Help! > Specific Engine Help
Vertical steam slide vale size as function of port size?
Reggleston:
Earlier this year at the NAME expo I purchased a set of castings from a well known US supplier of a Prototype Vertical bottle frame type of engine he hopes to sell sometime in the future. The castings are of decent quality but BP's have been very poor, some duplicates of hand drawn shop sketches. The castings don't match the limited and poor prints that were provided. I have successfully built the engine up to the point of trying to get it to run which I haven't been able to do at this point. The cylinder had the ports cast in and the crank has finally been fitted with a suitable connecting rod to achieve smooth rotation. The piston will traverse up and down with application of a burst of comp. air at the upper and lower intake ports. Cylinder is cast iron, frame and flywheel are aluminum. I suspect the cylinder is a Stuart product as it had a S cast into the steam chest cover. Construction of the slide valve first try was based on the poor BP's which didn't come anyway near correct. I redesigned the slide valve incorrectly as it still won't run. When air is applied you get full output thru the external exhaust port, the slide valve has no effect whatsoever. My theory is that I have made the slide valve opening TOO large and all the applied comp air is directed to the exhaust port due to being grossly oversize. Have done a comparison with another casting BP set for a similar vertical type of engine and determined that the slide valve cavity area is approximately 66% of the port opening area consisting of the upper & lower intake openings and the center exhaust area. I am wondering if this ratio is correct or suitable in applying to my errant engine project? Any insight members could share would be appreciated.
As you might guess I won't be purchasing any additional casting & BP's from that supplier again as his promises for an updated and correct BP's have not materialized. Nothing quite like being left in a lurch situation and basically having to design as you go to achieve a running engine! If any of you are interested in who this less than creditable supplier is PM me and I will be glad to share that information with you.
chucketn:
I may have some design info in my notes. I'll check. Meanwhile what do you mean by BP?
I am currently redrawing some engines in Fusion to make 3d printed patterns to cast. Lots of fun and learning a lot more than I ever dreamed...
Jasonb:
BP = Blue Prints
Can you give the cylinder bore and stroke, then one of us may have the details of that particular Stuart engine and could help with valve size and eccentric stroke. I would not size the valve by area but by the spacing of the inlet and exhaust ports.
Maryak:
If the ports are already cast into the cylinder it is possible that a bad casting would give rise to the inlet and exhaust ports being connected, i.e. the vital bit of metal separating the two is missing or broken inside the block.
This may be your problem as you have full exhaust pressure when applying air to the inlet port(s), when you should have no pressure from the exhaust port, i.e all the air should be going to the cylinder.
HTH
Regards Bob
Tennessee Whiskey:
Great info in this video
http://www.youtube.com/watch?v=ggd2sOc36GQ
Eric
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