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Old Sep 20, 2011, 09:27 PM
Dave North
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USA, CA, San Jose
Joined Apr 2004
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I tried both 7T and 8T 22awg but never 6T. Both of those were okay.

Dave
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Old Sep 20, 2011, 11:25 PM
Sorry, but they're all toys.
Eric Odle's Avatar
United States, WA, Bellingham
Joined Jun 2009
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Thanks Dave, I'll try it out. Any recollection of your results? And do you think that for all practical purposes the 7T-Y is as good as the 12T-D? They are both mid-2400kv.

Oh and I'm a little skeptical of the quality of this 10 Amp Turnigy ESC I have on hand, any recommendations on an alternate ESC that is inexpensive? It's going on a Polaris, so it may get wet. Hopefully not, but this'll be by first seaplane, and you know how that goes...


-Eric
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Old Sep 20, 2011, 11:52 PM
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Carmichael, CA
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Eric, are you using an old motor or new? The new ones get around 2600Kv with those winds, not 2450Kv like the old blue & reds. Polaris... I'm guessing a seaplane? Doubt the prop will unload much, so be careful. I'd point you in the right direction, but I haven't done any 2s 6x4 testing... nothing even close actually.

Kev

edit: Is it a turnigy plush 10? Those esc's are good. I run mine at 11-12A regularly with no problems, and they seem to handle small high rpm outrunners better than my expensive esc's.
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Old Sep 21, 2011, 12:19 AM
Sorry, but they're all toys.
Eric Odle's Avatar
United States, WA, Bellingham
Joined Jun 2009
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Quote:
Originally Posted by Truglodite View Post
Eric, are you using an old motor or new? The new ones get around 2600Kv with those winds, not 2450Kv like the old blue & reds. Polaris... I'm guessing a seaplane? Doubt the prop will unload much, so be careful. I'd point you in the right direction, but I haven't done any 2s 6x4 testing... nothing even close actually.

Kev

edit: Is it a turnigy plush 10? Those esc's are good. I run mine at 11-12A regularly with no problems, and they seem to handle small high rpm outrunners better than my expensive esc's.
Yeah, Polaris is a scratch-build Depron delta wing seaplane also available as a kit. And I am using a new motor, though a couple of these were actually blue and red not black and red... Seems my last order a year or so ago was a mix of both oddly enough. I'm not sure how to tell the difference besides the color.

I am thinking of using a Plush 10, though I might consider the 12 if those ESC's are ok. I do have an 18 on hand, which I'm considering as overkill since this ESC is likely to be buried. Or maybe a small heatsink, we'll see. My days of constant WOT are behind me so I might go light if I can.

I think I'll try the 7T and if I need more ESC then I'll get it. The 800mAH nanos can probably handle a bit more than 10A.
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Old Sep 21, 2011, 10:25 PM
Dave North
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USA, CA, San Jose
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Originally Posted by Eric Odle View Post
Any recollection of your results? And do you think that for all practical purposes the 7T-Y is as good as the 12T-D?
Yes and yes, which somewhat surprised me. It turned out to be a good equivalent, and actually looked kind of cool too. I expected a somewhat lesser result, but perhaps the blank was a good one.

Of course, these were the older motors, so YMMV as regards the newer version.

Dave
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Old Sep 21, 2011, 11:39 PM
Go ahead... Build it to crash!
Fuegodeth's Avatar
Conroe, TX
Joined Apr 2007
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Hey Eric. I used 2 strands 26g 8 turns star for my 75% polaris with this motor. Running on 3s with a 6x5 APC E prop. (not SF). It climbs out of sight at full throttle, and motor comes back barely warm after a 10 minute flight. Am using a CC Thunderbird 18 that has been corrosion _X'd. It's pretty well buried. I get 9-10 minutes using 700 mah out of a 1000mah 3s 25C pack. I think I measured about 15-16A on the bench. During flight it is much less. It does unload a bit as it is a fairly sleek airframe. And half throttle is about all you need unless you want to punch holes in clouds. Nice vert, takes off in 5 feet, and cruises at a pretty decent speed when you want to haul some A.

I have a 100% polaris using a rctimer equivalent of Emax 2822. Tbird 36 in that one and using a 2600mah lipo. Uses 7x5 APC E prop. Get 8 minutes on 1400mah and great performance. I think I did a 12t 24G delta on that one. (will have to double check that). KV is lower as it's a larger motor than the 2730. Works great though. Nice bearing tube style motor like the 2730. Easy to rewind. One C clip to remove and you are in business.
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Old Sep 21, 2011, 11:56 PM
Sorry, but they're all toys.
Eric Odle's Avatar
United States, WA, Bellingham
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With an ESC buried at those loads, I'm guessing you discovered the melting point of Depron? Did you use a heatsink?
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Old Sep 22, 2011, 08:16 AM
Jack
USA, ME, Ellsworth
Joined May 2008
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A Thunderbird 18 at 16A is not going to get hot unless you have a heavy receiver and servo load on the built in linear BEC. The CC ESCs are fine for use at their rated values, you don't really need to downrate them at all.

