Hi, I've made a Stuart D10 and fitted the drain valves on the cylinder sides.
I plan to use the engine in a model boat and remotely control the drain valves with a servo. I'm using a flash boiler and the drain valves are opened to maintain minimum steam flow when the engine is stationary.
Is there any reason that the valves can't be mounted a short distance away from the engine, using small bore pipe, to ease the connection of a shared servo linkage?
I wouldn't have thought it would make a lot of difference, depending on how far from the cylinders the valves are, and the bore of the pipe. You are effectively increasing the dead volume at each end of the cylinder by the volume of the extra length of pipe. This will need to be heated and cooled each stroke, just like the rest of the cylinder head is. Hence you're likely to get more condensation. I'd give it a try. and make sure the pipe is as well insulated as you can make it. The engine will likely be less efficient but should still work. Efficiency is not usually a major concern at this sort of size. Good luck with it, and let us know how you get on!
I've made a common drain valve block using a length of 1/4" stainless steel tube drilled with four drain inlets along its length and a common exhaust at one end. At the other end I've silver soldered a smaller diameter stainless steel rod which is used to rotate the tube in a brass housing with all the fittings attached.
I've used it with live steam up to 38psi and it performs very well without sticking even though it was built to close tolerances- it certainly makes the operation of the engine much easier especially starting up with the flash boiler.
Being the prototype it is a bit large, but could be made with smaller amounts of brass.
I don't know how to put images on this forum, but an image is available on the Model Boat Mayhem website:-
I presume you have to be a member to see the pics, they dont come up for me, just the text. To put a picture up, just use the next tag button to the right of the one for putting in hyperlinks, the one above the angry smilie. Click the button and put the weblink inbetween the 2 tags.
Simon. Tich, Invicta, Clayton lorry, 0.3cc Diesel, FD3/64 gas turbine. Weise Flying Scotsman part built, Seal 15cc part built. Currently researching 8th scale 14xx 0-4-2t and a 7.793 scale 2-6-2..... Now got a 3/4 acre garden to put a track round :-)