Thanks Ron:

Since both motors have the same number of poles and magnets (12 and 14), then why might one have more cogging if the electricals are also the same? And should there be any appreciable difference in performance between the two motors?

All manner of things can be different between two seemingly identical motors (aside from the wiring errors Ron already mentioned). Here are some other examples:

A difference in air gap between the magnets and stator can affect cogging. In particular, an error in the spacing of the magnets can create a harmonic cog. And even more amusing, the actual placement of the turns of wire can have an effect, though very minor -- which means two motors with the same number of turns of the same gauge wire can behave differently simply because one has the wire spaced differently.

Just to make it all more infuriating, various minor differences can add and subtract from each other, making each motor quite unique almost no matter what.

Dave

Originally Posted by Eric Odle

...
Since both motors have the same number of poles and magnets (12 and 14), then why might one have more cogging if the electricals are also the same? And should there be any appreciable difference in performance between the two motors?

The generator effect I mentioned could be taken for cogging. So if you had one of the motors shorted and the other not ...


Vriendelijke groeten Ron
• diy motor tips • Drive Calculator •
• diy motor group • Cumulus MFC •

Thanks for your insights guys...

One more question: I have before me two 2730's with the windings removed. One has a bit more cogging than the other. Could I expect better performance from the motor that has the least cogging, or is it simply more complex than that?

I think you'd have to guess that one of them has better magnets, smaller air gaps at the hammer heads, or something else that is beyond your control in a cheap motors market.

Mark them so you can tell them apart, wind them exactly the same, and maybe something conclusive and interesting will emerge in test.

Jack

To the cogging discussion: I have recently replaced all the stock magnets (which were glued in with typical Chinese "hot glue") with 2mm magnets I bought from Strong RC Motors. I had to slowly sand each magnet to about 1.7mm to make it fit (used sandpaper and custom magnet holder to avoid heating), a lot of work just for the heck of it.
I haven't wound this motor yet, but the cogging with tiny air gap and stronger magnets is way higher than in the original motor.

Boris

Originally Posted by Eric Odle

... I have before me two 2730's with the windings removed. One has a bit more cogging than the other. Could I expect better performance from the motor that has the least cogging, or is it simply more complex than that?

Cogging, or the lack of it, says nothing about quality, power, magnet strength, power, max.current, torque, Rm, I0, Kv, Kt.

Originally Posted by bluesky123

... I had to slowly sand each magnet to about 1.7mm to make it fit ...

Make sure the magnets are sealed again (lacquer, resin, nailpolish) otherwise moisture in the air will ruin your magnets.


Vriendelijke groeten Ron
• diy motor tips • Drive Calculator •
• diy motor group • Cumulus MFC •

I have a 2712-12 1300kv Blu Wonder from Heads up RC that I need to rewind--(broken lead). I have never rewound a motor so need to be educated starting with removing the old windings. I have taken the motor apart to the extent that the stator with windings,bearing tube and bearings are in one piece, so maybe can skip preschool and start with kindergarten. Initial questions:

1.--How do I remove the old windings? they appear to be glued or epoxied in place.
2.--In order to end up with approximately the same kv as original what size wire an no. of turns should I use?
3.--I have some copper wire that measures about .020 in. dia. that I took from around the picture tube of a color tv set about 40 years ago. Will that work or do I need to order wire from GB?

I have read thru the first 50 pages of this forum and have gotten a little understanding but you guys have a language that's still pretty foreign to me at this point. Any suggestions or pointers to tutorials etc. that can help?

Thanks for any help you can give

Edit--my motor has 12 coil stator and 16 magnets. I'm now thru page 50 of this forum and have thoroughly read the GoBrushless website but still haven't found no of turns, wire gage etc. for 1300kv or so motor. I think I do understand how to wind for a Star type connection however.

Bob

Star and delta are not winding diagrams Bob, they are hookups, two ways to connect phases after winding.

Your motor must be wound according to the ABCABCABCABC winding diagram, not LRK or dLRK.

