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Old Mar 26, 2014, 06:15 PM
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Question
Js 1490

First off I'd like to say thanks to Ron and anyone else involved in the sticky at the top of this forum. Damn good info for someone who doesn't know anything about winding a motor.

Bought a JS1490- 36mm outrunner, 1750kv ,6-pole(i think),24 turn(pretty sure), 5mm shaft motor 4-5 years ago. Used it in a Wemotec Midifan 90mmEDF unit in an F-18 for 3 years(summers). At a mile elevation where I live it had around 1100 watts and 62amps with 4-5amp 6s 25-30C packs. It would run hot but I found if i ran the fan for 30 seconds or so after every flight @ a low throttle setting, it would bleed a lot of the heat out. Worked great for 3 years, finally had a mishap and the fan went to the shelf.

This year I bought a new 11blade JetFan v.2 90mm ducted fan. I had heard these produced similar numbers to the wemo. Jumped my numbers up to 66amps and 1400watts. Did about a 1 minute test with no run down and she gave up the magic smoke. I knew it was getting hot and went to throttle it up but it was too late. It chittered and i knew that was bad and killed the throttle right then. But too late and a very small amount of smoke came out.

So i came here and found out some stuff about rewinding. My motor has 9teeth on the stator and 12 magnets. It came wired Delta. The wire in it was 23awg. They used 3 wires at a time when they wound it. If they were using the north to south winding method i couldnt see it and using 3 wires at a time seems to me, would make it difficult to keep track of it. They made 8 wraps with the 3 strands, so thats 24 turn right?

Went to a local motor rewinding place today and the guy was cool as hell and gave me this bunch of 22awg wire and wouldnt take any money for it. Tried to at least give him a $5 bill and he refused. Kudos to Lane Electric in Farmington,NM.

I plan to rewind this motor and would like your help on some stuff;

1. Did they wind it with 3 strands to save time on the assembly line? or is there a reason for this and I need to replicate that technique?

2. On the diagrams it shows a tooth being wired from the center out or vise versa and they only show 1 wrap. I will be doing multiple layers. When one layer is done do I simply start back toward the opposite direction or do i skip back and keep the slant of the wire the same? I imagine its the latter.

3. How does a 9tooth stator wound ABCABCABC have both a 6 and 12 pole possibilty? Or is that with 6 magnets and 12 magnet difference?

4. Anyone have the original tech notes on the little screamers/jet screamers JS1490?

Thanks
Steve
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Old Mar 26, 2014, 10:21 PM
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Answered #2. Have kept reading and saw a thread and the guy winding the motor kept winding back to the middle after reaching the end/outside.
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Old Mar 27, 2014, 08:24 AM
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Quote:
Originally Posted by Corelli View Post
First off I'd like to say thanks to Ron and anyone else involved in the sticky at the top of this forum. Damn good info for someone who doesn't know anything about winding a motor.

Bought a JS1490- 36mm outrunner, 1750kv ,6-pole(i think),24 turn(pretty sure), 5mm shaft motor 4-5 years ago. Used it in a Wemotec Midifan 90mmEDF unit in an F-18 for 3 years(summers). At a mile elevation where I live it had around 1100 watts and 62amps with 4-5amp 6s 25-30C packs. It would run hot but I found if i ran the fan for 30 seconds or so after every flight @ a low throttle setting, it would bleed a lot of the heat out. Worked great for 3 years, finally had a mishap and the fan went to the shelf.

This year I bought a new 11blade JetFan v.2 90mm ducted fan. I had heard these produced similar numbers to the wemo. Jumped my numbers up to 66amps and 1400watts. Did about a 1 minute test with no run down and she gave up the magic smoke. I knew it was getting hot and went to throttle it up but it was too late. It chittered and i knew that was bad and killed the throttle right then. But too late and a very small amount of smoke came out.

