From 1920, the cab side of Great Western Railway (GWR) steam locomotives bore a letter on a coloured disc, which enabled staff to quickly assess the capabilities of locomotives without the need to check tables of data. The letter showed the power classification, and the coloured disc showed the weight restriction. This system continued after the GWR became the Western Region of British Railways. [1] [2]
On 1 July 1905 the Great Western Railway (GWR) introduced a system for denoting both the haulage capabilities and the weight restrictions which applied to their various classes of locomotive. Originally this was used only in record books, but from mid 1919 began to be shown on the locomotives themselves. The weight restriction was shown in the form of a coloured disc, and the power classification was denoted by a capital letter placed upon the disc. At first these were painted high on the cab side, but during World War II the blackout precautions meant that staff had to be careful using lights at night, so the disc and letter were moved downwards to a position just above the engine number plate, to make them easier to see. [3]
When locomotives were loaned by other railways to the GWR during World War II, these were also allotted GWR power and weight classifications, so that GWR staff responsible for locomotive rostering could select the most suitable engine for the task without needing to learn an unfamiliar system. [3]
The GWR was nationalised in 1948, becoming the Western Region of British Railways. In 1949, BR decided to adopt the London, Midland and Scottish Railway (LMS) system of power classification for all locomotives. Despite this, the use of a letter to denote power classification continued to be used on former GWR steam locomotives, as did the coloured disc for weight classification; both continued until the end of steam traction on the Western Region in 1965. [4] Certain ex-LMS and BR Standard steam locomotives allocated to the Western Region were given GWR style route classification discs, [4] usually without the power class letter. Some of these had the BR power class shown on the disc as a figure; for example, the Class 5 4-6-0 bore the figure "5" on a red disc. [5] The coloured disc was also applied to some diesel locomotives allocated to the Western Region.
The letter represents the power of the locomotive, and is approximately proportional to the starting tractive effort, thus: [1]
| GWR/BR Power Class | Tractive effort | Example locomotive classes |
|---|---|---|
| Special | Over 38,000 lbf (169.0 kN) | 6000 (King) |
| E | 33,001–38,000 lbf (146.8–169.0 kN) | 2884, 7200 |
| D | 25,001–33,000 lbf (111.2–146.8 kN) | 4073 (Castle), 4300, 5600 |
| C | 20,501–25,000 lbf (91.2–111.2 kN) | 4500, 5700 |
| B | 18,501–20,500 lbf (82.3–91.2 kN) | 1101, 2251 |
| A | 16,500–18,500 lbf (73.4–82.3 kN) | 1600, 2301 |
| Ungrouped | Below 16,500 lbf (73.4 kN) | 1361, 1400 |
The "Special" classification was not shown on the "King" class, [6] but in the case of no. 111 The Great Bear, "Special" was shown by a cross (+) on its red route restriction disc. [7]
Locomotives loaned during World War II were given GWR power class letters, in order to avoid confusion with different systems used by the lending railway. For example, the Southern Railway (SR) also used letters, but with A representing the highest power; so when the SR loaned some S15 class 4-6-0s to the GWR, which were power class A on the SR, they were placed in power class D by the GWR; [8] [3] similarly, the London, Midland and Scottish Railway loaned some 2-8-0 locomotives of their power class 8F, which were given GWR power class E. [3]
Also during World War II, it was decided that some classes of two-cylinder engines (including the 1000 (County), 4900 (Hall) and 6800 (Grange) classes) would be permitted to haul loads heavier than those specified in the working books for their power classification. These engines were distinguished by a white letter "X" painted above the number plate. [3]
