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Old 10-11-2017, 10:51 AM   #111
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Brian,

What size of lathe do you have? That picture makes your con-rod look huge, but you said the engine was tiny. I'm trying to get a sense of scale.

Thanks,

...Ved.


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Old 10-11-2017, 01:21 PM   #112
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The full length of that con rod including the bolt on end-cap is 2.3" long. The lathe chuck is 6" diameter,


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Old 10-12-2017, 10:41 PM   #113
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I'm now into "second set-up" with the con-rods, machining the other side. Same fixture, but with a spacer washer of appropriate thickness between the finished big end boss and the fixture. The fixture is very handy for this kind of work. I know it doesn't look terribly different from the previous picture. After this operation is performed on both rods, then I have only to round the small ends and do a little "clean up" with my jewellers files.
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Old 10-13-2017, 07:11 PM   #114
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Today I finished the con rods. They turned out quite well. No, it isn't your eyes, that gudgeon pin hole in one of the rods is off center a bit. It won't affect how the con rod works, and if it is hugely visible when everything is assembled, I may make a replacement. It has burned about 8 hours of my time making these two.
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Old 10-14-2017, 11:04 PM   #115
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Okay--I have to say it--I'm stoked!!! It has been a long and busy day, but the first stage of assembly has been a great success. I completed the cross heads and "dummied up" a set of cross pins to connect the cross-heads to the connecting rods. I completed the bottom ends of the cylinders, with an integrated "guide/seal" on the underside to guide and seal the piston rod. Everything rotates and clears everything else. The engine is still a bit stiff, that is why the big V pulley is there. It lets me rotate the engine carefully and slowly by hand to check for clearance issues. The little 2" flywheel doesn't give me enough mechanical advantage to do this comfortably. Tomorrow, I will machine the pistons and piston rods, and try to get a video up showing the operation of the assembled parts so far.
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Old 10-15-2017, 11:18 AM   #116
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Today we're going to change things up a bit from the original Stuart engine. The piston will have one 1/16" diameter Viton o-ring. The piston rod is going to increase from 0.156" dia. up to .188" diameter (because I have a ton of 3/16" cold rolled), and there will be no threads at either end. The piston rod will be fitted into reamed holes in both piston and cross head and silver soldered in place. Of course this means that the bottom cylinder cover must be finished and placed on the piston rod before the ends are soldered in place, as it can not be installed afterwards.
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Old 10-15-2017, 11:40 AM   #117
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Quote:
Originally Posted by Brian Rupnow View Post
The piston rod will be fitted into reamed holes in both piston and cross head and silver soldered in place. Of course this means that the bottom cylinder cover must be finished and placed on the piston rod before the ends are soldered in place, as it can not be installed afterwards.
In my Stuart D10 the piston is fixed to piston rod while the piston rod is screwed to cross head. It will be practical to unscrew the piston rod from cross head when it is need to replace the worned O-ring with a new O-ring when the cylinder head is dismantled.

A question: No cland box gasked in the bottom cover?

The brass/bronze (bottom cover) will expand more than the steel (piston rod) who lead to more leakage. In my Stuart D10 the cland box is packed with graphite yarn who last very long time. O-ring as gasked in gland box works well too.
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Old 10-15-2017, 12:34 PM   #118
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I find that I have trouble with alignment on parts assembled with small diameter short threads. A reamed hole ensures my alignment. There is no gland nut on the bottom of the cylinder plate, as this engine will be ran on compressed air, not steam. A reamed fit and a bit of oil gives all the sealing required. There will be no heat, so I'm not worried about differential expansion factors.---Brian
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Old 10-15-2017, 05:23 PM   #119
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As I promised, here is a YouTube video of the engine to date, and a top view, showing the soldered piston to piston rod connection. I noticed after watching the video that I called the pistons --cylinders, so be forewarned.
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Old 10-15-2017, 09:54 PM   #120
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Looking good Brian.


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