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Old Dec 25, 2011, 03:08 PM
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Kv problems. scorpion 4035 and 4025 12N8P, rewind issue.

Previously, i rewinded a scorpion HK-4025 12N8P motor with 3 strands, 0.8mm wire, 10 turns delta, Kv is 930.

Today, i rewind a scorpion HK-4035, 12N8P motor, with 8 strands, 0.64mm wire, 6 turns delta, Kv is 1028.

Both my rewinded motor have higher Kv than original scorpions with same turns.

Motor is tested of Kv before rewind, and match the labelled Kv on the motor. So i assume magnet is fine. Everything keeps original except the wires.

Any thought why this is happening?
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Old Dec 25, 2011, 10:46 PM
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looks like everyones outta town
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Old Dec 25, 2011, 11:50 PM
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Same wind ABC x4?

Manuel V.
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Old Dec 26, 2011, 01:56 AM
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Originally Posted by manuel v View Post
Same wind ABC x4?

Manuel V.
i noticed, when i get rid of the original winding, that scorpion maybe has 1/4 or 1/2 turn cross winding to switch from one teeth to the next, such as from teeth 1 to teeth 4, and to teeth 7, then 11. Or maybe I am wrong, not sure. I guess this is to save some room at the bottom of the stator. While my winding does not, winding looks like as shown in the pic. besides that, winding is exactly ABCABCABCABC.

Of course, no shorts, motor runs perfectly. besides the nearly worn bearing, will replace as soon as i receive my order in a few days, finally, as well as new shaft.

for the 4025, 27% more copper cross section area than original
for the 4035, 50% more copper cross section area than original
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Old Dec 26, 2011, 11:52 AM
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modisc.

All wires across nut count.
Fore same Kv is necessary copy all half turns.(make a clone)
Parasite wire across nuten, count.

In one 6turn motor one 1/2 turn in any teeth count very mush.

Maybe Scorpion, do not have 6 wires nuten motor, maybe have 7.
if you rewind with real 6 turn wires,, has big differences.

Manuel V.
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Old Dec 26, 2011, 01:16 PM
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good. That is a reasonable explanation! But need to make sure of that! I am hoping anyone has similar experience!
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Old Dec 26, 2011, 05:00 PM
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As I recall, when I wound several of the Scorpion motor kits a few years back, I also tended to come out with a somewhat higher KV than you would infer from the stock count.

I recall asking the same question as yours in the Scorpion Kit thread in this particular subforum. I think I concluded that the difference was how I counted winds as opposed to Scorpion's definition, particularly the way to go from one tooth to the next.

I have forgotten some of the details, but that was an interesting thread in general.
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Old Dec 26, 2011, 05:49 PM
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Originally Posted by Alan Hahn View Post
As I recall, when I wound several of the Scorpion motor kits a few years back, I also tended to come out with a somewhat higher KV than you would infer from the stock count.

I recall asking the same question as yours in the Scorpion Kit thread in this particular subforum. I think I concluded that the difference was how I counted winds as opposed to Scorpion's definition, particularly the way to go from one tooth to the next.

I have forgotten some of the details, but that was an interesting thread in general.
Good to know someone has the same experience. Can you share the link of your thread? Thanks^^.
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Old Dec 26, 2011, 06:17 PM
Jack
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Could the difference be explained by the way you are measuring the Kv as opposed to how Scorpion measures it?

I know the quick and simple full throttle RPM divided by the voltage at the same moment it time is considered to be a "raw Kv" and close enough for out purposes. I think I've also read that it will be a little higher than the "real" Kv.

Jack
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Old Dec 26, 2011, 07:05 PM
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Jack
The difference is very little.
check my test:
http://www.rcgroups.com/forums/showt...777998&page=82

820 RPM/Volts vs 829 Kv with formula.

Manuel V.
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Old Dec 26, 2011, 07:49 PM
Jack
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Manuel,

OK, I had read those tests and forgotten how close they came out. That is only about a 1% difference.

modisc,

On your 930 and 1028 Kvs on your rewinds, what did Scorpion have on those for the Kv with the original winds?

Jack
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Old Dec 26, 2011, 08:05 PM
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Good to know someone has the same experience. Can you share the link of your thread? Thanks^^.
Here is the link to the overall thread.

http://www.rcgroups.com/forums/showthread.php?t=681251

Surprising to see how far it has fallen back.

At the time it was quite active.
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Old Dec 26, 2011, 10:40 PM
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Jack
The difference is very little.
check my test:
http://www.rcgroups.com/forums/showt...777998&page=82

820 RPM/Volts vs 829 Kv with formula.

Manuel V.
Exactly. If you are concerning about the voltage reduction I times Rm in the kv formula, yes, even when I is huge, the production will be quite small, since Rm is usually pretty small, such as 50mΩ.

So, Kv test even under some load will not be far from the actually Kv.
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Old Dec 26, 2011, 10:42 PM
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Manuel,

OK, I had read those tests and forgotten how close they came out. That is only about a 1% difference.

modisc,

On your 930 and 1028 Kvs on your rewinds, what did Scorpion have on those for the Kv with the original winds?

Jack
check out the pictures. 4035 is rewinded 6 turns delta, so the original is the 4035 800Kv, which is also 6 turns delta.
4025 is rewinded 10 turns delta, so the original is the 4025 740Kv, which is also 10 turns delta.
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Old Dec 26, 2011, 10:46 PM
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Originally Posted by Alan Hahn View Post
Here is the link to the overall thread.

http://www.rcgroups.com/forums/showthread.php?t=681251

Surprising to see how far it has fallen back.

At the time it was quite active.
that's quite a long thread^^. I rewinded another 4025 just now, with 6 strands 0.64mm, 8 turns delta, about 50% more copper again. standard ABCABCABCABC winding, no cross turns. so i am expecting roughly 1175Kv, according to my 940Kv 10 turns delta 4025.

I'll see what is the Kv soon
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