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Apr 13, 2006, 07:03 AM
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I am new..and I have to say...this is usefull stuff..great
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Apr 15, 2006, 03:40 AM
Ut Aquilae Volent
CAFB 04-12's Avatar
Could you add LVC (low voltage cutoff) and DVM (digital voltmeter) to your list of acronymn and descriptions. It took me some investigation to find out what those mean!

Chad
Apr 25, 2006, 12:37 AM
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dev|ant's Avatar
Request: kV? I'm pretty sure it ain't kilo-volts.
Apr 25, 2006, 12:40 AM
Registered User
RPM (in K's or thousands) per volt. Measure of electric motor output.
Apr 25, 2006, 05:41 PM
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dev|ant's Avatar
Got it, thanks rutat!
May 04, 2006, 06:28 PM
Registered User

Beginner asking questions


Thanks guys. I'm an old hand at glider guiding, but I'm really interested in learning about the electric power thing.
Not only do I have a "new" Airtronics Legend on the building board, but I'm scratch building a Ben Buckle Double Diamond.
My question is, it calls for an .049 motor. How do you determine what "electric" motor to use, how big of a battery pack is needed, and will the new battery packs run the motor and the reciever at the same time or do you need different packs.
Thanks in advance for not making fun of me.
SkipinHouston
May 20, 2006, 02:42 AM
Registered User
saucerguy's Avatar

Awesome


This is just a must see page for all new flyers before delving into this field, even if they have to use it as a cheat sheet "printed out", it adds a whole new dimension of understaing all of this stuff.

Keep up the good work!!!!!!!!
May 20, 2006, 06:48 AM
Proud member of LISF and ESL

Watts Per Pound = How to size electric systems


Quote:
Originally Posted by skipinhouston
Thanks guys. I'm an old hand at glider guiding, but I'm really interested in learning about the electric power thing.
Not only do I have a "new" Airtronics Legend on the building board, but I'm scratch building a Ben Buckle Double Diamond.
My question is, it calls for an .049 motor. How do you determine what "electric" motor to use, how big of a battery pack is needed, and will the new battery packs run the motor and the reciever at the same time or do you need different packs.
Thanks in advance for not making fun of me.
SkipinHouston
I have a Legend myself. Bought it used. Needs a lot of aligning so it doesn't fly very well right now.

New expression if not in the dictionary already - Watts per pound

Best approach for sizing an electric motor to a model is to use input watts per pound. This is comparable to horsepower in IC engines. 748 watts = 1 horsepower. Watts = Volts X Amps

So a speed 400 motor on 8 volts that draws 9 amps = 72 watts. Put that in a 1 pound plane and you have 72 watts/pound.

50 watts per pound = scale flight, ROG but not a lot of aerobatics A full scale Piper Cub's stock engine would be about 45 watts per pound. Good target for slow flyers if you want to keep things very light.

75 watts per pound = mild to moderate aerobatics - If you are used to glow systems, I would use this as your minimum target

100 watts per pound = agressive aerobatics - pattern planes, pylon racers, etc.

150 watts per pound = 3D flight
- hang it on the propeller.

If you use these with brushed motors, like a speed 400, speed 500, speed 600, 05, etc, you will get this kind of results. If you use a brushless motor you get about 30-50% better results as brushless motors are more efficent. They deliver more of the watts to the propeller and less gets lost to heat.

Give me the projected all up weight of the model you are building, the wing span and the type of flight behavior you want and I will point you based on these watt/pound ratios.

Very Very loosly, a speed 600 motor is similar in power to a .049 motor.

A 500 watt brushless motor, about 2/3 horsepower, would be roughly comparable to a .40 glow motor.

These are VERY VERY loose approximations as the electric motors have much wider use envelopes, can be inrunner or out runner and can have gear boxes. In addition, the battery is more than just a fuel tank, it can act like a supercharger, so the battery and motor are absolutely linked when you size an electric power system. You can change the behavior of a given motor based on the battery used.

These are things that glow motors don't use and so are not a factor. This makes electric systems more complex to figure, but far more flexible in application. So it is best to use watts per pound rather than trying to do glow motor size to some specific electric motor.

I hope that made sense.
Last edited by aeajr; May 20, 2006 at 06:54 AM.
May 25, 2006, 08:15 AM
Make 'n Break!!
roosevelt's Avatar
BTW? what's this mean?

AUW= All up weight. The flying weight of the plane with battery and everything.
May 28, 2006, 01:53 AM
Registered User
I'm going to hazard a guess BTW means by the way, but I could be wrong..
Jun 09, 2006, 10:22 AM
Ace of glue
Langenase's Avatar
If you want to go up, pull back on the stick.
If you want to go down, pull back a little more.
If you want to go down real fast and spin around and around and around, just keep pulling back.
--- Modificated aviation proverb (stick for "yoke").
Jul 24, 2006, 11:14 PM
Registered User
newflyermx's Avatar

Motor Calculation Program


Quote:
Originally Posted by skipinhouston
Thanks guys. I'm an old hand at glider guiding, but I'm really interested in learning about the electric power thing.
Not only do I have a "new" Airtronics Legend on the building board, but I'm scratch building a Ben Buckle Double Diamond.
My question is, it calls for an .049 motor. How do you determine what "electric" motor to use, how big of a battery pack is needed, and will the new battery packs run the motor and the reciever at the same time or do you need different packs.
Thanks in advance for not making fun of me.
SkipinHouston
Hi Skipinhouston:
I'm realy new at this but a find a page from Multiplex USA that may help you.
http://brantuas.com/ezcalc/multiplexcalc.asp
There you might will find any calculation you need for a proper setup.
Hope this will help.
AA @ Mexico
Aug 01, 2006, 06:09 PM
Registered User
So what does flying WOT mean?
Aug 01, 2006, 06:37 PM
Registered User
WOT - Wide Open Throttle

Ha! and I don't even fly RC! I do fly flight sim and race with LFS though.
Aug 01, 2006, 07:36 PM
Registered User
Thanks Mrodgers apprecaite it