
Apr 20, 2011, 08:41 AM  
Windsor, Canada, near Detroit
Joined Jul 2007
4,765 Posts

motor constants by Joachim Bergmeyer
i think adding his formulas could help to increase the knowledge of our motors. i have been using them and learned a lot about motors.
here is the link: http://www.rcgroups.com/forums/showthread.php?t=185271 he also has another formulas for a simplified method: http://flbeagle.rchomepage.com/resea...per_ver_02.pdf . 

May 08, 2011, 06:02 AM  
Czech Rep.
Joined Aug 2006
302 Posts

Hi guys,
I hope this is not much OT. For more than a year we have been using so called tax power formula for evaluating the input power in our local esailplanes competitions. The general formula is Pd=0.4*d*L*(kv*U*D/100000)^2 where Pd is tax power [W] kv is motor constant [RPM/V] U is battery nominal voltage [V] D is propeller diameter [inch] d is air gap diameter [mm] L is air gap length [mm] For "small outrunners" (with a bell diameter of 28 mm) it is slightly modified as Pd = 10*L*(kv*U*D/100000)^2 The calculation sheet is here: http://www.rcex.cz/kestazeni/taxpower_calc.xls. Examples: Axi 2814/10, 2S lipol, propeller 9.5x5: tax power is 0.4*28*14*(1640*7.4*9.5/1e5)^2 = 208 W, measured 210 W (this is what I fly in the AH Castor) TG 28261650, 2S lipol, 10x6 (this outer 2826 = inner 2209): tax power = 10*9*(1650*7.4*10/1e5)^2 = 134 W, measured 135 W (my "small outrunner" sailplane). Now, while the measured (static) values correspond to the calculated "tax power" values reasonably well, I am not able to get anything close to this formula theoretically. Would someone of you more educated experts be able to help? Thanks, Jan 
Oct 16, 2011, 03:44 AM  
Joined Oct 2011
14 Posts

Hi
I see all of you appear like RC motor experts because you discuss about motor formulas. I understand this forum place is for DIYers where advanced members like to help others in theirs fields. I have many technician skills, but RC aircrafts is field where I am not familiar so, and I am here new. So please, go in my thread "The basics of building RC aircraft motor where rotor is permanent magnet?" and help me something there. Thanks in advance :), Peter 
Oct 26, 2012, 05:31 PM  

I have a question about inductance? I have been messing with the timing on my ESCs to better match the pole counts of my motors and having good results. Now I am thinking of changing the PWM Pulse width Mod, but am hesitant because most of my ESCs Eflite pros tell you to check a motors inductance before changing. My problem is I don't know if the Ohm resistance reading is a measure for the Inductance which I understand as a magnetic field induced by electricity. Seems none of the motor manufactures list the inductance so I am assuming it needs to be interpolated.

Nov 04, 2012, 08:54 AM  
Joined Nov 2012
1 Posts

hi
This is the best site. Here you can get lots of information about various product. i have read the question but i don't know the answer. sorry for that.  Top Ten classified website 
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