Don't use used wire, will give shorts. Use thickest wire possible for desired number of turns, better for efficiency and power. Go to your local friendly motor/transformer rewinder/refurbisher or repair shop. Excellent quality, all gauges, penny stuff, you'll probably get it for free if you bring your motor along. They love it when they can handle a motor without an overhead crane And maybe let them have a spin with your plane once you finished your motor? You know, in case you need wire again for your next motor

About removing windings, the pictures say it all. Stick stator in an oven to soften glue. Put a clamp on statortooth to prevent the laminations from bending outwards.
http://www.eschmidt.onlineelektro.de...oren/drehstrom
or
translate...www.eschmidt.onlineelektro.de/scripts/show.aspx%3Fcontent%3D/shop/home/leistung/motoren/drehstrom

More otor (re)winding tips, tricks, vids, manuals, checks and safety tests:
www.rcgroups.com/forums/showthread.php?t=240993


Vriendelijke groeten Ron
• diy motor tips • Drive Calculator •
• diy motor group • Cumulus MFC •

Thanks for all the links Ron

I am using the wire just for practice to see if I can get 11 or 12 turns/arm on the stator. After several trys, the most turns I seem to be able to fit is about 8 or 9 so I have ordered some 26 ga. wire. Either there is some tricks I haven't figured out or my stator is different from what you guys are using. At this point it looks like I would have to order 50 lbs or so of 24 ga. wire in order to have enough to finally get the 11 or 12 turns I think I need

Bob

Bob, you've already taken the step I would have suggested and ordered thinner wire. Once you get your motor wound with the 26awg wire, you will have learned some tricks and can rewind it with thicker wire later. Make sure you are using an old prop to wedge between the stator teeth to flatten out your windings as you go. I don't rewind very often, so after I rewind a motor, my thumbs hurt for several days afterwards from tugging the wire tightly. Be patient, take your time, and once you finally get-er-done, you will be rewarded with a great motor and the satisfaction of having done it yourself.

Winding tricks and tools for packing more copper:
http://www.powercroco.de/Bautips.html (use translate.google.com to translate link)
http://www.powercroco.de/wickelwerkzeug.html (tools)
http://www.powercroco.de/Gurkenditto.html (errors)

http://www.rcgroups.com/forums/showthread.php?t=249007
http://www.rcgroups.com/forums/showthread.php?t=447174
http://www.rcgroups.com/forums/showthread.php?t=445750
http://www.rcgroups.com/forums/showthread.php?t=401641
http://www.rcgroups.com/forums/showthread.php?t=381117
http://www.rcgroups.com/forums/showthread.php?t=400958

Hi folks, I've been having lots of fun winding these motors. It seems that almost every wind I do is 24 gauge, and my spool of 24g MD Wire is getting lighter these days. I also picked up some 22g for the fun of it, and I have yet to use it.

However, I am now looking to tune a 2730 for a power system using a 6x4 APC prop on the new Nanotech 800mAH 2s batteries I have in my limited inventory. Using the 14-pole dLRK wind, I am probably looking at around 12T Delta for my Turnigy 10-amp ESC... Or, 7T-Y!

I'm guessing I'd get to use my 22g for a 7T motor, but is there some compelling reason why I shouldn't do this? I don't see a lot of low turn winds out there...

Eric, this is some info from a PM between Truglodite and myself that may help you in the right direction.


No, I haven't tested a 6T with 2s yet, but it'll come between 11T-D and 10T-D. Dave has tested 11T-Y on 2s, which is the next notch lower in Kv at 2750:

Turnigy 2730-14P-11T-24awg-Delta
2756Kv
Io=1.10A
Rm=0.051 ohm
GWS 5043hd/15739RPM/7.00V/9.10A/11.4oz/75.4%

...and I've tested 10T-23a-D, which is the next notch higher in Kv:

Turnigy 2730-14P-10T-23awg-Delta
3111Kv
Io=1.05A
Rm=0.032 ohm
GWS 5043hd/17402RPM/6.68V/13.33A/14.5oz/71.5%

6T-Y will be in between those numbers. Note that 6T-Y raw Kv is technically 2900, but on 3s the raw Kv turns out to be around 2750Kv due to extreme RPM (more eddy currents slowing it down).

"..Note that 6T-Y raw Kv is technically 2900, but on 3s the raw Kv turns out to be around 2750Kv due to extreme RPM (more eddy currents slowing it down)..."

I think at that Kv you are getting up into the area where reducing the number of magnets would be necessary or helpful, wouldn't it?

Jack