Published: 30th November 2016
Forty years ago, the Intercity 125, the 125mph diesel powered High Speed Train (HST) entered scheduled service on the Great Western Main Line (GWML). But also at this time, the Advanced Passenger Train – Experimental (APT-E) was nearing the end of its short life.
The HST has become universally known and many say that it is the best train ever designed and built in the UK. It is likely to remain in service for another decade anywhere between Cornwall and Scotland providing a link with two 250mph trains half a century apart.
The end of steam came in August 1968 and it was only a few hundred days after this that British Railways began a project to design and build the train of the future – which has still not arrived today. The train was known as the Advanced Passenger Train -Experimental and just three years after the last steam locomotives were withdrawn, BR announced that in theory, the train could reach over 250mph in service.
Initially the train was due to be tested at up to 125mph on existing track (as with HSTs) and then using the experience gained testing this developing technology, it was anticipated to run at speeds over 250mph on newly built lines. The APT was to be introduced in 1974 or 1975 BR forecast and testing of the bogies/wheelsets commenced in 1971.
Of course today, there is much talk about HS2 and the legal powers are likely to be granted in the next month to enable the start of construction. And it is a matter for public debate whether trains will operate at 200mph but the track may well be laid to allow 250mph trains to run in time to come. It will therefore be half a century on from the BR 250mph design concept.
The design was being carried out in 1971 and initially models were made and press photographs released as the project gathered momentum. The train had a pair of driving power cars and two (non-powered) trailer cars. The power cars contained four 300 HP (later uprated to 330HP) Leyland 350 gas turbines plus a fifth used to provide power for train auxiliary power supplies. The power generated was fed into two GEC 253AY traction motors hung below the ‘nose’ on the leading bogies. Each vehicle was around 70feet long with an articulated bogie between each carriage.
The train was the active-tilt train in the world and the first to use computerised design for the wheelsets linked to the tilt mechanism and the lineside signalling. Today, Pendolinos use this system with trackside balises informing the train’s computer where it is and when to tilt to enable it to travel round curves at higher speed than ordinary trains. This so-called active suspension gives a smoother ride at high speeds.
Testing included a diesel pulling up to three ‘skeleton’ carriages to test two powered bogies either side of a non-powered bogie. This train tested the tilt, bogies, braking and suspension systems used on the train and these were scrapped after the project ended.
The train’s inaugural run was made between Derby a few miles north to Duffield on 25 July 1972 but ASLEF, the drivers’ union immediately ‘blacked’ the train because there was only provision made for one driver in the cab at a time when there was unrest due to BR wanting to introduce HSTs with one driver. Because of this, the train remained at Derby for another year.
Meanwhile, the GWML was being upgraded for 125mph HST running which commenced in October 1976. This was made possible after the Wootton Basset to Westerleigh Junction section was closed from May 1975 for five months for wholesale track and signalling upgrade, making it suitable for APT-E testing.
Four years into the project on 10 August 1975, the train reached 152.3mph on one of its test runs on the GWML between Swindon and Reading. During this testing, the APT-E was posed with the prototype HST at Swindon in a PR exercise.
It was also operated between Derby and St Pancras on a regular test basis to test the tilt mechanism on the line’s many curves. The train was not designed for the public to travel on and was in reality, a mobile test laboratory and full of instrumentation and technicians whenever it ran. In fact, it was such a secure operation, all staff were issued with lapel badges to wear when on duty on the train.
The train was built with the help of the aircraft industry using aluminium and alloy bodyshells and was not intended for passenger service as it was more of a mobile laboratory. On-board engineers checked every part of the suspension, traction, aerodynamics, braking, vehicle structure and ride characteristics as the train was being operated. The power car streamlining testing was carried out by fitting a Class 86 electric locomotive with a fibreglass air-smoothed front running at speed on the main line.
This train should not be confused with the BR APT which was electrically powered and did operate in passenger service between Euston and Glasgow from October 1980.
A few years before the APT-E project commenced, the former Melton Mowbray to Nottingham main line was closed to passenger trains but 12 miles of it was retained for test purposes, as it is still used today.
The APT-E reached 143mph on this track in January 1976 during intensive testing on this line. The train ended its operational career in June 1976 and was taken to the National Railway Museum at York and a power car is on display at Shildon.