Pennsylvania A3 Switcher (Kozo)

[Johnmcc69]

 
 Looks great Kim! A beautiful piece in itself, the tender.
 Looking forward to the loco build. You've really developed your skills in
Model making.  "2 snaps up"
 
 John

[Kim]

Thank you Joe and John!
Appreciate your kind comments 
Kim

[scc]

Looking really good Kim       Are you doing Elvis impressions singing "love me tender"?          Terry

[Kim]

That's a groaner   

Thanks Terry!
Kim

[Don1966]

Nice job on the lettering Kim it’s looks awesome!.....


 
Don

[propforward]

Wow Kim - just wonderful! Beautiful job!

[Kim]

Thanks Don and Stuart 
Kim

[Kim]

Over the weekend I was able to kind-of complete the side frames.  I say “kind-of” because I can’t fully finish it till am ready to separate the sides.  And I can’t separate the sides till I complete a couple of other pieces.  So full completion is a ways out yet.  But it's good progress regardless of how you slice it.

After completing the five-sided hole for the steam-tee, I started to clean up the cutouts for the wheel bearings.  The front one is fairly deep and we took a chunk out with the saw. All I have to do is clean up the sides and bottom to more precise dimensions with the mill.  I was very careful to leave the radius from the place where I'd drilled out the corners.  Just used some careful math and the DRO to accomplish that.


I wasn’t smart when putting the frame in place for the previous operation so had to reposition it to cut out the hole for the front support.  Here I’m using a 3/8” roughing mill to take out the bulk of the material (I didn’t bother to saw this little chunk out).


Then cleaned it up to more exact dimensions with a standard 3/8” mill.


And finally, I cut the grooves on either side of the front cut out.


And now, before I complete the sides, I need to make the parts that go over these two axle holders.

Kim

[Kim]

Chapter 10.2 – Pedestal Braces

The first of these parts is for the front axles. The Pedestal Brace is the one on the left.  The taller nubbins on either side will fit into the grooves that I just milled in the frames.  The one on the right is the Rear Axel Box – that one will come later.


To start with, I took one of the pieces that I cut out of the frame – it is still double sticky-taped together, which is perfect.  I started by cutting the piece in two.  One part will be used to make these Pedestal Braces and the other part to do the Rear Axle Box.


Using the longer piece, I milled it to the appropriate length and thickness, then cut shaped the part as shown in the diagram:


Then drilled mounting holes.  I drilled them to the size I need for taping #3.


After that, I flipped the parts over and fit them into the place they go on the frames. Using the mill vice to hold them in alignment, I drilled the mounting holds into the sides using the ones in the pedestal brace as a template.


Then I took the pedestal brace and drilled the holes out for a close fit for a #3 and countersunk for the heads of the mounting screws.


And finally, tapped the holes in the side frames.  Here are the completed Pedestal Brace parts connected to the frame.



I was starting on the Rear Axel Box next – I had the part milled to size and shaped, and was just starting to drill the mounting holes when I had an unfortunate accident.   As the drill broke through the bottom side of the part, I didn’t stop my quill action fast enough and heard a nasty grinding sound.  I’d run the chuck into the part. And it took a pretty good gouge out of the top of the piece too.  (see the semi-circular shape on the top of the piece?  That wasn’t intentional )


I had “hoped” to complete this part before I stopped, but clearly, I was hurrying too much and this is the silly kind of stuff that happens when you hurry.  So, it was time to pack it in for the day.

I’m thinking about whether I can use the part anyway or not.   It's not like it will be seen, but one of the sides of the bearing holder will be shorter than the other by a few thou.  Is that bad? 


I was initially thinking I could just go ahead and use it. But now I’m worrying that if it is uneven then it might pinch the bearing some, which wouldn’t be good.

And if I’m going to re-do it, now’s the time!

Any helpful hints or suggestions?

Thanks,
Kim

[Admiral_dk]

I can't see if it will be tightend against the missing bit or the two other flat faces where the screws will be - but this make a big difference ....

At least it's a smal and simple part you had the accident with and not one with a lot of work done to ....

Best wishes

Per

[cnr6400]

Hi Kim, how about building up the gouged area with a bit of silver solder, then mill to the .379 dimension and finish the machining. I don't think the two top points see a lot of load, but it is probably a good idea to have metal there as Kozo intended.

(And set the drill further out in the chuck for the next one......)   

Just food for thought.

[Dave Otto]

Hi Kim

If those two little surfaces don't contact anything I would be inclined to take a fuzz off all of them so they are all the same height and move on. If they do make contact and are part of the mechanical alignment, I would probably remake them.

Dave

[kvom]

I would use larger pieces of stock and drill the 9/16" hole first, then remove the top.

Was your plan to use a rotary table?

[Kim]

Thanks everyone for the thoughts.

Per, I'm also not sure what will be tight against what.  I'm kind of thinking that those peaks hit, but not the flats since the hole is 0.375 deep and the peaks are specified to be 0.379 tall.  So that would mean those peaks hit first and the flats won't ever quite meet.  And if the peaks aren't there, then it will squeeze the bearing.  And if this is true, then they should touch bottom, which means I shouldn't take a few thou off, because that's all the height difference I need.

So taking Dave's advice, I think I'll just re-do.  As was mentioned, at least they are fairly simple (and small) parts and won't take long to re-do.  I've certainly re-done much more complex items! 

KVOM, the way Kozo shows is to attach these two parts where they belong, THEN drill the hole with it bolted in place.  That will give the half holes in both the frame sides and this rear axle holder piece.

Thanks for your thoughts.  I'm off to the shop to make it happen now!  I'll report back later.
Kim

[Kim]

Chapter 10.3 – Rear Axle Boxes

When I got out to the shop this morning a new idea came to me.  It’s basically what Dave said – shave off a bit of the top and go on.  But in addition to shaving off a bit of the top, I shaved off the same amount of the lower flats so I kept the depth the same.  What changed was the thickness of the attachment points.  And I don’t believe that dimension is critical.  It just has to be thick enough to hold the wheel bearing and axle in place and I figured a few thou less wouldn’t bother anyone.

So, I finished drilling the rest of the mounting holes then switch back to the cutter and shaved off a tad.  Turned out it took about 13-14 thousandths to clean up my little oopsie.  Then I shaved the same off the T-wings and we were good to go!  (That little tuft of white fluff is from the double-sided-sticky tape.)


Here’s what they look like sitting in place.


And I took this shot with a paper slid under the edge of the T shape to show that there TRULY is that small gap that I’d said there should be.


With the axle boxes in place, I drilled the tapping holes (#44) for the #3-48 threads.


No pics of this, but I drilled out the through holes and countersunk them for the #3 flathead screws, tapped the threads, and screwed the parts together.

With that, I was ready to drill out the 9/16” hole for the axle.
To find the center I used a laser center finder that I picked up a few years back.  It’s nice, but I’ve found the uses for it more limited than I’d imagined. But it was great for this op!


I step drilled the hole starting at 1/8” going up to 1/2".


I didn’t have a 35/64” drill bit that Kozo suggests.  My drill bit selection only goes up to 1/2”.  Beyond that, I’m limited to a cheap set of Silver & Deming bits that are only in 1/16” increments anyway.  So, I went with the boring head to open the hole up to just under 9/16”.  The finish isn’t so great, but that’s OK.


Because I’m following it up with a 9/16” reamer anyway!


And here are the completed Rear Axle Boxes.


Thanks for stopping by and for all your help!
Kim