Rewinding the famous RCTimer 5010 Pancake for lower KV - RC Groups
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Jul 30, 2015, 09:04 AM
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Rewinding the famous RCTimer 5010 Pancake for lower KV


Hi guys,

first things first: I'm not extremely proud of the results, however I still decided to share this. This might be the worst rewinding of a motor I have done so far (and I have disassembled and rewound approx. 50 motors) but there are some lessons to learn.

The base for this project is the RCTimer 5010 360kv pancake motor: http://rctimer.com/product-1080.html

I have attached some pictures for your convenience.

The motor has a kv of 360 and is wound with 4 parallel wires with 22 turns terminated star. I can't measure the original thickness of the 4 parallel strands as my digital caliper gauge is somewhere in my student apartment in mid-Germany (and I am on vacation).

The target was to lower the kv under 300 to make the motor fit 5S or 6S on 16 or 17" CF propellers (bearing in mind that the usual setup for this thing on a quadcopter is 4S and 17" CF).
I had to keep in mind that going up with the number of turns will dramatically increase the inner resistance of the motor, as it is already fitted with 22 turns. If I go too high, the resistance will eventually be too high and every single bit of improved efficiency I get out of 1) using a thicker wire and 2) using higher voltage will vanish into thin air.

A good compromise seemed to be 33 turns 0,56er (double-covered enameled wire) terminated star. This will NOT result in 66% of the original kv of 360 as there are many other factors to keep in mind.

Here is a short summary of how it went:
-The third layer was inevitable. It was possible to fit 14,5 turns in the first layer and 10 in the second. The third layer is somewhat extremely crappy as it will drastically raise the inner resistance of the motor. However as this is a pancake style motor, going into the third layer (and not more!) was a thing that had to be done. This resulted in a not-so-nice look of the winding and somewhat inevitable longer overall wire lengh. The only thing that shines bright on the horizon here is that this disadvantage will be offset by the gained efficiency from 1) thicker overall wiring (1 strand 0,56 double-covered enameled wire against 4 parallel strands of unknown wire) and 2) higher overall voltage (in the final project, 6S versus 4S).

The pictures show how it went, as stated in the first sentence, I'm not extremely proud of it, but the motor should do its job anyways. Winding a pancake-style motor in a clean and neat way like other motors I have wound so far with 33 turns is something that can't be done. In addition, the layers can't get too high as this would cause mechanical problems.

Here is the data I have obtained with my very improvised, very crappy test equipment (student budget...). The RPM have been measured optically - I have covered the outside of the motor with dark tape and have put a white dot as a reference for the laser RPM meter on top of it. That works really great.

Original Motor: 22 turns 4 parallel strands terminated star:
No-Load RPM: 4057
Voltage: 11,22V
No-load current: 0,48A

Rewound-Motor: 33 turns 0,56 terminated star AabBCcaABbcC:
No-Load RPM: 3322
Voltage: 11,16V
No-load current: 1,50A
====> 297kv


This seems as low as I can get. The no-load current of 1,50A is already pretty high which brings me to the fact that 33 turns are already the maximum number of turns you should put on this motor - the inner resistance will simply get too high if you put even more wire on it, no matter if you can increase its thickness by 0,03 or 0,06. The overall kv has decreased by 21,5%, which meets my target.


I would love to get some feedback by you guys. I am still thinking of a matching setup but I will most likely go for 6S and 17x5,5 CF props on 20A 6S simple ESCs by rctimer.

Pictures attached - and sorry again for the not-so-clean wiring.

Malte
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Jul 30, 2015, 06:26 PM
Registered User
Some additions: I am actually thinking of un-doing the 33 turns. As the no-load current went up over 200% this may account for way higher copper losses than expected... Any suggestions/ideas here?

