The summer of 1960 saw the introduction of the first diesel-electric Pullmans, an effort by the British Transport Commission to lure wealthier travellers away from roads and domestic air travel and back onto trains via the luxurious confines of a Pullman carriage.
It turned out to be an ill-fated venture, but prior to its demise The Engineer’s reporter revealed that five trains were built by the Metropolitan-Cammell Carriage and Wagon Company to provide services on the London Midland and Western Regions of British Railways.
Two of the trains were six-car sets for the Manchester- Leicester- London route serving first class passengers only. The other three were eight-car formations with first-and second-class accommodation for Bristol- London and Wolverhampton- Birmingham- London services. The trains were supplied with 1000hp power cars at each end and included two kitchen/parlour cars to serve meals to passengers at their seats. All the stock was air-conditioned and a six-car train in working order weighed 299 tons, an eight-car train 364 tons.
“In each power car of a train the main and auxiliary generator group is driven by a N.B.L. /M.A.N. 1000hp, twelve-cylinder, vee engine supplied by the North British Locomotive Company, Ltd., together with the cooling groups and engine accessories, as sub-contractor to the G.E.C,” said The Engineer. “From each power car current is fed to four traction motors, two in the rear bogie of the power car itself and two in the leading bogie of the adjacent vehicle. Immediately behind the driving cab is the Serck radiator unit with Serck-Behr hydrostatic fan drive, and beyond this is the engine and generator set, a bulkhead separating the engine from the generators.”
The Engineer continued: “Main generator continuous ratings at 1500rpm are 1700A, 383V, 650kW or, 1250A, 523V, 650kW. The auxiliary generator, carried on an extension to the main generator shaft, is rated continuously at 91A, ll0V) 650/1500rpm, 10kW.”
A 36-line control cable ran through the train for simultaneous control of the two power plants and there were 10 control notches, the first three building up the generator excitation while the engine ran at its idling speed of 340rpm, and the remainder increasing the engine speed in steps to its maximum. Automatic control of generator excitation by a servo-operated field regulator was effective from steps three to ten.
“Field-weakening of the traction motors takes place in the appropriate conditions under the control of a transition relay in the generator field circuit,” said The Engineer. “A single weak-field step is provided by diverter resistances, which are mounted on top of the main switchgear cabinet. The housing contains the diverters for the four motors, the value of those for the two motors in the bogie of the adjacent coach being adjusted to allow for the voltage drop in the inter-coach cable connections.
A current-limit relay arrested the increase of generator excitation by the automatic load regulator during acceleration of the train if the current exceeded a predetermined setting.
“When the current falls, with increasing train speed, to the relay drop-out value, the increase of excitation is resumed under the normal control of the load regulator,” said The Engineer. “On the final power notch an eight-car train will balance on level track at its maximum service speed of 90mph, and up a gradient of 1 in 100 at 54mph.
These trains are the first diesel units on British Railways to have fully springborne traction motors, added The Engineer.
In an essay titled ‘Metro-Cammell Diesel-Electric Pullman Trains’ by R.P. Bradley, the author noted: ‘The reasoning behind the introduction of these units was basically to attract the businessman to rail travel; or perhaps to return to rail travel, for BR had by 1960 to be on a competitive footing with air transport.
In its June 23, 1960 press release the British Transport Commission’s press release said: “These 90mph de-luxe diesel expresses…are of an entirely new type designed to bring a fresh conception of main-line railway passenger travel to Britain, with superior standards of comfort, and a personal service of meals and refreshments for all passengers.”
Various factors, however, mitigated against the success of the new Pullman’s, including the electrification of the LMR and West Coast Main Line
“On speed terms, competition with the electric services was easily ruled out, and by 1967 the Pullmans were less patronised than ever,” wrote Bradley. “One of the last duties of one of the power cars was during the coal strike of the winter of 1972/1973, when it acted as a standby generating set at Swindon, a far cry indeed from the proclamations of the spring of 1960,” Bradley added. “Withdrawal of all the sets took place in May 1973, when they were not quite thirteen years old.”
There is, however, a silver lining to the story of the diesel-electric Pullmans in that their dual power car configuration was adopted in the design of InterCity 125 high-speed trains that are still in service in one form or another today.