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Old Sep 19, 2012, 10:06 AM
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Rewind hextronik 5gram 2000 KV motor

I have 2 of the HXM1400-2000 motors with broken wires. I opened up one of the cans but was unable to solder the broken wires because the wire was too short. So I am in trying to rewind this motor. The original configuration of this motor was a 12 pole stator with 16 magnets wound with 2 strands of 37 gauge with 17 turns (ABC wye). I only have 30 gauge and tried rewinding with 8 turns but was unsuccessful. I think I can only get 5 or 6 turns on each tooth. What can I expect in turns of KV and torque relative to the original configuration ? For example, using the same 4X2 prop, would I expect to get roughly 3 times the KV and 1/3 the torque from the original ?
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Old Sep 19, 2012, 10:50 AM
Jack
USA, ME, Ellsworth
Joined May 2008
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New Kv = Constant / New Nr.Turns

Constant = Old Kv * Old Turns = 2000 * 17 = 34000

New Kv = Constant / New Nr.Turns = 34000 / 6 = 5666 (New kv)

You're about right on the new Kv but it will be unlikely to be able to turn the old prop vwithout buring up. As the Kv goes up the prop size needs to go down.

And depending on your ESC, it might have some trouble keeping up with the new permutation rate for the much higher Kv.

If you need some smaller wire here is a source:

http://www.techfixx.com/

Jack
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Old Sep 19, 2012, 11:22 AM
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United States, NJ, Edgewater
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Thanks for the info Jack.

I did buy the 30 gauge wire from techfixx on ebay. I just didn't want to invest more money to fix a $8 motor. Also, the 37 gauge wire is too delicate for me to work with. I think I will try the 5-6 turn setup and if the motor gets too hot I will drop it to a 1S battery or a smaller prop. I hope I can make these motors usable again!
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Old Sep 19, 2012, 11:46 AM
Jack
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I know what you mean about the finer wire. I have some 31 AWG I have not used yet and that is as fine as I want to go.

I just rewound some 24 gram Blue Wonders and used 26 AWG, was not able to get the turns I wanted with 24 AWG. With ABC being the only option and already having a Wye termination, it meant I was out of options for keeping the Kv down to the 1300 or so I wanted.

Jack
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Old Sep 21, 2012, 09:26 AM
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After 3 tries, I finally got the stator rewound with 6 turns. some of the green enamel covering the iron core did come off. I hope I don't have any shorts! I will give it a try on 2S (with throttle management) this weekend. I have no idea how some people manage to get more than 7 turns with 30 AWG wire on this little thing.
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Old Sep 23, 2012, 09:14 PM
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My first motor rewind was successful! It was very satisfying to watch the motor run for the first time. The bads is the motor gets way too hot on 2S. I will be ordering a 1S esc and some 3x2 props.
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Old Sep 23, 2012, 10:18 PM
Jack
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Congrats! So now you are addicted!

So the Kv is too high for the prop and that is why the heat. And props just don't get small enough, right?

Was the ABC wind terminated Wye (there was a small bundle with the ends of the three phase soldered together)? If so, an ABC wind terminated Wye is as low a Kv as you can get out of a ABC wound motor.

I just rewound a 19 gram motor, also 12N16P and an ABC wind, my smallest ever rewind. I did that with three strands of 32 AWG. It was terminated Wye and finished up with a 2300 Kv. It is doing fine though and I can spin a 6030 or even a 6050 slow fly on 2S with it. It was an AX-1806N 2500 Kv motor originally. I think I could have gotten a few more turns on it.

It was a real PITA to strip the ends on the 32 AWG wire and get the Wye bundle and terminations made. It came with a small circular PCB for a winding terminator board and I used that and put stranded wires on for the motor leads.

I just can't imagine rewinding 5 gram motors. If the work was linear it would be four times as hard as doing a 19 gram moto!

Jack
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Old Sep 24, 2012, 07:58 AM
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Yup. KV was too high as excepted and I was trying to spin a 4X2. I am hoping I can still spin the 4X2 on a 1S but will buy the 3X2 props just in case its still too much current. Next I'll have to find a plane to build for this motor!

