STEAM ENGINE VALVE LEAKS

[oscar blaumanParticipant @oscarblauman34278]

[oscar blaumanParticipant @oscarblauman34278]

I have just completed a Stuart N1 engine which works well under compressed air.

It does leaks considerably when the valve position is such that I would not expect any air to come out from the exhaust. I did spend considerable time polishing both the cylinder wall and the valve bronze sliding part, they are almost mirror like now, without any measurable difference. I would like to know how good of a seal the valve should make to be considered good enough and if there is something else I should be looking at other than the good mating of the surfaces, thanks oscar.

[Derek DroverParticipant @derekdrover32802]

Hi Oscar

With sliding valves, both faces not only need to be to a good polish, but they need to be flat. If you've not used a flat surface to polish on you may create slight gaps.

Also, are you running it dry or with a little oil applied? I'd try adding a little steam oil and see if that helps seal things up.

Rgds

del.

[RedsetterParticipant @redsetter]

Assuming the contact faces are reasonably flat, the seal will gradually improve as the engine is run in. A fine matt finish is preferable to a highly polished one. I usually finish the valve and port face by rubbing on fine wet and dry paper laid on a flat surface. Do not run it without oil.

[MichaelRParticipant @michaelr]

Have you got a little bit of float on your slide valve buckle ? which will allow the steam/air pressure to seal the valve to the port face.

MichaelR.

[JasonBModerator @jasonb]

As Michael says any tightness of the nut in the groove,valve rod in the cross groove or a wonky thread can stop the valve finding it's own position on the port face, you want it free but not sloppy

I don't polish of flatten any of my engines, just run them straight away with the machined finish.

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