The Caprotti valve gear is a type of steam enginevalve gear invented in the early 1920s by Italian architect and engineer Arturo Caprotti. It uses camshafts and poppet valves rather than the piston valves used in other valve gear. While basing his design on automotive valves, Caprotti made several significant departures from this design to adapt the valves for steam. Having agreed a joint-venture with Worcester-based engineering company Heenan & Froude from 1938, Heenan & Froude fully acquired Caprotti post-World War II in 1947.
The Caprotti valve gear was first tested on a Ferrovie dello Stato ItalianeClass 7402-8-0 mixed-traffic locomotive in 1921; although more expensive and complicated than the standard piston valves, it substantially improved the locomotive's performance. Until the 1930s it was fitted on some 334 FS locomotives and on 77 narrow-gauge locomotives of other companies; of the former, some were new-builds, the others were rebuilds of non-superheated compound locomotives.
Given their need for more complex and expensive maintenance, most of these locomotives were generally withdrawn from service before those with Walschaerts valve gear, in the 1960s.
Usage in Great BritainEdit
In August 1926, the London, Midland and Scottish Railway equipped four-cylinder 4-6-0 locomotive no. 5908 of the Claughton Class with Caprotti valve gear and poppet valves. Following trials, nine more were rebuilt in 1928 with Caprotti valve gear, poppet valves and larger boilers, and also in 1928 ten others of the same class were given the larger boiler but retained the Walschaerts valve gear and piston valves with which this class was originally fitted, to enable comparisons to be made between the two types of valve gear. Later that year, no. 5908 was also given a larger boiler. It was found that the Caprotti-fitted locomotives were more economical on coal and water than those with Walschaerts valve gear, but it was later found that some of the losses of the Walschaerts locomotives was due to leakage of steam past the valve heads, where a single wide ring was used. New piston valves having several narrow rings were fitted to one locomotive, and it was then found that the Walschaerts valve gear could be just as economical as the Caprotti, but with considerably less cost of fitment. No more Claughtons were fitted with Caprotti valve gear, and the ten locomotives were withdrawn in 1935–36.[1]
On the London and North Eastern Railway (LNER), two 4-6-0 locomotives of LNER Class B3 were rebuilt with Caprotti valve gear in 1929, followed by a further two in 1938–39. These locomotives also had four cylinders, and the poppet valves were mounted vertically, two at each end of each cylinder. One of the first pair of locomotives was rebuilt with Walschaerts valve gear in 1943, but the other three ran with Caprotti valve gear until withdrawal in 1946–47.[2]
British CaprottiEdit
In the 1950s, Caprotti valve gear was improved and this British Caprotti valve gear was fitted to the last two British Railways-built 'Black Fives'44686/7, the last 30 BR standard class 5s, numbers 73125-54, and the unique BR standard class 8 71000 Duke of Gloucester. Results were mixed, with the performance of the Duke of Gloucester being particularly disappointing. That was later found to be due to errors elsewhere in the design and construction of the locomotive.
Although more expensive to manufacture than its rivals, the improved Caprotti valve gear is considerably more efficient than any other. A major improvement is that much of the mechanism is enclosed, leading to reduced wear and tear from the harsh steam locomotive environment, and completely independent control of admission and exhaust. The restored Duke of Gloucester, with its flaws eliminated, has proved the concept.
^Boddy, M.G.; Brown, W.A.; Fry, E.V.; Hennigan, W.; Hoole, Ken; Manners, F.; Neve, E.; Platt, E.N.T.; Proud, P.; Yeadon, W.B. (March 1975). Locomotives of the L.N.E.R., part 2B: Tender Engines - Classes B1 to B19. Lincoln: RCTS. pp. 17–18, 23. ISBN0-901115-73-8. OCLC 655688865.
External linksEdit
Wikimedia Commons has media related to Steam engines with Caprotti valvegear.
British Caprotti Valve Gear on the Duke of Gloucester
with Caprotti gear, Midland Railway - Butterley.
