- LMS Stanier Class 5 4-6-0 44738-57
British Railways built twentyLMS Stanier Black Five s, numbers 44738-57 withCaprotti valve gear in1948 .Overview
Previous black fives had had
Walschaerts valve gear as standard. The only previous exception was1947 -built (4)4767 which hadStephenson link motion . (4)4767 and the Caprotti black fives were part of an experimental programme byGeorge Ivatt to try to improve the already good design.The first of the Caprotti black fives was M4748 which emerged from Crewe in February 1948. It had, in addition to the different valve gear, other modifications which gave it a much different appearance. The boiler was pitched 2
inch es higher than previously and therunning plate was also lower, necessitating the use ofsplashers over the wheels. Thesmokebox was extended and thechimney set further forward. The cab was also a different shape.M4748 later became 44748 as BR replaced the short-lived M prefix by adding 40000 to most LMS numbers. Numbers 44748-57 were fitted with
Timken roller bearings . The last three of these, 44755-7 were also fitted with a double chimney. 44738-47 had plain bearings.In service, the Caprotti black fives were regarded by railwaymen as faster but less powerful that their Walschaerts valve-geared classmates.
The two ultimate black fives, 44686-7 were built in
1951 with Caprotti valve gear but with more detail variations. No others were so equipped, though construction with various experimental detail differences continued. Later BR built thirty of the closely-related standard class 5 with Caprotti valve gear, and it was also employed on the standard class 8 71000 "Duke of Gloucester".None of the Caprotti black fives has survived to preservation, being withdrawn in the
1960s . However, one of the Caprotti standard fives, 73129, and "The Duke" have both done so.
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