how thick a magnet wire have you bent - RC Groups
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Sep 24, 2017, 02:44 AM
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how thick a magnet wire have you bent


awful cheap phone camera but in the picture is a weird mix of 11-12 turns with 18awg wire, just to see what I could fit, wonder if I should run it,..but what size you think I should order to try to get down to 8 turns? I was going to get 17 and 16.5 or maybe 16 as well. don't have an attic to store extra and don't want it really even if I had an attic.
there's a calculator and it's designer I think even gave me the numbers I'd need, but alas it is lost in the passing of the web












do just turns and the termination determine kv or will rare winding patterns?


with the possibility of such order with the thick wire, how do you go down to do the second layer on the tooth? it seems a big complication to take on but as it is now the loop down to do the next layer falls along the long length of the tooth and gets in the way of what could be perfect uniformity, so am thinking of doing the jump down for the next layer quickly at the back or front of the motor, a sharp bend down, and fixing the wire there clamping the wire in the back hard until the second layer is almost done, then release the clamp and finish maybe the last turn.
I like the challenge and wonder what thicknesses you will show a picture of and any advice on how I should be careful would be appreciated. I feel it streach sometimes with the 18 awg at maybe 40 lbs pressure but rarely I do that but wonder if that is a ok or how much maybe 16awg could take. I'm guessing even if I end up putting really hard pressure pulling the wire down into the gap between teeth, through wire, this shouldn't really matter even if I were to scratch its insulation as it'd be physically isolated...wonder what I cant do to it? how about smack it with a hammer and flatten it a certain amount? that's surely asking for too much.
Last edited by Hummina; Sep 24, 2017 at 03:34 AM.
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Sep 24, 2017, 06:26 AM
just look at it smokin'
z-matrix's Avatar
Quote:
Originally Posted by Hummina
awful cheap phone camera but in the picture is a weird mix of 11-12 turns with 18awg wire, just to see what I could fit, wonder if I should run it,..but what size you think I should order to try to get down to 8 turns? I was going to get 17 and 16.5 or maybe 16 as well. don't have an attic to store extra and don't want it really even if I had an attic.
there's a calculator and it's designer I think even gave me the numbers I'd need, but alas it is lost in the passing of the web

do just turns and the termination determine kv or will rare winding patterns?

with the possibility of such order with the thick wire, how do you go down to do the second layer on the tooth? it seems a big complication to take on but as it is now the loop down to do the next layer falls along the long length of the tooth and gets in the way of what could be perfect uniformity, so am thinking of doing the jump down for the next layer quickly at the back or front of the motor, a sharp bend down, and fixing the wire there clamping the wire in the back hard until the second layer is almost done, then release the clamp and finish maybe the last turn.
I like the challenge and wonder what thicknesses you will show a picture of and any advice on how I should be careful would be appreciated. I feel it streach sometimes with the 18 awg at maybe 40 lbs pressure but rarely I do that but wonder if that is a ok or how much maybe 16awg could take. I'm guessing even if I end up putting really hard pressure pulling the wire down into the gap between teeth, through wire, this shouldn't really matter even if I were to scratch its insulation as it'd be physically isolated...wonder what I cant do to it? how about smack it with a hammer and flatten it a certain amount? that's surely asking for too much.
I have coiled up some 3 mm thick double enamel coated copper wire, it needs some force, i would not use anything thicker than 1 mm - 1.2 mm because reasons most people don't even believe if told. A copper pipe or sheet is a better conductor than a wire, many parallel thin wires are good too it is called Litze wire, but the insulation and air takes more space.

You can wind 0.5 mm - 1 mm diameter wire on it as a test for example 10 turns, and connect to star, fire it up and check the speed, you can then calculate the amount of turns to reach your desired Kv, you can also connect it to delta that will give you sqrt(3) times Kv compared to star. As a side effect it will tolerate the loss of a phase winding and continue to run, star would have problems in this case.
Don't worry about the number of turns, if it is slow, use larger diameter wire, or more in parallel, the stator should be wound with as many turns you can fit for most efficiency.
You have the option to connect your coils in Star, Double Star, Quad Star, Delta, Double Delta, Quad Delta
You can use a broken plastic propeller blade to squeeze your windings in place.

If you pull hard on a magnet wire it will stretch, and it hardens, will break easier after that, then it starts to crack inside, it will have increased resistance because of the smaller cross-sectional area. Copper is usually cold formed, but then they place it in a "hot" bath to ease out the internal stresses. They pull the wire through smaller and smaller holes, this is how your wire is made.


Z
Sep 24, 2017, 12:43 PM
Registered User
This is a slow turner and I didn't think skin effect was worth thinking about . ?
Will double wye drop the kv further? I want 8 turns with regular wye or 14 delta about.

I'm not worried about hardening of the metal increasing its resistant as long as I can get it in and it doesn't short
Sep 24, 2017, 01:39 PM
just look at it smokin'
z-matrix's Avatar
Quote:
Originally Posted by Hummina
This is a slow turner and I didn't think skin effect was worth thinking about . ?
Will double wye drop the kv further? I want 8 turns with regular wye or 14 delta about.

