I have a couple of questions that I hope you can help me with.
Low water automatic
I need to replace the diaphragm and needle valve on a Low Water Automatic. How much clearance should I allow at ambient temperature. The originals are so far gone that I can't take any useful measurements from them.
The Stanley slide valve has quite a bit more exhaust lap on one end of the valve compared to the other end. I'm sure there's a good reason for it but what is it?
Steve the last question first.
Earlier Stanley engines had both ends of the valve the same. I believe whom ever did the design only did it for one end of the cylinder and then made both the same.
Two things you want the same when designing a double acting steam engine is for the lead (the amount the valve opens before TDC) and the percentage of compression, (when the valve closes at the other end of the stroke) to be the same at each end of the stroke.
This canít happen if both ends of the valve are the same do to the geometry of the movement of an eccentric. When you do a Bilgram Diagram for both ends of a valve for a double action cylinder on an eccentric operated slide valve the end of the valve face toward the crank is always wider then the opposite end.
Later on someone did the correct diagram as they built larger engines.
The wider valve face goes toward the crank.
The first question I canít answer. I only used one on my 1920 Stanley and canít remember the settings. But mean low water in a 23 inch Stanley boiler should be no less then four inches with the throttle opened at saturated operating pressure / temperature.
Iím still intrigued by the slide valve proportions. Bearing in mind that Iím used to fairly unsophisticated traction engines, every slide valve Iíve seen has always been the symmetrical with little or no exhaust lap. Rolly mentions Bilgram Diagrams which I hadnít heard of before. Iíve done a little bit of internet research but I have to say Iím none the wiser. Iíve used simple Reuleaux Diagrams but thatís about it and they donít show any difference between the front and back of the valve.
How do set the valve position? Iíve always done it Ďhooked upí because thatís where youíll spend most time and ensured that the valve opens at the same position from either TDC or BDC for each end of the stroke. Is that the right approach for the cars or is there a better way?
Iím aware that the valve gear design is what I would call Ďcrossed rodsí because you want the engine to turn backwards when you want to go forwards and that arrangement increases lead as you move towards mid gear.
I would appreciate yours comments. Even perhaps a reading list so I could find out a bit more.
Stanley used open rods, (piston toward the crank and eccentrics toward the cylinder block, eccentric rods not crossed.) when your in hookup the valve opens more before TDC and is more fully opened after TDC but closes earlier because it opened earlier, itís fixed by the eccentric.
Most people I have talked to adjust the valve for the same space at each end of the stroke. Not really the correct way. It should be the same angle of rotation. Most of the Stanley valves I have worked with are closed when the piston is at TDC. You should mark the gear on the crank for an angle 15 degrees past TDC in both top and bottom stroke and adjust the valve for the same opening. I made up wedges to do this and use layout die so I get the same thickness on the wedge for each end.
To be honest it not easy to tell the difference if there not just right when your driving the car.
On most marine engines they have cylinder ports on each end of the cylinder. I use a pressure gauge and air pressure and a protractor on the crank to set the valve to open at the same degree of angle before TDC both top and bottom of stroke.
Attached my big marine compound I built for my 35 footer.
I have always set my Stanley D valves with the engine in hook up while turing the engine in the forward direction that the engine runs in. For measuring valve lap, I use feeler guages. When I get equal opening indicated by the same drag of the feeler guage stack at either end of the slide valve, I then have equal valve lap.The low water automatic is set under steam while on the car. Between the Stanley Dealer Bulletins and the 1920 "Instructions for the Care and Operation of the Stanley Steam Car" most any question pertaining to the Stanley Steam Car are answered. The Stanley Dealer Bulletins are available through the Stanley Museum. The instructions book is available through The Steam Car Club of America, Inc.