Caprotti Valve Gear

[Chris CrewParticipant @chriscrew66644]

Having just admired Duke of Gloucester as built by The Steam Workshop on YouTube, I have suddenly become intrigued by the operation of Caprotti valve gear. I have viewed the animations by Graham Shirley but, to this bear of little brain at least, without commentary it is difficult to grasp the details of its operation except to appreciate the overall concept of a camshaft operating poppet valves. Achieving reversal and cut-off is, at this moment, a total mystery to me.

I would really like to try to understand more about this valve gear simply as a matter of interest because I certainly don't possess the level of skill required to build anything of this complexity and detail. Therefore, may I enquire if there any books available that may explain its operation in words of one syllable or where I may find more information about this fascinating mechanism.

[Chris CrewParticipant @chriscrew66644]

Any books?

[Clive Brown 1Participant @clivebrown1]

Hi Chris, I've got a vague memory that Martin Evans gave some explanation of Caprotti gear in his book "Model Locomotive Valve Gears". Might be wrong though, my copy went missing some time ago.

[Dennis RParticipant @dennisr]

Chris

Download this Pdf

https://www.theduke.uk.com/wp-content/uploads/woocommerce_uploads/2014/09/The-British-Caprotti-Valve-Gear-v02.pdf

[Chris CrewParticipant @chriscrew66644]

Dennis, thank you for the document link. I am beginning to get my head around the mechanism but not quite there yet, especially visualising the inlet valve's double lever and cam follower arrangement. It is certainly a very clever innovation of rotating two cams against each other to vary the arc of the lobe dwell. I will read the document's explanations again and try to relate it to the animations on YouTube.

[Author]

Posts