London Underground Battery-electric Locomotives - Main Battery Locomotives

Main Battery Locomotives

In 1936, the decision was taken to purchase a batch of new battery locomotives, and an order was placed with the Gloucester Railway Carriage and Wagon Company for nine vehicles, six of which would be fitted with GEC traction control equipment, while the other three would be fitted with metadyne units. The GEC-fitted machines weighed 53.8 tons, and were numbered L35 to L40, while the Metadyne-equipped ones weighed an extra 2.2 tons, and were numbered L41 to L43. Both types, when pulling a 200-ton ballast train, could run at 30 mph (48 km/h) when supplied with power from the current rails, and at half that speed when working on batteries.

The metadyne-fitted locomotives had new bodies, but the bogies and motors were removed from redundant Metropolitan line stock and refurbished at Acton Works. Similarly, the metadyne equipment was removed from an experimental train and reused. A metadyne unit consists of a rotating machine, which converts the constant voltage supplied by the battery to a constant current, which feeds the motor. The metadyne system is more efficient than conventional starting resistances, particularly when the locomotive starts and stops frequently, or when it needs to run for long periods at slow speeds. For cable laying work, the metadyne-equipped locomotives could pull trains of 100 tons at 3 mph (5 km/h) for considerable distances, without any sign of overheating. Despite the advantages, their complexity resulted in them becoming unreliable, and they were withdrawn in 1977. L41 and L42 were scrapped soon afterwards, but L43 was used for testing purposes for a further three years.

The locomotives fitted with GEC controls used an electro-pneumatic controller, with 28 steps, which allowed the four motors to be connected in series, in two parallel-series pairs, and all in parallel as the speed increased. Pairs of locomotives could be operated in multiple, and motors 1 and 3 or 2 and 4 could be selected if there was a failure of the other pair. As built, the vehicles were 54.3 feet (16.6 m) long, and could pick up power either from a standard four-rail configuration, or the three-rail configuration of the Central London Railway, until it was converted to four rails in 1940.

The next batch of seven vehicles were manufactured by R. Y. Pickering and Co Ltd, who were based in Wishaw, Scotland. The traction control equipment was by GEC, although the batteries had a larger capacity than the previous batch. The motors were reused from passenger stock which was being withdrawn at the time. One important improvement was the addition of runners and a lifting device, which enabled any battery cell to be removed from its rack and lowered to the ground through an aperture in the floor. This feature meant that the batteries could be changed without using an overhead crane in a lifting shop, freeing it for more important work. An eighth locomotive was built by staff at Acton Works in 1962, partly as an exercise to prove that the workshop could compete for this type of work. This vehicle was initially numbered L76, and took part in the Metropolitan Railway centenary celebrations, held on 23 May 1963, when it propelled a replica of the original inspection train used by Gladstone.

Metro Cammell received the order for the next batch of thirteen locomotives, which were numbered L20 to L32. The first one was delivered on 8 December 1964 to Ruislip Depot. They were part of a programme to phase out the last remaining steam engines, but the Victoria line was also being built at this time, and some of the battery locos were fitted with automatic train operation (ATO) equipment, to enable them to work on that line. Traction control equipment was by GEC, with the batteries supplied by DP Battery Co Ltd. As with previous batches, parts of the locomotives were refurbished; in this case, the bogies, traction motors and compressors were supplied by Acton Works. Unlike earlier models, each vehicle was fitted with two compressors, allowing them to work singly. The last steam engines were withdrawn soon afterwards, and an order for five more battery locos was placed with Metro Cammell in 1969. These worked on the Jubilee line construction, and were numbered L15 to L19.

The construction of the Jubilee line and the Heathrow extension of the Piccadilly line required yet more works trains, and eleven more locomotives were ordered in 1972, with delivery in 1973. They were built at Doncaster by British Rail Engineering Ltd. The motors were refurbished from redundant District line stock, but the bogies were new. Although based on the standard Z-type bogie used since the 1930s, they incorporated roller bearings, rather than white metal axleboxes and suspension bearings. Three of the locomotives were built to replace the three metadyne vehicles, but those were not actually withdrawn until 1977.

A final batch of six locomotives were built by Metro Cammell and were delivered in 1985 and 1986. They incorporated all of the improvements made to the previous vehicles. For the first time, they were specified in metric units. New features included entry to the cabs through a central door, rather than a side door, missile-proof windscreens with windscreen wipers, and the ability to charge the batteries while operating on electrified lines. One departure was the fitting of traction control equipment by Kiepe, which prevented them from working in multiple with any of the previous machines. They were not a success, as five of the six had been withdrawn from service by August 1993, while a decision was made about their future, and the sixth was withdrawn some time later.