Author Topic: Greene Automatic Cutoff Steam Engine  (Read 11180 times)

Offline jeff l

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Re: Greene Automatic Cutoff Steam Engine
« Reply #180 on: November 19, 2019, 03:13:24 AM »
So sorry to hear Kirk wish you a speedy recovery.

Offline Admiral_dk

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Re: Greene Automatic Cutoff Steam Engine
« Reply #181 on: November 19, 2019, 11:29:16 AM »
At least you got a quick diagnose and treatment  :ThumbsUp:

Wish you a speedy recovery too ...!

Per

Online kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #182 on: November 23, 2019, 10:29:56 PM »
After a week of healing, I ventured into the shop for a tricky final op on the exhaust eccentric strap.   This eccentric assembly has a swinging fork part that swings on two 1/8" pins that extend outward from the centers of the split line.  We went these pins to be clamped between the two halves of the strap.  In summary it's necessary to drill a hole that splits the split line on both ends.

I started by clamping one of the halves in the machinist vise with mounting screws inserted.  Between the surface plate and square, I ensured that both mounting faces were paralllel.



I then mounted the small vise on the Bridgeport's larger vise with its bottom against the fixed jaw.  Then an edge finder located the Y axis zero. 



I could then remove the smaller vise from the larger, I could then attach the other strap securely with nuts and return the vise to the Bridgeport.  The Y0 value won't have changed.  Then with edge finder I could find the center of the split line.



Then it remained only to spot and drill the hole.  The drill used was 7/64 as the hole will be reamed .124".  I decided against a through drill to the bottom as the drill is larger then the inner slot width.  So I turned the machinist vise over, keeping the Y0 intact, and center found the X0 point.  I repeated the drilling and was happy to see that the drill went cleanly through the first hole.  Then  reamed the holes in a single operation.


Online kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #183 on: November 25, 2019, 01:46:26 AM »
Spent a couple of shop hours turning the eccentric disk to fit the strap.  Same process as for the inlet eccentric.  This one took a lot of filing, sanding, shaving to get a halfway decent fit the strap that would turn.



After fitting the two halves of the strap together with the screws tightened, the disc became too tight to turn.  OTOH, the needed clamping of the pivot pins seems reasonable.  Whether they might turn loose once the engine is running for a long period we'll have to see.  Next time I'll need to fettle the strap a bit more to get the disk to turn smoothly.



It appears that the interior hole in the strap is out of round; possibly clamping in the vise when milling it caused some distortion.

Online kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #184 on: November 29, 2019, 03:02:50 PM »
To finish the eccentrics, I needed to drill and tap 4 3-48 grub screw holes around the collars.  Rather than do so individually, I cut off a short piece of 7/8" drill rod (diameter of crankshaft) and loctited both eccentrics to it.  Then holding the free end of the rod in a 7/8" collet and square block, I could quickly spot drill and drill each at 90 degrees separation around the collar.  By drilling into the shaft I avoiding internal burrs and allowed through tapping  while on the  rod.





Continuing on, I made a start on the swing yoke casting.  The surfaces of the "outer" portion are relatively flat and parallel, so clamping there in the Bridgeport vise allowed me to mill reference surfaces where the swing joint will be.  Both sides were milled without moving the work.



Then clamping these surfaces I milled off the sprue.



And at the same time the front and back of the "arm" were milled so as to be parallel to the reference surfaces.



The next two ops required the use of the Mark I precision eyeball.  First, I need to position the piece in the vise so that the arm was as nearly vertical as I could make it.  I used a small drill in the spindle as an alignment aid.  Once I was satisfied there, I used the same drill to determine the center of the arm and hence the centerline of the entire piece.  Given that, I could mill equal amounts from the sides of the arm to get smooth reference surfaces.

The next op also needed the same precision eyeball.  I clamped the arm in the machinist vise using a 123 block on the surface plate to ensure the work was flat.



Now I needed to determine the center of the round pocket that would be milled.  Moving the assembly to the bridgeport, I located the centerline of the arm with an edge finder, and then a drill bit to visually estimate the center of the circle. The DRO told me the distance from the side of the small vise.  Now I could move the CNC mill vise and duplicate the edge finding to locate the center.


