aluminium valves???

[87gn@tahoe]

I am in the process of drawing up some balanced slide valves to retrofit my father's Doty compound with.

I was wondering if hard anodized aluminium would be considered acceptable taking into account that they would be balanced and wear pressure on the valve face should be greatly reduced...

What think you?

[barts]

I would expect aluminum valves to gall very quickly, esp. if one was sparing with the lubricant. I'd think hard before using anything but cast iron or bronze. Alternatively, consider bronze welding up a wear surface on a steel valve. Slide valves get a lot of abuse.

- Bart

[Lopez Mike]

I concur completely. Cast iron on cast iron is the least trouble of all. I have balanced slide valves on my 2.5" to the foot locomotive and the balance makes the life of the valve gear much easier. Don't get carried away with the percentage of balance though. 80% is plenty. You need some sealing pressure. And with saturated steam and a nice finish on the inside of the valve chest cover, I have had good service from an ordinary Viton O-ring.

Mike

[87gn@tahoe]

Perhaps a wear face that is attached with countersunk screws?

I was having trouble finding a cast iron supplier near me, and aluminum was available, but I have since found a supplier for continually cast cast iron in my area...

Now for the next question; at rectangular balanced side (instead of the regular round one) with filleted corners, sealed with a close machining tolerance and an o-ring? The problem is the LP valve is 4.5"x9" and there's not enough vertical clearence to go with a 9" diameter backing.

[barts]

Perhaps a wear face that is attached with countersunk screws?

I was having trouble finding a cast iron supplier near me, and aluminum was available, but I have since found a supplier for continually cast cast iron in my area...

Now for the next question; at rectangular balanced side (instead of the regular round one) with filleted corners, sealed with a close machining tolerance and an o-ring? The problem is the LP valve is 4.5"x9" and there's not enough vertical clearence to go with a 9" diameter backing.

Wear plates would work just fine. Just make sure the screws don't loosen.
mcmaster.com has iron in various sizes and shapes... not the cheapest source, but it's easy. This is where I bought the iron for Otter's slide valve plate.

A rectangular area would work fine. Note that the o-ring _will_ wear - I had a system like this on Otter's old engine for a while, but had problems maintaining a smooth finish on the inside of the steam chest cover. It would rust slightly, and the O-ring would wear out right away. If you have the clearance, a cast iron on cast rubbing surface would be more rugged. You can always get more room with a spacer plate under the valve chest cover - something I didn't think about on Otter's old engine. Also, note that a balanced slide valve may not lift as easily to relieve cylinder overpressure due to condensation - make sure there's enough clearance to allow this to happen.

- Bart

[Lopez Mike]

The rust can be a problem. My loco is lubricated half to death so rust isn't a problem.

Another solution I have seen when the valve is long like that is to use two round cast iron rings. You get more area and you can use ordinary piston rings and take the wear on a side. The stationary gas engine crowd uses great big thick rings that might work just fine. Sometimes they are 1/4" wide which would give you clearance for the valve to lift more and release any trapped water.

Mike

[87gn@tahoe]

Thanks guys. Mcmasters online catalog doesn't show the dimensions I need. I suppose I could pick up the phone and talk to an actual person...ug

Another reason I asked about the aluminium was that I see some specialty piston manufacturers offering hard anodized coatings, and figured with a balanced valve (less loading) and adequate lubrication just maybe...

I called the suppliers near me and they were less than helpful,.

[Lopez Mike]

As soon as you say steam they think you are either building either a steam cleaner or an espresso machine. I have taken people off of the beach for a turn around the bay and late in the experience had them say, "So what does it run off of?" (Not dangling participles at any rate). This after watching me pitch hunk after hunk of stove wood through the firebox door.

I guess I can understand children not getting it. On the full sized loco when kids would ask about motive power, I would run the reverse lever back and forth several times and avow that I was winding it up. But adults? Sitting there with the oil fire rumbling and steam leaking out all over the place and not getting it?

Grump.

Actually one of my favorite things is when I have over fired a bit just before heading to the dock. Rather than let it pop, I let it churn away on a slow bell. Time after time I have been been notified by dock walkers that my propeller is going around and around. I act surprised and concerned and put it in reverse and explain that it will unwind the engine that way.

By the way, Wes, I love your video of downtown Stockton where you mistake that grossero yacht for your launch. I will use that some time.

Mike

[87gn@tahoe]

Mike.. I thought it was a cute touch.

I rarely mention steam in my acquiring of parts/materials/advice anymore, as like you said, it is met with blank stares and less than helpful customer service. They suddenly take you for nutcase and a waste of their time. VERY frustrating.

Two sealing/balancing rings side by side is a good idea, didn't think of that (obviously!)

I suppose a slick wear surface sandwiched between the valve cover and valve chest, made out of some corrosion resistant material would help with sealing and o-ring life.

Now, porting through on the LP so that it sees vacuum is a given, but on the HP? should I make a small hole (in the centre of valve travel) through the valve cover (don't worry they're nothing special, just a flat cast plate with no builders marks) so the valve sees atmospheric pressure, or through the valve like the LP so that it sees the LP receiver pressure (20+ PSI above atmosphere)? I'm thinking the lower pressure the better, as well as the hole through the cover would be a good indicator for when the o-ring needs replacing.

I will build in at least 1/4" lift-off clearance as well as drilling and tapping the (plain also) cylinder covers for pressure relief valves. Wouldn't want to destroy a irreplaceable engine..

I wonder how many Doty (Toronto and Goderich, Ontario, Canada 1881-1895)engines still exist? I know of 5, all compounds, of differing sizes; 1 large compound in a museum in Ontario, 2 large compounds (250hp each?)in the RMS Segwun in Gravenhurst, Ontario, 1 75hp compound in the S.S. Pumper somewhere in Ontario, and 1 in our garage.

Anyone know of any more? Perhaps available?

"A man with a technical knowledge and who is a good mechanic is a better man than a mechanic without a technical knowledge… Men who have not a technical knowledge are only equal to inferior men."

- John Doty

[barts]

Wes -

Note Mike's suggestion of running two piston rings sideways in a circular groove cut into the top of the slide value rubbing against the wear plate... no rubber/metal wearing bits that way. You might well need a wavey piece of spring wire underneath to press the ring against the wear plate...

- Bart