Oscillator Cylinder Pattern

[vtsteam]

After receiving and looking over the #12 fasteners, I decided I didn't like the size, and went with #10s after all. I think they have a axial shear of something like 100 lbs each, and the exposed surface of the end covers is about 1-3/4 sq in. At even 100 psi, that's only 175 lbs of force, and there are 6 screws, so it seems well within range, as Jason suggested earlier.

So I basically glued the end covers onto a block of wood, which I had earlier turned, faced and installed a guide pin in to fit my recently made simple rotary table for the drill press. The wood block had a turned recess to closely fit the raised inner boss of the covers. This and the pin centralized and locked the positions of the covers on the table. A simple index of a strip of paper on the circumference of the table had 12 divisions, of which I used 6 to drill the cover's holes. I started with a spotting drill, then a tapping diameter size drill, a #20.

After those were done, I transferred those holes to the cylinder and drilled them the same size. Next came tapping the cylinder, and finally opening the cover holes to #7 for clearance, I used some large washers as furniture to space the covers off of the table the thickness of the inner boss.

Finally, I had some #10 socket head cap screws on hand so I assembled the cylinder with those to have a look at the parts finally together.

[Sanjay F]

All that work has paid off, it's looking mighty fine 

[PaulR]

That's one solid piece of engineering   

Love the simple rotary table idea!

[CI]

Looks great; I can almost hear it running.
.

[vtsteam]

Thanks Sanjay! 

Thanks Paul, the rotary table is just a copy of Dave Gingery's version in his Shop Notebook book. Well mine is an enlarged version -- 5" instead of 3". I made it out of scrap. in fact the aluminum table was already partially swiss-cheesed with holes, which I filled with JBKwik epoxy. I got it as a piece of waste aluminum from a place where I used to work. 

Thanks CI, I sure hope it does! 

I had an amazing morning! People at the coffee shop I often visit mornings got wind of my engine building, in fact I brought in the cylinder for our friendly regulars "show and tell" a week ago. Word got around, and I was invited out to a nearby lumber mill to meet the owner who had a defunct steam engine (supposedly). So this morning I went there with a mutual friend who arranged the visit, and WOW, yes indeed there was a big Westinghouse style twin (a long time interest of mine) steam engine AND a steam turbine, both normally driving 1500kW generators, and both down. The Westinghouse twin was super interesting, in that it was both double acting AND unaflow. I measured a piston which had been removed, and it was 14-1/2" diameter.

The owner actually asked me if I would work on it. I'm considering that right now. Unbelievable......

btw.. Below is one of two Westinghouse twin full size engines that I own, which I intended to restore into one working engine. But they are dwarfed by the one I just looked at today.

[vtsteam]

Paul, if you're interested here's details of the rotary table made from scrap. Important that the central stepped arbor (steel) pressed in place has a true hole (I drilled undersize and used a .251" reamer) to accept arbors and adapters.

In my case 1/4" drill rod made a good peg when using a wooden sacrificial piece. Or you could just Swiss cheese the table as disposable and replaceable.

The square steel tail piece is easily clamped in a drill press vise when in use.

[CI]

That is a very nice small Westinghouse engine !
I hope you got photos of the large Westinghouse.
I don't think I have seen a twin uniflow before.
.

[PaulR]

Paul, if you're interested here's details of the rotary table made from scrap.

Thanks very much  When I come across a suitably large piece of scrap I'll definitely make one of those.

[vtsteam]

CI I didn't get photos -- I had forgotten my phone, and I was too busy talking to and fielding questions from the owner and the head of sawmill operations -- an hour went by like a minute -- I was just marveling that such a thing could exist nearby to me that I was completely unaware of AND that someone would even want it operational, rather than condemning it to scrap. What are the odds? I have been fascinated by Westinghouse and Unaflow types for over 20 years... below is a pic of some of my engines and my castings, for those types. Right now I'm still kind of mind boggled about this!

CI I will get photos next time I visit. 

Paul, great- I'm sure you'll do a nicer job of it than my quickly assembled expedient for this job.