The GWR system was divided into "red", "blue", "yellow" and "uncoloured" routes, according to the maximum axle load which the Civil Engineer would permit: for example, engines of axle load greater than 16 tons were not permitted onto "yellow" or "uncoloured" routes. In between these were "dotted red" and "dotted blue" routes, where overweight engines were permitted subject to speed restrictions. In addition, there were the "hatched red" routes, where any locomotive was permitted: the 6000 (King) class were barred from all except the "hatched red" routes. In August 1938 a summary of the GWR routes by colour was published: [3]
| Colour | Geographical miles | Percentage | Notes |
|---|---|---|---|
| Hatched red | 522 | 14% | All engines allowed |
| Red | 1280 | 34% | All engines allowed, except King class |
| Dotted Red | 285 | 8% | Red engines (see below) allowed at no more than 20 mph (32 km/h) |
| Blue | 320 | 9% | |
| Dotted Blue | 150 | 4% | Blue engines allowed at no more than 25 mph (40 km/h) |
| Yellow | 695 | 18% | |
| Uncoloured | 495 | 13% |
The "hatched red" routes comprised Paddington to Bristol Temple Meads, both via Bath and via Badminton; Reading to Devonport via Newbury; Bristol Temple Meads to Taunton; and Paddington to Wolverhampton Low Level via Bicester. Further routes were raised to this category after Nationalisation: Wolverhampton to Chester via Shrewsbury; and Bristol to Shrewsbury via Abergavenny. [2]
Up to two coloured discs were painted on the cabside of GWR steam locomotives and some Western Region diesel locomotive classes, to show that the maximum axle load of the engine did not exceed a particular value, the absence of such circles meaning that no restrictions applied to the locomotive: [3]
| Colour | Symbol | Axle load | Example locomotive classes |
|---|---|---|---|
| Double Red |  | 22 long tons 10 cwt (50,400 lb or 22.9 t) | 6000 (King) |
| Red | | Up to 20 long tons 0 cwt (44,800 lb or 20.3 t) | 4700, 4900 (Hall), 9400, Class 42 |
| Blue |  | Up to 17 long tons 12 cwt (39,400 lb or 17.9 t) | 2884, 6100 |
| Yellow |  | Up to 16 long tons 0 cwt (35,800 lb or 16.3 t) | 2251, 4500, Class 22 |
| Uncoloured | Up to 14 long tons 0 cwt (31,400 lb or 14.2 t) | 1366, 2301 |
As with the power classifications, locomotives loaned to the GWR in World War II were given GWR weight restriction colours. For example, engines of LNER Class J25, which were Route Availability 3 on that line, were placed in GWR route restriction "Yellow". [9]
There were occasional amendments in the light of operating experience; for example, the 5700 class (which had an axle loading of 16 long tons 15 cwt (37,500 lb or 17 t)) were found to have a low hammer blow, so caused less damage to the track than other engines of their axle load; accordingly, in 1950, they were reclassified from "Blue" to "Yellow". [10] [11]
The Great Bear, number 111, was a locomotive of the Great Western Railway. It was the first 4-6-2 (Pacific) locomotive used on a railway in Great Britain, and the only one of its type built by the GWR.
The Great Western Railway 3200 Class was a design of 4-4-0 steam locomotive for passenger train work. The nickname for this class, almost universally used at the time these engines were in service was Dukedog since the locomotives were composed of former Duke Class boilers on Bulldog Class frames. As such they were one of the last standard gauge steam locomotive classes to retain outside frames.
The Great Western Railway (GWR) 6800 Class or Grange Class was a mixed-traffic class of 4-6-0 steam locomotive, built to replace the GWR 4300 Class 2-6-0. There were 80 in the class, all built at the Swindon works, using some reconditioned parts from withdrawn 4300 Class locomotives.
The Great Western Railway (GWR) 2251 Class or Collett Goods Class was a class of 0-6-0 steam tender locomotives designed for medium-powered freight. They were introduced in 1930 as a replacement for the earlier Dean Goods 0-6-0s and were built up to 1948.
The GWR 5600 Class is a class of 0-6-2T steam locomotive built between 1924 and 1928. They were designed by Charles Collett for the Great Western Railway (GWR), and were introduced into traffic in 1924. After the 1923 grouping, Swindon inherited a large and variable collection of locomotives from historic Welsh railway companies, which did not fit into their standardisation programme. GWR boiler inspectors arrived en masse and either condemned the original locomotives or had them rebuilt. The systematic destruction of many examples of locomotives, most still in serviceable condition, followed, but various were worked alongside 5600 Class.
