- What is the advantage between an inrunner and outrunner brushless motor in a model aircraft?
An inrunner motor has stationary coils which surround the rotating magnet at the center.
An outrunner motor has stationary coils at the center, and the rotating magnet on the outside.
Outrunner motors generally have lower Kv ratings, meaning they run at a lower speed, but with more torque, which would allow you to direct drive larger props without needing a gearbox. Most RC cars and boats would require an inrunner brushless motor.
- How many RPM does a r/c helicopter motor do?
Check out on the web, you may find a kit is better than designing your own. And a lot of the r/c helicopters used professionally for photography (including all of mine) are electric due to less noise, no smoke, and far fewer vibrations.
The lifting range you are looking at (1 to 3lbs) would be well sited for an Align Trex 600.
- If i have to make the rc helicopter,what is the rating of the motor used in it ?
Go to library and read up on it.
Buy a kit and put it together and fly it, learn from it, then build your own with the improvements that you see fit.