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Old Aug 18, 2014, 09:09 AM
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335driver's Avatar
USA, TX, Round Rock
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Question
KV of motor

Is there a way to figure the KV of a motor ? Here's all the info---battery is 3S 2200mAH
30C ESC 60A motor MegaMotor 16/15/1 KV unknown WattMeter shows 53A and 530 Watts at WOT...
Any clues ?? 3 minute flight used almost 70% of battery.

Thanks,
Dick
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Old Aug 18, 2014, 09:40 AM
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http://www.megamotor.cz/v4/script/de...ge_id=lang_eng

Scroll down to see chart
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Old Aug 18, 2014, 10:37 AM
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Tricky to find read that site
So it's 8000kv ?? Doesn't seem as even remotely correct for your use, if it's accurate
Beyond that... that's a smallish battery.
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Old Aug 18, 2014, 12:03 PM
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Could also be one of these???

http://www.rc-base.com/engine/mega-m...ga-motor-16151

http://megamotorusa.com/BrushlessNew/ACn16-15-1.htm

http://www.icare-rc.com/mega_acn1615.htm#ACn_16/15/1

http://www.icare-icarus.com/Mega-Mot...151_p_676.html

I have no idea what the difference between them is, but Kv does seem to vary.
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Old Aug 18, 2014, 12:11 PM
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I think there was 2 version of the 16/15/1. One for EDF .I need to check the old charts. Is this a 50mm or 60mm fan to get the numbers you have..seems very low. But then its been a long time since I ran one in a fan.
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Old Aug 18, 2014, 12:14 PM
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Post Falls, ID United States
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I have used the 16/15/2 in a Vassa 65mm EDF and an Alfa 55mm EDF and its a beast of a motor in its day years ago.
16 refers to the rotor diameter, 15 refers to the magnet length, and 1,2,3 etc is the number winds. Thats why the motor is pretty short. The longer version has more torque and is even better for EDF.

The /1 motor does have an 8000KV rating.
The torque will be low and the amp draw will be high so keep that in mind.

Which fan are you using that motor in?
Your numbers are typical of what Im describing for a motor like that. I would get 5min flights on the same battery pack specs you have with the /2 motor.
Also seems to me your at the limits of that set up because just the peak values are off the charts of what is acceptable.
12.6V X 8000 = 100800rpm
Even if I assume 80% efficiency thats still over 80000rmp
You couldn't turn a 4.75X4.75 prop without maxing out temps and amps very easily.
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Old Aug 18, 2014, 03:52 PM
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Thanks to everyone who responded... the one thing I didn't mention was the fan I'm using is a 60mm WM300. It does go pretty good but I don't like the high amps and the fact that everything is getting hot. Not good to run the ESC that close to rated Amps, I don't believe. I got this motor with a Wemo 70mm fan awhile ago, don't remember why I changed out the fan, but I fried a 40A ESC with the motor/fan combo I'm using now. Then I got this motor, the guy said in the Wemo fan, it was just to fast for him.
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Old Aug 18, 2014, 04:01 PM
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Yea that is way too much for the WM fans..they like amps
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Old Aug 19, 2014, 12:01 AM
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Well, I was very surprised to see the KV of this motor. Had no idea it was that high. I don't think it's turning 80K it's not that fast. And Velocity RC sells a 4600KV motor w/WM300 as a combo. I have another 300 with a 3000KV Het motor and it drew about 30 A and 320 watts w 75A ESC. I'm wondering if it might be better to swap out the motor/fan and see how it flies that way.
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Old Aug 22, 2014, 03:25 PM
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I replaced the MegaMotor and was surprised to see it's a /2 which is half the KV as the /1. Don't know why I thought it was a /1. Anyhow, the specs for the /2 call for a 40A ESC but yet I was pulling 50+ Amps and in the specs Icare said for aerobatic plane 75mm impeller. So why the difference?
With 3S (say 12v) x 4600 KV = 55K rpm. Could it be fan choice?
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Old Aug 22, 2014, 03:53 PM
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You could ask Gary at eflux he has a lot of numbers for the WM fan. But I know they are amp hungry. I have only tested /flown the WM400
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Old Aug 22, 2014, 04:05 PM
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I think when Icare said that, they may have been refering to prop size, not a 75mm rotor.

" Recommended propeller for aerobatic airplane ---impeller 75 mm " which is 2.952"
http://www.icare-rc.com/mega_acn1615.htm#ACn_16/15/2
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Old Aug 23, 2014, 12:03 AM
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Cooler,,,,that's really what I thought but who knows "the shadow knows" (gotta be old to get that,right)
turbo, you must be right but why ? I just put my Wattmeter on a CS70mm 4 blade w /2W-20 on a 4S 2650 and it didn't go anywhere near the MegaMotor. Can it be the pitch of the rotor blades?
Also, what do you mean when you say they are amp hungry. Excuse my ignorance because I usually just use what the Mfg. recommends. I think the best running set-up I got is the E-Flite V15 w/3600 KV motor.
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Old Aug 23, 2014, 12:35 AM
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Quote:
Cooler,,,,that's really what I thought but who knows "the shadow knows" (gotta be old to get that,right)
I was born -- Oct 1952- does that qualify??..
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Old Aug 23, 2014, 12:00 PM
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By Amp hungry they pull more amps than other fans on the same KV motor. They have more pitch and very large/ wide cord blades. They have very good performance but are noisy.
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