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Mar 24, 2015, 01:45 PM
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basicguy's Avatar
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Discussion

rebuilding HexTronik 20g Brushless Outrunner 2300kv


had a motor go bad after the electronics got drug out of the bay an through the prop. It took out one wire from the motor.

I took it apart and found some abrasions on the front face of the windings.

It is a 2300kv 50w motor. The stator is .72" by .25" The wire is 30 AWG. 22 turns on each of the 9 poles with a 12 magnet rotor. Delta termination.
This is what it looks like with all the wires on it.


It is going to be my first re-wiring of a motor.

I was thinking of making the wiring in a larger gauge. 28 and going to a Wye termination.

Would it be better to keep the rewind stock?

I have practiced by turning some of the old wire back on to the armature.

Read through lot of posts on here, does everyone use a wand to keep the wiring straight and parallel or can it be done by hand.
Last edited by basicguy; Apr 03, 2015 at 06:59 PM.
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Mar 24, 2015, 03:44 PM
homo ludens modellisticus
Ron van Sommeren's Avatar
The thicker the winding wire, for given number of turns, the better for efficiency, power and temperature. Also better for constant rpm (helicopters).

Tips, tricks, checks, tests, videos, manuals in this RCG sticky same subforum, will save you time/money/controller/motor:
(Re)winding and building motors

Vriendelijke groeten Ron
Mar 24, 2015, 06:52 PM
Greediest Suer
Ron H's Avatar
Quote:
Originally Posted by basicguy

I have practiced by turning some of the old wire back on to the armature.
Best practice or test wind is to wind one, skip one and wind the next, then see if you can wind the one between.
Mar 24, 2015, 07:48 PM
Laughs at un-boxing videos...
basicguy's Avatar
Thread OP
Thanks Ron I'll try that.
Mar 25, 2015, 05:54 AM
homo ludens modellisticus
Ron van Sommeren's Avatar
Quote:
Originally Posted by basicguy
... 9 poles with a 12 magnet rotor. ...
ABCx3 (= CD-ROM) winding diagram
www.bavaria-direct.co.za/scheme/calculator

Quote:
Originally Posted by basicguy
... and going to a Wye termination. ...
Going from delta to wye will lower the Kv motor constant by factor √3.
Kt (= 1/Kv = torque per ampère), will increase by same factor.

Quote:
Originally Posted by Ron van Sommeren
The thicker the winding wire, for given number of turns, the better for efficiency ...
Efficiency governs power/weight ratio
Higher efficiency does not only mean that the motor makes better use of the batteries' power, it also means the motor is able to handle a higher power input before hitting its maximum temperature mark, i.e. a the power/weight ratio will be higher.

An example
Say the motor has an efficiency of 70% and it can handle 50watt input. That means it can get rid off 30% × 50 = 15watt excess heat. Now, by cramming in thicker wire (and/or using better stator-iron, segmented magnets), efficiency increases to say 75%. The motor's ability to loose those 15watt has not changed (by radiation, convection and conduction). This means the motor now can handle 60watt before it hits the 15watt (25% × 60watt) losses mark. An efficiency increase of 5% gives an increase in the power to weight ratio of 20% (from 50watt to 60watt). That's why efficiency plays such an important role, in any motor design: efficiency governs maximum power. The motors weight may have increased a bit due to more copper.
A rather extreme example, just for calculation's sake/fun: going from 80% to 90% efficiency would increase the input power the motor can handle by a factor two (a.k.a. 2).

Copper as thick as possible for
  • lower rpm drop under load
  • lower losses
  • lower temperature
  • highest efficiency
  • more power
  • at the cost of less good cooling
Vriendelijke groeten Ron
Last edited by Ron van Sommeren; Mar 25, 2015 at 06:40 AM.
Mar 29, 2015, 08:11 AM
Jack
jackerbes's Avatar
Quote:
Originally Posted by basicguy
had a motor go bad after the electronics got drug out of the bay an through the prop. It took out one wire from the motor.