The Great Western Railway (GWR) 5400 Class was a class of 0-6-0 pannier tank steam locomotive. They were similar in appearance to many other GWR tank engines but smaller than the ubiquitous GWR 5700 Class.
The Great Western Railway (GWR) 2600 Class or Aberdare Class was a class of 2-6-0 steam locomotive built between 1900 and 1907. They were a freight version of the 3300 and 4100 classes, both 4-4-0 locomotives. Therefore, the design was adapted and became a 2-6-0 type; the resulting locomotives were used for hauling coal trains between Aberdare and Swindon.
The Great Western Railway (GWR) 2221 Class or County Tank was a class of 4-4-2T steam locomotive, effectively a tank engine version of the 3800 "County" Class 4-4-0 tender locomotives. The two classes had different boilers, standard no 4 for the tender locomotive, and the smaller standard no 2 for the tank. 2230 was fitted with the larger boiler when new, but this was unsuccessful and was quickly altered.
The Great Western Railway (GWR) 4500 Class or Small Prairie is a class of 2-6-2T steam locomotives.
The Great Western Railway (GWR) 2301 Class or Dean Goods Class is a class of British 0-6-0 steam locomotives.
The Dean Single, 3031 Class, or Achilles Class was a type of steam locomotive built by the British Great Western Railway between 1891 and 1899. They were designed by William Dean for passenger work. The first 30 members of the class were built as 2-2-2s of the 3001 Class.
The GWR 388 class was a large class of 310 0-6-0 goods locomotives built by the Great Western Railway. They are sometimes referred to as the Armstrong Goods or Armstrong Standard Goods to differentiate from the Gooch Goods and Dean Goods classes, both of which were also large classes of standard goods locomotives.
La France, number 102, was a locomotive of the Great Western Railway. It was bought by G.J. Churchward to evaluate French locomotive practice, and particularly the effect of compounding.
The GWR 378 Class was a class of 30 standard-gauge 2-2-2 steam locomotives on the Great Western Railway in Britain. They were introduced in 1866, and the class remained intact until 1898. Several were altered to the 0-6-0 wheel arrangement, and the last was withdrawn from service in 1920.
The GWR 633 Class were 0-6-0Ts designed by George Armstrong and built at the Wolverhampton railway works of the Great Western Railway between November 1871 and April 1872. These were always Southern Division locomotives, but over the years some were fitted to work the Metropolitan lines and played a large role in the transportation of goods from Acton to Smithfield. Unusually, they had side tanks, and inside frames, with wheels of 4 ft 6+1⁄2 in (1,384 mm) in diameter and a wheelbase of 15 ft 6 in (4.72 m). Their weight was 34 long tons 12 cwt. There were twelve locomotives, numbered 633–644.
The Great Western Railway's 1813 Class was a series of 40 0-6-0T built at Swindon Works in two lots of 20 engines each. No. 1813 was sold to the Pembroke & Tenby Railway in May 1883 becoming No.7 Holmwood, retaining this name after being absorbed by the GWR. Nearly all of these engines spent their lives on the GWR's Southern Division.
The 1661 Class was William Dean's second design of tank locomotive for England's Great Western Railway. Like the 1813 Class which preceded them, there were 40 1661s, turned out of Swindon Works in two batches.
The GWR 1854 Class was a class of 0-6-0T steam locomotives designed by William Dean and constructed at the Swindon Works of the Great Western Railway. The class used similar inside frames and chassis dimensions to the 1813 Class of 1882-4. In this they differed from the intervening 1661 Class, which had reverted to the double frames of the Armstrong era. Thus the 1854 Class belongs to the "mainstream" of GWR 0-6-0T classes that leads towards the larger GWR pannier tanks of the 20th century.
GWR No. 36 was a prototype 4-6-0 steam locomotive constructed at Swindon Works for the Great Western Railway in 1896, the first 4-6-0 ever built for the GWR and one of the first in Britain. It was designed by William Dean and le Fleming comments that "the design is unusual and entirely Dean of the later period, including the only large boiler ever built entirely to his ideas."
The 4600 Class was a 4-4-2T steam locomotive built by the Great Western Railway in 1913. It was one of the GWR standard classes with two outside cylinders.
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