 the contract was let for the APT test facility within the Railway Technical Centre (RTC), and on July 4 Hawker Siddeley was awarded a contract to build the suspension.
The newly merged GEC-English Electric was given responsibility for the light alloy body structure, with the group’s part ownership of British Aircraft Corporation offering access to aircraft production expertise and aerodynamics. Government cancellation of the ‘TSR2’ fighter jet project had already made it
Despite government overtures, BR was “very doubtful” about the merits of spending so much money on a project that was not expected to realise a financial return for many years.
possible for BR to recruit engineers displaced from the aerospace sector, while the GEC-EE merger in 1968 had also aided BR’s recruitment drive for engineers.
Leyland Motors (British Leyland) was contracted for 12 gas turbines. The Leyland 2S/350/R had been developed for commercial road vehicles, and differed from aircraft-type gas turbines by being designed to reduce fuel consumption. It weighed roughly half that of a contemporary diesel engine of the same power.
By 1969 reports described the turbine as being fully developed and fully engineered, with a matched transmission and in limited production. Fuel consumption was said to be “remarkably low” and close to automotive diesel levels. A two-stage mechanical drive was judged suitable for speeds up to 100mph.
Meanwhile, a planning memo of December 16 1968, outlining the future workload for BR’s workshops, noted that no provision had been made for the manufacture of APT. This was despite final assembly of APT-E due to be undertaken at Derby, while part of the closed Melton Mowbray-Nottingham route was to be upgraded to provide a test facility for APT and other vehicles.
In July 1969 BR exhibited its designs for several future projects, and a full-size mock-up of an APT interior was on show. The APT concept had first been made public during a visit by the Minister of Transport on March 31 1967, when an ‘O’ Gauge model was displayed (this was also on display at the July 1969 exhibition).
As a result of a presentation made to the BR Chairman’s Conference held on February 21 1969, there was a perceived high priority for the designing of a high-speed diesel multiple unit (DMU) - either as an alternative to APT or as an intermediate stage before APT became available. At the time, the CM & EE was
considering options for new locomotives, including one of 4,500hp that would be capable of speeds up to 125mph.
Despite the views proposed at the Chairman’s Conference, on March 18 a meeting chaired by the CM & EE discussed a paper he had produced for the design of 125mph locomotives. Alternatives put forward were either an 80-ton Bo-Bo or 110-ton Co-Co, with Paxman’s Mk 3 ‘ Ventura’ diesel as one of the options.
The meeting judged that in the longer term it was expected that high-speed passenger services would be formed of APT sets. There was, however, a strong case for an alternative policy based on a conventional DMU, and the meeting felt there was no case for a high-speed passenger locomotive.
Also on March 18, H O Houchen (the BRB Member for BR’s workshops) wrote to the CM & EE to express his view that the latter should work up proposals for an alternative to APT - because if the decision in 1971 was that it was not viable, there would be an unacceptable delay in producing a conventional alternative.
Houchen felt that one of the Blue Pullman sets could be taken out of service and used as a developmental train. He judged that a decision could be made in 1970 on whether to convert the remaining five Blue Pullmans or to build more orthodox trainsets on that basis.
A week later, he sent a memo to the BR Deputy Chairman to give his views on future high-speed traction policy: “It is likely to be well into 1971 before a decision can be made as to whether the APT can go ahead to prototype in 1974 or later. By 1971 it will be too late to begin looking for an alternative.”
A paper prepared on June 30 by BR’s Chief Planning Manager, who was involved internationally with moves towards higher speeds, proposed an option to introduce a pre-APT intermediate multiple unit solution of 40 sets per year from 1974. APT was then expected to be brought into service at a rate of 20 sets per year from 1978.
Pressure within BR not to put all its future high-speed eggs into the APT basket also came from the Eastern Region (ER) General Manager, in a memo dated August 12 1969. With the potential for APT to be delayed or even never materialise, he was concerned about the loss of traffic to air and road between London and the North East without 125mph trainsets.
