Rewinding Emax CF2805 & CF2822 - Page 3

eruji · Mar 29, 2009, 11:50 PM

i just rewound an emax cf2822 yesterday which i think is the same as the fc28-22. It was defective when i got it.. and this is my second wind.. my first was a bluewonder 1300kv. I wound it with 18 turns of 26awg wire dlrk. I have no idea what the kv on this is. How do you figure that out? i dont understand the drill test. I put the motor into my MiniMag which about 24 ounces AUW. I have not gotten a chance to fly it yet.. I hooked it up to my homemade shunt multimeter and it only registers 6-7 amps at full throttle.. that doesnt seem right. The stock motor with this gws 8040 prop should be around 12 amps. I ran it on full throttle for about a minute and does not even seem warm.

MiseryQ · Mar 30, 2009, 12:06 AM

Put the shaft of the motor in to drill with a known RPM and hold the stator stationary.
Connect a multimeter set on volts AC to two of the legs, they'll be 3 combos,

Divide the RPM by the measured vol/tage and you'll get close to the kv.

yardboz1 · Mar 30, 2009, 10:32 AM

Quote:

Originally Posted by MiseryQ

Connect a multimeter set on volts AC to two of the legs, they'll be 3 combos,

Do you just hook the test leads to 2 of the motor leads? And what do you mean by "3 combos"? Sorry for the noob questions.

Sterling

eruji · Mar 30, 2009, 10:37 AM

Is the RPM listed on some drills? i have no idea what rpm my drill is.

Quote:

Connect a multimeter set on volts AC to two of the legs, they'll be 3 combos,

i think he means that you have 3 motor leads.. using the 2 leads from your multimeter you would have to match it 3 times to get all readings.. so

Motor lead 1
Motor lead 2
Motor lead 3

meter lead A
meter lead B

you would match
1A and 2B
then 2A 3B
then 3A 1B

MiseryQ · Mar 30, 2009, 11:03 AM

Some drills have the RPM listed on a sticker.
I have 3 and one doesn't have a speed.
Lets say the motor has the "normal" Red, Black and White wires.
You'd measure across:
Red - Black
Red - White
Black - White

The leads on the multimeter makes no difference since it's AC.

yardboz1 · Mar 30, 2009, 11:19 AM

Thanks for the quick responses. Wasn't sure how to hook this up and I didn't want to fry something.

Sterling

MiseryQ · Mar 30, 2009, 02:00 PM

Here's the numbers I just measured with the clamp-on meter. BTW, Is badcock.net totally wrong?

No Load Current was 2.7amps at 11.80v
With the APC 6x4e 23.7amps at 10.23v

Apparently my Li-Po isn't holding too good(?)
Badcock.net Results

Ron van Sommeren · Mar 30, 2009, 04:21 PM

Four methods for determining Kv (Christo van der Merwe = RCG user 'Skylar')
http://www.bavaria-direct.co.za/
-> Motor building Info
-> How to determine the Kv of a motor

Ken Myers' article and spreadsheet:
http://homepage.mac.com/kmyersefo/M1...runners.htm#KV
http://homepage.mac.com/kmyersefo/Kv-Worksheet.xls

Measuring Kv quick'n dirty:
http://www.rcgroups.com/forums/showthread.php?t=1009271
http://www.rcgroups.com/forums/showthread.php?t=1009491
http://www.rcgroups.com/forums/showthread.php?t=983725

Vriendelijke groeten

Ron

yardboz1 · Mar 30, 2009, 10:43 PM

Thanks Ron. Another of your links saved in my favorites!

Sterling

MiseryQ · Mar 31, 2009, 08:09 AM

That first link has a fomula I don't understand.

Quote:

Method 3 (Colin Dedman's formula) - this is my favourite method

1. Drive the motor with a power drill.

2. Measure RPM and voltage generated (by one phase).

3. Kv = ((RPM/ volt) / 1.41) / 0.95

This seems to give a real low kv yet he says it's his favorite method.

yardboz1 · Mar 31, 2009, 10:57 PM

I've done a little searching on this subject (not to question anyone, but because I didn't understand it also) and what I found was " The 1.41 comes from converting Volts DC (using a battery at full voltage to power a motor)and the .95 accounts for losses on the wire from the source to the motor." Apparently when using this method you initially get a higher KV figure than what the motor actually is, and the 2 divisions will give you a more realistic figure. I have no idea if this is correct or not, but I will check some of my motors (with known kv's)tomorrow after work and see what they come out as.

Sterling

MiseryQ · Mar 31, 2009, 11:05 PM

1200/.44=2727kv

((1200/.44)/1.41)/.95=2036kv

That's a big difference. It doesn't seem to add up.

annihil8ted · Apr 09, 2009, 11:43 PM

hello, im rewinding my 2805 tonight after the poor performanc it showed. Even with a 6x5.5 on 3s, the thing was enot even pushing 10oz.

I was hoping if anyone can tell me what was the original wind. Like what gauge and how many winds and how many wires in each wind.

Much appreciated.

MiseryQ · Apr 09, 2009, 11:56 PM

IIRC the stock wind of the 2805 and the 2822 was the same: 15 turns, 3 strands of 30AWG.

i don't think it has enough ass to turn a 6x5.5.
I think you'd be happy with the 11turns of 24.
It spind a Graupner 5.5x4.3 with authority. Lots of thrust and good speed.

I'm thinking my 2822 might not turn a 6x5.5 too good without amps getting reall high.

annihil8ted · Apr 10, 2009, 12:14 AM

Sorry, please be patient with me, being in highschool and just starting physics this is all new to me.

If the motor can't handle the prop, wouldnt it burn up? Well i just did a test and not only was it cold, the Watt's Up meter showed that even with 5x5 APC on 3s 1500mah, amp was only 6.5. Im starting to think i got a faulty motor.

