SMALL - Telemetry SMALL - Radio
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Old Jul 16, 2010, 02:56 AM
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Rewinding motors...
My brain cant seem to remember how many turns ive put round each of the sections, talk about short term memory loss , so I found this usefull counter..
counter 1.0 at www.dssf.net hit the space bar as you add a turn..simple enough for me...
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Old Sep 16, 2010, 02:44 AM
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i hope i dont sound like a complete idiot, but " what is meant by a short" i have been looking at rewinding my BW motors, and a couple of other motors, and i have watched a you tube vid, and after each faze you check for shorts, but thats the bit i dont get, what causes this short, is it when the wire touched the outside of the stator, i hope someone can explain this for me, as i dont want to fry my rewinds
carl
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Old Dec 20, 2010, 10:07 AM
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What is a short?

Quote:
Originally Posted by doggit View Post
i hope i dont sound like a complete idiot, but " what is meant by a short" i have been looking at rewinding my BW motors, and a couple of other motors, and i have watched a you tube vid, and after each faze you check for shorts, but thats the bit i dont get, what causes this short, is it when the wire touched the outside of the stator, i hope someone can explain this for me, as i dont want to fry my rewinds
carl
I only just joined, so sorry for the late reply. A "short" or "short circuit" is when any two conductors that need to be insulated from each other are in contact and conduct electricity.

In our case, if the corner of a stasor cuts through the insulation on a copper winding, that has the potential to connect it to a later winding that also gets nicked through the iron of the stasor.
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Old Dec 20, 2010, 04:12 PM
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Carl,

As an example, and so you can see how your meter handles and displays it, if you put the meter on the Rx1 or lowest resistance scale and touch the tips of the test leads or probes together you'll get a displayed value of 0.0 Ohms or something close to it like 0.01 or 0.02 Ohms or so.

If you hold the probes in contact for a few seconds, the reading may drop to 0.0 Ohms as the meter stabilizes. And that is a dead short between the probes, no resistance.

Some meters will display 0.0 when the probes are not in contact because there is no resistance present, others (my Fluke for example) will display "O.L." to indicate an "open line" when you are in the Rx1 or Check for Shorts mode.

When you put one probe on a stator and the other probe on a wire end there may be small amounts of paint or insulation at the points where the probes make contact and those will change the readings you see on the meter as compared to the reading you saw with the probes shorted together. And things like the pressure you use and how well you make contact will change the readings.

If basically comes down to that the meter is just trying to do the best it can at showing you what the actual resistance, if any, is between the two probes.

So when you have a short between the winding and the stator it might have some small amount of resistance that is caused by the "quality" of the contact at the probe and the point where the short is.

If I check for shorts and see a low resistance like 0.4 or 0.6 Ohms or so and if the number is dancing up and down a little, it still a short. The difference in the numbers is the "quality" of the contact points.

I have meter probes with interchangeable tips and I can change from needle point probes to clip on alligator clip probes. So when I start a winding I scrape the start end of the wire so I can clip one alligator clip on there.

As I complete the turns on each stator arm, I clip on to the scraped and can just touch the tip of the other probe to a bare spot on the stator (usually the ends of the hammer heads are bare of insulation and that is a good spot) and check for shorts before I move on.

Jack
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Old Oct 13, 2011, 03:18 PM
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Lots of goodies/tools/calculators for diy motor building/winding:
http://www.flugzeugseite.de.tf/


Vriendelijke groeten Ron
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Old Oct 16, 2011, 12:16 PM
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Try the diy electronics subforum Julian, plenty of ESC discussion there. I try to keep this diy motor tips & tricks thread lean and mean, every now and then I comb through it and remove posts. I will remove your post to, after a while.

Compilation of sensored and sensorless diy brushless controller designs:
http://www.rcgroups.com/forums/showthread.php?t=140454

Vriendelijke groeten Ron
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Old Oct 17, 2011, 10:48 AM
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There is the possibility to move the post?
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Old Oct 17, 2011, 04:51 PM
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This sticky is privately moderated by me. But I cannot move your post, I can only delete posts. Just do a copy/paste, I see you already have some experience in the copy/paste field It baffles me to see that you were referred to the, several subfora, even the 1:1 subforum, instead of the diy electronics subforum.

