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|Aldenham Bus Overhaul Works|
|Location||Elstree, Hertfordshire, England|
|Completed||1940s onwards, bus works 1955 onwards|
|Structural system||steel frame|
The Aldenham Works, or Aldenham Bus Overhaul Works, was the main London Transport Bus overhaul works. It was located on the edge of the Hertfordshire village of Elstree and not Aldenham despite being officially called Aldenham Works. In its heyday, 50 buses a week were overhauled there, and it was the most comprehensive bus overhaul operation in the world. It was opened in 1956 and finally closed in November 1986. The buildings were demolished in 1996.
The London Transport site at Elstree had originally been bought for the Northern line extension to Bushey Heath, as part of the 1930s New Works Programme. The site was to have become the main Northern Line depot with Golders Green depot closing. Essentially complete at the outbreak of World War II, the railway extension works stopped due to the hostilities. The site was modified for use as an aircraft factory, producing Handley Page Halifax bombers as part of the London Aircraft Production consortium, together with Handley Page, Duple Coachworks, Park Royal Coachworks and London Transport. After the war and despite the completion of the works and extensive construction of much of the Underground extension, the Northern line plan was finally dropped in September 1949.
With the wartime bus fleet worn out and the existing Chiswick Bus Works struggling to cope, it was decided to redevelop the site for bus overhaul, specifically body and chassis structures, with Chiswick continuing to specialise in the running units (engines, gearboxes, etc.). Construction of the new facility began in 1952. The existing buildings were extended and converted into a bus overhaul works over a 53.3-acre (215,700 m2) site, with its own staff canteen, social club and office blocks as well as the famous main building, test circuit and tilt test shed where London buses were subjected to being tilted on an inverter to assess stability. The site also had a power station on site to provide power for the works.
Although Aldenham had dealt with new vehicles and accident repairs from about 1945 it did not start full scale overhauling of bus bodies until 1949/50 and until 1955 chassis' were still dealt with at Chiswick. At first buses were dealt with on an individual basis, with each chassis and body being re-united after overhaul. A small number of changes of body among the RT family of buses was made during the period up to December 1955, at which point the 'works float' system of overhauling was re-introduced after being suspended during World War II. This meant that vehicle identities were again changed around so as to make full use of licenses. In most cases, each bus arriving in the works was replaced by an identical one carrying the same identity, which meant that it was back on the road the same day in the majority of cases. The system came into full operation in January 1956. The works were officially opened on 30 October 1956, at which date it had a staff of 1,800, which was expected to increase to 2,500.
The post-war standardisation and huge size of the London Transport fleet allowed maintenance along modern production line principles, with work being carried out on a number of buses at once. Several mechanics could focus on specific parts of the vehicle rather than a single mechanic working on a single bus at a time.
- Body rebuilds
- Major accident repairs
- Seat trimming
- Destination Blinds
- New bus preparation
- Tilt testing
Aldenham turned the overhaul of buses into an industrial operation. A bus entering the works would first be inspected and any repairs required would be identified. The vehicle would have its body removed from the chassis, and then the running units such as brake system, axles, springs and other safety critical parts apart from the engine and gearbox would be removed from the chassis and would be inspected and, if needed, overhauled (at Chiswick works). Each one of these sub-structures would be sent off for inspection and overhaul on its own line at Chiswick. The bodies would be placed on an inverting frame and rotated to access the underside so that road debris could be removed by steam cleaning. The body would then be moved by travelling crane to one of the many parallel bays in the main shop area. The body was placed on stands with staging all around for maximum access to all parts of the body.
The overhaul would include such necessary work to return the bus to virtually "as new" condition, and would be tailored to each vehicle depending on condition. For example, the body would have any damaged panels replaced or repaired, seats repaired and re-covered and any updates or modifications to the interior made. The chassis would be inspected, tested and have any service components changed or adjusted. This system of standard interchangeable components meant that when the chassis was ready to be rebuilt into a bus, the first available engine, transmission and body that had been 'outshopped' would be fitted.
It was highly unlikely that a chassis would leave the works with the same body, engine or gearbox that it entered with. Indeed, it was even possible for a bus to enter the works in the morning, and a bus carrying the same fleet number and registration number to leave later the same day - although a completely different vehicle.
Once the chassis and body were re-united, the completed vehicle would be test run around the factory site, which would include a brake test. Providing all was well mechanically, the bus would pass through the paint shop for a new coat of paint and varnish and would be fitted with new fleet number and ownership transfers. Following fitting of newly covered seats and re-certification, it would be despatched out to the receiving garage to return to service.
This modular system meant that buses could be overhauled in a fraction of the time that it would take if each bus was attended to on an individual basis. It was this attention and thoroughness that was largely responsible for buses such as the RT, RF and Routemaster lasting so long.
