Author Topic: Pennsylvania A3 Switcher (Kozo)  (Read 327863 times)

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #510 on: December 10, 2019, 05:12:29 AM »
Thanks Kerrin and Stuart.  Appreciate the commiserations and kind words both!
Kim

Offline mike mott

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #511 on: December 11, 2019, 12:31:39 AM »
Hi Kim, Ah that sucks! I agree that it is often much faster to start over that trying to fix some problems. Plus I agree with all the comments about quality cutting tools. I have even seen a drill bit unwind  :facepalm:

Looking forward to the new parts.

Mike
If you can imagine it you can build it

Offline fumopuc

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #512 on: December 13, 2019, 07:53:19 PM »
Hi Kim,  some very nice and sucessfull fabrication work is going on there.
Kind Regards
Achim

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #513 on: December 14, 2019, 06:08:46 AM »
Thanks Mike and Achim! :)
Kim

Offline Roger B

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #514 on: December 14, 2019, 03:41:00 PM »
I have been caught like that  :(  and now only buy good (expensive) drill bits and reamers.
Best regards

Roger

Offline crueby

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #515 on: December 14, 2019, 04:39:52 PM »
Kim, I have had great results with the cobalt drill bits from these guys, all sizes available single, some in 6 or 12 packs. I used theirs to replace some of the worn out ones from my set.
https://www.aircraft-tool.com/shop/detail.aspx?PRODUCT_ID=012-50
Good prices but still very good quality, much better than the silly-putty ones from the home stores!
Chris

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Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #516 on: December 15, 2019, 06:32:52 AM »
Thanks Roger!  Good tools make a big difference to the enjoyment for sure.

Thanks for the link Chris.  Looks like an interesting place!
Kim

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #517 on: December 29, 2019, 06:15:53 PM »
I’ve had some time off around Christmas and have had more shop time than usual.  Because of this, I’ve been able to catch back up to where I was before I decided to re-do the horseshoe assembly.

I didn’t take many pictures here because we’ve been through all this before. But, I did want to talk about what I did differently this time around.  The quick summary would be that I was just more careful.  The reality has a lot more detail.  This time I knew what to be more careful about!

One of my issues was that I didn’t allow for the 0.040” difference in the radius for the top horseshoe member compared to the bottom.  So, this time, when bending the top, I wrapped a piece of the 0.040” sheet around the 1-1/4" mandrel it to make up for that difference. I didn't do that last time.


And I made sure that the top and bottom members had the exact same shape, with only that 0.040” difference.  It might be hard to tell what’s going on in this picture, but the TOP horseshoe member (prior to making the horizontal bends) is sitting directly on top of the bottom.  You can see that 0.040” cutout all around the inside edge of the top member.


The next thing I did differently was to leave some material to make a radiused flange on the verge board.  This helped make sure there were no gaps around that radius.  This was a big problem for me with the first version.  (Kozo’s plans show to cut the tab out of the radius section completely – I liked this method MUCH better).


Finally, and the biggest difference this time around, was how I assembled all the elements.  The first time, I assumed the top and bottom horseshoe members defined the shape, and I made the vertical board fit them.  Then, after getting everything screwed together,   I filed off the excess from the vertical board to make it match.

The second time around I reversed that.  I made the vertical board nice and square and made it the EXACT correct height.  I made IT define the height and the basic shape. I then attached the horseshoe members to the vertical board, using the vertical board as a guide for keeping things square.  This process resulted in a much better-finished product.

Here I’m shaving the height of the vertical board to get it close to the correct height.


With a final pass of the mill to clean things up and get it exact and square.


And here it is, all screwed together and mounted in place.

Interestingly, you can see a little gap between the top member and the bottom member in the lower-left corner of this picture. This shows that the length of the upper member was about 1/16" too short based on all the numbers in Kozo's plan.  I was VERY careful to get the exact right lengths.  But those bends just put a bit of a monkey wrench in things and make the lengths somewhat difficult to predict.  Using the vertical board as the reference was the key to getting this assembled square and accurate.

The other thing I did differently is that I didn’t soft solder the horseshoe parts together – yet.  Kozo has you do that at this point.  But another problem I was running in to was that I didn’t have access to drill and tap holes for mounting the front boards.  I will wait until the whole tank is complete before I solder things together.

This brings me back to where I was about a month ago. But in much better shape I believe :)

Thanks for watching me struggle,
Kim

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #518 on: December 29, 2019, 06:22:13 PM »
Now, to continue on with the Front Plates!

Here’s where we left the front plates – I’d cut them and made notches to fit around the verge board.  And now I need to form the curve so I can cut them to size.  So, I’m just about to anneal the plates before bending.