I'm not worried about hardening of the metal increasing its resistant as long as I can get it in and it doesn't short
I think this was discussed about a million times here, electrical frequency is at least 6x rotation frequency, and your stator core has iron laminations same as in an 50 Hz rated transformer(, and the esc also does PWM).
Double Parallel Star doubles Kv.
Well you are making the wire thinner and more brittle, and you may introduce microcracks in it.
Sep 24, 2017, 02:52 PM
Registered User
Ive got 14 magnets so erpm 7 times the rpm but I remember reading here many times that even with a fast spinning prop we don't get to a frequency where skin effect would occur in the windings. What erpm would it occur?
The stator material i also didn't think would suffer especially from a high switching frequency being a slow turner
Sep 24, 2017, 03:19 PM
just look at it smokin'
z-matrix's Avatar
Quote:
Originally Posted by Hummina
Ive got 14 magnets so erpm 7 times the rpm but I remember reading here many times that even with a fast spinning prop we don't get to a frequency where skin effect would occur in the windings. What erpm would it occur?
The stator material i also didn't think would suffer especially from a high switching frequency being a slow turner
Distribution of current flow in a cylindrical conductor, shown in cross section. For alternating current, the current density decreases exponentially from the surface towards the inside. The skin depth, δ, is defined as the depth where the current density is just 1/e (about 37%) of the value at the surface; it depends on the frequency of the current and the electrical and magnetic properties of the conductor.

In copper the skin depth is about 2 mm at 1 kHz, that already occurs in my 9N12P outrunner spinning at 16 k RPM
(i have used 0.4 mm magnet wire in it)
0.4 mm - 40 kHz
There is also a PWM frequency 8, 16, 32 kHz usually at partial throttle, at full throttle there is none.

Skin depth in copper Frequency Skin depth (μm)
50 Hz 9220
60 Hz 8420
10 kHz 652
100 kHz 206
1 MHz 65.2

It is non linear, it does matter, but your motor will work, the wire will only conduct current on the outside skin at higher frequencies.
It is some trade-off between losing amount of copper cross sectional area using many small diameter strands vs skin conducting only, whatever works for you.


Z
Sep 24, 2017, 04:41 PM
Registered User
Thank u for ur answers!
Will the pwm frequency switching be experienced all the way to the windings and skin effect there based on the esc frequency or will the inductance of the coils smooth the pwm so no real switching is happening in the coils if the kv is low and inductance is high enough? Otherwise I'll d imagine there would be torque pulses as well
Last edited by Hummina; Sep 24, 2017 at 06:48 PM.
Oct 01, 2017, 09:35 PM
just look at it smokin'
z-matrix's Avatar
i have finished winding a 3 phase 12N8P 80 mm diameter bldc motor with 3 strands of 1.02/1.08 mm diameter 2z 180C rated CuZ (magnet wire)
7T not much space left, was not easy, and took hours
I was thinking about many 0.4 mm strands, but i tried to fit the most copper in i could now using thick wire.
Oct 14, 2017, 12:30 AM
Registered User
vollrathd's Avatar
awful cheap phone camera but in the picture is a weird mix of 11-12 turns with 18awg wire, just to see what I could fit, wonder if I should run it,..but what size you think I should order to try to get down to 8 turns? I was going to get 17 and 16.5 or maybe 16 as well. don't have an attic to store extra and don't want it really even if I had an attic.


Before retiring, I had access to a very wide variety of magnet wire on the end of the 250 pound spools at work. Wire size varied from around #32 down to #10 or so.

One problem with using the single winding design is the sharp corners required around the motor stator core. I ran into the varnish insulation cracking on some of those tight turns. This is much less a problem with multiple strands of much smaller diameter wire.
Oct 14, 2017, 01:13 AM
Registered User
manuel v's Avatar
There comes a time that no matter how thick the wire gauge is, the efficiency no longer increases.
Also sometimes it is so difficult to use very thick wire that ends up being counterproductive for the damage to the insulation.

Rewind a tarot motor 5008-340 with 20AWG wire and another with 21AWG wire.
the tests give me a very similar performance.

But if there is a difference, this is not worth the huge effort to use the thicker wire.

That was in my case with this engine.

Some of us are fans of HPDLRK winding.
since it occupies twice as many turns, we can use a thinner wire, which is harder to hurt.


https://www.rcgroups.com/forums/show...t=rewind+tarot



Your photo motor looks great on the bottom teeth.
Oct 15, 2017, 12:07 PM
Registered User
How exactly have u damaged the insulation? My stators are all well covered with green epoxy that stays put and I put a lot of force on the wire bending it in tension but so far no shorts

Using an inductance meter and winding two teeth back and forth in continous figure eights got the same total inductance as with the windings being done completely on one tooth then the other. For same.amount of turns.
Last edited by Hummina; Oct 15, 2017 at 12:47 PM.
Oct 15, 2017, 12:43 PM
Registered User
vollrathd's Avatar
Quote:
Originally Posted by Hummina
How exactly have u damaged the insulation? My stators are all well converter with green epoxy that stays put and I put a lot of force on the wire bending it in tension but so far no shorts

Using an inductance meter and winding two teeth back and forth in continous figure eights got the same total inductance as with the windings being done completely on one tooth then the other. For same.amount of turns.
The wire I had access to would have visible cracks in the varnish insulation when bending around very sharp corners.
Oct 15, 2017, 02:08 PM
Ronaldo Nogueira
ronaldopn's Avatar
My thickest and favorite wire is AWG16. I rewound a Tomcat 30cc with it (hpdLRK) and this week another one using LRK.
I should rewind a Turnigy G160 as soon as my spool arrives.
I found the thick wire to be easier to handle and almost impossible to short no matter how hard I pull.
Ronaldo
Oct 15, 2017, 10:18 PM
Registered User
I really like the 16awg. Feel I'm putting something real on and its much easier to sand and tin. The coolest unique benefit is it's so stiff u can tin it then skewer silicone multistrand and solder them inside the multistrand . Got to be the easiest to solder
The thickness allows you to organize the turns better and thereby get the most inductance per turn.
Last edited by Hummina; Oct 15, 2017 at 10:23 PM.
Oct 15, 2017, 10:29 PM
Ronaldo Nogueira
ronaldopn's Avatar
Exactly, forgot about how easy it is to remove wire insulation for soldering, just a small piece of emery paper and you're one.


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