Class 125 Derby 3-car DMUs

Description

These three-car DMUs were formed of two power cars and an unpowered centre car. One power car contained a Guard's van on the inner end. The vehicles were of the high density / suburban type, with a passenger door at each seating bay, there was only second class accomodation, and the vehicles were not gangwayed.

Underframe equipment aside, the power cars were almost visually identical to the second and third batches of Class 116s — with two marker lamps and a two-digit route indicator. The differences were:

• The train vacuum pipes hung vertically down at the front of 125s as opposed to projecting forward on 116s (there were however two exceptions to this in the form of 50988 and 51154).
• Two windscreen wipers were fitted from new on each driving car of a 125. as opposed to just one on a 116. Later, the 116s were fitted with a second on each cab.
• Only one inter-vehicle jumper cable was fitted to a 125, on the opposite side to that of the two fitted to 116s.
• The Orange Star coupling code symbol, rather than the more commin Blue Square, was displayed on the extreme lower corners of each cab front.

The image shows the inner end of DMS 50992, seen after withdrawl at Derby Litchurch Lane on 14 November 1980.

The trailers were also very similar to those of the 116s, with little to identify them from other suburban types, except the positions of the interior bulkheads which dictated slightly different bulkhead window positions (two small instead of a large). All DMU suburban trailers, though basically very similar, had slightly different bulkhead window positions between each class. These Class 125 centre cars had four full width bulkheads splitting the passenger accomodation into five separate sections, originally two non-smoking and three smoking.

Interior walls were formica covered in a pattern identical to that used on the Ayrshire Class 126s. Bulkhead walls appear to be plain coloured, and window surrounds were a dark varnished wood.

While built with round buffers, some did receive oval ones later on.

Power Train

Each power car was fitted with two Rolls-Royce series 823 Type C8-NFLH engines. These 8-cylinder, 16.2 litre, horizontal power units would produce 238hp at 1,880rpm, and were fitted with a CAV type N fuel pump. Transmission was through a Rolls-Royce three stage torque converter, connecting to a reversing final drive gear on the inner axle of the closest bogie. Number one engine, on the driver's side of a power car, would drive the front bogie, number two engine on the opposite side would drive the rear bogie.

Control System

The Class 125s were the only DMUs with the Orange Star coupling code, defined by their control system which used air pressure throughout for handling engine speed rather than an electrical pneumatic system as on other DMUs. The reduction in electrical circuits allowed a single jumper cable instead of two on each vehicle corner.

The control equipment was supplied by Westinghouse, their manual for these items is illustrated — download (18.1mb PDF).