October 24, 2023
caprotti, valve, gear, type, steam, engine, valve, gear, invented, early, 1920s, italian, architect, engineer, arturo, caprotti, uses, camshafts, poppet, valves, rather, than, piston, valves, used, other, valve, gear, while, basing, design, automotive, valves,. The Caprotti valve gear is a type of steam engine valve gear invented in the early 1920s by Italian architect and engineer Arturo Caprotti It uses camshafts and poppet valves rather than the piston valves used in other valve gear While basing his design on automotive valves Caprotti made several significant departures from this design to adapt the valves for steam Having agreed a joint venture with Worcester based engineering company Heenan amp Froude from 1938 Heenan amp Froude fully acquired Caprotti post World War II in 1947 Duke of GloucesterCaprotti valve gear on BR no 73129 Contents 1 Usage in Italy 2 Usage in Great Britain 3 British Caprotti 4 References 5 External linksUsage in Italy EditThe Caprotti valve gear was first tested on a Ferrovie dello Stato Italiane Class 740 2 8 0 mixed traffic locomotive in 1921 although more expensive and complicated than the standard piston valves it substantially improved the locomotive s performance Until the 1930s it was fitted on some 334 FS locomotives and on 77 narrow gauge locomotives of other companies of the former some were new builds the others were rebuilds of non superheated compound locomotives Given their need for more complex and expensive maintenance most of these locomotives were generally withdrawn from service before those with Walschaerts valve gear in the 1960s Usage in Great Britain EditIn August 1926 the London Midland and Scottish Railway equipped four cylinder 4 6 0 locomotive no 5908 of the Claughton Class with Caprotti valve gear and poppet valves Following trials nine more were rebuilt in 1928 with Caprotti valve gear poppet valves and larger boilers and also in 1928 ten others of the same class were given the larger boiler but retained the Walschaerts valve gear and piston valves with which this class was originally fitted to enable comparisons to be made between the two types of valve gear Later that year no 5908 was also given a larger boiler It was found that the Caprotti fitted locomotives were more economical on coal and water than those with Walschaerts valve gear but it was later found that some of the losses of the Walschaerts locomotives was due to leakage of steam past the valve heads where a single wide ring was used New piston valves having several narrow rings were fitted to one locomotive and it was then found that the Walschaerts valve gear could be just as economical as the Caprotti but with considerably less cost of fitment No more Claughtons were fitted with Caprotti valve gear and the ten locomotives were withdrawn in 1935 36 1 On the London and North Eastern Railway LNER two 4 6 0 locomotives of LNER Class B3 were rebuilt with Caprotti valve gear in 1929 followed by a further two in 1938 39 These locomotives also had four cylinders and the poppet valves were mounted vertically two at each end of each cylinder One of the first pair of locomotives was rebuilt with Walschaerts valve gear in 1943 but the other three ran with Caprotti valve gear until withdrawal in 1946 47 2 British Caprotti EditIn the 1950s Caprotti valve gear was improved and this British Caprotti valve gear was fitted to the last two British Railways built Black Fives 44686 7 the last 30 BR standard class 5s numbers 73125 54 and the unique BR standard class 8 71000 Duke of Gloucester Results were mixed with the performance of the Duke of Gloucester being particularly disappointing That was later found to be due to errors elsewhere in the design and construction of the locomotive Although more expensive to manufacture than its rivals the improved Caprotti valve gear is considerably more efficient than any other A major improvement is that much of the mechanism is enclosed leading to reduced wear and tear from the harsh steam locomotive environment and completely independent control of admission and exhaust The restored Duke of Gloucester with its flaws eliminated has proved the concept References Edit Toms George Essery R J James F 2006 Historical Locomotive Monographs No 3 Claughton amp Patriot 4 6 0s Didcot Wild Swan pp 33 35 37 44 57 97 ISBN 1 905184 19 0 Boddy M G Brown W A Fry E V Hennigan W Hoole Ken Manners F Neve E Platt E N T Proud P Yeadon W B March 1975 Locomotives of the L N E R part 2B Tender Engines Classes B1 to B19 Lincoln RCTS pp 17 18 23 ISBN 0 901115 73 8 OCLC 655688865 External links Edit nbsp Wikimedia Commons has media related to Steam engines with Caprotti valvegear British Caprotti Valve Gear on the Duke of Gloucester BR Standard Class 5 No 73129 with Caprotti gear Midland Railway Butterley Retrieved from https en wikipedia org w index php title Caprotti valve gear amp oldid 1017135438, wikipedia, wiki, book, books, library,
