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HelicopterMain Discussion › Some motors turn freely, others only risking gear damage
08-13-2010 10:08 PM  7 years agoPost 1
Kaarlo

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Helsinki Finland

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Whether you can turn the main rotor easily or not at all is an issue when loading an electric helicopter with a 6 - 7 foot rotor into a car or trying to get it through a door, especially if you are using a paddle equipped main rotor.
You would tend to think, the stronger the magnets in a motor the more efficient the motor is. Just a few examles of the many motors we have tested, Kontronik Tango (inrunner) motors are very efficient but can be made to spin with no resistance at all. The same manufacturers Pyro motors will not spin but turn relatively easily, but you can feel the typical resistance caused by the magnets when turning the motor or the main rotor. The Actro (outrunner) and Align 600 motors are giving much higher resistance and the Xera (outrunner) motor is so tightly held by the strong magnets that it is virtually impossible to turn the main rotor of a helicopter with a Xera motor installed, except of course in the freewheeling direction of the main rotor. The Xera would have been very well suited for the GPS autonomously flying helicopter we are developing, ( 12 S 2 Ah lipo set up) but met with opposition due to this feature. The question how easily a motor can be turned seems not to be proportinate to the pole count or RPM/1 V. Anyone able to explain the phenomenon and/or give a list of efficient 12 S motors that turn easily or a thread about this topic?
Kaarlo

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08-13-2010 10:43 PM  7 years agoPost 2
thenewguy

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Corvallis, Oregon Where there is liquid sunshine!

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One thing to keep in mind. When you drive a motor by hand you basically turn it into a small generator. This will make a motor give different resistance.

Chris

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08-13-2010 11:51 PM  7 years agoPost 3
Heli 770

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USA.

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The Tango(inrunner) has an "ironless" core. Because there is no magnetic iron core, ironless inrunners have no cogging, they spin freely with no magnetic interaction when power is disconnected.

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08-14-2010 12:26 AM  7 years agoPost 4
heli_headcase

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Hovering around Atlanta

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...and the first time you handle one you'll think the magnets weren't ever installed! But just short all three wires together, try turning it and then you'll be a believer


HHC

So many heli's - too little time...

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08-14-2010 12:42 AM  7 years agoPost 5
heli_headcase

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Hovering around Atlanta

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To answer the thread starter, Kaarlo:

The effect you're describing is called "cogging" and has nothing to do with the motor's overall efficiency. The key to how/why the cogging feels is due to the number of magnets (poles) and the number of stator arms.

I too own an X-era (4035-2.5Y 480) and it is a monster to turn by hand. It's all because the magnets are always opposite stator poles (arms) directly. Each permanent magnet has a direct and unopposed attraction to an iron stator arm. Other motors using more or less magnets have a different ratio of arms to magnets and only a pair of magnets will be directly lined up with stator arms at any one moment whereas all the other magnets are either getting ready to line up or have passed the point of direct alignment. Follow? The Actro series (32-3 and 32-4 in particular) have their own unique magnet configuration -- each magnet (pole) consists of paralleled magnets sitting directly against each other in eight sets. I guess it works

My Kyosho e-Caliber 90 uses that X-era motor mentioned above and there are times I can't take advantage of the autorotation clutch to let me move the main rotor out of the way of an object. So how do I turn the rotor in reverse? I give it a firm and constant bump against the "compression" of the motor's magnets and keep a steady push on the rotor until it moves to the desired angle. Don't worry about hurting the drive gears -- if they can take the strain of flight, they can easily take the cogging of the motor.


HHC

So many heli's - too little time...

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HelicopterMain Discussion › Some motors turn freely, others only risking gear damage
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