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Old Jan 01, 2014, 11:34 AM
Su-27's Rule!
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Blue wonder motor.
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Latest blog entry: A cheap way to measure Kv
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Old Jan 01, 2014, 12:31 PM
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Look it up in this zipped XLS, albeit from much earlier in This thread.
There is a later RBW version, but this place won't accept XLS files ..
Search for it? If this one doesn't give answers you like :-)
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Old Jan 01, 2014, 12:34 PM
just an earth-bound misfit
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Quote:
Originally Posted by su33seaflanker View Post
Blue wonder motor.
He is asking for specifics. There are 2 versions (HXT and Turnigy) mentioned in this thread. Of those two versions, there are different kv's available which have different numbers of magnets and are wound differently.
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Old Jan 01, 2014, 12:53 PM
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Assuming we're not talking about custom magnets and we are not going OT discussing the Hex version, then there are 4 possible answers to the question. Going off of my Turnigy 2730 database:

14P-16T-Y = 1132 Kv
14P-16T-D = 1960 Kv
16P-16T-Y = 1159 Kv
16P-16T-D = 2007 Kv

So with Turnigy cores you'll get roughly 1150 with Y and 2000 with Delta. Just in case... a Hex would come in around 1050 and 1800 respectively. In my experience, the delta is a potent wind, and the Y is a bit too low for most applications.

Cheers,
Kev
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Old Jan 01, 2014, 08:36 PM
Su-27's Rule!
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thanks guys sorry, its 14p 16t and i did this winding
ps what is the stator height?
edit: checked bare's chart now 14p 16t should be ~1800kv but when i got the motor before it had 1500kv specs...and same no# of turns. how could that be? also my motor seems to have gone down in kv because it's not heating up, for the same prop as it did before...
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Old Jan 02, 2014, 07:45 AM
Jack
USA, ME, Ellsworth
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Quote:
Originally Posted by su33seaflanker View Post
thanks guys sorry, its 14p 16t and i did this winding ..<snip image>...

ps what is the stator height?
edit: checked bare's chart now 14p 16t should be ~1800kv but when i got the motor before it had 1500kv specs...and same no# of turns. how could that be? also my motor seems to have gone down in kv because it's not heating up, for the same prop as it did before...
That is the wind we call the dLRK for Delta wind. It brings the wires that will be joined for the Delta termination out side by side.

In that wind image the view is looking at the top of the stator, if you look at the side of the stator, that would be the length or height of the stator with the difference being whether is it setting on one end or laying on it's side. In most cases when we mention a 22mm stator we are talking about the diameter of it. And if we mention a 2216mm stator it would be 22mm in diameter and 16mm long or high. Some motors model names use the dimensions of the stator and others use the dimensions of the finished motor. So one man's 2216 motor might be the same motor as another man's 2820 motor.

The Kv is unique to the parts in the motor. If you have two 12N14P motor that are not made with stators of the same length and from the same production run you will get different Kv's. And if they have magnets that are not from the same production run the Kv will not be the same. So a blue wonder and a red wonder and a blue and red wonder with the same arm and pole count and the same turn count will have three different Kv's.

And when you factor in the missing or crossed or miscounted or misplaced windings that are found in the stock motors, the actual Kv's that will result can change again. And then you can find 1800 Kv motors that were sold as 1500 Kv motor due to mistakes in marking the motors, packaging the motors, or dealer having sent you the wrong motor.

If you go to Truglodite's blog page, click on the Continue reading... link, scroll down to the Extra's listing, you will find at least three spreadsheets there about wonder motors (rewind-BRW, rewind-RBW, and rewind-BW) and those are the gold mines for finding the history and details of everything worth knowing about three distinctly different generations of wonder motors.

You can extract the M$ Excel formatted *.xls spreadsheet files from the *.zip archives. Then you can download and install the free OpenOffice software suite and it will open the *.xls fils and you can see the details with the Open Office Calc application. In most cases, just printing a screen shot of the info will give you all you need as far as re-winding info (turn counts, Kv's, terminations, etc.) but there is also a ton of testing data there from previous rewinds and with various props too.

So the bottom line is that you have to look at the data for the right motor to get the same results. And even then, there will be some variation in the resulting Kv's that are caused by minor changes in the components (magnet air gaps for example) and who measures the Kv and how it is measured.

