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Old Jan 22, 2010, 12:13 AM
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Truglodite's Avatar
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Yep, wouldy is right. That wiki is also right, it does appear contrary to logic at first.

Dave, that means your thrust stand readings should be lower, not higher? Eh well, things can be finicky I suppose.

Thanks,
Kev
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Old Jan 22, 2010, 10:56 AM
Dave North
timocharis's Avatar
USA, CA, San Jose
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Quote:
Originally Posted by Truglodite View Post
Dave, that means your thrust stand readings should be lower, not higher?
Maybe so, but the consistency of the issue is interesting (and there is doubtless something I'm overlooking). My take on theory vs reality is: when the data contradicts the theory, the theory is incomplete.

Or wrong.


Dave
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Old Jan 22, 2010, 12:52 PM
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Atlanta
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Need some help please

I have just purchased a 2730-1300 from HC to put in my Micro Tele and I'm having some problems with it I can't figure out.

It won't start up on its own. It chatters back and forth and sometimes it will start not always. Most times I have to hand prop it to get it going. I've read that this might be caused by bad connections, so I replaced the wires and resoldered the bullett connectors, with no improvement. I'm using a Hyperion Tition 10A ESC and a 8x6 SF APC prop. I've tried all sorts of different ESC settings as well, (8kHz & 16 kHz switching, soft, hard and auto timing, soft start off etc...)

Any suggestions? I'm thinking I might need to rewind it (never done that, but willing to try)

I've noticed that this motor has a REALLY strong magnet pull as I turn it by hand. CLICK, CLICK, CLICK. Is it because this one has 16 magnets? I have another Turnigy motor (28-03 ? I think) of the same diameter with 14 magnets and it is much smoother when turning by hand.

Thanks!
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Old Jan 22, 2010, 12:59 PM
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Got my motors yesterday well packed and they have the big letters on them..make that huge letters.

Quote:
Originally Posted by going4speed View Post
I finally found a US supplier of the turnigy red and blue wonder in 3000kv!!!

I am so excited and can hardly type this.

Any order over $27 ships free.

No I dont know or own anything related to this company.

Just glad to not order from Hobby city and wait 482 years for my order (no its not that bad but you know...)

I just placed an order I will let y'all know when I get it

http://montorc.com/
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Old Jan 22, 2010, 02:13 PM
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Conroe, TX
Joined Apr 2007
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Same here. 2 of the three had huge letters and 1 had medium letters. All appeared to be the same as my friends 3000kv version. The wires were very close to the bell, and in fact I felt rubbing on one of them. They will be rewound anyway, so no big deal there. However, I found that the first one I rewound had 2 shims, one at each end. One was about double the thickness of the other one. So, I reversed them to give myself an extra 0.2mm or so extra clearance. The stator pokes out by about 1 stator plate. The wires all fit so, it worked nicely. 12t of 24g dLRK Delta. Here's a run on my Eagle Tree, that I'm just getting used to. I ran it no load, to get the RPM, and then threw on a 4.7 x 4.7 Graupner CAM speed prop. Kv came out at about 2678. Io is 1.4A 33000 rpm 12.5v.

24,200rpm with prop on at 11.7v for 250W peak.

Of course it won't be flown continuous like that. I ran it WOT for a bit on the bench and it was smooth. It got warm, but no problems. I ran it in pusher and it was very smooth and quiet. This is going to scream on a 10oz 28" wingspan flying wing. That is 400W per pound
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Old Jan 22, 2010, 03:40 PM
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Conroe, TX
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Also, those 2 graphs don't show the temp reading because it made the left scale go up to 100, so amps and volts were way down low. I left it logging at the end of the run. Peak temp was 115F after the end of the WOT run. Before this logged run I had run it at WOT for 30 seconds, and no problems. the prop is turning at 77% of the Kv, so it's not overloaded based on what I am seeing. So, 10 watts per gram out of these tiny little outrunners, and I'm betting the efficiency is not too bad. I don't know how to find that out though. I don't have a thrust stand yet.
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Old Jan 22, 2010, 04:44 PM
Dave North
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Quote:
Originally Posted by Fuegodeth View Post
24,200rpm with prop on at 11.7v for 250W peak.
!!!

Dave
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Old Jan 22, 2010, 05:06 PM
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Speechless?
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Old Jan 22, 2010, 05:34 PM
Dave North
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mmm.

Dave
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Old Jan 22, 2010, 05:46 PM
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Lol
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Old Jan 22, 2010, 06:09 PM
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Conroe, TX
Joined Apr 2007
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OK, these numbers are insane. This is my first time to run something through badcock. I took rpm, amps and volts from same spot on eagle tree chart at middle of WOT run.

11.7v
21.4A
23,119 RPM
88.9% efficient
Current temp in garage is 74 degrees, just north of houston, about 10M over sea level.

I might have to run that again to double check, because if it's right... then I think it's awesome.
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Old Jan 22, 2010, 06:12 PM
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Attached calc sheet
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Old Jan 22, 2010, 06:31 PM
Dave North
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Hmm. Curiously, when I run the same numbers through DriveCalc they give a higher thrust reading but an efficiency of 70.9% ... they don't usually disagree so much! To tell the truth, I'm kind of suspecting DriveCalc may be closer to reality on this one, but either way it's an excellent result for such a power level from that little crank!

Dave
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Old Jan 22, 2010, 06:42 PM
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I agree. That will be used in burst anyway, so this thing should run really cool. I'm using a Thunderbird 36 because that's what I have on hand. It's going on a sleek little 28" flying wing with AUW about 10oz or so with 1000mah 3s or 11oz with 13503s. I cut the wires down very short on the esc, and it still weighs about as much as the motor does . I will eagle tree the flight once I get the plane finished and that will be cool to see what the in flight rpm, temp, etc are. That prop is meant for speed, and I don' think it's getting full bite on the bench. I will say that it was fairly quiet for that amount of power out of a pusher. The prop has a good couple of inches of clearance from the trailing edge, so it's getting pretty clean airflow. These little heatsink/clamp/stick mounts really make it easy to put these little motors in the perfect location on a little flying wing.
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Old Jan 22, 2010, 06:57 PM
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Wow Fuegodeth, that's insane! I suppose it'll be moving so fast that it won't matter how much heat is there.

The problem with taking readings from one "spot" is that spot might contain a "twitch" in the data. For example, looking at data from a bench test I did today, there are efficiencies in the middle of the WOT region ranging from 75.8% to 79.6% (~5% error). That could be even worse, as that test had very "clean data". Instead of picking 79.6%, I log at 10Hz and take an average over at least 1sec. From that same test, the 1sec average was 77.6%, with a "standard deviation" of +-0.9%. So averaging data reduced the error to less than 1/5 versus picking a spot on the graph. Averaging per-point efficiencies, is different than averaging RPM and power and plugging in to calculate efficiency, but that's why I use a spreadsheet.

Kev
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