After bending, I cut them to length on the front. Then I kinda flattened them out again to emboss the rivets.  Kozo says to emboss the rivets before bending, but I couldn’t figure out how to get the right length without bending.  So I did it this way.

And here I’ve got it marked (on the back) for rivet locations.  It’s just the horizontal location.  I figured the distance from the edge would be set by the embossing jig.


And here I am embossing the rivets all around the outside edge of the part:


Ah yes, one other thing – based on some excellent advice from Mike Mott, I made a new die with the rim of the die set to the size to set the spacing correctly.  This worked a treat! And even though I marked the locations of the rivets, I wouldn’t have had to.  This produced very regular spacing.


After embossing the rivets I re-bent the panels into place:


To attach the front panels to the tank base I needed to make the front corner members.  These are short lengths of 1/4" square brass.  They have to have a little notch cut out of them so they go around the copper sides.


Then I drilled and tapped a 3-48 hole to mount them to the base.  This I a picture of a tinny little tap handle (only about 1.5” long) that I purchased recently from Little Machine Shop.  It is the greatest thing since sliced bread!  I just love it!  It gives you enough leverage to tap these little holes, but it gives you a LOT of control.  And it's so light I’m not nearly as worried about breaking the tap!  A very good investment, I’d highly recommend it.


Here’s the pair of front corner members:


And now, after they have been screwed in place.


Next, I need to cut the top edge of the front plates to length.  Here’s how I marked those for length:


Length marked on both sides:


That pretty much gets my build log up to date.  A bit more to go on the front plates, then it's on to the top plate, and we’ll have the basic form of the tank completed :)

Thanks for following along,
Kim

Offline b.lindsey

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #519 on: December 29, 2019, 06:36:44 PM »
Impressive as always Kim. Sorry about the redo, but you seem much happier with things now which is good!!

Bill

Offline crueby

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #520 on: December 29, 2019, 07:13:10 PM »
Those rivet patterns came out great!
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Offline cnr6400

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #521 on: December 29, 2019, 09:04:50 PM »
Great work Kim!  :ThumbsUp: :ThumbsUp: :ThumbsUp: :popcorn: :popcorn: :popcorn:
"I've cut that stock three times, and it's still too short!"

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #522 on: December 30, 2019, 05:30:28 AM »
Impressive as always Kim. Sorry about the redo, but you seem much happier with things now which is good!!

Bill
Thanks Bill!  I am much happier :).  There are still things that could be better, but it passed the 'good enough' point on my quality meter, so we're going forward!

Thanks,
Kim

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #523 on: December 30, 2019, 05:31:05 AM »
Thanks for following along Chris and CNR :)
Kim

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #524 on: January 01, 2020, 06:23:05 PM »
To finish off the front plates, I need to silver solder some little tabs onto the top end of the plates.  This will help the joint with the top plate that is coming next.

So, here’s one of the front plates all setup to hard solder the tab in place:


And after the soldering is complete.  This went well.  I’m getting much better at this.  Guess practice really does help!  I’m quite enjoying the silver soldering now.  It’s quite satisfying!


With the fabrication completed, all we have left is to mount them to the tank. Kozo recommends #0-80 round head screws.  I marked 10 locations around the rim and drilled right through the faux rivet for these mounting screws.


Then marked the first holes on the supporting structure and drilled and tapped.


Here’s a picture of one of the many front plate fittings needed to mark the spots for the screws.  I marked them one or two at a time.  Notice that the Verge Board has been removed and I’ve got a few scraps of 0.040” plate stuck in those holes to fill the gap.  If I’d soldered it all together already, I would not have been able to remove it and I don’t know HOW I would have been able to drill and tap those mounting holes!


Drilling through the copper tank sides after marking:


And tapping the receiving holes for the #0-80 screws.


This process involved a lot of steps for each screw (marking, drilling, tapping, re-fitting, repeat). So a lot of assembly and dis-assembly.  Interestingly, these little #1 and #0 brass screws aren’t all that sturdy. You don’t have to work very hard to just twist their little heads right off!  Needless to say, I did that several times.  Usually, I could grab the exposed part of the screw and unscrew it with some vice-grips.  But sometimes there wasn’t enough of a nubbin exposed to get a hold of, so I had to drill it out. This picture commemorates one of those events. I’m drilling out the middle of the #0 screw with a #58 drill bit.  Then I used a cutting tap to remove the remainder of the screw.  Not a big deal, but it all takes time.  I’m learning to be a little more ginger with these teeny-weeny brass screws!


Last, but not least, I marked, drilled, and tapped mounting holes for the front corner members.  This picture shows the left side installed, and the right side sitting next to it, waiting to be installed.


And here’s the front plates, fully installed.


Next up is the top plate, and it will start to look like a tender!
Kim

 

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