One of the unusual aspects of the Aldenham overhaul concept was the "Works Float" System. As chassis generally took less time to overhaul than did the bodies, this would have resulted in chassis cluttering up the works awaiting completed bodies. This required the number of bodies in the overhaul system to be greater than the number of chassis in the works. To provide this, a number of vehicle identifications became part of the works float and disappeared off the road, sometimes for years. Effectively, these buses ceased to exist except on paper, to provide the necessary spare components to allow the works float system to operate. This system permitted the number of road licences held to be less than the number of buses in existence, the unlicenced vehicles effectively being the vehicles under overhaul - a considerable financial saving. A system of separate chassis and body numbers was utilised to keep track of these major components. The works float system ceased in the mid-1980s when the practice of body separation was abandoned.
Later off the peg buses such as the DMS-class Daimler Fleetline were less suited to this style of maintenance due to the bodies distorting if removed from their chassis. These vehicles would be overhauled but without separating the body/chassis - indeed, many of them did not last long enough in London Transport service to receive overhauls. Overhauls of vehicles of this type were therefore carried with the vehicle in "built up" form. LT had to set aside a separate area of the works for this type of work away from the "normal" work. Lifting jacks to raise vehicles were installed to enable access beneath. This type of overhaul resulted in the bus being off the road for weeks or even months, and was a very inefficient use of vehicle fleets.
In 1970 London Transport's country area buses were transferred to the state-owned National Bus Company (NBC) as London Country Bus Services. This helped to dramatically reduce the workload of Aldenham, with London Country establishing its own overhaul facility at Tinsley Green near Crawley in Sussex. With NBC in control, its vehicle purchases included more off the peg rear engined buses to replace London Transport standard RTs and Routemasters.
Aldenham was also used to prepare new buses for service, and they would be delivered to the works for preparation. Major accident repairs would also take place at Aldenham if the local garage could not handle the work in question. Typical of this would be the replacement of a top deck lost in collisions with low bridges.
Staff at Aldenham were transported in by bus, with buses running from over 40 London bus garages every day. The fleet included redundant RTs and later used ex-British Airways front entrance RMA vehicles.
However, as financial pressures led to a decline in bus maintenance standards, the scope for overhaul of vehicles was reduced. London Transport's Bus Works Restructuring Programme 1983-4 was followed in October 1985 by the decision to discontinue the practice of completely overhauling each bus every four or five years. This, a shrinking fleet and the arrival of numerous types of non-standard bus not suited to the Aldenham concept made it increasingly uneconomic, and closure in November 1986 was inevitable. Indeed, by this time, the very existence of London Transport as a bus operator was under review, with private sector operation under competitive tender eroding its domination.
Bus overhaul was moved to Chiswick Works on a much smaller scale, then taken over by a short-lived private company called BEL (Bus Engineering Limited).
The site was acquired by Slough Estates, a property developer and stood mostly empty except for occasional storage of cars on the vast site until being demolished in July 1996 to make way for the Centennial Park business park.
Aldenham was an ambitious concept, even in its early days and never worked to its full capacity (part of the works site was leased to British Leyland as a repair and spares storage centre). The cessation of overhaul of buses by Aldenham became evident in an increasingly shabby fleet, not helped by the upheaval in London Transport prior to privatisation of the bus service. The much reduced maintenance also resulted in shorter service life with fleet renewals becoming much more frequent.
Aldenham was the subject of much film time, including a 1957 British Transport film, entitled "Overhaul", about the work taking place at Aldenham. In 1962 the opening ten-minute scene of Cliff Richard's musical film Summer Holiday was filmed at the Aldenham Works, and Cliff's character and friends are all supposed to be mechanics at Aldenham works. Whilst on lunch on a rainy day, they come up with the idea of converting an RT bus into a mobile home and the next 5 minutes shows them at work to the track Seven days to a holiday. These scenes were all shot in the works during the summer shutdown, and employees were used as genuine extras. One shot even shows Cliff on an RT suspended from the crane above the works.
The last film of the derelict works took place in 1992 for the BBC series "Perpetual Motion" which featured the story of the Routemaster and widely on the changes at London Transport. The episode featured samples from overhaul, and later repeated the shots this time of the derelict works with the original voiceover dubbed onto the footage. Access to the site after closure was difficult, and few images exist of the site after closure.
- London Transport Museum Photographic Archive
- - British Pathe film showing a tilt test at Aldenham
- Opening scenes to Summer Holiday 1963 on YouTube
- Seven days to a holiday on YouTube
- Aldenham Bus Works Trade Union Records 1949-85
- GoogleMaps view of the Aldenham site undergoing redevelopment
- Catalogue of the Aldernham Works trade union archives, held at the Modern Records Centre, University of Warwick