Mar 30, 2009, 04:21 PM	#38
Ron van Sommeren homo ludens modellisticus Join Date: Feb 2001 Location: near Nijmegen, Netherlands Posts: 8,674	Four methods for determining Kv (Christo van der Merwe = RCG user 'Skylar') http://www.bavaria-direct.co.za/ -> Motor building Info -> How to determine the Kv of a motor Ken Myers' article and spreadsheet: http://homepage.mac.com/kmyersefo/M1...runners.htm#KV http://homepage.mac.com/kmyersefo/Kv-Worksheet.xls Measuring Kv quick'n dirty: http://www.rcgroups.com/forums/showthread.php?t=1009271 http://www.rcgroups.com/forums/showthread.php?t=1009491 http://www.rcgroups.com/forums/showthread.php?t=983725 Vriendelijke groeten Ron Last edited by Ron van Sommeren; Mar 31, 2009 at 09:26 AM.

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Mar 29, 2009, 11:50 PM	#31
eruji "plane don't hurt" Join Date: Aug 2005 Location: Mountain Home Village, CA Posts: 328	i just rewound an emax cf2822 yesterday which i think is the same as the fc28-22. It was defective when i got it.. and this is my second wind.. my first was a bluewonder 1300kv. I wound it with 18 turns of 26awg wire dlrk. I have no idea what the kv on this is. How do you figure that out? i dont understand the drill test. I put the motor into my MiniMag which about 24 ounces AUW. I have not gotten a chance to fly it yet.. I hooked it up to my homemade shunt multimeter and it only registers 6-7 amps at full throttle.. that doesnt seem right. The stock motor with this gws 8040 prop should be around 12 amps. I ran it on full throttle for about a minute and does not even seem warm.

Mar 30, 2009, 12:06 AM	#32
MiseryQ Registered User Join Date: May 2006 Location: Norfolk, Va Posts: 1,775	Put the shaft of the motor in to drill with a known RPM and hold the stator stationary. Connect a multimeter set on volts AC to two of the legs, they'll be 3 combos, Divide the RPM by the measured vol/tage and you'll get close to the kv.

Mar 30, 2009, 11:03 AM	#35
MiseryQ Registered User Join Date: May 2006 Location: Norfolk, Va Posts: 1,775	Some drills have the RPM listed on a sticker. I have 3 and one doesn't have a speed. Lets say the motor has the "normal" Red, Black and White wires. You'd measure across: Red - Black Red - White Black - White The leads on the multimeter makes no difference since it's AC.

Mar 30, 2009, 11:19 AM	#36
yardboz1 Registered User Join Date: Sep 2007 Location: LaSalle, Illinois Posts: 390	Thanks for the quick responses. Wasn't sure how to hook this up and I didn't want to fry something. Sterling

Mar 30, 2009, 02:00 PM	#37
MiseryQ Registered User Join Date: May 2006 Location: Norfolk, Va Posts: 1,775	Here's the numbers I just measured with the clamp-on meter. BTW, Is badcock.net totally wrong? No Load Current was 2.7amps at 11.80v With the APC 6x4e 23.7amps at 10.23v Apparently my Li-Po isn't holding too good(?) Badcock.net Results

Mar 30, 2009, 10:43 PM	#39
yardboz1 Registered User Join Date: Sep 2007 Location: LaSalle, Illinois Posts: 390	Thanks Ron. Another of your links saved in my favorites! Sterling

Mar 31, 2009, 10:57 PM	#41
yardboz1 Registered User Join Date: Sep 2007 Location: LaSalle, Illinois Posts: 390	I've done a little searching on this subject (not to question anyone, but because I didn't understand it also) and what I found was " The 1.41 comes from converting Volts DC (using a battery at full voltage to power a motor)and the .95 accounts for losses on the wire from the source to the motor." Apparently when using this method you initially get a higher KV figure than what the motor actually is, and the 2 divisions will give you a more realistic figure. I have no idea if this is correct or not, but I will check some of my motors (with known kv's)tomorrow after work and see what they come out as. Sterling

Mar 31, 2009, 11:05 PM	#42
MiseryQ Registered User Join Date: May 2006 Location: Norfolk, Va Posts: 1,775	1200/.44=2727kv ((1200/.44)/1.41)/.95=2036kv That's a big difference. It doesn't seem to add up.

Apr 09, 2009, 11:43 PM	#43
annihil8ted Registered User Join Date: May 2008 Location: San Diego Posts: 424	hello, im rewinding my 2805 tonight after the poor performanc it showed. Even with a 6x5.5 on 3s, the thing was enot even pushing 10oz. I was hoping if anyone can tell me what was the original wind. Like what gauge and how many winds and how many wires in each wind. Much appreciated.

Apr 09, 2009, 11:56 PM	#44
MiseryQ Registered User Join Date: May 2006 Location: Norfolk, Va Posts: 1,775	IIRC the stock wind of the 2805 and the 2822 was the same: 15 turns, 3 strands of 30AWG. i don't think it has enough ass to turn a 6x5.5. I think you'd be happy with the 11turns of 24. It spind a Graupner 5.5x4.3 with authority. Lots of thrust and good speed. I'm thinking my 2822 might not turn a 6x5.5 too good without amps getting reall high.

Apr 10, 2009, 12:14 AM	#45
annihil8ted Registered User Join Date: May 2008 Location: San Diego Posts: 424	Sorry, please be patient with me, being in highschool and just starting physics this is all new to me. If the motor can't handle the prop, wouldnt it burn up? Well i just did a test and not only was it cold, the Watt's Up meter showed that even with 5x5 APC on 3s 1500mah, amp was only 6.5. Im starting to think i got a faulty motor.