Cobra CM-4510/28 420Kv Motor Propeller Data
Magnets Motor Wind Motor Kv No-Load Current Motor Resistance I Max P Max (6S)
14-Pole 28-Turn Delta 420 RPM/Volt Io = 0.67 Amps @ 21v Rm = 0.061 Ohms 40 Amps 900 W
 
Stator Outside Diameter Body Length Total Shaft Length Shaft Diameter Motor Weight
12-Slot 54.9 mm,  2.161 in. 32.8 mm,  1.291 in. 36.3 mm,  1.429 in. 6.00 mm,  0.236 in. 211 gm,   7.44 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 0.49 A 0.55 A 0.61 A 0.67 A 417 RPM/Volt 0.061 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 15.92 294.5 6,511 33.9 2049 72.28 6.96
APC 16x5.5-MR 5 18.5 23.41 433.1 6,049 31.5 2809 99.08 6.49
APC 18x5.5-MR 5 18.5 29.96 554.3 5,670 29.5 3490 123.10 6.30
GemFan 15x4.5-MR 5 18.5 14.67 271.4 6,590 28.1 1943 68.54 7.16
GemFan 16x4.5-MR 5 18.5 19.05 352.4 6,309 26.9 2376 83.81 6.74
RC-Timer 13x5.5-CF 5 18.5 15.99 295.8 6,508 33.9 1786 63.00 6.04
RC-Timer 14x5.5-CF 5 18.5 21.81 403.5 6,143 32.0 2162 76.26 5.36
RC-Timer 15x5.5-CF 5 18.5 29.97 554.4 5,675 29.6 2664 93.97 4.80
RC-Timer 16x5.5-CF 5 18.5 33.96 628.3 5,438 28.3 2975 104.94 4.74
RC-Timer 17x5.5-CF 5 18.5 37.99 702.8 5,214 27.2 3230 113.93 4.60
RC-Timer 18x5.5-CF 5 18.5 44.59 824.9 4,829 25.2 3567 125.82 4.32
 
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 21.50 477.3 7,525 39.2 2788 98.34 5.84
APC 16x5.5-MR 6 22.2 31.29 694.6 6,915 36.0 3749 132.24 5.40
APC 18x5.5-MR 6 22.2 38.76 860.5 6,414 33.4 4468 157.60 5.19
GemFan 15x4.5-MR 6 22.2 19.73 438.0 7,638 32.5 2661 93.86 6.08
GemFan 16x4.5-MR 6 22.2 25.37 563.2 7,276 31.0 3220 113.58 5.72
RC-Timer 12x5.5-CF 6 22.2 16.44 365.0 7,874 41.0 1911 67.41 5.24
RC-Timer 13x5.5-CF 6 22.2 21.90 486.2 7,495 39.0 2417 85.26 4.97
RC-Timer 14x5.5-CF 6 22.2 29.31 650.7 7,021 36.6 2855 100.71 4.39
RC-Timer 15x5.5-CF 6 22.2 39.95 886.9 6,352 33.1 3375 119.05 3.81
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.