Yes, the termination was Wye as a delta termination would give 1.7 times the KV. I was also thinking of doing an LRK wind but that would require me to re-position the magnets. I probably should have started with bigger motor for a first rewind, but none of them were broken :-).

I just can't imagine rewinding 5 gram motors. If the work was linear it would be four times as hard as doing a 19 gram moto!

rewinding the 5 gram motor is only more work if you put the correct number of winds on them. If you cheat and only put 6 turns, its not that much work!

I'm still debating what to do with my other broken 5 gram motor. I don't want another 5000 KV motor. I think I'll open up the can and try to solder the broken double stranded 37 AWG wire to a 30 gauge strand. If that doesn't work out, I'll buy some 34 AWG wire and try to get 12-14 turns with a single strand. I don't think I want to mess with anything smaller than that.

I just rewound a 19 gram motor, also 12N16P and an ABC wind, my smallest ever rewind. I did that with three strands of 32 AWG.

On your 19 gram motor, why did you use 3 strands of 32 AWG wire instead of a single strand of something bigger ?

-vinnie
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Old Sep 24, 2012, 08:59 AM
Jack
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Quote:
Originally Posted by vinnieg View Post
..<snip>...

I just rewound a 19 gram motor, also 12N16P and an ABC wind, my smallest ever rewind. I did that with three strands of 32 AWG.

On your 19 gram motor, why did you use 3 strands of 32 AWG wire instead of a single strand of something bigger ?

-vinnie
I had read somewhere that the original wind on that was 3 strands of 0.2mm (32 AWG) wire but when I got the motor someone had already tried to rewind it with 24 AWG. That only had 8 or 9 turns and was very disorderly so I started over.

So I decided to see how multiple strand winding goes and tried three x 32 AWG because I had that wire. The original amount of surface area would have been 3 x 32 AWG or 0.096 mm2. That would be a little less than one strand of 27.5 AWG or so and I did not have any of that.

I tried a test wind with some 26 AWG, also looking for a higher turn count to drop the Kv, and that ran out of room too soon too. so I tried the 3 x 32.

As far as the mechanics of winding, I used my "3rd hand" accessory and that really made the multi strand process go very well. I laid the three strands in that side by side and flat, put a light sliding strain on the group, and that let me pull out a 12" or so length (strands were about 45" or so).

I had put a small dowel through the motor for handles and was able to keep the three strands flat and side by side and just roll the stator arms up the wire without any turning or twisting. The first layer went on as 5 turns with 15 strands laying side by side and absolutely flat. The second layer went on almost as neatly and when I got two layers on (10 turns) I decided to try that. I actually went to about 10-3/4 turns in the process of the transit to the next arm.

But looking at it now I think I could have gotten a third layer of turns on and now wish I had tried to do that. Oh well, next time...

I terminated it Wye, put some temporary bullets on it, and when I fired it up it was running beautifully. The bearings sounded like a washing machine full of rocks but that was another issue...

A no load showed a Kv of 2279 and it was pulling 1.02A. I tested it with my two smallest props and maybe it is OK at that Kv on 2S as I am not a compulsive full throttle flyer. I used a 3S A123 pack so the voltages are a little higher than a 2S LiPO would produce:

GWS EP 6030 (not full throttle run - I chickened out on the RPM limit!)
19 seconds 3/4 throttle +/- averages
8,794 RPM, 9.48V, 2.02A, 19W temp 83F to 84F stabilized
Numbers were wrong, see post below for corrected info

GWS RS EP-6050 SLOW FLY
30 second full throttle averages
10,017 RPM, 7.89V, 9.85A, 78W temp 77F to 91F and stabilized

Numbers were wrong, see post below for corrected info

I am happy with those numbers. 3.9W per gram on that slow fly prop and it is not overheating at full throttle, that cries out to be used. Like you, now I need to build something!

