Author Topic: Greene Automatic Cutoff Steam Engine  (Read 9401 times)

Online kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #105 on: July 12, 2019, 12:00:27 AM »
So I was mistaken about the name of this part.  I read it as "device" mainly because the font used in Solidworks made the cl combo read as d.  In reality it was clevice which is actually clevis misspelled.  I didn't want to call it a device so just called it a swing arm.  Now that that's out of the way, let's finish it up.

I machined a soft jaw pocket matching the outer profile .3" deep, and after parting each clevis off the parent stock I was able to machine the opposite side.



After drilling the hole for the control rod, we're finished for now.  These will need a set screw or two to attach to the rod.  The cad model shows a through hole implying two on opposite sides, but it seems to me that with the clevis in place on the engine the inner screw could be hard to access.  So I'm leaving these undrilled for now.

Here's the clevis shown in relation to the other completed parts.


Online kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #106 on: July 12, 2019, 10:48:15 PM »
Now that I have an endmill with 2" flute length, it's back to try again;  this time milling the two main profiles top down.  Starting with 2.5" length of 1.75" round grey iron with reamed .501" hole 1.7" deep in the center.  I turned the bottom  down to 1.125" and milled a soft jaw pocket to match.

The first profile just defines the bottom mounting face of the bracket. Milled 1.9" deep.



Not the greatest surface finish, so on the second profile I did two passes with a .005" roughing clearance on the first pass.  Then the second profile, also with a roughing and finishing pass.



The other bracket is the same but with the second profile mirrored around the Y axis.



Next ops will be to finish the bottom;  hopefully I'll finish both parts entirely next time in the shop.


Online kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #107 on: July 13, 2019, 11:17:01 PM »
More progress on the brackets.  I used the CNC mill to finish the inside (relative to the cylinder block).  The following photo shows how the bracket for the cylinder cover side would be mounted.



The onto the Bridgeport to drill and tap holes for the bearing cap, to be made next.



Then mill the edges of the hole and drill and oil hole.



I was very happy to get to this point without screwing up.


Online kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #108 on: July 19, 2019, 12:48:09 AM »
Having discovered the misspelling of clevis in SW, I saw that there are 4 more needed.  The overall dimensions are identical other than the fact that they are connected to rod ends of different diameter, hence the hole on the small end is larger.

I had ordered some 1144 stressproof rods from McMaster, and the steel I made the exhaust clevises from is not that.  The finish on these is a lot better.  I cleaned up CAM for the first ops, but otherwise pretty similar to the prior parts.



With 4 of them to do, this time I'm letting the computer cut the slots.



So here they are waiting for the next ops.  I'm looking to make a fixture for turning the barrel versus messing with the 4 jaw to center it.


Online crueby

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Re: Greene Automatic Cutoff Steam Engine
« Reply #109 on: July 19, 2019, 01:01:40 AM »
Great work, following along...

Online kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #110 on: July 20, 2019, 10:06:42 PM »
Thanks for looking in Chris.

Today's goal was to finish the 4 clevises, which when we left them were still attached to the ends of the 1" rods.  The first order of business was to drill and tap for 3-48 grub screws





Since I've not machined over or removed the soft jaws on the CNC mill's vise, I can re-use the profile pocket as long as I can recover the XY zeros.  My mill doesn't have working limit switches;  if it did I could have recorded the machine coords.  In this case I had the finished exhaust clevises, so I placed one in the pocket and used this pointed wiggler.



By jogging until the head was smooth to the barrell all around, I can expect accuracy of better than .002 in either direction.  Then I parted off the 4 clevis ends leaving ~5/8" of extra rod.  Then placed the clevis into the soft jaws, I could mill a 1/2" boss centered on the large end of the clevis.



Then I could mount the part on the lathe using a 1/2" collet.  This allowed me to this form the inside diameter:



And then to drill and ream for a 3/16" rod.



Then it was back the mill to use the soft jaws and mill away the remaining material and finish the "back" of each clevis.  The four are now done other then some buffing/deburring.  Todays' sessions was nearly 5 hours, longer than my usual.  If I had to make a few hundred of these I'd need to find more efficient methods.


Online kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #111 on: July 29, 2019, 04:06:58 AM »
After a mini-vacation in Las Vegas, I was back in the shop today to start on the bearing brackets that support the two parallel rods on which the 4 clevises made previously are attached.  One pair of clevises activates the input valves and the other two attach the dash pots.

Starting with 6" length of 1" diameter stressproof rod, I milled 4 sides of the rod to obtain a rectangular bar .75" wide and .5" thick.  The CNC mill then machined the profiles of the 4 parts .22" deep.



Then on the Bridgeport  I milled away the bottom stock to free the parts.



Still a few manual ops tomorrow to complete these.  So far about 95% of the original bar is chips.

