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A spy shot from the "Skunkworks"


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#1 havlicek

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Posted 22 October 2016 - 11:10 AM

One of my "Strapnut"TM Falcon conversions under development, alongside where it came from.  On this one, and just to see if there was any difference, I ordered a set of the magnets new from Scott at PCH, instead of reusing the originals... and magically they appeared at my doorstep PDQ (as always!).  Anyhow, I'll see if "my source" can score some more pictures later on when the guys in the white lab coats get further along. In the meanwhile, getting the motors is easy... basically free, and you can experiment-away untiul you land on your own recipe. One thing I will say is that (again) the sequence of steps is important here.  

 

What I do:

1 Cut the can to length (I usually go around .750")
2) Do axle clearance cuts
3) Remove the can bushing flange for a flat rear end
4) Drill the can for endbell retaining screws
5) Trim the endbell (here a PS unit) so it fits the can... they need some work on the radiused sides
6) Install the endbell and solder-in the can bearing using whatever method of aligning them you prefer, and neutralize the acid
6) THEN make the final cuts on the top and bottom flats, because the can is somewhat weaker after this
7) Do a final cleaning/deburring
8) Paint the can (if doing so at all)
9) Epoxy-in the magnets to set the airgap (*on painted cans, be extra careful not to get any epoxy on your new paint job... but it looks way better than painting the can and magnets and getting paint on the magnet tips).

Now, with a proper setup, you can build your arm. Here I see that "they" went with an itty bitty .350" stack. Yikes, that thing is sure gonna whistle!

IMG_1779_zpsmwjnbnea.jpg
 
-john


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#2 olescratch

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Posted 22 October 2016 - 07:30 PM

John, as you know, I love seeing this stuff. I would also like to see if you could provide a list of the "elements" you use.  By this I mean the type of powder coating, paint, epoxy, etc. I would hate to try and do the trial and error to find good items for these conversions. 

 

BTW, do you find the PS endbells a better choice than the Muras and if so, why?   


John Stewart

#3 havlicek

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Posted 23 October 2016 - 07:16 AM

Hi John,
 

John, as you know, I love seeing this stuff.  I would also like to see if you could provide a list of the "elements" you use.  By this I mean the type of powder coating, paint, epoxy, etc.

 
Thanks.  The powder coating I use is from two different companies.  The brown colored one is made by 3M and I no longer have the number.  After months and months of trying to get the stuff, someone right here on Slotblog got me some through work.  It's normally only available in industrial quantities and not sold through regular retail sources that I've ever seen...and I really looked.  I traded most of the container I got for some made by another manufacturer that is in the blue color.  Both are similar, although they have slightly different working characteristics and finished properties.  ***Like all epoxy products, whether in powder or liquid form, they do have a finite shelf life, and I keep them in a small refrigerator in the hope of extending their life as long as possible because I don't know that I'll be able to replace them when they're either gone or no longer work. ***If anyone is reading this and has a source, let me know. Epoxy and other (usually polyester) powder coatings are widely used now, so it's possible another source is out there. These powder coatings used for armatures are a high temperature epoxy type and are used in industry for coating rotors, stators and other electrical/motor components for insulating them. More commonly available powder coatings can be had from places like this one:

http://www.columbiacoatings.com/
 
Columbia makes some really neat powders, and one of theirs is widely used in the firearms industry.  Many of them should be fine for armatures even though they weren't developed for them because you're just looking for a tough, heat resistant coating that doesn't conduct electricity.  The only problem here is that these powders were developed for electrostatic spray application.  The electrostatic method requires extra measures in preparation of the armature as well as a way to capture extra powder that doesn't bond to the armature ("overspray") such as a type of mini-"booth" or some such thing.  Electrostatic powder coating is capable of a thinner and very even finished product coating, but is more cumbersome for the reasons above and others, and requires a special gun for application.  The guns that Columbia sells are very expensive and really meant for industry.  Eastwood, sells inexpensive ($60) electrostatic guns that should work fine with Columbia's powders.  I had one that I experimented with, but ultimately went with a different method of application.  By the way, Eastwood sells powders as well and in a dizzying array of colors and finishes, but they're polyester powders and not as tough or heat resistant as the epoxy stuff:
http://www.eastwood....-coat-guns.html

I use a method of powder coating called "fluid be" application.  If you use powders formulated for electrostatic application in a fluid bed, you'll get a very thick and heavy coating, at least with the powders I've tried, and this is not very suitable for armatures where you don't want to waste space or add useless extra mass.  Fluid Bed application is really about preheating the part (*armature stack in our case) to around 375-400F (a cheap toaster oven works well), and then dipping the part into the powder which is contained in a "bed" with air (supplied by a cheap aquarium pump) rising up from the bottom through a membrane into the powder.  Under these conditions, the powder looks like and behaves like a boiling liquid.  Because of the "boiling" type movement of the powder, as well as preheating the part, the powder will get into the "nooks and crannies" and then stick instantly to the part.  To make sure the part is well-coated on the insides, you give it a couple of "twists" or "spins" as you're dipping it.  After dipping, the part goes back into the oven for "post curing"... fifteen or twenty minutes is plenty, as the arm will be subjected to more heat when curing the epoxy and even just running if the arm is "warm" wind ;)  With any method of powder coating, places you don't want the powder to stick to MUST be masked because, once coated, the powder is pretty darned difficult to remove.  For masking that won't be ruined by the oven temperatures, teflon products in either tubing or tape work really well.  I use this stuff from Eastwood in the 3/4" width and one roll will last you for years:

