VALVE MECHANISMS
4 main parts to deal with.
- Eccentrics on main shaft
- The D valves themtselves
- The adjustable shafts
- Connecting rods – Connects eccentrics to adjustable shafts.
As noted earlier, few original parts that remain were in a very bad state and these were off one side only, so a complete set will have to be made for the second cylinder anyway. The eccentric on main shaft had been damaged and MAY be repairable but that has to be seen. The connecting rod was a fairly basic forged unit, but was badly bent and corroded. The threaded shaft similar. The D valve is a single CI casting, worn and corroded.
Much earlier in the restoration process, I had been aware of these issues so took steps to look into getting things moving on bits I couldn't easily do myself. Struggled for ages to find a 'proper' blacksmith to forge the connecting rods but finally got someone who came up with the goods at a reasonable price, they are rough and ready so will need cleaning up and machining to size etc.
The D valves were sourced from Oak castings who were excellent to deal with and did a fine job.
The adjustable shaft has a length of thread that fits through a hole slightly larger in the D Valve and each has 2 pairs of brass nuts holding it in position (so the D valve has a degree of free 'float'. The other end is a fork with an 5/16" pin (held by a small taper pin) that connects to the small end of the connecting rod.
The original would have been in one piece either forged then machined, or machined from solid. Due to equipment limitations, I made each in 2 parts making the forked end from square stock and the shaft from 3/8" bar, then silver soldering together. Appeared to work well, then completing the final machining after assembly to ensure correct alignment.
I had noticed that the original shaft had a coating of some kind, but suspect it was possibly there to inhibit corrosion, as the inside of the steam chest would be a pretty 'hostile' environment for steel? So am considering attempting home nickel electroplating – checked out a few 'YouTube' videos and it looks relatively straightforward – we shall see!
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Since the weather warmed up a bit, and Xmas was out of the way. managed to get on with all the above. Everything pretty straightforward so I shan't detail it in text, just added a few photos.
D valve castings machined, shaft plated and assembled successfully
Aligning link shaft for eccentric (Mill table only just long enough!)
Splitting the Eccentrics after turning / milling in one piece each
Shafts + Eccentrics fixed together
Oilways were machined in the eccentrics and small drip feed oilers sourced and fitted
Made a temporary fitting for the top of the cylinders – When I received the engine and did the check of what issues there were, one of the points I noted was that there was the broken remains of a threaded 'something' in the top of both cylinders. As mentioned at the beginning of this article, any valuable 'brass' parts seem to have been rather brutally robbed off the carcase many years ago! No idea originally what they were but subsequent investigation leads me to belive they are in fact the remains of manual oilers which were typical in very early engines. I (eventually) managed to get the remains out and determined they were a 1/2" x 12TPI Whit thread.
Here's an example from a model of an engine from the same era that I believe will be a suitable style.