The Great Western Railway (GWR) 5700 Class, or 57xx class, is a class of 0-6-0 pannier tank steam locomotive, built between 1929 and 1950. 863 were built, making them the most prolific class of the GWR, and one of the most numerous classes of British steam locomotive.[1][a]

Although officially designated by GWR as "light goods and shunting engines",[2] 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 British Railways Western Region, and also other regions.

The 5700s were not as glamorous as the GWR Castles and Kings, but became just as much of an icon of the GWR.[3]

As a result of the 1955 Modernisation Plan, the 5700 Class was withdrawn from BR service between 1956 and 1966. Nineteen withdrawn locomotives were sold to London Transport and industry, of which ten were later preserved, along with six that were retrieved from scrapyards.

The GWR started designing and building 0-6-0 tank locomotives in 1860,[4] and this continued into the BR era until 1956, with a total of 2,393 being built.[5] The GWR also used 0-6-0 tank locomotives from other manufacturers' designs (from its subsidiary and absorbed railways' stock[6]), and since 1898 it always had at least 1,000 tank locomotives in stock.[5]

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). GWR first fitted pannier tanks (mounted on the side of the boiler but not reaching down to the running platform) in 1898 to nine 4-4-0 tank locomotives and, in 1901, to five 0-6-0T locomotives which were also fitted with Belpaire fireboxes.[7] The shape of the Belpaire firebox gives a larger surface area which improves heat transfer and steam production,[8] but their rectangular shape made them difficult to combine with saddle tanks.[9] Locomotives fitted with pannier tanks have a lower centre of gravity than those with saddle tanks (enabling higher speeds on curves),[9] and access for maintenance is easier than for those fitted with side tanks.[10]

Churchward's period as Chief Mechanical Engineer (1901–21) is well known for significant improvements in locomotive design and manufacture,[11] and the development of standard designs.[12] However, the scope of the standard designs did not include the 0-6-0 tank locomotive,[13] and the GWR did not introduce any new 0-6-0 tank designs from 1897 to 1928 (with exception of the GWR 1361 class of five 0-6-0 saddle tanks in 1910).[14]

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).[5] The rebuilding program also included a number of other changes including:

improved cab designs, eventually becoming fully enclosed[15]
superheating, which by 1929, had been found to have little benefit on shunting engines[1]
adaptation for working with autocoaches for push–pull trains (auto-working)[5]
increasing boiler pressures, for example, the various rebuilds of the GWR 2721 class started at 150 lbf/in2 (1.03 MPa), increasing to 165 lbf/in2 (1.14 MPa), and then to 180 lbf/in2 (1.24 MPa)[16]

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.[17][18] In addition, GWR's stock was wearing out,[13] and the variety of classes was problematic for maintenance and rostering.[19] Collett had to produce a new standard design for 0-6-0 pannier tanks.[2] The result was 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. The boiler included a top-feed (between the chimney and dome). They were similar in appearance to older 0-6-0 tank engines that had been rebuilt as pannier tanks, particularly the later rebuilds of the 2721 class. The 2721 class was itself a development of the 1854 class, which in turn was based on the 645 class.[1]
Specification

The table below gives the technical specifications of the 5700 class. Values are from GWR diagram B48[20] unless referenced otherwise.
5700s technical specifications Dimensions

Length over buffers: 31 ft 2 in (9.50 m) Width: 8 ft 7 in (2.62 m) Height: 12 ft 3 1⁄16 in (3.74 m)

Firegrate area 15.3 sq ft (1.42 m2)
Firebox

Outside: 5 ft 4 in (1.63 m) x 4 ft 7 3⁄8 in (1.41 m) and 4 ft 0 in (1.22 m)
Inside: 4 ft 7 3⁄16 in (1.40 m) x 3 ft 8 in (1.12 m) and 3 ft 3 3⁄4 in (1.01 m)
Height: 6 ft 0 1⁄2 in (1.84 m)

Tubes

2 off diameter 5 1⁄8 in (0.13 m) 233 off diameter 1 5⁄8 in (0.04 m) Length: 10 ft 6 13⁄16 in (3.22 m)

Heating surface

Tubes: 1,075.7 sq ft (99.94 m2)
Firebox: 102.3 sq ft (9.50 m2)
Total: 1,178.0 sq ft (109.44 m2)

Boiler

Barrel: 10 ft 3 in (3.12 m) Outside diameter: 4 ft 5 in (1.35 m) & 4 ft 3 7⁄8 in (1.318 m) Pitch: 6 ft 11 3⁄4 in (2.127 m)

Working pressure 200 lbf/in2 (1.38 MPa)
Cylinders

Two Inside Diameter: 17 1⁄2 in (0.44 m) Stroke: 24 in (0.61 m)

