DESIGN: Electrotor-Simplex ~ Power Train - Motor - Cooling

• Plettenberg page ~ Added Options for Predator
• A thought re the cooling of the motor when used on a high-speed competition airplane. The cone on the propeller hub has a relatively small opening for the cooling air. Perhaps the advantages of this are; 1/ The airspeed is probably 150 mph and this is well above what is need for cooling. 2/ the air may expand inside the cone (and slow down) and thereby have its temperature reduced just before it enters the motor.

• Pressure Change Cooling:
• The expansion or contraction of a gas under pressure is adiabatic, meaning that there is a temperature change associated with the volume change. For an ideal gas, this relationship is expressed in the equation PV=nRT. By performing mechanical work on a gas to change its volume, the temperature can be forced to change as well. Information on the Ideal Gas Law algorithm above
• The Proposed Method:
• The flight time of current batteries will be about 15 minutes. Therefore, why not install a strong lightweight filament-wound bottle of pressurized air near the motor. This bottle has been pressurized previous to the flight and the increased temperature due to compression has dissipated. During flight this compressed air is released into the motor where it expands and cools the surrounding motor-coils etc.
• There is also the ability to refrigerate the carbon wound cylinders and then insolate the cylinders when using them.
• This idea assumes that a large temperature differential between that of expanded air and ambient air will proved equal or better cooling than will higher velocity ambient air. This idea also assumes that the 15-minute tank of air plus valve will have a weight penalty comperable to that of the replaced fan plus the power consumed in driving the fan.
• For Principal Assembly 1574 The cold air could enter the bottom of the engine. Then the structural members above the motor close off much of the exiting air so that it is in contact longer with the motor until it approches the ambient temperature. Perhaps the air could then be exhausted into the vanes of the planetary reducer.
• At some point in time do some rough calculations re the above.
• From Rick; While the "concept" sounds good, when doing final testing on the product , the annoyance of having to deal with a finite amount of compressed air every time a flight test is done whereas a small blower installed to cool the motor continuously and at any time I believe outweighs the "possibility" of bottled air doing the job. Remember after a flight there is residual heat left in the motor winding and steel that needs to be dissipated. A small fan does this admirably and with nominal power requirements in all circumstances. Remember you have to spend a lot of time "designing" the apparatus, finding the right release valves and/or nozzles, build a shroud to contain the spent air into the motor, provide some kind of control from the cockpit, buy a compressor, carbon fibre bottle, etc. I think it gets way more complicated and not as efficacious as an off the shelf fan and blower.
• By Self: Both the electric batteries and the tank of air must be charged up before flight. Perhaps the question is; Is the weight of the composite tank, the average weight of its depleting content, plus tubing and valves etc. more or less than the weight of; the fan, additional batteries and controls etc.

• Pressure Change Cooling: There could be a stack of 3 fans. This fan assemblage would be part radial and part axial. The inner fan rotates with the motor output. The next 'fan' consists of vanes in the frame, which are stationary. The outer 'fan' consists of vanes in the mast, which rotate with the mast.
• Fan Cooling:

• Pascal has suggested liquid nitrogen vaporized within the motor.

For Cooling Idea: See; UniCopter ~ Synchronizing Gears Rootes blower type of concept.

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