Author Topic: Greene Automatic Cutoff Steam Engine  (Read 44588 times)

Offline kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #480 on: July 22, 2021, 08:30:23 PM »
Remake of the exhaust valve brackets proceeded over several days.  The first ones were made of cast iron from 1.875" round bar, but I discovered I didn't have enough left over.  So I used some 2" hex brass rod cut into 2.5" pieces.  A 5" diameter hole is drilled into the center on the lathe to a depth of 1.7" with a 1/2" carbide endmill held in the tailstock.  I checked depth with a depth micrometer as drilling proceeded.  The OD was turned to 2" diameter for a length of 1.85".



Profile rouging and spot drilling on the CNC mill was next, and the holes for the bearing cap screws were drilled.



The bearing cap screw holes are tapped 2-56.



The first powder coat was done next, after which the 4 mounting holes were drilled.




The remainder of the stock was milled away, and the brackets were checked for fit on the engine block.



After finish milling the bracket shafts, the were powder coated again, after which the holes for the valve stem and oil were drilled.



I then made new bearings as the shaft arms are slightly wider than before.  A test assembly shows the connecting actuator rod mates very wekk.




Offline Kim

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Re: Greene Automatic Cutoff Steam Engine
« Reply #481 on: July 22, 2021, 10:23:02 PM »
Very pretty work, kvom!  :ThumbsUp:

What was the reasoning for the first powder coating before the milling step?  You still had to coat it again, so you would still have to mask everything off, right?  Just curious.

Thanks kvom,
Kim

Offline kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #482 on: July 23, 2021, 02:24:35 AM »
First pass little masking was needed; just plugs/screws in the holes.  Less masking was needed as well the second time as I had a plug for the bore and had only to touch up a few places.  I wanted no powder on the face that mates with the cylinder.  Seemed easier overall.

Prior to working on the exhaust timing I plan to replace the activator rod as it attained a lot of burrs and abuse with previous trials.

No more pieces to make, so I can only hope it turns into a runner.  The rubber drive belt isn't tight enough to turn the governor reliably, so I'll need to shorten it by a tiny bit.

Offline kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #483 on: July 24, 2021, 10:36:51 PM »
After test fitting the valve brackets with the valves attached, I discovered that I had confused the top and bottom of the bracket, both here and with the previous versions.  Since the mounting holes are not symmetric vertically, the holes didn't match up (good clue).  So that meant I needed to turn both over and switch ends of the cylinder block.  It also meant I had drilled the oil hole through the bottom, which isn't a problem, but I needed to drill the holes again.

With that sorted, I spent several hours putting it all together and attempting to time both the inlet and outlet valves.  With it all buttoned up, here is the assembled engine:



Of course I had to apply some air while praying for a miracle, but alas no better than previous efforts.  I'm seeing neither kicks in the desired direction nor resistance.  One issue may well be the exhaust valves.  When I paired the fixed and sliding grates I measured how far the sliding grate end was from that of he fixed grate when the valve is open.  Then in setting each to it's open position, I used a depth mic set to that value.  I had previously also measured the displacement at the closed position, and both exhausts move more than the minimum.  The slide can move up to 1/8" further before it would begin to open to the next slot.  The amount the slide moves is a function of the clevis angle to horizontal.  The flatter it is the smaller the movement; to flatten the angle, the length of the valve stem must be shortened by screwing it further into its crosshead.

We have a family outing tomorrow, and then I'm in Las Vegas through Friday, so next weekend I'll have another go.

Offline crueby

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Re: Greene Automatic Cutoff Steam Engine
« Reply #484 on: July 24, 2021, 10:43:48 PM »
Looks great - I am sure you will solve the timing issues too.  One thing I like to do when having issues like that is to take or at least loosen the cylinder end cap. It at least makes it very easy to tell if the inlet valve at that end is opening/closing effectively, also shows if there is leakage past the piston. Just a suggestion.
 :popcorn: :popcorn: :popcorn:

Offline kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #485 on: August 25, 2021, 09:33:20 PM »
I have been occupied with lots of outside issues and thus only a few hours off and on playing with various timing tries.  I recently tried setting the output valves so that the leading edge of the slide valve groove was just at the outside edge of the fixed valve groove.  I can do this since I measured the offsets of the valve ends when the grooves are aligned.  Since the end of the fixed valve is flush with the side of the block, I set set a depth micrometer, hold it against the block, and advance the sliding valve until it touches, then lock the set screw.  This allowed some progress so that for several shop sessions I was able to have the piston powered in one direction, but I haven't been able to get the reverse portion of the cycle no matter how I adjust its inlet valve.