Jack
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Old Jan 02, 2014, 09:59 AM
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Quote:
In that wind image the view is looking at the top of the stator, if you look at the side of the stator, that would be the length or height of the stator with the difference being whether is it setting on one end or laying on it's side. In most cases when we mention a 22mm stator we are talking about the diameter of it. And if we mention a 2216mm stator it would be 22mm in diameter and 16mm long or high. Some motors model names use the dimensions of the stator and others use the dimensions of the finished motor. So one man's 2216 motor might be the same motor as another man's 2820 motor.
yes i get this.. my motor's written as 2206 and according to my research it's very similar to this thread's motor and thus written under this thread rather than a new thread..

Quote:
The Kv is unique to the parts in the motor. If you have two 12N14P motor that are not made with stators of the same length and from the same production run you will get different Kv's. And if they have magnets that are not from the same production run the Kv will not be the same. So a blue wonder and a red wonder and a blue and red wonder with the same arm and pole count and the same turn count will have three different Kv's.
ah ok,so the only way to get an accurate read is to get a tach and watt meter?
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Old Jan 02, 2014, 10:13 AM
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I used one of these. Easier to use than a tach+wattmeter and seems as good for my purposes.
http://www.hobbyking.com/hobbyking/s...rch=kv%20meter
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Old Jan 02, 2014, 03:24 PM
Jack
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"..ah ok,so the only way to get an accurate read is to get a tach and watt meter?..."

There are several ways to measure the Kv. You can read about those here:

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

The easiest way is to get what is called a "raw" Kv by running the motor up to full throttle with no prop on it and measuring both the RPM and the pack voltage as the same moment in time. That will be a little different, a few percent or so, than Kv as it is measured in a motor laboratory. But it is accurate enough for what we are doing.

The HK tool that flydiver mentions give you a raw Kv even though they do not say that. And it is a good tool as far as I know (I have not used one).

I use a eLogger V3 or V4 and that measures and records RPM and voltage simultaneously all the time so it is very easy and quick to use it to get a Kv.

You will never get a Kv measurement with any method that agrees rexactly with the advertised Kv. It will always be at least a little different. And sometimes it will very different, even hundreds of RPM different.

A watt meter (the eLogger is that too) measures voltage and current (Amps) and calculated the power in Watts (volts x Amps = Watts). It is an essential and wonderful too and everyone should have one. A tach is needed to measure the raw Kv as I describe it.

An eLogger with the essential (and optional) accessories for most of the things we want to do will cost you around $100 or so. Good watt meters cost from $30 to $70 or so. The eLogger is small enough that it can be used in flight in most cases and that makes it even more useful.

Jack
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Old Jan 02, 2014, 04:27 PM
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Before I got the KV-meter I used a tach+wattmeter. The wattmeter has a LOT more uses and is a decent tool to have....period.
I rarely use the tach anymore. I don't know if it was MY tach or a general tach problem I've only used the one I have) but I had trouble getting reliable RPM readings. I used LED lights on the motor, BIG stripes on the outrunner can, fluorescent light off.....etc.
The meter is much less of a hassle, can be set up in a couple minutes and for me seems more accurate.
The eLogger seems very cool but more than I want to invest.
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Old Jan 02, 2014, 06:48 PM
Jack
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Using hand held tachs can be challenging. The lighting and other things can effect the readings. With props, I usually hold a flashlight on one side of the prop and shine it into the tach on the other side of the prop. That will usually get a fairly stable and accurate reading. But sometimes the will be all over the place Without props I put a wrap of masking tape around the housing and make two opposed black marks on the tape and shine the flashlight on that.

The reason a watt meter and a tach will work for measuring Kv's is because most or all watt meters display Volts, Amps, and Watts with the latter being calculated from the first two. So if you have a watt meter connected and you glance at it to get the pack voltage as you take the RPM reading you have the info needed to calculate the raw Kv. With a 3S pack if the no load RPM is 15,678 and the pack voltage is 12.1V the raw Kv would 14,478 / 12.1 or 1196. And the motor would have probably been sold as a 1200 Kv motor.

With the eLogger I zoom in on a 3 to 5 second period with the motor at full throttle and with no load on it and the software gives me the average RPM and voltage for that period of time in that summary box at the bottom. It is not easy to read in the image but in that case the average RPM was 16940.52 and the average voltage was 6.26V so the Kv was 2706.

Jack
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Old Jan 03, 2014, 08:56 PM
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That is a clever workaround (easier than using a drill motor to spin the motor thank you.
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