Hello Everybody,
I am currently using Plettenberg 15-22 with centrifugal fan and MVVS 8.0 with centrifugal fan in my Big Red.
Plettenberg 15-22 fan is an option but the MVVS 8.0 fan comes always with the motor.
Plettenberg 15-22 with fan and 2" long leads with EC3 connectors, weights 193 grams (6.78 oz.).
MVVS 8.0 with 2" long leads with EC3 connectors, weights 229 grams (8.08 oz.).
The Plettenberg centrifugal fan weights 12 grams (0.42 oz.). By the way: this fan and shaft constitute one assembly and to remove the fan, one must replace the shaft.
In central Poland, where I live right now, the ambient air temperature reaches frequently 32-34 deg. C (~90 deg.F.) in the shaded areas, in the early afternoons. When I was using MVVS 8.0 running Igor's 12x5x3 carbon composite, narrow blade, prop. on 6S ThunderPower batteries, the temperature of the rotor after full pattern was 53-55 deg.C. I have used the infrared measuring device, measured this temperature many times and then averaged the results. MVVS 8.0 rotor surface is dull black, therefore the emissivity of it is probably close to 0.9. For those who want to understand better the infrared measurements, please go to
https://en.wikipedia.org/wiki/Emissivity or/and any of the websites regarding black body radiation.
Some time ago, I have asked the Plettenberg factory to remove the fan from one of my motors. The weight of Pletty 15-22 without fan was 181 grams. This motor went into my Big Red and I started flying 48 grams (1.7 oz.) lighter model in hot weather. The temperature of the motor, about 15-20 seconds after landing, reached 73 deg.C. Because the Pletty's rotor has shiny and smooth surface having low emissivity, I have measured the temperature on the black, aluminum back plate with four ventilation holes. This plate has the emissivity close to the MVVS 8.0 surface emmisivity, therefore I feel the temperature measurements of both motors are reasonably comparable.
Plettenberg Engineering says that 80 degrees C. on the windings represents the maximum safe temperature, therefore 73 deg. C on the back plate that is directly exposed to the hot air passing the windings and is located about 0.10 " from the windings, was dangerously close to this limit.
Please remember that I was flying in hot weather and full sun. The air flow in the Big Red's motor and battery compartment seems to be sufficient, with the ESC suspended directly in the flow and very large inlets. By the way, I have enlarged the size of the fuselage front portion w/r to the original Igor's Max Bee II to have more air flow and more cooling. The ESC (Spin66) was not even warm to touch after full pattern flights with MVVS 8.0 and Pletty. The MEASURE option available via JETI BOX showed maximum ESC temperature in flight = 45 degrees C. This was the temperature measured by the sensor inside ESC and was of course higher than the ESC surface "touch" temperature. Simply put: no problem with the ESC overheating for both motors.
Then, I have installed Plettenberg 15-22 with the centrifugal fan using the same prop. and battery and flew five patterns in hot weather.
The temperature of the Pletty's fan surface (that is dull black aluminum) was in 52-53 deg. C range and this means that the Plettenberg fan is very effective. Aluminum is very conductive and, because this fan is very close to the windings and is exposed to the hot air flow coming directly from the motor inside, the temperature of the windings was perhaps 3-5 deg. C higher.
Conclusion: MVVS 8.0 and Plettenberg 15-22 centrifugal fans are very effective in lowering the temperature of these motors and must be used in hot weather. The RTF weight of the model, lap times, length of lines, Target Throttle, Max.Throttle and the active timer Sensitivity parameter affect the temperature of motors but,
when all these parameters are set like in case of Big Red, centrifugal fans will provide lower (and acceptable) temperatures of the windings after the C/L Pattern in hot weather.
Only centrifugal fans are effective. The axial fans will not be effective enough.
I can explain why but it will take another half a page. If anybody is interested, please send me the PM.
Happy (hot weather) flying and do not forget your own sun and heat protection,
Best Regards,
M
Topic: Motors cooling (Read 700 times)
