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Mar 30, 2009, 09:59 AM
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Discussion

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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Mar 30, 2009, 10:30 AM
Registered User
mecevans's Avatar
Might want to check out the the Fuel sections. try using the search at the top of the page.
Mar 30, 2009, 05:47 PM
MINE!
Mick Molloy's Avatar
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...
Mar 31, 2009, 06:59 AM
Gaftopher
Gary Mortimer's Avatar
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.
Mar 31, 2009, 08:05 AM
Registered User
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.
Last edited by aerodolphin; Mar 31, 2009 at 08:13 AM.
Mar 31, 2009, 08:48 AM
Dieselized User
gkamysz's Avatar
What diesel power plants have you seen in this size range? I think the smallest is the Cosworth diesel, but it's 5HP.

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

Steve
Mar 31, 2009, 11:13 AM
Registered User
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?
Mar 31, 2009, 01:25 PM
Dieselized User
gkamysz's Avatar
Oh, those are spark ignition gasoline engines. That will work too.

Greg
Mar 31, 2009, 03:42 PM
Nemo in a blender
Connexxion's Avatar
Have you considered the saito fg-36?

Or even the roto 35 FS:
http://www.rotomotor.cz/rotomotor/en/roto-35-fs.html
Mar 31, 2009, 03:58 PM
Registered User
Airboatflyingshp's Avatar
Check out Davies diesel head conversions,
Mar 31, 2009, 07:56 PM
Registered User
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
Apr 04, 2009, 06:41 AM
Registered User
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!).