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Dual locomotive F3 Model Bo-Bo

Dual Mode Locomotive

Dual locomotive F3 Model Bo-Bo

The railway locomotive leads a rugged existence, and only the fittest survive. Evolution has thus tended to move in moderate steps, and few successful developments have been sufficiently dramatic to merit the term "revolutionary". One such step was the pioneer four-unit freight diesel. No. 103, produced by the Electro-Motive Division of General Motors in 1939. When that unit embarked on a 83,764 mile (134,776km) demonstration tour of 20 major American railroads, few people, other than EMD's Chief Engineer Richard M. Dilworth, ever imagined that it would be possible for the country to be paying its last respects to steam only 20 years later.

Locomotive F3 Model Bo-Bo

By 1939 EMD had some six years' experience of powering high-speed passenger trains by diesel locomotives tailored to suit the customer's requirements.
Their ability to outrun the best steam locomotives had gained them acceptance in many parts of the USA, but this was a specialised activity, and even the most diesel-minded motive power officer did not regard the diesels an alternative to the ten, twelve or sixteen coupled steam locomotive for the heavy grind of freight haulage.
Dilworth had faith in the diesel, and his company shared his faith to the tune of a four-unit demonstrator weighing 912,0001b (414t) and 193ft (58,830mm) in length.

Origin: Electro-Motive Division, General Motors Corporation (EMD), USA.
Type: All-purpose diesel-electric locomotive, "A" units with cab, "B" units without.
Gauge: 4ft 8 1/ 2in (1,435mm).
Propulsion: One EMD 567B 1,500hp (1,120kW) 16-cylinder pressure-charged two-stoke Vee engine and generator supplying current to four nose-suspended traction motors geared to the axles
Weight: 230,000lb (104.4t) (minimum without train heating steam generator).
Axleload: 57,500lb (26.11).
Overall length: "A" unit 50ft 8in (15,443mm), "B" unit 50ft Oin (15,240mm).
Tractive effort: 57,500lb (256kN).
Max speed: Between 50mph (80km/h) and 120mph (192km/h) according to which of eight possible gear ratios fitted.
Service entry: 1945.

Most of the passenger diesels built so far incorporated the lightweight Winton 201 engine, which EMD had acquired, but in 1938 EMD produced its own 567 series of two-stroke Vee engines (numbered from the cubic capacity of the cylinder in cubic inches). The 16-cylinder version was rated at 1,350hp (1,010kW), and this fitted conveniently into a four-axle Bo-Bo layout, with the whole weight thus available for adhesion. Two such units were permanently coupled, an "A" unit with cab and a "B" or booster unit without; two of these pairs were coupled back-to-back by normal couplings. Multiple-unit control enabled one driver to control all four units, but they could easily be separated into pairs, or, with a little more work, into 1 plus 3. Dilworth reckoned that a 2,700hp pair was the equal of a typical steam 2-8-2 or 2-10-2, and that the full 5,400hp (4,030kW) set could equal any of the largest articulated steam locomotives. As the combined starting tractive effort of his four units was almost double that of the largest steam engine, his claim had some substance. They were geared for a maximum speed of 75mph (120km/h) but could be re-geared for 102mph (164km/h), thereby producing a true mixed- traffic locomotive.

The units were built on the "carbody" principle, that is, the bodyshell was stressed and formed part of the load-bearing structure of the locomotive. The smooth streamlined casing was in sharp contrast to the Christmas-tree appearance of most large American steam engines, festooned as they were with gadgets. But this was one of the revolutionary ideas demonstrated by No. 103. Bright liveries on the passenger stream had attracted great publicity; now there was the possibility of giving the freight locomotive a similar image. Despite the scepticism of steam locomotive engineers, 20 railroads spread over 35 states responded to EMD's invitation to give No. 103 a trial, and everywhere it went it improved on the best steam performance by a handsome margin. From sea level to 10,240ft (3,120m), from 40°F below zero (—40°C) to 115°F (46°C), the story was the same. Typical figures were an average speed of 26mph (42km/h) over 98 miles (158km) of 1-in-250 grade with 5,400t, compared with 10mph (16km/h) by a modern 4-6-6-4, or an increase in load from 3,800t with a 2-8-4 to 5,100t. The booster units were equipped with steam generators for train heating, and this enabled No. 103 to show its paces on passenger trains. The impression it made on motive power men was profound.

Not least amongst the startling qualities of No. 103 was its reliability. Throughout the 11-month tour no failure occurred, and even when allowance is made for the close attention given by accompanying EMD staff, this was a remarkable achievement. Production locomotives, designated "FT", followed closely on the heels of the demonstrator, and orders were soon received from all parts of the country. EMD's La Grange Works was tooled-up for quantity production, and over a period of six years 1,096 "FT" units were built, Santa Fe being the biggest customer with 320 units. The War Production Board was sufficiently impressed by the contribution which these locomotives could make to the war effort to allow manufacture to continue with only a short break, despite the use of scarce alloys.

By the end of the war the freight diesel was fully accepted on many railroads, and total dieselisation was already in the minds of some motive power chiefs. The first postwar development was production of the 567B engine rated at 1,500hp (1,120kW) to replace the 1,350hp 567A model. After 104 interim units designated "F2", there came a four-unit demonstrator of the "F3" model, with a larger generator to suit the 1,500hp engine, and a number of other improvements based on six year's experience with the "FTs". Amongst these were automatically-operated cooling fans; the fans fitted to the "FTs" were mechanically-driven through clutches; and had manually-worked shutters. The fireman had a frantic rush to de-clutch the fans and close the shutters when the engine was shut down, particulary in severe cold when the radiators would freeze very quickly. EMD proclaimed the "F3" as "the widest range locomotive in history", and the railroads seemed to agree, for new sales records were set with a total of 1,807 units sold in little more than two years up to 1949. Railroads took advantage of the scope which the smooth curved shape offered for imaginative colour schemes, and an EMD pamphlet showed 40 different liveries in which these locomotives had been supplied.

Simplicity of maintenance, and improvements in the engine to reduce fuel consumption, were two of EMD's claims for the "F3", and these same claims were repeated for the next model, the "F7", launched in 1949. The main change from the "F3" was in the traction motors and other electrical equipment. With the same engine power, the new motors enabled 25 per cent more load to be hauled up heavy grades. The model was offered with the usual options, including eight gear ratios. The "F7" proved to be a bestseller too; 49 US roads bought 3,681 "F7s" and 301 "FP7s", the version with train-heating boiler, whilst Canada and Mexico took 238 and 84 respectively. They handled every type of traffic from the fastest passenger trains to the heaviest freight. Measured by sales, the "F7" was the most successful carbody diesel ever. "F7" production ended in 1953, to be replaced by the "F9". The main change was the 567C engine of 1,750hp (1,305kW). By time the US market for carbody diesels was drying up, as "hood" units gained popularity, and only 175 "F9s" were buit over a period of three years.

By the 1960s steam had been replaced totally, and manufacturers were now selling diesels to replace diesels. Trading-in old models became popular, and bogies in particular could be re-used. Many "Fs" were replaced in this way as the more powerful hood units became increasingly popular, and the decline of passenger traffic helped the process. Never some units of the "F" series were still to be found at work in 1984, and the Canadian locomotives, in particular, could still be seen on passenger trains.
The "F" series, more than any other model, showed, showed that improvements in performance and economies in operation could be achieved in all types of traffic by dieselisation, despite uncertainties about the life which could be expected from a diesel locomotive.

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