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The Advanced Passenger Train (APT) was an experimental tilting high speed train developed by British Rail during the 1970s and early 1980s, for use on the West Coast Main Line, which contained a lot of curves. Notable among numerous technical advancements was the active tilting system, which the APT pioneered and has since appeared on other designs around the world. Other features of the APT such as the hydrokinetic braking, used to stop the train within existing separations, have not been adopted.〔http://www.apt-p.com/aptbrakesystem.htm〕 The experimental version APT-E achieved a new British railway speed record when on 10 August 1975 it hit 152.3 mph (245.1 km/h). The introduction into service of the Advanced Passenger Train was to be a three-stage project. Phase 1, the development of an experimental APT, the APT-E, was completed. Phase 2, the introduction of three prototype trains, known as the APT-P, into revenue service on the Glasgow-London route, enjoyed only limited service due to bad publicity. Phase 3, the introduction of the Squadron fleet designated APT-S, did not occur. The APT suffered from delays between the APT-E and APT-P, and then a lengthy series of in-service problems when the APT-P started testing. As these delays grew, the programme was dismissed as a white elephant and every minor problem was heavily covered in the press. It gathered a reputation that led to politicians wishing to distance themselves from the fray. Further funding for service entry became increasingly difficult to find, and the project eventually ground to a halt. ==Background== In the mid to late 20th century, British Rail express services compared unfavourably with France's TGV and Japan's Shinkansen. Experience with increasing the speed of passenger services had shown that reduced journey times could produce a significant increase in passenger numbers. The East Coast Main Line was largely straight and suited to high speeds, but other lines, specifically the West Coast Main Line (WCML) from London to Glasgow, were not straight enough to support high speeds with conventional equipment. Lateral forces would be just too high around curves; passengers would not be able to stand upright easily, and things would move on tables. Because slower trains also use the same tracks, superelevation (banking or "canting" of the track around curves) could only be utilized to enable speeds up to . In order to permit a top speed of , and thereby cut journey times, British Rail's engineers at the Derby Research Division developed an advanced active tilting technology, using hydraulic rams controlled by spirit level sensors to tilt the passenger cars into the curves so that no lateral forces would be felt. British Rail deliberately commissioned two young engineers with no experience in trains or railways to head the development of the project. One had worked in missiles and the other for the National Coal Board. They worked in isolation to the in-house British Rail engineering team. The reason for total outsiders to develop the trains was that they would have no preconceived rail engineering prejudices and would approach the problem with a fresh open mind. These fresh minds brought to trains methods and technology from other advanced fields. They brought science into British railways, an industry that from its paradigm shift in innovative technology in the Victorian times, had progressed at a slow pace since then in comparison to other countries. Not only was the train designed to tilt but it was also articulated and had hydrokinetic (water turbine) brakes. The latter feature is often overlooked but was in fact just as significant as the tilting concept, because it enabled the train to stop within the existing signal spacings. During extensive testing on the West Coast Main Line, the hydrokinetic brakes repeatedly achieved their predicted performance. The fault in the system was that the hydrokinetic braking forces fell away rapidly as speed fell below 25 mph. At that speed the system was designed to apply hydraulic pressure to conventional friction brakes on the axles of each bogie on the train. The train manufacturer produced these bogies in bulk long before the train vehicles were ready. Their friction brakes were tested independently with water before they were stored but the storage period was so long that the internal coating on the hydraulic cylinders corroded. When the trains were tested in service, this corrosion caused a loss of brake pressure on every axle. On test, this caused the train to take nearly as long to slow from 25 mph to a standstill as it did to slow from 125 mph to 25 mph. During commissioning, because of this and other development issues, every axle on the trains was modified and exchanged. The shortcomings of using engineers with no experience of trains was exposed when the APT-P began commissioning tests. The stainless steel welds cracked on the hoses carrying fluid to the hydrokinetic brakes on the axles. Although this was rapidly solved, the air systems on the trains were not designed to deal with the water that compressed air contains. On conventional trains, vehicles were designed such that air pipes sloped towards drain valves and compressor air receivers were fitted with automatic drain valves. This reduced the water in the system and ensured that it was not trapped in pipework or critical equipment. On the APT-P, air pipe runs were tortuous, accidentally designing in multiple trap points for water. The results were first experienced during freezing conditions during West Coast Main Line commissioning, operating from Shields Depot, Glasgow. Air-powered door opening equipment froze and it was clear that