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GWR 6000 Class
The Great Western Railway (GWR) 6000 Class or King Class is a class of 4-6-0 steam locomotives designed for express passenger work and introduced in 1927. They were the largest locomotives built by the GWR, apart from the unique Pacific (The Great Bear). The class was named after kings of the United Kingdom and of England, beginning with the then reigning monarch, King George V, and going back through history. They handled the principal GWR expresses on the main line from London to the West of England and on the Chiltern line to Birmingham and Wolverhampton, until 1962 when the class was withdrawn.
By 1918, it was apparent to the GWR chief mechanical engineer George Jackson Churchward that his Star Class 4-6-0 locomotives would soon be incapable of handling the heaviest West of England expresses without assistance. He therefore proposed fitting the 6 ft (1.83 m) diameter boiler used on his 4700 Class 2-8-0 on to a 4-6-0 chassis, in 1919, to create a more powerful express locomotive, but was prevented from doing so by the weight restrictions on the GWR main line. The future problem was therefore left for his successor Charles Collett to solve.
On taking up office in 1922, Collett began to develop the more powerful Castle Class from Churchward's Star Class. However, the design was limited to a maximum axle-loading of 19.5 long tons (19,800 kg) due to the weakness of some underline bridges. The new class would not therefore be able to pull express trains with more than thirteen coaches unaided. Following their introduction in 1923, the Castle Class was the most powerful express passenger class in the country in terms of tractive effort, but this title was lost to the Southern Railway's Lord Nelson class in 1926.
The GWR's General Manager, Sir Felix Pole, was anxious for a new design that would once again enable the company to claim to run the most powerful locomotive. Pole agreed to allow Collett to explore a design for a "Super-Castle", subject to getting the tractive effort above 40,000 lbf (180,000 N). By 1927, a series of bridge renewals had taken place on the Great Western mainlines. This was coupled with the widely known (but as yet unpublished) findings of the Bridge Stress Committee, which gave engineers a better scientific understanding of the impact of hammer blow, and enabled the GWR Civil Engineer to agree to raise the maximum allowable axle-loading to 22.5 long tons (22,900 kg) for the new ‘Super Castle’ class.
Although Collett was nominally responsible for the design of the class, the detailed work was undertaken by his Chief draughtsman Frederick Hawksworth. The bulk of the increase in power over the Castle Class was initially achieved through raising the boiler pressure to a maximum of 250 pounds per square inch (1.72 MPa) and by increasing the cylinder stroke from 26 in (660 mm) to 28 in (711 mm). These factors together increased the tractive effort to around 38,165 lbf (169,770 N), slightly below the figure required by Pole.
As a means of increasing the tractive effort to bring it closer to the 40,000 lbf (180,000 N) requested by Pole, smaller 6 ft 6 in (1.981 m) driving wheels were used compared to the standard 6 ft 8.5 in (2.045 m) on the "Castles" and the first six locomotives to be built had their cylinders bored out to 16.25-inch (412.8 mm) giving a further 990 lbf (4,400 N), thereby enabling the ‘Kings’ to achieve a tractive effort of 40,300 lbf (179.3 kN). The smaller wheels also allowed for a wider boiler within the loading gauge to be used.
Later operational experience showed that loading gauge clearance of the outer cylinders was problematic, resulting in their replacement on each locomotive's first major overhaul, which resulted in a reduced tractive effort of 39,700 lbf (176.6 kN).
The new, 16 feet 0 inches (4.88 m) long, GWR ‘Standard No.12’ boiler was used on only this class. It had a maximum diameter of 6 feet 0 inches (1.829 m) tapering to 5 feet 6+1⁄4 inches (1.683 m). There were 171 x 2+1⁄4-inch (57 mm) fire tubes, and 16 x 5+1⁄8-inch (130 mm) flue tubes. The firebox area was 194 square feet (18.0 m2), with a tube area of 2,008 square feet (186.5 m2). As built, they had 96 × 1-inch (25 mm) superheater tubes.
