Steve Hoather

4ft 8½in and all that

When the first of the main line diesel locos were produced under British Railways’ modernisation plan, the most powerful engines available were of 2000 HP from English Electric and 2300 HP from Sulzer, the latter being increased after the first few locos to 2500 HP. In both cases the bodies were of the 1-CO CO-1 wheel arrangement, giving an overall weight of over 130 tons. Experience showed that these were unable to improve on the timings of steam trains, so BR let it be known that it was looking for a new design of about 2700 HP with a CO-CO wheel arrangement and an overall weight of about 114 tons. The main sponsor for this new design seems to have been the Eastern Region, since the Western was still wedded to diesel hydraulics, and the London Midland was electrifying their main trunk route.

The size of the British locomotive industry was such that it was possible for three separate consortia to produce different designs. All three produced single prototypes, and all three ran on the East Coast Main Line, and since my layout is based on the ECML, they were obvious candidates to model.

The first prototype to enter service in October 1961 was Falcon from Brush, which had two Maybach engines made under licence by another member of the Hawker Siddeley group, giving 2800 HP, finished in a striking livery of lime green and brown. Unfortunately BR had already seen enough of these engines in Western Region diesel them on diesel electrics. In 1965 the loco was transferred to the WR, where it stayed until it was withdrawn in 1975. Next to appear, in May 1962, was Lion , built by BRCW with a Sulzer engine of 2750 HP and AEI electrical equipment. This loco was in an eye catching white livery, but by January 1964 BRCW had decided to withdraw from the locomotive business and the loco was broken up. Also in May 1962, English Electric’s DP 2 appeared. Rated at 2700 HP, it had a single EE engine in a modified Deltic body. The loco remained in service hydraulics to decide they did not want until July 1967 when it was badly damaged in a collision with a derailed cement train at Thirsk.

An end view of the three prototypes described in the article

Ironically, none of the 3 prototypes was selected as the standard BR type 4. The standard design (Brush Type 4) was a combination of a shortened Falcon body, Sulzer 2750 HP engine, and Brush electrical equipment as used on the later class 46 locos. After a few years in service, however, the engines started developing serious crankcase fractures, and had to be modified and derated. When BR needed a final batch of 50 locos to eliminate steam, they turned to English Electric, whose class 50 design was an updated DP2. They, however, seemed to be even more problematic than the Brush 4s, but that is another story…

The Models

The bodies of all three models are made from Plastikard mounted on a wooden former to give adequate strength. I have used this technique before, notably on a class 47 which is now 49 years old and still going strong (see Model Railway Constructor, October 1967) and the prototype Deltic described in the May 1996 Gazette. I had originally intended to use a PRMRP etched brass Deltic kit for DP2, but when I checked the drawings I found the bodyside windows were in different positions, as well as the roof being different, so this was not practical.

Falcon and Lion have straight sided bodies, so I used 0.060in Plastikard glued on to 1/8 in hardwood. The roof is a length of wood planed to the correct profile (particularly difficult on Lion which has a raised centre section along its length), overlaid with 0.020in Plastikard on which all the detail is built. The wood is between the cab doors only, the nose ends (body and roof) being entirely Plastikard, with the large radius curves at the corners being made by filling in the inside of the corner, waiting a week or so for the solvent to dry, and then sanding to profile.

Photo 1

Photo 2 - Falcon cab body and roof

Photo 3

Photos 1, 2 and 3 show various stages in building Falcon’s cab. Below the waist I used 0.080in, but the windows above the waist are only 0.002in but with suitable Plastikard reinforcement set back from the edges of the windows to give sufficient strength. On these two locos, the bogie pivot support bars are fixed to the hardwood, and the buffer beams are tied back to this support bar, so that the Plastikard is not load bearing. The locos are weighted with lead in the battery boxes to give a weight of about 2kg.

DP2 was a much more difficult proposition. Not only are the bodysides curved in profile, but the long nose at the end means that the bogie pivots had to be outside the area reinforced with wood. I therefore made a steel and brass subframe to support the bogie pivots and buffer beams.

Photo 4

Photos 4 to 10 show the main stages in construction of the body, much more clearly than I could describe in words.

Photo 5

Photo 6

Picture 8 shows how I curved the side windows by clamping them between two sheets of copper and immersing in hot water – if you do not pre-form the curves, they will tend to straighten out over time.

Photo 7

The bogies on all three locos are different. Lion has a unique design, so I had to cut the main frames out of brass and solder brass flanges on the top and bottom. The equalising beams and axleboxes were diecast from a pattern I made.

Photo 8

As the frames are brass, I made them load bearing, unlike the other two locos which have whitemetal sideframes and an internal brass frame between the backs of the wheels to carry the load. Falcon’s sideframes are PRMRP class 31, with one half suitably lengthened to give the correct wheelbase as they are asymmetric, and DP2’s sideframes are PRMRP class 37/55.

Photo 9

You will see from photo 10 that the bogie pivot is midway between the leading and middle axles, to reduce overhang on curves and hence lessen the risk of buffer locking. The ABC diesel motor unit is mounted on the inner axle on each bogie, with a chain drive to the outer axle, which is compensated. The middle axles are lightly sprung and not driven. Although I originally fitted flywheels, I have since removed these as the built in ‘stay alive’ capacitor on the ESU V4 XL decoder combined with flywheels was too effective and caused the loco to overshoot too far when one of my drivers had a SPAD! One motor bogie on each loco would probably have been sufficient, except that it was difficult to get enough weight at one end to haul 12 coaches up my 1 in 50 gradients.

Photo 10

All three locos have ESU XL sound decoders with 40mm speakers. The decoders were specially programmed by Howes Models and Bryan Robertson to give what I guess is a realistic sound – class 47 with class 33 horn for Lion, class 52 for Falcon, and class 50 with class 37 horn for DP2. The tail lights are 3mm LEDs and wired directionally, so are a useful way of knowing which direction is set. The four figure train describer panels are tinplate with Fox transfers, made from the bottom of tin cans, and retained by small magnets inside the cab so they are removable.

Photo 11 - Four prototypes. From left to right, Falcon, DP2, Lion and Deltic