Thread Tools
May 22, 2010, 08:02 PM
jackerbes's Avatar

EMAX BL2210/30 wire size for rewind?

I toasted a EMAX BL2210/30 a while back and want to see if I can rewind it. I've done one larger motor, not sure if I can do this little guy or not but for the cost of a little wire makes it worth a try.

Here are the specs on the motor:

Emax BL2210/30 Rpm/V Outrunner Brushless Motor
Model: BL2210/30
No. Of cells: 2-3x Li-Poly
RPM/V: 1450
Max. efficiency current: >75%
No load current / 10V: 0.5 A
Current capacity 2210/30 16.5 A/60s
Dimensions: 22x10 mm
Shaft diameter: 3 mm
Weight: 45 grams

It was originally wound with 13 turns, three strands of wire that probably 31 guage wire. The strands measure 0.009"/ 0.23mm.

The surface area of a single 31 gauge wire is 0.0404 mm2 and that had three strands. Would I want to shoot for a single strand of about three times that area or a little larger? Or about 0.121 or so? If so, 26 gauge at 0.129 mm2 would be my guess. Is that how you would figure out the wire size?

The stator is pretty dark and toasted looking, it was originally coated with the green shiny stuff but I'm not sure if that is going to survive cleaning up.

I have it soaking a denatured alcohol now to get the epoxy and tar(?) off but am not sure if it will clean up well or not. If the stator should need to be re-coated to protect the windings, what is good to use for that?

Thanks for any help or suggestions.

Sign up now
to remove ads between posts
May 23, 2010, 01:21 AM
Normally soaking it in alcohol also damage the green epoxy coating as well. If you did that you must remove all of the epoxy and use another isolating material when winding. Do a search for a picture with a winding with the (paper like) material for isolation to see how to do it. (I am not on my own computer now, so don't have links)

To do 13 winds per tooth you can use 0.5mm single strand wire. (24awg)
May 23, 2010, 06:26 AM
jackerbes's Avatar
Thanks for the help Sven.

I think the dark tar like stuff that was on stator was the melted and burned insulation from the original wiring. It was very dark and quite hardened and even had some wire strands trapped in it where the wires had broken when I was taking the old windings off.

I didn't realize that the green stuff was epoxy too. But if that's the case I could mix up some thin epoxy and paint it with a couple of coats of that couldn't I?

May 23, 2010, 12:17 PM
It is a different epoxy than what you use as glue. I did try that before and was not successful. The problem is that on the sharp corners of the stator the epoxy flow away to expose the sharp edge. That is where you want the isolation instead of on the flats where it does not matter so much. Best is to use the thin isolation paper (Kevlar).
May 24, 2010, 07:26 AM
jackerbes's Avatar
OK, I see what you mean.

I can get the paper and will try that, I still have to get some wire too. I've got the stator pretty well cleaned up and there is quite a bit of bare iron exposed from the cleaning.

Jun 01, 2010, 11:16 AM
jackerbes's Avatar
Originally Posted by Swen View Post
It is a different epoxy than what you use as glue. I did try that before and was not successful. The problem is that on the sharp corners of the stator the epoxy flow away to expose the sharp edge. That is where you want the isolation instead of on the flats where it does not matter so much. Best is to use the thin isolation paper (Kevlar).
Good advice, I should have taken it to heart. Instead I learned something the hard way.

I made a small fixture to align the laminations and painted the stator with a coat of epoxy to put it back together. You can see that in the first two photos. The laminations were well bonded with the one coating of epoxy on the outside and have stayed together nicely.

I experimented with wire sizes for a wind and using 13 turns of 24 AWG in two layers of 5 turns over 8 turns produced a nice looking wind. I checked a test winding and it was not shorted to the stator so I thought the epoxy coating was going to be enough to insulate the stator from the windings.

So I proceeded to wind all 12 windings. That produced the nice looking rewind seen in the third and fourth photos.

But when I got all done and started checking it with an Ohm meter every single winding was shorted to the stator. Grrrrr!

So now I am going to start over again and put some insulation over the top and bottom of the stator arms where the windings cross those sharp corners you warned me about.

I don't have any Kevlar but I have some Tyvek CD-ROM sleeves that I can cut insulation strips from. I think that will work for insulation if I wrap it around the stator arms where the wire turns double back. But I'm going to test it a little before I do the whole thing again.

