View Full Version : Inrunner or outrunner motors

06-28-2007, 04:34 AM
I am in the learning process and I'd like to know the difference and the advantage or disadvantage of an in runner and out runner. Any and all detail will be appreciated, so I can situate myself properly about this technology.

Thanks Jean??<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p></o:p>

Sky Sharkster
06-28-2007, 12:35 PM
Hello Jean, Welcome to Wattflyer!
here's a good explanation of the basics of brushed, brushless, inrunner and outrunner motors from gobrushless.com;
The outrunners, because of the torque generated by the rotating outer case, can turn a large-diameter prop without using a gearbox ("direct Drive"). Therefore they are used on slower models that require a lot of thrust, like aerobatic and 3D models. Their drawbacks are; Limited prop selection, large outside diameter may not fit inside some cowls and slightly lower efficiency than geared inrunners.
Geared inrunners allow the motor to run close to its optimum motor speed/efficiency while turning a large-diameter prop (reduction gearing), and by varying the gear ratio a large number of prop sizes can be used. Their disadvantages are; Gear drive noise, somewhat heavier than outrunners, more maintainence, longer/bulkier than direct drive.
Direct-Drive inrunners have a limited number of uses; Since they won't swing a large-diameter prop they are best for high-speed models like Pylon Racers or Ducted Fans. They are generally not very efficient so high-discharge capacity batteries are required.
Both types of motors have their supporters and motor choice is also dependent on the size/voltage of the battery used, the type of model, expected flight performance, size of the motor compartment, etc.
Here's an older link that explains KV, speed controllers and motor basics;
hope this helps!

06-28-2007, 03:54 PM
Thanks Ron this does help a lot
Thanks again

06-28-2007, 11:59 PM
Today I was looking at the web site you sugested and man this site is what the doctor ordered. Even if I was not an electrician I think I could undersatnd this.
Thanks again

07-02-2007, 11:09 PM
Brushless motor animations and simulations:

Excellent motor building articles by Brian Mulder, a must read, will prevent you from asking a lot of questions you even did not know you were going to ask ;) ;) Inrunners our outrunners, from an electric point of view there's no difference, they look the same to the controller:
-> Articles by SouthEasterners.
-> Electric Motors - part 1-5

Do-it-yourself motor homepages, manuals/tutorials, checks and tests in this motor builders tips and tricks thread. The checks and tests may save you from frying your controller or motor. Thread is active, bookmark it for future reference and subscribe to it:
http://www.rcgroups.com/forums/showthread.php?t=240993 (sticky thread, at top of subforum)

Vriendelijke groeten ;) Ron
near Nijmegen, the Netherlands