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Old Jun 09, 2012, 08:26 AM
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leadfeather's Avatar
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8p NN SS NN ... it works!!

I just did a quick test on an 8p red and blue wonder. NN SS magnet arrangment to achieve the 8p ( 8 magnet) configuration. It seems to work!

I managed to get 9 turns of 23g wire ABC on the stator; connected Y,

First quick results with a TGS 4.5 x 4.5 prop; 460 grams thrust, 19 A 199 Watts.

Runs pretty smooth. Not sure if I should have high esc timing or automatic esc for this motor.

Putting the magnets back on is pretty easy. They are a tight fit so make sure to get all the residual glue off the magnets and then just stuff them back in the rotor with no gap.
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Last edited by leadfeather; Jun 10, 2012 at 04:53 AM.
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Old Jun 10, 2012, 04:11 PM
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Truglodite's Avatar
Carmichael, CA
Joined Feb 2007
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I checked DCalc SPC and it says roughly 70% efficiency; not bad for 9T-23awg running 200W, but I was hoping for more. I'm curious to see how it would run with a single mag 8p rotor. I'm sure it wasn't all that fun getting 16mags back in; I've never glued 16 mags in a 'wonder motor now that I think about it.

Kev
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Old Jun 11, 2012, 06:40 AM
Winging it >
leadfeather's Avatar
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Quote:
Originally Posted by Truglodite View Post
I checked DCalc SPC and it says roughly 70% efficiency; not bad for 9T-23awg running 200W, but I was hoping for more. I'm curious to see how it would run with a single mag 8p rotor. I'm sure it wasn't all that fun getting 16mags back in; I've never glued 16 mags in a 'wonder motor now that I think about it.

Kev
Gluing the magnets in wasn't really hard. No spaces, just push the magnet in place next to the last one. I glued them in place two at a time. Putting in a NS combination would hold the magnets in place. When putting in a single N next to a N, I would have to hold the magnet in place until the glue set up otherwise the repelling force would create a gap.

Testing the single magnet 8p is a good idea for comparison.

I was a little surprised that the kV wasn't higher on this first try.

Kev and others, what is the best ( not too hard) BW motor you have done so far for speed?
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Old Jun 11, 2012, 07:05 AM
Jack
USA, ME, Ellsworth
Joined May 2008
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The magnet coverage is a factor in the motor's performance too.

I think I've read in various threads that is is best to have less than 100% coverage with the magnets on the inside of the housing, to have some gaps between them. Numbers in the 80% and up to 95% have been mentioned.

But I don't know where that difference would show up in the motors performance. I would guess it would be the RPM range. Or maybe it lets the ESC better sense the passing pole locations and deliver power more efficiently? Getting into some serious motor engineering considerations here now.

Jack
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Old Jun 11, 2012, 07:12 AM
Jack
USA, ME, Ellsworth
Joined May 2008
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It occurred to me where I had seen that before, it is here:

http://www.bavaria-direct.co.za/models/motor_info.htm

There is at Magnet Coverage Spreadsheet (xls) there!

I ran that with OpenOffice Calc and the attached is what it has to say about it. If you can't run that, give me the numbers and I'll run it and post a screen shot for you.

Jack
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Old Jun 11, 2012, 11:23 AM
homo ludens modellisticus
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The Netherlands, GE, Nijmegen
Joined Feb 2001
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Jack that is Christo v.d. Merwe's site, user Skylar on RCG. Nice to correspond in Dutch / South-African with someone/people living in the southern hemisphere.

Vriendelijke groeten Ron
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Old Jun 11, 2012, 06:37 PM
Jack
USA, ME, Ellsworth
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It is a great page, and a wonderful donation to the hobby. I used it a lot when I was getting started on rewinding and still go back to it occasionally.

I've never had much luck with languages. Every time I tried to learn one it was a struggle. And then I'd seem to run into these regional dialect issues that rendered one or both sides of attempts to use it incomprehensible.

Jack
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Old Jun 11, 2012, 06:47 PM
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United States, WA, Puyallup
Joined Aug 2006
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Quote:
Originally Posted by leadfeather View Post
Kev,

Going in a few different planes

A pbf speed contest plane
Little speed delta
HK EPO MK II Park Jet
Swifty, scratch built pylon type plane

The 8t ABC has worked well for a couple of guys but only using a Castle Creation esc.

Based on Jack's and your response I think DLRK would be better, and also the 14p housing. I s this correct?

