Author Topic: Pennsylvania A3 Switcher (Kozo)  (Read 327671 times)

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #885 on: December 19, 2020, 04:12:27 PM »
Thanks for the comments Roger and CNR!
Kim

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #886 on: December 21, 2020, 08:39:41 PM »
Chapter 11.2 – Bushings

The next parts are the split bushings for the engine axles.  There are four of these, all the same.  They are made from 1” round 932 Phosphor Bronze.  I ordered 3/4" for these, but it seems like that was a mistake.  The OD for the flange on these bushings is 3/4" but they are split, which will take a little extra out of the middle.  I must have missed that fact when making my material list since 3/4" just won’t cut it.  Well, it might… because the bronze rod always comes about 20-30 thou oversized. But even if I could keep my slit under that size, I’m worried that soldering the halves back together will be off by a few thou and I just won’t have room to true it up.  So, I went with the next larger size of bronze I have, which is 1”.  Luckily, it only takes a few inches of the stuff and I have enough.

So, the first move is to cut a few inches (about 3) in half.   I measure carefully and used a 0.040” slitting saw (after all, I’ve got a ton of extra wiggle room when using the 1” size!)
I cut from both sides so that I had it separated in half all the way up to the marked line.


Here’s what it looks like right off the slitting saw.  Very nice finish, actually. I’d thought I might have to mill the middle flat but this seems plenty flat to me. The two halves fit together very well!


Here are the halves fluxed up with some flattened solder on the.  I’m using soft solder for this operation.


Now sitting together with a little weight on top to help push them together.  I’m hoping that the halves don’t slide too much when the solder melts.  Guess we’ll see.  I’ve got some room to play with anyway.


Turns out it went quite well.  You can see that the back top half slid a little to the left there, and the front slipped a little to the right.  But not much. Well within my tolerances, though probably not if I’d gone with the 3/4" bronze though.


Now off to the lathe where I centered the newly joined halves as best I could using the 4-jaw chuck.  The most important part was to make sure the centerline is in the middle.  The other dimension is less important but I still wanted to get it close-ish.


Then I cut it down to 3/4” OD and drilled a 3/8” hole in the center.  From there I used a boring bar to open it up to about 0.415” (a little under 7/16” or 0.4375”).


Followed by reaming to 7/16”.


It was at this point I realized my error.  I DID realize the bushings were split and I DID order the right material.  I was misreading the drawings NOW, not then.  Looking at the drawings I misread the 0.075” as 0.75” for the diameter of the flange.  But really, it’s the width of the flange 0.075”  (silly little order of magnitude mistake).  And of course, the diameter of the flange is 11/16”. So I could have used the 3/4" phosphor bronze.  Ah well, what’s a little extra phosphor bronze swarf laying around, right?  :insane:


So, NOW I take it down to 11/16” OD.


Then cut the main part of the bush to 9/16” and cut it off leaving a tad extra on the flange.


After repeating that four times, I then popped each of the bushings into a 9/16” collet and faced it off to the proper width.


Now, to un-solder the bushing halves.  I mistakenly thought that by suspending them like this, the weight of the bush half would separate it when I heated them up.  Unfortunately, no. I had to poke at them with something to get them to separate. But that wasn’t too hard, and they did all come apart.


With a little cleaning up, they look almost presentable.  I also marked the halves so that I could keep them together.


Kozo’s directions have you use Loctite to hold the upper half of the bushings in place.  Here it’s the lower half because things are sitting upside down.  Also, he has you put a piece of paper in-between the lower half of the bushing and the axle cap, then ream the bushings again. This will give a little extra space so that the axels spin well even when the axle caps are tightened down.  At least, that’s the theory.


And here they are, all in place.


That’s actually a lot of work for those little guys!

Thanks for taking a look,
Kim

Offline crueby

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #887 on: December 21, 2020, 09:17:42 PM »
Great work on little but very important parts!

Offline cnr6400

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #888 on: December 21, 2020, 10:55:52 PM »
Hi Kim, a handy trick for separating soldered halves type parts, like your bushings: use a pair of expanding type e-ring pliers to pop them apart while heating. You want the pliers that remove external e-rings, where the ends expand. Did that the last few sets of conrod bearings I made. Your chassis is coming together!  :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 #889 on: December 22, 2020, 05:36:35 AM »
Thanks Chris and CNR!

