Our small gang were busy with the ever progressing overhaul of Tyseley's flagship engine: the double-chimney Castle Class 4-6-0 No7029 "Clun Castle". She is now looking very much like an engine again, though there is still a long way to go. Even though she looks pretty much complete, the untrained eye would be surprised to see just how much work remains. I suppose the phrase "it'll be done when its done" is all you can say. However, the progress is very much there and it will be fantastic to see this historic Castle move under her own steam once again. Who needs to say it with two chimneys when you can say it with four?! It'll be a great and loud occasion...
What is interesting whilst studying the Castle, and indeed other GWR four-cylinder types, is the Walschaerts valve gear set-up between the frames. They use a divided drive with the two inside pistons driving the leading axle and the outside pistons driving the main crank axle. An axle-mounted eccentric is used instead of a return crank and the expansion links swing from a common cross-shaft, being driven from the bottom by the appropriate eccentric. Rocking levers then transfer the valve positioning motion from the inside to the outside valves. There is a good demo video here. Its an interesting set-up and one that obviously works very well. After a very enjoyable (if chilly) day at Tyseley, I headed for home at just after 4pm. For those interested, the Vintage Trains website is here with a variety of tours on offer for 2017. Cheers all, Sam...
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