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Old Nov 17, 2013, 08:19 AM
Jack
USA, ME, Ellsworth
Joined May 2008
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Automobile alternators are wound with heavier wire, it can often be seen through the cooling openings. Not sure how likely it is that they would lend themselves to the wire being reused for winding though.

If you happen to know of a shop that re-winds or rebuilds motors and generators they may have some scrap wire or too short for their use remnants they will give you.

If you measure the length of a stator arm from near the bottom of the "V" formed by the slot between two arms and out to the end where the shoulder of the hammerhead is, you can estimate the wire size that will give you the desired turns by using the wire dimensions from the wiki AWG page. That way when you buy a spool of good wire you will have a good chance if it being the best size for the wind.

But always remember that it is a little better to start with wire on the too small size than with wire that is too large to fit all the turns with.

As an example, if there is a windable length of 20mm on each arm and you want to get 20 turns on the arm, in two layers of 10 turns on each as it would typically be done, then 10 turns of wire that is 2mm in diameter would fill the first layer on the arm with turns.

But we also know that on the smaller stators on these motors the wire size can become too large to do the winding with. And 2mm wire is almost impossible to work with, it is too stiff. It becomes very difficult to keep the larger wire in contact with the stator arms and make the turns on the corners of the arms. So that will mean that you'll have to use two smaller strands (like 1mm in dia. for example) in parallel and lay the pair of strands side by side for 10 turns.

When the second layer goes on, the primary complication will be that that two adjacent arms will put four layers of windings close to each other as the "V" shaped slot narrows as the bottom. And that can limit the size of the wire you can use. Sometimes that jam at the bottom can be resolved by going to smaller wire, putting 12 turns on the first layer, and only 8 turns in the second layer so as to get the needed 20 turns while, at the same time, relieving the crowding between two adjacent arms at the bottom of the slot.

The point of it all is to fill the arm with the maximum possible amount of copper while, at the same time, choosing the wind type and termination that gives you the number of turns that produces the desired Kv.

If you look at the image of the Turn Calculator spreadsheet for the DAT-750 motor you can see a very useful tool. I entered the turns and termination from the factory wind in the yellow boxes and it shows me the options for getting various Kv ratings using other winds and terminations. The winds shown there are the LRK wind, the Half Parallel dLRK wind, and the dLRK wind. And the results for using either a Delta or Wye termination are shown. The results there are unique to that particular set of components (magnets and stator) so you have to base the re-wind KV predictions on the Kv that resulted from the original wind.

If I wanted to re-wind a DAT-750 motor to have a 800 Kv, there are several winds that could do that. Look for the values close to 800 and that is a candidate wind. But to get the highest current capacity and most power, I would normally want to use the largest possible size of wire (to lower the resistance and increase the current capacity). And that would mean that I would be most interested in the winds that could be accomplished with the lower numbers of turns.

That is a motor that has been much rewound, all the winds have been tried, and it is now well known that the Half Parallel dLRK wind, terminated Wye, done with about 18 to 21 turns will produce a very good motor with a Kv in the 750 to 900 or so range. And it is also known that wire in the range of 22 AWG to 19 AWG can be used. The 19 AWG or 20 AWG is arguably the largest wire that is practical to use and it will take some skill to get the turns on with those sizes. For a new motor re-winder, I would recommend starting with the smaller 22 or 21 AWG wire for the first re-wind and then, as your skills develop, consider moving up to larger wire when and where you can.

Is it worth the time and trouble? I think so. The re-winding on the DAT-750 took a motor rated for 135W on 3S and got it up to the point where it could be used at up to 400W and on 4S. And if you simply matched the original factory wind, doing it with a neatly done single strand wind, you would have a much smoother running, more powerful, and very reliable motor capable of 200W continuous operation.

Jack
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Old Nov 18, 2013, 03:48 PM
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Quote:
Originally Posted by sredlin View Post
Andre, I'll keep that in mind, I may not have anything that heavy duty on hand, but I have a good ideas what to look for now, thanks for the tip.
For the 2812 specifically I would recommend a high temperature rated wire (200c).
Every one I have done with radio shack wire has burned out.
The sweet spot for this motor seems to be 9 turns of 23 or 24 guage MicroDan wire. It looks like Tech Fixx also has some 200c rated wire. I may have to give it a shot once I've used my spool of the MicroDan stuff. Got five motors fixed so far just from the one spool I purchased...
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Old Nov 18, 2013, 05:56 PM
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I found this place in southern California selling 200c wire as well, the price after shipping works out to be nearly the same as gobrushless.com's MicroDan wire, but it may ship to me a little quicker, so I may try it? Here's the link:

http://www.powerwerx.com/wire-cable/...FWRk7AodWlAALQ
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Old Nov 18, 2013, 06:20 PM
Jack
USA, ME, Ellsworth
Joined May 2008
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That wire will work fine. Reading the specs for it there, the descriptions of the coating and the like are identical to those as used by http://www.techfixx.com/ so it might be from the same maker.

If you click on a wire size in the Tech Fixx listings and then read the description in the eBay listings, he has more detailed specifications there and the maker and type too. As far as I can tell, all Tech Fixx wire is U.S. made Essex (aka Superior-Essex) wire.

