Alternative valve mechanism

Nigel has dubbed my timing wheel "the Bramwell gear" which is quite a coincidence because i have a book entitled Railways and Locomotives, lectures selivered at the school of military engineering at chatham in 1877 by John Wolf Barry and Frederick J Bramwell.! In it there are many beatifully drawings including three types of valve linkage; ordinary, reverse radial and straight. Here is a photo of the ordinary linkage

Relation of yours?

Those old text-books are a great source of information for model-engineering, by showing typical design practices contemporary with the types of machine we are replicating. I have a few, one of which concludes a chapter on water-turbines with the assertion that the world's rivers should supply enough power for mankind's needs... in 1911!

Mill-engines fitted with plain valve-gears driven by just an eccentric to run in only one direction to drive factory machinery, were sometimes fitted with a slotted eccentric bolted to a disc keyed to the crankshaft, to be set clockwise or anticlockwise to suit the particular installation.

One small stationary-engine preserved at Weston Zoyland Pumping-Station Museum (fen-draining) has cam-drive poppet-valves, somewhat as in a car engine. The cam is elongated with a tapering profile giving a varying throw by its position along a keyed shaft, controlled by the governor, so maintaining constant speed by varying the cut-off rather than a throttle-valve.