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Old May 21, 2007, 08:18 PM
Brunswick, Ohio
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Very nice thread and explanations.

Jim
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Old May 21, 2007, 10:09 PM
Engineer for Christ
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Amherst, VA
Joined Jun 2006
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Thanks for the compliments, guys. I'm still learning. I'm no expert for sure, but I am very happy with all of the motors I'm rewinding. I started rewinding because I'm cheap and don't like spending too much money Now I rewind so I can get exactly what I want out of a motor. The bragging rights to winding your own is also a plus


EDIT: Now I'm becoming an expert (or at least close to it). I'm going into the depths of odd motor design such as the 9 pole-8 magnet and 12 pole - 10 magnet. I also have made a parrallel winds that that propels my pylon racer upwards of 110 mph!

If winding a 9 pole - 8 magnet or 9 pole - 10 magnet, the winding pattern is AaA BbB CcC and you MUST TERMINATE WYE or the motor will vibrate itself to pieces!
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Old Jun 16, 2007, 01:04 PM
Wonderfully Wicked
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Willoughby, Ohio
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Alex,

I think you told me you are using an oscilliscope to measure KV? How are you doing it? One probe on the termination lead, and on lead on a phase? what will I see? Picking up a scope tomorrow from a buddy of mine.

Don
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Old Jun 17, 2007, 05:01 PM
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I use a fairchild semiconductor QRB1114 Infra-red emittier collector pair and a piece of reflective tape on the motor can (or in this case non reflective tape). I'll make you one of these if you like. I used a 7.2 V battery and a 220 ohm resistor on the emittier and a 5.1K ohm on the collector. You get a low voltage (measured at the collector) on the reflection and high voltage when no light is reflected. Pointing this at the motor when running this produces a frequency in revolutions per second. Measure the period (time) between pulses (they will be square waves) which will give you how long it takes for one revolution. Then you divide 60 by the period you get and you get rpm. Make sure you translate the period to seconds (ie 1 ms = .001s).
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Old Jun 17, 2007, 05:10 PM
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Mentor, OH
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Quote:
Originally Posted by IBCrazy
I use a fairchild semiconductor QRB1114 Infra-red emittier collector pair and a piece of reflective tape on the motor can (or in this case non reflective tape). I'll make you one of these if you like. I used a 7.2 V battery and a 220 ohm resistor on the emittier and a 5.1K ohm on the collector. You get a low voltage (measured at the collector) on the reflection and high voltage when no light is reflected. Pointing this at the motor when running this produces a frequency in revolutions per second. Measure the period (time) between pulses (they will be square waves) which will give you how long it takes for one revolution. Then you divide 60 by the period you get and you get rpm. Make sure you translate the period to seconds (ie 1 ms = .001s).
isn't that called a FLUX capacitor? and if you do 90 mph's with it, will i go back to the future?

the only problem is....where do you get some gigga watts?
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Old Jun 17, 2007, 05:30 PM
Wonderfully Wicked
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Jack....Jack....Jack..... its 88 mph

Alex,

I thought you were measuring the pulses on the ESC line. You went ahead and built yourself an IR RPM sensor and are counting the frequency pulses. Nice job!

Here is how I did it. I hooked one of the motor lines up to one of the scope probes. I used my Eagletree logger in Live mode to set my voltage input voltage to 10.0 volts (what I wanted). The I got the period from the scope and calculated the RPM based on the frequency and poles of the motor.

Here is a cut and paste from my post in the LSJS thread so you can see what I did.

RPM = (f * 60)/( .5 * no of poles)

f = frequency: 2280 Hz
no of poles= 6

RPM= (2280*60)/(.5*6) = 45600 RPM
voltage= 10.11 volts

KV= 45600/10.11 = 4510 rpm/volt

Eagletree brushless RPM readout = 45454 RPM
Scope RPM = 45600 RPM

So KV has been determined by five different methods.

1) Oscilliscope : 4510
2) Eagletree Brushless RPM Sensor : 4446
3) Eagletree Optical RPM Sensor : 4532
4) Hyperion Emeter Optical RPM sensor : 4466
5) Drive Calc KV calculation based on loaded motor data : 4425

Average of the 5 methods used is 4476 with a standard deviation of 44, which is less than 1%.

Don
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Old Jun 17, 2007, 06:45 PM
Engineer for Christ
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Amherst, VA
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Quote:
Originally Posted by The Don
Jack....Jack....Jack..... its 88 mph

Alex,

I thought you were measuring the pulses on the ESC line. You went ahead and built yourself an IR RPM sensor and are counting the frequency pulses. Nice job!

Here is how I did it. I hooked one of the motor lines up to one of the scope probes. I used my Eagletree logger in Live mode to set my voltage input voltage to 10.0 volts (what I wanted). The I got the period from the scope and calculated the RPM based on the frequency and poles of the motor.

Here is a cut and paste from my post in the LSJS thread so you can see what I did.