The older CC ESCs with built in linear BECs reqire some attention to detail as that can be a major source of heat and it is not real hard to overload the BEC. But most of the stuff that is flying on the 25g class motors also has a pretty light load on the BEC as far as receivers and servos too.

Jack
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Old Sep 22, 2011, 09:04 AM
Go ahead... Build it to crash!
Fuegodeth's Avatar
Conroe, TX
Joined Apr 2007
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Yeah, it doesn't get hot. CC rates their ESC's very conservatively. They use better FET's than others, so much less heat. They already de-rate them. I run a TB-18 on a flying wing with a 2730 12t 24g delta that pulls 25-26A on the bench. I run a nano-tech 1300 down 1000mah in a 4 minute flight. ESC and motor come down cool to the touch. They are externally mounted with great cooling though. Battery gets warm, but nothing else does.
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Old Sep 22, 2011, 01:07 PM
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Yep, Castle says their esc's need "5mph" of air to stay cool, but with thermal and overcurrent protection circuitry, there's not much that can go wrong on a CC esc regardless of cooling. I'll be the first to admit that esc cooling takes a back seat on my more demanding applications. Still, I've only sent 2 Castles in for repairs because 1) connected the lipo with reverse polarity, and 2) smashed an input capacitor during a crash (and my attempt to replace it failed :P). You do have to take more care with Castle esc's as you go up in power (things happen fast and furious when you are running 700W+), but at these power levels a CC esc should be considered 100% bulletproof... provided you don't turn off the current limiter.

Kev
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Old Sep 22, 2011, 01:16 PM
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Quote:
Originally Posted by jackerbes View Post
A Thunderbird 18 at 16A is not going to get hot unless you have a heavy receiver and servo load on the built in linear BEC. The CC ESCs are fine for use at their rated values, you don't really need to downrate them at all.

The older CC ESCs with built in linear BECs reqire some attention to detail as that can be a major source of heat and it is not real hard to overload the BEC. But most of the stuff that is flying on the 25g class motors also has a pretty light load on the BEC as far as receivers and servos too.

Jack
Awesome point here... you know you're overloading a BEC when the esc gets very hot while you're setting up linkages before maiden. I've seen guys replace motors, drop prop sizes, and even go to lower V packs trying to fix problems with smoking esc's... when the cause of the problem is binding linkage. Don't be that guy!

Kev
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Old Oct 08, 2011, 10:43 PM
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10 pole...

I made an interesting discovery during my recent Turnigy 2730 experiments. The old blue & red version has curved magnets, the newer black & red HK now sells has flat magnets. Less magnetic flux... makes sense with the different results we noticed once the black version showed up. POOP! Now I cherish my collection of blue & reds even more than before.

My current crop of experiments involves 10 pole rotors for high speed stuff. So far I've compared a 14p 12T-24a-parallel-Y against a 10p 16T-25awg-parallel-Y (both just north of 2700kv). The 14p is straight up classic blue & red (my "scrappy" motor). The 10p is made with a thin lam turnigy stator and an old school blue wonder rotor (black curved mags).

I've had superior results with 10p at medium amp draws (3s 4.1e), but as the amps go up the 10p drops off fast (14p is better with the 4.75e). This is great news to those looking for an even more efficient alternative for their park speedster than say, a 14pole 12T delta, but not quite the power level I was after. This could be related to having a tad less copper in the 10p motor. So more experiments are needed.

I'm cobbling together a red & blue 10p rotor tonight. I'm curious to see the difference between the original blue wonder black curved mags, and the long lost silver curved magnets of the red & blue.

Kev

[edit: A quadruple post is just too much...

I ended up testing what amounts to 6 different 10 magnet pole dLRK 2730's. To do this I used 2 different Turnigy 2730 stators, and 3 different rotors. The stators were wound with 8x2T-25awg-Y, and 12T-24awg-D. I made the 3 rotors with a) an original blue wonder rotor with it's curved black magnets, b) a newer black & red rotor with older curved silver magnets, and c) an older blue & red rotor with newer flat silver magnets. I put the old style silver curved magnets (best magnets) in the newer style black & red rotor (lighter & better cooling), for use in my Eclipse. The resulting Kv's were in the 2700 range with the 8Y, and 3300 with the 12D. All testing was done with a fully charged Rhino 3s1250 30C (29m, 22C, DCalc efficiency, thrust from my thrust stand).