the air controls on the hydrokinetic braking system would be compromised. Although the commissioning team engineers sought and found a Westinghouse designed solution that would eliminate the water being produced by the compressors, the design team would not accept the solution, stating that the problem would not occur with a full train formation, as opposed to the shorter formation used in commissioning. The seed was sown for the disastrous demonstration run from Glasgow, bearing national journalists, when the train failed shortly after leaving Glasgow due to a frozen brake system. The project never recovered. It was only discovered at the APT-P commissioning stage that parts of the West Coast Main Line had been built in such a way that, if two APT-P trains with their tilt systems failed and the carriages stuck in the inward tilted position met, they would strike one another. The civil engineers had built the railway with dynamic envelopes too small for the APT. The effect was not seen with conventional trains since, without tilt, their movements stayed well within the dynamic envelope. Some of the senior managers in British Rail at the time were unwilling to commit to a single project, and so initiated a parallel project to design a train based on conventional technology as a stopgap. This was the High Speed Train (HST), which was also marketed under the InterCity 125 name. The same senior managers withheld experienced engineering resources from the APT project, using them instead to press ahead as swiftly as possible with what they saw as a conventional rival to APT. The HST was a successful design, and is still in use 40 years later. In 1972, the APT-E, a gas turbine-powered experimental testbed, was constructed. This was only four cars in length; two power cars, one at each end and two 'passenger' cars full of instrumentation. The experimental train APT-E having proved the concept, British Rail moved to build three prototype Class 370 APT-P trains. Gas turbines had been chosen for their light weight compared to diesel engines but Leyland had ceased production and development and no other was suitable. Thus the new APT-P and APT-S trains were to be electrically powered and so restricted to electrified track. The hydrokinetic brake system was successful and reliable on the APT-E but for the APT-P design, it was decided to abandon the oil-filled hydraulic system and design an all-new system filled with water glycol solution, to reduce costs. The exhaustion of the corrosion inhibitor in the static hydraulic lines of parts of the water glycol system was to cause multiple problems with the brakes during commissioning. The APT-P trains were designed as two half-trains with twin power cars in the middle, sharing one pantograph. There was a passage through the power cars but it was noisy, cramped and not permitted for passengers. Therefore, each end of the train had to duplicate facilities. There were a number of reasons for this design compromise. Two power cars were necessary to maintain the design speeds over the northern banks with 12 coaches. Normally these would be situated at the front and rear of the train (as with the HST and TGV etc.) but, due to the design of the overhead line, a "wave" was set up in it by the front pantograph, thus causing problems for current collection from the rear unit. The obvious answer was an on-board 25 kV "roof-line" link to the rear power car but this was considered infeasible at the time. The final option was to put both power cars at one end of the train but, at the high speeds (and with the tilt feature), concerns were raised over excessive buckling forces when the train was being propelled. The eventual decision to use two non-articulated power cars in the centre of the train allowed one pantograph to be used with a 25 kV link between the two power cars. Both power cars were equipped with pantographs, with one lowered in service. Power was supplied through ASEA thyristor equipment, supplying four 1 MW DC traction motors mounted in each power car. The traction motors transmitted their power through internal gearboxes, cardan shafts and quill final drives, minimising the unsprung weight on the axles. Although all auxiliary equipment such as lighting, air conditioning and air compressors was powered by motor alternators, from the 25 kV overhead line, it was recognised that if there were to be an overhead line failure conditions in the passenger vehicles would quickly become unsafe and unbearable. Each driving van trailer i.e. the leading and trailing vehicles, was equipped with a diesel-alternator generator capable of supplying the minimum requirement of auxiliary power. The diesel-alternators were started using air motors powered from the train's air system, since the APT carried few batteries. The APT was designed for faster running than existing trains, and over the same track. The higher speed limits were provided to the driver by way of a transponder-based cab display called "C-APT". A radio beam from the train caused a track-mounted transponder to return the current line speed for an APT, which would then be displayed in a cab instrument. These sealed, unpowered transponders were placed at intervals of no more than 1 km. Approaching speed restrictions were provided at the appropriate distance, along with an audible alert; failure to acknowledge these alerts would result in an automatic brake application. C-APT was driven by a redundant onboard computer system using Intel 4004 microprocessors. The track units were essentially the same as the modern French Balise beacons. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Advanced Passenger Train」の詳細全文を読む スポンサード リンク
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