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Author Topic: Here is a good question. ( I think )  (Read 1804 times)

Offline RC Storick

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Here is a good question. ( I think )
« on: January 03, 2014, 07:56:24 PM »
Why are the magnets so strong on a AXI and yet it makes no performance difference to the Cobra or E-flight? I can tell?
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Offline Tim Wescott

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Re: Here is a good question. ( I think )
« Reply #1 on: January 03, 2014, 10:42:10 PM »
I assume you're talking about the cogging that you feel as you turn the motor?

AFAIK all the motor magnets are roughly the same strength (give or take 10%).  What you're probably feeling is the difference between a motor where the manufacturer has purposely reduced cogging torque and a motor where they haven't.

Basically, if the armature laminations are skewed so that the slots are slanted, then the cogging torque is reduced without significantly affecting the motor performance.  It makes the motor harder to manufacture, though.

If someone who has had these motors apart could comment on whether some armatures have skewed slots and some have straight, then it would verify (or rule out) my wild ideas.
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Offline RC Storick

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Re: Here is a good question. ( I think )
« Reply #2 on: January 04, 2014, 12:17:35 AM »
The magnets and stators are all straight.
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Offline Tim Wescott

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Re: Here is a good question. ( I think )
« Reply #3 on: January 04, 2014, 12:45:10 AM »
Clank bash rattle (sound of another theory hitting the round file).

Oh well.  I know the slanted slot thingie is done in motors for industrial applications, I'd always assumed that's what ours did.

Now I want to know how they achieve it!
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Offline Igor Burger

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Re: Here is a good question. ( I think )
« Reply #4 on: January 04, 2014, 01:59:06 AM »
Quote from: Robert  Storick on January 03, 2014, 07:56:24 PM
Why are the magnets so strong on a AXI and yet it makes no performance difference to the Cobra or E-flight? I can tell?

If you speak about cogging as Tim wrote, then it has (almost) nothing to do with efficiency. Cogging makes shape of magnets and stack teeths and air gap. There are also motors with armature without teeths, such motor does not have any cogging, means feels from outside like without magnets and still can run at high efficiency and performance :- ))) 
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Offline Igor Burger

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Re: Here is a good question. ( I think )
« Reply #5 on: January 04, 2014, 02:03:52 AM »
Quote from: Tim Wescott on January 03, 2014, 10:42:10 PM
AFAIK all the motor magnets are roughly the same strength (give or take 10%). 

There are motors with different magnets. FOr example MEGA makes motors of 2 different magnet strengths (normal, and "E" series). Difference is expectable - stronger magnets have smaller winding resistance and higher no load current, means operation pont for best efficiency is also different (torque type applications versus high rpm applications).
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Offline Avaiojet

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Re: Here is a good question. ( I think )
« Reply #6 on: January 04, 2014, 06:58:51 AM »
AXI is not made in China.

Have a three year warranty AND life time replacement at 50% the original cost.

Charles
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Offline Tim Wescott

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Re: Here is a good question. ( I think )
« Reply #7 on: January 04, 2014, 09:44:27 AM »
Quote from: Igor Burger on January 04, 2014, 02:03:52 AM
There are motors with different magnets. FOr example MEGA makes motors of 2 different magnet strengths (normal, and "E" series). Difference is expectable - stronger magnets have smaller winding resistance and higher no load current, means operation pont for best efficiency is also different (torque type applications versus high rpm applications).

I know that even within the rare earth magnet selection you can get a variety of magnet strengths.  But the variation isn't as much as the variation that I've noted between strongly cogging motors and smooth ones.

Any time I try to stay on the one point I'm trying to make I always manage to be ambiguous.
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Offline Tim Wescott

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Re: Here is a good question. ( I think )
« Reply #8 on: January 04, 2014, 10:28:54 AM »
Quote from: Robert  Storick on January 04, 2014, 12:17:35 AM
The magnets and stators are all straight.

Wait a minute -- did you take them out of the motor to look?  The slots only need to twirl about the width of the slot for the anti-cogging to really kick in: just peering in the end isn't going to do it.  Even making the slots super narrow should go a long way to relieving cogging, for that matter.
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Offline RC Storick

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Re: Here is a good question. ( I think )
« Reply #9 on: January 04, 2014, 10:54:37 AM »
I have had both of these motors apart apart . It's a difference in magnet strength.
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