British Rail Class 85

During the late 1950s, British Rail (BR) embarked upon the electrification of the West Coast Main Line, a strategy which necessitated the procurement of a large number of electric locomotives to utilise the newly-installed infrastructure. A detailed specification, listing various performance attributes for such a locomotive, was produced by the British Transport Commission.[1]

It was decided that, instead of a bulk order from a single manufacturer, several batches of similar locomotives would be ordered from several companies, the first of these being the AL1 series.[2] Further contracts were awarded, including one to BR's own Doncaster Works, to procure a similar locomotive, thus resulting in the Class 85. Under the earlier BR classification, the type was given the designation AL5 (meaning the 5th design of 25 kV AC locomotive), and locomotives were numbered E3056-E3095.[3][1]

While BR planned had intended for this procurement strategy to have led to work being spread out to a variety of different manufacturers, many of the systems used across the different prototype classes were similar or in some cases identical, having been supplied by the same firm, the Metropolitan-Vickers division of the British manufacturing group Associated Electrical Industries (AEI).[2][1] Between 1961 and 1964, a total of forty such locomotives were constructed, all of which were built at Doncaster.

The Class 82 is an AC electric locomotive intended for express services on the West Coast Main Line.[1] Its design bore considerable similarities to the earlier British Rail Class 81, particularly in terms of their shared AEI-supplied equipment. One key area of difference was its adoption of semiconductor-based rectifiers and a rheostatic braking system; the latter was viewed as likely to generate considerable cost savings in comparison to conventional braking by reducing wheel wear.[1] A small proportion of the locomotive's equipment, such as the bogies, were designed by the French industrial group Alsthom.[1]

In order to achieve the minimal weight requirement stipulated by BR, while still maintaining sufficient structural strength, the lower halves of the body sides were merged into the locomotive's underframe, while the roof and sides above the base of the windows were built from a relatively light steel frame with an aluminium covering.[1] The underframe is a welded steel assembly divided into seven box-like sections, while the bogie frame is built from rolled steel members that were welded together. On the outer faces of the underframe, the coupler and oleo-pneumatic buffers were fitted.[1] The locomotive was seated upon each bogie via a double-ended rubber cone-shaped pivot, the alignment of which was defined by a transverse spring anchorage. Much of the weight was carried by two sets of four spring-loaded side-bearers, which used rubber brushes wherever practical to eliminate the need for lubrication.[1]

The Class 85 featured a sizeable power compartment, of which particular attention was paid to making it as accessible for maintenance purposes as was realistically possible.[1] The bulk of the equipment was installed within two compartments, one containing the rectifier apparatus and the other accommodated the main transformer and associated equipment, while a walkway spanned the length of the power compartment for access purposes. Above the transformer was its roof-mounted radiator and cooling fans, while the braking resistors and motor contactor panel were positioned close by.[1] In between the transformer unit and the rear bulkhead was the brake compressor, primary air reservoir, and the fault indicator panel. On the opposite side of the power compartment, next to the forward bulkhead, was the auxiliary compressor, battery charging apparatus, and a chemical toilet for the locomotive crew.[1]

Power was delivered to the locomotive via overhead catenary, which was always energised at 25,000 V AC. However, the main transformer, which was normally operated with the four windings in series, could be operated at 6.25 kV AC with the transformer windings in parallel. This voltage was intended to be used where limited clearances gave concern over use of the higher voltage arcing onto lineside structures, especially those made of cast iron. Since the clearances were found to be adequate, the lower voltage connections were locked out of use.[4] A standardised Stone Faiveley AMBR pantograph was adopted for the type, which was raised using pressurised air, the power for which was provided via the battery-powered auxiliary air compressor.[1]

The Class 85 features a driving cab at either end of the locomotive, eliminating the need to ever turn around.[1] These cabs feature double-skin construction, the exterior being composed of sheet steel around a steel frame, while the side walls were lined with plastic-faced plywood and the roof comprised fibreglass mouldings. Asbestos was also applied for its thermal insulation and soundproofing properties; several electric heater units were also present each of the cabs.[1] The driving controls, which conformed to BR's standard conventions of the era, were mounted on a sloped plastic-covered desk directly beneath the forward window; various instruments, light switches, indicators, and gauges lined the centre console. The master controller was to the right of the driver while the air brake controls were to the left.[1]

Upon their entry to service, the AL5 fleet was used to haul express trains on the then newly electrified West Coast Main Line, from Birmingham, to Crewe, Manchester Piccadilly, Liverpool, and later Preston. By 1965, electrification had spread south to London Euston, allowing for services to be extended shortly thereafter.

The majority of the Class 85 locomotives were originally built with germanium rectifiers in their power systems, although a minority were constructed with silicon-based rectifiers instead.[3] Largely due to reliability issues experienced, all members of the class underwent a mid-life refurbishment, during which those locomotives with germanium rectifiers were replaced by the alternative silicon-base counterpart.

In 1968, the type was reclassified as the Class 85 as a result of BR's introduction of the TOPS numbering system. From 1971 onwards, locomotives were progressively renumbered into the 85001-040 series. Fifteen locomotives were converted for freight only use, numbered in the 85/1 series - see table below. These locomotives were restricted to 80 mph.

• On 13 October 1985, 85001 caught fire while hauling the 16:15 Euston to Manchester service.[5]
• On 27 April 1989, a passenger train hauled by 85 012 was derailed near Northampton.[6]

One locomotive has been preserved, 85101 (having previously numbered E3061 & 85 006) This locomotive is preserved by the AC Locomotive Group, who also have examples of Classes 81-84 and 86. at Barrow Hill Engine Shed. It was named to commemorate the 150th anniversary of Doncaster Works and is painted in Railfreight Distribution livery, a livery it never carried in service. Their intention is to eventually restore this locomotive to operational condition.[7]

• Derrick, Kevin (2014). Looking back at AC Electric Locomotives. Strathwood. ISBN 9781905276516. OCLC 931820979.
• McManus, Michael. Ultimate Allocations, British Railways Locomotives 1948 - 1968. Wirral. Michael McManus.
• "Not the Class 85!". Traction. No. 188. Warners Group Publications. June 2010. ISSN 1354-2680.

Wikimedia Commons has media related to British Rail Class 85.

• AC Locomotive Group - Owners of preserved locomotive no. 85101 / E3061
• High-Voltage A.C. Locomotives Built by British Railways, Publisher:Associated Electrical Industries Ltd.