What does anyone know about DEL120. All I have is a brief description in the 'Red Panniers' by John Scott-Morgan and Kirk Martin. It looks to have had a cab made up of parts from a pre WW1 Central London motor coach tacked onto a well wagon with the rest built up from parts of other stuff. It apparently lasted until July 1958. Does anyone know any detail about its construction, specifications and service life and just why it was not a success (other than the obvious 'diesel fumes in tunnels' problem). Also, why would it need pick-up shoes? Thanks.
Extract from my article in Underground News September 2004:
DEL 120
As we have seen, between early-1936 and mid-1938, various schemes for diesel-electric locomotives had been proposed. Although the details differed, it was the intention with all the designs that some degree of compatibility with steam locomotive performance was desirable, if not essential. If possible, diesels should be able to match the steam locos and have 10-15% extra power in reserve to cope with any extra work which might arise in time. It was also suggested that, since diesels could not be used in tube tunnels, they could be built to surface line gauge. This was eventually rejected on the grounds that the tube line extensions were largely in the open and that the diesels would have to get through the tunnels to work there when required.
The slow progress on the design work for the prototype Metadyne-diesel authorised back in March 1937, continued through to the middle of 1938. The high price of the Metadyne scheme almost stopped the whole idea of diesels but, in the late summer of 1938, matters were brought to a head by the imminent demise of one of the steam locomotives, former Metropolitan Railway E class 0-4-4 tank engine no L47. The LPTB was told that this engine needed replacing and that it could be replaced by the prototype diesel locomotive. It would be a prototype for future steam loco replacement and would provide useful experience in the design and running of such machines.
This proposal was ratified in December 1938 and money was formally allocated for construction. It confirmed the March 1937 decision but there were some modifications to the specification. Now the intention was that it should be primarily an electric locomotive of sufficient power to haul a 300-ton train from Lillie Bridge to Rayners Lane in 30 minutes. A diesel engine and generator was to be provided but this would give rather less power to allow the same train to do the same journey in 50 minutes. Four 240 h.p. traction motors and a diesel engine of 400-450 h.p. were to be provided. It was, in essence, an electro-diesel.
The main reason for the change in specification was the realisation that most night-time works trains travel to the worksite immediately behind the last passenger train while the current is still on. The diesel engine would only be required at the worksite for shunting etc. and the train would proceed under electric power back to its depot as soon as the current was switched on in the morning, running ahead of the first passenger train. The newly built battery locos were already working in a similar fashion and this method of operation has continued ever since.
The approval for the construction of the diesel loco was at a price of £6500. This comparatively low price was possible because, apart from the diesel engine and generator, most of the rest of it was second-hand. The scheme to construct sleet locos from pairs of redundant Central London motor cars, suitably chopped about and then fixed back-to-back, was extended to the diesel loco. This idea also conveniently met the tube loading gauge requirements.
The cars actually used for the diesel loco were ex-Central Line “Ealing Stock” motors Nos. 3930 and 3933, originally built in 1917. They had been replaced by Standard Tube Stock as part of the 1935-40 New Works Programme. Their driving ends and equipment compartments were kept while the passenger saloons were removed. A new central “well” was constructed between them to house the diesel engine and generator. The motors, bogies and electric traction control equipment were also from the Central London cars and their front halves were little altered apart from the provision of de-icing equipment on the bogies.
As it was still intended that another nine of these locos would be built to replace the steam locomotives, eighteen more Ealing Stock motor cars were set aside and were stored at Cockfosters Depot pending their conversion.
The prototype was not completed until November 1940, when it was given the number DEL 120 and was weighed, reaching a total of 62.2 tons in full working order. This was some four tons heavier than planned and led to a ban on its use north of Golders Green because the Civil Engineer was afraid of what it might do to his bridges. The official photographer was summoned to Acton Works and took pictures of the new machine in the works yard on 16th January 1941. It was finished in the new standard grey livery being used on all electric locomotives at the time.
Although new in its purpose and present form, the only major parts of DEL 120 which were actually new were the diesel engine and generator. Sulzer Bros., English Electric and Davey Paxman had all been approached, but the engine was eventually supplied by Petters and it was of the superscavenge, airless injection, two stroke cycle, cold starting type. It had six cylinders and was capable of developing 506 b.h.p. at 675 rev/min. A compressed air starter used air stored at 350 lb/in2 in a reservoir which was recharged from two high pressure cylinders through a reducing valve. The high pressure cylinders had air stored at 1800 lb/in2.
The generator was supplied by Brush. It was of the compounded shunt type designed to operate at 675 rev/min giving 750 amps at 450 volts. For running on the line, the usual series-parallel control was provided. The equipment was housed in the original switch compartments over each bogie, the two motors on each bogie being controlled by the equipment above it. The two equipments were operated in multiple but either one could be switched out if a defect developed.
Owing to the limited maximum output of the generator, it was not possible to allow both the traction equipments to ‘‘notch up” together when drawing power from the generator. The control was arranged for normal series operation but when changing to parallel, one equipment “dropped out” whilst the other notched up in parallel. When the first equipment had reached full parallels and the current demand had fallen to half the maximum possible generator output, the second equipment switched in and notched up to parallel. A selector switch allowed either equipment to be first in the parallel sequence so that if either failed, the other could be used in parallel on its own.