Online kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #185 on: November 29, 2019, 03:09:53 PM »
Yesterday I loaded the program to mill the circular hole.  When running, the 1/2" 4-flute carbide endmill couldn't penetrate the thin material in the center, merely pushing the work downward in the vise.   I decided to drill the center on the Bridgeport, only to find that my cobalt drill bits wouldn't cut it.  Seems the thin area cooled too quickly and became very hard.  I put a 5/16 2-flute cabide endmill in and with a good deal of force on the spindle managed to punch through.  The material is only about 1/16" thick but quite a fighter.

Using a spare 1/4" carbide endmill with a chipped end flute, I tried using the side flutes to remove the center material not caring muchly about the endmill itself.  Before quitting for Thanksgiving dinner, I milled away about half of it at very slow speed and lots of red sparks being thrown about.  Hopefully next shop session I can get rid of the rest and that the thicker sections will mill more normally.
« Last Edit: November 29, 2019, 09:37:17 PM by kvom »

Offline crueby

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Re: Greene Automatic Cutoff Steam Engine
« Reply #186 on: November 29, 2019, 03:49:44 PM »
Can castings like that be annealed by heating then cooling slowly?

Online kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #187 on: November 29, 2019, 04:03:04 PM »
I believe for cast iron the required temperatures/times would be a lot higher than I could safely generate without a heat treat oven.

Offline Jasonb

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Re: Greene Automatic Cutoff Steam Engine
« Reply #188 on: November 29, 2019, 04:10:17 PM »
You need about 880 degrees C, if you don't have an oven then an open fire or wood burner will do the trick, just leave to cool slowly in the ashes overnight. very small parts can be given a good long blast with a propane torch.

Looking at the amount of flash around the casting I wonder if the middle was meant to have any metal in there, looks like the mould halves were not weighed down enough and some liquid metal flowed into the gap.

Online kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #189 on: November 29, 2019, 09:36:47 PM »
The eccentric castings didn't have a lot of material in the centers, so I suspect Jason is correct.  But the material there was quite consistent in its thickness.

Offline Craig DeShong

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Re: Greene Automatic Cutoff Steam Engine
« Reply #190 on: December 01, 2019, 03:22:09 PM »
My friend in Apex is just starting on the yokes to his Greene engine.  It will be interesting to compare how you attack the problem as opposed to how he does it.

Great work you're doing.  I''m following along even though I don't comment as much.
Craig

Online kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #191 on: December 01, 2019, 04:03:03 PM »
Is he posting any of his work?

Online kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #192 on: December 01, 2019, 10:41:34 PM »
More ops on the yoke.  I finished cleaning out the center with the 1/4" drill on the BP;  it seemed to be less hard the closer to the edge.  Then mounted on the CNC mill to relocate the center once again.



Then milled the center to a diameter of 1.85" using very light DOC.



Now it was time to thing out the casting.  I used the point of the spotting drill to estimate the center of the casting rib...



...and then took equal amounts off each side.



Next, I used a 1/8" 4-flute carbide bit to split the yoke.  .025" DOC each pass.



Spot and drill the mounting hole.



And then mill the other side of the holes flat.


Offline Dennis

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Re: Greene Automatic Cutoff Steam Engine
« Reply #193 on: December 02, 2019, 03:43:22 PM »
Craig,
Tell you friend in APEX that Dennis said Hi and I haven't forgotten about the part I promised.  still working on problems at the foundry.

Dennis

Offline Dennis

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Re: Greene Automatic Cutoff Steam Engine
« Reply #194 on: December 02, 2019, 03:49:46 PM »
Hello everyone,
the metal in the center of the eccentric rings is flashing from a mold that didn't close all the way.  It is unfortunately common.  Kirk is correct thinking the thin metal cools very quickly and is hard as if quenched.  The thin flashing is so brittle that I remove it with a hammer and punch, it breaks out like glass and is much softer at the edges where it contacts the thicker ring.  The thicker ring slows the cooling of the flash at the edge.

Thanks for posting all of these photos and machining details Kirk.  Hope your healing process is still going well. 

Dennis