Cobra CM-4012/32 300Kv Motor Propeller Data
Magnets Motor Wind Motor Kv No-Load Current Motor Resistance I Max P Max (6S)
22-Pole 30-Turn Wye 300 RPM/Volt Io = 0.69 Amps @ 21v Rm = 0.124 Ohms 22 Amps 490 W
 
Stator Outside Diameter Body Length Total Shaft Length Shaft Diameter Motor Weight
24-Slot 45.5 mm,  1.791 in. 27.9 mm,  1.098 in. 33.5 mm,  1.319 in. 4.00 mm,  0.157 in. 141 gm,   4.97 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 0.461 A 0.517 A .564 A .685 A 308 RPM/Volt @ 21V 0.124 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 5 18.5 8.55 158.2 5,272 27.5 1340 47.27 8.47
APC 16x5.5-MR 5 18.5 12.86 237.9 4,952 25.8 1898 66.95 7.98
APC 18x5.5-MR 5 18.5 17.18 317.8 4,606 24.0 2424 85.50 7.63
GemFan 16x4.5-MR-W 5 18.5 10.86 200.9 5,097 21.7 1637 57.74 8.15
GemFan 18x5-MR-W 5 18.5 14.91 275.8 4,791 22.7 2123 74.89 7.70
GemFan 20x6-MR-W 5 18.5 21.16 391.5 4,252 24.2 2656 93.69 6.78
RC-Timer 13x5.5-CF 5 18.5 8.45 156.3 5,279 27.5 1158 40.85 7.41
RC-Timer 14x5.5-CF 5 18.5 11.81 218.5 5,021 26.2 1469 51.82 6.72
RC-Timer 15x5.5-CF 5 18.5 16.18 299.3 4,695 24.5 1817 64.09 6.07
RC-Timer 16x5.5-CF 5 18.5 18.57 343.5 4,475 23.3 2040 71.96 5.94
RC-Timer 17x5.5-CF 5 18.5 20.81 385.0 4,298 22.4 2204 77.74 5.72
 
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 13x5.5-MR 6 22.2 9.44 209.6 6,320 32.9 1523 53.72 7.27
APC 14x5.5-MR 6 22.2 16.12 357.9 5,788 30.1 1980 69.84 5.53
APC 16x5.5-MR 6 22.2 17.14 380.5 5,695 29.7 2564 90.44 6.74
APC 18x5.5-MR 6 22.2 22.52 499.9 5,211 27.1 3144 110.90 6.29
GemFan 15x4.5-MR-W 6 22.2 10.77 239.1 6,218 26.5 1757 61.98 7.35
GemFan 16x4.5-MR-W 6 22.2 14.37 319.0 5,923 25.2 2244 79.15 7.03
GemFan 18x5-MR-W 6 22.2 19.54 433.8 5,478 25.9 2811 99.15 6.48
RC-Timer 13x5.5-CF 6 22.2 11.74 260.6 6,143 32.0 1612 56.86 6.19
RC-Timer 14x5.5-CF 6 22.2 16.12 357.9 5,788 30.1 1980 69.84 5.53
RC-Timer 15x5.5-CF 6 22.2 21.86 485.3 5,262 27.4 2362 83.32 4.87
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.