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Pauls Railway Web

Advanced Passenger Train - Experimental

The Early Years

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In the later part of the nineteen sixties British Railways had worked on how to increase train speeds on standard track,  while keeping maintenance costs down and at a high level of reliably and flexibility for everyday use.    Fundamental work had been carried out on how wheel sets reacted to the surface they were running on and what the effect of high speed cornering would have on track and ballast.     An optimum cone angel was calculated to maintain a central position of the wheel to rail contact ,  the cone angle being the angle of the surface of the wheel that touches the rail.     This angle reduces the amount of horizontal shift the wheel set would do at high speeds,  i.e. the wheel set would naturally try to stay central between the two running rails.  This was a major step forward in the production of high speed trains and BR were the first to realise the importance of this fact.

apt46s.jpg (29618 bytes) This rather unusual looking vehicle was the very first piece of APT hardware to be produced.    It was used to develop the wheel sets and the cone angle of the wheels, and also to test the effects of high speed cornering.   The iron and steel work was used to simulate the weight of a standard railway coach for that time.

This photograph was taken outside the

Research and Technical Centre at Derby

where the APT was designed and built.

APT -E outside the Research Centre

Note the Advanced Passenger Train - Prototype in the background,  this train followed the successful conclusion of the APT-E project and ran for a short while on the West Coast Mail line until 1986,  see Rob Lathams APT Support Team pages for more information on the Prototype train and its preservation.

In order to prove concepts BR had to build a test skeletal train which became known as the POP train, this was the abbreviation for POWER - 0 - POWER.    This train consisted of two articulated vehicles,  a conventional coach,   filled with monitoring equipment and a diesel locomotive.   Each end of the articulated vehicles were fitted with proposed APT powered bogies and the centre articulated bogie was the proposed APT none powered bogie, I.E. Power - 0 - Power (POP).   This set-up was used to develop the APT articulated bogies,   brakes, suspension and later the tilting systems.     After the Advanced Passenger Train - Experimental development was completed in 1976 the POP train was reused in the development of the Prototype trains and was fitted with APT - P articulated bogies and tilting systems.

apt37s.jpg (31809 bytes) One of the main new features of the APT was the heavy use of Aluminium,  a lightweight and very robust metal more commonly used in the construction of aircraft.   The APT design team used a space frame for the chassis and then pot riveted aluminium sheets to form the outer covering of the vehicle,  this system made each APT-E vehicle around 45% lighter than conventional stock.

The Space frame principle was also taken from the Aero industry and was used extensively on the APT - E vehicles.  This system had the advantage of making it relatively easy to re-design and re-position equipment after construction,   as was proved by the various APT-E re-design programmes carried out during development from 1971 - 1976.

As a speed of 155 mph was to be achieved on the West Coast Mainline the main problem was power to weight output from the motive power unit or units,   diesel power at that time was too heavy and electric traction was proving to be costly and unreliable, also the motors in the class 86/87 locomotives would prove to be under powered for a 12 - 16 coach train climbing Shap or Beta climbs so a risky but fundamental decision was taken to use GAS TURBINE which Leyland were developing for their commercial vehicle marked.    This decission also made the development of the APT more flexible due to the fact that BR could use un-electrified sections of the network for testing.  Each Gas turbine was capable of production 300 Bhp at a sustained rate.

As the evolution period for the APT was to be kept as short as possible the design team were forced to use conventional axle hung traction motors rather than the proposed body mounted motors that were still only at an early design stage,   the axle motors were to used until the variant motors could be developed to a sufficient level of reliability and a high level of tractive effort output could be sustained.

To prove the APT concept the experimental train only need to contain the bare essentials,  this was,  to maintain the required level of power output for 155 mph,  two powercars were required and only two coaches.   These vehicles were codes PC1 (Powercar 1), TC1 (Trailer Coach 1), TC2 (Trailer Coach 2) and PC2 (Powercar 2).

Each powercar of the E train was to contain 4 turbines and 4 alternator sets for motive power and one other turbine and alternator known as the (APU,  Auxiliary Power Until) to produce power for the electrical system on the train.   After power output testing it was found that the 4 turbines could not sustain the required level of power output so the APU turbine and alternator were re-positioned with the rest of the motive power units and a diesel generator was fitted in the APU bay at the rear of each powercar.    Leyland also up-rated the gas turbines to 350 bhp, thus giving the train 5 motive power units and 1 APU at each end.   Each turbine was accompanied by a control unit fitted inside TC2.

