Cobra CM-3520/28 350Kv Motor Propeller Data
Magnets Motor Wind Motor Kv No-Load Current Motor Resistance I Max P Max (6S)
14-Pole 28-Turn Delta 350 RPM/Volt Io = 0.43 Amps @ 15v Rm = 0.117 Ohms 26 Amps 580 W
 
Stator Outside Diameter Body Length Total Shaft Length Shaft Diameter Motor Weight
12-Slot 43.0 mm,  1.693 in. 52.0 mm,  2.047 in. 55.6 mm,  2.189 in. 5.00 mm,  0.197 in. 234 gm,   8.25 oz
 
Test Data From Input 12.0 V 15.0 V 18.0V 21.0V Measured Kv value Measured Rm Value
Sample Motor Io Value 0.40 A 0.43 A 0.46 A 0.49 A 346 RPM/Volt @ 15V 0.117 Ohms
 
Prop Prop Li-Po Input Motor Input Prop Pitch Speed Thrust  Thrust Thrust Eff.
Manf. Size Cells Voltage Amps Watts RPM in MPH Grams Ounces Grams/W
APC 14x5.5-MR 6 22.2 12.54 278.4 6,317 32.9 1962 69.21 7.05
APC 16x5.5-MR 6 22.2 17.98 399.2 5,845 30.4 2634 92.91 6.60
APC 18x5.5-MR 6 22.2 22.84 507.0 5,425 28.3 3194 112.66 6.30
GemFan 15x4.5-MR-W 6 22.2 11.63 258.2 6,416 27.3 1872 66.03 7.25
GemFan 16x4.5-MR-W 6 22.2 15.53 344.8 6,031 25.7 2336 82.40 6.78
RC-Timer 13x5.5-CF 6 22.2 12.44 276.2 6,339 33.0 1690 59.61 6.12
RC-Timer 14x5.5-CF 6 22.2 16.80 373.0 5,940 30.9 2068 72.95 5.54
RC-Timer 15x5.5-CF 6 22.2 22.63 502.4 5,446 28.4 2442 86.14 4.86
RC-Timer 16x5.5-CF 6 22.2 25.42 564.3 5,181 27.0 2717 95.84 4.81
RC-Timer 17x5.5-CF 6 22.2 27.72 615.4 4,959 25.8 2878 101.52 4.68
Propeller Chart Color Code Explanation
   The prop is to small to get good performance from the motor. (Less than 50% power)
   The prop is sized right to get good power from the motor. (50 to 80% power)
   The prop can be used, but full throttle should be kept to short bursts. (80 to 100% power)
   The prop is too big for the motor and should not be used. (Over 100% power)
PLEASE NOTE:
The Data contained in this Prop Chart is based on actual measurements, taken in a controlled test environment, at an altitude of
512 feet above sea level.  The test voltages used are based on the standard output of a Li-Po battery under load, which is 3.70 volts
per cell.  If you are using a battery that is larger in capacity than normal, or has a very high C-rating, then your actual voltages will
be higher than those shown in the chart, and this will result in a higher current and power value for every prop used.  You should
always test your actual power system with a watt meter before flying your model to make sure that you are not exceeding the 
recommended current and power ratings of the motor being used.  The prop recommendations in this chart assume that the motor
receives adequate cooling throughout its operation.  If your motor is being used inside a cowl or fuselage, you must ensure that
the motor receives sufficient airflow, and does not get too hot during operation.  It is always best to use a prop size that pulls no
more than 80% of the motors maximum recommended current value to ensure safe operation under all conditions.