Cobra C-5330-18 250Kv Motor Propeller Data
Magnets Motor Wind Motor Kv No-Load Current Motor Resistance I Max P Max (12S)
14-Pole 18-Turn Delta 250 RPM/Volt Io = 2.13 Amps @ 20v Rm =  0.024 Ohms 70 Amps 3110 W
 
Stator Outside Diameter Body Length Total Shaft Length Shaft Diameter Motor Weight
12-Slot  63.0 mm,  2.48 in. 60.5 mm,  2.38 in. 94.3 mm,  3.71 in. 8.00 mm,  0.315 in. 649 grams, 22.89 oz.
 
Test Data From Input 16.0 V 20.0 V 24.0V 28.0V Measured Kv value Measured Rm Value
Sample Motor Io Value 1.946A 2.128 A 2.306 A 2.517 A 255.4 RPM/Volt @ 20V 0.0239 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 17x12-E 6 22.2 28.88 641.05 4,991 56.7 3,134 110.6 4.89
APC 18x10-E 6 22.2 26.75 593.76 5,193 49.2 3,605 127.2 6.07
APC 18x12-E 6 22.2 37.00 821.40 4,985 56.6 3,512 123.9 4.28
APC 19x8-E 6 22.2 28.14 624.64 5,044 38.2 3,885 137.0 6.22
APC 19x10-E 6 22.2 29.99 665.82 5,129 48.6 4,033 142.3 6.06
APC 19x12-E 6 22.2 33.62 746.34 4,950 56.3 4,258 150.2 5.71
APC 20x8-E 6 22.2 31.59 701.32 5,100 38.6 4,446 156.8 6.34
APC 20x10-E 6 22.2 37.50 832.59 5,006 47.4 4,859 171.4 5.84
APC 20x11-E 6 22.2 37.66 836.01 4,891 50.9 4,775 168.4 5.71
APC 20x13-E 6 22.2 42.60 945.81 4,919 60.6 5,071 178.9 5.36
APC 20x15-E 6 22.2 50.47 1120.37 4,680 66.5 4,572 161.3 4.08
APC 21x12W-E 6 22.2 50.29 1116.48 4,791 54.4 5,968 210.5 5.35
APC 21x14-E 6 22.2 48.19 1069.73 4,831 64.0 5,782 204.0 5.41
APC 22x10-E 6 22.2 48.15 1068.97 4,834 45.8 6,100 215.2 5.71
APC 22x12-E 6 22.2 57.85 1284.18 4,694 53.3 6,560 231.4 5.11
APC 24x12-E 6 22.2 70.17 1557.73 4,398 50.0 7,838 276.5 5.03
 
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 15x10-E 8 29.6 28.93 856.42 6,723 63.7 3,616 127.5 4.22
APC 16x8-E 8 29.6 31.73 939.09 6,702 50.8 4,276 150.8 4.55
APC 16x10-E 8 29.6 34.71 1027.50 6,671 63.2 4,397 155.1 4.28
APC 16x12-E 8 29.6 43.17 1277.86 6,515 74.0 3,997 141.0 3.13
APC 17x8-E 8 29.6 34.27 1014.30 6,685 50.6 4,836 170.6 4.77
APC 17x10-E 8 29.6 42.03 1244.03 6,552 62.0 5,160 182.0 4.15
APC 17x12-E 8 29.6 47.95 1419.35 6,217 70.6 4,994 176.2 3.52
APC 18x8-E 8 29.6 34.65 1025.73 6,565 49.7 5,347 188.6 5.21
APC 18x10-E 8 29.6 42.74 1265.22 6,497 61.5 5,912 208.5 4.67
APC 18x12-E 8 29.6 60.75 1798.17 6,128 69.6 5,726 202.0 3.18
APC 19x8-E 8 29.6 48.06 1422.46 6,373 48.3 6,454 227.7 4.54
APC 19x10-E 8 29.6 46.82 1385.90 6,400 60.6 6,577 232.0 4.75
APC 19x12-E 8 29.6 57.43 1700.02 6,355 72.2 7,093 250.2 4.17
APC 20x8-E 8 29.6 51.95 1537.84 6,452 48.9 7,384 260.5 4.80
APC 20x10-E 8 29.6 61.03 1806.61 6,304 59.7 7,888 278.3 4.37
APC 20x11-E 8 29.6 61.96 1833.90 6,139 63.9 7,580 267.4 4.13
APC 20x13-E 8 29.6 66.82 1977.87 6,067 74.7 7,871 277.6 3.98
APC 20x15-E 8 29.6 79.16 2343.25 5,772 54.7 7,096 250.3 3.03
 
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 15x8-E 10 37.0 29.91 1106.7 7,875 59.7 4,557 160.76 4.12
APC 15x10-E 10 37.0 46.91 1735.8 7,366 69.8 5,099 179.86 2.94
APC 16x7-E 10 37.0 35.52 1314.3 7,838 52.0 5,769 203.49 4.39
APC 16x8-E 10 37.0 51.85 1918.5 7,295 55.3 5,968 210.50 3.11
APC 16x10-E 10 37.0 56.20 2079.5 7,257 68.7 6,046 213.28 2.91
APC 16x12-E 10 37.0 65.23 2413.6 7,190 81.7 5,649 199.27 2.34
APC 17x7-E 10 37.0 39.88 1475.4 7,838 52.0 5,769 203.49 3.91
APC 17x8-E 10 37.0 54.16 2003.9 7,902 59.9 6,917 244.00 3.45
APC 17x10-E 10 37.0 65.45 2421.8 7,680 72.7 7,336 258.76 3.03
APC 17x12-E 10 37.0 72.77 2692.3 7,294 82.9 6,943 244.90 2.58
APC 18x8-E 10 37.0 53.01 1961.4 7,997 60.6 8,016 282.76 4.09
APC 18x10-E 10 37.0 60.51 2238.8 7,737 73.3 7,737 272.91 3.46
APC 18x12-E 10 37.0 86.01 3182.3 7,298 82.9 7,494 264.34 2.35
APC 19x8-E 10 37.0 79.86 2955.0 7,632 57.8 9,445 333.16 3.20
 
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 15x6-E 12 44.4 40.66 1805.2 9,284 52.8 6,125 216.06 3.39
APC 15x7-E 12 44.4 36.14 1604.8 9,367 62.1 6,156 217.15 3.84
APC 15x8-E 12 44.4 40.85 1813.7 9,069 68.7 5,910 208.46 3.26
APC 15x10-E 12 44.4 67.48 2996.0 8,657 82.0 6,387 225.29 2.13
APC 16x7-E 12 44.4 54.56 2422.6 8,969 59.5 7,908 278.94 3.26
APC 16x8-E 12 44.4 75.73 3362.5 8,256 62.5 7,901 278.70 2.35
APC 16x10-E 12 44.4 80.98 3595.6 8,025 76.0 7,895 278.50 2.20
APC 17x7-E 12 44.4 56.20 2495.1 9,486 62.9 8,893 313.69 3.56
APC 17x8-E 12 44.4 76.65 3403.2 9,110 69.0 9,018 318.08 2.65
APC 18x8-E 12 44.4 74.20 3294.4 9,140 69.2 10,801 380.99 3.28
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
584 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.