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Old Mar 30, 2009, 09:59 AM
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UAV Motor

I'm starting to design an UAV for surveilance. It will weight about 8-10 Kg.

I will choose a diesel motor. But I don't know how to choose the motor.

What kind of calculations I need to do to choose the suitable motor?
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Old Mar 30, 2009, 10:30 AM
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Might want to check out the the Fuel sections. try using the search at the top of the page.
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Old Mar 30, 2009, 05:47 PM
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Quote:
Originally Posted by aerodolphin
I'm starting to design an UAV for surveilance. It will weight about 8-10 Kg.

I will choose a diesel motor. But I don't know how to choose the motor.

What kind of calculations I need to do to choose the suitable motor?
Total All Up Weight
Wing Area
Speed Required
Duration Required
Engine Weight
Engine Location
CoG
Prop Clearance
Vibration
Cooling
Cost
Mounting

These are just the things to start with...
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Old Mar 31, 2009, 06:59 AM
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An 8 to 10kg UAV will put you over weight in several countries for simple systems.

Your vehicle will most certainly have to comply with airworthy requirements.

None of this has been set in stone yet though.

But I would try and come in under 7KG for a machine that might have less regualtion, unless you have deep pockets.
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Old Mar 31, 2009, 08:05 AM
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But what equations are behind the Aerodesign Propeller Selector sofware to calculate the thrust from altitude, motor RPM and propeller?

http://www.geistware.com/rcmodeling/...r_selector.htm


Gary thank you for the information. There is any preliminary document about it?

I will check if I can design an UAV under 7 Kg. I think yes. My payload will be 1,5 Kg maximum.
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Last edited by aerodolphin; Mar 31, 2009 at 08:13 AM.
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Old Mar 31, 2009, 08:48 AM
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What diesel power plants have you seen in this size range? I think the smallest is the Cosworth diesel, but it's 5HP.

Greg
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Old Mar 31, 2009, 10:43 AM
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What duration are you looking for? A 2-stroke gasoline motor could easily get you 8 hours duration, is that enough?

Steve
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Old Mar 31, 2009, 11:13 AM
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I will need a 2-6 hours range.

I found this Diesel engines:

http://www.evolutionengines.com/Gas/Default.aspx

I don't know if the 40GX it's good for my application, of I need a more power one.


But, about the maximum 7Kg. It's writted somewhere this value? And what will me the maximum altitude allowed?
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Old Mar 31, 2009, 01:25 PM
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Oh, those are spark ignition gasoline engines. That will work too.

Greg
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Old Mar 31, 2009, 03:42 PM
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Have you considered the saito fg-36?

Or even the roto 35 FS:
http://www.rotomotor.cz/rotomotor/en/roto-35-fs.html
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Old Mar 31, 2009, 03:58 PM
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Check out Davies diesel head conversions,
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Old Mar 31, 2009, 07:56 PM
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2-6 hours is trivial to achieve with a reliable gas engine. Get a Zenoah G-26 and 2Kg fuel should be plenty for that duration on a reasonable airframe. Don't bother with any model airplane engines, they aren't reliable enough for serious UAV work. You don't need a diesel or a 4-stroke either.

Steve
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Old Apr 04, 2009, 06:41 AM
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Joined Feb 2009
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Quote:
Originally Posted by aerodolphin
What kind of calculations I need to do to choose the suitable motor?
If you want to do it properly you need to use something like this to get somewhat accurate performance data of your propeller, then when you've set your cruise speed (and know how much thrust you need based on the drag of the airframe) you can work out the optimal RPM and torque required to run it. Based on that select an engine which fits your size requirements and run at optimal efficiency at those speeds.

... and that's how you get the best endurance. It's a bit of a pain to do though

I have done propeller performance calculations before, might be able to whip up a Matlab script that can do it in the next few days if you want (no promises tho!).
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