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GWR railcars
GWR railcars
	AEC railcar No. 27 at Tenbury Wells station in 1949
In service	1934–1962
Manufacturer	Park Royal; Gloucester RCW; Swindon Works
Replaced	Steam locomotives and carriages
Constructed	1934–1942
Entered service	1934
Scrapped	1954–1962
Number built	38 cars
Number preserved	3 cars
Number scrapped	35 cars
Successor	British Rail Class 121; British Rail Class 122
Fleet numbers	1–38
Capacity	44–70 seats
Operators	Great Western Railway; British Railways
Lines served	Western Region
Specifications
Maximum speed	63 mph (101 km/h) to; 80 mph (130 km/h)
HVAC	steam heating
Track gauge	4 ft 8+1⁄2 in (1,435 mm) standard gauge

In 1933, the Great Western Railway introduced the first of what was to become a successful series of diesel railcars, which survived in regular use into the 1960s, when they were replaced with the new British Rail "first generation" type diesel multiple units.

Design

Bodywork

The original design featured streamlined bodywork, which was very much the fashion at the time. The rounded lines of the first examples built led to their nickname: "flying banana". The preserved W4W is an example of the original, rounded body shape. Later "razor edge" examples, such as No. 27 (pictured), had much more angular (and practical) bodywork, yet the nickname persisted for these too.

Heating

The interiors of railcars No. 1 to No. 18 were heated by using waste heat from the engine cooling water. This system proved unreliable in service due to issues with the thermostatic valves employed. Later vehicles from No. 19 onward abandoned this system due to its unreliability and because their revised specification demanded that they be able to haul steam-heated rolling stock.^[1]

These later vehicles, No. 19 onwards, were equipped with steam heating systems which were capable of heating both the vehicle's interior and that of any additional trailed vehicles, via a steam supply to the standard steam heating equipment. Steam was produced by a fully automatic Vapor Clarkson steam generator manufactured by Gresham and Craven Ltd under licence from the Vapor car co. The generator was of the water tube with counterflow arrangement type, and could supply up to 300 lb of steam per hour, at 45 lb per square inch. The quantity of steam supplied could be varied by the driver to suit the demand required by a solo railcar, or plus one, or plus two, trailer vehicles. The fuel was the same diesel as was used by the railcar's engines, drawn from a separate 45-gallon tank. The water supply for the heating system was a single 100-gallon tank.^[1]

Powertrain

Railcars No. 1 to No. 18 were powered by a high-speed diesel engine manufactured by A.E.C, producing a maximum brake power output of 130 hp (97 kW). The engine was of the straight 6 configuration, with a bore of 115 mm diameter and a stroke of 142 mm. This gave a total displacement of 8.85 litres. The maximum operating speed was 1,800 rpm.^[1]

Railcars No. 19 onwards were powered by a modified version of the previous engine. This engine was equipped with direct injection and the bore diameter was enlarged to 120 mm, the stroke remaining at 142 mm. This engine produced a lower brake power output of 105 hp at 1,650 rpm.^[1]

An unusual feature was the external cardan shaft drive from the gearbox on the rear of a horizontally mounted engine to road-vehicle style reduction boxes outboard of the two axles on one bogie. Later units had two such engine-and-drive combinations placed on opposite sides. Railcars 19–20 were fitted with a separate high-low ratio gearbox on the final drive side of the gearbox, which allowed a top speed of about 60–70 mph (97–113 km/h) in high and about 40–45 mph (64–72 km/h) in low. Railcar W20W retains this in preservation.

Brakes

The brake system on railcars No. 2, 3 and 4 was unconventional. Instead of the usual vacuum-actuated tread brakes used on most British rolling stock of the period, an automotive-style system was adopted, utilising vacuum-hydraulically actuated drum brakes. A vacuum brake cylinder and hydraulic master cylinder set was mounted on each bogie. From the master cylinder, hydraulic fluid passed through hoses to the operating cylinders. The operating cylinders actuated cam mechanisms within the brake drums to apply the internally expanding brake shoes to the inside circumference of the drums. The 20 inch internal diameter cast steel brake drums were bolted to the inside face of one wheel per axle.

The vacuum necessary for brake operation was created by three rotary exhausters, two being driven directly from the engines (one by each engine). The third exhauster was chain-driven by the final drive shaft. This arrangement allowed vacuum to be maintained during coasting, when the engines would be shut down. The system operated at a vacuum of 22 to 24 inches of mercury, stored in four reservoirs on the chassis. Another unusual aspect to this system was that vacuum was increased in the vacuum brake cylinder to apply the brakes,^[1] this being contrary to normal British railway practice, in which the vacuum is reduced to apply the brakes.^[2]

Operational history

The prototype unit, No. 1, made its first run on 1 December 1933 between London Paddington and Reading with a large number of press representatives. Three days later this unit entered public service between Slough, Windsor and Didcot.^[3]

Soon after this, the GWR ordered the next three production units, Nos. 2 to 4, which were built with two engines (instead of one) which allowed them to reach a maximum speed of 80 mph (130 km/h), and included a buffet. These units were delivered in July 1934 and entered service on 15 July 1934 between Birmingham Snow Hill and Cardiff General. This was the first long-distance diesel express service in Britain, and covered the 117.5 miles (189.1 km) miles between Birmingham and Cardiff in 2 hours 20 minutes. This was intended as a businessman's service; fares were charged at the normal rate, although bookings were limited by the 44 seats of the railcar.^[3]