I'm using the good quality MicroDan wire and the insulation on the wire shows very little visible damage in the places where it was shorted out to the stator. In only one or two spots is there any visible bare copper. But it is obvious that there were short on every winding and it had to happen at the sharp corners that Sven warned me about.

It was good winding practice if nothing else. And a total waste of six 33" lengths of 24 AWG wire.

Last edited by jackerbes; Jun 01, 2010 at 11:21 AM.
Jun 01, 2010, 11:52 AM
Here is a picture from elsewhere on RCG. If you do this, success is very possible.
Jun 01, 2010, 12:50 PM
jackerbes's Avatar

Thank you very much! I think that looks like the Tyvek paper too so that should work.

If you have a link to the thread where that was posted it looks like it would make interesting reading. But if not, you've got me headed in the right direction again.

Jun 01, 2010, 01:37 PM
On the 2nd picture it says "mylar" which is the material used.
Sorry, I don't have the link, just collect pictures. (can't read )
Jun 19, 2010, 10:54 AM
jackerbes's Avatar
I played around with Tyvek (didn't have any Mylar) and trying to get this stator insulated. But I just kept generting shorted turns or things that otherwise did not work.

I finally read about using the Loctite 410 rubberized CA adhesive for insulating stators and got bottle of that. That stuff turned out to be very good.

I cleaned that stator up a little (the laminations were down to bare metal), deburred all the sharp corners where windings crossed with an abrasive burr, and put two coats of Loctite 410 on all the edges where the turns crossed them.

I put the laminations on a wooden dowel and bound them together with scrap wire temporarily to keep them together and aligned while I got first coat of the 410 on. Then I cut the wires off and put the second coat on. The Loctite 410 serves as an adhesive to keep the stator toether nicely too.

I did a couple of test winds and found the insulation was working very good as far as putting an end to all the shorting issues. In the course of testing the winds I decided to do a LRK six tooth wind.

So I finally have the stator from the back plate motor that probably should have been thrown away rewound.

I got 18 turns of 24 AWG on in three layers (7-6-5) and intend to terminate it Star or Wye.

Will follow up with some more details after I get this going...

Jun 21, 2010, 11:52 AM
jackerbes's Avatar

BL2210/30 - It is a runner!

I got this motor back together and tested it today, it actually turned out pretty good I think.

I think I now understand the disdain or dislike that some seem to have for rewinding the backplate motors. Getting the stator remounted, getting the windings terminated and fitted into the space available, and getting the motor leads out of the motor is not much fun.

The stator had a small keyway in it but there was no matching keyway on the outside of the bearing tube (the stator had been epoxied to the tube).

I used a Dremel tool and ground a small groove on the outside of the bearing tube with an abrasive cutting disc, then slid the stator into place on the bearing tube and aligned the keyway and the groove. I used a short piece of .047" piano wire as key to lock the stator and bearing tube together.

The stator is a light friction fit and the key is holding so far, with the motor assembled the stator cannot back off of the housing so I think it will stay together.

In the end I brought the three single strands out of the backplate through separate openings and soldered stranded pigtails on outside of the motor. Not pretty, but it is working.

The motor was wound LRK with three 46" lengths of 24 AWG. It took 18 turns in 3 layers (7-6-5) and was terminated Star or Wye.

I spun it up on the drill press at a few hundred RPM and got readings of 0.55V AC on all three windings. I shorted the leads and the cogging was smooth and even so I decided to play the "You Bet Your ESC You Got it Right" game.

It powered up very nicely on a 3S A123 pack, gave me a little tune, and two click of throttle had it starting easily and run smoothly. No smoke, no funny smells!

I ran a couple of No Load tests and the eLogger reported:

11,551 RPM, 0.61A @ 9.89V, Kv = 1168
11,551 RPM, 0.43A @ 9.84V, Kv = 1174

I was impressed that I got the same peak RPM in two tests.

I put couple of slow fly props on (one at a time of course) for tests and got the following numbers:

GWS RS 8060 = (partial throttle) 5,683 RPM, 3.83A, 9.37V 36 Watts

Great Planes 10X4.5 SF 3S A123 = (partial throttle) 3,769 RPM, 3.95A, 9.49V, 37 Watts

Great Planes 10X4.5 SF 2S A123 = (full throttle) 4,251 RPM, 8.84A, 5.93V, 52 Watts

I ran for 30 seconds or so with the 10x4.5 and checked for heating and the back plate was not even warm.

