The British Rail Class 310 was a slam-door, alternating current (AC) electric multiple unit (EMU) introduced in 1965 as part of the West Coast Main Line electrification project. They were initially classified as Class AM10 units before the introduction of the TOPS classification system. Constructed at BR's Derby Carriage and Wagon Works. They consisted of four carriages - a second class driving trailer, a second class trailer, a second class motor car (with guard's/luggage compartment above which the Stone Faiveley AMBR pantograph was mounted) and a composite (1st and 2nd class) driving trailer. The maximum speed was . A glass partition behind the driver's cab enabled passengers in the leading and rear coaches to view the line ahead or behind.
History
They introduced some new features; the first standard multiple units with disc brakes (emergency stop from top speed in 33 seconds over ); the first naturally air-cooled rectifiers (silicon diodes on cups of beryllium oxide), inductors and transformers. Noise was reduced by sprayed asbestos on the floor, body and roof.
Original livery was overall Rail Blue, later amended to the standard BR blue and grey colour scheme.
Initially they were primarily used on local services from London Euston to Bletchley, Milton Keynes, Northampton and Birmingham New Street, and within the West Midlands. They were also the first EMUs to be based on the British Rail Mark 2 bodyshell, which featured semi-integral construction.
During the mid-1980s they underwent their heavy C1 refurbishment at Wolverton which included new flat windscreens, a corridor connection between the Motor Vehicle (MBS) and trailer (TSO), and a PA system among other modifications.
The Class 310 has a nearly identical body shell to that of the Class 312, there are some minor detail differences in the equipment locations and the MBS has a separate guards van and storage area whereas on the 312 it is combined. The braking system is slightly different with ventilated brake discs on the axles of the B4 non-powered bogies attached to the axles whereas on the Class 312 they are mounted on the wheel discs (this permits easy replacement in the case of defects). As are the motor bogies axles on the Class 310. When first arriving on the LT&S the Class 310 were modified with an additional plug being inserted in the dummy cylinder of each vehicle and a different size "choke" fitted in the Electro-pneumatic (EP)valve to improve the braking performance to that required on a more intensive service. Also the cast BR double arrows were removed from the cab sides on arrival, or soon after at East Ham Depot. The Class 310 stock also were used for a short while on the newly electrified route to Cambridge prior to replacement with more modern stock.
The motors differed from the class 312 in that the gear ratio is lower which accounts for the maximum speed of compared to on the Class 312. The B4 bogies on the Class 310 are fitted with friction primary dampers whereas on the 312 they are hydraulic.
The main fleet of Class 310/0 units was replaced on the Euston commuter routes with Class 317/1 units which began to enter service on the route in late 1987, however the Class 317 units were then superseded by the new build of Class 321/4 within about 2 years.
Most Class 310 units that survived into the 21st century were withdrawn between 2001 and 2002.
Sub-classes
310/0 - four-car units. All 310s were originally 310/0s. 310/1 - Four-car units (reduced to three-cars in the mid-1990s) modified for use in the Midlands.