The Steamboating Forum

I have strongly recommended to her that she have a balanced valve built and installed. It would do the least violence to the design and esthetics of the engine.

I have successfully used an O-ring for the riding valve to chest cover seal but it hasn't worked for everyone. The finish of the chest cover seems to be the sticking point. I inserted a polished S.S. shim between the chest and chest cover. Got a fair service out of the O-ring.

The traditional design for small engines with a piston ring riding against the chest cover would probably be the conservative solution. Even a bronze ring I suppose?

I cannot remember the percentage of balance I used. 80% comes to mind.

I ran Otter's old engine for a year this way, but the O-ring died multiple times, despite use of #600 paper on valve chest rubbing surface.

- Bart

Hard to improve much on iron to iron in saturated steam. Once it beds in it seems to wear forever.

Lopez Mike wrote:Hard to improve much on iron to iron in saturated steam. Once it beds in it seems to wear forever.

Yup. Trick w/ balanced valve is that you need some 'float', and the balance piece needs a bit of a phosphor bronze spring to keep it against the valve chest. Lots of parts to go in a small space, but making a different valve chest cover can help.

- Bart

What do you mean balanced valve? And, what part does the O ring play? I made the new eccentric today but I haven't reassembled the engine to try it yet. I believe one of the screws in the shift linkage backed out and locked up the valve rod which broke it. This also broke the keyway out of the eccentric casting. All remade now and I put jam nuts on the back of the linkage screws.
I thought it interesting that Bart had to close the throttle to shift the linkage. I hadn't thought about the stiction on the stopped valve. I have pondered why the shifter is so hard to reverse.
Thanks for the help.

What is a balanced slide valve?

https://www.youtube.com/watch?v=1R4OFznjkF0

- Bart

It should not escape your notice that this modification is essentially reversible. Just yank out the cup and plug the four tapped holes in the original D-valve.

As Bart has noted, it might be prudent to replace his O-ring with an iron or bronze ring with a light spring behind it. Air on the bench with no load is rather different than steam under load.

I dunno about making the cup out of aluminum. Maybe O.K.

There sure was a lot of wear on his cylinder port face. I would lap that flat while I was at it.

Mike, could it be made into a compensated valve, to relieve the load (or is it already)?

That's what it is, indeed. Just a different name.

I do not see how a solid slider could ever be made that would seal unless maybe there was an O ring placed behind it to push it against the wall or perhaps a wave spring.
I am trying to relate this balanced valve idea to the tapered valve I made a few weeks ago for the rocking valve engine. You can imagine how much friction there is in the mating tapers. I had to put a stop in the actuator end to keep the valve from pushing back and locking up. the adjustment was tedious and is one of the reasons I did not put the engine into the boat.
I have the original Semple single cylinder, the stuart 6a and the rocking valve. Granted, I only need one but I like playing with the other to learn their performance characteristics.
The Semple is the most reliable but reversing is difficult and cannot be accomplished quickly enough for docking and other close situations.