Author Topic: Pennsylvania A3 Switcher (Kozo)  (Read 104785 times)

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1335 on: October 16, 2021, 05:34:54 AM »
Thanks CNR & Chris!
Got a nice fresh bottle of white popcorn (no kernel shells to get stuck between the teeth)
 :popcorn:

No hulls! That's the best! :)  With butter? (I hope?  ;D)
Kim

Offline crueby

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1336 on: October 16, 2021, 01:12:45 PM »
Thanks CNR & Chris!
Got a nice fresh bottle of white popcorn (no kernel shells to get stuck between the teeth)
 :popcorn:

No hulls! That's the best! :)  With butter? (I hope?  ;D )
Kim
Popped in microwave in a silicone popper dish, either dry then with butter added, or popped in a little peanut oil which adds flavor. Tasty!

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1337 on: October 17, 2021, 12:18:28 AM »
Back to the yokes.

First thing I did was to mill the top down to where it should be.  I used the already drilled holes as reference.  These holes were all located with the DRO so I trust their relationship to each other.  If you recall, Iíd left 0.030Ē at the top of the guide plates for this milling operation. I also milled the outside edge even where that added part stuck out and milled off the heads of the soldering screws. Here Iím checking the height of the top compared to one of the already drilled holes.


Next, I notched the brackets that hold the crosshead guides.  I cut the top inside bracket referenced to one of the existing holes (as above) then used an inside mic to set the distance between the two brackets at 1.040Ē.


Hereís my reading.  Came out pretty close!  I have to confess, I donít usually show the mic readings like this because Iím not usually that close and it's embarrassing to show when youíre off by a thou or two.  But I wanted to show this one! :)


And finally, I took off the screw heads on the backside and then milled the notch out of the top of the plate, according to the plan.


And here are the two guide yokes up to this point.


I still have the final shaping to do.  The shaping work is less critical to the operation though. I still want it to look good, however, so will still be doing things in my slow, methodical way.

Thanks for stopping by!
Kim

Offline joe d

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1338 on: October 17, 2021, 02:50:21 AM »
Looking good, Kim!  Still following along.  Maybe I should invest in some popcorn....

Joe

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1339 on: October 17, 2021, 05:38:59 AM »
Thanks Joe!

I hear you should go for the hull-less variety - makes for better eating and less picking hulls out of your teeth!  :Lol:

Kim

Offline kvom

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1340 on: October 17, 2021, 07:40:21 AM »
I missed where you drilled the bar supports.

That precise measurement of the spacing if matched by the matching spacing on the cylinders should mean that the bars go on parallel.  Once the yokes and tie plate are assembled to the frame will come the most exciting part since the check on driver quartering.  Smooth travel of the cross heads is the goal.

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1341 on: October 17, 2021, 07:32:50 PM »
I missed where you drilled the bar supports.

I drilled those before they were soldered in place - see post #1324 (https://www.modelenginemaker.com/index.php/topic,8552.msg242493.html#msg242493)

That precise measurement of the spacing if matched by the matching spacing on the cylinders should mean that the bars go on parallel.  Once the yokes and tie plate are assembled to the frame will come the most exciting part since the check on driver quartering.  Smooth travel of the cross heads is the goal.
Fingers crossed...  (we need a "fingers crossed" emoji! Something like this: )

Kim


Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1342 on: October 18, 2021, 11:47:41 PM »
Moving forward on the guide yokes I trimmed the bottom end to length and thinned the 1/4" square crosshead guide brackets to the same width as the crosshead guides, which is 0.236Ē.


And I have to open up the vertical holes in the crosshead guide brackets to be 3-48 clearance holes.  I used a gauge pin to center on the hole:


Then drilled #38 through both of the brackets.


I had a lot of trouble figuring out how to make the curved pattern on the yokes so I ended up drawing it on paper using a compass, as best I could (Kozo doesnít really give you clear info on this.  Probably because it isnít critical.)  Then I cut out the shape and used spray sticky glue to attach the template.  In this picture, the brass screws are holding the two yokes together left & right, back to back, just as before (but without double-sided sticky tape this time :)


After I figured out how to hold it in the mill vice, I used a 3/8Ē roughing mill to remove the bulk of the material for the opening between the guide brackets.


And cleaned up the last bit with a 1/2" 4 flute end mill.


Now for the curvy bits.  I used the belt sander and a bunch of files to finally get the shape put in these parts.


And after a little cleanup work, here are the two completed guide yokes.


Now attached to the tie plate ready for installation on the chassis!


