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Old Jan 14, 2013, 05:26 PM
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I can see two possible reason why not to run a motor to its max unloaded....

1) No bearings are made for these RPMs we use. They are made for X RPM (probably 20k etc) as they use somewhat generic bearings. A bearing has a design parameter for RPM and lifespan ( and other aspects too of course), and say it is 20k RPM... if you run it at 20k RPM it will meet the mean lifetime spec. If you run it at 30k rpm it will not 'explode'(!), but its lifespan will reduce.
At some point of higher RPM it will fail very quickly of course, but they can cope with what we use them for.
So the RPM an unloaded motor will reach is still not an issue.... but wears it faster.
You can check bearing sites for info on this stuff.

2) Probably likely, as suggested by Supercollider, (but I don't know for sure) is that the BackEMF of an unloaded motor could be WAY higher than from loaded motor. So this 'much higher' level could be bad for ESC's circuitry.
The RPM it reaches should not outrun most ESC's.... but combine the 'different' BackEMF situation and it might send them a bit gaga.
And also, seeing they can run to higher RPM unloaded, the ESC Timing you had set for good Loaded use might be too low for good Unloaded motor running.

In pure physical terms of RPM reached I don't think it should matter too much except if done for too long. Bearing heat would matter more... if that even gets to a problematic level anyway. Then the X amount higher than specs RPM of the bearing. So in those terms, I would not want to run it for more than seconds - especially seeing it is rare that you even need to do it at all.
Mainly for testing unloaded KV.
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Old Jan 14, 2013, 05:40 PM
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Originally Posted by WhalleyB0Y View Post
Nah this was happening at low throttle on 3s. I just wanted to see how true the motor shaft runs. Maybe 20%? I will post a video later if it continues.
ya ok if thats the case then I would check motor wire solder connections for a bad solder joint beyond that it will be a bad esc or motor in that order
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Old Jan 14, 2013, 05:58 PM
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The bEMF can't exceed the voltage applied to the motor by the ESC. kv works just as well for generators as for motors (indeed, that's how we check it after rewinding!)

I have noticed a motor run up with no load warms up quicker than I'd expect for only 1-2A draw, there might be a high risk of burning the motor? I don't know why it happens though
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Old Jan 14, 2013, 06:24 PM
chuck
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Originally Posted by Odysis View Post
The bEMF can't exceed the voltage applied to the motor by the ESC. kv works just as well for generators as for motors (indeed, that's how we check it after rewinding!)

I have noticed a motor run up with no load warms up quicker than I'd expect for only 1-2A draw, there might be a high risk of burning the motor? I don't know why it happens though
i think u will find the no load current much higher than 1-2 ?
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Old Jan 14, 2013, 06:55 PM
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Even if the esc sees just a few volts of counter EMF or back EMF ( same difference ), at those speeds you can possibly mess up the timing. Some esc's may tolerate more or less of this depending on their design. Best case it turns into heat, worst case you could damage the esc. A few seconds shouldn't hurt but you never know.
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Old Jan 14, 2013, 07:09 PM
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...

rccastle recently has complete 10 blade 70mm fan unit, $74
Cyclone Power 7010 2200Kv Power Unit For 5S - 6S With Dynamic Balanced !
5s = 18.5v, Static Thrust: 1700g, 55A

anybody had experience with it?
Just Wonder about the sound... ????
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Old Jan 14, 2013, 08:15 PM
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[QUOTE=WhalleyB0Y;23805134]
Quote:
Originally Posted by supercollider View Post

I use a 2950kv long can Tenshock motor in a CS10 fan. In my Habu with 5s packs it peaks at 90 amps and settles at 75-80. I use house branded Gens Ace packs that are 3300mAh 30C. Is this a hot setup? I didn't think it was...

http://youtu.be/nevigrRCRwU
Check your pack and cell voltages, I was pulling over 100 amps easy on that...
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Old Jan 15, 2013, 03:09 AM
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[QUOTE=erh7771;23816158]
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Originally Posted by WhalleyB0Y View Post

Check your pack and cell voltages, I was pulling over 100 amps easy on that...
Yea I checked my packs and they are still the same ol' crappy generic house brand that tend to sag like old titties in hard times.
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Old Jan 15, 2013, 03:29 AM
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Originally Posted by chas650r View Post
i think u will find the no load current much higher than 1-2 ?
Why? I've got much larger motors in my collection with a much lower Io than that (i.e. a Neu 1515/1.5Y is around 1.2A)
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Old Jan 15, 2013, 03:42 AM
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I limit my no load motor runs to about 5 seconds......just to get no load KV from ICE ESC or Eagle Tree data logger w/brushless RPM sensor.

The motors do heat up more than I expect without a load on them.

Pole count also has some effects on how much they heat up.


I don't see any good reasons to run longer duration no loads....if it was not for occasional initial hickups by various loggers, I would shorten it down from 5 sec.



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Old Jan 15, 2013, 03:48 AM
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KV effects no load AMPs big time.
Motor lenght effects it.
Quality of magnets effects it.
Pole count....

D (Delta) winding has higher no load AMPs than similar KV Y winding.


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Old Jan 15, 2013, 08:25 PM
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Originally Posted by WhalleyB0Y View Post
I wish I could agree that these ARE a high end motor as I never had much luck with them. In fact out of 5 of these motors the one in the Habu is the only one I can get working right.
Just read the last few pages of this thread to see what a nightmare they have been for me...
http://www.rcgroups.com/forums/showthread.php?t=1730546

I am trying again to use them but this time in a CS12-70mm fan. So far not much luck. I go to ramp up the motor with no load and it runs great for about 5 secs and then it stops. Lower throttle and try again and the same thing.

I'm going to try again with another controller and see. But just in case these really are crap, could you recommend an awesome high end motor for use on 4s-5s with these fans? I'm about ready to scrap these new motors for canopy magnets.
So it appears this problem is with the Eflite 60A esc. With the CC Ice the motor is operating normally. So I will continue the process of mounting them into the CS12 fans while looking for furthur issues.
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Old Jan 16, 2013, 12:26 AM
chuck
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Originally Posted by WhalleyB0Y View Post
So it appears this problem is with the Eflite 60A esc. With the CC Ice the motor is operating normally. So I will continue the process of mounting them into the CS12 fans while looking for furthur issues.
gee , that's the first time i have ever heard of 1 of those being a pos

glad u got it figured!
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Old Jan 16, 2013, 12:33 AM
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But also test that ESC with ANOTHER motor/combo.
Sometimes an ESC/Motor combination just hate each other!
Neither being really faulty... they just don't work well together.
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Old Jan 16, 2013, 12:38 AM
chuck
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Originally Posted by PeterVRC View Post
But also test that ESC with ANOTHER motor/combo.
Sometimes an ESC/Motor combination just hate each other!
Neither being really faulty... they just don't work well together.
agreed, just put it in plane u dont like! and don't use it at over 35 amps.
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