Maybe using a thicker wire and going for 22turns is a better idea - or maybe using the 0,56 wire for approx. 25 turns in only 2 layers.
Jul 31, 2015, 05:00 AM
Registered User
Fourdan's Avatar
Hi Malte
With more turns, 33 versus 22, same voltage ~11.2V :
** The Kv is lower, so the rpm no load
** Normally the no load current has to be LOWER !!
It is not a question of wire diameter nor Rm (ohm)
Something is abnormal !!
Louis
Jul 31, 2015, 09:35 AM
Jack
jackerbes's Avatar
I think there is something wrong here too.

Consider this:

winds_new = winds_old * Kv_old / Kv_new

22 turns = 362 Kv

22 * 362 / 298 = 27

This indicates to me that 33 turns should have given you a much lower Kv than the 298 you got.

Another way to figure it is:

Stock turns Kv * Nr. Turns = Constant

362 Kv * 22 Turns = Constant of 7964

New Kv = Constant / New Nr.Turns

7964 / 33 Turns = 241 Kv

So I think you should have had a lower Kv than your numbers indicate.

No-Load RPM: 3322 / Voltage: 11,16V = 297 Kv

I wonder if all the arms are wound in the right direction...

Jack
Jul 31, 2015, 12:04 PM
homo ludens modellisticus
Ron van Sommeren's Avatar
Phase hookup not correct? Either the three starts or the three beginnings ot the three phases must be connected.

Check with generatortest, also for Jack's suggestions above
(Re)winding and building motors
→ opening post
→ item 37: generator test

Prettig weekend Ron
Last edited by Ron van Sommeren; Jul 31, 2015 at 07:09 PM.
Aug 23, 2015, 12:05 PM
Registered User
Hi guys,

thanks for your input!

I re-wound the motor again, this time using 0,45 wire. The results are better optically, however this is the data I get:

3602 rpm at 11,77 Volts, 1,25A no-load currents.

Equals a kv of 305, roughly the same result as before...

There is no short-circuit in any of the wires, each arm is 33 turns and I didn't mess up the winding scheme.

I have attached the winding scheme I used. Can somebody PLEASE shed some light onto this? Is the winding scheme I used crap? Of course I used the star-wiring where I connect T1-T2-T3 together and E1-E2-E3 go onto the ESC...

Thanks!
Malte
Aug 24, 2015, 04:51 AM
Registered User
Fourdan's Avatar
Quote:
Originally Posted by Nerox
I re-wound the motor again, this time using 0,45 wire. this is the data I get:
3602 rpm at 11,77 Volts, 1,25A no-load currents.
Equals a kv of 305, roughly the same result as before...
There is no short-circuit in any of the wires, each arm is 33 turns
Hi Malte
To predict the performances (under load) of the motor one need the internal resistance phase-phase (or the length of wires for one phase to star) and if possible rpm, V, Io for two or three voltage values.
Anyway are your sure of Io = 0.48A for 22 turns stock winding ?
It is abnormal you get more Io for a lower rpm/V
Louis
Aug 24, 2015, 07:55 AM
Jack
jackerbes's Avatar
Quote:
Originally Posted by Nerox
Hi guys,

thanks for your input!

I re-wound the motor again, this time using 0,45 wire. The results are better optically, however this is the data I get:

3602 rpm at 11,77 Volts, 1,25A no-load currents.

Equals a kv of 305, roughly the same result as before...

There is no short-circuit in any of the wires, each arm is 33 turns and I didn't mess up the winding scheme.

I have attached the winding scheme I used. Can somebody PLEASE shed some light onto this? Is the winding scheme I used crap? Of course I used the star-wiring where I connect T1-T2-T3 together and E1-E2-E3 go onto the ESC...

Thanks!
Malte
Throw that winding image away and print one from this page for a 12 slot 14 pole motor with a Y termination:

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

That will show the scheme as AabBCcaABbcC and you'll notice that all the turns are in the opposite direction from where your image shows.

Either scheme should work exactly the same as one is just a fully reversed version of the other:

AabBCcaABbcC (image generator)
aABbcCAabBCc (your image)

But the termination scheme on yours is just too darned confusing....