Jack
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Old Sep 25, 2012, 10:11 AM
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United States, NJ, Edgewater
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I'm going to have to try out your "3rd hand" accessory when I rewind with multiple strands.

regarding your rewind, I like the 6x3 prop pulling 2.02A. I personally like low and slow flying planes with long flight times. Do post when you end up putting this motor on a plane. And thanks for the help!
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Old Sep 25, 2012, 06:36 PM
Jack
USA, ME, Ellsworth
Joined May 2008
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Hmmm, that 2.02A makes me suspicious that I have made an error in my notes or in reading the eLogger data. That sound like it is way too low. But I will follow up on it.

But you've got very similar tastes in flying to mine. I fly alone for the most part, at a rough field location, hand launched and most landings are a gentle flare/stall/flop into the weeds. I jokingly refer to my flying location as the Geezerville Aerodrome.

As a guy new to these smaller stators, I think I am finding that the use of multiple strand winds on them can let you get more wire into the wind. I have been replacing multistrand winds with single strands on almost every wind I've done until now. When the wire got bigger and stiffer I used a two strand wind on a 35mm stator and it worked good. It was very hard to get 17 AWG wire to conform to and lay flat on the arms but two smaller and equivalent in area strands did well.

But now I'm finding that the multiple smaller strands lay on the arms nicely and are more compact when you get down to these smaller motors. Using multiple strands was thought to be a bad thing as it raised issues of strands crossing and not being as symmetrically arranged. And that disrupts the harmony or karma of the magnetic fields of something like that.

But using the 3rd hand and rolling the turns on with less twisting is going well. I would have to have two or more motors and try them both ways to be sure but for right now, if I look at it purely from the amount of copper I can get in and if using the smaller strands improves that, I'll give it a try.

When I do the multiple strands, I tie the strands together with an overhand knot at the starting end (that will be scrapped eventually) and lay the strand flat and side by side as they come through the 3rd hand. And that and the business of rolling the stator arm up the strands as I work really improves neatness of it. After each half turn I gently nudge the strands together before I cross the top or bottom of the arm and that avoids crossing turns.

Jack
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Old Sep 26, 2012, 04:11 PM
Jack
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Joined May 2008
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I screwed those numbers up somehow. I ran that test again and got this:

GWS HD EP-6030
32 seconds at full throttle
12,857 RPM 9.08V, 5.64A, 51W
temp rise 72F to 75F during run, peaked and holding steady at 75F

So that one will handle more prop than that, especially if the throttle is on and off as you fly.

I also did the slow fly prop again too, on that I had to use the throttle to limit the RPM as it started fluttering

GWS RS EP-6050
22 seconds RPM limited to below audible fluttering
9,369 RPM, 8.84V 7.44A, 66W no temp taken, motor barely warm

Jack
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Old Sep 26, 2012, 09:13 PM
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these numbers still sounds good. You can easily do a 7x3 prop on it. The fun part is watching it on a plane.

As for me, I just put in the order for a 1S esc. Now I find myself looking around for a broken cdrom drive. Even though its cheaper to buy a brand new motor, I just want to satisfaction of rebuilding a cdrom motor for rc use. This stuff is definitely addictive!
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Old Sep 27, 2012, 06:36 AM
Jack
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It is an amazing thing. I skipped the CD-ROM motors phase, that was just ending as I got into all this. But I still like old CD and DVD drives too because I get two free 3mm shafts out of every one. Almost every old computer goes to the graveyard with at least two 3mm shafts and a CD-ROM motor in it!

You know about Strong Motors? He still has some of the bits and pieces that made for some of the best CD-ROM motors. Don (bz1mcr) is a regular here on the forums and a gentleman to deal with too.

http://www.strongrcmotors.com/

Jack
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Old Sep 27, 2012, 07:38 AM
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yes.. I've been thinking of buying the "Curved N50 set for single 20" for $2 + shipping. I just need of find a motor to put these magnets in.

I'm hoping that the motor rewind side of the hobby will keep me entertained in the winter.
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