http://www.eastwood....sking-tape.html

Looking around YouTube, I found several videos on fluid bed powder coating (anglers use the same method for applying tough, brightly colored coatings to fishing lures).  This one even has the same air pump I use, but even smaller ones can work well.  Whatever material you use for a "membrane" to separate the air coming into the fluid bed from the powder has a big effect on how well your fluid be will work.  Generally speaking though, you really only need to see the powder "lift" up like a half inch or more and behave like a boiling liquid without so much air that the stuff starts getting all over the place and/or the powder coating isn't solid enough to provide good insulation against shorts.  Building your own fluid bed is super EZ:

https://www.youtube....h?v=QRL-HuoSSRo

So, getting the right kind of powder can be tough, but some of the Columbia material should be fine...although it is meant for electrostatic application.  Maybe you can get it to work well with some experimenting, and their coatings in general should be fine for less extreme winds.  They do have ceramic type coatings, but application and even more so, curing becomes an issue.  Powder coating is a whole area to investigate on it's own, but you CAN do it with some basic "scratchbuilding" type ingenuity.  It isn't rocket science.

For the epoxy used to "pot" the armatures after winding.  You want a lo-viscosity material that will penetrate the armature coils that will also have high heat tolerance.  ***The commonly used magnet wire for armatures has no more than a 200-220C tolerant coating (around 400F), so anything beyond that with the epoxy is probably overkill in most cases.  ***If an armature gets to 400F, other things are likely to be going wrong with the rest of the motor.  That's not to say that even more heat-resistant epoxy wouldn't be a good thing, just probably not necessary in most cases.  After being lo-viscosity and high heat-resistant, other properties you want in an epoxy is a relatively easy cure schedule and of course a fairly clear finished appearance.  The epoxy I use is called "Duralco 4461" and is made by a company called "Cotronics".  It's available in a one pint "sample kit" that has both the resin and the catalyst ("hardener").  If you keep the stuff cool, it can last you MUCH longer than the 6 month shelf life spec...much much longer.  That's a good thing because even the "sample kit" is about $100.  You might be able to ease that pain by finding someone to split the kit with.  Then you could get some cheap plastic bottles, separate the material in half, pack it very carefully (the P.O. and other shippers have rules you need to follow) and send it off.  Anyway, here's the link to Cotronics' "Duralco 4461":

http://www.cotronics...tr/pdf/4461.pdf
 
You can also look at their "4460".  This has even better heat-resistance (up to 600F under service), but requires more in the way of heat for curing.  Either one will "speed-cure" and at least gel enough to not run all over the place under heat, but you DO have to be careful not to over-apply and watch the armature while it's starting to gel because getting it off after curing is impossible.

http://www.cotronics...tr/pdf/4460.pdf
 
No regular "hardware store" type epoxy will work well.  Even JB Weld, which has a good enough heat tolerance for many arms, is waaaaaay too thick to penetrate the coils and is of course not clear (their best formula anyway).

***That's all I have on the subject.  I've posted all this at least several times before, so I hope someone will bookmark this so I don't have to post it again!

-john


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#4 havlicek

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Posted 23 October 2016 - 07:42 AM

Back on this little "Strapnut™", I thought better about the paint on this motor, since it very well will be soldered-in... so I stripped the paint and left it as bare metal.

IMG_1783_zpsjyx9bnzv.jpg

 

For "motivation", I wound me up a 45t/28. On the short stack, the arm comes in at .198 ohms. LOTS of revs is the aim here!

IMG_1782_zpscxccppcs.jpg

 

-john


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#5 olescratch

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Posted 23 October 2016 - 08:20 AM

John,

 

I appreciate the info you have provided for the items you use to produce your motors, and really hope that I didn't cause you too much grief. I was just seeking to have all possible info in one post to make a copy of. I for one, will never ask for this info again! 


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#6 havlicek

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Posted 23 October 2016 - 08:51 AM

Hi John..

 

Please... no worries! Part of all this is just in the "form" of the internet. I've posted so much stuff over the years, there were two threads that became so long, they were unmanageable and even unsearchable. I don't know what to do about that, but my aim has always been to post as much info as I can, because a lot of that info wasn't there for me either as a kid or more recently as I got back into all this again. There's less "secrecy" now than in the '60s, but a lot of the information is still kept under wraps.  

 

There's a lot I still don't know, but I'm happy to tear off the blankets wherever I can anyway!

 

-john


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#7 Mark Johnson

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Posted 23 October 2016 - 06:19 PM

Where did you set the timing?

 

Mark



#8 havlicek

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Posted 23 October 2016 - 07:24 PM

Almost always around 15 degrees advance CCW, Mark.

 

-john


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#9 havlicek

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Posted 29 November 2016 - 08:24 AM

I got this arm back in the last batch that was sent out for balancing.  This little guy whistles like the theme song from the "Andy Griffith Show".  Sometimes I do these with ceramics, sometimes with the "poly neos".  The ones with the neos tend to have more grunt and the ceramic versions more RPMs.  This one follows that, but there are certainly plenty of revs on hand!  While a #28 may not sound like "much" to some, it's an excellent combination of speed and reliability all tucked-away in a very compact little motor.  That's why it's a wind I favor for these things.  Another tossed FK has a second chance at life :)

 

-john


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#10 havlicek

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Posted 30 November 2016 - 05:10 PM

OOPS!  Forgot the glamor shot!

IMG_1851_zpsdepasgtu.jpg


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#11 Jay Guard

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Posted 30 November 2016 - 08:52 PM

Artwork, simply artwork !!


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Jay Guard
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#12 havlicek

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Posted 30 November 2016 - 09:01 PM

Thanks Jay!

 

-john


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