Charles Benjamin Collett (10 September 1871 – 5 April 1952) was Chief Mechanical Engineer of the Great Western Railway from 1922 to 1941. He designed (amongst others) the GWR's 4-6-0 Castle and King Class express passenger locomotives.
Charles was the second son of the journalist William Collett (1843-1884) and his wife Mary Helen nee Cook (about 1847-1923). The family settled at 33 Tavistock Terrace, Westbourne Park and it was near here that his older brother, William Augustus Mallalue, was fatally injured whilst playing in the GWR Goods Yard on 18 September 1879. Charles reported the accident to a servant that William had lost both his legs. He died that evening at St Mary's Hospital.
C B Collett was educated at the Merchant Taylors' School (then at Charterhouse Square, London) and the City and Guilds College of London University. He then became an engineering pupil at Maudslay, Sons and Field, a firm that built marine steam engines. In 1893 he entered the GWR Drawing Office at Swindon as a junior draughtsman. Four years later he was put in charge of the buildings section, and in 1898 became assistant to the Chief Draughtsman. In June 1900 he was appointed Technical Inspector, and soon after Assistant Manager, at the Swindon Works. In 1912 he rose to be Manager of the Works, then in 1919 he was made Deputy Chief Mechanical Engineer of the GWR.
Collett's predecessor, George Jackson Churchward, had delivered to the GWR from Swindon a series of class-leading and innovative locomotives, and arguably by the early 1920s the Great Western‘s 2-cylinder and 4-cylinder 4-6-0 designs were substantially superior to the locomotives of the other railway groupings.
In 1922 Churchward retired, and Collett inherited a legacy of excellent standardised designs. But, with costs rising and revenues falling, there was a need to rationalise the number of pre-grouping designs and to develop more powerful locomotives. Collett was a practical development engineer and he took Churchward's designs and developed them – notably the Hall from the Saint class, and the Castle from the Star. He was also responsible for more humble locomotives, such as many of the pannier tank classes.
By the time Churchward retired, his 4-cylinder Star class locomotives were becoming inadequate for the increasing loads and speeds expected of express passenger trains. To solve this, Churchward had proposed fitting a No 7 boiler (designed for the 4700 class 2-8-0 express freight engines) onto a Star. This was not possible, because the weight would be too great for the track. Instead, Collett enlarged the Star design, leaving the wheels the same but with bigger cylinders and a new standard boiler that would not exceed the 19+1⁄2 ton permitted axle load. He also fitted a more comfortable cab. The result was christened the Castle class, and the first engine, No 4073 Caerphilly Castle, was soon proudly paraded at the British Empire Exhibition, (placed close to the larger LNER Flying Scotsman) with the claim that it was 'Britain's most powerful passenger locomotive'.
One result of this provocative claim was an agreed exchange of locomotives between the companies. Castle class No 4079 Pendennis Castle went to the LNER in exchange for A1 class No 4474 Victor Wild. Both engines acquitted themselves well, but the performance of the smaller Castle led Gresley to investigate the cause and redesign the A1's valves, as well as give them a higher boiler pressure.
As well as rebuilding several Star class locomotives into Castles, Collett shocked some people by rebuilding the GWR's flagship 4-6-2 locomotive No 111 The Great Bear into a 4-6-0 Castle. This at least drew the attention of General Manager Sir Felix Pole to the restrictive permitted axle loads, which had constrained the usefulness of this prestige symbol. When larger locomotives were needed, Sir Felix instructed the Civil Engineer to ensure that the main lines (Paddington–Plymouth, via Westbury or Bristol, and Paddington–Wolverhampton via Bicester) could carry a 22+1⁄2 ton axle load. This was quickly done, since work was already underway to meet this standard.
