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Old Jan 17, 2013, 06:40 AM
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Brushless motor stutters at high speed

Hi,

I have a brushless motor (http://www.rctimer.com/index.php?gOo...9&productname=) that begins to stutter from 48% throttle up with no increase in speed from that point on. And this only happens when the prop is on. I've tested it wiht a brand new ESC with the same results.

I did short it a bit by using too long screws, and since then it started behaving like this.

Is this caused by a short inside? Is this fixable?

Thanks
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Old Jan 17, 2013, 01:38 PM
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I had this same issue about a week ago. It was suggested that I try changing the timing. In my case, increased timing fixed the issue completely.
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Old Jan 17, 2013, 02:15 PM
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Quote:
Originally Posted by zer0g View Post
I did short it a bit by using too long screws, and since then it started behaving like this.
Is this caused by a short inside? Is this fixable?
Thanks
If it didn't before, and does now....you probably ruined it.
The only fix is a rewind.
It's not an uncommon mistake that you won't do again, eh?
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Old Jan 17, 2013, 02:16 PM
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Thaks for the reply.
I'm using escs with simonk firmware which employs "24-bit timing and PWM pulse tracking at full clock rate resolution" as described in the features. I don't think there's anything more I could do here.

Hmm.. I have found this thread which seems to describe my problem. It might be an esc firmwire issue..
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Old Jan 17, 2013, 02:28 PM
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An OK motor with stuttering indicates a bad connection or a timing issue.

Too long a screw that hit the windings, strips off the enamel insulation and makes a short. So now you have a connection issue that can't be readily fixed.
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Old Jan 18, 2013, 06:00 AM
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Ok. Tried it with a new motor and works fine. So for sure I've burned something in the old motor while shorting it... Strange though that the short becomes visible only at high throttle and with prop on..
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Old Jan 18, 2013, 02:44 PM
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That's probably because you shorted the interior wires to each other. In one or more windings you probably have the equivalent of a non-functioning 'cylinder'. There are 3 phases, corresponding to the 3 wires that come out. Each phase should be identical to the others. You now have one that is crippled. Under no load it gets by but under load and speed it shows that it's not working properly.

You didn't burn it, you simply shorted it. That's plenty.
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Old Jan 18, 2013, 03:28 PM
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Thanks. I was thinking that something like this was happening and the magnetic field generated by at least one of the phases has a lack in intensity and thus the stuttering. But I hoped. I'm so sorry coz it was almost new... I guess I'll have to try to rewind it.. to pay for my stupidity ..
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Old Jan 18, 2013, 03:40 PM
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If you really want to learn there is plenty of info. OTOH, if you simply want to re-coupe your losses, don't bother. That's not an optimal motor to learn on. Your first attempts will be as trying and likely as successful as your first attempts at flying. It is not as straightforward as one would think.
Getting the parts together to start will cost more than a replacement motor.
The good side is knowing way more about motors than you do now, and being able to make (some) motors even better than you can buy them. It can be part of the sport in it's own right. There is a small community of active rewinders.
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