Cobra CM-3515/34 385Kv Motor Propeller Data
Magnets Motor Wind Motor Kv No-Load Current Motor Resistance I Max P Max (6S)
14-Pole 34-Turn Delta 385 RPM/Volt Io = 0.38 Amps @ 15v Rm = 0.133 Ohms 24 Amps 530 W
 
Stator Outside Diameter Body Length Total Shaft Length Shaft Diameter Motor Weight
12-Slot 43.0 mm,  1.693 in. 47.0 mm,  1.850 in. 50.6 mm,  1.992 in. 5.00 mm,  0.197 in. 195 gm,   6.88 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 0.35 A 0.38 A 0.41 A 0.44 A 374 RPM/Volt @ 15V 0.133 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 16x5.5-MR 5 18.5 10.75 198.9 5,632 29.3 1553 54.78 7.81
APC 16x5.5-MR 5 18.5 15.25 282.1 5,192 27.0 2064 72.80 7.32
APC 18x5.5-MR 5 18.5 19.24 355.9 4,788 24.9 2459 86.74 6.91
GemFan 15x4.5-MR-W 5 18.5 9.88 182.8 5,724 24.4 1454 51.29 7.95
GemFan 16x4.5-MR-W 5 18.5 13.30 246.1 5,373 22.9 1843 65.01 7.49
RC-Timer 13x5.5-CF 5 18.5 10.35 191.5 5,683 29.6 1318 46.49 6.88
RC-Timer 14x5.5-CF 5 18.5 14.02 259.4 5,317 27.7 1603 56.54 6.18
RC-Timer 15x5.5-CF 5 18.5 18.66 345.2 4,865 25.3 1917 67.62 5.55
RC-Timer 16x5.5-CF 5 18.5 20.97 387.9 4,616 24.0 2086 73.58 5.38
RC-Timer 17x5.5-CF 5 18.5 22.99 425.3 4,383 22.8 2199 77.57 5.17
RC-Timer 18x5.5-CF 5 18.5 26.21 484.9 3,996 20.8 2370 83.60 4.89
 
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 6 22.2 8.80 195.4 7,096 30.2 1392 49.10 7.13
APC 14x5.5-MR 6 22.2 14.13 313.7 6,504 33.9 2082 73.44 6.64
APC 16x5.5-MR 6 22.2 19.94 442.7 5,861 30.5 2702 95.31 6.10
APC 18x5.5-MR 6 22.2 24.53 544.6 5,323 27.7 3101 109.38 5.69
GemFan 13x4.5-MR-W 6 22.2 10.14 225.1 6,933 29.5 1580 55.73 7.02
GemFan 14x4.5-MR-W 6 22.2 11.93 264.8 6,744 28.7 1847 65.15 6.97
GemFan 15x4.5-MR-W 6 22.2 13.03 289.3 6,615 28.2 1977 69.74 6.83
GemFan 16x4.5-MR-W 6 22.2 17.28 383.6 6,138 26.2 2423 85.47 6.32
RC-Timer 12x5.5-CF 6 22.2 10.70 237.5 6,878 35.8 1459 51.46 6.14
RC-Timer 13x5.5-CF 6 22.2 14.22 315.7 6,490 33.8 1811 63.88 5.74
RC-Timer 14x5.5-CF 6 22.2 18.70 415.1 6,026 31.4 2117 74.67 5.10
RC-Timer 15x5.5-CF 6 22.2 24.45 542.8 5,394 28.1 2379 83.92 4.38
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.