Author Topic: Greene Automatic Cutoff Steam Engine  (Read 6792 times)

Offline kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #120 on: August 04, 2019, 02:31:57 AM »
Start with some 1.5" rod in the lathe, face, and skim turn to get the initial diameter which is used to set the DRO.



Then turn down to .850" diameter for a length of .675.



Drill a centerline hole .144" (#27) through (1" depth) here.  Then use .5" endmill in the tailstock to rough out the cylinder bore, and finish with boring bar; final diameter .575".



Using a parting tool, machine inner diameter to .75".



Then part off.  The canister is not difficult to chuck for the remaining ops, so I turned a 5/8" aluminum bar to a close fit to the canister bore and glued it in.  Subsequent ops will use a 5/8" collet and collet block to hold the piece.  At the end a blast from a torch will free the plug.



Next shop session I'll finish these and start on the pots.

Offline crueby

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Re: Greene Automatic Cutoff Steam Engine
« Reply #121 on: August 04, 2019, 03:09:51 AM »
Great work, following along.   :popcorn:

Offline kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #122 on: August 06, 2019, 10:55:56 PM »
I had a couple of days of frustration trying to finish the first canister.  The aluminum plus glued into the bore didn't hold properly, and the piece rotated ruining it while machining the base.  I tried Loctite instead of glue and that also failed.  I probably would have succeeded with a miniscule DOC.  So one of them was ruined, and I tried to come up with a way to hold it securely to mill out the bottom profile.  Eventually did this:



Three pieces of 3/16" square brass glued to the tips of chuck jaws fit into the recessed diameter and allowed a very firm hold.

For the pistons, I turned some 3/4" brass rod down to 5/8".  Then drilled and tapped one end 5-40, and parted off a 1" length.  The opposite end was drilled for a cross pin (to attach the rod end), two 3-48 set screws, and a pocket.



The bottom end was then turned to fit the canister with a nice sliding fit.  The top end was similarly turned down, and a grooving tool used form the bands.





The partial assembly to the rod:



Now I need to make another canister.

Offline kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #123 on: August 10, 2019, 09:42:23 PM »
I came up with a better sequence of ops for the canister.  After the manual turning and boring, the flange is machined on the CNC mill.



Then back to the lathe to groove the cylinder relief, and finally part off.  To clean up the bottom the lathe chuck gave a good enough hold so that facing with small DOC gave no problems.

Now I could finish the piston the same way as the first, turning to get a good sliding fit.



With these done, my next part to attack is the slide shelf.



The overall dimensions are 2.5"x1"x.8".  To make a start, I cut down a 2.5" length of stressproof into a block slightly larger in the other two dimensions.



Most of the ops on this part will be manual on the Bridgeport.

Offline kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #124 on: August 12, 2019, 01:50:50 AM »
Today I reduced the block to the required dimensions on all three axes, then cut the three reliefs.



Then on to the CNC  mill where the large front pocket was milled .6" deep.  I used a 3/8" roughing mill followed by a 1/4" finishing pass.  Then spot drilled and drilled the 5 holes needed on this face.



Next time I'll finish with drilling in the top and the smaller pocket from the rear.

Offline kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #125 on: August 13, 2019, 08:45:15 PM »
I finished up the shelf yesterday, mostly drilling and tapping.



I was intending to continue with the slide.  But rather than continue to carve flat sheet from round bar, I decided to order some 1/8 and 1/4 inch sheet A1 tool steel from MSC for these flat parts.  In the interim, I attacked the small part shown in red here:



The view here is the bottom of the cutoff assembly.  The shelf is a light brown and the slide is grey.  The input from the governor is a rod that activates a cammed vertical motion of the rod that is attached to our red piece.  As the rod moves vertically, so does the part that engages its slot.  This part in turn is attached to the tappets via holes in the slide.  As the slide moves back and forth the tappets remain at a constant height as long as the slot has a good sliding fit that inhibits any vertical movement.

The dimensions of this "slide bracket"  fit within a 1/2" bounding circle, so I could mill the sides on the end of a piece of 1/2" drill rod.



Then reorient the collet block to mill the slot.  I used a 3/32" endmill, slightly smaller than the called for .10" slot width;  but a good fit with its partner is more critical than the dimension.



Then part of on the lathe and bring the cut off side to dimension.




Offline kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #126 on: August 16, 2019, 02:21:47 AM »
Made the simple slide today.  It took a bit of work, but finally got a good sliding fit with the previous part.



