British Rail Class 28

The British Rail Class 28 (Metro-Vick Type 2) 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-storke diesels built under the Pilot Scheme. The locomotives had a Co-Bo wheel arrangement (a 6-wheel bogie at one end, a 4-wheel bogie at the other) - unique in British Railways practice and uncommon in other countries, although Japan also used some C-B diesel hydraulics. The maximum tractive effort of 500,000 lbf (220 kN) was unusally high for a Type 2 locomotive but, as there were five (not four) driving axles, the risk of wheelslip was minimal.