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Old Oct 19, 2009, 04:10 AM
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Carmichael, CA
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I tried winding 11.5T 26awg Y again (23T parallel). This time I started out really clean on the first 2 layers, so I got too greedy and went for 24T during the finish. Should have known better; my per phase Rm's were out of wack again. Perhaps I did an extra turn again, some turns missing somewhere; I dunno because I had to cut the wires out this time.

Good news is that failure made me go in a more "reasonable" direction with this motor. I tried 17T 25awg (delta), and the stator didn't want to be more than a 16T.... for me. 17T would have already been on the edge of too much current for my needs, so I tried the next logical step, a 10T 23awg (y). Finally, my Rm's are a solid looking 94.2, 94.2, and 94.4, with no stator or cross-phase shorts of course! Can't wait to put some props on this guy and see what he's capable of. Even if it's no splendor, I'll be glad if it works since it's had 4 rewinds on it now without even being flown, lol.

Dave, 10Y is right above 17D on the turn chart. I'm hoping this compares to your 17T-D, but with about 1A less, and (wishful thinking) a smidge higher effy?

FYI, while I was at it I measured 0.5mOhm per inch for my Consolidated 23awg. So you get about 0.5mOhm error on internal shorts. Anyhoo...

Quote:
Originally Posted by rloberlin
Anyway, it looks like your idle currents are pretty low so they are probably not worth worrying about....
Exactly, and for comparisons the idle current sort of cancels out, as long as you use the same esc for all your tests.

Cheers,
Kev
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Old Oct 19, 2009, 04:58 AM
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Julez's Avatar
Germany
Joined Dec 2003
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I do not like this 24n motor particularly.
I recently tested it on my bench, and compared the 1800kv version to a 1700kv blue (silver) wonder. The 24n had a bit more power at full throttle, but for any given input power when throttled, the blue wonder had 300-400RPM more.

The blue and red wonder should be even better.
I am thankful that I stumbled over this thread just know. I immediately ordered 2 blue and red wonders.
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Old Oct 19, 2009, 11:38 AM
Dave North
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USA, CA, San Jose
Joined Apr 2004
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Quote:
Originally Posted by rloberlin
One way to gauge whether the correction is useful might be to test the Io of the same motor at the same voltage on a bunch of esc's ... it looks like your idle currents are pretty low so they are probably not worth worrying about.
Interesting approach, and knowing me I'll get around to it someday. But I agree it's probably not very important.
Quote:
When you say that you are calculating Kv from Io and measured Rm, you mean Io, measured Rm, and no load RPM, right?
Right! My shorthand bad.
Quote:
Originally Posted by Truglodite
Dave, 10Y is right above 17D on the turn chart. I'm hoping this compares to your 17T-D, but with about 1A less, and (wishful thinking) a smidge higher effy?
It's a little hard to predict due to hardware variance. I've seen 17s and 10s that look almost exactly the same. But the odds are it will turn out roughly that way. Usually, the 10Y is a softer motor at higher efficiency. Somewhere around 15-16oz for about 8amps. And frankly, getting close to 2x thrust/amps at 2S is a teeny thrill for me.
Quote:
Originally Posted by Julez
I do not like this 24n motor particularly.
I don't hold out a lot of hope for it. Also, it's kind of a pain to rewind. Looks cute though!

Dave
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Old Oct 19, 2009, 04:08 PM
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Problems with grease, and more confusing results

I spun up the 10T-23awg today, and my initial results were lame. Io was too high, and efficiency sucked. I noticed excessive bearing drag, so I blew out the factory grease, and added a drop of lightweight oil. Then magically my Io was more what I was expecting (but still a tad high). The interesting part is the efficiencies only perked up slightly with the oil; I thought with such a big change in Io, 0.92A to 0.62A, efficiency would have done better than that.

Note that even after oiling, I have an older BW that spins much more freely than this one. Perhaps there was some remnants of grease left behind after I blew it out with motor spray. I rigged up a tool that forces the spray though the bearings, but I didn't rotate and respray at all.

Anyhow, I'm still at a loss as to why I'm having such a hard time getting over 80% with my 8040hd? A wind like this should do it, and I sorta doubt it will improve much after the bearings are more broken in.

Cheers,
Kev

ps: Julez, thanks for the "bearing tool" idea. This should be an interesting data set for those curious about grease vs oil.

[edit: I updated the "oiled" numbers; got rid of the "bad" calculated Rm value.]
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Old Oct 19, 2009, 04:52 PM
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lance dalton's Avatar
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Congrats again, kev. You didn't hit 80% but it's dam close.

What's this "bearing tool" I've been hearing about?

Julez, great thread you started on parallel charging. Very informative.
FYI, the R&B 3000 kv's are dLRK and the 1700, 1500, 1300 are ABC winds in case you didn't know. I just bought two 3000kv's to wind. Very well made.
That's odd that your bench tests showed more full throttle output for the 24n. One of the guys on the 3020 thread said it had more low end punch than the Wonder. It will be interesting to see what becomes of it. If it can sing Dave can make it a soprano .

Lance
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Old Oct 19, 2009, 05:21 PM
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Quote:
Originally Posted by lance dalton
Congrats again, kev. You didn't hit 80% but it's dam close.

What's this "bearing tool" I've been hearing about?
...

Lance
Thanks Lance. I think it's close enough to use, and maybe this motor just has bad mojo. I don't have the gall to rewind it again, since the insulation is probably shot and I've already had 2 not so spectacular tests with it.