He added that there was no confirmation of the APT cost calculations and that this could affect the scale of its use, while his study of potential loss of revenue would largely cover preliminary design work on a more conventional multiple-unit solution by way of insurance. He concluded that there was an urgent need to achieve substantially reduced journey times for principal Inter-City services well before the introduction of the APT.
John Ratter, the BRB Member for engineering and technical matters, wrote to the Chairman on June 4 in response to the latter’s enquiry about the French TGS prototype gas turbine trainset.
Ratter expressed a worry about the lack of an intermediate form of traction until APT came on stream, and that he had discussed this with the CM & EE, who was one of his staff. He judged that a prototype high-speed DMU could be produced in three years and that the CM & EE had managed to recruit design engineers, primarily from the outwash from the GEC/EE merger.
The idea of an intermediate form of traction
History records that the APT project failed, but that Italy and Sweden pursued the concept of tilting trains for high speed, while the results now run in Britain in the form of the Class 390 Pendolinos and Class 221 Super Voyagers.
had actually been aired six months earlier, but no action had been taken. Ratter said he would take the matter forward through the Executive Committee, and then (if appropriate) to the Investment Committee.
The June 1969 issue of Modern Railways described SNCF’s developments with its TGS high-speed trainset, which by then had already run 100,000 miles at speeds of up to 150mph. The article argued that BR should have been at least at the same stage of development. BR’s chairman read this feature and wrote to John Ratter (copied also to Sydney Jones, the Board Member for research) saying: “Very interesting, but costs by our standards are very heavy.”
The Chairman wanted to know if BR had been apprised of SNCF’s prototype, and was told that it had been. Like BR, gas turbine propulsion had been selected. But unlike BR’s plans for APT-E, the French were using a traditional bogie and mechanical drive arrangement (the view in Derby was that this would be more costly overall than envisaged for APT). By now SNCF was already planning its first dedicated high-speed line, and so moving along a different development path to BR.
On November 7 the BR Deputy Chairman received further views concerning the prospects for APT. These said that while it might conceivably be possible to bring forward the introduction into commercial service of the APT at additional cost, this course did not commend itself because:
APT combined several different experiments in one project. Failure of any one would affect the others.
In the circumstances it was essential that the proving programme, both at prototype and service testing stage, should not be curtailed.
It would represent too great a concentration of capital and other resources on a single solution, which (even if successful) might not be applicable to all Inter-City services.
A meeting on November 7 agreed that BR’s long-standing policy of specifying mixed traffic motive power for both freight and passenger applications was no longer appropriate. Going forward, traction would be produced for each application and for running at up to 125mph, and a trainset with a lightweight power car at each end was the solution. This trainset was to become the HST and be the responsibility of the CM & EE, whose own preference for a 4,000hp locomotive for this purpose was abandoned.
Events between 1967 and 1969 reveal the divergent approaches to high-speed internationally, with the Derby Research Unit proposal differing from that of overseas railways.
Firstly, it appears to have been much more one of scientific application, rather than extending the use of traditional heavy rail vehicle progression.
Secondly, BR (unlike its international counterparts) was having to work within a tight financial straitjacket.
Thirdly, the traditionalists within BR, with no background in science, were concerned that APT might not materialise or be too costly for commercial service. In this respect, the huge sums poured into the development of the Concorde aircraft project by both the British and French Governments produced a plane that only each country’s flag carriers ever bought.
Finally, politics within BR were also to the fore, with the CM & EE seeing his timehonoured control of traction development sapping away. His department led the High Speed Passenger Services Steering Group, which had no involvement with APT, despite its title. All these factors were to prove a hindrance to the APT project.
History records that the APT project failed, but that Italy and Sweden pursued the concept of tilting trains for high speed, while the results now run in Britain in the form of the Class 390 Pendolinos and Class 221 Super Voyagers.
HSTs continue to be the mainstay of Great Western Railway’s inter-city motive power fleet, 40 years after being introduced, and remain important components of the fleets of other operators.
The HSTs did, of course, benefit from aspects of Alan Wickens’ research on the wheel-rail interface. And elements within the APT project found application within the design of Class 91 and the Mk 4 coaches built for the East Coast line in the 1980s.