I found a piece of 2" diameter steel rod in the shop, and am pretty sure it is left over 1144 from when I made the Joy engine conrods.  In any case I cut off a few inches, faced both ends, and machined the profiles for the input valve bracket replacement for the one ruined by a wandering drill bit.



To free it from the stock, I needed to part it off.  Doing this in a single deep groove is tough, and I was getting a lot of chatter and complaining from the lathe.  Solution is to cut a groove 1.5 time the width  of the parting tool, and go alternately a short depth from each side.  Tomorrow I'll machine off the backing material and hope to have better luck finishing it.

Offline kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #127 on: August 19, 2019, 12:38:42 AM »
I got the bracket and clamp separated from the root stock and glued up, but am waiting for a new #37 drill bit before proceeding. 



In the meantime I attacked the "trips";  these are the two parts that stand proud of the slide and activate the valves as the slide goes from side to side.  Their height above the slide is controlled by the governor.  Above a certain height the mating catch cannot slide over its trip, and no cutoff occurs.   To begin I chucked a piece of 3/8" drill rod, faced the end, and drilled/tapped for 3-48.  Then turned down to .187" for a length of .675" according to plans.



Checked the fit with the reamed holes in the slide.  The left the lathe setup to cut the same diameter on the other end of the stock.



Next part off and over to the CNC mill to machine the ends to a 1/4" square.



Test to check fit with the slots on the slide.



After facing to final length, the 20 degree angle is machined onto the top surface.  On the prototype engine, this face is slightly concave.



On the drawing, a threaded boss at the end is shown.  I prefer to use a screw or some threaded rod and a nut for simplicity.



I also used 3/16" as the diameter of the slide holes, thus allowing the work to be held with a 3/16" collet.

Offline kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #128 on: August 20, 2019, 01:26:05 AM »
Today's project is the "gauge plate", that attached to the front of the slide shelf.  It is slightly proud of the shelf, and hence provides a limit for the slide itself.  The markings on the plate aid in centering the back and forth motion of the slide.


Offline Captain Jerry

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Re: Greene Automatic Cutoff Steam Engine
« Reply #129 on: August 20, 2019, 01:53:09 AM »
This is the part that I have been waiting for anxiously.  Not for the complexity, but for the simplicity.  Designs that have stood the test of time usually have a common flavor of simplicity and this one is a great example of that.  Your parts are nicely made and your presentation is clear.  I believe that before final assembly, you try reversing the trips in the slide.


Jerry
There are thing that you can do and some things you can't do.
Don't worry about it. try it anyway.

Offline kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #130 on: August 20, 2019, 04:13:36 AM »
I noticed they were backwards when I took the photo.   :facepalm:

Offline Dennis

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Re: Greene Automatic Cutoff Steam Engine
« Reply #131 on: August 20, 2019, 03:29:09 PM »
Nice job on the small parts Kurt.  And a good job of explaining how the parts function in use. 
To me, Green's cut off is more rugged and positive than Corliss' cut off.  I like the simpler design of Green's cut off better than the Corliss design.

Many people are aware of the court battles between Corliss and Green's backers over the patents on cut off design.  The court decisions had a major impact on the US copywrite and patent laws and the interpretation of the laws.  I think it is also interesting to know that Green actually worked for George Corliss in the early part of his career.

Thanks again for posting your work and explaining the operation of the engine.

Dennis

Offline kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #132 on: August 21, 2019, 01:30:45 AM »
Only an hour of shop time today, so started this simple part, the "trip slide post".  It is this rod that raises the trips when it in turn is raised by action of the governor.

Plans call for .200" diameter rod.  I might have elected to use 7/32" had I planned ahead, but since the hole in the slide shelf was already drilled I ordered some drill rod of this size.  Not having a suitable 5C collet, I dug out my rubberflex collet chuck, which hasn't seen any use for quite a few years.  In reality it's a useful tool as each of the collets covers a range of diameters.  In this case, I used the 1/8-1/4 collet.

After parting off 1/25" of rod and facing the ends, I drilled one end .099" diameter x .25" deep.  A length of .099" drill rod will be loctited into the hole such that 1/2" protrudes with 1/8" of 3-48 threads.



The finishing op is a 1/16" through slot 3/8" long.  My 1/16" endmills have flute lengths that might not penetrate all the way through, so I elected to use a 5/64" endmill.  Here's the workholding setup on the CNC mill:



4-flute endmill at .02" DOC and 4 IPM feed.

Shown in position on the slide shelf:



A type of bell crank fits into the slot to move the rod up and down.