The GWR 5700 Class (or 57xx class) is a class of steam locomotive built by the Great Western Railway (GWR) and British Railways (BR) between 1929 and 1950. With 863 built, they were the most prolific class of the GWR, and one of the most numerous classes of British steam locomotive.
Although officially designated by GWR as "light goods and shunting engines", they were also used for passenger working on branch, suburban, and shorter mainline journeys. They were distributed across most of the GWR network and, after nationalisation of the railways in 1948, across the Western Region of British Railways, and also other regions. Although not as large as the GWR Castles and Kings, they became just as much of an icon of the GWR, due to their iconic design and quantity.
As a result of the 1955 Modernisation Plan, the 5700 Class was withdrawn from BR service between 1956 and 1966. Nineteen withdrawn locomotives were sold to the London Transport Executive and industry, of which ten were later preserved, along with six that were retrieved from scrapyards.
Background The GWR started designing and building 0-6-0 tank locomotives in 1860, and this continued into the BR era until 1956, with a total of 2,393 being built. The GWR also used 0-6-0 tank locomotives from other manufacturers' designs (from its subsidiary and absorbed railways' stock), and since 1898 it always had at least 1,000 tank locomotives in stock.
The early 0-6-0 tank engines were fitted with either saddle tanks (wrapped over the boiler) or side tanks (mounted at the side of the boiler and reaching down to the running platform). The Great Western first fitted pannier tanks (mounted on the side of the boiler but not reaching down to the running platform) in 1898 to a single 4-4-0T locomotive, No. 1490, and, in 1901, to two 0-6-4 crane tank locomotives. They started to be fitted to 0-6-0 tanks from 1903, but weren't being fitted more generally until about the end of 1909. The shape of the Belpaire firebox gives a larger surface area which improves heat transfer and steam production, but their rectangular shape made them difficult to combine with saddle tanks. Locomotives fitted with pannier tanks have a lower centre of gravity than those with saddle tanks (enabling higher speeds on curves), and access for maintenance is easier than for those fitted with side tanks.
George Jackson Churchward's period as Chief Mechanical Engineer from 1901 to 1921 is well known for significant improvements in locomotive design and manufacture, and the development of standard designs. However, the scope of the standard designs did not include the 0-6-0 tank locomotive, and the GWR did not introduce any new 0-6-0 tank designs from 1897 to 1928 (with exception of the 1361 Class of five 0-6-0 saddle tanks in 1910).
However, pannier tanks and Belpaire fireboxes became the standard for the rebuilding of various 0-6-0 tank locomotives (projected in 1902 and getting fully underway by 1910). The rebuilding program also included a number of other changes including: improved cab designs, eventually becoming fully enclosed superheating, which by 1929, had been found to have little benefit on shunting engines adaptation for working with autocoaches for push–pull trains (auto-working) increasing boiler pressures, for example, the various rebuilds of the GWR 2721 class started at , increasing to , and then to
With the completion of grouping in 1923, GWR's collection of 0-6-0 tank locomotives was expanded with the stock from 28 acquired companies. The acquired tank locomotives came from different manufacturers, were a mixture of side, saddle and pannier, and varied widely by size and state of repair. In addition, GWR's stock was wearing out, and the variety of classes was problematic for maintenance and rostering. Collett had to produce a new standard design for 0-6-0 pannier tanks, which resulted in the 5700 Class.
Design
The first batch of 300 locomotives built between 1929 and 1931 included a medium height chimney, a mid-boiler dome, safety valve with cover, and an enclosed cab. They were similar in appearance and design to older 0-6-0 tank engines that had been rebuilt as pannier tanks, particularly the later rebuilds of the 1854 Class (based on the earlier 645 Class), retaining the latter's 'four down, two up' layout of springing, longer smokebox and forward-mounted chimney (necessitated by the re-positioning of the regulator within the smokebox). The cylinders and driving wheels of the later 2721 Class were adopted and the front overhang was extended from to . The frames were strengthened and altered in configuration to 'marry up' with the longer smokebox (unlike the '1854' rebuilds), and the injectors, valances, and wheel centres redesigned (this being a 14-spoke offset crankpin arrangement instead of the earlier 16-spoke in-line one).
Specification
The table below gives the technical specifications of the 5700 class. Values are from GWR diagram B48 unless referenced otherwise.
+ 5700s technical specifications Dimensions Firegrate area Firebox Tubes Heating surface Boiler Working pressure Cylinders Valve gear Stephenson (slide) Wheels diameter, coupled Wheelbase 15 ft 6 in (7 ft 3 in + 8 ft 3 in) ( ( + )) Tractive effort (85%) Coal capacity Water capacity Weight (full) Minimum curve
The 5700s were given the GWR route colour Blue (based on axle load), and were in the GWR power group C (based on tractive effort). The classifications were shown on the cab with the letter C in a blue disc.
le Fleming describes the 5700 class as "an almost unaltered continuation of the 27xx rebuilds" and Holcroft describes them as "practically identical to 2721 rebuilds", but according to Oswald Nock it was "a thoroughly modern design", and Jones notes that design included "numerous detailed improvements" and reflected improved construction techniques. The main differences from the 2721 class include:
increased boiler pressure, from to , giving a corresponding increase in tractive effort improved valve settings longer frame, from to fully enclosed cab
The initial design also included a return to non-fluted coupling rods and laminated springs beneath the leading and driving axleboxes (both features harking back to the 1854 class). The locomotives were also fitted with cast iron chimneys (which had only rarely been fitted to earlier locomotives), and the whistles were fitted on top of the firebox rather than on top of the cab.
