Author Topic: Pennsylvania A3 Switcher (Kozo)  (Read 24756 times)

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #375 on: July 07, 2019, 03:17:23 PM »
Like Bill, I got the dual voltage gun.  Seemed like 2 for 1 a little more money, right?  If I need it, I'll be glad I sprung the extra $40 for the dual voltage gun (that's my theory anyway :)).

Hi Kvom, I got one of the plug sets too, though I haven't had an opportunity to use them yet.

Bill, on the high-temp masking tape - I got several widths of the blue-green plasticy tape which is what I used. But you're right - I'm not using it on a flat surface.  I'm bending around corners and doing lots of weird stuff on these parts, so it isn't a fair trial really.  It probably will make much more crisp lines on a flatter surface.

I also got one roll of the white fiberglass tape, because it came with the 'accessories' pack that I got.  Haven't used that yet.

Kim

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #376 on: July 07, 2019, 03:20:15 PM »
First order of business today was to dis-assemble everything into its constituent parts for a paint strip, in preparation for powder coating.  I took this opportunity to get a quick family shot of all parts made to date.  Doesnít look like so much when it's just sitting there. But that was a lot of work!


I decided the best way to do the wheels was to disassemble them too.  I had to heat them up to release the Loctite.


This also had the advantage of helping to strip the paint some.


Still took quite a bit of work with a wire brush and a lot of buffing with a 3M mesh wheel.  But I got them back to pretty nice condition for the powder coating.

I covered the edges with the high-temp masking tape, made little wire hangers for them, and powdered them.  I hung 3 at a time in my high-tech paint booth.  I did have to remember to move the ground clip when I moved from one to the next.  After coating them, I moved them to the rack that Iíd set up right next to the powder coating station.


When all eight wheels were powdered, I moved them to the oven to bake.  Itís interesting, watching the powder melt and start to flow.


After the baking period, I moved the whole rack out to cool.


Unfortunately, after cooling, it became clear to me that I didnít really get a thick enough cover with the powder.  A few are OK, but several just arenít even and donít have the color I want.  Itís easier to see in person, but a few you can see in the picture too, like the one in the top left corner, and the second one from the right on the top, to name a few.


Anyway, now Iíll get to try the re-coating.  Itís not any different other than it sounds like it can be a little harder to get the powder to coat well.  Guess Iíll find out! :)

Kim


Offline b.lindsey

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #377 on: July 07, 2019, 05:16:23 PM »
Interested to see how that works out Kim. I haven't tried a second coat yet either. Might be good to use the 25kV setting for the redo though. Looking forward to seeing the results.

Bill

Offline kvom

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #378 on: July 07, 2019, 10:54:46 PM »
A bit of a rub with scotchbrite helps with the second coat adhesion, although I haven't needed it on most parts.

Online crueby

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #379 on: July 07, 2019, 11:47:17 PM »
When you talk about the powder flowing, can a too-thick coating sag? Or does it just melt the particles into one film layer? Wondering if going on too thick could run like paint does? Fascinating stuff!

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #380 on: July 08, 2019, 05:46:17 AM »
Well, with my minimal experience, it seems that the powder melts and flows together - a little.  But if it seems to need to be pretty evenly distributed or you can get lumps - they refer to it as "Orange Peel" though this seems to have several potential causes (powder too thick, bake too long, etc.)  I've got a few not-so-ideal pictures I can share soon.  Not sure if it will run like conventional paint though.  It might if you could stack enough powder in one place.

My re-coating went pretty well.  Most of the 8 wheels came out pretty good. but one I fussed around with a lot and it just kept getting worse.  I touched it with my finger once while trying to position it - that was dumb.  Big fat oily finger print right in the middle...  I cooked the other 7, and they are mostly OK - still might be a little thin in a spot or two.  But that one - I cleaned all the lose powder off and tried it again - a couple different times.

I think the concave shape of the wheels causes some problems.

Higher voltage didn't help.  Lower voltage is what most things I read recommended.  So I used the 15K setting.  The thing that actually helped the most was to turn the air pressure down.  I though I had it down below 10psi, but apparently not - it was more like 20psi, which was almost blowing the powder off the wheel.  Anyway, bring the pressure down helped the most (and getting rid of my finger print!  :wallbang:).

Pics to follow soon.
Kim

Eventually, the things that see

Online mike mott

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #381 on: July 12, 2019, 04:10:11 PM »
Good Morning Kim
I just finished reading through this entire thread, and I am really enjoying your detailed descriptions of each step. I have Kozo's book as well, and your posts have added a great deal to the work. It looks like you have some nice tooling as well. I will follow along now that I have the background of your build. Oh yes and it all looks great so far.

