Apr 05, 2021, 11:34 PM
Go ahead... Build it to crash!
Discussion

# what happens if I miss a turn?

Hello all,
I was just curious of the impact of missing a turn when winding a motor. Let's say for example on an ABC 12stator 16 magnet pole 2730 motor I have wound 11 out of twelve stator poles to 15 turns, but the remaining pole only got 14 turns. How much will that impact the performance of the motor? Assuming of course there are no shorts and everything else is wound correctly. Thanks.
 Apr 05, 2021, 11:53 PM If it flies, I can crash it. There's probably a much more complicated mathematical derivation, But using "back of the napkin" math, Magnet strength is proportional to the number of windings. So that winding is 93% as strong as the other 2. But there are three windings in the motor, of which two are at 100%. So on average, I think the motor will be (100+100+93)/3 = 97 percent as strong as if you'd wound it correctly. You have effectively raised the KV slightly, but that comes at the cost of lower torque. If it was me, I'd fly it this way and not go to the bother of rewinding unless the purpose of rewinding was to maximize performance.
Apr 05, 2021, 11:57 PM
Go ahead... Build it to crash!
Quote:
 Originally Posted by rocketsled666 There's probably a much more complicated mathematical derivation, But using "back of the napkin" math, Magnet strength is proportional to the number of windings. So that winding is 93% as strong as the other 2. But there are three windings in the motor, of which two are at 100%. So on average, I think the motor will be (100+100+93)/3 = 97 percent as strong as if you'd wound it correctly. You have effectively raised the KV slightly, but that comes at the cost of lower torque. If it was me, I'd fly it this way and not go to the bother of rewinding unless the purpose of rewinding was to maximize performance.
Awesome. Thank you. I'm not even sure if I missed a turn, but I have a nagging feeling that I might have. I just didn't want to possibly cause damage to the ESC or anything like that. I'll run it up on the wattmeter in the morning and see how it goes.
 Apr 06, 2021, 01:00 AM Registered User You only missed a turn on one tooth? There are 4 teeth per phase, so using a new napkin, torque will be down by (1 - (14 / 15)) / 4 / 3 = 0.56%. Thus the motor would theoretically still have 99.44% torque and Kv would be 0.56% higher, e.g. 1006 RPM/V instead of 1000. I've seen bigger mistakes on motors that were wound in factories.
 Apr 06, 2021, 01:24 AM If it flies, I can crash it. I expected someone would come along with a better answer.
 Apr 06, 2021, 02:13 AM Registered User Btw, I like the sound of 12N16P motors. They sound and feel so much smoother than the 12P14P models, plus the ABC winding is easier to do.
Apr 06, 2021, 09:48 AM
Go ahead... Build it to crash!
Quote:
 Originally Posted by Skylar You only missed a turn on one tooth? There are 4 teeth per phase, so using a new napkin, torque will be down by (1 - (14 / 15)) / 4 / 3 = 0.56%. Thus the motor would theoretically still have 99.44% torque and Kv would be 0.56% higher, e.g. 1006 RPM/V instead of 1000. I've seen bigger mistakes on motors that were wound in factories.
Excellent! I don't know that I missed a tooth. One tooth may have gotten perfect packing and just looks 1 turn light. I certainly did not want to unwind all that work to find out. My fingers are sore enough as is today. It just got me thinking about what would be the quantifiable effects of it. You have answered the question, and now I am not worried at all about it impacting performance.

I don't mind the 12/16 motors. The ABC wind is cake. I feel like the 12/14 are smoother because the cogging isn't there. If I'm winding a delta for high speed I like the dlrk pattern where the wires to be joined come out perfectly next to each other. Either way, I love these little Turnigy red and blue wonders 2730 motors. I just buy them without worrying about the kv and then rewind them to suit whatever style of plane I'm building. I've never been disappointed with the result. The factory winding is weak, but is easy to remove, which is a plus for my purposes. This motor came with 11 turns of 26g. I rewound with 15 turns of 25g. The stator is much more full of copper.
 Apr 07, 2021, 09:51 PM Sokol one aspect that was not mentioned is the introduction of torque ripple and vibration because of the field strength difference. In the end , not worth bothering , I would say. Latest blog entry: Great Planes Rifle based franken-plane
Apr 09, 2021, 11:36 AM
homo ludens modellisticus
Quote:
 Originally Posted by Fuegodeth ... I have wound 11 out of twelve stator poles to 15 turns, but the remaining pole only got 14 turns. ...
The sum of the three (phase)voltages won't be zero.