I have used all three colors, red, amber, and green, and found them all to work well. I use 130F/54C or too hot to keep a finger on it for my normal "that is as hot as I want a motor to get" limit so I think the 155C stuff is adequate.

I would not be surprised to find that MicroDan, Powerwerx, and Tech Fixx are all selling the same wire.

Tech Fixx will give you a combined shipping cost if you ask for it (or maybe even automatically) and you can get two 1/4 lb. spools shipped for the cost of shipping one spool.

Jack
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Old Nov 18, 2013, 10:04 PM
My dog ate my airplane
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Jack,

Thanks for the link, that's the most reasonably priced wire I've seen so far, which makes it easier to justify rewinding a cheap "disposable" motor instead of just buying a new one. I guess it's really more about doing it just to say you can anyway, right?

Scott
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Old Nov 18, 2013, 11:06 PM
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I have wound quite a few motors with beading wire. No specs of course, but I never had a short using it. It is actually more flexible than some winding wire, yet the coating is tough to scrape off. Very good wire, and cheap too.http://shop.hobbylobby.com/products/...g-wire-833038/
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Old Nov 18, 2013, 11:07 PM
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about six bucks gets you a new a brand new little red motor. But, a little patience and learning how to get it done and you can end up with a nice setup. I know people that will actualy buy these things new, strip the wires and do the rewind. There are still some quality issues with the little red motors and rewinding isn't for everybody, but it is fun to take something broken, make it work again and in the case with the 2812 actually work better and more reliably than it did before.
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Old Nov 19, 2013, 08:03 AM
Jack
USA, ME, Ellsworth
Joined May 2008
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Quote:
Originally Posted by sredlin View Post
Jack,

Thanks for the link, that's the most reasonably priced wire I've seen so far, which makes it easier to justify rewinding a cheap "disposable" motor instead of just buying a new one. I guess it's really more about doing it just to say you can anyway, right?

Scott
You just have to get your mind into that peaceful state that us "man knitters" attain when we watch a re-wound motor start up smoothly and run quietly. You'll always remember that first one that did that.

It took me a couple of fumbling around tries to get my first re-wind going but there was no looking back from there. It did not have to make sense economically as far as comparing the costs of buying new to re-winding.

There are many aspects of the hobby where putting time and money into something is done only for the joys of doing it and maybe taking a small benefit from it too.

I use the attached image as an example often, it speaks to me as to why I like to rewind motors.

Jack
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Old Nov 19, 2013, 10:01 PM
My dog ate my airplane
United States, CA, San Diego
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Jack,

That wind certainly looks much neater, does it help the electrons flow in a more organized pattern as well? Seriously though, I understand that this isn't necessarily economically motivated, and I think your pictures above really demonstrate how a cheap motor can be upgraded to a higher quality motor which is maybe as good or better than the expensive brand name motors out there.

Hopefully I can successfully pull this "man knitting" trick off on my broken 2812 when I get the wire I just ordered from techfixx.com?

So is the motor in your picture above similar to the 24 gram Blue Wonder, because I have a few of those and may consider a rewind on one of those if I am successful with my 2812 wind?
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Old Nov 19, 2013, 11:45 PM
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It does look similar to a blue wonder I would say.
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Old Nov 20, 2013, 07:54 AM
Jack
USA, ME, Ellsworth
Joined May 2008
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Quote:
Originally Posted by sredlin View Post
Jack,

That wind certainly looks much neater, does it help the electrons flow in a more organized pattern as well? Seriously though, I understand that this isn't necessarily economically motivated, and I think your pictures above really demonstrate how a cheap motor can be upgraded to a higher quality motor which is maybe as good or better than the expensive brand name motors out there.

Hopefully I can successfully pull this "man knitting" trick off on my broken 2812 when I get the wire I just ordered from techfixx.com?

So is the motor in your picture above similar to the 24 gram Blue Wonder, because I have a few of those and may consider a rewind on one of those if I am successful with my 2812 wind?
One of the things we gain with our single strand winds is that the turns are more concentric and evenly spaced. And, although it cannot be seen or measured, we are assured that it also results in a increase in the quality and performance of the magnetic fields. I like to say that our rewinds have better "magnetic karma".

That was a 78g motor with a 40mm O.D. on the magnet housing, about three times as heavy as a BW. When it first arrived it's size was unusual, it was like the biggest ever blue wonder and it's size alone gave it a strong allure. It promised more power.

And it was also a 12N14P (12 slots, 14 poles) motor whereas some of the 24g motors were 9N12P motors. The 12N14P motor opened to door for some winds that could not be done on the 9N12P. And the bigger, more roomy, and easier to work on and with stator was also welcomed by guys with normal sized hands and fingers.

The DAT-750 had it's issues (small bearings for example) but it also had enough potential that the man knitters could live with the drawbacks.

If your 2812 is a 12N14P motor it can have all the same winds that were used on the DAT-750. It will mean smaller wire, other issues will arise (like clearance for the windings and the magnet housing dome), but you can do it.

Jack
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