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Apr 11, 2021, 12:01 AM
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Help!

I mucked up an outrunner ...


... brushless motor, stupid me what happened was l drilled the radial mount, with the idea of tapping the mount to recieve the bolts l wanted to secure it to the firewall of my plane & of course the drill bit hit the windings! Of course l rplaced the unit, but now l have a brand nd new motor that is trashed! Look, its not the money, lm just a natural born tinkerer! & l want to re/wind this motor Anyone got ideas? Maybe a link to something? Thank you, Laramie.
Last edited by Lmoreau13; Apr 11, 2021 at 10:56 AM. Reason: I was told to ...
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Apr 11, 2021, 03:25 AM
jofro
Buy the new motor, they cost peanuts these days. You mentioned it's not the money!
Apr 11, 2021, 07:46 AM
homo ludens modellisticus
Ron van Sommeren's Avatar
Do you want to change the velocity konstant Kv? Or do you want to keep it the same?
Note that Kv, expressed/measured in rpm/volt, says nothing about how much power a motor can handle. And max. torque does not depend on Kv, it will not change due to a rewind.


Don't remove the windings yet, we/you need a bit of information first.
  • Make/type motor? Link?
  • What is the original Kv_old of that motor?
  • Desired Kv_new?
  • Are the three phases terminated in delta or wye? See my next post below.
  • Maybe it's not necessary to rewind the motor, just changing it from wye to delta termination will multiply Kv by √3.
    Conversely, going from delta to wye will divide Kv by same factor √3.
  • What is the number of magnetpoles?
  • Number of statorteeth?
  • Number of coils?
  • Pictures?

Once you know all that, you can remove the windings.
  • Don't damage the stator insulation.
  • How many parallel wires?
  • (Single)wire thickness?
  • How many winds in a coil? Parallel wires count as single one wire when determining number of winds.

New number of winds for desired Kv_new is easy to calculate. For a given motor Kv is inversely proportional to #winds:
#winds × Kv is constant
Therefore:
#winds_new = #winds_old × Kv_old / Kv_new
It follows that as #winds goes up, Kv goes down, and vice versa.


Vriendelijke groeten 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 11, 2021 at 08:07 AM.
Apr 11, 2021, 07:54 AM
homo ludens modellisticus
Ron van Sommeren's Avatar
1. Principle: one coil per phase.
Motors can have several coils per phase.
Each of the three phases has a start and an end. Don't reverse them, when terminating/configuring the phases in star or delta.
Star = wye = Y, delta = triangle = Δ




2. Three coils per phase





3. Three coils per phase, 9N/12P cd-rom winding diagram

Last edited by Ron van Sommeren; Apr 12, 2021 at 10:57 AM.
Apr 11, 2021, 11:12 AM
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Thread OP
Quote:
Originally Posted by jofro
Buy the new motor, they cost peanuts these days. You mentioned it's not the money!
Oh! Im ahead of you, I did that right after the motor got damaged But didnt l mention that l like to tinnker with stuff? Back in the day, when off/road R/C racing was all the rage, l built hand wound race motors, but those were only 2 magnet, 3pole brushed motors. there are those amoung us who just want to play {the majority, it seems) & than theres people like me, who enjoy the building & tinnkering aspect of the hobby I will enjoy re winding my little & admittedly in expenceve motor, & learn about brushless tecknology into the bargain! Laramie
Apr 11, 2021, 11:28 AM
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Thread OP

T.o Ron van Sommeren ...


... Thank you, thank you, THANK YOU!!! See, Im already learning stuff! I hope you are a paitient man, as soon as I tear the little motor apart, I will be able to answer those questions like pole count, magnet count etc. . If I remember correctly, Its 2100 KV ... Anyway, thanks again for the diagrams & the easy to understand explanation of the funtioning of a 3 phase motor ... Laramie.
Apr 11, 2021, 11:40 AM
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Thread OP

After re reading your first ...


... post, it brings back fond memories of my motor modifying days, less turns, higher RPMs, more turns lower speed, but higher torque, as l can see, it seems the same principles apply. Laramie
Last edited by Lmoreau13; Apr 11, 2021 at 11:40 AM. Reason: Typo
Apr 12, 2021, 09:14 AM
homo ludens modellisticus
Ron van Sommeren's Avatar
Quote:
Originally Posted by Lmoreau13
as l can see, it seems the same principles apply. Laramie
Yes, same principles.
There's not much of a difference between a brushed and a brushless motor. The former has a mechanical commutator, the latter has an elektronic commutator, the ESC.
Both have the same motormodel, with parameters Io , no load current, Rm, resistance and Kv, the velocity konstant.
As far as the rotor of a brushed motor is concerned, it is a three-phase system as well.

By rewinding with different number of winds you can change Kv and Kt. As one goes up the other goes down, and vice versa.
By using thicker wire, cramming more copper in the slots, efficiency will increase, the motor will be able to handle more power and/or get less hot:
Efficiency governs maximum power a motor can handle - RCG


Quote:
Originally Posted by Lmoreau13
... l built hand wound race motors, but those were only 2 magnet, 3pole brushed motors. ...
Brushless motors in RC have an even number of magnetpoles, number of statorpoles is multiple of three, number of coils is multiple of three.