It was originally claimed that DEL 120 could haul 500 tons on the level and 300 tons up a gradient of 1 in 34 but no record can be traced that this was ever achieved once it began work. Indeed, over the years, the loco had difficulty achieving loads of half that weight. However, before such troubles came to light, a series of trials was carried out over the test tracks between South Ealing and Acton Town during January and February 1941. On March 9th, the first of a number of loaded runs was made with two brake vans, a flat car, six loaded wagons and two ex-Metropo1itan electric locomotives to form a load of 290 tons. The locomotives were included in case the diesel disgraced itself by breaking down. They actually came in useful on a test run on 31st May when DEL 120 stalled at the entrance to Lillie Bridge yard because of wheelslip and they were used to get the train in.
In May 1941, a full description of the loco was published in ‘‘Modern Transport” with emphasis on the use of redundant material being useful for the war effort, although this had not been in the minds of anyone at the design stage. From this time until the following October, some further trials were carried out and some minor modifications done. During October the steam loco drivers were given a two-day diesel conversion course at Neasden which included some handling practice in Neasden yard. Shortly after, DEL 120 was absorbed into the locomotive stock and began turns on the Watford “tip” trains.
One fact which became apparent during the trials was that the generator characteristic was not correct. However, there was not much that could be done about it at the time and people had to learn to live with it. Had this been the only fault, it might have proved a useful tool but the locomotive soon began to give trouble and it made its debut on the failure sheets by putting 52 minutes on the Metropolitan service on 24th November 1941, when it broke down at Harrow and had to be rescued by a steam loco. Further trips to Watford were made until, in March 1942, it was taken out of service for engine repairs. From then on various duties were undertaken on the Metropolitan Line until, after the war, it was used on the western end of the Central Line during the building of the extension to Ruislip and the reconstruction of Wood Lane Depot. There were also long periods when it was out of service awaiting repairs to its engine or generator. An average of eight weeks at a time was common. By mid-1951, after an overhaul at Acton Works, it was at Hainault, where it was stationed for over two years. Because of its poor service record, a steam loco had to be hired from the Eastern Region from time to time to work ballast trains in the area.
By 1954 DEL 120 was back at Neasden but it was confined to shunting duties because of its unreliability. Even then it did not escape trouble as letters of complaint were received from local residents about the noise from its engine. Even the Town Clerk of Willesden wrote officially after complaints to his office. These incidents, together with the unreliability of the diesel engine, prompted the suggestion to convert the loco to simple electric operation. After all, it was no longer used when current was off, so the engine was actually redundant. This was approved in October 1954 and the diesel engine and its generator were removed and sent to Ruislip depot where they were available for inspection by any prospective buyers. They were eventually bought by scrap dealer R. Adair & Co. in July 1955.
Following its conversion to electric operation, it is recorded as having been renumbered L120 in the official stock lists but there is no evidence, photographic or otherwise to show that this was actually done on the loco. It was now permanently at Acton Works and it was to be used as the works shunter. Unfortunately, it was quite unsuitable for the job, the visibility from the driving position being very poor, particularly when shunting high wagons or surface stock coaches and the crews did not like it. There was continued pressure from the authorities at Acton to get DEL 120 accepted for these duties because the Met loco which was usually used was needed to cover the withdrawal for re-equipment of the electric locos being used on the Aylesbury trains. In spite of this pressure, DEL 120 was little used, even after offers to the crews of rear view mirrors and periscopes and, in March 1956, it was stored out of use. It was officially withdrawn in July 1958 and it was scrapped at Acton in the October.
DEL 120 never achieved the great things hoped for it and the scheme to build nine more was never carried out. The eighteen Ealing Stock motor cars stored at Cockfosters were scrapped after the war. The loco’s failure was largely due to the engine and generator not being able to provide the power required and to its appalling reliability record. During 1951 it only averaged a daily running time of one hour and in a seven-month period during 1953, it ran for only 5½ hours.
The diesel did, of course, have the cards stacked against it. Arriving in the middle of the war meant that not enough attention could be paid to it during its early running and no doubt, steam loco maintenance techniques were applied to it when a much gentler approach was needed. The staff disliked it, particularly because of the noise, which drowned out whistle signals during shunting operations. Also, it is very tiresome to have to change ends constantly during such work. The noise problem caused it to be banned from night work in 1943, because of complaints from lineside residents. However, in spite of all these problems, London Transport was never sufficiently discouraged to give up the idea of using diesels if the right type could be found.
The determination to keep trying to find an acceptable alternative to the steam locomotives surfaced again immediately after the Second World War. In 1946, another attempt was made to design a tube sized diesel-electric locomotive. Only two drawings have survived but they clearly show that the idea was not dead. They were both to have a diesel engine mounted in the centre of the body, which was to be 52 feet long over buffers. The electrical equipment was to be the 1938 tube stock PCM type and it was to have been mounted under the floor. Batteries were to be provided on either of the centrally positioned diesel engine. One of the designs had a conventional double-ended body with cabs not unlike those of 1938 Tube Stock driving cars. The other was more unusual in having the batteries housed under low-level bonnets on either side of the central structure which housed the engine and the cabs. The result was a sort of 1938 Tube Stock shaped camel-backed locomotive. Neither design seems to have progressed any further than these drawings and some studies carried out by BTH, the PCM equipment suppliers, to test the viability of the proposed traction system. Perhaps it was their report which killed it.