6700 Sub-class
Of the first batch of 300 locomotives, most were fitted with vacuum brakes and steam heating, and some of these were also fitted with GWR's Automatic Train Control (ATC) safety system.
However, the 50 locomotives of the 6700 or 67xx Class were not fitted with vacuum brakes, steam heating, or ATC, and were fitted with three link couplings only; they were therefore limited to shunting duties and some freight working. The 6700s had a smaller minimum railway curve radius of (normal) and (slow) and an increased axle clearance.
8750 Sub-class
The 8750 or 87xx Class were first built in 1933, using an updated design which included an improved cab with a higher roof, rectangular windows and grills (as opposed to the round windows (or "spectacles") of the initial design), and sliding shutters and hinged doors for more protection from the elements. The new style cab was derived from the sister 5400 Class, the first of which were built in 1931. Vacuum brakes, steam heating, and ATC were fitted as standard (except for Nos. 6750–79, built between 1946 and 1950, which were fitted with steam brakes and three link couplings only). The locomotive weight increased to , and the axle load increased to .
9700 Class
The 9700 or 97xx Class pannier tanks were a direct development of the 5700 class. The prototype for the class, No. 8700 (later No. 9700), was a rebuilt 5700 locomotive. They were specifically for working on the Hammersmith & City line between Paddington station and Smithfield Meat Market. They replaced Metro and 633 class locomotives.
The eleven locomotives in the class had a condensing apparatus that fed the exhaust steam back into the water tanks. The tanks themselves were shortened to make room for the external exhaust pipes and were extended down to the footplate in front of the cab to increase their capacity. As condensing the steam heated the water, a reciprocating pump (Weir pump) was fitted as a boiler feedwater pump because standard injectors will not work with hot water. The pumps led to (unsuccessful) tests with these locomotives acting as fire engines during World War II.
To work over the electrified underground lines, the 9700 Class locomotives had a special type of ATC equipment that lifted clear of the centre rail and had tripcock brake valves that matched the London Transport signalling system. The design changes resulted in reduced coal () capacity and a slight increase () in water capacity. The locomotive weight increased to , and the axle load increased to .
Later developments
From 1936 to 1942, a number of small changes were introduced to new builds:
In 1936, a whistle shield was added to the front of the cab to deflect steam away from the cab windows. Also in 1936, pocket steps and extra railings were added to the fireman's side (left side) of the cab to improve access to the bunker. In 1937, a drawing was issued for fitting shutters and doors to the older, pre-8750 class, locomotives. In 1938, a larger whistle shield was fitted, which became standard for the larger cabs. In 1942, a new type of top feed was introduced, with separate clackboxes in a taller cover, and internal delivery pipes rather than trays.
All these changes (with the exception of the new top feed) were later applied to locomotives that had been built earlier. The new top feed became standard for new locomotives in 1944. Some older boilers and locomotives were later fitted with the new top feed, and some locomotives that were built with the new top feed were later changed back to the old design as boilers were swapped.
Variants
A small number of 5700s were adapted for specific tasks:
From 1937 to the end of World War II, thirteen 5700s were fitted with spark arresting chimneys for work on industrial and military sites with significant fire risks. In 1958, No. 3711 was converted to oil burning by Robert Stephenson and Hawthorns. In 1946, No. 7722 was fitted with winding gear to work the Pwllyrhebog Colliery incline on the former Taff Vale Railway.
Production
The first 5700s were built in 1929 by North British Locomotive Co. and, later in the year, at GWR's Swindon Works. Between 1929 and 1931 a total of 300 were built, of which 50 were built by GWR, and the rest by outside contractors:
Armstrong Whitworth: 25 (Nos. 7775–99) W. G. Bagnall: 50 (Nos. 6700–24, 8725–49) Beyer, Peacock & Co: 25 (Nos. 8700–24) Kerr Stuart: 25 (Nos. 7700–24) North British: 100 (Nos. 5700–49, 7725–74) Yorkshire Engine Co: 25 (Nos. 6725–49)
It was unusual, but not unprecedented, for GWR to use outside contractors to build locomotives, as 50 of the 200 strong 5600 Class had been built by Armstrong Whitworth. The building programme was partly funded by interest-free government loans intended to relieve unemployment during the Great Depression. Also, stricter accountancy rules that distinguished between maintenance and building costs meant that it was often economically worthwhile to build new locomotives rather than repair older locomotives.
At first more 5700s were built than were immediately needed, so Nos. 6700–49 were stored for a couple of years before being allocated. Many of these were then assigned to sheds near the South Wales ports of Newport, Barry, Cardiff and Swansea.