British Rail Class 28
The British Rail Class 28 diesel locomotives, known variously as 'Metrovicks', 'Crossleys' or 'Co-Bos', were built under the Pilot Scheme for diesel locomotives as part of the British Railways 1955 Modernisation Plan.
These Crossley-engined locomotives were the only two-stroke diesels built under the Pilot Scheme.
The locomotives had a Co-Bo wheel arrangement – unique in British Railways practice and uncommon in other countries, although Japan also used some C-B diesel hydraulics. The maximum tractive effort of was unusually high for a Type 2 locomotive but, as there were five driving axles, the risk of wheelslip was minimal.
Origin
Work had begun on the Pilot Scheme in 1954 and the first plan for 174 locomotives had been produced by October 1954, including 20 of these Metro-Vick Type B locos, although orders were not placed until November 1955. In July 1956 the Type A, B and C designations were changed to Types 1, 2 and 4, making this a Type 2.The two-stroke engine was chosen as a comparison to the more common four-stroke engines used, and partly as a result of the influence of Oliver Bulleid. The leading manufacturer of such two-stroke locomotive engines was General Motors, but the national shortage of foreign exchange meant that imported engines were unaffordable. Crossley in Manchester had a suitable design in production as a generator set for the Admiralty and had also used it for a class of locomotives in Australia. Bulleid had left British railways and moved to Ireland and the CIÉ. He had beem impressed by the Admiralty's experience of the Crossley diesel and he had already ordered 60 similar locomotives as the CIÉ's 001 class.
Engine
With low-speed Crossley 8-cylinder HST V8 two stroke engines, they represented an experiment in two stroke versus four stroke engines for diesel-electric traction.The engines had exhaust pulse pressure charging and developed 1,200 horsepower at 625 rpm. There were no valves, and inlet and exhaust were via ports in the cylinder walls. The same engine was originally fitted in the Irish A Class and the Western Australian Government Railways X class. A similar, but smaller engine, the ESNT6 was used in the D3/3 shunters, an 08 with a Crossley engine rather than English-Electric.
Almost from the beginning the Metrovick's Crossley engines were problematic. They suffered frequent failures and by 1961 the entire class was handed back to the manufacturer for remedial work on the engines and to cure problems with cab windows falling out while running. The cab windows were modified such that instead of wrapping round to the side the outer front windows were replaced by a flat piece of glass facing the front only.
The engines were also noisy and prone to unacceptable levels of smoky exhaust fumes.
Statistics
Total weight in working order was 97 long tons, distributed as shown in the table below. The units are tons, hundredweights and quarters.Operation
All twenty Metrovicks were initially allocated to the Midland Division of BR's London Midland Region, where they were often used in pairs on the overnight London–Glasgow "Condor" express freight service. After the 1961 refurbishment they were all transferred to the Barrow-in-Furness 12E depot. They were withdrawn after only eleven years at work and in service. The allocation of all twenty locomotives in October 1967 was Carlisle Upperby.Despite the locomotives being otherwise reliable the Crossley engines were still giving problems and British Rail considered replacing the engines, as was done with the Class 31 diesels and, later, with Crossley-engined locomotives in Ireland. Instead the entire class was withdrawn from service during 1967–68, and all but one were scrapped by the end of 1969. Their parts had been sold to make new metals by the end of 1971.
| Year | Quantity in service at start of year | Quantity withdrawn | Locomotive numbers | Notes |
| 1967 | 20 | 6 | D5700/03-4/09-10/13 | |
| 1968 | 14 | 14 | D5701-2/05-8/11-12/14-19 | D5705 went into departmental use |