Below is a video of adreher's X-Raycer with the 8t ABC. It does about 110 mph

http://www.youtube.com/watch?v=wonGKfM286w

dont blink or youll miss it
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Old Aug 09, 2012, 04:49 PM
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United States, UT, Ogden
Joined Nov 2004
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Has anyone had a front bearing failure with a newer 2730? I bought a bunch of Turnigy 2730 1300's and have had 4 of them come back with the front bearings blown out - they are also a larger front bearing than some of my older red and black turnigys - did they change the bearing size? Also I cant get the bearing race out - when I tried to remove the bearing it came apart with the inner parts coming out but the outer race is stuck in the bore of the shaft - any ideas how to get that out?
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Old Aug 11, 2012, 10:58 AM
Dave North
timocharis's Avatar
USA, CA, San Jose
Joined Apr 2004
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That's not good news. I haven't seen this particular batch, but other motors have used those larger bearings in front and it they have always been the same way: extremely flimsy bearing cases that fall apart almost instantly.

You can try some WD40 or the like on the bearing skin and later try to pick it out carefully. I don't hold out much hope they will every be any good though. In the end I gave up on any motors that used those bearings as being not worth the effort.

Bad news indeed!

Dave
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Old Aug 11, 2012, 08:45 PM
Jack
USA, ME, Ellsworth
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Quote:
Originally Posted by asat View Post
Has anyone had a front bearing failure with a newer 2730? I bought a bunch of Turnigy 2730 1300's and have had 4 of them come back with the front bearings blown out - they are also a larger front bearing than some of my older red and black turnigys - did they change the bearing size? Also I cant get the bearing race out - when I tried to remove the bearing it came apart with the inner parts coming out but the outer race is stuck in the bore of the shaft - any ideas how to get that out?
And the race is at the bottom of a blind counter bored hole, right? No overhanging edges or holes that can be used to drive it out? You can try warming the stator up and hoping the race is loose enough to fall out. Other than that the only way is usually to work a sharp edged screw driver under it and try to lever it up. I have done that by bending a small screwdriver to a _/ kind of shape and tapping it in. Not pretty but it worked....

Jack
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Old Aug 12, 2012, 09:29 AM
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Quote:
Originally Posted by jackerbes View Post
And the race is at the bottom of a blind counter bored hole, right? No overhanging edges or holes that can be used to drive it out? You can try warming the stator up and hoping the race is loose enough to fall out. Other than that the only way is usually to work a sharp edged screw driver under it and try to lever it up. I have done that by bending a small screwdriver to a _/ kind of shape and tapping it in. Not pretty but it worked....

Jack

yep, thats the one, wonder why they change design? And to an inferior one no less. I'm thinking it isnt going to be worth the hassle.Looking into some Keda replacements.
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Old Aug 12, 2012, 10:15 AM
Jack
USA, ME, Ellsworth
Joined May 2008
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I have not had to pull a race from a RC motor yet, I was talking more about years past and in machinery and motors. They make blind hole bearing pullers that will do down and past the race and then expand to engage it. Then a sliding hammer is used to lift the race.

Jack
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Old Aug 12, 2012, 10:48 AM
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I got around 250 watts in from a 22AWG 14T star LRK 2505 14P, I wound it while back it was spinning around 20K RPM. Way ,way to fast for my feeble piloting skill. I didn't have the test equipment I have now so I don't have any efficiency numbers. Some one ran it through D calc and said it was around 50%. Although I doubt that is correct as I have found Dcalc to disagree with real world measurements by quite a bit at times. The primary reason I think it was more efficient is it ran slightly above ambient temp. I would imagine a delta connection on a 14T LRK would be a real screamer.

"14T 22AWG from powerwerks. The prop is a an APC 7X4 SF/E/? it peaked at at about 13.5K RPM, 28A and 290W on 3S" I went back and looked at my notes as I try not be to liberal with numbers.
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Old Aug 12, 2012, 10:51 AM
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Has anyone had a front bearing failure with a newer 2730? I bought a bunch of Turnigy 2730 1300's and have had 4 o.....

Trick for removing bearings from a blind bore. Find or whittle a stick to the ID of the bearing, fill the blind bore with grease. Install stick and push, depending on how well the bearing is sealed it may require a light smack with a hammer to create the psi needed. Hydraulic pressure will push the bearing out. That's the old Ford trick for removing pilot bearings. Works every time I need it to when I don't have the right size puller on hand.
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