So i came here and found out some stuff about rewinding. My motor has 9teeth on the stator and 12 magnets. It came wired Delta. The wire in it was 23awg. They used 3 wires at a time when they wound it. If they were using the north to south winding method i couldnt see it and using 3 wires at a time seems to me, would make it difficult to keep track of it. They made 8 wraps with the 3 strands, so thats 24 turn right?
By using multiple strands in parallel they can increase the cross section surface are in the wire in small increments. As the turn count varies they can add or remove strands to keep the fill on the copper maximized. And also, three strands are more flexible than a single larger strand and more practical to wind with. And they can get away with stocking one size of wire (the most common strand size in multi strand winds and inexpensive motors is 0.25mm or so typically).

If your three strands are 23 AWG you can look that up in the wiki AWG table to see the cross section surface area. At 23 AWG they will be about 0.573mm or a little more and about 0.258 mm2 in area. So the total area in that wind is 3 x 0.258 or 0.774 mm2.

A well done single strand wind will have perfectly concentric and parallel turns with no twisted or crossing strands. And that will made the magnetic karma and harmony better than a multiple strand wind. So we amateur winders or "man knitters" usually try for a single strand wind.

And we would try to use a single strand that equals or betters that surface area so as to have the same or better current capacity.

Looking up the table from 23 AWG you can see that 19 AWG has an area of 0.653 mm2 and 18 AWG has 0.823 mm2. So you would want to try 18 AWG first to see if you can get the turns on with that and get that slight improvement in area too. And you'll find that a single strand of 18 AWG wind will not be easy as far as getting it in contact with the arms all the way around and getting the requisite number of turns on.

The turns decide the Kv as long as you do the same wind and termination. And your wind would be called an 8 turn wind as their are 8 turns on every arm if they got the winding work right. In Europe they use the "wires in a slot" count most of the time. So two adjacent arms with 8 turns would have 16 wires in a slot.

The ABC wind is really about the only choice for the 9 arm stator because of the odd number of arms on the stator. A 12 arm stator can give you more options for other winds.

If you want to pursue winding and there is a handy winding image calculator that can be downloaded here:

http://www.rcgroups.com/forums/showp...8&postcount=16

That will show you the wind you have now or want to have. The attached image shows the 9N12P ABC wind that you have now. The image is not exactly what you will see, it is intended to show the sequence the arms are wound in and directions (CW or CCW) of the turns. So you'll most often have something that actually looks quite different from the image.

Quote:
Went to a local motor rewinding place today and the guy was cool as hell and gave me this bunch of 22awg wire and wouldnt take any money for it. Tried to at least give him a $5 bill and he refused. Kudos to Lane Electric in Farmington,NM.

I plan to rewind this motor and would like your help on some stuff;

1. Did they wind it with 3 strands to save time on the assembly line? or is there a reason for this and I need to replicate that technique?
It saves money and makes it easier to wind as I said above. In higher quality motor a wider range of strand sizes will be found and they will try to get the combination of strand sizes and counts that gives the best fill. In inexpensive motors they use only one size (the ubiquitous 0.25mm wire) and add strands until the workers cannot get any more on.

Quote:
2. On the diagrams it shows a tooth being wired from the center out or vise versa and they only show 1 wrap. I will be doing multiple layers. When one layer is done do I simply start back toward the opposite direction or do i skip back and keep the slant of the wire the same? I imagine its the latter.
That is the deal about showing you the sequence and direction and not the actual arrangement. In a typical 8 turn wind you would start on the inner end and wind four turns out and four back for end turns. Or maybe 6 turns out and 2 turn back if there is not room in the bottom of the "V" for two layers on adjacent arms. This is where you become a man knitter, go into a trance, and just figure out the details as far as the best with to get the needed turn count and best copper fill.

Quote:
3. How does a 9tooth stator wound ABCABCABC have both a 6 and 12 pole possibilty? Or is that with 6 magnets and 12 magnet difference?
The 9N stator is a little unusual in that you wind it the same way for 6 or 12 magnets. The difference would be that the Kv would change with the magnet count change. And the work for the ESC gets easier as the magnet count drops lower because the number of commutation cycles is reduced. ESC have their limitations and it is normal for magnet counts to drop as Kv's get higher.

Quote:
4. Anyone have the original tech notes on the little screamers/jet screamers JS1490?

Thanks
Steve
I don't have any experience with those motors but I think there are others here that do and that will chime in.

There are some other helpful tools. for example, if you think you want to change the Kv there is a calculator that will use the details from a motor to predict a table of turn counts and the resulting Kvs.

