flyingcrowe

I am new to electrics and would like to know how to determine what electric motor is best for a plane.
I was looking at a brushless set up from Great Planes. It comes with a 35-30-950 motor but I have no idea what size plane it can handle.
This motor says it can swing a 10x4 or 12x5 prop. Am I to assume it would fly a smaller .40 size plane? I know weight is an issue also.
Is there a formula or key to comparing Electrics to Glow as far as power goes? What do the numbers stand for in a motor "35-30-950"?
Sure wish they just said something like "comparable to a .25 or .40 glow engine".
Any help here would be appreciated very much.


Here is the info on the system I was looking at:
FEATURES: Contains ESC, Brushless motor and LiPo battery in one package for
400 size Park Flyer applications

INCLUDES: Silver Series 35A Brushless Electronic Speed Control (GPMM1830)
35-30-950 Brushless Outrunner Electric Motor (GPMG4590)
LiPo 1500mAh 11.1V 15C Battery Pack w/Balance Connector (GPMP0717)

mrasmm

you can figure out their HP by finding the watts. To do that you take nominal voltage times max cont amps and then you get a number, and that is how many watts the motor has. Then you take that number and divide it by 746, the number of watts in 1hp, and that will give you how many HP the motor has. You should be able to compare this to nitro pretty easily. If you want to get more complicated you can also times that number by the efficiency.

So for example say your motor draws a max of 28A cont on a 3s lipo and has a 74% efficiency

28 * 11.1 * 0.74 / 746 = 0.308 HP

maybe that way will work for ya =)

flyingcrowe

OK, Then if I understand this correctly the 35-30-950 would come out like this:

35 X 11.1 X .74 =287 Divided by 746 would be .385 HP ???

Fliprob17

You will not get 35 amps on a continuous basis from that motor. It is spec'd at 20 amps continuous and 28 amps on a 15 second burst.

Everything in electric is based on total watts, and watts per pound of aircraft. Seriously, I think it is easier to just forget about what size glow engine was in the plane, and just work with the flying weight. It seems to just get more confusing

Total watts = battery voltage x motor amp draw. You then take that total watt number, and divide by the weight (in pounds) of the aircraft to get watts per pound. For Trainer planes you will need 70-90 watts per pound - for aerobatic/sport you will need 110-130 watts per pound - for 3D you will need 150+ watts per pound.

Do you have an aircraft weight, or something in mind?

flyingcrowe

I basically want a park flyer that has 4 channels, capable of 3D even if I am not (hehe). I am thinking of just a 34-36" WS Foamie profile. I would also like to buy/build a smaller trainer, maybe 46" WS for teaching other guys out here on the road. I am an over-the-road trucker and haul my nitro planes with me. The proplem is getting to flying fields with a semi. I know where several are but don't always have time to drive out to them. With an electric or two I could go behind the truckstop and run down a battery or two and then get back truckin'. The only issue is LIPO batteries, I'll have to build a little vault for them so they don't get damaged. I have seen what can happen to them if hit too hard.