Today I had a revelation of a fix that can be tried the next time I have shop time.  I noticed that the valve stem crosshead blocks were touching all through the cycle, hence "pushing" each other.  To have a gap between them and thus have the valves work independently, I need to change the position of the crosshead when the valve is completely closed.  This will be done by adjusting the angle of the control clevis when the dash pot is at its bottom and the valve is closed.

For a simpler explanation, here's how each valve works.  It is closed with the dash pot piston at the bottom of its pot.  When the slide moves the catch, it rotates the actuator rod while raising the dash piston.  The actuator rod in turn rotates a clevis attached to the valve stem crosshead.  Once the slide is at its furthest and reverses direction, the dash piston pulls actuator rod so that the catch follows the trip until the dash piston bottoms. 

To have a gap between the crossheads, each needs to be closer to its side of the block meaning the valve stem is further into the steam chest, and the valve position on its stem adjusted is the opposite direction.

Offline kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #486 on: August 28, 2021, 09:38:59 PM »
The ideas mentioned in the previous post have bourn fruit, as the engine now runs on air at high pressure.  Setting the clevises on the actuator rod as well as the position of the valves on their stems is quite delicate, and it took 90 minutes and several non-starts/adjustments to achieve this stage.  I didn't have a pressure gauge on the line, but would guess it was over 40 psi in this video.  Some gasketing will hopefully improve things.  I also replaced the grub screws fixing the clevises with socket screws, as the sockets in the former were being deformed by the allen wrench when tightened.  I think replacement with button head screws will improve appearance. 


To finish I'll need a better air valve, a tighter drive belt for the governor, and to finish the steam chest covers.


Offline Admiral_dk

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Re: Greene Automatic Cutoff Steam Engine
« Reply #487 on: August 29, 2021, 10:33:42 AM »
Congratulations on achieving this major milestone with a challenging project   :ThumbsUp:

Offline cnr6400

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Re: Greene Automatic Cutoff Steam Engine
« Reply #488 on: August 29, 2021, 01:54:40 PM »
 :ThumbsUp: :ThumbsUp: :ThumbsUp: :popcorn: :popcorn: :popcorn:

like a Swiss watch! well done!

Offline RReid

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Re: Greene Automatic Cutoff Steam Engine
« Reply #489 on: August 29, 2021, 02:52:41 PM »
Quite a good bit of detective work and problem solving. Congratulations! You'll soon having it running just as fine as it looks! :ThumbsUp:
Regards,
Ron

Offline Kim

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Re: Greene Automatic Cutoff Steam Engine
« Reply #490 on: August 29, 2021, 04:54:40 PM »
Very impressive, Kvom!  Well done!  That's a very complex mechanism to get working!   :ThumbsUp: :popcorn: :popcorn:

Kim

Offline Dennis

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Re: Greene Automatic Cutoff Steam Engine
« Reply #491 on: September 01, 2021, 04:55:55 PM »
Very good Kirk, glad to hear you finally got both sides of the cylinder under power. 

Yes, the Green engine is sensitive to adjustments and scaling it down to model size makes it even more sensitive.  I'm sure your engine will smooth out and run on lower air pressure with some more break in run time and a little more fiddling with the valves and eccentrics.

Dennis

Offline crueby

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Re: Greene Automatic Cutoff Steam Engine
« Reply #492 on: September 01, 2021, 05:35:56 PM »
Excellent!!!   :popcorn: :popcorn: :popcorn:

Offline fireguy976

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Re: Greene Automatic Cutoff Steam Engine
« Reply #493 on: October 11, 2021, 03:23:49 PM »
Hi all,

been a long time since being here.

Getting ready to retire and interested in building some kits.

Only reason I mention in this post is, I tried to track down "Historic Model Reproductions",, then Green River tools,,,

and both seem to be out of business.

Are there any other companies making This kit?

Thanks in advance
KJ
« Last Edit: October 11, 2021, 03:27:35 PM by fireguy976 »

Offline jeff l

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Re: Greene Automatic Cutoff Steam Engine
« Reply #494 on: October 17, 2021, 08:31:23 PM »
Historic Models and Reproductions is in business but I have some major health issues that have slowed me down a bit  and the foundry that I currently use is slow to fill my current orders .I do have a few engine casting sets in stock though .Jeff
my email jeffreylehn@comcast.net