Hi Kim, a handy trick for separating soldered halves type parts, like your bushings: use a pair of expanding type e-ring pliers to pop them apart while heating. You want the pliers that remove external e-rings, where the ends expand. Did that the last few sets of conrod bearings I made. Your chassis is coming together!  :ThumbsUp: :ThumbsUp: :ThumbsUp: :popcorn: :popcorn: :popcorn:

Good tip, CNR!  I was trying to think of something like that.  Clearly, the parts are too light for the gravity assist I was hoping for, so something like the e-ring pliers is a great idea!

Kim

Offline Roger B

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #890 on: December 29, 2020, 06:51:31 PM »
Good work  :ThumbsUp:  :ThumbsUp: I see you have numbered each pair. I tend to use a largish (75w) electric soldering iron for soft soldering split bushes.
Best regards

Roger

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #891 on: January 02, 2021, 06:48:44 PM »
Chapter 12.1 – Driving Wheels

In chapter 12, Kozo describes how to make a pattern for the drivers and tells you to send it out to a foundry and have some cast for you.  I know you can get a set of driver castings from the Friends Yankee Shop Models ( http://www.friendsmodels.com/productsforsale/kozowheelsdrivers.html), but I want to make my engine completely from bar stock.  Not sure why, I just want to.  So I came up with this idea for how to make the drivers.  My hope was to complete one to show it was possible.  I still believe it’s possible, but I’m not there yet, and it's time to let you all in on my foibles and progress (or lack of progress :)).

The first thing I did was to make a jig to help me with making the drivers.  This jig allows me to create a radius with the center outside the driver.  It might not make much sense yet, but in the next post, you’ll see how I use it.

I needed two 1/4" pins spaced exactly 5/8” apart.  This will be for the center of the hub and the crank pin.  I will use these holes to keep the wheel aligned during machining.  Then I need a way to locate the center of my radius that is outside the driver.  I did this by drilling and reaming a third 1/4" hole.  It wouldn’t have to be 1/4", but for simplicity, I kept them all the same size.  Here’s a hunk of aluminum I had that I’m using for the base of my driver jig with the three holes drilled and reamed:


Then I made two 1” pins to fit the holes.  I used 1/4" 12L14.  This was a nice fit in the 1/4" reamed holes.  But I needed the pins to stay in place.  So, my idea was to knurl a bit on the end of the pin so that I’d get a nice friction fit.


Unfortunately, that was WAY too tight. For the first pin, I tried to use my 1-ton press to get it to go in, but that wasn’t working – it wasn’t going in straight.  So I brilliantly used a hammer and pounded it in.  Took a lot of pounding but I won!  I got it all the way in. For the second pin, I was smarter and chucked it back in the lathe and filed off most of the knurling.  This one went in better, but still, not as easy as I’d have thought.

Guess it doesn’t take much ‘interference’ to make a good friction fit, eh?  The pin on the right is the first one. And what I didn’t think about is that all my pounding REALLY changed the shape of the pin.  It isn’t straight, it isn’t round, and it isn’t 1/4" anymore.  And this picture was taken after I’d done some filing to get rid of the mushroom head I’d put on the pin.  But again, that didn’t help much cause the whole pin was fatter and shorter than it had been before.  Good lesson learned here! Don’t use a friction fit if you want to keep a pin a specific size!


With that lesson learned, I drilled out the deformed pin.   The remaining hole was now 6-7 thousandths over 1/4", so a new pin would wobble around in there way too much.  To fix this, I drilled out the hole, tapped it 3/8”-24, and made a 3/8” aluminum plug that I screwed and Loctited in place.  After that set, I milled it flat and drilled & reamed a new 1/4” hole in the plug.


At this point, I realized that having two close-fitting pins on a part like this might make it hard to get the workpiece on and off.  So I decided to make a removable pin to use for this second one.  So that’s what I did.  And I used Loctite to attach a little handle to the pin so I could get it out easier too.


OK, now, finally, on to making an actual driver!  The drivers for the A-3 are 3 7/16” in diameter at the flange.  So I used 3.5” round bar (12L14) for this and set up the saw to cut a 1/2" slice from the loaf of steel.


It was doing just fine till it got to some point and just wouldn’t make any progress. I fussed around with the saw trying to get it to cut more – the blade was still going around, but there were NO metal shavings coming out the backside.  None at all.  So I finally unclamped the piece and rotated it about 20-30 degrees.  I used the existing kerf to keep things lined up.  And then it would cut again, for a while.  Then it stopped again.  I went through this process 3-4 times till I finally saw what was happening!  The inside blade guide roller was hitting the clamp!  You can almost see that here (it’s the one in the back).


