Cobra CM-2820/24 490Kv Motor Propeller Data
Magnets Motor Wind Motor Kv No-Load Current Motor Resistance I Max P Max (6S)
14-Pole 24-Turn Delta 490 RPM/Volt Io = 0.53 Amps @ 15v Rm = 0.111 Ohms 27 Amps 600 W
 
Stator Outside Diameter Body Length Total Shaft Length Shaft Diameter Motor Weight
12-Slot 35.0 mm,  1.378 in. 46.4 mm,  1.827 in. 52.6 mm,  2.071 in. 5.00 mm,  0.197 in. 146 gm,   5.15 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 0.47 A 0.53 A 0.58 A 0.63 A 490 RPM/Volt @ 15V 0.111 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 9.41 139.3 6,351 27.1 1111 39.19 7.98
APC 14x5.5-MR 4 14.8 15.34 227.0 5,827 30.3 1641 57.88 7.23
APC 16x5.5-MR 4 14.8 21.30 315.2 5,277 27.5 2141 75.52 6.79
APC 18x5.5-MR 4 14.8 25.96 384.2 4,767 24.8 2453 86.53 6.38
GemFan 14x4.5-MR-W 4 14.8 13.02 192.7 6,025 25.7 1454 51.29 7.55
GemFan 15x4.5-MR-W 4 14.8 14.08 208.4 5,919 25.2 1545 54.50 7.41
GemFan 16x4.5-MR-W 4 14.8 18.53 274.2 5,533 23.6 1918 67.65 6.99
RC-Timer 12x5.5-CF 4 14.8 11.44 169.3 6,189 32.2 1143 40.32 6.75
RC-Timer 13x5.5-CF 4 14.8 14.97 221.6 5,850 30.5 1412 49.81 6.37
RC-Timer 14x5.5-CF 4 14.8 19.53 289.0 5,392 28.1 1633 57.60 5.65
RC-Timer 15x5.5-CF 4 14.8 25.05 370.7 4,891 25.5 1889 66.63 5.10
RC-Timer 16x5.5-CF 4 14.8 27.77 411.0 4,588 23.9 2041 71.99 4.97
 
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 11x4.5-MR 5 18.5 10.68 197.6 7,963 33.9 1316 46.42 6.66
APC 12x4.5-MR 5 18.5 13.88 256.8 7,650 32.6 1651 58.24 6.43
APC 14x5.5-MR 5 18.5 21.81 403.5 6,893 35.9 2366 83.46 5.86
APC 16x5.5-MR 5 18.5 28.89 534.5 6,080 31.7 2850 100.53 5.33
GemFan 12x4-MR-W 5 18.5 12.53 231.8 7,780 29.5 1516 53.47 6.54
GemFan 13x4.5-MR-W 5 18.5 15.60 288.6 7,480 31.9 1812 63.92 6.28
GemFan 14x4.5-MR-W 5 18.5 18.16 336.0 7,208 30.7 2070 73.02 6.16
GemFan 15x4.5-MR-W 5 18.5 19.99 369.8 7,048 30.0 2251 79.40 6.09
GemFan 16x4.5-MR-W 5 18.5 25.48 471.4 6,476 27.6 2656 93.69 5.63
RC-Timer 11x5.5-CF 5 18.5 10.85 200.7 7,949 41.4 1211 42.72 6.03
RC-Timer 12x5.5-CF 5 18.5 16.84 311.5 7,364 38.4 1682 59.33 5.40
RC-Timer 13x5.5-CF 5 18.5 21.84 404.0 6,872 35.8 2031 71.64 5.03
RC-Timer 14x5.5-CF 5 18.5 27.42 507.3 6,235 32.5 2234 78.80 4.40
 
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 6 22.2 11.66 258.9 9,571 40.8 1461 51.53 5.64
APC 11x4.5-MR 6 22.2 14.72 326.8 9,247 39.4 1825 64.37 5.58
APC 12x4.5-MR 6 22.2 18.80 417.4 8,834 37.6 2242 79.08 5.37
APC 14x5.5-MR 6 22.2 28.46 631.8 7,794 40.6 3045 107.41 4.82
GemFan 11x4-MR-W 6 22.2 12.62 280.2 9,473 35.9 1640 57.85 5.85
GemFan 12x4-MR-W 6 22.2 16.68 370.3 9,049 34.3 2072 73.09 5.60
GemFan 13x4.5-MR-W 6 22.2 20.61 457.5 8,631 36.8 2427 85.61 5.30
GemFan 14x4.5-MR-W 6 22.2 24.03 533.5 8,255 35.2 2775 97.88 5.20
GemFan 15x4.5-MR-W 6 22.2 26.35 585.0 7,994 34.1 2984 105.26 5.10
GemFan 16x4.5-MR-W 6 22.2 32.05 711.5 7,235 30.8 3332 117.53 4.68
RC-Timer 10x5.5-CF 6 22.2 9.88 219.3 9,773 50.9 1253 44.20 5.71
RC-Timer 11x5.5-CF 6 22.2 14.98 332.6 9,220 48.0 1684 59.40 5.06
RC-Timer 12x5.5-CF 6 22.2 22.83 506.8 8,408 43.8 2258 79.65 4.46
RC-Timer 13x5.5-CF 6 22.2 28.79 639.1 7,703 40.1 2594 91.50 4.06
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.