Valve gear Stephenson (slide)[21]
Wheels 4 ft 7 1⁄2 in (1.410 m) diameter, coupled
Wheelbase 15 ft 6 in (7 ft 3 in + 8 ft 3 in) (4.72 m (2.21 m + 2.51 m))
Tractive effort (85%) 22,515 lbf (100.15 kN)
Coal capacity 3 long tons 6 cwt (7,400 lb or 3.4 t)[1]
Water capacity 1,200 imp gal (5,500 l; 1,400 US gal)
Weight (full)

First axle: 16 long tons 15 cwt (37,500 lb or 17 t)
Second axle: 16 long tons 15 cwt (37,500 lb or 17 t)
Third axle: 14 long tons 0 cwt (31,400 lb or 14.2 t)
Total: 47 long tons 10 cwt (106,400 lb or 48.3 t)

Minimum curve

Normal: 5 chains (330 ft; 100 m) Slow: 4 1⁄2 chains (300 ft; 91 m)[22]

The 5700s were given the GWR route colour Blue[b] (based on axle load), and were in the GWR power group C (based on tractive effort).[24] 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"[1] and Holcroft describes them as "practically identical to 2721 rebuilds",[25] but according to Nock it was "a thoroughly modern design",[26] and Jones notes that design included "numerous detailed improvements" and reflected improved construction techniques.[27] The main differences from the 2721 class include:

increased boiler pressure,[28] from 180 lbf/in2 (1.24 MPa)[29] to 200 lbf/in2 (1.38 MPa),[1] giving a corresponding increase in tractive effort
improved valve settings[28]
longer frame, from 26 ft 9 in (8.15 m)[30] to 27 ft 6 in (8.38 m)[20]
fully enclosed cab[28]

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).[1] The locomotives were also fitted with cast iron chimneys (which had only rarely been fitted to earlier locomotives),[1] 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.[c]

However, the 50 locomotives of the 6700 Class, 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.[31] The 6700s had a smaller minimum curve radius of 4 chains (260 ft; 80 m) (normal) and 3 1⁄2 chains (230 ft; 70 m) (slow) and an increased axle clearance.
8750 Sub-class

The 8750 Class, 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.[23] The new style cab was derived from the sister 5400 class, the first of which were built in 1931.[31] 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).[23] The locomotive weight increased to 49 long tons 0 cwt (109,800 lb or 49.8 t), and the axle load increased to 17 long tons 0 cwt (38,100 lb or 17.3 t).[23]
9700 Class
A pannier tank locomotive adapted for underground working. The pannier tank shown is shorter than usual, starting behind the smokebox and after about a third of its length extends down to the footplate. At the front there is a pump and extra pipe work, which also extends above the boiler.
No. 9701 at Paddington, showing the modified tanks and condensing apparatus

The 9700 Class, 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.[1] They were specifically for working on the Metropolitan/Hammersmith & City lines between Paddington Stations and Smithfield Meat Market. They replaced Metro and 633 class locomotives.

The eleven locomotives in the class had condensing apparatus that fed the exhaust steam back into the water tanks.[32] 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.[32] 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.[32] 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.[23][32] The design changes resulted in reduced coal (2 long tons 16 cwt (6,300 lb or 2.8 t)) and water (1,230 imp gal (5,600 l; 1,480 US gal)) capacities.[23] The locomotive weight increased to 50 long tons 15 cwt (113,700 lb or 51.6 t), and the axle load increased to 17 long tons 4 cwt (38,500 lb or 17.5 t).[23]
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.[23]
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.[23]
in 1937 a drawing was issued for fitting shutters and doors to the older, pre-8750 class, locomotives.[23]
in 1938 a larger whistle shield was fitted, which became standard for the larger cabs.[23]
in 1942 a new type of top feed was introduced, with separate clackboxes in a taller cover, and internal delivery pipes rather than trays.[23]

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.[23]
Variants

A small number of 5700s were adapted for specific tasks:

in 1937, 1938 and during World War II thirteen 5700s were fitted with spark arresting chimneys for work on industrial and military sites with significant fire risks.[23][32][d]
in 1958 No. 3711 was converted to oil burning by Robert Stephenson and Hawthorns.[33][e]
in 1946 No. 7722 was fitted with winding gear to work the Pwllyrhebog Colliery incline on the former Taff Vale Railway.[1][33]

Production

The first 5700s were built in 1929 by North British Locomotive Co. and, later in the year, at GWR's Swindon Works.[22] 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)[f]
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 (50 of the 200 strong 5600 class had been built by Armstrong Whitworth).[g][18] The building programme was partly funded by interest-free Government loans intended to relieve unemployment during the Great Depression.[1] 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.[36]

At first, more 5700s were built than were immediately needed so Nos. 6700–49 were stored for a couple of years before being allocated.[1] Many of these were then assigned to sheds near the South Wales ports of Newport, Barry, Cardiff and Swansea.[37]

After a gap of a year, building started again in 1933, with the 8750 and 9700 classes, and continued until 1950.[38] All the later locomotives, totalling 563, were built at Swindon, and the numbers built only dropped in the last few years with the introduction of the 9400 class in 1947.