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Old Nov 09, 2011, 09:34 AM
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Winding tool.

This DIY kit had a very short bearing tube so I used a 4-40 bolt and a 1/2in in diameter hardwood dowel-rod and drilled and tapped it for a 4-40 allen head bolt and used a large enough washer to cover the outside race of bearing.A 4-40 bolt will fit through a bearing with a 3mm inner diameter.

Worked very well and did no damage to bearings.
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Old Jan 02, 2012, 03:25 PM
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anyone know what has happen to this very informative site

http://www.powercroco.de/

just before holiday's it went down now back but all the great info has disappeared and no longer available.

just started to look into winding motors and can't seem to find other links that would help a newbie like myself.

tried most of the links provided here but non compare to powercroco.
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Old Jan 02, 2012, 05:45 PM
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www.powerditto.de

I think this was the original name. Loks like Ralph has seperated the speed planes from the other info.
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Old Apr 18, 2012, 07:16 PM
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Ron,

This question may not have a place on your "sticky" but I can't find an understandable answer so I'm taking a chance. If it's out of place just disregard my question.

What happens to an outrunner when you use more battery cells in series to power it than the number outlined by the manufacturer. I know the rpm increases, and I've been told you can destroy the motor. Why and how does that happen with to high a voltage?

Regards,

Hankg
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Old Apr 18, 2012, 07:48 PM
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Quote:
Originally Posted by hankg View Post
What happens to an outrunner when you use more battery cells in series to power it than the number outlined by the manufacturer. I know the rpm increases, and I've been told you can destroy the motor. Why and how does that happen with to high a voltage?
Unless you apply voltage high enough to break insulation (that would be probably in kilo-Volts) nothing will happen. Of course the rpm may exceed max rpm for bearings, and balancing quality or motor might explode from centrifugal force. But we are talking extreme here. The other limiting factor would be current running through the wire. Even if motor is unloaded at high rpm it will get enough load from the bearing and wind resistance that might exceed the max current for that design. The last part is the frequency of the alternate current powering the motor. Because of iron losses at high frequency it will heat the stator, and because of surface current effect it will reduce the maximum current that wire can handle.

So in short the real limiting factors for the motor are:
- voltage if high enough to break the insulation (unlikely),
- rpm for bearings, vibrations and centrifugal force (possible),
- current which may generate more heat in winding than the cooling might remove (most common)
- high switching frequency which reduces motor's efficiency (unlikely)
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Old Apr 19, 2012, 11:48 AM
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Quote:
Originally Posted by hankg View Post
... This question may not have a place on your "sticky" but I can't find an understandable answer so I'm taking a chance. If it's out of place just disregard my question. ...
I will delete these posts later Hank, and/or move them to a new thread if you start one. I do this every now and then, to keep this sticky lean and mean.

What Richard/Rysium said

Volts jolt, current kills. And current wants to go up squared with voltage, increase will be higher than one would expect. I have made this very simple table which lists the effect of one/two extra cells on current:
http://www.wattflyer.com/forums/show...945#post594945
http://www.wattflyer.com/forums/show...red#post591620

And since copper losses (=heat) go up squared with current (Pcopper = I² Rcopper, copperloses go up with voltage^4! E.g. double voltage gives 16 times more copperlosses, worst case.

Also: motor power wants to go up cubed with voltage.

Vriendelijke groeten Ron
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• Get a life ... get a Watt-meter!!! •
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Old Apr 21, 2012, 08:30 AM
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Quote:
Originally Posted by rysium View Post
... Because of iron losses at high frequency it will heat the stator, and because of surface current effect it will reduce the maximum current that wire can handle. ...
Skin effect does not come into play here Richard, frequencies are not high enough.
Quote:
Originally Posted by rysium View Post
... - high switching frequency which reduces motor's efficiency (unlikely)
And low switching frequency also reduces motor efficiency.
Quote:
Originally Posted by hanzie View Post
That's Dutch, it means something like 'best regards'
Are you a member of www.modelbouwforum.nl too?


Vriendelijke groeten Ron
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