Jun 22, 2010, 09:34 AM
Registered User
Looks like you got another good one there. For a beginner at this you seem to be doing pretty good. If you can't tell....I'm envious

Jun 23, 2010, 09:46 AM
jackerbes's Avatar
Originally Posted by Slow_Buzz View Post
Looks like you got another good one there. For a beginner at this you seem to be doing pretty good. If you can't tell....I'm envious

Even a blind pig can occasionally find an acorn! Actually, with the help you get here it is just a case of a little learning curve and working out the details. I think I am doing it for two reasons. I find it entertaining, and the motors get better than they were. I think you'll find it the same way.

The part that is still sort of a mystery to me is what I'll actually wind up with. The BL2210/30 was bought as a 1400 Kv 2S to 3S motor rated for 12A continuous and 16.5A peak/60. But I think those ratings were very optimistic, especially for 3S.

When it burned up on me I was using it on 3S LiPO and it only took a short period of time (two 15 second or so runs) at 16A or so so for it to overheat and become damaged beyond further use (stuttering on starts, smelling funny, and a smoking end probably just moments away).

So I'm sort of "sneaking up" on the rewind as far as seeing what it will do.

Yesterday I ran it at 3S voltages a little and I'm further encouraged that it will be a useful motor. I used the Great Plane 10 x 4.5 slow fly prop again because I wanted to test the upper end limits of the motor.

I used a 12V battery and test runs at 10A and 12A to see how hot the motor would get and also to see if the heat would stabilize at a non-damaging level. The peak readings on the two runs are:

10A run - 4,903 RPM, 9.64A, 11.9V (115 watts)
12A run - 4.786 RPM, 12.3A, 11.8V, (145 watts)

On both of those runs I used thermistor/DMM to monitor the temperature rise in the base plate/back of the windings area of the motor a set a self imposed arbitrary limit/stopping point for heat rise of 55C/130F or so. That would be the temp where the base plate would get too hot for me to keep my finger on it and it would also be getting hot enough to threaten the motor.

On the 10A run the motor plate warmed to a stable but safe temperature and stopped rising. On the 12A run the motor plate got hotter, almost to the too hot to touch limit and it was still rising slowly at the end of the run.

But I noticed something interesting in graphing the data that was not apparent to me as I did the runs. It looks like the last 2A to 3A or so of throttle increased the RPM very little when I increased the throttle to get the 10A and 12A readings during the test. So I think in flight there would be little or no apparent increase in performance or speed for the last four or five "clicks" of throttle movement.

I don't know propeller theory for planes but it looks like there is a point in propeller RPM where adding more power produced little additional power. Maybe is is something like the hull speed on a boat where additional power adds little additional speed.

It looks like this motor, on 3S, will be a good reliable 100 to 150 Watt motor with this prop. I'm going to test it a little more with DD and smaller SF props on 2S and 3S A123 packs just to get some more numbers on it as to where and how I can use it. Then I need to put it on something...

Now I'll also take the trouble to open the motor up again and clean up the way the windings are terminated and brought out of the back plate. I need to do that because as it is now, movements of the motor leads moves the windings a little too and could create a friction point where the magnet housing could rub a winding.

Jun 23, 2010, 02:08 PM
Will work for foam
wingnutt's Avatar
Jack - Assuming you are using the same GP 10x4.5SF prop, I would say the numbers may not be lying. That may be the largest prop for that motor on 3s. Possibly the magnets may have gotten cooked a bit during the last run of the original wind and lost some magnetism.

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Wire gauge for 30 Amp Power Suppy Tim B Batteries and Chargers 25 Mar 29, 2010 10:43 PM
Discussion Emax CF2812 Rewind - need advice mabuse_ Electric Motor Design and Construction 6 Feb 27, 2010 09:23 PM
Sold Dave North Rewind Emax FC-2805 (~2725v) dashunde Aircraft - Electric - Power Systems (FS/W) 2 Apr 06, 2009 11:10 PM
Discussion wire size for rewind rcalldaylong Electric Motor Design and Construction 3 Mar 08, 2009 11:28 PM
For Sale EMax BL2210-30 NIP darkside212 Aircraft - Electric - Power Systems (FS/W) 0 Mar 15, 2007 06:54 PM