GWR 6619 rests at Embsay

Tea break for the crew between runs

 

 

When the GWR took over the Welsh valley lines, they discovered that the Welsh locomotive crews liked their 0-6-2T locomotives. Rather than a new design the 5600 Class was a "Swindonised" version of the Rhymney Railway M class and R class locomotives. The 1904 M class (and the similar 1909 R class) were successful designs ideally suited to hauling heavy coal trains a relatively short distance.
The 5600 Class was specially designed for work in South Wales, replacing the elderly, worn-out locomotives that had been 'inherited' in 1923, when the smaller railway companies were forcibly merged into the GWR at The Grouping. Contrary to this trend, the Rhymney Railway's more modern 0-6-2s were in generally good order and had proved successful. Thus they became the blueprint for the 56xx.
The first of five R class locos was re-boilered by the GWR in 1926 and a single M class was upgraded in 1930. In this form, both were visually almost indistinguishable from the 56 Class.

The design of the 5600 Class followed Great Western Railway practice as far as possible, by utilising many standardised parts. Included in Collett's innovations was a Standard Number 2 boiler which was suitable for the 5600 Class, and the M and R class Rhymney locomotives, complete with the traditional brass GWR safety valve casing and copper-capped chimney.
They were substantial sized tank engines, 37 ft 6ins in length and weighing 62 tons. The side tanks were capable of holding 1900 gallons of water. The high domed cab, bunker and tanks were closely related to the 31xx and 42xx classes. One hundred of the class were built at the GWR workshops in Swindon from 1924-1927.
In 1927 another 100 similar engines were constructed – these were slightly heavier and numbered in the 66xx series. Nos 6600-6649 were Swindon-built in 1927-1928, but due to the pressure of work 6650-6699 were built by Armstrong Whitworth in 1928. This resulted in some minor design differences from the Swindon locomotives.

My thanks to Wikipedia for the above.