Author Topic: Pennsylvania A3 Switcher (Kozo)  (Read 84707 times)

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1125 on: July 22, 2021, 12:28:55 AM »
Thanks Chris,

Interesting...  But this would only hold insulation over the top of the steam chest - not around the rest of the steam chest or over the cylinder. But maybe the steam chest cover is the thinnest part, so that's why you'd insulate it?

Hmm.... And here I thought it was only for looks!

Kim

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1126 on: July 22, 2021, 10:16:17 PM »
To complete the steam chest cover casings I need to round over all the top edges.  I considered just filing them round but I’m just not that good with a file.  And these parts will be nice and shiny, up-front and center to catch everyone's eye, and I want them to look really good.  So I chose to use a 3/32” round-over bit to round off the edges believing that would produce a much nicer, more uniform look.

I picked this one up on Amazon for not too much.  It’s a wood router bit but I couldn’t find any 3/32” round-over bits specifically for metal that weren’t stupid-expensive.  So I went with this one and it performed admirably in this situation.

First I rounded over all the short corners, like so:


Then I rounded over all the long edges.  It appears easy, but there was a lot of setup time for each unique edge.  You have to get the depth and side cut set just right so you don’t get a stairstep on the side of the round-over.


But eventually, I got it all completed, then buffed it up on a 3M abrasive wheel:


And here’s the cylinders up to this point.  I’ll eventually make little brass nuts to fit on top and hold the casings in place.  But for now, they’ll just sit there looking pretty! :)


Thanks for looking in!
Kim

Offline Johnmcc69

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1127 on: July 22, 2021, 11:09:51 PM »
 :ThumbsUp:
 Real nice work Kim!
 Quietly watching & enjoying the journey!

  :popcorn:
 John

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1128 on: July 23, 2021, 02:24:40 AM »
Thanks John,
And what a journey it is, eh? :)

Kim

Offline crueby

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1129 on: July 23, 2021, 02:36:20 AM »
Never tried a woid router bit for brass, nice idea for light cuts.   :ThumbsUp: :popcorn:

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1130 on: July 24, 2021, 11:56:13 PM »
Never tried a wood router bit for brass, nice idea for light cuts.   :ThumbsUp: :popcorn:
Huh, I'm sure I've seen other people on this forum use wood router bits like this, I could have sworn that one of them was you!  guess I was wrong there, eh? :)

Kim

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1131 on: July 24, 2021, 11:59:26 PM »
Chapter 14.5 – Rear Cylinder Heads


Today I started the Rear Cylinder Heads.  These will hold the O-ring retainer for the main cylinder rod and provide one of the mountings the crosshead guides.

I made them from 1.5” round 360 brass stock.  I mounted the bar in the 4 jaw chuck with a brass scrap wrapped around it to keep from marring the bar, then proceeded to turn the general shape for the Rear Cylinder Head.  Careful work, but pretty straightforward.


Then I drilled a #12 hole all the way through the part (just a hair over 3/16”), then enlarged 7/16” of it to M size and followed that with a small boring bar to bring the O-ring holder to the correct size (0.320”).   


With all the concentric elements completed, I cut the part off leaving a 1/16” boss on the backside to mate with the cylinder.  Here are the two rear cylinder heads up to this point.


I’ve still got to drill holes to mount the head to the cylinder, the crosshead guides to the head, and to retain the O-ring.  So still a lot to do on these parts.

Kim

Offline crueby

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1132 on: July 25, 2021, 12:01:41 AM »
Never tried a wood router bit for brass, nice idea for light cuts.   :ThumbsUp: :popcorn:
Huh, I'm sure I've seen other people on this forum use wood router bits like this, I could have sworn that one of them was you!  guess I was wrong there, eh? :)

Kim
Maybe I did at one point - dont recall!  I know I've used quarter-round end mills.   :thinking:     Too many projects, not enough brain cells surviving the Elfensteiner beer with the elves...!

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1133 on: July 25, 2021, 12:21:34 AM »
Never tried a wood router bit for brass, nice idea for light cuts.   :ThumbsUp: :popcorn:
Huh, I'm sure I've seen other people on this forum use wood router bits like this, I could have sworn that one of them was you!  guess I was wrong there, eh? :)

Kim
Maybe I did at one point - dont recall!  I know I've used quarter-round end mills.   :thinking:     Too many projects, not enough brain cells surviving the Elfensteiner beer with the elves...!
Gotta watch that Elfensteiner!  It can really sneak up on you after 50-60 thimble-steins!  :cheers:

Kim

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1134 on: July 25, 2021, 11:10:39 PM »
I made a little progress on the rear cylinder heads today.