Jack
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Old Mar 27, 2014, 10:19 AM
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Thank you. After reading for the last couple days and seeing some of the "discussions" with the original manuf. of this motor I was worried I'd get a reply at all

>>>There are some other helpful tools. for example, if you think you want to change the Kv there is a calculator that will use the details from a motor to predict a table of turn counts and the resulting Kvs. <<<

Where is this calculator?

I would in fact like to lower the kv a touch. @1750 in a wemo fan it was decent power but not amazing. Altitude affects fans a lot, in my experience. Going from 1100 watts to 1500 would have been nice. But this is a 5oz. outrunner and heat dissapation is what it is. I'm hoping with a Man Knitter wind I can increase its heat properties. At the same time I'm, wanting to lower the KV maybe 50-100. With new , better and more winds in this motor if I can see a 1250-1350 watts range and manageable heat management(lol)I will be happy.

I understand I need more winds to lower the KV. I haven't attempted a wind yet. I'm going to the supply store today and will pick up parts for my jig. Hopefully, tonight I will do at least one tooth and see how many I can get of this 22awg on there.

Thanks again
Steve
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Old Mar 27, 2014, 10:50 AM
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Read your reply again. So with 3 strands and 8 wraps this motors 1750kv is dictated by the 8 winds? Its not 24 like I assumed. So if I take my 22awg and do 1 strand and get 24+ winds on there, I will reduce that kv to something like 600?

If I read you right, I should get 18awg and try to do around 9-10(1-2 more, lowering my kv like i want)winds with a single strand.

Steve
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Old Mar 27, 2014, 12:27 PM
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Keep in mind Steve
The Kv motor-constant says nothing about a motors max.power, max.current and rpm

Vriendelijke groeten Ron
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Old Mar 27, 2014, 01:15 PM
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Quote:
Originally Posted by Corelli View Post
Thank you. After reading for the last couple days and seeing some of the "discussions" with the original manuf. of this motor I was worried I'd get a reply at all

>>>There are some other helpful tools. for example, if you think you want to change the Kv there is a calculator that will use the details from a motor to predict a table of turn counts and the resulting Kvs. <<<

Where is this calculator?
You can download it here:

http://www.rcgroups.com/forums/showp...&postcount=260

It is a spreadsheet and the details on what to run it with are there too. For your motor you want to use the Simple Turn Calculator or V2 version of that. Turn Calculator 5 and 6 are for 12 are stators and need an input from a motor that was wound dLRK (Distributed LRK) to set up the turn counts for all the winds it will do.

If you cannot run a spreadsheet for some reason, post the info on your motor and I'll run it and post a screen shot for you. The attached screen shot is from simple Turn Calculator V2 and is for a 10 turn, Delta terminated, 10000 Kv motor.

If you can measure your Kv it is best (more accurate predictions) but otherwise you can just enter the Kv it was advertised to have had.

Quote:
I would in fact like to lower the kv a touch. @1750 in a wemo fan it was decent power but not amazing. Altitude affects fans a lot, in my experience. Going from 1100 watts to 1500 would have been nice. But this is a 5oz. outrunner and heat dissapation is what it is. I'm hoping with a Man Knitter wind I can increase its heat properties. At the same time I'm, wanting to lower the KV maybe 50-100. With new , better and more winds in this motor if I can see a 1250-1350 watts range and manageable heat management(lol)I will be happy.

A lower value for the Kv will give you fewer RPM and drop the input power with the same load. If you want to increase the input power you would want a higher value so the motor is trying to run faster. And that will increase the input power too. And the faster turning impeller will increase the thrust and performance I would think.

If your 50 oz./142g motor will handle an 1100W input power now, that is surprising. For props, on average quality motors, we consider that the average motor will be able to handle 3W for each gram of motor weight. That would make your motor a 3 x 142 = 526W motor. And you are running it at more than double that and it is surviving, right? That is pretty amazing.

Better quality motors, and yours might be one of those, will get up around 4, 5 or even 6 Watts per gram with props on them. And you are up around 7.75W per gram now.

