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Old Nov 30, 2010, 07:13 PM
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Philipp's Avatar
Grand Prairie, Texas, USA
Joined Mar 2000
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Turnigy Motor Mis-Labeled

I have installed a new Turnigy SK3548-900 on my Dh-2 Beaver. I am using a Turnigy Plush ESC with 4S A123 2300mah cells. The system seems to have plenty of power (have not flown it yet), but the software programs predict different values to what I am seeing. I also changed the timing on the ESC from mid to high with little effect.

Online ECalc and Electricalc both predict well over 8,000 rpm with the APC E 11x7 prop. I am measuring 7,700 rpm with a tach. I thought the tach was bad, but it reports the incandescent lights at 3,600 ppm. (60 cycle current).
If I plug 700 RPM/V into the program, all figures (RPM, amps and watts) come out a lot closer.
I know that these motors are notorious for misstating the kV, but 700 instead of 900 ?

Am I possibly missing something or is this really a 700 kV motor?
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Old Nov 30, 2010, 07:21 PM
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Quote:
Originally Posted by Philipp View Post
I have installed a new Turnigy SK3548-900 on my Dh-2 Beaver. I am using a Turnigy Plush ESC with 4S A123 2300mah cells. The system seems to have plenty of power (have not flown it yet), but the software programs predict different values to what I am seeing. I also changed the timing on the ESC from mid to high with little effect.

Online ECalc and Electricalc both predict well over 8,000 rpm with the APC E 11x7 prop. I am measuring 7,700 rpm with a tach. I thought the tach was bad, but it reports the incandescent lights at 3,600 ppm. (60 cycle current).
If I plug 700 RPM/V into the program, all figures (RPM, amps and watts) come out a lot closer.
I know that these motors are notorious for misstating the kV, but 700 instead of 900 ?

Am I possibly missing something or is this really a 700 kV motor?
Turnigy is (from what I understand) simply HobbyKings name for what ever motor they get from whatever vendor, and then they simply slap a Turnigy label on it. Yep, I've read of many stories here where the actual kV value is not even in the same ballpark as the advertised specs.
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Old Nov 30, 2010, 07:26 PM
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United States, CO, Denver
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Philipp, if you have a Wattmeter, check to see what the battery voltage is under load. The Kv rating is RPM/Volt, so if your battery voltage is dropping under load, your RPM will be lower also.
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Old Nov 30, 2010, 07:53 PM
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Challenger 413's Avatar
Dickinson, Tx.
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Quote:
Originally Posted by NoFlyZone View Post
Turnigy is simply HobbyKings name for what ever motor they get from whatever vendor, and then they simply slap a Turnigy label on it
Hmm, can you provide us with links to prove it?

From the motors I've used other than HK, there is a slight difference in published versus actual readings..

Challenger413
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Old Nov 30, 2010, 07:57 PM
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Philipp's Avatar
Grand Prairie, Texas, USA
Joined Mar 2000
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Yes, the voltage dropped, as expected, and predicted.

The measured, resting voltage (no power ) was 14.4V and under power, 11.7v

The watts were approximately 320 instead of the 404, as predicted.

Just bad labeling, I guess as posted by NoFlyZone. I am tempted to go to a bigger prop to try and get the watts up.
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Old Nov 30, 2010, 08:01 PM
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Prove it!?? C'mon 413... Every HK motor I've ever bought has been distinctly 'different ' from the previous one. Likely they ('Jason' or whatever this weeks Anglicised name is) has some vague specification than gets farmed out for competitive bidding.
The only surprising thing here is Your surprise.
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Old Nov 30, 2010, 08:08 PM
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Originally Posted by Challenger 413 View Post
Hmm, can you provide us with links to prove it?

From the motors I've used other than HK, there is a slight difference in published versus actual readings..

Challenger413
Hi Challenger,

One question before I attempt to answer your question please. Why did you selectively cherry pick my post and conveniently leave out the part where I said "from what I understand" ?

It took an effort on your part to make sure you left that out when you supposedly 'quoted me'.

Here is what I said.... "Turnigy is (from what I understand) simply HobbyKings name for what ever motor they get from whatever vendor, and then they simply slap a Turnigy label on it."

Here is what you quoted me as saying... "Turnigy is simply HobbyKings name for what ever motor they get from whatever vendor, and then they simply slap a Turnigy label on it."

I might be stupid because I was born at night, buddy; but not last night.
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Old Nov 30, 2010, 08:13 PM
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Chattanooga, Tennessee, United States
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The measured, resting voltage (no power ) was 14.4V and under power, 11.7v

That means you must have a lousy battery pack...that amount of voltage drop under load suggests that it simply cannot supply what the motor requires....

If they compute 404W at 13.5v (about what you expect from 4s Lipo under load)... that's around 30A.

You get 320W at 11.7v...that's around 27A.

Seems to fit!
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Last edited by Dr Kiwi; Dec 01, 2010 at 06:59 AM. Reason: Missed the fact you were using A123
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Old Nov 30, 2010, 10:11 PM
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Philipp's Avatar
Grand Prairie, Texas, USA
Joined Mar 2000
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I just checked the battery pack to see what the reported IR is.

My iCharger reports it as 11, 11, 12 & 11 mOhm. I thought that was about normal as I have seen most of the 123 cells at 8 or so.
Could there be another big loss in the system?
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