London Underground electric locomotives

London Underground electric locomotives
A print from the Illustrated London News showing a City & South London Railway electric locomotive and train
Stock type	Deep-level tube
Notes

Electric locomotives were first used on the London Underground when the first deep-level tube line, the City and South London Railway (C&SLR), was opened in 1890. The first underground railways in London, the Metropolitan Railway (MR) and the District Railway (DR), used specially built steam locomotives to haul their trains through shallow tunnels which had many ventilation openings to allow steam and smoke to clear from the tunnels. It was impractical to use steam locomotives in the small unvented tubular tunnels of the deep-level lines, and the only options were rope haulage (as on the Glasgow Underground) or electric locomotives.

The C&SLR was opened just a few years after the very first use of electricity to drive rail vehicles (trains or trams) and the primitive locomotives reflected this. Over the next 15 years, motors became smaller, gear drives and motor suspension were developed and reliable multiple unit control became available. Electric multiple unit trains became the standard, but electric locomotives were still being built.

From 1903, the MR and the DR began to electrify the central parts of their lines for use by electric multiple units (EMUs). On both railways carriages were hauled by electric locomotives that were exchanged for a steam engine to run over un-electrified distant sections. The last steam-hauled passenger trains were replaced in 1961.

When not hauling passenger trains, the electric locomotives were used for shunting and for hauling departmental trains. Some locomotives, as on the MR, were retained just for these duties. Rather than buy additional locomotive for this work, as was required with the battery-electric locomotives, makeshift locomotives were created from withdrawn passenger vehicles of at least three types, which were modified to haul trains over any part of the system or shunt rolling stock at Acton Works.

When the City & South London Railway (C&SLR) was authorised in 1884, it was intended to be a cable-hauled line, but during the construction phase, the promotors decided to use electric traction, despite the fact that the technology was in its infancy. Two prototype locomotives were built by Mather & Platt in 1889, to a design by Dr Edward Hopkinson, with Beyer-Peacock supplying many of the mechanical parts. No. 1 used motors mounted directly on the drive axles, while No. 2 had motors driven through gears. Trials were conducted in December 1889 with No. 1 and two passenger cars. No. 2 was also used for testing, but it is not clear whether it pulled any cars. A production run of 14 locomotives was then built, numbered 1 to 14, duplicating the original numbers 1 and 2. Each had four wheels, with Edison-Hopkinson motors fitted to the axles, which were permanently wired in series. A 26-step rheostat was used to control the speed, and a switch which altered the connections to the armature was used to reverse the direction of travel.