But you're on your own as far as how hot it gets and that. I can understand how fan jet motors would have better cooling from being mounted in air stream in the inlet tract. I guess that dissipates a lot of heat.

Quote:
I understand I need more winds to lower the KV. I haven't attempted a wind yet. I'm going to the supply store today and will pick up parts for my jig. Hopefully, tonight I will do at least one tooth and see how many I can get of this 22awg on there.

Thanks again
Steve
More turns will lower the Kv, fewer turns will raise it. So you want to take a turn or so off to get a higher Kv. The load will increase, the input power and RPM will go up, and so will the heat and power.

Jack
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Old Mar 27, 2014, 04:46 PM
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Once again, thanks for the replies.

I bought a floor flange with a 3/4" IPS fitting in the middle of it. A 3/4"X1/4" IPS bushing. A 1/4"X6" nipple, a 1/4"X1/8" bell reducer then an 1/8"X1-1/2" nipple. Shown in the pic. I'll screw that to my work bench and wind from it.


With me punching in 1750kv as a comparison starting point based off what the manuf. claimed,... assuming my 8 count was right, if I up the turns to 9 it will lower the kv to 1550. This is an apple to apple comparison based off of whats and amps and kv already introduced. That being said maybe the watts and amps after my winding will be useable.

So now the rubber meets the road. Ill have to see how the winds work. I'm thinking first I'll see if a double strand wrapped 9 times will fill a tooth and go from there. Maybe I will have to get some 18awg.

I know on the forums this can be a loaded question; what do you think? Does it sound like my assumptions are good enough up to this point to warrant a try at winding?

Steve
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Old Mar 27, 2014, 07:40 PM
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Quote:
Originally Posted by Corelli View Post
Read your reply again. So with 3 strands and 8 wraps this motors 1750kv is dictated by the 8 winds? Its not 24 like I assumed. So if I take my 22awg and do 1 strand and get 24+ winds on there, I will reduce that kv to something like 600?

If I read you right, I should get 18awg and try to do around 9-10(1-2 more, lowering my kv like i want)winds with a single strand.

Steve
I missed the question here earlier. But yes, it is the 8 turns that counts. On some stators with even numbers of arms that are wound in adjacent pairs, you may find different counts on two adjacent arms in a pair. Like 8 turns on one and 7 on the other and that would be called a 7.5 turn wind.

But 9 arm stators will all have the same number of turns on every arm as far as I know.

I ran STCV2 for your motor with the 1790 Kv it was supposed to have and the 8 turns and Delta termination you found. The screen shot of that is attached. And as you said, 24 turns would drop the Kv to around 600.

So your next choice for a turn count with a higher Kv would be 7 turns for a 2046 Kv. As long as it is the wire you have, try three strands of the 22 AWG and see if 7 turns of that will fit. If it does not, fall back to two strands and try that.

I think it will serve you well to go ahead and do one of the winds and then get a good accurate Kv measurement. Do you have a tach? All you have to do is measure the full throttle RPM and voltage at the same moment in time and divide the RPM by the Volts. That is called a "raw" Kv and it is accurate enough for our needs here. Then you can redo the spreadsheet with the accurate Kv and really narrow down the results on future predictions.

Jack
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Old Mar 27, 2014, 07:55 PM
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Quote:
Originally Posted by Corelli View Post
Once again, thanks for the replies.

I bought a floor flange with a 3/4" IPS fitting in the middle of it. A 3/4"X1/4" IPS bushing. A 1/4"X6" nipple, a 1/4"X1/8" bell reducer then an 1/8"X1-1/2" nipple. Shown in the pic. I'll screw that to my work bench and wind from it.


With me punching in 1750kv as a comparison starting point based off what the manuf. claimed,... assuming my 8 count was right, if I up the turns to 9 it will lower the kv to 1550. This is an apple to apple comparison based off of whats and amps and kv already introduced. That being said maybe the watts and amps after my winding will be useable.
OK, but the higher turn count/lower Kv will drop the input power. I thought you said earlier you wanted to increase it the input power?

Imagine it this way if it helps. With the higher Kv, for a given throttle setting, the motor will be trying to turn the impeller faster. And that will take more "effort" to do that and the input power goes up.