I took it apart and found some abrasions on the front face of the windings.

It is a 2300kv 50w motor. The stator is .72" by .25" The wire is 30 AWG. 22 turns on each of the 9 poles with a 12 magnet rotor. Delta termination.

It is going to be my first re-wiring of a motor.

I was thinking of making the wiring in a larger gauge. 28 and going to a Wye termination.

Would it be better to keep the rewind stock?

I have practiced by turning some of the old wire back on to the armature.

Read through lot of posts on here, does everyone use a wand to keep the wiring straight and parallel or can it be done by hand.
Is it wound with multiple strands in parallel? If so, you can use a single strand of an equivalent cross section surface area and get a better motor.

That is called a 9N12P motor and it will use only the ABCABCABC wind, you can see that winding by entering 9 and 12 and choosing D here:

http://www.bavaria-direct.co.za/scheme/calculator/

And here is a manual for a kit motor that describes the process well:

http://www.micronradiocontrol.co.uk/.../KH-278-v2.pdf

If you change to a Wye termination at the same turn count you will lower the Kv by a factor of 0.58 and that will let you use a bigger prop usually. But the all around best way to do it is to choose a prop and battery voltage and then choose Kv that will work best for that prop. And, at that point, the termination (Delta or Wye) that has the fewest turns will let you use the largest wire.

You can use the Turn Calculator 7 spreadsheet to see the turn count results for an ABC wound motor. I struck that out as I am not sure it is right. I think maybe it would be the Simple Turn calculator... But the image is an example for another motor, you'll have to do that entering your motor's turn count, termination, and Kv and it will give you the turn count predictions for your motor.

The images are the Simple turn calculator results for your motor - that gives the turn counts and Kv predictions for D and Y rewindson your motor...

Jack
Last edited by jackerbes; Mar 29, 2015 at 09:48 AM.
Mar 29, 2015, 11:16 AM
Laughs at un-boxing videos...
basicguy's Avatar
Thread OP
Is this correct? Mine has 22 turns of 30AWG wire in a delta config giving 2300k/v. If I use 13 turns and go to a wye design I can keep the same k/v and use a thicker wire.

Originally it uses 18" of 30awg wire which occupies a volume of about .0018sq in. and is 22 turns. If I use 29awg wire and go for the same volume I would get 14" of wire and 17 turns. At 28 awg wire I would get 11" of wire and about 13 turns.

Going to a wye I would want about 13 turns to keep the same K/v therefore I would want to switch to use 28awg.
Mar 29, 2015, 11:24 AM
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basicguy's Avatar
Thread OP
One thing that I have noticed is that it is very hard to get the used wire back on the stator in the same density. Perhaps it is because the wire isn't as smooth and takes up more volume.

Oh thanks for the links.
Mar 29, 2015, 01:07 PM
Jack
jackerbes's Avatar
Quote:
Originally Posted by basicguy
Is this correct? Mine has 22 turns of 30AWG wire in a delta config giving 2300k/v. If I use 13 turns and go to a wye design I can keep the same k/v and use a thicker wire.

Originally it uses 18" of 30awg wire which occupies a volume of about .0018sq in. and is 22 turns. If I use 29awg wire and go for the same volume I would get 14" of wire and 17 turns. At 28 awg wire I would get 11" of wire and about 13 turns.

Going to a wye I would want about 13 turns to keep the same K/v therefore I would want to switch to use 28awg.
It is correct, that is the nature of the differences in Delta and Wye. You can see more info about that on the info page here:

http://www.bavaria-direct.co.za/info/

It unusual for a motor to be wound with a single strand of 30 AWG, it would usually be 2 or 3 stands or more in parallel. If each of your motor connector leads (at the bullets) had more than two strands in them, that is two wire ends or the ends of two bundles of parallel stands. So it there was four strands there it was two strand wind, six would be a 3 strand wind, etc.