And here’s another picture from over the top of the blade.  Anyway, once I figured that out, I moved the guides a few inches to the left to give it more clearance and all was good.

You can see the pretty pattern that resulted from me rotating the stock during the cut.


Then to the lathe where I faced one side of the slice:


Drilled and reamed a 1/4" hole in the center:


Turned it around and faced the backside off to exactly 1/2".


Then over to the mill where I drilled and reamed the 2nd 1/4" hole, 5/8” from the center.


And now you can see how it sits in my jig:


Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #892 on: January 02, 2021, 06:53:36 PM »
With the jig made and a wheel blank ready, I clocked in the rotary table using the coaxial indicator:


And using a 1/4" gauge pin, I centered the distant hole on the rotary table.  I used the square as a way to align the jig with the table so I knew that the crank-pin was aligned.


Then, using the rotary table and a 1/4" mill, I cut an arc, 7/16” deep.  This arc defines the lower part of the weight on the driver.


Next, I re-centered the jig so that the center pin was exactly over the center of the RT and cut a similar arc all around the inside of the driver rim.


Then cut an arc around the top of the hub:


Now, using the same trick to center the crank-pin hole over the center of the RT. Again, I used the square to keep the jig aligned at the same angle to the RT.


And cut a radius around the lower part of the hub.


Then I carefully joined the upper and lower hub sections.  The sides are just about 11 degrees off vertical.


Next, I re-centered over the middle hole (I will improve these steps to require fewer re-centering operations :)) and removed all the excess except for a 1/8” wide arc close to the outer rim.


Then, I cut that down to only 1/8” high.  The reason I leave this raised section is that it will help hold the spokes at the correct height.


Then I did the same to the other side.   With this, the major shape of the driver can be seen.  The rim, the weight along the top, and the hub.


Next, I used a 1/8” ball-nose mill to cut grooves for the spokes.  There are 12 spokes, each 30o apart.  And they are offset 15o from vertical. Here I’ve cut the first two grooves for the spokes.


Now all 12 spoke grooves are complete.  (This did require some clamp leapfrog work.)


And here’s the state of play.  The side you are looking at will be the back of the driver.  The front will be the other side and the 1/16” of steel left on that side will be removed, revealing the spokes, inset by 1/8”.  My thinking in doing the hub, rim, and weight as one piece like this is that I should be able to attach the spokes and maintain things in the right dimensions so that the wheel will still be round.  It’s like a built-in jig for keeping the hub centered to the rim.

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #893 on: January 02, 2021, 07:08:05 PM »
Next, I need to make the spokes.  They are all made from 1/8” x 5/16” CRS (1018).  I used a 1/16” round-over mill to round off the ends of the spokes.


Then round off one of the long edges.  This will be the front side.  It will face down in the wheel I’ve just made and the rounded side will mesh with the ballnose shaped hole.


Here are all the spokes completed.  Note that four of them needed to have both ends rounded.


I also needed to round off the corner where the two round-overs meet.  Unfortunately, I started rounding off the ends that needed to be square on a couple of them, so needed to re-make those.  But you get the idea here.


Now for the big step – soldering the spokes in place.  I’m all set up on the hearth with flux and solder…


And quite sometime later, I have this charred piece of junk :(  It did not go well.  By the time I got the rim (especially the weight section) hot enough, the spokes weren’t hot enough.  I had to blast heat from the top to get those since there is no access through the bottom.  I worked at it for a while with my standard welding tip (#1 I think).  But eventually moved to a rosebud (#4).  That worked better – got a lot more heat a lot faster.


Anyway, left it to cool and then in the pickle.  Here’s what it looks like after several hours in the pickle.  You can see that almost NOTHING happened with the hub joints.  And only one of the outer joints looks like it has a decent solder job.  A few of the outer spokes seem to have been soldered to some degree.  But not most (though I intentionally stopped before I got around to most of them).


Unfortunately, one of the outer rim joints that DID get made, came out in the wrong place!  I didn’t think they’d move. And they didn’t… much.  Just a little bit.  But its enough to make the spokes not align, and I don’t like that!


