|Apr 15, 2006, 04:40 AM|
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!
|May 04, 2006, 07:28 PM|
Joined Aug 2005
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.
|May 20, 2006, 03:42 AM|
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, 07:48 AM|
LI, New York, USA
Joined Mar 2003
Watts Per Pound = How to size electric systems
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.
|Jun 09, 2006, 11:22 AM|
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 25, 2006, 12:14 AM|
Motor Calculation Program
I'm realy new at this but a find a page from Multiplex USA that may help you.
There you might will find any calculation you need for a proper setup.
Hope this will help.
AA @ Mexico