Trevithick Dredger Engine- Valves
by John
No workshop posts for a while because I have been making parts for the internals of the engine, and when installed they are not very photogenic.
Since the last post I have made the piston, piston rod and installed soft packing to seal the piston, made the valves and valve handles..
Stainless steel piston rod, bronze 20mm dia piston, and soft packing inserted into the machined groove.
Also made the throttle valve and steam direction valve.
This was the third attempt at making a steam valve. I went slightly undersized with the first, totally buggered the O ring groove on the second, but the third one looks OK.
Good one (I hope) on the left, and destroyed one on the right. The lathe tool bit into the bronze.
From left to right. The bush, the undersize, the buggered, and the OK I hope. and the plans.
And after all of that, and also making the throttle valve, I discovered a mistake in the plans. A 1mm discrepancy, which I suspect was an arithmetic mistake on the part of the plan maker. I decided to modify the valves, bush and valve block rather than remake the valves.
I machined 1mm off the faces shown in the photo, then spent some time prettying it up. Then took 1mm off the valve lengths, and the valve bush.
This is what it looks like now. All fixed. Waiting for Viton O rings to arrive. Looks OK IMO.
johnsmachines 