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GWR 6000 Class
The Great Western Railway (GWR) 6000 Class or King Class is a class of 4-6-0 steam locomotives designed for express passenger work and introduced in 1927. They were the largest locomotives built by the GWR, apart from the unique Pacific (The Great Bear). The class was named after kings of the United Kingdom and of England, beginning with the then reigning monarch, King George V, and going back through history. They handled the principal GWR expresses on the main line from London to the West of England and on the Chiltern line to Birmingham and Wolverhampton, until 1962 when the class was withdrawn.
By 1918, it was apparent to the GWR chief mechanical engineer George Jackson Churchward that his Star Class 4-6-0 locomotives would soon be incapable of handling the heaviest West of England expresses without assistance. He therefore proposed fitting the 6 ft (1.83 m) diameter boiler used on his 4700 Class 2-8-0 on to a 4-6-0 chassis, in 1919, to create a more powerful express locomotive, but was prevented from doing so by the weight restrictions on the GWR main line. The future problem was therefore left for his successor Charles Collett to solve.
On taking up office in 1922, Collett began to develop the more powerful Castle Class from Churchward's Star Class. However, the design was limited to a maximum axle-loading of 19.5 long tons (19,800 kg) due to the weakness of some underline bridges. The new class would not therefore be able to pull express trains with more than thirteen coaches unaided. Following their introduction in 1923, the Castle Class was the most powerful express passenger class in the country in terms of tractive effort, but this title was lost to the Southern Railway's Lord Nelson class in 1926.
The GWR's General Manager, Sir Felix Pole, was anxious for a new design that would once again enable the company to claim to run the most powerful locomotive. Pole agreed to allow Collett to explore a design for a "Super-Castle", subject to getting the tractive effort above 40,000 lbf (180,000 N). By 1927, a series of bridge renewals had taken place on the Great Western mainlines. This was coupled with the widely known (but as yet unpublished) findings of the Bridge Stress Committee, which gave engineers a better scientific understanding of the impact of hammer blow, and enabled the GWR Civil Engineer to agree to raise the maximum allowable axle-loading to 22.5 long tons (22,900 kg) for the new ‘Super Castle’ class.
Although Collett was nominally responsible for the design of the class, the detailed work was undertaken by his Chief draughtsman Frederick Hawksworth. The bulk of the increase in power over the Castle Class was initially achieved through raising the boiler pressure to a maximum of 250 pounds per square inch (1.72 MPa) and by increasing the cylinder stroke from 26 in (660 mm) to 28 in (711 mm). These factors together increased the tractive effort to around 38,165 lbf (169,770 N), slightly below the figure required by Pole.
As a means of increasing the tractive effort to bring it closer to the 40,000 lbf (180,000 N) requested by Pole, smaller 6 ft 6 in (1.981 m) driving wheels were used compared to the standard 6 ft 8.5 in (2.045 m) on the "Castles" and the first six locomotives to be built had their cylinders bored out to 16.25-inch (412.8 mm) giving a further 990 lbf (4,400 N), thereby enabling the ‘Kings’ to achieve a tractive effort of 40,300 lbf (179.3 kN). The smaller wheels also allowed for a wider boiler within the loading gauge to be used.
Later operational experience showed that loading gauge clearance of the outer cylinders was problematic, resulting in their replacement on each locomotive's first major overhaul, which resulted in a reduced tractive effort of 39,700 lbf (176.6 kN).
The new, 16 feet 0 inches (4.88 m) long, GWR ‘Standard No.12’ boiler was used on only this class. It had a maximum diameter of 6 feet 0 inches (1.829 m) tapering to 5 feet 6+1⁄4 inches (1.683 m). There were 171 x 2+1⁄4-inch (57 mm) fire tubes, and 16 x 5+1⁄8-inch (130 mm) flue tubes. The firebox area was 194 square feet (18.0 m2), with a tube area of 2,008 square feet (186.5 m2). As built, they had 96 × 1-inch (25 mm) superheater tubes.