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AXI 5330 Power Requirements

Old 12-18-2006, 02:58 PM
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Neo8234
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Default AXI 5330 Power Requirements

Hello,

I am a student leading a UAV project at my university. We are building a custom aircraft body and are estimating the final flying weight at 20lbs. We plan to use a single AXI 5330 to propel the aircraft. I am unsure of the power requirements of this brushless motor.

I know that it can accept up to 10s LiPoly, but I am having a hard time getting a good understanding on how much battery power we need to perform our tasks. Basically the only extremely demanding part of our flight will be takeoff & climb because we will not be performing aerobatic maneuvers. I am looking primarily at using Duralite Flightpower EVO20 7400mah packs ( http://www.duralitebatteries.com/bat...5000-7400.html ). These packs are available in 5s2p and 6s2p configurations at 7400mah. My difficulty is in that we are trying to obtain up to 2 hours of flight time using some combination of these packs.

Do I really need a 10s configuration ( two 5s2p packs in series) or would a 6s2p setup be sufficient? Also, I am not sure how 7400mah will last me in either configuration and I am aware I may need to setup a parallel configuration as well with up to 4 packs total (that would be 2 parallels of 2 5s2p in series). Any thoughts on what I would need to obtain 2 hours of flight time?

Thanks for your help.

-Blake
Old 12-18-2006, 04:44 PM
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ray foley
 
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Default RE: AXI 5330 Power Requirements

Hi Blake:

To obtain a 2 hour flight duration will require a light airframe, large capacity batteries, minimum power during steady state flight and during takeoff and climb. What sort of wing area, airfoil, general planform are we lookin at?

A sort of scale electrified sailplane can tolerate the weight of large batteries and can perform in a climb and glide mode for long periods without resorting to the vagueries of thermal hunting, ridge lift or other weather related phenomonon. How large a plane is allowed by the rules? Could you jettison depleted battery packs and still qualify?

A clean airframe with retractible or jettisonable landing gear will reduce the SS power requirement. A one time retraction no extension spring loaded retract system could be of some benefit if a belly skid were ok. A servo driven or pneumatic retract system is easy and fairly light if you must land on wheels.

Consider the use of total TE camber control for enhanced glide as well as for quick running from sinking air. A plane with a lifting stab allows a more rearward CG and uses all your horizontal surfaces as lift generating areas. A folding Prop will minimize drag during power off times.

If there is an electro geek in your crew then the battery packs could be distributed into the wing structure with power connectors as required.

Must the power for flight come from batteries only or could an IC diesel engine and dc motor be employed as an on board alternator/generator with a smaller buffer battery for launch purposes?
A couple of years ago Maynard Hill flew an r/c and gps guided plane from nova scotia to ireland on 1 gallon of rc diesel fuel with fumes to spare. How creative can you be with power supply?

Good luck fellows

Raymond Foley, Commander

Flying Tigers R/C Club, Toledo Ohio
Old 12-18-2006, 06:07 PM
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Neo8234
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Default RE: AXI 5330 Power Requirements

Hi Ray,
We are required to stick with electric propulsion. Our prototype aircraft design is 10-11ft wingspan and is a trainer-style aircraft. Total of 14-16 sq ft of wing area. It is being designed for belly skid landings in order to eliminate the need for landing gear. Definitely can't jettison any equipment like depleted packs.

We are limiting the weight of our hardware equipment (meaning computers, sensors, and their power systems) to 10lb. Besides that, we will have a custom composite aircraft (graphite CF, Kevlar, Fiberglass), the AXI 5330/18 Motor (1.1lbs), LiPoly packs to power the motor, the motor's ESC, and RC equipment (receiver & its battery). In addition the airframe will probably house some small aluminum or RFI shielded enclosures for each subsystem.

Our initial target flight time was 2 hours, but we are realizing that this may be extremely expensive to accomplish with LiPoly. My problem is that I am not sure exactly what power output I need to keep the thing flying and i'm even less sure about what sort of LiPoly array I need to provide the necessary power. Would 6s LiPoly have sufficient thrust, or does it really need 8-10s? Duration is the next issue.

Thanks for your quick response.

-Blake
Old 12-19-2006, 08:24 AM
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Helijack
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Default RE: AXI 5330 Power Requirements

I do happen to be playing with a scratch build scale model that is a bit smaller than yours using the 5330/18 I doubt seriously if you can obtain 2 hours flight time unless you can come up with 12, 000 mah packs or better....that is a guess. My calculations, using MotoCalc8, are with a prop of a 17x9, two 4s 8000mah 10c packs and best I can see is 28 minutes time. This is also a trainer like, high lift, slow flying aircraft, and I consider that a very long time. My estimated weight is a little more than half of yours. Final prop-ing will give more accurate data.
Old 12-19-2006, 10:43 AM
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ray foley
 
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Default RE: AXI 5330 Power Requirements

Hi Blake:

There are two design philosophies regarding epower. The first is low voltage - high current, the second is high voltage - low current. The first scenario is aimed at high performance, the second scenario is aimed at long duration.

So the higher you go in voltage, the lower will be the current for a given power output. All batteries are charge storage devices which have a specific maximum storage capacity. So the lower the average current for a SS flight regimen the longer will be the flight time. The motors within reason don't care what voltage the battery is when it is being chopped for part throttle operation. So if you can limit the maximum part throttle duty cycle so that you don't overspeed the motor and break things, then you can go higher in voltage for the given capacity of the cells and attain longer flight times.

example: Assume 1 Kilowatt SS power requirement for the airframe, motor, and prop (that is a 20lb plane and 50 watts per lb power loading). If you use 10s lipo and need 30 amps at about 50% duty cycle to maintain best l/d cruise speed, then, if you have 15s lipo you can expect 20 amps at about 33% duty cycle to attain the same average power. Hence your battery lasts 50% longer at that SS flight condition. You will have to limit the maximum percentage duty cycle and hence RPM to whatever is necessary for reasonable takeoff and climb rate but that is pretty easy all in all, and of course never use full power settings.

So if you go to 20s lipo you would need 15 amp average current draw and even lower %duty cycle from the ESC to the motor. Longer flight time results.

There are ESCs which are good for 12s lipos and prototypes which may be available on loan or evaluation from CC with up to 20s capability.

if two hours is the goal, and 20s lipo and 15 amps is the SS average draw, then 30 amphours capacity is required for continuous operation. That is a big battery pack

If the assumed power requirement is higher than really needed, adjust the calculations and capacity accordingly. However a 20 lb plane at 50 watts per pound (1 kwpower) is fairly low power loading. The airplane will take off a hard runway or closely clipped grass (fairway quality) at this loading. Do not expect aerobatics but it will fly in a scale like manner. Use of aileron to rudder coupling will be necessary and watch the bank angle during turns (20* or less initially).

You must absolutely insure that the ESC, motor, and batteries are properly cooled during operation, adequate air inlet and outlets as well as processor type cooling fans may be necessary. Duct work for moving the air is probably necessary.

Interesting project though

ciao -rjf

ps: I have seen a twenty pound electric glider plane maintain SS altitude at a mere 500 watts power. Takeoff power was around 850 watts. It was a fairly long takeoff run. YMMV -r
Old 12-20-2006, 10:45 AM
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Default RE: AXI 5330 Power Requirements

Have you asked the motor manufacturer, Model Motors, about this? They were very helpful to me with technical questions about their products.

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