If you put the starts on arms 1, 3, and 5 and terminate the three ends in the bundle as shown in the image generator you would have the starts on 1, 3, and 5 and the Wye bundle on 8, 10, and 12.

That would call for:

1, 3, and 5 (e1 t2 e3) for the three motor leads, and

8 + 10 + 12 (t1 e2 t3) for the Wye bundle.

But that is not what your image calls for, it has phase B arranged in a different way and I don't know but what that is affecting something.

Jack
Aug 24, 2015, 08:51 AM
homo ludens modellisticus
Ron van Sommeren's Avatar
Quote:
Originally Posted by Nerox
... Is the winding scheme I used crap? ...
It's ok, been used be many people since the start of diy motorbuilding 15 years ago.

Vriendelijke groeten Ron
Aug 24, 2015, 09:44 AM
Registered User
Fourdan's Avatar
Hi Malte
I agree with Jack reply
I think that you have exchanged t2 and E2
So your winding is (probably) wrong
Louis
Aug 24, 2015, 10:15 AM
Jack
jackerbes's Avatar
Quote:
Originally Posted by Ron van Sommeren
It's ok, been used be many people since the start of diy motorbuilding 15 years ago.

Vriendelijke groeten Ron
Ron, I think there is an error in the terminating notes. At least as I understand that in comparison to the one from the the time honored presentation as seen in the bewicklungsrechner.

Jack
Aug 24, 2015, 11:24 AM
homo ludens modellisticus
Ron van Sommeren's Avatar
My apologies, I had not noticed that it was a translated version of the original, I just glanced at the thumbnail. Termination is not correct. Everything must be rotationsymmetric by 120 degrees.

Malte, where did you find that winding diagram? So we can contact that site and correct the mistake.

Vriendelijke groeten Ron
Last edited by Ron van Sommeren; Aug 24, 2015 at 11:33 AM.
Aug 24, 2015, 09:20 PM
Master Prop Breaker
Did you check the unmodified no-load amp reading with that exact motor or with one of your others your using?

Reason being, and this is a long shot. Looking at the pics you posted, the magnets are marked red for polarity. There seems to be one not marked. It may have just been the last magnet installed or maybe someone had a hangover in China?
Aug 24, 2015, 10:15 PM
Jack
jackerbes's Avatar
They usually stack the magnets to get the like poles matched up and then mark them, then reverse every other magnet as they are installed to set up the alternating poles. If you take a small magnet you can check the poles on the magnets. Like poles attract, unlike repel...

Jack .
Aug 25, 2015, 05:00 AM
Registered User
Hi Jack, Louis and Ron,

Thank you so much for your input!
I see where you guys are coming from. I don't know if I was the one being unconcentrated but on the third glance I see the difference in the winding scheme you're mentioning (I found that winding scheme on google and will post a link later once I re-wound the motor again). Considering that the current re-winding is just a quick&dirty one for testing purposes I will go for a third round and re-wind the motor again using the scheme from the page Jack provided (using the 0,45 wire as it simply fits better. Comparing 0,45 and 0,56 wires I don't think that there will be any benefits from trying to fit 33 turns with 0,56 wire onto that motor...)

On top of that I see the red mark on that magnet and will check later. I indeed did compare this motor to a completly different one regarding no load current etc., as I ordered 4 of those guys and disassembled this one the minute it came in the mail without checking it first. A reversed magnet would be a bummer for sure.


Another question: do you guys think it actually makes sense to go from kv 360 to kv 240 with this motor? If I don't take into account that the efficiency might go up 1% or 2% by not using 4 parallel strands rather than 1 single wire, those 4 motors shall go on a quadcopter (obviously). Most people fly those motors with 360kv on 4s and 17,5x5,5. My thoughts are that the motor with 240kv on 6s and the same propeller should result in equal thrust and rpm but with higher efficiency... Taking copper and iron losses aside, is this thought legit or am I overlooking some basics?

Thank you so so much by the way. I was actually running out of ideas.

Malte


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