GWR 3521 Class


The 3521 Class were forty tank locomotives designed by William Dean to haul passenger trains on the Great Western Railway. They were introduced as 0-4-2T locomotives in 1887, but were quickly altered to become 0-4-4Ts to improve their running. Following two serious accidents they were further altered from 1899 to run as 4-4-0 tender locomotives, in which form the last was withdrawn in 1934.

Locomotives

0-4-2T standard gauge

The first twenty locomotives were turned out in 1887 as 0-4-2T locomotives for services on the lines.
In 1888 a further batch of twenty were ordered as 0-4-2ST saddle tanks for the broad gauge lines in Devon and Cornwall.
Due to the unsteady running of the 0-4-2STs, the last of the order, 3660, was turned out in August 1889 as a 0-4-4T bogie side tank. The remainder of the class were altered to a similar layout over the following two years. 3660 was slightly different at this time, having a bogie that was shorter and an overall wheelbase of, rather than the of the converted locomotives.
The standard gauge 0-4-2Ts were converted to 0-4-4Ts in the same manner as the broad gauge locomotives, which were all eventually converted to standard gauge. By the end of 1892 the whole class of forty locomotives was to one standard design for the first time.
All forty 0-4-4T locomotives were rebuilt as 4-4-0 tender locomotives between 1899 and 1902. Twenty six locos retained their parallel domed boilers while fourteen received new Standard No 3 parallel domeless boilers.
Holcroft was of the opinion that the original inside and outside frames were modified whereas Le Fleming was of the opinion that new inside frames would have been required. However, as the modification also increased the coupled wheelbase from 7 ft 4 in to 8 ft 6 in it is unlikely that much of the original framing was re-used.
Two locomotives, 3521 and 3546, were transferred to the Cambrian Railways in 1921 to replace locomotives destroyed in the Abermule accident. They were allocated Cambrian numbers 82 and 95 respectively but these were never carried, the two locomotives being returned to the Great Western Railway with their original numbers when the two railways were grouped together in 1922.

Accidents and incidents