British Rail Class 37/9

The British Rail Class 37/9 was a sub-class of the
British Rail Class 37 diesel locomotive. In 1986 Class 37s numbers 150/148/249/124, were converted to test the Mirrlees MB275T diesel engine and Brush alternator for the proposed Class 38, and were numbered 37901-4. These were followed in 1987 by 37905/6, converted from 37136/206, and fitted with the alternative pairing of a Ruston RK270T diesel engine and GEC alternator. All six locomotives were fitted with new bogies, and had ballast weights to increase their overall weight to 120 tons. Although intended as a testbed for the Class 38, the two power units fitted were those considered for the British Rail Class 60, which was eventually delivered with an enlarged version of the Mirrlees MB275T engine.

All six Class 37/9s were delivered in Railfreight Grey livery and operated as part of the British Rail Heavy Metals sector, being based in South Wales and hauling trains normally rostered for the much more powerful British Rail Class 56 such as the Port Talbot Steelworks - Llanwern iron ore tipplers. During the late 1990s use of the Class 37/9s declined due to availability of the newer and more powerful British Rail Class 66s and problems maintaining such a small number of non-standard locos, with all six officially designated as being in storage in 1999.

This was not, however, the end of the sub-class. In July 2000 37906 was designated as part of the EWS heritage fleet but has since been sold into preservation, joining 37901 and 37905; 37902 was sold to Direct Rail Services (DRS) in 2003, but was scrapped and cut up in 2005 after a review by DRS. 37904 was cut up at Booths in Rotherham in November 2004 and 37903 was scrapped at Crewe Diesel TMD in April 2005.