Author Topic: Pennsylvania A3 Switcher (Kozo)  (Read 129390 times)

Offline Minh Thanh

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1455 on: December 27, 2021, 01:48:48 AM »
Great !

Offline stevehuckss396

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1456 on: December 27, 2021, 11:03:27 AM »
I don't comment nearly enough but this thread is one of the great ones.great work and great documentation. Thank you for taking the time. I do check in on every update.
Do not be like the cat who wanted a fish but was afraid to get his paws wet.

Offline Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1457 on: December 27, 2021, 05:53:51 PM »
Thanks for looking in on me Per, Minh, and Steve!
I really appreciate the kind comments  :cheers:
Kim

Online propforward

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1458 on: December 27, 2021, 07:24:22 PM »
Magnificent work Kim, coming right along.
Stuart

Forging ahead regardless.

Offline Steamer5

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1459 on: December 28, 2021, 08:44:05 AM »
Hi Kim,
 Moving right along !
Nice work on those 4 brackets, look to be tricky little items, you nailed it!


Cheers Kerrin
Get excited and make something!

Offline cnr6400

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1460 on: December 28, 2021, 01:30:16 PM »
 :ThumbsUp: :ThumbsUp: :ThumbsUp: :popcorn: :popcorn: :popcorn:

Offline Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1461 on: December 28, 2021, 05:25:54 PM »
Thanks, Stuart, Kerrin and CNR,
Appreciate your encouragement!  :cheers:
Kim

Offline Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1462 on: January 03, 2022, 12:05:13 AM »
Chapter 17.12 Return Cranks

This week I worked on the Return Cranks.  These are the little arms that clamp onto the crankpin on the rear wheels and provide an out-of-phase motion that is contrary to the motion of the crosshead bracket.  These two motions are combined through the combination lever to produce the final motion for the steam valves.

The return cranks were made together, end to end, out of a length of 1/4" x 1/2" 1018 bar.  After thinning the bar to 0.200 I drilled and reamed four 1/8 holes, two in each part.  The outside holes are used to hold the part on the jig for many of the machining steps but will later be enlarged for the crank pin.  The inside holes are the ones that will connect to the radius rod via a 1/8 pin.


Using the outer holes, I mounted it on a jig and used a 1/8 end mill to define the edges of the 1/2" diameter round section that is centered around the eventual crankpin connection.


Then I milled the outside ends flat to the correct width.  This will be where the screws go that will clamp the part onto the crankpins.


Next, I moved the part into a second hole in the jig that provided a ~5o angle so I could cut the angled sides of the crank.  This shows just after the first edge has been angled.  Note that the angle only goes to the center of the piece because there are TWO parts here.


Flipping it around and turning the piece over I cut the opposite side angle.  These two angles meet in the middle.


Then I completed the same two operations on the other side.  Here are all four angled sides completed.  You can begin to see the shape of the return cranks.


Moving the piece back to the horizontal position on the jig, I mounted the jig vertically and used a 1/8 end mill to cut a recess on one side.  This covers both parts of course.


And while the part is upright and clocked in, I drilled #49 holes through both ends.  This is not the right size for the #3-48 screws, but it is the right size to hold my filing buttons, and it is small enough that it doesnt mess up the #3-48 holes.  Well widen these holes later.


Next, I used 1/2" filing buttons to round the area around the crankpin holes.


Then I filed the ends round, again using filing buttons. These filing buttons are held with a #1 screw, which is why I used the #49 here earlier.


Now that Ive rounded the ends I can go ahead and drill the end holes to their final size.  They were first drilled through for #3-48 tapping, then I drilled halfway through with a 3-48 clearance hole.  After this, I tapped the other half of the hole.


And then I widened the crankpin holes and reamed them to 7/32 to match the crankpins.


The last major operation here is to cut a 1/32 slit on the end of the crank to allow the 3-48 screw to actually clamp the part onto the pin :)


With all major operations complete its now time to cut the piece in half on the bandsaw and use 9/32 filing buttons to round the ends of the crankpins.


And here are the two completed Return Cranks!


That was a lot more work than it had any right to be, but Im pleased with how they look. And yes, they do in fact, tighten nicely onto the crankpins, I checked!  But before I can really assemble all of these pieces Ive got a bunch of little pins to make. So thats what Ill be doing next.

Thanks for looking in!
Kim

Offline RReid

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1463 on: January 03, 2022, 12:34:18 AM »
Real nice work, Kim. You're a link-makin'-maniac! (I mean that in the best possible way, of course ;):ThumbsUp:
Regards,
Ron

Offline Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1464 on: January 03, 2022, 12:52:23 AM »
Only taken in the best possible way!  ;D
Thanks Ron!
Kim

Offline matthew-s

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1465 on: January 03, 2022, 05:12:46 PM »

Then, with a 1/16 mill, carved out the steam ports.  The inlet ports are just a hair over 1/16 (0.078 which just happens to be 2mm) and the exhaust port is 0.394 wide (10mm wide).  Seems Kozo didnt bother to change this part of his design from metric.  Worked fine for me.  But its interesting nevertheless!



Kim,

I cant figure out the steam port depth. Do you recall how you figured that out?
The books narrative says refer to figure 14-7 for that, but its not shown

The right end view in Figure 14-3 could be read to imply the floor of the steam ports  intersect a plane  created with the peak of the cylinder major diameter ( the 1 7/16 dimension). 

Seems pretty important to not be specified explicitly though!! Perhaps Im missing something obvious?!?

What worked for you?

Thanks in advance.

Offline Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1466 on: January 03, 2022, 11:20:06 PM »
I can’t figure out the steam port depth. Do you recall how you figured that out?
The book’s narrative says refer to figure 14-7 for that, but it’s not shown

The right end view in Figure 14-3 could be read to imply the floor of the steam ports  intersect a plane  created with the peak of the cylinder major diameter ( the 1 7/16” dimension). 

Seems pretty important to not be specified explicitly though!! Perhaps I’m missing something obvious?!?

What worked for you?

Thanks in advance.

Well, you're right, I couldn't find it specified anywhere either.  So I did just what you describe, calculating it that way.  I came up with 5/32" deep.  It's clearly marked on MY drawings from when I cut the steam ports :)

However, I don't really think the depth is all that critical.  The main steam passageways are much smaller - just those drilled holes.  The important part of the milled ports is their width.  I don't even think the height is all that important, as long as it doesn't constrict the incoming steam or outgoing exhaust.  But the width is what's important because that has to line up with the edges of the D-valve to get the correct timing of the steam in and out of the cylinder.

So if you made the ports a little deeper, or a little shallower, I don't think it would matter at all.  (Though I'm willing to change my opinion based on what other people with more knowledge in this area have to say! Always willing to learn!)

Good luck, Matthew!
Kim

Offline crueby

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1467 on: January 03, 2022, 11:41:37 PM »
I agree Kim - the depth of the ports is not critical, just needs to be sure not to break through into the cylinder or any other passage.


 :popcorn: :popcorn: :popcorn:

Offline Minh Thanh

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1468 on: January 05, 2022, 03:14:29 AM »
I love steam train  , I will build a steam train someday
 Thanks for share !

Offline Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1469 on: January 05, 2022, 05:30:47 AM »
Thanks Minh!
I'll look forward to seeing you post your steam locomotive build!
Kim