class-28-co-bo

The BR Class 28 'Co-Bo' was a series of 20 diesel-electric locomotives of an unusual Co-Bo wheel arrangement built by Metropolitan-Vickers of Stockton-on-Tees with Crossley two-stroke diesel engines between 1958 and 1959 for the London Midland Region of British Railways. The asymmetric Co-Bo configuration — one six-wheel bogie (Co) at one end and one four-wheel bogie (Bo) at the other — was a unique choice in British diesel practice, adopted because the Crossley 2-stroke engine was heavy enough to require the additional axle of the Co bogie for weight distribution, while the shorter Bo bogie at the opposite end kept overall length and weight manageable. The result was a locomotive that looked distinctly lopsided compared with the symmetric Bo-Bo and Co-Co types that dominated BR's Modernisation Plan fleet.

The Crossley HSTVee two-stroke diesel engine proved to be the Class 28's fatal weakness: an unproven design for main-line traction work, it suffered persistent reliability problems in service on the LMR's varied mixed-traffic duties. Metropolitan-Vickers' electrical equipment was generally well regarded, and it was the Crossley engine rather than the electrical side that caused the class's poor availability record. The entire class was withdrawn between 1968 and 1969 after only a decade of service, making the Class 28 one of the shortest-lived of the Modernisation Plan diesel classes.

One example, D5705, is preserved and represents this distinctive and short-lived Co-Bo design.