The next three units, Nos. 5 to 7, entered service in July 1935 and had 70 seats. They were used on services between London, Oxford and Hereford. The next batches of railcars numbered 8 to 34 were of various designs and entered service in batches between 1936 and 1941. Two of these (17 and 34) were designed for express parcels services rather than passenger services.^[4]^[5]

The earlier units operated as single railcars. The final four, numbered 35 to 38, were twin coupled units with the driving cabs at the outer ends of the set, and were the forerunners of today's diesel multiple units. These had the capacity for 104 passengers, and a standard corridor coach could be installed between the two cars to increase the seating capacity to 184. These were introduced in November 1941 and worked the Birmingham-Cardiff service.^[5]

Fleet list

Number Range	Introduced	Builder	Engine	Weight (long tons)	Seats	Withdrawn	Notes
1	1934	Park Royal	1 AEC of 130 hp (97 kW)	24 long tons (24.4 t; 26.9 short tons)	69	1955	Prototype railcar
2–4	1934	Park Royal	2 AEC of 130 hp (97 kW)	26.2 long tons (26.6 t; 29.3 short tons)	44	1954–1958	Buffet fitted
5–7	1935	Gloucester RCW		25.3 long tons (25.7 t; 28.3 short tons)	70	1957–59	Standard single car
8–9, 13–16	1936			29.5 long tons (30.0 t; 33.0 short tons)	70	1957–60	9 withdrawn in 1946 after fire
10–12	1936			29.9 long tons (30.4 t; 33.5 short tons)	63	1956–57	Lavatory fitted
17	1936			28.85 long tons (29.31 t; 32.31 short tons)	None	1959	Parcels car, capacity 10 long tons (10.2 t; 11.2 short tons)
18	1937			33.6 long tons (34.1 t; 37.6 short tons)	49	1957	Prototype, with buffers & draw gear for hauling vans
19–33	1940–41	GWR, Swindon	2 AEC of 105 hp (78 kW)	35.65 long tons (36.22 t; 39.93 short tons)	48	1960–62	33 rebuilt in 1954 to replace 37
34	1941			34.9 long tons (35.5 t; 39.1 short tons)	None	1960	Parcels car, capacity 10 long tons (10.2 t; 11.2 short tons)
35–38	1941–42			36.7 long tons (37.3 t; 41.1 short tons) + 37.6 long tons (38.2 t; 42.1 short tons)	60 + 44	1957, 1962	Power twins with buffet and lavatory 35+36 and 37+38 37 withdrawn in 1949 after fire and replaced by 33

Five of the 38 railcars were destroyed by fires:^[6]

No 9 was burnt out at Heyford in July 1945; officially condemned in May 1946
No 10 was burnt out at Bridgnorth in March 1956; officially condemned in May 1956
No 35 and No 36 were destroyed by fire at St Anne's Park, Bristol in April 1956; officially condemned in April 1957
No 37 was damaged by fire in February 1949 and was stored until being scrapped; officially condemned in September 1949

Preservation

Three of the GWR railcars have survived into preservation:

Vehicle no.	Builder	Year built	Location	Comments
W4W	Park Royal	1934	National Railway Museum, York^[7]	Static display
W20W	GWR Swindon	1940	Kent & East Sussex Railway	Under restoration at Tenterden since 1983
W22W	GWR Swindon	1940	Didcot Railway Centre	Operational

Models

Hornby Railways manufacture a model of the 1940-style railcar in OO gauge, using tooling acquired in their takeover of Lima.^[8] In late 2017, Dapol released an OO model of the streamlined 1936 Gloucester RCW railcars in a variety of liveries and numbers. Heljan manufacture a model of the 1940-style railcar in OO gauge, using new tooling, that includes internal lighting and front and rear lighting.^[9]

Graham Farish produced an N-gauge model (with various numbers, e.g. 19, 22, and 20), both before and after their takeover by Bachmann.

References

^ ^a ^b ^c ^d ^e Judge, C. W. (2008). The history of Great Western A.E.C. diesel railcars. Southampton: Noodle. ISBN 978-1-906419-11-0. OCLC 233788958.
^ Handbook for railway steam locomotive enginemen. Shepperton: Ian Allan. 1998. ISBN 0-7110-0628-8. OCLC 59990926.
^ ^a ^b "Great Western railcars. The Park Royal bodied railcars, numbers 1 to 4". The Great Western Archive. Retrieved 2 March 2020.
^ "Great Western railcars. The Gloucester bodied railcars, numbers 5 to 18". The Great Western Archive. Retrieved 2 March 2020.
^ ^a ^b "Great Western railcars. The Swindon bodied railcars, numbers 19 to 38". The Great Western Archive. Retrieved 2 March 2020.
^ Judge, Colin (2008). The History of the Great Western A.E.C. Diesel Railcars. Kevin Robertson (Noodle Books). p. 227. ISBN 9781906419110.
^ "Back home! Swindon legends go back on display". The Railway Magazine. Vol. 161, no. 1, 377. Horncastle, Lincs: Mortons Media Group. 2 December 2015. p. 9. ISSN 0033-8923.
^ "Hornby GWR Diesel Railcar". Hornby Railways Collector Guide. Retrieved 29 March 2020.
^ "OO GWR Railcars - Now in Production". UK Model Railway Locomotives, Rolling Stock & Accessories. 16 March 2021. Retrieved 22 October 2023.