So, my assessment*:
1)   The wheel has so much thermal mass it's hard for me to get the whole thing hot enough, fast enough.
2)   I can’t heat the spokes from the underside at all.
3)   I tried to do too much at once.   I should have focused on a few joints and tried it again for the next ones.  Doing all of them at the same time was a BAD idea.
4)   I should have had a way to keep the spokes from moving while soldering.

I may try and play with this experiment a little more – see if I can clean it up and get some better joints out of it.  My problem is that it's hard to get into the places you need to in order to clean up the joints for another go.

Anyway, that’s where I’m at. And that’s where my soft solder/powder coating question came from.

Thanks for taking a look and for any thoughts or comments you may have.
Kim

*I’ve learned all these lessons before.  Guess I just was so worried about heating up that whole thing that I didn’t want to do it multiple times.  In retrospect, that was silly, wasn’t it?


Offline cnr6400

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #894 on: January 02, 2021, 07:35:35 PM »
Hi Kim, even though your soldered assembly was not successful, I'd say this was an excellent attempt and that you learned a great deal from it. That in itself is a big win. I am sure with more heat (and maybe using a high heat black flux) your next ones will be golden.  :cheers:
« Last Edit: January 02, 2021, 09:53:02 PM by cnr6400 »
"I've cut that stock three times, and it's still too short!"

Online tghs

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #895 on: January 02, 2021, 08:28:16 PM »
were you using any firebricks to help keep in the heat?
what the @#&% over

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #896 on: January 02, 2021, 09:57:41 PM »
Thanks, CNR, that's what I'm trying to tell myself :)

Tghs,  good thought.  I'm sitting the item on firebricks, but mostly it was supporting.  I should try putting some on the sides and behind.  I just like to be able to get the torch all around the item so I'll have to learn a different technique to make that work.  But I guess that's the point, right?  The techniques I've been using don't work for this, so it's time to learn something new!

Kim

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #897 on: January 10, 2021, 07:56:43 PM »
This weekend I took a second try at silver soldering the wheel assembly. 

I did my best to clean it up some using various files and then set it up for another round with the torch.  Forgot to take a ‘before shot’ but here it is just after the soldering session.


What I did differently:
  • I used Harris Black flux– Order it off Amazon and arrived just in time!
  • Next, I started with a #4 rosebud tip – puts out a LOT of heat quickly, and in a broader way – not so focused or concentrated as the standard #1 or #00 welding tip I often use
  • And finally, I did the stuff I already knew to do, but didn’t do last time – like use gravity to your advantage, and only do a few joints at a time, rather than trying to get them all at once.

And, as one might expect, it worked far better!  The biggest difference, I believe, was the black flux.  It really stays around much longer than the white flux.  And I focused on a few joints along the bottom rim and a few along the top of the hub.  With the part set up this way, I was able to get below and behind the part which made for better access for applying heat too.  I stuck a length of 1/4" steel in the hole to help provide some stability so the wheel wouldn’t fall over.  It seemed to work.

After I completed those few joints, I left it to cool, then a while in the pickle, and cleaned it up again for another run.


This time, I did another set of joints, then rotated the wheel a bit, and did a few more.  In this way, I actually completed the rest of the joints in that session.


Another thing I did differently was to apply the solder after heating the part, rather than ahead of time as I normally do.  Not sure if that was better, but it allowed me to do more joints in one heating session that way.  I also found that dipping the solder in the black flux, then applying some directly to the hot joint seemed to help some.  Not sure it was the best, but it seemed to work OK.

Here’s a couple of close-ups of the wheel after it was pickled for several hours.  Not perfect joints, but getting better.  I think my next wheel will be even better!


You can see a few here that don’t look complete, and some that look kind-of like ‘cold’ solder joints, like the solder didn’t really flow very well.  Not sure if that was a flux problem or a heat problem.


Anyway, my plan is to go forward with a few more steps on this test wheel.  It is, only a test.  The spokes are too far out of whack so it's not worth perfecting this one anyway.

Thanks for taking a look,
Kim

Online tghs

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #898 on: January 10, 2021, 08:11:09 PM »
looking better,, soldering can be a hard learning curve!! then there are those days when everything should be perfect and it still doesn't work :wallbang:
what the @#&% over

Offline matthew-s

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #899 on: January 10, 2021, 08:30:00 PM »
That is quite the journey! I wimped out and bought the casting - and finishing those nearly killed me!

Keep up the good work.

 

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