Online kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #112 on: July 30, 2019, 12:18:15 AM »
In order to drill the center mounting hole vertically through a bracket and its cap, the two must be aligned precisely.  Here's the method I came up with.

First, align as closely as possible by eye and clamp together in the small machinist vise.  Then face mill to ensure that the two sides of both parts are parallel.



Then ream the two bearing holes 5/16.



After this, I used my new sonic cleaner to remove any oil or dirt.  I then cut 4 pieces of 5/16" drill rod to serve as alignment fixtures while the two parts are fastened together with Gorilla Glue (cyanoacrylate).



Next time out I'll drill the center holes for 3-48 body screws and 1/16 oil holes for the bearings.

Online kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #113 on: July 30, 2019, 11:55:27 PM »
These brackets are proving trickier all the time.  After the glue cured overnight, I went about drilling the holes.  The smaller bracket went OK, but here the drill wandered.   :(



It's possible I didn't make the spotting drill hole large enough.  The camera color came out a bit weird, but the sonic cleaner leaves the steel with a greyish patina that comes off with a light rub of 1000 paper.  The steel seems to want to rust when cleaned though.

I don't want to cut another piece of stressproof right now and will wait until I have some other parts that can use the same size.

As consolation I spent the rest of the afternoon making the rod ends for the rods that suspend the dash pots.  Each pair has one 3-48 RH and one LH, so that turning the rod can adjust the height of the pots.


Offline Craig DeShong

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Re: Greene Automatic Cutoff Steam Engine
« Reply #114 on: July 31, 2019, 09:47:33 PM »
Hi Kirk,  just getting caught up on this build.  Was sorry to see the problems you were having with the cylinder casting, sort of reminicent of the head problems I had with the Frisco build.  Hope you get a replacement casting you can work with.  The Clevises look terrific.  Great work here.
Craig

Offline steam guy willy

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Re: Greene Automatic Cutoff Steam Engine
« Reply #115 on: July 31, 2019, 11:58:17 PM »
Hi Craig, Following along, and that is an interesting rule you have,,divided into 50ths..! i have seen  8ths 16ths  and 10ths and 100ths but never 50ths..?? is there a special reason for this ? 

willy

Online kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #116 on: August 01, 2019, 03:12:17 AM »
The rule is one of many I have picked up over many shows.  I could never find a rule when I was looking, so now with 20 or so scattered over the shop I can usually lay my hands on one.  No idea why the maker of this one chose 32nds.

Today I made the dash pot connecting rods.  Cut the two rods to length on the lathe using DRO to measure and my $90 Hardinge collet to hold it while I parted them.  Then thread milled the two ends of each.  After drilling out the threads of two 3-48 nuts, I glued them onto the rods.



The rod ends needed to be bought to 3/16 thickness.  With a clevis one one end, here's the assemblies:


Online kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #117 on: August 02, 2019, 12:40:30 AM »
Continuing on with the inlet, this shows the parts involved:



The clevis mounts on a rod that oscillates as directed by the eccentric and cutoff mechanisms.  The small end is connected to a sort of die block that sides vertically in a slot in the blue part, which serves as a crosshead.  This in turn connects to the valve via the valve stem.  The stem is 1/8" in diameter and has .8" of 5-40 thread .  For timing, the angle of the clevis on the rod determines the total stroke of the valve.  Once set, the 3 nuts on the stem adjust the proper position the of the valve.

To keep everything aligned, the valve slides in a groove and also is constrained by the steam chest cover.

My shop job for the day was to make the simple valve stems, with .8" of thread on one end and .2" on the other.  Decided to thread mill these as my mill was already set up.  Probably silly as I spent over an hour developing the code to cut the long thread.

Online kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #118 on: August 02, 2019, 11:42:43 PM »
For the slider block, mill the profiles in some 1144 steel.



To remove the bottom waste, this is one of my favorite methods.  Better finish the  from the tip of an endmill.



Drill and tap the hole for the valve stem.



With valve stem attached.



Machine profiles of the die block on the end of some 75" bronze rod.



After separating from the stock and fettling for fit, assembly of clevis, slider, and die block.


Online kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #119 on: August 03, 2019, 06:28:12 PM »
Today's work will be to start on the dashpot canister.  Here's a transparent view.



The dashpot cylinder slides within the cavity, and is attached by a rod to the inlet mechanism. At cutoff, the cylinder pulls the valve shut.  On a full size engine, there's a close fit, and when the cylinder is raised a vacuum forms in the canister.  This plus the weight of the cylinder provides the force needed to close the valve.  In this model, a spring is used, so the fit of the cylinder is not as critical.

There are two castings provided for the canisters, but for me it's much easier to make them from round 1144 rod.  The two flanges fit within a 1.5" circle, and I have some 1.5" stock.