British Rail APT-E & APT-P

The British Rail Advanced Passenger Trains were two experimental train sets that utilized tilting technology, allowing the trains to navigate tight turns at high speeds. Four sets were built, the gas-turbine powered APT-E, and three of the electric powered APT-P.

With the imminent success of Japan’s “Shinkansen” service beginning in 1964, the rest of the world took notice and began implementing their own rendition of high speed services. France began experimenting with its “Aerotrain”, which preceded the TGV, while the United States began testing their high speed “Metroliner” train-sets. These advancements led British Rail to develop a high speed train of their own.

Background

With the genesis of air travel and the personal automobile in the mid-20th century, trains were becoming an antiquated mode of transport. British Rail still utilized steam locomotives on many of their services, while other modes of transport were modern and attracting the interest of the public. Due to the diminishing ridership on the nation’s railways, BR chairman Richard Beeching abandoned thousands of miles of railway throughout the country. These cuts in services, known as the “Beeching Axe”, significantly restructured the British railway system.

In order for the railway to compete with alternate modes of transportation, management began a painstaking study of the dynamics of railway wheels and adhesion. Throughout this period, derailments were common and research began at BR to investigate the effects of “bogey hunting”, which caused wheels on wagons and carriages to hunt for a middle spot on the rail, causing an eventual derailment.

BR eventually developed a freight car, HSFV-1, which was capable of high speed operation, rectifying the issue of bogey hunting. BR realized that similar technology could be allocated to passenger trains, utilizing BR’s single axle suspension system which significantly reduced drag during high speed running. This research commenced the beginning of the APT project with the request for an experimental passenger train.

The project was spearheaded by a report prepared by the Passenger Business division of BR, which stated that speed of the trains would determine if the railway could compete with other modes of transport. The report noted the introduction of the Class 55 locomotives to the ECML, and the electrification of the West Coast Mainline (WCML), in which ridership slowly increased. Thus, with the introduction of a high speed train, ridership was thought to skyrocket.

In the early 1970s, British Rail began culminating the idea of high speed train service, however, with most of the infrastructure being built in the 19th century, it was not feasible to operate trains at higher speeds without reconstructing the entire network. Upon realizing the limitations of the nation’s infrastructure, dynamics expert Alan Wickens formed the Derby Research Division, which began the development of the first experimental train set, the APT-E.

The research division at BR had two options, super-elevate the curves throughout the railways system, or curate a train that would tilt into corners similar to the Spanish Talgo sets. It was decided that similar to the Talgos, hydraulic cylinders would operate the tilting mechanism, therefore, reducing the centrifugal forces at play.

APT-E

The Advanced Passenger Train Experimental (APT-E), was a gas turbine experimental passenger set, able to travel at speeds of up to 156 mph. Although the train was designed for experimental purposes, and not intended for passenger service, its tilting technology would be implemented in various future trains.

The APT-E consisted of two power cars on either end, PC1 & PC2, and two trailer cars in between, TC1 & TC2. Each power car was fitted with four Rover-Leyland 2S/350 gas turbines, originally designed for roadway use. Each turbine was rated for 330 hp, which sent power to two GEC 253AY nose suspended traction motors, located on the leading bogey on each power car.

In addition to the original set, an addition a few non-powered carriages were constructed to test the braking and tilt systems, and were called the APT-POP sets, denoting Power-0-Power. The two dummy cars were denoted PC3 & PC4. The POP set was hauled by a conventional locomotive, and sent testing results to Derby while engineering the APT-E.

Much to the chagrin of British Rail, upon the set’s first run between Derby and Duffield in 1972, drivers became suspicious of BR’s efforts to utilize one crew member in the cab of the APT-E, and were concerned this would serve as the protocol for future operations. This resulted in a system-wide strike which lasted an entire day, costing the railway a substantial amount of money. Thus, the APT-E was taken from service for twelve months, and reintroduced in 1973. Throughout its time removed from service, BR continued negotiations with the various driver’s unions.

During its twelve month absence, the APT-E underwent various modifications, including replacing the bogies on PC1&2 with similar bogies as the power cars, with the exception of traction motors. Furthermore, the turbines were modified, and a passenger area was added to one of the trailer cars.

Once released from Derby, the set was extensively tested throughout the system before once again being shopped at Derby for additional modifications. The set was proving unreliable, thus, the turbines were replaced with upgraded models with 30 additional horsepower. Furthermore, every turbine powered the traction motors, rather than some being allocated to powering electricity to the passenger cars.

Upon reintroduction into service in 1974, the set recorded a new British railway speed record of 152.3 mph on the Great Western Mainline on the segment between Swindon and Reading. Throughout its furlong on the BR network, the train-set also spent a considerable amount of time on the London Midland region of the network, and could oftentimes be seen at the Old Dalby Test Track, where it reached a top speed of 143.6 mph.

Upon the conclusion of successful testing throughout the system, in 1976, the set was gifted to the National Railway Museum in York, where today it is preserved and maintained for the enjoyment of future generations.

