Cobra CM-4010/20 550Kv Motor Propeller Data
Magnets Motor Wind Motor Kv No-Load Current Motor Resistance I Max P Max (6S)
22-Pole 20-Turn Wye 550 RPM/Volt Io = 1.25 Amps @ 21v Rm = 0.054 Ohms 30 Amps 660 W
 
Stator Outside Diameter Body Length Total Shaft Length Shaft Diameter Motor Weight
24-Slot 45.5 mm,  1.791 in. 26.1 mm,  1.027 in. 29.2 mm,  1.150 in. 4.00 mm,  0.157 in. 124 gm,   4.37 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 0.947 A 1.014 A 1.136 A 1.248 A 553 RPM/Volt @ 21V 0.054 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 12x4.5-MR 4 14.8 14.25 210.9 7,106 37.0 1438 50.72 6.82
APC 13x5.5-MR 4 14.8 19.06 282.1 6,845 35.7 1810 63.85 6.42
APC 14x5.5-MR 4 14.8 23.11 342.0 6,586 34.3 2138 75.41 6.25
APC 16x5.5-MR 4 14.8 32.90 486.9 5,881 30.6 2752 97.07 5.65
GemFan 12x4-MR-W 4 14.8 13.08 193.6 7,280 27.6 1342 47.34 6.93
GemFan 13x4.5-MR-W 4 14.8 16.49 244.1 7,052 30.1 1629 57.46 6.67
GemFan 14x4.5-MR-W 4 14.8 19.40 287.1 6,834 29.1 1919 67.69 6.68
GemFan 15x4.5-MR-W 4 14.8 21.33 315.7 6,707 28.6 2065 72.84 6.54
GemFan 16x4.5-MR-W 4 14.8 27.92 413.2 6,231 26.6 2497 88.08 6.04
RC-Timer 11x5.5-CF 4 14.8 11.23 166.2 7,414 38.6 1063 37.50 6.40
RC-Timer 12x5.5-CF 4 14.8 17.75 262.7 6,966 36.3 1518 53.55 5.78
RC-Timer 13x5.5-CF 4 14.8 23.31 345.0 6,577 34.3 1867 65.86 5.41
RC-Timer 14x5.5-CF 4 14.8 31.15 461.0 6,036 31.4 2174 76.68 4.72
 
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 10x4.5-MR 5 18.5 12.64 233.8 9,236 48.1 1342 47.34 5.74
APC 11x4.5-MR 5 18.5 16.07 297.3 8,979 46.8 1704 60.11 5.73
APC 12x4.5-MR 5 18.5 20.78 384.4 8,643 45.0 2133 75.24 5.55
APC 13x5.5-MR 5 18.5 27.52 509.1 8,115 42.3 2617 92.31 5.14
APC 14x5.5-MR 5 18.5 33.12 612.7 7,703 40.1 3024 106.67 4.94
GemFan 11x4-MR-W 5 18.5 13.90 257.2 9,145 34.6 1536 54.18 5.97
GemFan 12x4-MR-W 5 18.5 18.63 344.7 8,787 33.3 1983 69.95 5.75
GemFan 13x4.5-MR-W 5 18.5 23.54 435.5 8,431 35.9 2381 83.99 5.47
GemFan 14x4.5-MR-W 5 18.5 27.60 510.6 8,123 34.6 2750 97.00 5.39
GemFan 15x4.5-MR-W 5 18.5 30.39 562.2 7,882 33.6 2947 103.95 5.24
RC-Timer 10x5.5-CF 5 18.5 10.86 200.9 9,384 48.9 1154 40.71 5.74
RC-Timer 11x5.5-CF 5 18.5 16.75 309.9 8,931 46.5 1607 56.68 5.19
RC-Timer 12x5.5-CF 5 18.5 26.24 485.4 8,146 42.4 2209 77.92 4.55
RC-Timer 13x5.5-CF 5 18.5 34.55 639.2 7,665 39.9 2618 92.35 4.10
 
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 9x4.5-MR 6 22.2 12.81 284.4 11,148 47.5 1388 48.96 4.88
APC 10x4.5-MR 6 22.2 17.38 385.8 10,778 45.9 1866 65.82 4.84
APC 11x4.5-MR 6 22.2 22.08 490.2 10,403 44.3 2353 83.00 4.80
APC 12x4.5-MR 6 22.2 28.32 628.7 9,918 42.3 2884 101.73 4.59
GemFan 10x4-MR-W 6 22.2 15.96 354.3 10,894 41.3 1786 63.00 5.04
GemFan 11x4-MR-W 6 22.2 18.70 415.1 10,682 40.5 2134 75.27 5.14
GemFan 12x4-MR-W 6 22.2 24.87 552.1 10,182 38.6 2686 94.74 4.86
GemFan 13x4.5-MR-W 6 22.2 31.34 695.7 9,666 41.2 3151 111.15 4.53
RC-Timer 10x5.5-CF 6 22.2 14.91 331.0 10,970 57.1 1623 57.25 4.90
RC-Timer 11x5.5-CF 6 22.2 23.07 512.2 10,339 53.8 2207 77.85 4.31
RC-Timer 12x5.5-CF 6 22.2 36.60 812.5 9,364 48.8 2919 102.96 3.59
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.