Oh, shoot.  I just remembered.  I still have to drill and tap a few holes in the top for the running boards.   So, Iím not as done with these as I thought. Well, it wonít get done today.  But soon!

Thanks for taking a look,
Kim

Offline cnr6400

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1343 on: October 19, 2021, 12:12:03 AM »
 :ThumbsUp: :ThumbsUp: :ThumbsUp: :popcorn: :popcorn: :popcorn:

all yoking aside they look great!  :Lol:

Offline crueby

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1344 on: October 19, 2021, 12:21:57 AM »
Great results!    :popcorn: :popcorn:

Offline Dave Otto

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1345 on: October 19, 2021, 12:43:52 AM »
Nicely done Kim!

Dave

Offline Don1966

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1346 on: October 19, 2021, 01:28:20 AM »
 :Love:


 :cheers:
Don

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1347 on: October 19, 2021, 04:58:11 AM »
Thanks Cnr, Chris, Dave, and Don!  Appreciate you stopping by for a look  :cheers:

all yoking aside they look great!  :Lol:

Cnr, you better run now, I just saw the pun police go by!

Kim

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1348 on: October 20, 2021, 12:21:15 AM »
My goal for today was to finish up the yokes and get them installed.

There were TWO things I had left to do Ė the first was to mill out a little clearance notch (similar to the one done on the tie plate), and the second was to make the screw holes for the running board.

To make the clearance notch, I put the yoke in the mill vice at a 35o angle and made the cut.  Easy peasy.


Making the screw holes for the running board was a little harder.  I SHOULD have done this before I rounded things off yesterday.  That was my plan, but clearly, I forgot. SoÖ plan B is to mount things in the vice as vertically as I can, like so:


Then drill the mounting holes.  I tapped them 3-48 too, but no pic of that.  But trust me, I really did it.


Now the hard part begins; making the crossheads slide well in the crosshead guides.  Kvom warned me that this was an arduous process, and heís right.  I spent the rest of the day getting this working.  Luckily, I only had a few mishaps.  Unfortunately, I had a few mishaps.

The first thing I learned was that you canít install the yoke plate when itís all screwed together.  It wonít get past the rods.  So, I mounted the tie plate to the chassis and went to put on the yokes one at a time.  Unfortunately, you canít access the bottom screw with the front drivers in place.  So they had to come out.  Luckily, I was able to disassemble the front bearings and swing the wheels out of the way without dismantling everything.

But with the yokes in place, the front wheels lost ALL their movement.  They are supposed to be able to wiggle back and forth a few degrees.  But there was barely any movement at all.  Look at the paper-thin gap between the back edge of the wheel tread and the bottom of the yoke plate.  Not good.


So, back out they came and I filed a little angle across the bottom there.  If Iíd known this, I might have done it in my mill set up earlier.  But at this point, I decided a little file work was just fine.  With that done to both sides, Iíve not got several degrees of movement back in the front wheelset.  Yay!  ;D



Now, on to installing the crosshead guides between the yoke and the cylinders.  The guides went in great.  But once I got them installed, things moved very poorly.  The crossheads were super tight and hard to move.

So I spent quite a bit of time fettling things here and there to make them move.  Turns out the main culprit was that Iíd left the inside of the groove in the top and bottom of the crossheads freshly machined. Once I took the edge off those groves (all around) they slid quite smoothly back and forth across the guides.

Unfortunately (yeah, another one of those) one of the things I tried early on was to widen the spacing between the guides.  I did this by filing a bit off the upper mount; and thought it was helping. So I did it a little more.  Tuned out not to have any effect whatsoever other than to make things sloppy and wiggle up and down.  Not what I wanted.  So I currently have a brass shim in place there to bring it back where it was before I went all file happy on it.  I wished I'd just left that completely alone  :wallbang:

Anyway hereís a pic of where I ended up:


And a short video to show it all working as intended!  :cartwheel:

Now back to the sad part.  :hammerbash:  Hereís the side with my bungled attempt to fix things where I now have a nice shim installed.  Iím considering if I should leave it like this, or if I should silver solder a little piece in place there and make it look better.  Thatís probably what Iíll do.  I just donít want to mess up the parts that are already soldered in place.  But I think I can do it.  Any other thoughts on how to make this not look quite so stupid?


Thanks,
Kim




Offline Dave Otto

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1349 on: October 20, 2021, 12:42:32 AM »
Nice motion Kim!

My first thought on the shim would be to make it from steel and bond it place with some JB clamped up tight. Make it a little oversized so it could be dressed back down to the original surfaces.
Silver solder would be ok but there is always some risk involved with something going wrong on your finished part.  :wallbang:

Dave