Hi Tom,
Thanks for responding. Clearly you know a lot about steam engines. I hope you'll give me a little leeway for not describing *everything* about the engine here in a public post. The 200:1 ratio I spoke of is simply the ratio of the volumes at BDC/TDC. I'm sorry if I seemed to imply that the I'd be trying to obtain a 200:1 expansion ration of the working charge.
If we apply the combined gas laws the pressures & temperatures are so far off the chart as to be ridiculous.
Again the valve plenums are essentially sealed, and so the net forces on the valve cones should be proportional to the port areas only, with the gas-bearing area being many times the area of the ports.
The whole point of the valve plenum is to create infinitely variable valve timing of both angle & duration. Sure It's not going to be efficient at 90 degrees of admittance and 2:1 expansion, but I would expect it to make power like a hydraulic motor under those conditions. Somewhere inbetween there is an optimum. Fortunately the valve is under ECU (computer) control, so anything from full power forward to 100% reverse is simply a matter of computation. There are no mechanical considerations like conventional steam-chest a sliding valve or even the linkages of the 'Silent-Knight' rotating & nutating valve have to deal with. It's pure rotary motion.
I do get what you mean by comparing indexing to decking a bank of using gang-drills to punch 30 odd holes in one stroke. But it'll be a while before mass production bottlenecks are the long pole in the tent.
Why no master rod? Because as you were quick to recognize it a two-stroke and I'm planning on an even number of cylinders. And the master introduces variations in the piston speed depending on the cylinder number. In order to compensate for that the valves would be required to vary the phase angle of the cutoff & duration six times per revolution. That would require a colossal data table of empirical coefficients to correct. Besides the four-bar has an excellent reputation for reliability in stationary engines. The master rod's greatest advantage was in its weight savings according to P&W's testimony.
And in case I neglected to mention it, the 'block' and the cylinders are separate parts. The block is little more than a 12 sided nut with cross-drilled holes. Most of my designs start with a stubby section of DOM tubing, which gets faced off to length in a lathe. The length tolerance is the axial tolerance of the shaft in its bearings, again it can be quite loose and not cause any more trouble than requiring a washer or shim. Then that simple symmetrical nipple has the 12 flats machined onto its OD, and gets 12 kisses from the boring bar, and a chamfer. For the purposes of the prototype, a CNC machine with a rotary indexer in good working order is more than tight enough tolerance wise. The thermal expansion of the engine core will be many times the tolerance of the machining requirements.
FWIW I'd've claimed the _static_ volumetric ration was >200:1 but I left a big thick clearance between the piston & the head at TDC because I want to *measure* what the actual clearance diminishes to as the parts warm up. It all depends on how much the connecting rods stretch at high speeds. I might be able to get the squish area of the head down to 0.015" (4/0.015 = 266:1), but as I pointed out that's a heavily diminishing return.
I can understand why you would be concerned about extreme tolerances. Cyclone made a couple of fundamental choices that only make sense if one can maintain incredible precision matches. The spider & the super critical injector valves. Both of those choices required one thing to push against another thing. If only he had used 'unobtanium' it might have held together.
So just like I used to advise my junior programmers "Don't write clever code. White clear code. Someone else will be maintaining it." I took that advice to heart when I designed the engine. Yes, the 4-bar is a bit more complex than the master rod, but no one gets past "Mec.Eng.-101" without understand it. And by analogy my valve is as simple as a "4-5 siren" compared to a set of diesel injectors for Cyclone.
I had planned to build this a long time ago. I even bought a CNC machine shop to accomplish the task, but then I lost the use of my arm, then the recession hit, and after that I had to sell the shop. But I did put my kids through college, and handled the other things. Now I'm in Florida and I want to jump on (well, ease into anyway) that saddle again.
Thanks for your time. I do appreciate your comments. It's getting me to think about the multitude of details again. Helps to to limber up my muscle memory (if you will).
Best,
--Paul