LRK winding diagram, only half the teeth wound.




Quote:
Originally Posted by Lmoreau13
... less turns, higher RPMs, more turns lower speed, but higher torque, ...
Not quite, max.torque does not change with #winds.
However, Kt, torque for given current is proportional to #winds.
Kv, speed for given voltage, is inversely proportional to #winds.
angular speed = voltage × Kv
torque = current × Kt
with
Kt = 1/Kv
Kv and Kt in SI units, radians per second per volt respectively newtonmeter per ampère.
Multiply left-hand terms and you get mechanical power, right-hand terms give electrical power.



Three phase.
The three motor/ESC wires are equivalent, but not identical. They carry the same motorvoltage signal albeit with a 120degree phase ('time') difference, switching between zero and full voltage. One complete voltage cycle corresponds with one magnet passing a stator pole.

See also these
brushless motor animations and simulations - RCG

You can connect the three motorwires anyway you want. If motor runs in the wrong direction, just swap any two of the three motorwires. But NEVER EVER swap battery wires to reverse rotation, reversing battery polarity will ruin you controller, bigly, in the blink of an eye
Different colours for motorwires are handy for remembering the ESC→ motor connections, that's all


Motorvoltages at full throttle, no chopping up voltage in pieces.



Motorvoltages at partial throttle, PWM chopping ('grass') to reduce effective voltage.


Scope traces from www.aerodesign.de/peter, DIY brushless motor building (english&german)
Last edited by Ron van Sommeren; Apr 12, 2021 at 11:05 AM.
Apr 13, 2021, 04:51 PM
Registered User
Thread OP

What we have ...


... here is 12 poles (hope this is the correct term),&14 magnets. the lable on the can sez, L2210, next line (below the first) sez 1400KV 210W. I have removed the 2 set screws & pulled the radial mount off the back end of the motor, & a tiny little snap ring & washer, also the other 2 set screws from the bell. what is the best way to press the bell off the shaft?

Is it hammer time? Theres a bench vice around here somewhere.

Thank you for all the help, advice, & above all your patience It is very much appriciated!

Laramie.
Apr 13, 2021, 05:01 PM
Registered User
Thread OP

P.s.


I dont want to modify the motor, just replace the wires that I broke with the drill bit. Maybe down the road a bit, when I have a better understanding of all this, l might try my hand at modifications, right now, Ill be satisfied with just rewinding the motor.
Apr 13, 2021, 05:09 PM
homo ludens modellisticus
Ron van Sommeren's Avatar
You don't have to remove/press the bell from the shaft, you remove the assembly as a whole.

In the opening post, under #6, you'll find methods for motor disassembly and for removing the coils
Re-winding and building motors, tips and tricks, checks and tests - RCG
The topic numbering takes you through a typical motor rewind, from beginning to end.

All 12teeth/statorpoles wound, distributed LRK windingdiagram,, or 6 of them, LRK windingdiagram? (there's a very simple relation between the two to get the 'same' motor)
See
www.bavaria-direct.co.za → winding schemes → common schemes (RCG user skylar)
old.torcman.de/motoren/manuals/anl_eco_200e_scr.pdf → 2.2. preparation for winding


Vriendelijke groeten 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
Apr 13, 2021, 06:12 PM
Registered User
Thread OP

I am learning!


Well, its just as you said. The magnets in the can are really strong! Now I have The stator assembly out, the ball bearings, a little washer/ spacer, you know, all that stuff that is oh so easy to loose, locked up in an old plactic medicine, vial, so if any of it gets lost, itll all get lost together Now I think its time to study some more of your (& others) links & before anything else, I need to go to to Macs Electronics (the go to place in San Bernardino) for a spool of wire , Im beggining to think I just might pull this off yet Danka (?), Ron! Laramie.
Apr 13, 2021, 09:20 PM
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AntiArf's Avatar
Learned about accidental winding nicking years ago, with long screws hitting the windings. They still supply motors with excessively long screws, including an outrunner I'm using in my current build right now! Took an inrunner with a failed winding due to being nicked, cleaned up the wire ends and bridged them. I've tested the motor up to rated current without issue.

Had a GWS inrunner fail in an EDF, due to the factory nicking windings while installing the endbell. It was beyond trying to repair using the method shown below, with the windings trashed! I'm surprised it ever ran. There's a few videos of guys throttling up their GWS 262s, then blowing smoke from the nacelles. Picturing them assembling the motor endbells at the factory, reminded me of the old tv commercial with the monkey trying to pound the square block in the round hole. Apparently they windings were loosely wound on the mandrel, so the solution was to just pound the endbells on and make it all fit in there.
Last edited by AntiArf; Apr 13, 2021 at 09:25 PM.
Apr 13, 2021, 10:29 PM
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Thread OP

Well, its apart ...


..... I see what you mean, the shaft stays with the bell, the stator came out, & is with out the bearings.in my old brushed motors, l used to epoxy the windings, is it an advantage to epoxy the stator windings on this little out runner? Or is it a waist of time? Its a very cheap little Turnegy motor. & l still dont have the wire to wind it with. Whats worse, I dont know what I will find available tomarrow when l go shopping & if it is an advantage to epoxy the winds, would 30 minute be good? Laramie.


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