Author Topic: Greene Automatic Cutoff Steam Engine  (Read 26125 times)

Offline Dennis

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Re: Greene Automatic Cutoff Steam Engine
« Reply #420 on: August 30, 2020, 09:50:17 PM »
Those are good ideas Kirk, personally, I do not like set screws and much prefer the tapered pins for those connections.

Offline kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #421 on: August 31, 2020, 02:03:28 AM »
I removed the swing link assembly and decided to fix the actuator rod with Loctite 638 with the two grub screws in addition.  I also shortened the threaded rod that connects the lever to the ball joint.



Assembling these parts is a bit tricky.  First, one needs to disassemble the ball joint to thread the rod into the ball.  Trying to do so with the joint intact just causes the ball to rotate freely rather than screwing in.  Then the lever must be screwed on.  Doing it after the ball joint is reassembled wont work because the swing link gets in the way.  Only now can the joint be reassembled inside the link.

While these parts were out I managed to do so some cleaning up of some bearings so as to provide lubrication paths.



The two small bearing blocks had 1/16" holes drilled when made, but now I needed to loctite the bearings and then extend the holes into the bores.

For the main standard, I drilled a 1/8" hole in the bottom center and installed a small length of 1/8" drill rod.  A matching 1/8" shallow how was drilled in the bottom of the bearing, so that when assembled the bearing won't shift.  I then drilled a .104" hole through the bearing cap, and then a 1/16" matching hole through the top of the bearing.  At some point an oiler will be placed atop the cap, but for now a small amount of oil can make its way down to the shaft.

The other standard and bearing will get the same treatment at a later date.

Note for future builders.  The small bearing block that mounts on the other standard is nearly impossible to remove with the outer standard in place.  I suggest using a socket screw for the bottom hole, as that can be accessed.  A hex head screw would need a 90 degree nut driver and much patience.

Offline gary.a.ayres

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Re: Greene Automatic Cutoff Steam Engine
« Reply #422 on: September 02, 2020, 08:27:37 AM »
Disassembled parts needed to separate the cylinder block preparatory to being able to assure air tightness in the exhaust valves.




It's looking beautiful...

Offline kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #423 on: September 02, 2020, 02:30:45 PM »
I noticed some "lost motion" in the exhaust valves, and some of it appears to be in the eccentric being too loose in its strap. It's possible that movement inside the strap is like backlash that can be ignored as long as the rotation is not reversed.   I finally got the valves to actually move in sync with the flywheel and applies air.  Nothing moving, but at least the sound is something other than the steady hiss of leaking air.  I'm going to remove the eccentrics and try to tighten up a bit.  While they're out, I'll drill for the oilers.

Offline kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #424 on: September 08, 2020, 07:32:39 PM »
I took everything apart to address some issues that I put off.  The first was to make the fit of the exhaust eccentric to its strap a bit better.  One issue is that the two halves of the strap need to clamp the pivots of the swing arm, so there's a balance between the fit of the two halves and the diameter of the pivots.  I ended taking 25 thou off of the straps and 9 thou off the pivot diameter.  Obviously I needed to be careful as taking too much off the strap would cause the eccentric to jam; it's a bit of a balance.  There's still some play between the strap and eccentric, but it's much smaller than before.  The upper half of the strap was also drilled for an oil passage.

While apart, I also did the same ops on the inboard standard and bearing as I did before on the outboard, so both now have paths for lubrication.

In order to be able to visually see that open/shut status of the exhaust valves, I came up with this idea.  Both the fixed and stationary halves were marked with dimples on the back ends to ensure they stay paired.  Then they were clamped together in the open position and a line scribed in the fixed valve marking the end of the moving one.  Then the moving valve was moved  slightly to a closed position and another line scribed.



The idea is that when timing the exhausts, I'll have the rear covers removed and can see when the moving valve is at the open and closed positions.

Offline kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #425 on: September 14, 2020, 09:25:58 PM »
My wife suggested that the 20+year old toilet set in our bathroom had outlived its time (who knew you could wear out a toilet seat?).  But being the agreeable sort I went to Lowes and got a new one.  While installing it I pulled a muscle in my back, so no shop time again today.  What does that have to do with the Greene engine you ask?

Since the exhaust valve motion is still being contrary, with the angle of the clevis being close to 90 degrees to the connecting rod, I decided to model the assembly in SW.  Here the angle is more forgiving.  After some measurements I found that I had used the wrong drawing/SW part for the rod ends on the connecting rod.   :hammerbash: :killcomputer:

So the intra-hole distance as built is .72" rather than .63".

Easy parts to make correctly, so I'm hoping tomorrow the back isn't as sore and I can make progress again.

Offline kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #426 on: September 24, 2020, 04:26:05 PM »
My scheme for marking the open and closed positions on the fixed grid ran into an issue, as I had forgot that the sliding grids move in opposite directions from open to closed, so I needed a different closed mark on one grid.

In testing with the valve links at .625", I saw the the sliding grid moved much further than the distance between marks.  So I needed to investigate how to adjust the grid travel.  To do so, I made a Solidworks sketch:



I determined that the actuating rod moves through the 13+ degree angle based on the eccentric's .14" travel and the lever's .59" length.  The clevis is represented by the .59" line and the link by the .7" line.  The ends of both lines are constrained to remain on the dotted line.

The angle of the clevis has an effect as well, but I chose 30 degrees below horizontal as a reasonable value.  By varying the lever's length and measuring the distance between the two points on the dotted line, I can determine the grid travel.  With a link at .625, which is what the engine had, the travel would be .155", which verifies what I saw.  I had to increase the link length to .7" to get the travel to .1".

Based on the as-drawn dimensions of the grid, the required travel needs to be in the range of .08-.1".

When I first machined the grids early in the project, I reasoned that spacing the openings further apart would make timing easier, and did so.  But when I remade the fixed grids to be full length in the block, I reverted to the original spacing.

So now I need to decide whether to continue with the current grids and try to adjust the travel to what's needed, or to remake the fixed grid and have more wiggle room in timing.  I'm leaning towards the latter even though that means another major disassembly of the engine.

I'll also mention that I remade the valve crossheads in steel replacing the brass ones.  They seem to slide much more easily as the brass caused a lot of friction for some reason.

Offline Craig DeShong

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Re: Greene Automatic Cutoff Steam Engine
« Reply #427 on: September 28, 2020, 09:57:41 PM »
Following along Kirk;  :popcorn: :popcorn:

Lots of parts to get all working together. 
Craig

Offline Roger B

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Re: Greene Automatic Cutoff Steam Engine
« Reply #428 on: September 30, 2020, 11:51:00 AM »
I'm still following in the background  :ThumbsUp:  :ThumbsUp:  :wine1: That's a tricky linkage to set up so all runs well  ::)
Best regards

Roger

Offline kvom

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Re: Greene Automatic Cutoff Steam Engine
« Reply #429 on: September 30, 2020, 01:55:38 PM »
Thanks for looking in people.  I've had a lot of distractions lately, but I hope to be able to try again with a corrected link soon.

** edit **

I made a link that was .7" long, but still had grid movement over .2".  The problem is that I can't get the start angle of the clevis small enough before the crosshead hits the end of the bracket.  I considered shortening the crossheads, but I think making shorter links until I get the necessary movement will be more prudent.

It's pretty clear that the clevis angle has the greatest effect, something that appears obvious after some thought.

My plan now is to continue with the grids as they are to get it to run, but to remake with wider slot spacing later on.
« Last Edit: September 30, 2020, 09:24:08 PM by kvom »