With the lower Kv, for a given throttle setting, the motor is finding the impeller easier to turn because the RPM is lower and the input power goes down.

Quote:
So now the rubber meets the road. Ill have to see how the winds work. I'm thinking first I'll see if a double strand wrapped 9 times will fill a tooth and go from there. Maybe I will have to get some 18awg.

I know on the forums this can be a loaded question; what do you think? Does it sound like my assumptions are good enough up to this point to warrant a try at winding?

Steve
Yep, I think you're ready to give it a try, either 7 or 9 as you decide. And it is pretty easy to keep two strand side by side and orderly. Easier than three or more for sure. If you find the turn count and Kv you like and there is still some room for larger wire you'll have the option of one larger strand (maybe) or three smaller strands (maybe).

I think we all find our own niches for how we do the work. The stand is interesting but I don't think it would work for my tired old hands and weaker fingers. I made a thing I call the 3rd hand and I control the tension on the wire as I pull it through that and onto the stator. I have a snug fitting dowel in the stator as a handle and can twist and turn the stator to keep the wire coming straight at me.

You can see the 3rd hand in action here:

http://www.rcgroups.com/forums/showp...00&postcount=4

Jack
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Old Mar 28, 2014, 12:44 AM
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Well thats done. Kinda like the first time I had sex. Not too good but even by the time I was finishing, i thought i might be better next time.

I checked it with the meter to make sure none of the leads were grounding on the stator. The jig of mine was so so. And it scratched some of the insulation off the top ends of the winds it touched when I wasnt careful and pushed too hard on it. I made sure the bare wire isnt going to touch anything.

It's late so I will get it wired up tomorrow and see whats what.
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Old Mar 28, 2014, 11:26 AM
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Lol, it works. Really thought I had about a 50% chance of it even turning. I only did a basic hook up with a 3s(uncharged) battery just to check it. Still need to work on getting the insulation off my leads and making a good set of leads. The stator wants to sit up in the bering shaft so i need to clean up the wire terminals some.

No idea what the KV will be or if it will come close to what i want. Did get a message from the guy who manufactured the motor(not the company that sold them) and he said they were all originally 22awg dual strand. Weird cause mine was 23awg tripple and now is 22awg double, funny. Sent him another message asking what the turns were because after winding this motor myself, I think I mis counted when I took the wire off

Have to take the kids to town and do some errands but will finish up the leads and get the motor wired properly and put it back in the fan and back in the plane and get some 6s numbers some time today. Still give myself about a 10% chance of total success with this.
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Old Mar 28, 2014, 02:30 PM
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Hi, I just rewound a js1400 70mm version, It had 3 strands of 22 with 3 turns and I rewound it with 18g and 5 turns.

So far numbers look good I ran it in a het 6904 on 5s not fully charged and it pulled just under 40a, might be a good candidate for a cs70 rotor on 6s.

I might even rewind it with 4 turns.

I don't remember the stock #s in the 6904, I think it was 80a-90a+ on 4s.

Happy flying.

Shane M.

PS: If anyone is thinking about rewinding an old Js1400 or 1490, Go for it! They come apart really easily, very little epoxy on the stator and it comes right off with just a little heat and the windings are loose without good copper fill.

Although 18awg is a little stiff its not that hard to work with, A small prop cut to press the wire around the corners and some skewers to use as wedges.
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Old Mar 28, 2014, 02:41 PM
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Nice job on the wind! Don't sell your self short on your chance of success!

One tip I have is from the look of your first pic its the same issue I had on my first go round.

The wires are to tight to the bearing tube so when you go to assemble the motor, the wire hit where the bearing tube flares at the base.

A simple way to avoid this is to slide a dowel rod thru the stator and then wrap electrical tape on the dowel to simulate the step on the bearing tube.

Great work , looking forward to some initial #s

Shane M.
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Old Mar 28, 2014, 07:09 PM
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What Shane said!

That was one I learned the hard way when I wound an iPower MT4006 kit motor stator. I couldn't even get the bearing tube fully seated into the stator until I got the transit runs out of the way. And learned it the hard way so I had to wind it again!

When the stator was pushed all the way up against the collar the collar held the transit runs back.

jack
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