By 1926, the other railway companies were catching up with the GWR, with designs such as the LNER Pacifics (improved as a result of the GWR/LNER locomotive exchange), SR Lord Nelson class, and the imminent LMS Royal Scot Class. Better locomotives were needed not only for faster and heavier trains, but also for to uphold the prestige of the GWR. Collett started by testing 6 ft 6 in driving wheels on No 5001 Llandovery Castle. When this proved satisfactory, he spread these wheels out under a larger and higher-pressure boiler, and increased the piston stroke to 28 inches, pushing the design to the limit both of the loading gauge and the newly increased axle load. Fitting these increased dimensions together required an unusual front bogie, with outside bearings on the front axle but inside bearings on the rear, to clear the inside and outside cylinders respectively. Finally, the first loco (or first five) had cylinders bored out to 16+1⁄4 inches. The significance of this small change was that it pushed the calculated tractive effort over 40,000 lbs, as required by Sir Felix Pole, thereby emphasising the locomotive's status as the most powerful passenger locomotive in the country. It was named the King class.
Like the Castle class, the King class was exploited for its publicity value. The very first one, No 6000 King George V, was shipped off to America where it led the parade of engines at the Baltimore and Ohio Railroad Centenary Exhibition, and whence it returned carrying a commemorative bell on its front buffer beam. The King class remained the heaviest and most powerful 4-6-0 engine in Britain. Stanier paid it the compliment of using its principal dimensions (Boiler pressure, cylinder size and wheel diameter—and therefore tractive effort) in his first design, the 4-6-2 LMS Princess Royal Class.
However, while it has been described as Collett's masterpiece, the suggestion has also been made that it was largely the responsibility of Hawksworth, Collett's eventual successor, who was then Chief Draughtsman.
A curious event in the story of the 4-cylinder designs was the appearance of two streamlined locomotives. In the 1930s there was a vogue for streamlining, and Collett came under pressure to produce a streamlined locomotive for the GWR, particularly in view of the forthcoming centenary of the company in 1935. The story goes that Collett took a paperweight model of a King, and smeared plasticine over it to produce an outline for the drawing office to work from. Although probably apocryphal, this may have been as good a way of designing a streamlined loco as any, short of carrying out tests in a wind tunnel. Collett was certainly aware of the many other factors causing drag. As The Great Western Railway Magazine put it, "Rigorous application of the principles of scientific streamlining becomes not only difficult but practically inexpedient, as the net reduction in the total resistance may be relatively small." In March 1935, locomotives 5305 Manorbier Castle and 6014 King Henry VII were outshopped with a hemispherical dome over the front of the smokebox, fairings covering the front buffer beam, cylinders, and splashers, fairings behind the chimney and dome, a vee-shaped cab front and a tapered roof over the tender. Both of these engines, and no others, were given a full-page photograph in the GWR's 1935 publication Swindon Works and its place in Great Western Railway History, but without any further descriptive text. The locomotives gradually lost the streamlined features as they passed through the shops in following years.
Absorbed locomotives and the 5600 class 0-6-2T
Collett became CME just before the grouping of British railway companies took effect on 1st January 1923. Although the GWR retained its identity by virtue of being grouped with many much smaller railways, it did make Collett responsible overnight for over 800 locomotives, of a wide variety of designs, many in a state of disrepair. The ones in the worst condition could only be scrapped; those in a better condition were surveyed to establish which could be refitted with boilers from the GWR standard range, including three new boilers modified for the purpose. The scrapping of so many unmaintainable engines left a shortfall in power, especially in the Welsh valleys where the widely-used compact inside-cylinder 0-6-2T engines were hard to replace with standard GWR classes. Collett decided to build a new class, based on the Rhymney Railway R class 0-6-2T. Although it used a standard No. 2 boiler, and as many other standard parts as possible, the cylinder castings, wheels, hornblocks, valve gear and three-bar motion crosshead were all new designs. The 5600 class was powerful and versatile, working both passenger and freight trains in the Welsh valleys in a characteristic 'facing up the valley' direction, so that on the faster descending services, the pony truck helped to keep them stable.