I use this page to look of the wire sizes and surface area figures:

http://en.wikipedia.org/wiki/American_wire_gauge

If you had two strands of 30 AWG at 0.0509 mm2 you should be able use, at a minimum, one strand of 27 AWG at 0.102 mm2 and get the same number of turns. But of course, we always experiment with larger wire if the turns leave any room for it. It is part of the addiction of being a man knitter of motors.

I think maybe you can do better than 28 AWG at 13 turns. The primary problem you have is that of the turns on adjacent arms interfering with the winds on the next arm. And you'll get better at that eventually.

For me, using a 3rd hand and making money turns (threading strands through when space is scant) was the most help.
The images explain the money turn concept.

Jack
Mar 29, 2015, 02:53 PM
homo ludens modellisticus
Ron van Sommeren's Avatar
Don't forget to remove the sharp burr/edge from where you cut the windingwire. Burr could/will damage insulation.

Vriendelijke groeten Ron
Mar 29, 2015, 04:33 PM
Laughs at un-boxing videos...
basicguy's Avatar
Thread OP
Yes Jack it is a single strand of .01" wire. The motor is rated at 50watts at 7.4 volts and weighs 20 grams total.

Threading the wire is a great tip. Going over the top adds another twist. Good tip on not leaving a burr too.

I have 5 of these motors. One of my other motors damaged the wire where it came out of the windings. I resoldered the wire for now.

On one of the links they recommended unwinding 3 foot of wire rather than unspooling it as you go. Is that the way you do it?
Mar 29, 2015, 05:29 PM
Jack
jackerbes's Avatar
I pull the wire directly off of the spool and through the 3rd hand in most cases. That light tension on the wire and rolling the stator up the wire with a dowel handle through it really helps with getting the turns on and in contact with each other and snug to the arm. I use a CF prop tip or a small all plastic stylus and push the turns into contact on the first layer. The flat side of the CF tip will also work to press the turns back flat against the arm and make a little more room for the next arm's turns.

I guess a single strand of 30 or so will work on a motor that small. I have not done many of those. But I'll bet you'll see an improvement with the Wye term and bigger wire though.

Ron's tip about smoothing the cut off end of the wire for the money turn is a good one, I do that with a piece of 400 grit or so emery cloth. Just takes a second to get rid of those sharp corners from the ends.

Jack
Mar 29, 2015, 05:56 PM
Registered User
This Motor ?
https://www.hobbyking.com/hobbyking/s...er_2300kv.html

Search in this forum for 20 gram motor and /or Timocharis for historical answers to what you are considering.
Yes it's easiest to cut a length of wire then wind it.
Manuel V's chart can give a good approximation of the length to cut.
But certainly 36" will be more than enough per phase... if there isn't a critical wire shortage in your shop.
Do buy Decent quality wire Not much point in refitting wire of the same quality of the original Gobrushless. com ...Used to sell wire?
Certainly.... http://www.techfixx.com/ does.
Other thing to consider is that less than 10$ will replace the motor Wire costs will be more Plus you have to rewind it :-)
Yess It can (usually will) be a better performing motor..
However there is a learning curve and there will be a *few* hours work before you can enjoy the results.
Mar 29, 2015, 06:29 PM
Laughs at un-boxing videos...
basicguy's Avatar
Thread OP
Yes that is the motors I have. Had priced go-brushless last week and that was my conclusion as well. I have paid 7-9 dollars a piece for the motors brand new. They really make the foamies that I fly, run well.

I have not taken the rotors off any of the motors except the one that I am attempting to rebuild.
Mar 30, 2015, 06:59 AM
Jack
jackerbes's Avatar
We don't do this to save money, we do it to give a motor another life and have better motors. That is a lot of satisfaction to be taken from flying motors you have rewound.

One of the things that really helps is to get the motors apart without damaging the coating on the stator. And getting the stator off undamaged can be one of the most challenging points. This thread has the details on doing that:

Outrunner Disassembly and Stripping - Gimbal Motor Rewind - www.rcgroups.com/forums/showthread.php?t=1823636

Jack


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