Rolling Stock Evolution, by Mike Portillo
The prototype units on test for what would become the new "standard suburban" train - or "1972 design".
British Rail's rolling stock, the selection of trains that is, underwent a rapid transformation from the mid 1960s to mid 1970s. Steam was finally phased out by 1975, fully replaced by electric and diesel traction, and removing a great deal of smoke and dust from city centres. The evolution away from steam took time; at first British Rail's strategy was to electrify lines and move straight to electric traction - the long project times on electrifying routes and the clamour from both political circles and the public meant it was impossible to wait for this process to complete however. Diesel locomotives would take up the mid-position on many routes which were not to be quickly forthcoming with electricity; the long distance Great Western services embraced fast diesel traction early on.
Shorter distance services were quicker to transform. Routes on almost all radial rail routes in to and out of London were electrified by the 1970s, and would quickly be served by a fleet of new electric multiple units. The 4 car, first generation was for British Rail a ground-breaking design - able to be used on short distance urban routes and longer distance commuter routes with ease, reliable under the 1,500v DC system, and manufactured in large numbers for the different metropolitan areas of the United Kingdom; London, Glasgow and Manchester. The design would later be adopted and evolved as a standard for the second generation of multiple units, utilising many formerly cutting edge features, and bringing them in to one standard design.
The new "1972 Design" was ground breaking due to these changes. It featured electrical compatibility with both the third rail 750v DC system as well as the overhead 1,500v DC system, and could easily be manufactured in a 2-coach, 3-coach or 4-coach formation. The structural design was taken from the evolving "Mark 3" coach design, which would be used for longer distance services, with power operated doors (moving away from the "slam door" approach), and new improved passenger comforts. Seats were of a new ergonomic design, and they were sealed trains with heating and air conditioning capabilities. Regenerative capabilities by using the motor in reverse was provided, providing substantial maintenance advantages by reducing brake wear.
These trains turned out to be the greater part of Beeching's legacy today; the mindset switch in British Rail away from just traction development to improving the passenger experience. The formation used had the outer coaches on each end with motors in, and the middle 1 or 2 coaches as unpowered trailers. This would later evolve by 1980 in the "TMU" or "Trailer Multiple Unit", a self contained rake of 4 coaches with operating cabs in, but no motors - designed to be operated in combination with a locomotive on one end, and allowing bidirectional working without moving the locomotive from one end of the train to the other at it's terminating point. This approach would also allow an easy change in locomotive - envisaged as diesel to electric - without needing to swap out the entire train.
The APT's problems with tilting were well documented by the media
Elsewhere and away from suburbia, there were pressing concerns. A meeting of the British Rail Board to discuss the Intercity business was held in 1971; the Advanced Passenger Train was high up on the agenda list. It would be easy to consider British Rail as schizophrenic at the time; long term planning was frequently at odds with itself. The slowly expanding network of electrification was at odds with the gas turbine powered APT, and conversion of the train to overhead power was the obvious choice. However, the "reliable" 1,500v DC system could not supply enough power for high speed operations much above 100mph, something which BR was loathe to publicly admit for reasons of PR - it's choice of system had come in for considerable criticism from some sectors. Problems with the Leyland gas turbine also began to make gas turbine propulsion unpopular, and Leyland's withdrawal of the gas turbine from the company's road vehicles also led to distrust of long term support despite promises to the contrary from the company. By accident, this would turn out to be an excellent move - 1973 brought a severe oil & gas crisis, with prices almost trebling, severely undermining the economics of such a gas turbine train.
There was also the vocal opinions of those "traditionalists" within BR - predominately the engineering section - who sought a more low key high speed train, with less cutting edge features resulting in far more reliability both in service and for any introduction of such a train, with severe doubts now being placed over the target of "in service by 1978" of the APT. Without tilting though, speed improvements would be difficult to get - tilting would allow faster speeds in curves, whereas straight tracks were limited to 100mph (now 110mph) by electrical systems. It seemed highly unlikely that the Government would authorise new truly high speed line construction through the English countryside. The hydrokinetic brakes were also effective, but complicated and problematic, although a switch to electric traction offered an easy way to provide additional brake force, via regenerative & rheostatic braking with the motors in reverse.
Problems appeared to be mounting for the Advanced Passenger Train. However, in 1973, British Rail decided to finally close the Great Central Main Line after it's freight usage dwindled, and in what turned out to be a fortuitous case, someone asked "why don't we fit the GCML with 25kV AC overhead power for high speed operations and just use that?". It was a proposition with many complications and difficulties, but also many advantages.
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Notes: Several things to note here:
- The second generation of stock is beginning to roll out here roughly as per OTL, but again with a little more standardisation. However the "trailer set" (my version of Class 438) is pushing out here, and is an answer to locomotive operation with different locomotives; an operational model which seems remarkably common in places such as the DACH region.
- The APT stumbles forward...until someone mentions the GCML. This is not a straight forward solution
This chapter has been brought to you with inspiration courtesy of my day in the Siemens Traincare Depot in Three Bridges (where they are maintaining the Class 700 units for Thameslink)! Completely unrelated to this, was only there on work business which is usually completely unrelated to trains.