I started by creating a spreadsheet for the table of offsets needed to create the PDC for the cylinder/cylinder heads.  It’s a fairly simple bit of trig.  The only wrinkle is that if I used the same surfaces for reference on both ends of the cylinder, I’d have to recalibrate my DRO.  I didn’t want to do that, so for one end of the cylinder I used the steam port as the X-reference, for the other end I used the flat on the opposite side (if you look at the picture, you’ll see what I mean).  For the Y-reference, I used the steam port face in both cases (so the Y values stay the same between the two cases).


I mounted the cylinder head to the cylinder using a few small pieces of double side sticky tape.  Using the right side of the above table, I drilled the six holes to #37 (tapping holes for 3-48).


Then I went around again and drilled ONLY through the cylinder head with 3-48 clearance hole.


And finally, removed the cylinder head and tapped the holes 3-48.


Here’s where I’m at now showing both cylinder heads mounted.


That’s enough for today - the shop is too hot and I’m heading in!

Thanks for following along,
Kim

Online Dave Otto

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1135 on: July 26, 2021, 12:31:10 AM »
Those turned out great Kim!
If it were me I would sweep the bore with a dial indicator and use the center of the bore for my X/Y datum. Maybe there is a reason that I'm not seeing to use a different point?
I would still use one of the flat surfaces to align the casting but sweep each end to ensure that the covers are concentric to the bore.

Anyway, it looks like what you did worked just fine, can't argue with success. :ThumbsUp:

Dave

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1136 on: July 26, 2021, 05:16:02 AM »
Thanks Dave!  :cheers:

I considered that, but chose to do it this way because the covers will be concentric because there's a 1/16" lip on the backside that fits snugly into the cylinder bore.  And that lip was turned at the same time as the center & packing holes made, so I'm pretty sure they are as concentric as possible.

Also, I hadn't drilled any holes in the cylinder yet either.  The cylinders and headcovers are drilled at the same time this way.

The plus side of doing it this way is that I don't have to zero in the cylinder bore for each side of both cylinders.

The only downside I could think of in using this way is that the bolt hole circle could be a little off-center, and I doubt that would be noticeable.  Regardless, the important features of the headcover should be centered over the cylinder bore, and that is what's most important.

Don't know if that helped explain my thinking.  Please feel free to let me know if I'm wrong here.  I don't have as much experience as many of you.  I'm just doing what seems best to me.

Thanks,
Kim

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1137 on: July 30, 2021, 11:32:29 PM »
Finishing up the Rear Cylinder Heads:

With the heads firmly attached to the cylinder, I can now carefully cut a flat, 1/4" long on the exact top and bottom of the head.  Here’s is the first side:


And here’s the second:


Then I carefully dial in the center of that flat to drill and tap a 3-48 hole for mounting the crosshead guides on both sides.  These are blind holes and don’t go all the way through.


Then, on the third side, I drill and tap a 3-48 through-hole to use for a set screw for the cylinder o-ring retainer.


And that completes the work on the rear cylinder heads.
Kim

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1138 on: July 30, 2021, 11:38:45 PM »
Chapter 14.6 – Front Cylinder Heads

On to the front cylinder heads.  These are much simpler.  The process is very similar but without the o-ring retainer.

The front cylinder heads are also made from the same 1 1/2" 360 stock, turned down to 1 7/16” with a 15/16” boss on the outside.


Also on the outside, we’ll add a 3-48 blind hole. This will be used to hold the Cylinder Head Cover in place.


After cutting a 7/8” x 1/16” boss that will center the head on the cylinder bore, I cut the part off, flipped it around in a 15/16” collet, and cleaned up the nubbin left by the cutoff tool.


I then proceeded to drill the bolt hole circle for the front end of the cylinders using the same process as before.  No pictures of this operation since it was identical to the rear cylinder heads.

And here are the completed front heads:


And finally, the latest, most up-to-date beauty shot of the cylinders:


I only have a few more parts to go to complete the cylinders:
  • The o-ring retainer for the cylinder
  • The o-ring retainer for the steam chest
  • The front and back Cylinder Head Covers

Thanks for following along,
Kim

Offline RReid

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1139 on: July 30, 2021, 11:47:17 PM »
Nice work, Kim! The cylinder/steam chest assemblies are such a key part of a locomotive build, both visually and operationally. Yours are looking fantastic, and I'm quite sure they'll function as well as they look! :cheers:
Regards,
Ron