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Old 03-29-2012, 03:05 AM   #1
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Default Electric motor without magnet

Is there a motor without the magnetic forces in the rotor that runs free? I know i can just run a X12 a couple of times with too much timing but is there some other way around?
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Old 03-29-2012, 03:18 AM   #2
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42 is the answer
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Old 03-29-2012, 04:07 AM   #3
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42 is the answer


and wetwang is the centre of the universe
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Old 03-29-2012, 04:18 AM   #4
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Is there a motor without the magnetic forces in the rotor that runs free? I know i can just run a X12 a couple of times with too much timing but is there some other way around?
Not in electric...electric motors all use magnetic forces of some kind. Nitro engines are non-magnetic.

I think i know what you mean though in that you are concerned that the magnetic forces may slow down the motor too much...the old brushed motors were much stronger in that effect and was not really an issue. If your car is slowing down too much now it is more likely due to binding in the drive trane somewhere and not due to strong magnetic forces in a BL motor.
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Old 03-29-2012, 05:13 AM   #5
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A smaller diameter rotor, or a weaker rotor will both reduce the effect you are seeing. The X-12 motors have very strong rotors, so when you turn them by hand, you can feel the "notchyness" as it rotates. Thus, when you lift off the throttle, it adds some natural drag brake.

Increasing the air gap by using a smaller rotor will reduce this, at the expense of slightly less torque (but more RPM). The air gap is the distance from the rotor to the stator. You can get the same results with a magnetically weaker rotor.

Depending on the ESC you are using, you can also reduce the drag brake setting, or add push control, which applies a small amount of throttle to counteract this effect.
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Old 03-29-2012, 07:30 AM   #6
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Is there a motor without the magnetic forces in the rotor that runs free? I know i can just run a X12 a couple of times with too much timing but is there some other way around?
Are you familiar with how an electric brushless motor actually works?

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42 is the answer
I disagree. 71 is the clear choice
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Old 03-29-2012, 08:31 AM   #7
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The very first generation of brushless motors did not have much magnetic force in them and its actually because i run RC Bikes and you want as little magnetic force as possible. Thats why i ask... I cannot buy 20 different brushless motors and try out myself.

Btw. drag brake is on 0%
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Old 03-29-2012, 09:05 AM   #8
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An induction or asynchronous AC motor would not have permanent magnets in the rotor.
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Old 03-29-2012, 09:06 AM   #9
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The very first generation of brushless motors did not have much magnetic force in them and its actually because i run RC Bikes and you want as little magnetic force as possible. Thats why i ask... I cannot buy 20 different brushless motors and try out myself.

Btw. drag brake is on 0%
The Thunder Tiger Europe bike team uses Reedy motors with good results. The drag brake is not severe and the powerband is very smooth.
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Old 03-29-2012, 09:07 AM   #10
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The very first generation of brushless motors did not have much magnetic force in them and its actually because i run RC Bikes and you want as little magnetic force as possible. Thats why i ask... I cannot buy 20 different brushless motors and try out myself.

Btw. drag brake is on 0%
Have tried to run a Tekin? They have a setting called push that might do what you are looking for.
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Old 03-29-2012, 09:26 AM   #11
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Some of the early Feigao motors had almost no magnetic 'drag'. Unlike the current designs of BL motors, those early motors did not have an iron core with the stator wires wound around it. They just had loops of wire crammed into the can with no core. So, no magnetic drag as long as there was no current flowing through the stator coils. Something like these motors: http://www.rc-monster.com/proddetail...WAND_XL&cat=20
Of course, they also aren't sensored. Don't know if you'll find a sensored motor with no magnetic drag. If you really need sensored, then Highside20's suggestion of using a Tekin with push control is your best bet.
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Old 03-29-2012, 09:53 AM   #12
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A multi-phase induction motor has no permanent magnets and therefore has very little freewheeling resistance, but good luck finding one of those at your local hobby shop.
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Old 03-29-2012, 10:52 AM   #13
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was going to say thers r no mag motors out there but not our size.
I could be done for rc just dont know how useful or effective it would be for our needs.
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Old 03-29-2012, 11:34 AM   #14
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I disagree. 71 is the clear choice
no you are wrong my good friend 42 is always the answer , 71 is clearly a crazy number dreamed up by mad rabbits
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Old 03-29-2012, 03:04 PM   #15
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no you are wrong my good friend 42 is always the answer , 71 is clearly a crazy number dreamed up by mad rabbits
Actually, I believe it was George Carlin that came up with 71. Let's just say it is related to 69

As for the motor question, get a Tekin, use push control and any motor you want. Between push and drag, you should be able to get any off throttle feel you want.
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