London Underground 1935 Stock

The first three two-car units were delivered to Lillie Bridge Depot in October and November 1936. From there, there were transferred to Ealing Common depot,[10] where staff from the various companies supplying the equipment completed installation and arranged acceptance tests. Most of the two-car units were tested and accepted individually, but the units with Metropolitan Vickers equipment ran as four cars.[11] Testing took place on the test tracks which run between Acton Town and Northfields, with the first taking place on 13 November 1936. Testing continued on most weekdays until 8 January 1937. A Press day was held at Northfields depot on 17 November 1936, and the "streamlined wonders" received widespread coverage in national newspapers.[12]

Prior to the production of the 1935 Stock, driving motor cars were designated as 'A' cars if they faced west, and 'B' cars if they faced east. However, for the new stock, the axles were lettered from 'A' to 'D', and the driving motor cars were lettered according to the nearest axle. They were thus designated as 'A' cars in they faced west and 'D' cars if they faced east, a scheme which has been carried forwards to all subsequent stock.[12]

The first train to enter passenger carrying service did so on 8 April 1937 on the Piccadilly Line, and the final one followed nearly a year later, on 10 March 1938. Initially, they ran as four-car trains during the daytime, avoiding the morning and evening peak services. From 26 April 1937, an extra two-car unit was added to the four-car trains at the end of the afternoon service, and the six-car formation ran through the evening peak. Four cars of flat-fronted stock began running from 24 January 1938, but cars 10009, 11009, 10010 and 11010 were transferred to Golders Green depot on the Northern Line on 31 March 1938, so that gauging tests for the 1938 Stock could be carried out. They returned to the Piccadilly Line on 4 July 1938.[11]

The various types of streamlined units were used interchangeably to make up four-car and six-car trains, but the flat-fronted units were kept together. There were significant teething problems with the new equipment, and when the outbreak of World War II made maintenance difficult, the trains were put into storage at Cockfosters depot. Three of the cars found temporary use as air raid precaution (ARP) shelters, one at Northfields depot, and two at Cockfosters. They were parked over a pit and surrounded by sandbags, for use in an emergency. They found no further use in service until the end of 1948, when there were plans to remove the streamlining and drivers cabs from the streamlined cars, and for them to become trailer cars which would run in 1938 Stock trains.[9] Work began on the first conversion in early 1950, and was quite extensive. In addition to the rebuilding of the bodywork, all of the traction equipment was removed, and a complete rewire of the electrical system was needed. When the work was completed, the trailers looked similar to the 1938 Stock, but there were some visible differences. The converted cars only had three windows between the single end door and the first set of double doors, whereas the 1938 Stock had four, and the single door itself was further from the end of the car. Trailer number 012484 was outshopped in August 1950, and entered service on the Northern Line in September. It was monitored to see how it performed, and the remaining 17 conversions incorporated changes to the doors and bogies as a result.[13] The motor cars became trailers 012477 to 012494,[14] and the last one to be used in passenger service was number 012489, which was withdrawn in 1976.

In 1949, the flat-fronted units were modified to run as two-car shuttle trains, and were to be transferred to the Central Line. Some of the streamlined cars had been through an overhaul process, where the bogies had been upgraded to conform to 1938 Stock standards. As the flat-fronted units had not received an overhaul, they were given bogies removed from the updated streamlined cars.[15] The Wedglock couplers at the outer ends were removed and replaced by Ward couplers, so that they could be mechanically coupled to Standard Stock trains, and air hoses were fitted. The Metropolitan Vickers control system was removed, and replaced with the British Thomson-Houston equipment, which had been removed when those units were converted to trailers. The guard's control panel, which had been located in the cab, was moved to the trailing end of the 'D' cars, so that the guard remained in the same position whichever the direction of travel. To ensure that each train ran with two compressors, KLL4-type compressors were fitted to all of the cars.[9]