[vtsteam]

Back from the distraction of a "real" steam engine..... to the world of a 1-1/2" bore. I turned a piston up out of material on hand from a casting session riser. First to rough overall dimensions and then tapped the center 5/16"-18 tpi. Then I parted it off.

I then threaded the end of a piece of 5/16" drill rod to fit and screwed the two together. The piston rod with piston attached was then mounted in the lathe chuck, and both ends of the piston were cleaned up with a parting tool, bringing the final piston width down to 5/8" final. The piston diameter was then turned down to a close sliding fit to the cylinder. I added a thin jamb nut to the end and tried it out in the cylinder with the covers on.

With no lubrication, gaskets, packing or rings, the piston will fall the 2-1/4" stroke of its own weight, and take a consistent 12 seconds to do that.

I had originally thought about making CI rings for it, but I'm considering just trying V-groove labyrinth seals for the piston. Both the cylinder and piston are iron, so  temperature expansion should be pretty much the same. Might just give it a try. (btw, I do know about O-rings, but I just wanted to go full metal on this one).

Anyway, progress,,,

[PaulR]

With no lubrication, gaskets, packing or rings, the piston will fall the 2-1/4" stroke of its own weight, and take a consistent 12 seconds to do that.

Wow, that must be a good fit. The chunky nut on the end of the piston rod looks like the whole thing means business!  Really looking forward to see this engine complete

[vtsteam]

Thanks Paul.    I've been trying to research just what size would be appropriate for these labyrinth grooves. There's really nothing I can find about them. In fact it seems that on many model steam engines with grooves, nothing is specified at all, and very little about pistons, except the comment "Turn them to size on the drawing, and turn the ring lands (or packing groove)...etc.

Best I can find so far is from Elmer Verburg's engines -- all the smaller ones specify grooves .010" wide and .005" deep. And in the drawings they look to be Vee grooves, rather than square. That means an approximately 90 degree Vee, so that's easy.

On a somewhat larger bore engine (0.875") he specs .015" x .007". I'm going to guess that on a 1.5" bore he'd have used .020: x 010" so  that's what I'll try.

This should be interesting because I already know that the piston descends in 12 seconds consistently. So what will the difference of adding the grooves make? Will it drop slower, the same or worse? Of course I'm hoping for better compression, which is why I'm doing it.

Then, Elmer calls them "oil rings" and perhaps that's the main reason for them, but this experiment will be done dry, and we'll find out if the claims for "labyrinth packing" hold true, in this case.

Fun to learn stuff by doing.....

[Jasonb]

I don't do anything special size wise for oil grooves which I tend to use on the smaller engines 16mm bore or less. Just what looks right using a pointed tool.

12seconds, I can beat that. No oil and just holding te hcylinder on a flat surface.

<a href="https://www.youtube.com/watch?v=Vp2Vrq1Ziw4" target="_blank">http://www.youtube.com/watch?v=Vp2Vrq1Ziw4</a>

[PaulR]

I don't do anything special size wise for oil grooves which I tend to use on the smaller engines 16mm bore or less. Just what looks right using a pointed tool.

12seconds, I can beat that. No oil and just holding te hcylinder on a flat surface.

<a href="https://www.youtube.com/watch?v=Vp2Vrq1Ziw4" target="_blank">http://www.youtube.com/watch?v=Vp2Vrq1Ziw4</a>

Impressive... you didn't slow down the video did you? 

[vtsteam]

And the answer is.........

No difference. Twelve seconds it is.

I've done better, too, for hot air engines, lapped brass bore, and graphite piston, pretty much indefinite period. But in this case this was just a homemade boring bar, homemade boring table, homemade lathe, homemade castings, homemade boring gauge, no DRO, no lapping, just twiddled the handwheels... and an addition of 20% luck! 

re. those grooves, and some caveats about functionality. These seals are dynamic, so the present rate of descent is a tiny fraction of the running rate, and the pressure differential in the groove is going to reflect that. At 1000 RPM that piston will be moving on average roughly 400 times as fast as it is in my so-called "experiment". Second, the effect of oil on the seals.

But I was curious to see if it did have an effect even now. Which it didn't. Fun anyway!