It’s time for a PEP talk
The future shape of the British Rail suburban electric multiple unit fleet arrived 40 years ago in the form of the prototype PEP units. Simon Bendall tells the story of the three units that would influence a generation of EMUs, both on the Southern Region and beyond.
BY the mid-1960s, British Rail had begun work on preliminary designs for a new high-density electric multiple unit, this being intended as a next generation replacement for the increasingly elderly fleet of suburban units then in use. To test the proposed concepts, including the use of power-operated sliding doors, a full-size wooden mock-up was constructed at Doncaster Works, this being subjected to peak-hour loading and unloading tests alongside a slam-door vehicle for comparison. With these successfully completed, the spring of 1968 saw the construction of three prototype EMUs authorised in order to evaluate the design in everyday use.
Built at BREL’s York Works, these took the form of two four-car units and one two-car set, numbered 4001/2 and 2001 respectively. Initially given the TOPS classification of Class 461 (driving vehicles) and Class 462 (intermediate vehicles), this was later amended to Class 445 (four-car) and Class 446 (two-car) but were more often simply known by the Southern type code of PEPs (Prototype Electro Pneumatic).
First to arrive at Wimbledon in July 1971 to commence technical trials was 4001 with 4002 following in November and 2001 in June 1972, the latter having been held at Derby for type testing. While the two four-car sets were finished in standard BR rail blue, 2001 was unusually left in unpainted aluminium, complete with red BR arrows, to test the durability of the finish. Subsequent reformations (see table) would later bring mixed sets of both colours. Besides their striking modern appearance, the three PEPs were a world away in many other respects from the Mk.
1-based, and earlier, classes that surrounded them. Apart from the integrally constructed bodies with aluminium cladding, all axles of all cars were powered with English Electric-AEI 100hp traction motors to give rapid acceleration to the maximum speed of 75mph. Other technical aspects included the provision of rheostatic brakes in addition to the normal electro-pneumatic system along with automatic Scharfenberg couplings at the cab ends. Different bogies were used under 4001/2 and 2001, the latter’s featuring air suspension and recognisable as the forerunner of the types that would later be used under a host of multiple unit designs. 4001 was also delivered with a primitive and ultimately unsuccessful air-conditioning system, its sealed windows having to be replaced with revised versions featuring conventional sliding ventilators before seeing passenger use.
Strange sliding doors
Externally, the driving cars featured two sets of passenger sliding doors per side with the intermediates having three sets. Notably, the sliding doors required an initial pull by a passenger before the power mechanism would kick in and do the rest. This somewhat alien concept to passengers used to simple slam doors required the Southern Region to distribute an instruction leaflet as part of its promotional material for the trains. The PEPs were also revolutionary internally, though not in a good way, with 2+2 low-backed seating with little in the way of cushions and widespread use of what is now termed airline seating. The provision of three doors also impacted on the amount of seating that could be installed with the PEPs having less seats than a comparable slam door EMU. So spartan were the interiors that they were likened to London Underground stock, an impression not helped by the sprung grab handles hanging from the ceilings or the amount of standing room. This eventually gave rise to the alternative meaning of PEP among commuters of ‘pack 'em perpendicular‘ while questions were asked by MPs in the House of Commons in the autumn of 1973 as to how such a ‘design’ could be permitted. Emergency doors were provided in the cab fronts to allow egress in tunnels, a clear pointer that the design was also intended for use away from the Southern
With extensive testing on the Alton line completed, the PEPs had finally been unleashed on the public from June 1973, working from Waterloo on inner suburban turns to Hampton Court, Shepperton and Chessington South. Between August and September of the same year, the entire 10-car formation was trialled on services from Charing Cross and Cannon Street to Dartford, Bromley North and Sevenoaks but a series of failures, and the resultant difficulties in rescuing the Scharfenberg-equipped units, saw them unceremoniously returned to the South Western. During their time in passenger service, numerous surveys were undertaken to assess reactions to the sets, this leading to the adoption of partial 2+3 seating and the reduction to two doors per side on the production versions of the PEPs, these taking the form of the Class 313/314/315 and Class 507/508 family of units. Unfortunately for passengers, the criticisms of the low-back seating were not acted on to any great degree.
Overhead electric conversion
The first unit to be removed from passenger service was two-car 2001, this being despatched to York Works in August 1974 for conversion into a 25kV ac unit by the addition of a new purpose-built pantograph coach, ADB975431. This was styled in the same manner as the PEPs but with only two doors per side. In this three-car departmental form, with new set number 920001, the unit was trialled on the Great Eastern during the second half of 1975 and then on the London, Tilbury & Southend line early in 1976. Between March and August 1976, the set was tested on the Glasgow suburban network, this being repeated in late 1977. Subsequently stored at Derby, it was sent for scrap in 1987.
The four-car sets 4001 & 4002 continued in passenger use until early 1977, although this had become increasingly sporadic in the run up to this date, and were withdrawn that May. They also passed into departmental stock for use as test units, officially becoming Class 935s Nos. 056 & 057 respectively. 4001 saw little use in its new role, being stored at Wimbledon and then Derby St. Mary’s Yard, before disposal in 1986. 4002 fared somewhat better, seeing use as a bogie and traction equipment development unit working off Strawberry Hill and Wimbledon between 1979-81, prior to which it gained a unique livery that was seemingly inspired by the APT-P. Subsequently stored at Clapham Junction for much of the 1980s, it would not be scrapped until November 1990.
The author would like to thank John Atkinson for his assistance with this article.
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