APT-E Technical

APT-P-Ahead Of Its Time

While BR was engineering the APT-E, researchers and engineers at BR began working on the production run of the APT, which was to operate via 25 Hz current from overhead power lines. The utilization of electricity rather than turbine power is due to Leyland exiting the turbine market, as they had reached the decision to terminate their project involving turbine powered trucks. Furthermore, the oil crisis of 1973 would cause gasoline prices to skyrocket, thus, the APT project would not be economically feasible, especially at the rate that the turbines consumed fuel.

Thus, with the WCML previously electrified, BR decided to produce the prototypes. The design of the APT-P is distinctive to any other train to operate over British metals, as the two power cars were placed in the middle of the consist. This decision was made due to the condition of the overhead wires on the route, as they had trouble handling speeds over 120 mph, and were prone to kinking, especially when a train passed with two pantographs raised on each end of the train. Furthermore, an electrical connection on the roof provided power to both power cars, as only the rear-most power car had its pantograph raised when in operation.

The bogies on the two power cars were significantly different than those on the rest of the train, as they were not articulated. This decision was made due to the shortcomings of the APT-E’s articulated driving wheels. Furthermore, for weight reduction purposes, the traction motors were located inside the carbody, as opposed to inside the bogey frame. Power was given to the wheels by a series of gears, shafts, and drives.

APT-P Technical

Although this unique design solved the issues regarding the overhead lines, it hindered the experience of the passengers, as there was a tiny passageway through the power cars, however, it was not opened for the public. Therefore, the train was separated into two sections, each with their own accommodations such as dining cars. Furthermore, due to the mid-train power-cars, the sets were oftentimes longer than the station platforms permitted, thus, the entire length of the platform could not be utilized.

Because of the high speed capabilities of the APT compared to a conventional train, drivers had trouble slowing for speed restrictions and other speed limit changes, as the trackside signage proved inadequate. Therefore, a system called “C-APT” was implemented, which acted similar to the Automatic Warning System (AWS). Track mounted transponders utilized RFID technology to report the speed limit to the driver, if they failed to respond, a braking application would commence.

The train entering testing in 1979 after numerous delays, and almost immediately set a new UK speed record of 162.2 mph, only to be broken by a Class 373 Eurostar operating on HS1 in the early 1990s. Three APT-P sets were ultimately produced; they underwent testing and oftentimes operated scheduled passenger service in order to expose the technologically advanced nature of the train to the general public.

However, various shortcomings were experienced during testing, as various brake issues arose. These issues are blamed on the long term storage of the braking system prior to assembly, thus, the system began to corrode, severely hindering the train’s stopping power. Furthermore, the compressed air system was faulty, further hindering the ability of the brakes and other aspects of operation.

Infrastructural issues further plagued the project, as the APT team discovered during the testing phase that if two APT trains passed through a curve simultaneously, they would collide with each other due to the tiling mechanism. These issues, in addition to reorganization amongst British Rail departments, further hindered the train’s performance.

Throughout the project, the train was harshly criticized by the media, as they often highlighted the various breakdowns and delays. Furthermore, passengers reportedly fell ill due to the rough ride of the tilting mechanism. The trains were pulled from service in 1981 and underwent a series of upgrades regarding the tilt and braking systems. During this time, BR was producing the legendary High Speed Train (HST), utilizing convention diesel power. The HST was seen as more practical than the APT, as it harnessed the flexibility to operate throughout nearly every route on the BR system. The project was a great success, and support for the APT project dwindled.

The trains were returned to service in 1984 and performed adequately with minimal issues. However, due to BR’s stark interest in the HST, supporters of the APT fell by the wayside, and the production version, the Advanced Passenger Train-Squadron (APT-S), was dismissed. The trains were officially pulled from service in 1986, bringing an end to the tumultuous project.

Although the APT project never came to fruition, the engineers at BR developed a tilting system that would be utilized on trains throughout the world. Furthermore, various APT technologies were implemented on further trains utilized throughout the system, including the Intercity 225 project, which included the Class 91 locomotive that was fitted with the carbody mounted traction motors similar to the APT. During the APT project, the patents to the tilt system were sold to Fiat Ferroviaria, which later merged with Alstom in 2000. This led to the return of the tilting system to the UK in the form of the Alstom-built Class 390 “Pendolino” trainsets, which were operated by Virgin Trains (now Avanti West Coast) on the WCML.

Although the APT project had a tumultuous existence, and constantly found itself in negative press, the project was not a failure. The tilting system developed during the project was later utilized on the Pendolino trains, which allow them to keep a similar schedule to the APT-P, albeit, the system is now matured and operates reliably. Upon retirement, two of the three APT-P’s produced were scrapped, with one set being preserved at Crewe Heritage Center.

Provided below are photos of the integral components of the APT-P taken while the train-sets were being overhauled in 1981, prior to their second furlong in service beginning in 1984. Photos provided with the kind permission of Frank Struben.