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Old Feb 24, 2013, 07:52 AM
Jack
USA, ME, Ellsworth
Joined May 2008
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Quote:
Originally Posted by ArtPiranha View Post
Dualsky is not good for us, it has very strong magnets and a huge magnetic cogging
I read so many comments here about cogging implying that the presence of it was a bad thing. But I'm not sure that feeling the cogging effect by turning the magnet housing with your hand is a meaningful evaluation of it, nor does it necessarily imply that it will be some measure of what will happen with the motor is running.

As to what you feel by hand, consider this. The cogging you feel will be different in each one of these situations:

1 - Motor disconnected from ESC

2 - Motor connected to ESC and ESC not connected to battery

3 - Motor connected to ESC and ESC connected to battery

4 - Motor connected to ESC, ESC connected to battery, and ESC armed

5 - When connected to a powered up ESC, the brake and timing settings can have an effect on what you feel

6 - Motor disconnected from ESC and the three connectors on the motor leads shorted together.

Situation 6 is when the cogging will have the lightest feel and it is the only situation where the cogging steps will be felt as equal and evenly spaced.

And I think #6 is the only situation where the number of cogging steps will be the "cogging steps" value that results from the test2 calculator.

It would seem to me that, for this gimbal purpose, the wind that has the highest value for cogging steps would be the motor that has the potential for the smoothest movement and least "vibration" as it moves from step to step. And I say that because it would be the situation with the shortest movement from one potential stopping point to the next.

And, beyond that, I think the design and programming of the ESC that will really control how quickly the motor will start to move, how fast it will move, and how abrupt the stop will be as it goes from one step to another.

I am not a motor expert and am not sure I know enough to even discuss this intelligently. But the focus on what people feel when they rotate a magnet housing by hand might not be a good reason for choosing motors or determining which motor might be better than another.

I've tried to understand cogging better and found a wiki article that seems to discuss it but I don't seem to come away feeling any smarter when I read that as it is too technical for me:

Cogging torque - http://en.wikipedia.org/wiki/Cogging_torque

This is just idle discussion, I'm not trying to say that cogging should or should not be ignored. But I think we might have more to learn about it as far as if and how we should consider it.

Jack
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Old Feb 24, 2013, 07:53 AM
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Joined Dec 2007
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Quote:
Well, he did say that he had 7.3 ohms across 2 phases with 2 strands/30 turns, so I would assume winding the same motor with 1 strand/60 turns would double the resistance....

Nope, going from 2 strands to 1 strand would double the resistance, doubling the windings too would quadruple the resistance
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Old Feb 24, 2013, 09:04 AM
Begin with end in mind...
power's Avatar
Eagle Lake, Minnesota
Joined Apr 2003
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Quote:
Originally Posted by Coyote64 View Post
Nope, going from 2 strands to 1 strand would double the resistance, doubling the windings too would quadruple the resistance
So.. 60T of say 30ga (.010) wire should be about perfect then?

This is fun learning and experimenting as my fingers and eyes are straining but I can't help thinking about companies like T-Motors and RC-Timer soon offering prewound motors for this application. At times I don't see the personal reward after spending several hours winding these little buggers. For now, it's all we can do.

Mike
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Old Feb 24, 2013, 09:41 AM
Friend is a 4 letter word...
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3rd stone from the sun
Joined May 2007
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Quote:
Originally Posted by Coyote64 View Post
Nope, going from 2 strands to 1 strand would double the resistance, doubling the windings too would quadruple the resistance
Of course, stupid me...Didnt quite think it through...
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Old Feb 24, 2013, 10:34 AM
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Croatia, City of Zagreb, Zagreb
Joined Mar 2012
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what about this http://www.haydonkerk.com/LinearActu...7/Default.aspx
or if any of u know price of this Printedmotorworks XR15-03-C series or where to buy
http://www.printedmotorworks.com/wp-...Overview-6.pdf
or maybe this is best "anticogging" solution http://www.thingap.com/products/index.htm
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Old Feb 24, 2013, 04:38 PM
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Rewinded a Turnigy 5014 with .2 wire. 150 turns and got 15 ohm.

Rewound Turnigy 5014 (0 min 38 sec)



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Old Feb 24, 2013, 04:39 PM
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Testrun on my gimbal with Nex 7

Alexmos SBGC with Sony Nex 7 (0 min 52 sec)



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Old Feb 24, 2013, 05:04 PM
Begin with end in mind...
power's Avatar
Eagle Lake, Minnesota
Joined Apr 2003
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Looks great Fredrik, great job!

That motor looks to have a lot of room to work, those tall stator arms look naked

Are you running 3s?


Mike
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Old Feb 24, 2013, 05:08 PM
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Thanks. I use 4S.

Yes its some space left.


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Old Feb 24, 2013, 07:30 PM
Make UAVs, not drones! ;-)
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Vancouver, BC Canada...eh!
Joined Feb 2010
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Quote:
Originally Posted by Fredrik R View Post
Testrun on my gimbal with Nex 7

http://youtu.be/qb_SN_6w0Nw


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That's lookin' smokin' good! My HX30 should be no problem.
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Old Feb 24, 2013, 11:43 PM
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Norway Haugesund
Joined Jun 2010
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Fredrik R that's one nice gimbal... Did you make that one ?

I like the 5014, easy to mount on the gimbal, the nx I have is not that nice.. Now I need to make a order from hk again. Is it okay to let you share more parts info on your gimbal?
The main parts like clamps, cf tubing and your custom milled parts ?

Thanx
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Old Feb 25, 2013, 12:27 AM
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Thanx. Yes i did

Not to fancy on the gimbal parts. 19mm carbon tube with boom clamps.
Camera plate is made of 4mm G10. I like rigid camera plates
All other G10 is 2mm.

This is my first prototype. Will make one gimbal for a DSLR but I sold my 7D and only have an old Nikon that does not film... If Im nice my friend might borrow me one 7D
Also a GoPro version is at the drawing table
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Old Feb 25, 2013, 12:53 AM
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Old Feb 25, 2013, 08:09 AM
vip
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United States, WA, Seattle
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Quote:
Originally Posted by Fredrik R View Post
Thanks. I use 4S.

Yes its some space left.


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Do you have to use a 4S to power this?
seems like allot of weight to add just to power the gimbal?
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Old Feb 25, 2013, 08:37 AM
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Originally Posted by vip View Post
Do you have to use a 4S to power this?
seems like allot of weight to add just to power the gimbal?
Can use 3S to.
But I will take power from my multirotor that is using 4S.


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