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MidwestFlyer
11-13-2005, 02:44 AM
New to electric flight. I see references to inrunner and outrunner motors, both for the same aircraft.

What is the difference between these two types of motors?

Dr Kiwi
11-13-2005, 03:32 PM
Briefly:

Inrunners have a rotating, wire wound, armature spinning within a magnet-lined can.

Outrunners have a rotating magnet-lined bell, spinning around a wire-wound fixed stator.

Generally inrunners are high Kv (ex. 3200-5600Kv) designed for high rpm (50,000rpm) - they can be used in direct drive with small props, but are often geared to drive bigger props.

Generally outrunners are much lower Kv (ex. 800-1500Kv) and higher torque (in part because of the larger rotating mass of magnets and bell), and so can be used as direct drive with large props. Some higher Kv outrunners can be geared.

Cheers, Phil

ron_van_sommeren
11-13-2005, 03:35 PM
See
http://www.yahoogroups.com/group/lrk-torquemax

A list of outrunner manufacturers (kit manufacturers too):
http://www.rclineforum.de/forum/thread.php?threadid=43664&sid=

A very very simplified inrunner animation on this page:
http://www.speedy-bl.com/electr.htm

A very simplified lrk outrunner animation
http://www.torcman.de/peterslrk/LRK_in_action.gif

Two better inrunner animations, the controller uses sensors but that makes no difference to the motor itself. You can step through the sequence or maximise your window to get the speed down:
http://www.servomag.com/flash/2-pole/2pole-bldc-motor.html
http://www.servomag.com/flash/4-pole/smi-motor007.htm

CD-rom outrunner motor computer simulation
http://www.meinpapi.de/dieter/JAMO_0-33Wi10Abig.gif
http://www.meinpapi.de/dieter/JAMO_0-33Wi10Asmall.gif (smaller version)
The cd-rom motor simulation was done with a free simulation program:
http://femm.foster-miller.net

A beautiful LRK outrunner computer simulation, different colours for different magnetic field strength
http://www.mfly.de/animation_b.gif

Waveforms and signals in a brushless controller:
http://www.torcman.de/peterslrk/SPEEDY-BL_eng.html#Anker1591256

ron_van_sommeren
11-13-2005, 03:36 PM
@Dr.Kiwi/Phil
It's not the mass that produces torque, it's the greater distance between the magnets and the shafts that's responsible for more torque.

Dr Kiwi
11-14-2005, 06:53 PM
@Dr.Kiwi/Phil
It's not the mass that produces torque, it's the greater distance between the magnets and the shafts that's responsible for more torque.

Sorry, Ron - I knew about the moment arm from High Shool Physics in the '60's, but forgot to mention it. I would have thought mass would be greater too, and that allied with the longer moment arm, produces the increased torque.

Matt Kirsch
11-14-2005, 07:25 PM
I'm pretty sure it's all moment arm.

The torque is being generated entirely by the interaction between the permanent magnets and the electromagnets, independent of the mass of the rotating can. Technically, some torque might be generated by the interaction of the mass of the outer can and gravity, but assuming the outer can is uniform all the way around, effects of gravity are neutralized.

timocharis
11-14-2005, 08:16 PM
I'm pretty sure it's all moment arm.

Personally, I kind of doubt it (though Ron is not someone to be taken lightly). I would also assume the higher magnet count has some significant effect. (More pulses per revolution should, I would think, mean an automatic torque increase).

Though I suppose it's possible to have a 12 or 14 mag inrunner, they'd have to be relatively small magnets. And of course this is the direct result of having a larger diameter to work with (impossible without increasing the moment arm!)

Am I missing something here?


Dave North

ron_van_sommeren
11-14-2005, 09:02 PM
Of course there are more variables that influence torque, statorpole- and magnetpole-count being only two of them.

diy 14 mag lrk inrunner:
http://www.cenara.com/users/ce00359/LRK220.htm

Unbalanced prop
11-15-2005, 03:40 PM
For my type of flying, I personally like outrunners for simplicity of setup and maintenance. No gearbox and gears to setup and maintain. Sort of a plug and play type motor. They are also quieter then a geared inrunner. I have had very good results using outrunners in small and large (4 -5 lb) planes.

Geared inrunners are more flexible and prop sizes can be changed over a wider range by simply changing gear ratio. An outrunner is limited in the prop sizes you can use. Some peple like the fact that if you crash a geared plane, the gearbox takes the most abuse, and not the motor.

Doug

Elfwreck
11-27-2005, 06:51 PM
[quote=Dr Kiwi;22313]Briefly:
Inrunners have a rotating, wire wound, armature spinning within a magnet-lined can.

Hey now,
I'm surprised nobody caught this. You described a brushed motor, not a brushless inrunner. Brushless inrunners have a wire wound *can* and a central rotating magnet.
RobII

Dr Kiwi
11-28-2005, 04:09 AM
[quote=Dr Kiwi;22313]Briefly:
Inrunners have a rotating, wire wound, armature spinning within a magnet-lined can.

Hey now,
I'm surprised nobody caught this. You described a brushed motor, not a brushless inrunner. Brushless inrunners have a wire wound *can* and a central rotating magnet.
RobII

Duh! I'm sorry - a major slip of the pen (and the brain driving it)!

Elfwreck
11-29-2005, 05:35 PM
Hey now,
Just another reason to drink your coffee before posting...
RobII

Dr Kiwi
12-03-2005, 01:36 AM
Hey now,
Just another reason to drink your coffee before posting...
RobII


I agree. Just for the record my PhD's in Geology - maybe that's why I make mistakes with Electrical Engineering. :D My piloting skills are so bad I wouldn't get through an undergraduate degree in "crashology" - nothing would survive to be the subject of a PhD.

Elfwreck
12-03-2005, 05:01 PM
Hey now,
The undergrad work wasn't so bad. It was coming up with a completely new and different way to crash for my discertation that was rough:eek:
But it was the perfection of the "side arm overhand corkscrew launch"
that really did it. I can hand chuck a model into the ground at angles Euclid never thought of:D
RobII

timocharis
12-03-2005, 06:46 PM
Phil, if you're not crashing, you're not learning. So it just means you're learning a lot faster than some (though not necessarily me).


Dave

Dr Kiwi
12-04-2005, 04:03 AM
I grew up with completely indestructible C/L aircraft - powered by Oliver Tiger 2.5cc diesels - hit the ground or even a soccer goal post at 90mph and they usually bounced. Hitting the ground from a vertical power dive simple meant bending the nylon prop back into shape, cleaning the dirt out of the venturi - and away you go again! This electric stuff is far too fragile for ham-fisted old guys!

P.S. One of my Oliver Tiger III's (vintage perhaps 1960 - I bought it second-hand for five quid in 1963) still runs well!

cyclops2
12-04-2005, 09:36 PM
There nothing rugged about plastic 6:1 gearboxes, by any manufacturer. 6' to 15' usually does mine in with 400 motors from Germany.