The "bearing tool" is nothing more than a 3" long piece of 3mm CF tube, plugged on one end, with a small slot cut in the middle. I attach the open end of the tool to a can of motor spray, insert the tube in the motor, such that the slot is located between the 2 bearings, and blast away. This creates a high pressure blast of cleaner that squirts out of the bearing seals front and back. Gotta wear safety glasses when you use it, but it definitely gets the bearings squeaky clean.

FWIW, after that last test, I checked the bearings again and they're every bit as smooth as (if not smoother than) that old BW I was talking about. If I spin the rotor with my fingers, I could go and take a leak, come back, and it would still be spinning, lol. Before it wouldn't spin more than 5sec.

Cheers,
Kev
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Old Oct 19, 2009, 06:26 PM
Dave North
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Kev, there are a bunch of reasons the efficiency can suffer even after you get the bearings straightened out. And in fact, you're right at high average for the results I got from that wind, so that might just be all she wrote.

Things to look for: is the stator at an exact right angle to the bearing tube? Are the mags evenly spaced and is the airgap the same for all of them? Are the bearings mounted eccentric in the tube so the airgap wanders? Etc. Any of those things can mess with the quest for an 80. Most don't turn out that way, alas. High 70s is pretty much the norm for a good job.

Lance, I'm oscillating about the wind. It looks like 16T of <28 is a workable wind, and I also test wound a 1/2 phase with 11T excellent 27awg. I have the funniest feeling the 11T would give the better result as a Delta 2S (calm the motor down a bit to get into the efficiency range) but the 16T just looks cool! However, the <28 (I think it's the same wire the motor was originally wound with) is some sinojunk I got with some kit or something and is probably low quality. It's not quite 28, and not quite 29awg. Probably some SWG or MM variant but I'm too lazy to check the tables.

What to do?


Dave
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Old Oct 19, 2009, 06:37 PM
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Carmichael, CA
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Quote:
Originally Posted by timocharis
...Any of those things can mess with the quest for an 80. Most don't turn out that way, alas. High 70s is pretty much the norm for a good job....


Dave
Ahh, a sigh of relief. Thanks Dave, I was starting to think there might even be a problem with my logger calibration or something. There is a slight eccentricity to the rotor and stator. My eyes aren't good enough to see an magnet spacing error, but either way it is what it is, "sub 80". No doubt you rewind 10x more than I do, so you're bound to have more chances at 80; I think I'll just have to put in my time and eventually some exceptional mechanicals will start showing up at my doorstep.

Cheers,
Kev
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Old Oct 19, 2009, 06:55 PM
Dave North
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Quote:
Originally Posted by Truglodite
No doubt you rewind 10x more than I do, so you're bound to have more chances at 80
That's about the story of it. Do enough of them and you'll score. Probably on an unexpected motor -- it's caught me by surprise a few times, on winds or hardware that seemed unexceptional.


Dave
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Old Oct 20, 2009, 03:08 AM
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Ron van Sommeren's Avatar
The Netherlands, GE, Nijmegen
Joined Feb 2001
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Quote:
Originally Posted by lance dalton
... What's this "bearing tool" I've been hearing about? ...
See
http://www.rcgroups.com/forums/showt...5#post13326055

Vriendelijke groeten Ron
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Old Oct 20, 2009, 05:43 AM
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Julez's Avatar
Germany
Joined Dec 2003
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Quote:
Originally Posted by lance dalton
[]
That's odd that your bench tests showed more full throttle output for the 24n. One of the guys on the 3020 thread said it had more low end punch than the Wonder.
[]
Lance
Hi Guys,

my judging my have been premature.

As I just learned, throttling can decrease performance.
http://www.rcgroups.com/forums/showthread.php?t=1128430

I just went to my workshop to check again with a video camera.
I began at full throttle and decreased gradually.

Silver Wonder
A,W,rpm
6.2o, 42.7, 7880
4.59, 31.2, 7050
3.32, 23.4, 6300

Turnigy 3020
A,W,rpm
8.87, 55.0, 8210
6.60, 44.1, 7570
5.00, 34.8, 6950
4.46, 30.5, 6570
3.52, 24.4, 6070

Same prop and same esc, Battery was probably quite depleted.

OK, maybe this in too much off topic now.

Cheers,

Julez
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Old Oct 21, 2009, 12:55 AM
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lance dalton's Avatar
Chino Hills, CA.
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Thanks for the info for the tool guys.
I want to try 5w/30weight 100% synthetic motor oil for bearings. I think it would work very well, any thoughts from anyone? I've been using 3in1 but wanted something better.

Jules,
What prop were you using on the bench test? The lipo didn't seem to hold voltage well on the 3020's first run up at 8210rpm. I figured 6.2 volts. Were you using a small mah lipo?

Dave,
My 3020 still hasn't arrived . I think it got put on the slow boat from China .
What kv are you shooting for?

Lance
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Old Oct 21, 2009, 01:03 AM
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United States, AZ, Chandler
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I've heard Gun Lube works well for bearings of questionable quality.
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Old Oct 21, 2009, 01:17 AM
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Julez's Avatar
Germany
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Hi Lance,

I was using a 8x4 GWS DD propeller.

Yes, the LiPo I used was a cheap 12C 800mAh Mystery from 2008, which was not even fully charged.
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Old Oct 21, 2009, 04:39 AM
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8x4 DD, my favorite!
I'm glad that prop fits the motors prop saver. I like GWS SF but their very fragile.

A friend swears by Tri-Flo. He says it drys and doesn't attract dirt or dust as bad. I've used it on motorcycle chains and it did work great.

Lance
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