RPM = (f * 60)/( .5 * no of poles)

f = frequency: 2280 Hz
no of poles= 6

RPM= (2280*60)/(.5*6) = 45600 RPM
voltage= 10.11 volts

KV= 45600/10.11 = 4510 rpm/volt

Eagletree brushless RPM readout = 45454 RPM
Scope RPM = 45600 RPM

So KV has been determined by five different methods.

1) Oscilliscope : 4510
2) Eagletree Brushless RPM Sensor : 4446
3) Eagletree Optical RPM Sensor : 4532
4) Hyperion Emeter Optical RPM sensor : 4466
5) Drive Calc KV calculation based on loaded motor data : 4425

Average of the 5 methods used is 4476 with a standard deviation of 44, which is less than 1%.

Don
Well, you can do it that way too, I guess. I made the IR rpm tach because I got the QRB1114 chip as a free sample. You know me, I'm cheap I got my oscilloscope from a flea market for $20. To each his own
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Old Aug 15, 2007, 10:23 PM
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I think I've come up with an empirical formula for making a blind guess on a new motors kv. This is good for most 9 pole out runners with a stator diameter between 22 and 25 mm.

KV ~= 36000/(L*P*T) for wye motors

KV ~= 59500/(L*P*T) for Delta

Where L is the length of your stator in inches, P is the number of poles, and T is the number of turns per pole. This will vary slightly from motor to motor, but it gets you in the ball park. If you have a motor where you have 6 magnets (Like the one I rewound in this tutorial) multiply your KV by 2.

-Alex
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Old Sep 17, 2007, 09:36 AM
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Alex, I suppose the question I have is how do you start the wind and how do you get from one armature to the next? Do you have any photos of the other side of the stator?
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Old Sep 17, 2007, 03:43 PM
Maz
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Paul,

Go to gobrushless.com and click on tutorials. Plenty of pictures there.
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Old Sep 18, 2007, 08:22 AM
Engineer for Christ
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Amherst, VA
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Go brushless has some good tutorials as Maz pointed out. To answer your question though, start on any pole with ample wire coming out of the back of the motor, wind the number of turns you want, and then skip two poles going over the backside of the motor (between the mount and the stator) and begin winding again. It is self explanitory when you unwind an old one. It will be clear how to rewind it. I'll see if I can post a picture of the backside of one of my motors with the mount removed.

Just remember to go only one direction for all poles, clockwise or counter clockwise. I wind all of my motors clockwise around each pole and then move over three poles in the clockwise direction (with the front of the motor facing you and the mount away from you).

So if you wind clockwise looking down on the motor with the front of the motor toward you your next pole would be three poles to your right side passing the other two poles between the rear of the stator and the motor mount. When going to your second phase, it is best to start one pole to the right of where you started your first phase. Same thing with the third phase.

Hope that helps,

-Alex
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Old Jun 19, 2008, 03:19 PM
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Same motor -Wye vs Delta Performance

This guy brought the windings out and made a plugs so that he can switch the motor from wye to delta and back. He talks about the results:

"This motor draws a little under 2 amps on 2 Li-Po cells with a 5-1/4 x 4 prop when wired in the Wye configuration. In the Delta configuration, it draws about 5 amps on the same prop, but it also turns about 2500 RPM faster (11,200 in Delta vs 8,700 in Wye)."


http://www.rcgroups.com/forums/showthread.php?t=392174


--and thanks for putting this thread together. I'm about to rewind a burned out motor.
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Old Jun 19, 2008, 04:55 PM
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Ok, success - kind of. I rewound the motor with 30 turns of 30 guage wire in a wye. It draws 2.5 amp on full w/a 9x47 gws slow flyer. Thing is, the stator gets hot though, so I'm sure it's way over-propped. My goal is to replace a GWS IPX brushed motor in a Tiger Moth. So, I'm looking for low KV, and ideally swinging a 10x47 prop.

Any suggestions on # of turns and gauge (I have 24, 26, and 30) wire to use for something like this?
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Old Jun 19, 2008, 06:51 PM
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Akron, Ohio
Joined Aug 2006
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Quote:
Originally Posted by kdahlhaus
Ok, success - kind of. I rewound the motor with 30 turns of 30 guage wire in a wye. It draws 2.5 amp on full w/a 9x47 gws slow flyer. Thing is, the stator gets hot though, so I'm sure it's way over-propped. My goal is to replace a GWS IPX brushed motor in a Tiger Moth. So, I'm looking for low KV, and ideally swinging a 10x47 prop.

Any suggestions on # of turns and gauge (I have 24, 26, and 30) wire to use for something like this?
30 turns is A LOT. what are the dimensions of your stator? 24 awg is my favorite wire gauge, but the size of the motor has a lot to do with it.
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Old Jun 19, 2008, 09:52 PM
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I'll have to measure it. Just rewound with 20 turns of 26 gauge. Will have to wait until tomorrow to try it out.
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