Author Topic: Pennsylvania A3 Switcher (Kozo)  (Read 155910 times)

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1890 on: September 22, 2022, 10:51:29 PM »
Apparently, I wasn’t completely done with the lever yesterday.  It still needed a pin to connect to the eccentric rod.  So I quickly turned up the pin and Loctited it into the lever:



Chapter 21.10 – Spring Pawls
Now to the little spring pawls that make the ratchet mechanism work.

I made these from some of that metal strapping tape that comes wrapped around big heavy boxes.  I can't remember how long I've had it but I remember when it came in I thought "Hey, sprint steel!  This could come in useful someday!"   So I've saved it for years and looky here - now I get to use it!

Here I’m drilling two little #52 holes for 0-80 screws.


After cutting them to size and sanding to clean up the edges, here are the two spring pawls:


Now all the parts of the lubricator pump itself are complete.  Still have the eccentric rod and strap to go, but that’ll come later.  Now I’m going to assemble the pump.  And here are all the pieces that go into the lubricator pump:


Before assembling I tested the pump/ram mechanism to make sure it would pump.  Turns out it doesn’t pump water at all because there’s no o-ring seal around the ram.  But when I tried oil, it worked fine.  It doesn’t move a ton of oil, but it would send out tiny spurts, but that’s all that’s needed. Kozo refers to this in his book saying the viscosity of the oil allows you to get away without having an o-ring here.  Apparently, he’s right. Who knew?  :Lol:

While assembling it, I discovered that one of the spring pawls just doesn’t reach the ratchet wheel when it’s the specified length of 1/2".  So I quickly made another one that was 1/8” longer.  That worked. I still may have to fiddle with the lengths a little bit, but at least it demonstrates the working of the pump mechanism.

Here it is all assembled – from the outside:


And from the inside  (kind-of):


I took a video to show the ratchet working.  It’s pretty cool!

Thanks for looking in!
Kim

Offline crueby

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1891 on: September 22, 2022, 10:54:47 PM »
Sweet!

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1892 on: September 22, 2022, 11:14:22 PM »
Thanks, Chris!

And I wanted to mention to everyone that previously I stated that I was not using stainless steel balls for my pumps.  Which is correct. But what was incorrect is that I said I was using nitrile balls.  I'm not.  I'm actually using Si Nitride balls.

I went back and changed that on my previous posts, but I wanted to make a note of it here since I doubt that many of us go back and re-read old posts!  :Lol:

Regardless, I'm sorry if my mistake caused you any confusion.  Hopefully, I'll be sure to state the correct name of the material going forward!

Thanks,
Kim

Offline cnr6400

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1893 on: September 23, 2022, 12:35:01 AM »
 :ThumbsUp: :ThumbsUp: :ThumbsUp: :popcorn: :popcorn: :popcorn:

That works great Kim! well done. Like a Swiss watch! (if a Swiss watch had an oil pump)  :Lol:

Offline Don1966

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1894 on: September 23, 2022, 01:13:59 AM »
Some fine work going on here.  :Love:



 :cheers:
Don

Offline Dave Otto

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1895 on: September 23, 2022, 01:20:17 AM »
Looks great Kim!

Dave

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1896 on: September 23, 2022, 05:23:49 AM »
Thank you CNR, Don, and Dave!  :cheers:

Kim

Offline Michael S.

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1897 on: September 23, 2022, 10:04:24 AM »
Hello Kim, I like the construction of the ratchet drive. I'm considering rebuilding my oil pump on the Stuart 5A. I use a needle bearing freewheel there. As soon as oil gets close to it, the drive fails.
Very good work Kim 👍

Michael

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1898 on: September 23, 2022, 05:30:26 PM »
Thank you Michael!  :cheers:
Best of luck on the rebuild of the oil pump for your Stuart engine!

Kim

Offline Admiral_dk

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1899 on: September 23, 2022, 07:50:46 PM »
Good to see another fine little sub-assembly leave the productionline and passing the test  :ThumbsUp:

 :cheers:   :popcorn:   :cheers:

Per

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1900 on: September 24, 2022, 12:04:31 AM »
Thanks Per!  :cheers:

Unfortunately, the QC department kicked it back for rework, as you'll see in today's update.

But NOW I think it's ready for use! :)

Kim

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1901 on: September 24, 2022, 12:16:03 AM »
Well, you know that sinking feeling you get when you notice something doesn’t look quite right?  Well, I got that feeling yesterday after I posted my update.  I was watching the video of the ratchet wheel turning the pump crank and it suddenly dawned on me that the pump plunger was supposed to be under the crank pin during the downward stroke of the pump.  The downward stroke is the one that will be under the most load, since it’s squishing the oil, under pressure, into the system.

And what you’ll notice in the video is that the crank pin is FAR from the plunger on the downward stroke.   :facepalm:  What's going on?