Trailer Coach 2 (TC2) was to be the test bed,  this coach contained all the monitoring equipment and equipment necessary to test the various systems on the train,  1 to 4 engineers worked in this coach during testing.

Trailer Coach 1 (TC1) was to carry the support team and also to test re-design layouts before refits.

Each coach was also fitted with air conditioning and a hydrokenetic brake power pack (when commissioned).

apt17s.jpg (50599 bytes) While making the train go faster the centrifugal forces exerted on passengers had to be reduced when cornering,   the APT was going run on the steep and curvaceous West Coast Mainline so this problem had to be addressed.    A tilting coach to compensate for the force being applied was the answer,   but a tilting train had never been built before so the design team had to start from scratch.    There solution was simple but very effective.

A central mounting point was fitted at either end of a bogie,   the bodywork was balanced on the mounting point,  two hydraulic rams were fitted at each end of the vehicle, and at either side of the mounting point , these supported the bodywork and held it level.    As the vehicle is needed to be tilted one pair of the rams are lifted and thus the vehicle tilts.   The whole assembly resembles a see-saw. Click here to see a diagram.   

Each hydraulic ram is supplied fluid by a TILT PACK which is fitted within the vehicle bodywork.   Tilting is controlled by means of an Accelerometer,  which acts like a spirit level, but is also affected by centrifugal force,  as the bubble moves off centre the electronics in the tilt pack compensate by tilting the vehicle into the curve,  a maximum tilt of 9 degrees can be achieved during everyday running, but the system is capable of tilting up to 12 degrees if necessary.    The tilt system allowed APT to run at between 25 - 40% faster while maintaining the conventional level of  passenger comfort,  but the train was also perfectly safe to run at the higher speeds even if the tilt system failed.

E Train when first built was fitted with Mk1 tilt packs, these packs proved inadequate for there task and even before the trains first run TC1 and TC2 were fitted with Mk2 packs. Although the TC1/TC2 tilt system had been commissioned by the time of the first run, the BR hierachy decided that the train must run passive for its first trip out.

The train was capable of running at high speed while maintaining passenger comfort,  but the train also had to be stopped within standard signal distances and convention friction brakes were found to be incapable of doing this job so very early on in the APT programme it was decided to develop a new braking system,  this became known as the Hydrokenetic brake.    A hydrokenetic brake is a water turbine made as inefficient as possible so that energy can be dissipated   without generation excessive amounts of heat.    A pressurised fluid is pumped through a tubular axle and then passed back through a set of turbine blades,  these blades are rotation at the same speed as the wheel set,  the greater the pressure of fluid pumped into the wheel set the harder it becomes for them to rotate,  energy is stored in the form of heat in the fluid,  this is in turn returned to a central holding tank and cooled before being re-used.  On the APT-E friction brakes were used below 70 mph and the hydrokenetic brake was used up to 155 mph.     APT-E was only allowed onto the mainline once the fitting and commissioning of the HK brake was completed and tested.

APT-E was designed originally for single man operation,   but this was blocked by ASLEF who blacked the train for nearly a year after its first mainline run until extra seats were fitted behind the driver.

apt24s.jpg (38700 bytes) In 1972 this technical diagram was published in Flight magazine,   another point of proof between the Aero industry and and design heritage of the APT-E.

Although correct at the time of printing the train design did change from the version shown here,  most notably just behind the cab,  this drawing shows the original train as there is only one turbine in the first compartment and it shows the turbine in the APU (Auxiliary Power Unit) bay at the rear of the powercar instead of the diesel generator.

apt48s.jpg (12999 bytes) As it was not possible for BR to develop the APT-E on the mainline,  this would disrupt normal services,  they re-instated a section of track 13 miles long,  this became known as the Old Dalby Test Track and APT-E would run many miles during its development along this route.   Once being part of the Midland line it contained all the features of the normal rail network,    Tunnels,  tight bends,  poorly maintained track,  trackside obstacles, everything you would expect to find on a route from anywhere to anywhere.

To find out more about the "OLD DALBY TEST TRACK" visit "DAVE COXON's OLD DALBY TEST TRACK SITE"

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Email me on Paul@APT-E.Org

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