60040 at Barnetby on 6M00 Humber to Kingsbury loaded Bogie Tanks 27th February 2013

The British Rail Class 60 is a class of Co-Co heavy freight diesel-electric locomotives built by Brush Traction. They are nicknamed Tugs by Rail Enthusiasts.
In the 1980s, British Rail decided it had a requirement for a high powered Type 5 diesel locomotive for use on its Trainload Freight sector. On 10 August 1987, the British Railways Board issued a competitive tender for response by 7 November, for a fleet of 100 locomotives. Of the six companies invited to tender,[citation needed] only three bid responses were received:

Metro-Cammell - offered a MetroCammell body with an option of traction packages, many untried, and could not offer performance guarantees as stipulated by the tender
GEC - a partnership with General Motors Electro Motive. They offered a state-of-the-art Class 59, built in the UK, probably at BREL Crewe Works, which had an existing partnership for construction of the Class 91 electric locos
Brush Traction - offered a locomotive powered by either a Mirrlees or Ruston engine, and used separately excited (Sepex) traction control, as previously tested on the Class 58.

Of the three bidders, Brush was selected, and an order was placed for 100 locomotives in a deal worth around £120 million.

Brush sub-contracted parts construction, with final construction at Brush's erecting shops at Loughborough. The bodyshells, shared with the Class 92 electric locomotives, were fabricated by Procor (UK) of Wakefield. The engine was a higher-powered development of the Mirrlees engine previously fitted experimentally to British Rail Class 37 nos. 37901-37904.

The first locomotive was delivered in June 1989 and sent to Derby for testing, which revealed a number of teething problems. Parts requiring modifications included the axle box suspension and the Mirlees engine cylinder head.
Unlike the Classes 59 and 66 (solid girder underframe) the Class 60s have a monocoque stressed skin construction with diagonal trusses - with the external bodywork providing support for the internal components.

Two different cab designs were considered and full size mock-ups were made in wood, plastic and metal by the Engineering Development Unit at the Railway Technical Centre in Derby. One of these had a French-style raked-forward cab end, similar to the SNCF Class CC 72000, but this was rejected in favour of a more conventional cab.
The main alternator is a Brush BA1006A type, providing power for the traction motors via rectification circuits to DC, the auxiliary alternator is Brush BAA 702A Auxiliary Alternator, providing power for the radiator fans, lubrication and fuel oil pumps, traction motor cooling fans and air compressors amongst others. The main and auxiliary alternators are both driven by the main engine.

Each of the six axles are driven via a reduction gear by one nose suspended axle hung traction motor (Brush designed and built TM2161A four pole motors). Each motor has a separate microprocessor-controlled power supply (SEPEX in Brush's designation - from "Separately Excited"), a system that was first tried on the Class 58. One feature of this system is that if one set of wheels/axle/motor starts to wheelslip their speed can be reduced without affecting the other motors.
The engine is an 8-cylinder, 145 litre Mirrlees Blackstone 8MB275T diesel traction engine (275 mm cylinder diameter) the Mirrlees engine was one of the most fuel efficient available at the time (189g of fuel per kWhr), but relatively heavy. The engine was also successfully installed in marine applications such as small ships and passenger ferries. The low cylinder count for the rated power was expected to result in lower maintenance costs.