British Caprotti valve gear. 73129 departs Highley SVR

I shall republish this again in the interests of those

who have taken an interest in the Caprotti valve

gear. Much work was done by the LMS who fitted

the gear to a number of Black fives. This was not

the British Caprotti valve gear developed from the

original by LA Daniels. There is a distinct sharpness

to the exhaust

 

 

The last two of the 842 LMS Stanier Black Fives, numbers 44686 and 44687 were constructed by British Railways at Horwich Works in 1951. They were fitted with Caprotti valve gear, raised running plates without splashers, a double chimney and SKF roller bearings on all axles. Caprotti valve gear had previously been fitted to a batch of twenty Black Fives, nos. 44738-57, built in 1948. The valve gear on these was driven by one drive-line between the frames, driven from the leading coupled axle. Although these locomotives developed a great deal of power at high speeds and were free in coasting, acceleration at low speeds was poor. 44686 and 44687 were fitted with a modified form of valve gear, with an external shaft on each side, driven by a worm gear mounted on a flycrank attached to the driving axle. The British Caprotti valve gear was a new development of Caprotti valve gear by the Associated Locomotive Engineers, under the leadership of L.A. Daniels.
44686 and 44687 emerged from Horwich works in April and May 1951 respectively. The two locomotives cost £20,642 each, over £5,000 more than a contemporary standard Class Five. This was in part because of the high cost of development for a type of which only two examples were built. For much of their lives they were allocated to Longsight. 44686 was withdrawn in October 1965. 44687 was withdrawn in January 1966. Both were scrapped.
in the early 1960s both 44686 and 44687 worked off Southport shed (code 27C) on passenger trains from Southport to Manchester and Rochdale via Bolton. Other non-standard LMSR 5MTs were at Southport including LMSR Caprottis and the unique Stephenson Link machine 44767.
The success of the British Caprotti valve gear lead to its fitting to the final batch of BR standard class5s and also to the solitary BR standard class 8 71000 Duke of Gloucester. One of the Caprotti standard fives survives(73129), as does The Duke.

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