By August 1950, conversion of the shuttles had been completed. Two units entered passenger service in October, with the final one following in February 1951.[15] Central Line services had been extended from Loughton to Epping on 25 September 1949,[16] and the converted trains were primarily used to provide a shuttle service on this section, although they were sometimes used on the Woodford to Hainault section,[15] which had opened on 21 November 1948.[16] The three trains were moved back to the Piccadilly Line on 17 May 1954, for use on the shuttle service from Holborn to Aldwych. Car 11010 overran Aldwych station on 3 April 1955, and was damaged when it hit the buffer stops. The cab was rebuilt at Acton Works, and the finished result looked more like the 1938 Stock than the remaining 1935 Stock cars. Two trains returned to the Central Line for the opening of the Epping to Ongar service on 18 November 1957, where they were assisted by a three-car unit of 1938 Stock, specially adapted by fitting two compressors to the trailer car.[17]

The third unit, consisting of cars 10011 and 11011, had been moved to Ealing Common depot in early 1957, to be used in a trial of regenerative braking. The concept, which involves the motors being used as generators, and current being fed back into the system for use by other trains, had been tried previously, on the O and P surface stock trains, which were equipped with metadyne controllers. The metadyne controllers were being replaced at the time, as they were proving increasingly unreliable, but London Underground still hoped that the system could be used to reduce energy costs. The 1935 Stock train was fitted with regenerative braking equipment manufactured by British Thomson-Houston, and the substation at Northfields was adapted to cope with the regenerated current. Because it was a trial system, the equipment was installed in the passenger area, and a self-lapping switch was fitted to the brake controller, which tilted as the brakes were applied. Testing of the system ran from May 1957 to early 1958, when a system manufactured by General Electric Co replaced it, and a third set of tests used equipment by Metropolitan Vickers. Although regenerative braking did not become part of the 1959 Stock or 1962 Stock production runs, the British Thomson-Houston equipment was modified to allow tests of rheostatic braking on a test train of 1960 Stock, which paved the way for it to be incorporated into the 1967 Stock built for the newly constructed Victoria Line.[17]

The unit used for regenerative testing was returned to passenger service in May 1960, and rejoined the other two units on the Epping to Ongar shuttle. It was fitted with a modified 1927 Stock trailer, as the other two units had been previously, to provide more passenger accommodation. Once the Central Line had been re-equipped with unpainted aluminium 1962 Stock, the red livery of the 1935 Stock looked incongruous, and they were painted silver between August 1963 and May 1965. The trailer cars were fitted with de-icing equipment in 1964,[17] and the units continued to be used on the Epping to Ongar route, until they were withdrawn from passenger service in 1966, when 1962 Stock replaced them.[18] The units, including the 1927 trailers, were stored at Hainault depot for a time, and then moved to a scrap line at Ruislip depot.[17]

When London Underground were considering the use of articulated trains on the Northern Line, to replace the 1938 Stock, the redundant 1935 Stock was used for trials. Motor cars 10010 and 11010 spent some time at Acton Works for preliminary tests, and were then returned to the Ruislip scrap line.[19] On 15 May 1969, motor cars 10011 and 11011 entered Acton Works for full-scale trials to be conducted. The trailing ends of the cars were cut back so that only one window remained beyond the rear doors. The driving end bogies were replaced by new lightweight aluminium ones, while the trailing ends of both cars were supported by a single steel bogie. The conversion work was completed for testing to begin in August 1970, and information was collected for a year.[18] There were plans to re-equip the Northern Line with 8-car articulated trains, but rolling stock requirements were reassessed when authorisation to build the Heathrow extension of the Piccadilly Line was obtained, and the idea of articulated trains was dropped in favour of using conventional 1972 Stock, similar to that running on the Victoria Line.[20] Following the tests, the articulated unit was found to be particularly useful for shunting, as the beams carrying the current collecting shoes were 64 feet (20 m) apart, enabling it to cross long gaps in the current rails at low speeds. It was given a maroon livery, and renumbered L14A and L14B, becoming part of the service fleet. The aluminium bogies were removed for further testing on a 1972 Stock car in 1975, and the 1935 cars were scrapped at Acton in early 1975.[18] The units on the Ruislip scrap line lasted until they were officially scrapped on 10 October 1971.[21]