Greene Automatic Cutoff Steam Engine

[crueby]

Fantastic looking parts - hard to tell they are a scale model not the full size!   

[kvom]

Bit more progress over the past few days.  I decided to try to save the exhaust bracket that I had messed up since I had no more of the 2" cast iron rod it was made from.  Remade the bearing cap, and was able to tap the mounting holes in the bracket well enough to old it.  I decided that in the worst case I could just loctite the two pieces and the bushing together.

It seems I hadn't finished the tiny "turnbuckle" used for fine adjustments of valve travel.  I had thread milled the left and right hand threads, but on a length of .099" drill rod that was too long.  Trimmed the right hand thread end to length and threaded with a die.  Then drilled a 3-48 nut and used loctite to secure it in the center.



Still needed to drill the clevis for set screws, but after that I could assemble the mechanism.  It's the same as the other but bracket is a mirror image.



Test fit to the cylinder block:



The ends of the two 3/16" rods that will be connected via a coupler are probably out of line by less than 20 thou before trying any shims.

Although I need disassembly/adjustment on the crankshaft end,   I'm not far from trying to get the first run.  I need to think about how to time the valves; since they are independent, it's not like a slide valve where you just have sync the valve and piston rods.  Does the MEM corliss plan have anything written about timing it?  Should be similar.  One issue is whether the weight of the dash pot pistons will be enough to close the input valves.  On the completed engine these are "assisted" by a spring below the base.

I ordered some Buna-N round and square o-ring material to see if I can build a workable belt to drive the governor. 

The good news is that the parts drawer seems only to have governor parts left.

[kvom]

A few hours spent doing some last minute fettling on some parts, and then putting it all together:  first time all the major assemblies together.



Still a lot of adjusting to go before I can think of a test run. Issues evident from today:

- Slide needs centering.

- Crank side exhaust valve assembly motion is stiff.  Might need to shave the sliding grid a hair.

- Rod that links exhaust assemblies won't go into the coupler.  Thinking I'll open up the coupler a bit or move set screws closer to the end.

- Dash pot weight not enough to close inlet valves.  I may put temporary weight on each.

No rush to get it running as the pandemic has a ways to run.
-

[crueby]

Wonderful to see it assembled, quite a pretty engine.
 

[fumopuc]

Hi Kirk, impressive.

[Craig DeShong]

Looks impressive Kirk, can’t wait to see it run !

[Dennis]

Hi Kirk.
Your model is looking very nice.  I am looking forward to the first running like all of the others following this build.  You have made a lot of progress on this build the last few months.

Getting all of the valves and valve gear adjusted will take some time and patience.  There are so many things moving at the same time, it is difficult to get it all coordinated.  At one time there was a step by step instruction sheet to guide you through the valve setting and adjustments but I could not find a copy it my computer files.  I will continue to look for it.  From my experience with this model, by the time you are finished making the adjustments you will have a new understanding of Nathanial Green's design. 

I believe Green was a very good engineer as was George Corliss.  Many people have read about the patent war between Corliss and Green's backers, however the court battle was not about steeling a CUT OFF VALVE DESIGN.  The court case was really about what could be patented or IF THE IDEA OF VARIABLE CUT OFF could be patented regardless of the mechanism used to accomplish the cut off. 

Maybe you should build a corliss valve gear engine now so you have the whole story.
Dennis

[kvom]

Rather than starting to fiddle with adjustments, I decided to do a bit more with the flywheel.  Since I am now able to run the 10EE in reverse for the first time ever (thanks to help from the Monarch section of PM), I now had the ability to turn across the full width of the wheel in one pass.  This was done by using a boring bar turned upside down.

I also removed the hole in the rim by facing off about .3" of the rim, which eliminated the connecting gaps in both the outer and side faces.  That said, I still need to do some finish lathe work using a sturdier way of holding it.  I used two difference mandrels, but still get wobble on the outer edges because of the weight of the wheel.  So I intend to make a new mandel that is supported by a tailstock center.

As for setting the input valves, these are a bit easier.  My normal approach for D valves is for the input to be full open when the piston is at midpoint in the cylinder.  This should mean that the opposite exhaust valve is fully open at that point as well. 

One peculiarity I discovered by mental review is that the oscillating activating rod means the exhaust valves act differently in an important way.  When the rod is rotating in one sense it is acting on both valves.  Thus both will either  be pushing into the cylinder or pulled outward.

After writing the above, I watched John's video again and can see that clevises are angled in opposite directions, and this in turn causes opposite motions.  That simplifies things a good bit. 

Since pushing one open means pushing the other closed, the two sliding grates need to be offset internally by the width of the grate opening or a bit more.  The openings are .08" wide and separated by .115".  So if I can determine when then valve should be open and can then position it, as long as it moves forward or back by > .08" I should be good.

By removing the valve cover on the opposite side, I can see the ends of both the fixed and sliding grates.  If the ends are even, then the openings are aligned and the valve is open.  I could also used a depth mike to measure the offset between the two.

[kvom]

Maybe you should build a corliss valve gear engine now so you have the whole story.
Dennis

Trying to presell a set of Lane & Bodley castings?   

[Dennis]

Hi Kirk,
Sorry if I offended anyone, as I re-read the posting, it does look like a sales pitch and I apologize for that.  It was not my intention.

The L&B engine is a fine model but as you know we sold our model business several years ago.  My interest in steam power has shifted to the history of these engines and the people who developed them. 

The history of steam power is a fascinating thing to study.  There are people, technology, manufacturing processes and new ideas that pave the way for more improvements in designs.  Sandy and I spent a lot of time (and money) collecting information and taking photos of stationary steam engines.  We have detailed photos of several hundred stationary engines and had planned to put them into a book that showed the progress of stationary engine design over the years.  The Henry Ford Museum and several small museums gave us permission to publish the photos we took of their engines without paying royalties on the published photos.  However, many of the photos were taken at museums which require a large royalty for permission to use photos of engines they own, even if you take the photos yourself.  That is understandable because the museums all have to support their exhibits and pay the people who care for them, however, the royalties would increase the estimated cost of our book to over $100 per copy which we felt was unreasonable and unsellable to recover the cost of publishing.  Presently, about 600 pages of the manuscript sit on a shelf in my den where I work on it occasionally just for the personal enjoyment, and it is well worth the effort and cost.

Dennis

[kvom]

My intent was jocular.   

[kvom]

After some fettling I was able to get the valves operating as I turned the flywheel.

<a href="https://www.youtube.com/watch?v=cG82Cbpmq_s" target="_blank">http://www.youtube.com/watch?v=cG82Cbpmq_s</a>

[crueby]

Awesome!!  How long to a test run?   

[kvom]

Nothing stopping me now but fear of failure.   

[kvom]

I made the first attempt at setting the valves this afternoon.  Applied air and ....


Nada!!   

At 50 psi on the valve meter I could detect only a very light breeze coming from the exhaust opening in the bottom of the cylinder block.  Unfortunately the push connector I installed is 1/8" NPT and 1/8" OD tubing.  So air volume is likely way short of what's needed.  I ordered a connector for 1/5" tube from McMaster that will ship Monday.

I couldn't feel the slightest kick from either side, so there's a fair chance that the exhaust valves aren't sealing completely.