So, I spent some time investigating this today and found that I’d drilled the hole for the pump body on the wrong side of the pump housing.  It is supposed to be offset 1/16” to one side.  I just happened to get the wrong side.  How’d I do that you might ask?  I certainly asked that question!

Turns out that the diagram for the pump shows the hole from the TOP, not the BOTTOM, which is what I’d assumed.  So the offset happened on the incorrect side.

This is at the start of play today – the crank is moving up (sucking oil into the chamber, not under pressure.  But the crank pin is close to the plunger.  This is backward.


What to do?  After cogitating on this overnight, the plan I came up with was to silver solder a plug in the hole and re-drill.  I thought it sounded like a great plan, so I got to work.

Here’s me turning the plug from a piece of CRS. 


Here’s the housing, the plug, and a couple of pieces of sheet steel that I grabbed out of the scrap bin to use to cover the glass.  My hope was that by covering the glass with the sheet I could avoid breaking the glass during the silver soldering. Solid plan, right?


Here’s the part setup on the operating table, ready for the repair work to begin.


I used black flux, which I always use on steel and larger parts since it takes longer to get them up to temp.  You can see just a bit of the solder ring sticking out of the black flux along the top of the plug.  I’d made a few dimples in the plug to help keep it centered and to provide enough friction that it wouldn’t fall out during soldering.


The soldering operation went great!  But the glass came out cracked in the end.  Ah well, I’ve got another 97 microscope slides that I can use to cut a new piece of glass for it.

Here I’m set up in the mill, just getting ready to shave off the bottom of the plug.  I didn’t pickle it very well… I was too impatient.


But it’s clear that the solder penetrated the repair joint quite well!  I’m pleased!


And then I had to mill off the top of the plug on the inside.  No before picture here, just the after.


Now, to drill the hole for the pump body in the CORRECT place this time.  You can see the faint outline of the plug I soldered in place – it’s only off from the correct hole by 1/8”.  It was supposed to be offset 1/16” from the center line.  I went the wrong way the first time. So going 1/16” the correct way this time, makes 1/8” total.  That looks promising, doesn’t it?


And here, to compare with the plans.  I wrote “TOP” on this picture now – I guess for the NEXT time I make one of these :).  But you can see how if you interpreted this view to be a BOTTOM view, the hole would be on the opposite side of center.  Ah well…  Live and learn (he says optimistically).


And here’s the after picture.  I decided not to put a piece of glass in till after I’ve painted the housing.  I was worrying about how well the glass would survive the powder coating oven anyway.  Nothing else on this unit will be painted. Well, maybe the pawl bracket and/or lever.


And here are the before and after pictures right next to each other – hopefully, this makes it more clear on how offsetting the plunger on one side or the other affected things.  The picture on the left is the BEFORE shot.  The crank pin is on the way UP and is more closely centered over the plunger (this is backward).  The picture on the right is the AFTER shot.  The crank pin is now moving downward and is closer to the plunger, which is CORRECT since this is the stroke that requires more power – pushing the oil into the system.


Note that the plunger cam follower thing (scotch yoke) is also reversed in the before/after pictures too.  That was another clue that things were wrong.

But I’ve got it turned around now. And all it cost me was a day’s effort in the shop!

That’s a bargain, right?!
Kim

Offline Dave Otto

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1902 on: September 24, 2022, 12:33:41 AM »
Nice save Kim!

Dave

Offline cnr6400

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1903 on: September 24, 2022, 02:40:08 AM »
 :ThumbsUp: :ThumbsUp: :ThumbsUp: :popcorn: :popcorn: :popcorn:

offset holes to the wrong side have never ever happened in my workshop. (more than 920 times, anyway)  :Lol:

Nice recovery. Save the broken glass in case you ever want to make a diorama with the locomotive in the roundhouse. You can pose an apprentice figure and an irate foreman next to a little pile of the shards!  :Lol:

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1904 on: September 24, 2022, 05:31:49 AM »
Thanks Dave and CNR!

:ThumbsUp: :ThumbsUp: :ThumbsUp: :popcorn: :popcorn: :popcorn:

offset holes to the wrong side have never ever happened in my workshop. (more than 920 times, anyway)  :Lol:

Nice recovery. Save the broken glass in case you ever want to make a diorama with the locomotive in the roundhouse. You can pose an apprentice figure and an irate foreman next to a little pile of the shards!  :Lol:

That would be great!  :ThumbsUp: Unfortunately, the glass shattered as I was trying to take it out.  It chipped out in a little pile of sharp dust so I doubt it would be useful for a diorama.  But I've got a bunch more pieces of glass I could break in more strategic ways for the diorama!  I'll probably be doing some strategic glass breaking soon anyway, so I'll keep track of those pieces for future use.

Kim