(as printed in The Railway Magazine, January 1959)
Twenty 1,200-h.p. mixed-traffic diesel-electric locomotives, Nos. D5700-D5719, are being supplied by Metropolitan-Vickers Electrical Co. Ltd. to the London Midland Region of British Railways. All are being allocated to Derby and will be used on passenger and freight trains in the Midland Division.
Principal dimensions and particulars are as follows :-
|Total weight in working order||97 tons|
|Length overall||56 ft. 7 1/2 in.|
|Total wheelbase||42 ft. 7 in.|
|Bogie wheelbase (Co)||12 ft. 1 1/2 in|
|Bogie wheelbase (Bo)||8 ft. 6 in.|
|Distance between pivot centres||32 ft. 4 in.|
|Width overall||9 ft. 2 1/2 in.|
|Height overall||12 ft. 8 3/8 in.|
|Wheel diameter||3 ft. 3 1/2 in.|
|Maximum tractive effort||50,000 lb.|
|Continuous tractive effort||25,000 lb.|
|Maximum service speed||75 m.p.h.|
|Minimum curve radius||3 1/2 ch.|
|Fuel oil capacity (engine and boiler)||510 gal.|
|Water capacity (for boiler||600 gal.|
|Steam heating boiler capacity||1,500 lb. per hr|
The mechanical parts are being manufactured by Metropolitan-Vickers/Beyer Peacock Limited, and the electrical equipment by Metropolitan-Vickers Electrical Co. Ltd. The locomotives are being fitted with Crossley Vee-8 engines; this is the only conventional engine of the two-stroke type being supplied to British Railways for mixed-traffic locomotives, and it will provide a basis for comparing two-stroke and four-stroke cycle types.
There is a full-width body and driving cab at each end. The driving position is on the left-hand side of each cab. Up to three locomotives can he driven in multiple. Also multiple-unit operation of these locomotives with others now being delivered under the modernisation scheme and fitted with electrical equipment by the General Electric Co. Ltd. and Brush Traction Limited has been arranged by co-operation between the three companies.
The main driving controls are the master controller and the brake valves. Instruments comprise a main generator ammeter and engine tachometer, brake gauges and speedometer. Three indicator lights, "engine stopped", " wheelslip" and alarm" follow the standard system introduced in locomotives being supplied to British Railways. Each lamp is normaly dim, and comes up to full brilliance under fault conditions. The intensity of illumination of these lamps under dim conditions, and also the intensity of the instrument lights, can be adjusted by individual variable resistances to suit the driver's requirements under all conditions between brilliant sunshine and total darkness.
Electric cab heating is by tubular heaters, and there is also a foot warmer at both driver's and assistant's positions. Demisters are provided for the outer front windows, using heated air fed from the traction motor cooling system. The cab roofs, and the cab bulkhead at the engine end, are lined to provide heat and sound insulation.
The underframe, carlines, cantrail, floor and body sheeting form a complete welded structure designed to give maximum strength with minimum material. The underframe is made up largely of folded plate sections welded to form continuous longitudinal and transverse members with diagonal bracing, the transverse members being positioned at the load carrying points. A special feature is the incorporation of the main fuel and boiler water tanks with the underframe top and bottom plating. In sections not used for tankage the traction motor air ducts are also built in.
Besides the side buffers and centre screw coupling fitted initially, provision is made for the replacement of these items by a central automatic coupler at some future date. Among the special provisions for lifting and jacking of the locomotive in the event of derailment is the facility for using a single rocking jack at the centre of the underframe.
The body is divided by transverse bulkheads into four main compartments, namely, two driving cabs, an engine and radiator compartment, and a generator and boiler compartment; the upper portion of the bulkhead between the latter two compartments is removable.
Louvres are provided at the various air intake positions, and where access is necessary these take the form of doors. Sections of the roof are easily detachable for removal of the power unit, boiler, and auxiliary machines, while a number of smaller panels are provided for access to engine cylinder heads, fuel pumps and boiler fire compartment roof.
Entrance doors are arranged on the assistant's side of each cab and, near to the cab bulkheads, on the opposite side in the engine and generator compartments. End doors conceal the flexible gangway connection used when locomotives are operating in multiple. The engine room floor is arranged so that any spillage of fuel oil or water drains into a tank beneath the underframe, which can be emptied from time to time.
The diesel engine is a two-cycle type with eight cylinders in Vee formation, continuously rated at 1,200 h.p. at 625 r.p.m. The one-hr. rating is 1,320 h.p. at the same speed. Safety devices ensure that the engine is automatically shut down in the event of overspeed, low lubricating oil pressure, low engine cooling water pressure, or high engine cooling water temperature. Twin outlets are provided for the exhaust gases, the positions being chosen such that contamination of overhead contact wiring is avoided.
The main and auxiliary generators, both direct current machines, are of integral construction, with the frame flange-mounted on the end of the engine, and the armatures are mounted on a common hollow shaft, which is solid coupled to the engine crankshaft at one end and carried on a single roller bearing at the other.
Each of the five axles is fitted with a nose-suspended axle-hung traction motor; all five motors are connected permanently in parallel. The drive to the axle is through totally-endosed single-reduction spur tooth gears with a ratio of 15 : 67 ; the gearwheel provides for torsional resilience between hub and rim.
Ten notches are provided in the master controller to control the engine speed and power. Automatic control of generator and motor field strengths ensures that the engine power selected shall be available over a wide range of locomotive speeds. This is achieved by the use of a servo-mechanism which functions in response to a signal from a hydraulic pilot valve associated with the diesel engine governor to control the electrical output of the traction generator. Hence the total power is maintained at a constant value, irrespective of changing track speeds and load conditions.
Most of the control equipment is housed in a cubicle adjacent to the driving cab at the generator end of the locomotive. The main items are the load regulator, electropneumatically-operated contactors and reverser, auxiliary switches, relays and resistors. Deadman equipment is also fitted.
Auxiliary equipment includes the auxiliary generator, on the end of the main generator; an air compressor, driven by engine, to supply compressed air at 100 lb. per sq. in. for locomotive brakes, electropneumatic control gear, sanding, whistles and window wipers; two vacuum exhausters, driven by electric motor, for train brakes; three fans, driven by electric motors, for force ventilating the generator and traction motors; engine ancillary equipment, comprising motor-driven pumps, and radiator panels with motor-driven pumps, and radiator panels with motor-driven fan; a battery for starting the diesel engine, using the main generator as a motor; and the train heating boiler, for steam heating passenger coaches. Provision is made for a.t.c. equipment to be installed later.