8Y/black curved=======
no load / 31284RPM/11.47V/0.71A -> 2727Kv
APC 4.1x4.1e / 26549RPM/11.89V/15.12A/15oz/75%/103mph
APC 4.75x4.75e / 22779RPM/11.51V/23.04A/18oz/70%/103mph

8Y/silver curved=======
no load / 34275RPM/12.39V/0.93A -> 2766Kv
APC 4.1x4.1e / 26387RPM/11.69V/14.32A/14.7oz/80%/102mph
APC 4.75x4.75e / 22813RPM/11.39V/22.49A/18oz/73%/103mph

8Y/silver flat=======
no load / 35008RPM/12.45V/0.80A -> 2812Kv
APC 4.1x4.1e / 26418RPM/11.62V/14.80A/15.2oz/78%/103mph
APC 4.75x4.75e / 22857RPM/11.39V/23.17A/18oz/72%/103mph

12D/black curved=======
no load / 40541RPM/12.19V/0.99A -> 3326Kv
APC 4.1x4.1e / 29573RPM/11.16V/23.07A/20oz/74%/115mph

12D/silver curved=======
no load / 40945RPM/12.23V/1.05A -> 3348Kv
APC 4.1x4.1e / 29801RPM/11.20V/23.13A/20oz/75%/116mph

12D/silver flat=======
no load / 39789RPM/12.25V/0.95A -> 3248Kv
APC 4.1x4.1e / 29728RPM/11.29V/22.68A/20oz/75%/115mph

Yes Jack, it was a bit unnerving spinning one up to 40kRPM for no load the first time. My results show that there's no real difference between the various magnets; maybe with the 8Y, but I'm after more myself. Even slightly off magnets in the black mag rotor didn't do much to dull performance. I'm tempted to fly a 4.75 with the 12D... only way to test that is in the air, LOL!

Enjoy,
Kev
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Old Oct 11, 2011, 07:04 PM
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Singapore
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How did you get the magnets off the bell, and what glue did you use subsequently to glue them back on?
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Old Oct 11, 2011, 08:58 PM
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I used a utility knife to pry on the corners of the magnets, and they popped right out (safety glasses an absolute must... bits of utility knife are bound to go ballistic). Then I scraped the insides of the rotors to remove excess glue residue. After scraping the rotor, I arranged the magnets with proper spacing, and used black CA to fix them in place (BSI brand-"IC2000", aka "rubberized CA"). To spread the CA, I put a half drop between the magnets, and used an old broken GWS prop to push the glue up against the magnets (without moving them out of place of course). Once the glue was worked good around the magnets, I hit it with accelerator. No balancing was done before testing, although the blue & red rotor did vibrate a bit (the other 2 rotors spun smooth and true all the way to 40kRPM).

A note on cleaning the rotor before reinstalling mags:
The older blue & red rotor had brittle glue, which was extremely easy to remove from the rotor & magnets (flaked off in large chunks). The old school hxt rotor hardly had glue... if there was it was thin CA (some residue fell out as I popped out the magnets). The newer style black rotor had a more flexible glue on the magnets; that stuff took about 20min to scrape off the rotor with a utility knife after I pried the magnets out. The magnets won't clear the stator if you leave thick chunks of glue in the rotor. Remember the magnets are likely flat; it's hard to see after you pop the mags out, but underneath every mag is a crescent shaped glue chunk that needs to be worked down. Keep going until you start scraping flux ring metal... and work down as close to the hub as you can (so the mags don't hang out the back later on). I haven't tried it yet, but maybe a hot acetone bath will soften the glue so it can be easier to scrape off? Works on most adhesives, so someone might wanna try it.

Kev

[edit: Note on tweaked flux rings...

While you have the magnets out is the perfect time to double check the flux ring is fully pressed on the hub. The blue and red rotor I used came off a motor that had been plagued with poor benchmarks (5% substandard); only possible cause was the flux ring being about 0.5mm proud on one side. When I rebuilt that rotor for this experiment, I used my press to drive the flux ring home. The rotor no longer stood out as a dud. ]
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Old Oct 30, 2011, 02:42 AM
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328w !!!

My Eclipse flew OK with the 10P-12T-24awg-D at 260W. So why not push it harder? Although just flying it this weekend would be fun enough, just for you guys I put my latest creation on the stand this evening:

T2730-10p-6x2T-24awg-Y (3650Kv)
Rhino 3s1250 30c (full charge)
APC 4.1x4.1e
31301RPM/11.26V/29.1A/122mph/69.0% DCalc effy

There is a lack of props and no load... would have been fun enough to just fly it.

Efficiency is low on the bench, but the plane is slippery. 100W of dissipated heat is a whole lot for a 25gm outrunner to handle, but I'm not expecting problems with open air cooling at those speeds. Tomorrow's test flight should see around 130mph average. After a certain point increasing cell count becomes necessary. I doubt going beyond 3650Kv on 3s would be fruitful. So now I'm looking at a 2730-10p-8x2T-25a-Y 10p motor mounted on the test stand with a 4.1x4.1e attached, waiting for 4s. If I have time I'll try my 12D stator too... this is where I make the turn for the darkside.

Cheers,
Kev
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