|Introduced||1924 – 1928|
|Weight||68t 12cwt (69t 7cwt – The Armstrong Whitworth builds)|
|Driving Wheels||4ft 7.5ins|
|Cylinders||Inside – 18in x 26in|
|Valve Gear||Stephenson (piston valve)|
The 0-6-2T type had been used extensively in the Welsh Valleys for working coal trains, in particular by the Rhymney, Taff Vale and Barry Railways. This class was a GWR development of the Rhymney Railway M class, built to work the same services.
|Rhymney Railway M class built in 1904. Six were built and three lasted to be taken into BR stock in 1948|
|Rhymney Railway M class rebuilt with a GWR boiler in 1930|
The 5600 class replaced many of the older miscellaneous engines acquired from the previously independent lines in South Wales, although some were to be found on other parts of the GWR.
Prior to the GWR takeover of lines in South Wales many of the railway companies stopped producing new engines and ran the locomotives into the ground. The result was that there was a very urgent need for replacement locomotives when the GWR took control and Collett was required to urgently to provide the answer. To make this possible the construction of Castle class locomotives was slowed down and the building of the 4300 class 2-6-0 locomotives was contracted out to Robert Stephenson & Co. The first 20 Castle locomotives took three years to produce whilst the contracting out of the 43oo engines was the first time this had been done by Swindon.
The result was a 0-6-2T design based largely on the Rhymney R class design with features taken from Swindon standard designs. The working drawings were dated August 1924 and the first engine was steamed only four months later in December of that year. The steaming of the first engine had to be cut very short because of problems with the design of the locomotive. An account of the event was later published by John Gibson in his book on Great Western Locomotive Design where he wrote the following based on an eye witness account.
“Full forward gear, drain cocks open, lubricator set to give a generous flow of oil, a touch on the whistle, the regulator opened carefully, the engine moved forward a few yards. Then horrors! With fearful groans and screeches from underneath, two of the four beats virtually disappeared. The regulator was shut hastily, and Swindon’s fine new engine shuddered to a shrieking halt.”
At the time forty-nine other engines were on order, twelve at least being erected, two or three almost ready for trials and all were desperately needed. The problem with the engines was caused by what was presumed to have been a junior draughtsman error in the design of the Stephenson valve gear which resulted in the end of the valve spindle being bent when the engine moved.
Collett is said to have issued commands the day after the trial steam. The first was that the staff responsible in the drawing office were not to leave their boards until they had worked out a solution. The second was that the event had not happened and anyone who dared to say otherwise would be dismissed instantly. The response from the drawing office was to produce a very robust solution which may not have been the easiest to maintain which was probably only applied to the first fifty locomotives as a better solution was later utilised.
While they were powerful machines, the 5600s were very unpopular with footplate crews at the time. They were beset by numerous failures, the most common of which was hot axle boxes. Eventually new machines built at Swindon had to be put into store, whilst those which failed in South Wales were examined for an explanation of the problem. It was discovered by the former Rhymney Railway workshops at Caerphilly that it was the tight tolerances that the GWR enforced which was the problem. Going around sharp bends, the axle boxes did not have the wider tolerances in the boxes as the previously built South Wales locomotives.
They were extremely versatile engines with impressive power and acceleration and capable of speeds of 60mph. The exceptional front overhang of the boiler and smokebox gave them an overbalanced appearance. They were fitted with superheated Belpaire boilers and had sloping tops to the side tanks.
6600 were introduced in 1927 with detail alterations, for example parallel buffers replaced the tapered type and balance weights fitted inside the driving wheels webs opposite the crank pin. The last fifty of these were built by Armstrong Whitworth. Some engines of this last batch were modified at Swindon for noisy brakes.
When the Welsh railwaymen discovered that the new 5700 class 0-6-0PT (introduced 1929) was even more suitable for the same work – being shorter and lighter, with roughly the same (slightly lower) tractive effort – no further Class 56xx/66xx were built.
From 1934, the class were fitted with recesses in the rear bunker, and later on, sliding screens were fitted to the cab sides.
One feature of the class was that they ran better in reverse than in forward gear, making the trailing wheels into a bogie wheel.
All of the locomotives were built at Swindon Works apart from 6650-99 which were constructed by Armstrong Whitworth of Newcastle in 1928.
The first withdrawals of the class were four locomotives in May 1962, while the last engine in service was 6668 which survived until the last month of GWR steam in December 1965.
The 5600 Class had the distinction of being the only locomotive of 0-6-2 wheel arrangement built new by the GWR. Nevertheless, there were just over 400 of the type in service from 1940–1945, demonstrating the large number acquired in 1923.
The locomotives were employed almost exclusively in South Wales. A handful spending time in the English Midlands and one or two being based in North Wales at Croes Newydd in the later days of steam working.
Due to these engines working in Wales, eight of the nine preserved examples were taken to Woodham scrapyard at Barry after withdrawal.