As others already wrote, you probably will not notice it ... in star.

But a delta termination is a closed circuit, what you have now is a shorted non-zero sum of the three voltages. Current will recirculate, resulting in losses and higher temperature.

Quote:
 Originally Posted by Fuegodeth Excellent! I don't know that I missed a tooth. ...
You could do the generatortest and compare the three voltage if you want a piece of mind.

Or short the three motorwires and drive the motor with powerdrill. If you hear a chugging sound there could be a miscount.

Next time you could start with, or mark, same lengths of wire before rewinding. If you have wire left over, or markings in the wrong place, you probably miscounted .

Prettig weekend en wees voorzichtig, Ron
• Without a watt-meter you're in the dark ... until something starts to glow •
E-flight calculatorswatt-metersdiy motor tips&tricksCumulus MFC
Last edited by Ron van Sommeren; Apr 25, 2021 at 04:08 PM.
Apr 09, 2021, 06:43 PM
Go ahead... Build it to crash!
Thanks Ron,
It's a star termination. Thanks for the other info, particularly the bit about delta termination.

Quote:
 Originally Posted by Ron van Sommeren The sum of the three voltages won't be zero. As others already wrote, you probably will not notice it ... in star. But the delta termination is a closed circuit, what you have now is a shorted non-zero voltage. Current will recirculate, resulting in losses and higher temperature. You could do the generatortest and compare the three voltage if you want a piece of mind. Or short the three motorwires and drive the motor with powerdrill. If you hear a chugging sound there could be a miscount. Do you hear a difference between shorted and open motorwires? Next time you could start with, or mark, same lengths of wire before rewinding. If you have wire left over, or markings in the wrong place, you probably miscounted . Prettig weekend en wees voorzichtig, Ron • Without a watt-meter you're in the dark ... until something starts to glow • • E-flight calculators • watt-meters • diy motor tips&tricks • Cumulus MFC •
 Apr 21, 2021, 06:42 PM Ronaldo Nogueira Always had that question, thanks for asking I'm sure I've unwound motors with unequal number of turns/ tooth too (from factory). The result is always a mismatch with TC spreadsheet predictions, requiring a new rewind. Ronaldo
Apr 23, 2021, 01:15 PM
homo ludens modellisticus
Quote:
 Originally Posted by Fuegodeth what happens if I miss a turn?
Centraal Beheer insurances is based in Apeldoorn/Nederland.
"Even Apeldoorn bellen." = "Just call Apeldoorn."

Hedgehog.
Last edited by Ron van Sommeren; May 15, 2021 at 11:42 AM. Reason: Added translation: "Even Apeldoorn bellen."
Apr 23, 2021, 07:04 PM
homo ludens modellisticus
Quote:
 Originally Posted by Fuegodeth what happens if I miss a turn?
Picknick.
Last edited by Ron van Sommeren; May 15, 2021 at 11:44 AM.
 Apr 23, 2021, 07:29 PM homo ludens modellisticus Both were commercials for Centraal Beheer insurances, located in Apeldoorn/Nederland. Catchphrase: "Even Apeldoorn bellen." = "Just call Apeldoorn." Not all their, very funny, commercials where about missing a turn: Youtube Centraal Beheer commercials. Vriendelijke groeten en wees voorzichtig, Ron • Without a watt-meter you're in the dark ... until something starts to glow • • E-flight calculators • watt-meters • diy motor tips&tricks • Cumulus MFC • Last edited by Ron van Sommeren; Apr 26, 2021 at 07:43 PM.
 Apr 23, 2021, 10:05 PM Go ahead... Build it to crash! Thread OP I was wondering about that. Funny stuff. Thanks Ron.