Cobra CM-2208/20 Motor Propeller Data
Magnets Motor Wind Motor Kv No-Load Current Motor Resistance I Max P Max (3S)
14-Pole 20-Turn Delta 2000 RPM/Volt Io = 0.77 Amps @ 10v Rm = 0.076 Ohms 20 Amps 220 W
 
Stator Outside Diameter Body Length Total Shaft Length Shaft Diameter Motor Weight
12-Slot 27.7 mm,  1.091 in. 24.0 mm,  0.945 in. 45.2 mm,  1.780 in. 3.17 mm,  0.125 in. 44.2 gm,   1.56 oz
 
Test Data From Input 6.0 V 8.0 V 10.0V 12.0V Measured Kv value Measured Rm Value
Sample Motor Io Value 0.59 A 0.67 A 0.77 A 0.87 A 1988 RPM/Volt @ 10v 0.076 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 5.25x4.75-E 3 11.1 13.34 148.1 17,507 78.7 451 15.91 3.05
APC 5.5x4.5-E 3 11.1 13.67 151.7 17,388 74.1 456 16.08 3.01
APC 6x4-E 3 11.1 14.87 165.1 17,003 64.4 630 22.22 3.82
APC 7x4-SF 3 11.1 21.82 242.2 13,985 53.0 840 29.63 3.47
APC 7x5-E 3 11.1 24.02 266.6 13,272 62.8 797 28.11 2.99
FC 5x4.5 3 11.1 8.66 96.1 19,061 81.2 428 15.10 4.45
FC 5x4.5x3 3 11.1 12.38 137.4 17,825 76.0 534 18.84 3.89
FC 6x4.5 3 11.1 15.47 171.7 16,792 71.6 721 25.43 4.20
GemFan 5x3 3 11.1 6.67 74.0 19,801 56.3 374 13.19 5.05
HQ 5x4 3 11.1 7.13 79.1 18,182 68.9 373 13.16 4.71
HQ 5x4x3 3 11.1 9.25 102.7 17,401 65.9 449 15.84 4.37
HQ 5x4.5-BN 3 11.1 11.17 124.0 16,902 72.0 487 17.18 3.93
HQ 6x3 3 11.1 7.34 81.5 18,128 51.5 419 14.78 5.14
HQ 6x4.5 3 11.1 13.53 150.2 16,206 69.1 645 22.75 4.29
HQ 6x4.5x3 3 11.1 17.60 195.4 15,137 64.5 762 26.88 3.90
HQ 7x4 3 11.1 20.71 229.9 14,250 54.0 850 29.98 3.70
HQ 7x4.5 3 11.1 20.31 225.4 14,351 61.2 865 30.51 3.84
 
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 5.25x4.75-E 4 14.8 17.29 255.9 20,560 92.5 603 21.27 2.36
APC 5.5x4.5-E 4 14.8 17.87 264.5 20,436 87.1 635 22.40 2.40
APC 6x4-E 4 14.8 20.15 298.2 19,829 75.1 837 29.52 2.81
FC 5x4.5 4 14.8 10.89 161.2 22,511 95.9 588 20.74 3.65
FC 5x4.5x3 4 14.8 16.43 243.2 20,828 88.8 718 25.33 2.95
FC 6x4.5 4 14.8 20.09 297.3 19,809 84.4 998 35.20 3.36
HQ 4x4.5-BN 4 14.8 10.45 154.7 22,661 96.6 477 16.83 3.08
HQ 5x3 4 14.8 6.88 101.8 23,580 67.0 442 15.59 4.34
HQ 5x4 4 14.8 10.22 151.3 22,739 86.1 589 20.78 3.89
HQ 5x4x3 4 14.8 13.26 196.2 21,763 82.4 710 25.04 3.62
HQ 5x4.5-BN 4 14.8 16.10 238.3 20,899 89.1 744 26.24 3.12
HQ 6x3 4 14.8 11.06 163.7 22,512 64.0 679 23.95 4.15
HQ 6x4.5 4 14.8 19.62 290.4 19,948 85.0 982 34.64 3.38
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.