Would not British Caprotti Valve Gear be better suited to the 5AT than Walschaerts?

There are many people (including many with great knowledge of the subject) who challenge Wardale’s choice of Walschaerts valve for the 5AT, believing that British Caprotti (as used on the BR 8P Pacific No 71000 Duke of Gloucester) would have been a far more appropriate choice because it offers larger port openings and zero back pressure when coasting.

Wardale strongly defends his choice and has explained his reasons in several letters, some of which are included in the page titled “Why Walschaerts Valve GearWhy Walschaerts valve gear?”.  However a more comprehensive reply is recorded in a letter from David Wardale to John Duncan which is transcribed over 7 pages titled “Piston Valves vs. Caprotti Valves – The Final Discussion?” and in PDF format in Wardale responses to Caprotti proposals 3 Sept 2009.