| Industry | Bus manufacturing |
|---|---|
| Founded | 1946 |
| Defunct | 1964 |
| Owner | AEC Leyland |
British United Traction (BUT) was a manufacturer of railway equipment andtrolleybuses. It was established in 1946 as ajoint venture betweenAEC andLeyland.
British United Traction was established in 1946 whenAEC andLeyland amalgamated their trolleybus interests. Neither had produced trolleybuses since the early years ofWorld War II. With both forecasting that demand would return to pre-war levels as networks began to close, a joint venture was formed. The new company was organised so that AEC would design and produce vehicles for the UK market while Leyland looked after export markets, although there were some exceptions to this. The only noticeable difference between the manufacturers' output was the wheels.[1][2][3]
Initially vehicles were produced at Leyland'sHam, London factory, with the first vehicles completed in 1947 forJohannesburg. After the factory closed 1948, production moved to AEC'sSouthall and Leyland'sLeyland, Lancashire factories. Following AEC's acquisition ofCrossley Motors, AEC transferred its production to the latter'sStockport factory. Trolleybus production wound down in the late 1950s, however a final batch forWellington was built atScammell's,Watford factory in 1964.[1][2][3]
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British United Traction was a major supplier ofdiesel engines forBritish Rail's first-generationdiesel multiple units. These engines were built in 125 hp (93 kW) or 150 hp (110 kW) versions and were branded BUT, although manufactured by BUT's parent companies, AEC and Leyland. There was also a 230 hp (170 kW) BUT engine, manufactured byAlbion, a Leyland subsidiary.
A 275 hp (205 kW) version was supplied to theUlster Transport Authority for itsUTA MPD class railcar.
| BUT / ACV railcars | |
|---|---|
| In service | 1952–1960 |
| Manufacturer | British United Traction Associated Commercial Vehicles (AEC,Park Royal Vehicles) |
| Orderno. | List
|
| Family name | First generation |
| Replaced | Steam locomotives and carriages |
| Constructed | 1952, 1955–1957 |
| Scrapped | 1963 |
| Number built | 3DMT/DMS, 4DMBT/DMBS, 4TT/TS[a] |
| Number scrapped | All |
| Formation | 1-, 2-, or 3-car sets |
| Capacity | DMT/DMS: 41 (prototype car), 34 (production cars) DMBT/DMBS: 28 TT/TS: 48 |
| Operators | British Rail |
| Depots | Watford |
| Specifications | |
| Car length | 37 ft 6 in (11.43 m) |
| Width | 9 ft 0 in (2.74 m) |
| Height | 11 ft 4 in (3.45 m) |
| Wheelbase | 22 ft 0 in (6.71 m) |
| Maximum speed | 45 mph (72 km/h) |
| Weight | 15 long tons (15 t) (motor cars), 10.5 long tons (10.7 t) (trailers)[4] |
| Prime mover(s) | AEC 6-cylinder diesel, one per motor car |
| Power output | 125 bhp (93 kW) each engine |
| Transmission | Mechanical: 4-speedepicyclicgearbox |
| Coupling system | Screw-link couplings |
| Track gauge | 4 ft 8+1⁄2 in (1,435 mm) |
In 1952, British United Traction introduced a prototype diesel-mechanical multiple unit as a demonstrator. This was followed by orders for production units built from 1955 to 1957. The units were designed by BUT and constructed byAssociated Commercial Vehicles group companies, with underframes and engines byAEC and bodies byPark Royal Vehicles. Instead of bogies, each vehicle had a two-axle four-wheel arrangement. The demonstrator unit was introduced as a 3-car set with two motor cars and a centre trailer car. In addition to operating as either a 3 or 2-car set, each motor car was equipped with driving controls at both ends and could operate as single-car units, with a similar configuration to the laterBritish Rail railbuses.[5]
The demonstrator unit underwent a series of trials across allregions of British Railways, often on low revenue routes. The first trials were operated betweenDidcot andNewbury, followed by trials onHigh Wycombe-Princes Risborough,Epping-Ongar,[6]Watford-St Albans,Chalfont & Latimer-Chesham,Bangor-Amlwch,[7]Ayr-Dalmellington,[8]Hull-South Howden,Birmingham-Solihull,Gravesend-Allhallows-on-Sea,[9]Wellingborough-Higham Ferrers andHarrow-Belmont services.
BR acquired the set in 1955, together with a second 3-car set and a spare motor car and trailer. Under BR ownership, these units worked on regularWatford-St Albans services. A third 3-car set was delivered in 1957 and operations were expanded to include regularHarrow-Belmont services.
The units were unreliable in regular service, and were noted for their poor ride quality. By 1961, all vehicles had been moved toDerby Friargate for storage. No other use could be found for them, and all units were subsequently withdrawn and scrapped atDerby C&W Works by 1963.[10]
| Lot No. | Type[a] | Diagram[b] | Qty | Fleet numbers | Notes |
|---|---|---|---|---|---|
| 30128 | Driving Motor Third (DMT) | 500 | 1 | 79740 | 41 seats |
| 30128 | Trailer Third (TT) | 500 | 1 | 79741 | 48 seats |
| 30128 | Driving Motor Brake Third (DMBT) | 500 | 1 | 79742 | 28 seats |
| 30174 | Driving Motor Brake Third (DMBT) | 506 | 2 | 79743-79744 | 28 seats |
| 30175 | Driving Motor Third (DMT) | 506 | 1 | 79745 | 34 seats |
| 30176 | Trailer Third (TT) | 506 | 2 | 79746-79747 | 48 seats |
| 30214 | Driving Motor Second (DMS) | 506 | 1 | 79748 | 34 seats |
| 30215 | Trailer Second (TS) | 506 | 1 | 79749 | 48 seats |
| 30216 | Driving Motor Brake Second (DMBS) | 506 | 1 | 79750 | 28 seats |
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