Mike 
If you can imagine it you can build it

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #382 on: July 12, 2019, 09:34:54 PM »
Thanks Mike!
Appreciate the kind words :)

Hopefully, me documenting my struggles can be helpful others.  It is certainly helpful for me!  I get so much amazing feedback from the members of this forum.  everything I know about model engineering, I've learned from people right here, sharing their wisdom and experience with me.

Kim

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #383 on: July 14, 2019, 11:12:33 PM »
Well, I wasnít pleased at all with my second coat either.  It was marginally better, but most wheels still had very poor coverage, as can be seen in this picture.  I just wasnít happy with the look at all.


So, I tried going back to basics.  Things just didnít seem to be getting the powder and I wondered why. So I used an ohm-meter and sure enough Ė there was NO electrical connection between my wire and the part.  And looking at the hole in the wheel I could see that it was completely coated with baked-on paint. As was the wire I used to hold it. This picture doesn't show it very well, but it is quite clear in real life.   Things are dark in that hole, which messes up the picture. But trust me, it was completely coated Ė on all wheels.


So, I took the wire out and tossed it.  Figured it was way cheaper to spend a little wire on a new hanger. Then I used a reamer to clean out the hole.  With new wire and a reamed hole, I got an excellent electrical connection.


I did this to ALL the wheels.  Then tried re-coating them.  THIS time, I made sure my air pressure was turned way down (below 10psi), AND I used the diffuser tip on the powder coating gun.  You can see that in this picture Ė itís the blue round thingy on the end of the gun (yeah, it's blue, it just has red powder all over it!). The idea of the diffuser is that it helps disperse the powder while preventing the blast of air from being so strong that it blows the powder off the part.


Also, I ended up doing the parts laying down, instead of suspended. I donít know if this made any real difference Ė my thinking was that gravity might help some. But in the end, I think the main differences was Ė 1) good electrical connection, 2) taking the powdering a little more slowly, and 3) making sure I got good coverage.


I think my real problem with my original coating was that I just didnít get enough powder on the part.  The second try I think I didnít have a good electrical connection, which made the powder not stick very well.  And with my inexperience, I didn't recognize what "enough powder" looked like.  Guess that's what experience will do for you, eh?

Here we are, baking the parts in the oven.


After cooling, I took them out and started to strip the masking off.  Itís clear my masking failed on a few of the parts Ė I think this is a result of the many coatings and re-bakings.


After a considerable clean-up effort consisting of a lot of scraping with an X-Acto knife, some wire-brushing, and the use of sandpaper on a mandrel on the lathe, hereís how the came out:


Now, after the 3rd attempt, I am happy with them :)

On to black! Everything else will be powder coated black now!

One thing left to do on the wheels though. I donít really want them to rust, and I see the steel (1018 and 12L14 Ė but 12L14 is worse) in my shop rust over time and I donít really want to deal with that.  So, Iím seriously considering spray them with a clear coat.  Just regular spray paint mind you, no powder clear coat Ė that would be too much (I donít really want that thick glossy look anyway). 

If you have any experience with this or feel that Iím planning to do something really stupid, please feel free to let me know!  But thatís my plan at the moment.

Thanks,
Kim


Offline b.lindsey

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #384 on: July 15, 2019, 12:15:19 AM »
Clear coat or an oily tool dip will keep the rust at bay Kim. Good excuse to get a dipping pot and heat soluble coating. But yeah, easy to spend other people's money, just ask Tennessee Whisky  :lolb:

Bill


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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #385 on: July 15, 2019, 12:46:26 AM »
Some great learning Kim! Guess that any new process has its key things, looking ng much better. For my Kozo Shay, had same concern with the rims rusting, also 12L14, so used some clear coat spray, worked fine.

Online Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #386 on: July 15, 2019, 05:31:18 AM »
Thanks for the input Bill and Chris,
Good to know that others have done similar.  I've used the technique on model ships to keep the copper plating from oxidizing, and it has worked pretty well, so I hope for similar experience here.
Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #387 on: July 15, 2019, 01:13:15 PM »
Ship models?  Pictures?!

Online mike mott

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #388 on: July 15, 2019, 01:48:39 PM »
Yes pictures...would be good.

Mike
If you can imagine it you can build it

Offline Flyboy Jim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #389 on: July 15, 2019, 02:36:23 PM »
The wheels came out great Kim.  :ThumbsUp: Also, I now have a better picture of the powder coating process.

I too would love to see pictures of your ship models.  :)

Jim
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