Just thought that as I'm sort of taking the day off, I'd go back in time six weeks or so and continue the saga of problems found on this "Bargain" half horse Sipp.
After finding that the crankshaft was not causing the bind, it was time to disassemble the piston rod, crosshead and open up the cylinder to find where the bind actually was coming from. As noted before, the crank rod ends seem not the issue either, and to further examine that linkage train, I will now note that the crosshead slide seems to have just about the right amount of "slop" or tolerance, to slide smoothly without binding, though the slide shoes are shimmed with gasket material to attain a closer tolerances for that clearance.
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Having disconnected that from the piston rod, next move was to open up the cylinder end cap, free the piston rod packing gland nut and back the piston out of the cylinder. While this was easily done, as it appears there was only a sleeve in the packing gland and no actual packing, it was noticed that there was more than a little drag on the movement of the piston as it was pushed back in the cylinder. So it seems that at least a goodly part of the rotational drag noted on the flywheel/crank assembly likely has the piston/cylinder as its source, so much further investigation was needed here next!
Upon opening up the cylinder and removing the piston, a couple of other telltale features were immediately noted. First, the cylinder cover bolt hole drilled and tapped just above three o'clock violates the steam passage port from the steam chest, while the next one down at about five o'clock into the rim of the cylinder, had initially been miss-located, but was caught and corrected before it had been drilled too far, or more likely the pre-assigned spot was missed to match with a misalignment in the drill holes of the cylinder end cap. Whichever is the case, something wasn't done quite right, as seen here:
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Also note in this photo, at the front end of the cylinder (rather out of focus) the drill gouge and threading marks from the large hole that was drilled and plugged into the front bottom of the cylinder for no known reason.
But an interesting aspect of this is that while that hole and plug are down at about seven o'clock in the photo, the gouge and thread marks are up at around ten o'clock, so that brass front face of the cylinder is an insert that is pressed of screwed into the cast iron cylinder casting, in order to provide for the piston rod packing gland set-up as seen here:
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Now, even at this point I'm unsure as to whether this brass packing gland assembly "insert" is just pressed in or actually threaded, but I suspect it is only an interference press fit, and will test this assumption the next time I tear the engine down. Based on the rotation of the plate on the inside of the cylinder, as evidenced by the changed location of the drill gouge, it could be either, but a press fit perhaps makes more sense, we shall see.
In any event, now knowing at least much of the drag is coming from the piston/cylinder combo, I felt it time to make do a little measuring, testing and hopefully improving any situations that were remedial in this area. Thus I measured the cylinder bore for cylindrical conformity in a couple of different ways:
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Having so measured the bore all around and in and out, I found it to be quite consistent within a couple of thousands, and believe that runout only to be caused by the roughness of the bore, due to a scale or corrosion build up mostly along the bottom 1/4 where you'd expect condensate to collect after a run. It seems likely the cylinder was originally factory bored to be this good compared to how much of the rest of the machining seems to be done. To be sure the worst of the roughness was along that bottom portion of the cylinder, but in fact all walls of the cylinder seemed to be unnaturally dark with some form of deposit or buildup, and thus I felt the next step to take of benefit, would be a bit of honing of the bore. So a lashed the engine in an end up position to the trailer hitch ball on my trucks bumper, so as to align the cylinder vertically for ease of working, and thus reducing any tendency of gravity to cause uneven honing around the bore, as seen here:
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In the last photo you can better see (now in focus) the gouge in the front plate of the cylinder left over from drilling the plug hole that can barely be seen at about seven o'clock, and how it is now rotated up to about ten o'clock. This few minutes of honing evened the bore noticeably and smoothed it to the touch as well. Perhaps I'll go another round of honing next time I have it apart, but the upshot is that clearly doing this did help materially in smoothing the engines motion.