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Too many motors! - 6/2/2008 5:23:13 PM   
BrentL


 

Posts: 32
Joined: 5/5/2008
From: JohannesburgGauteng, SOUTH AFRICA
Status: offline 		I'm new to electric flight but rapidly getting addicted.

Only problem is, damn, are we spoilt for choice!

Nitro is pretty easy - buy OS. Period.

But electric, well, there are dozens of manufacturers to choose from, ech producing dozens of motors. Then there's the battery. And the esc. And and and.

So, to all of you with experience, please tell me - when looking for the right combination for any given plane, what are the magic numbers to look for? It often seems like the smaller motors are a better option!

Downloaded motorcalc, which is brilliant, but still not really making sense of it all.
       Post #: 1

RE: Too many motors! - 6/6/2008 4:43:47 PM   
whitecrest


 

Posts: 75
Joined: 8/8/2007
From: Orleans, MA, USA
Status: offline 		You're right, there are many choices. To reduce the confusion, I think it helps to focus on the basic function performed by each essential element of the power train: battery, ESC (electronic speed control) and motor-propeller. Though there are many brands and sizes of each of these, they all pretty much perform the same function and have power limits that must not be exceeded. Your power requirements will be dictated by the type of plane you want to fly. Wing area, all-up weight of the plane, and its desired flight characteristics (sedate trainer, 3D, racing, etc.) will all affect the power required. In the end, you will need a definite number of watts to fly the plane you have in mind to the level of performance desired.

Once you have determined your power requirements, you will be better able to select the right motor. Your primary determinant here will be current-handling capacity which is usually provided by the manufacturer. For example, a motor that can pass 10 amps at full throttle without undue overheating can provide about 100 watts using a 3-cell lipo: 10.1 volts (under load) x 10 amps = just over 100 watts. Motors in this class weigh only about 24 - 28 grams which is about 1 oz. If you were using a 2-cell lipo, the maximum power you could derive from this motor would be about 74 watts: 7.4 volts (under load) x 10 amps (motor's rated current). Propeller diameter and pitch are used to vary the load (amp draw). Many planes weighing about 16 - 24 oz can be flown very well with 74 - 100 watts. You can use a motor's weight to roughly estimate its power-handling capacity. Roughly 1 oz of motor weight can safely handle about 100 watts. In the above example, the battery and ESC must be rated for at least 10 amps (motor's maximum rated draw) and ideally a bit more for safety and reliability.

If you focus on the fundamentals, you should have no trouble selecting the right motor from the multitude. You will have no trouble obtaining greater than a 1:1 thrust/weight ratio using a lipo/brushless power system.

I have found the following calculator to be very effective for determining the power requirements of a prospective airframe:

http://flbeagle.rchomepage.com/software/webocalc_0.9.0/webocalc.html

I think you will find the advantages of electric power to be very compelling. Good luck with your future projects!


_____________________________

Some things that count can''t be counted, and some things that can be counted don''t count. << A.E.

(in reply to BrentL)
       Post #: 2

RE: Too many motors! - 7/6/2008 2:20:03 AM   
lilbanchee


 

Posts: 283
Joined: 7/2/2006
From: Chula Vista, CA, USA
Status: offline 		Just for the record, Himax, Castle Creations, Thunder Power, MaxAmps, and Eflite are some of the top companies, although Castle Creations is top of the line for speed controlls.

Hobby City has great products that work great too, so check them out. My favorites from there are zippy lipos, turnigy motors and ESCs, and the towerpro combos, which work suprisingly well for their price.

_____________________________

Life is short, fly more!

(in reply to whitecrest)
       Post #: 3

RE: Too many motors! - 7/11/2008 7:52:46 PM   
Glacier Girl



Posts: 6886
Joined: 7/9/2004
From: SomewhereIn, PA, USA
Status: offline 		Lot's of the plane mfg's are gettinginto the game too, you'll see recomended set ups already listed. EFlite/ Hangar9/Horizon are really on the ball right now. If you know which plane from them, they already have an electric set up for you.

Heck EFlite even went to the point of naming a lot of their motors to a specific scale/ engine class.

You got a 60 scale like their Camel, or P40, use the 60 motor. Something bigger, like say my 120 scale Corsair, you use either the 110 or 160 EFlite motor.
Smaller like the Hangar 9 Cub, the 25 motor is a good set up.

_____________________________

"The Missing Man Formation"
Looking heavenward you cannot help but shed a tear...mornful...lonesome...a hole that screams out almost as loudly as the roar of the engines that pass over head.

(in reply to lilbanchee)
       Post #: 4

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