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Old Dec 06, 2012, 09:53 AM
alexandermh is offline
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I sent them a PM and they told me they would have parts for new units in the Jan - Feb time-frame.
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Old Dec 06, 2012, 05:34 PM
PeterVRC is online now
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My email said the same (of course).
So no more Vortex Xmas presents!
Old Dec 09, 2012, 11:22 PM
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Good vibrations.
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Large EDF's


Someone asked me about balancing outrunner EDF units. I recently repaired my Ramtec EDF and ran it through the Vortex to check balance.

The first thing you will notice is that the imbalance signal has a shaky waveform. The "shakes" is due to the commutation frequency of the motor. Hidden behind the shakes is the rotor imbalance.

After applying the filter, the commutation is mostly removed and the imbalance signal remains. It is not possible to totally eliminate the commutation as it has already exceeded the limits of Vortex. But you can see what is happening.

After balancing the vibration amplitude was reduced from 10mv down to 6.5mv. This indicated that the Ramtec was fairly well balanced. I could tweek it much more though but this post is to demonstrate the commutation effects.

cheers

DH
Old Dec 09, 2012, 11:28 PM
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Good vibrations.
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Smaller EDF's


Here is an example of my Wemotec 90mm EDF. This is the unbalance version. Pre balance vibration was 14mv. Post balance was 5mv (first pass). The cradle seemed to work well with it.
Old Dec 10, 2012, 08:47 AM
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Hey!


. That looks suspiciously like a power supply feeding the fan.....instructions tell us not to use power supplies, and use batts instead.

Love it, and now like a kid awaiting Christmas. Really too excited to wait.... Next time she goes out, there's gonna be a raid.....
Old Dec 10, 2012, 09:03 AM
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Quote:
Originally Posted by PikeStaff View Post
. That looks suspiciously like a power supply feeding the fan.....instructions tell us not to use power supplies, and use batts instead.

Love it, and now like a kid awaiting Christmas. Really too excited to wait.... Next time she goes out, there's gonna be a raid.....
roflmao! be sure to tape all packages back together
Old Dec 10, 2012, 12:41 PM
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subscribed!
Old Dec 10, 2012, 06:27 PM
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Quote:
Originally Posted by PikeStaff View Post
. That looks suspiciously like a power supply feeding the fan.....instructions tell us not to use power supplies, and use batts instead.

Love it, and now like a kid awaiting Christmas. Really too excited to wait.... Next time she goes out, there's gonna be a raid.....
I don't know who said that, but they don't know what there talking about. "IF" you have the right power supply, its better that using a battery. especially if you doing power and efficency tests.

Larry E.
Old Dec 10, 2012, 06:43 PM
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Originally Posted by LJE4357 View Post
I don't know who said that, but they don't know what there talking about. "IF" you have the right power supply, its better that using a battery. especially if you doing power and efficency tests.

Larry E.
The purpose was due to noise induced by the power supply to the power head; that noise can be picked up by the spectral analysis and can be interpreted as yet another source of vibration that you're trying to eliminate.

And testing with a power supply is indeed wonderful for bragging rights, and/or absolute results. They're completely worthless for testing comparative to real-world applications, as there isn't a battery in the universe that can hold constant, unwavering voltage and amperage output.
Old Dec 10, 2012, 08:47 PM
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Quote:
Originally Posted by PikeStaff View Post
The purpose was due to noise induced by the power supply to the power head; that noise can be picked up by the spectral analysis and can be interpreted as yet another source of vibration that you're trying to eliminate.

And testing with a power supply is indeed wonderful for bragging rights, and/or absolute results. They're completely worthless for testing comparative to real-world applications, as there isn't a battery in the universe that can hold constant, unwavering voltage and amperage output.
Actually there is a battery that gives constant voltage for a time period. It's a thermal battery. I designed a switcher thats variable from 5V dC to 80V dC 400A, 1% regulation. The switching frequency is 10K hz. and control loop bandwidth is 8khz. Thats pertty high frequency to translate to vibration at any reasonable amplitude. But it will be there. Ballancing a rotor can be tricky. I'm sure that you have ballanced a rotor as close a you can get it. Then in actual running of the fan there is an RPM in which the rotor virbrates, but it get faster and the vibration quits. Usually caused by the natural ressonante frequency of the rotor assembly, You can not get rid of it, but you can move it to a frequency above an RPM you will never see.

Larry
Old Dec 10, 2012, 08:58 PM
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That would do it for sure - at those freqs it's improbable that any harmonics could be induced, at any honestly discernable amplitude. And you are spot-on with natural resonance; even we have our own .

We've certainly come a long way with batts over the past decade or so. Hope to see comparable improvements over the next.
Old Dec 10, 2012, 09:10 PM
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Good vibrations.
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The high frequency I saw appeared to be from the motor/switching. The Scorpian on the Ramtec EDF has fairly strong "cogging" effect from the magnetic poles.

I rotated the fan by one revolution and counted 24 clicks. When you look at the signals, the high frequency signal is 24 x RPM. I guess this is from the motor poles. The amplitude from the high frequency signal is high and likely induced by some physical force (EMF?). I'll let the motor experts debate this.

Having said that, I did see electrical noise transmitted down Vortex in the early days. Switch mode power supplies connected to Vortex were terrible and caused me grief. If you see a 50 or 60Hz signal superimposed then you know it's the power supply. I recommend batteries because it is one less thing to worry about.

good luck,

DH
Old Jan 03, 2013, 08:42 PM
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Question


DH, can you advise scale for the balance sheet? Manual says they can be found in the appendix.....but I'm not finding that.
Old Jan 03, 2013, 08:55 PM
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Is it possible to do the strobe balance without a spinner? If so, how (i.e. where would you put the line for the strobe)? Thanks.
Old Jan 03, 2013, 09:01 PM
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Could put the line on the face of the hub - then align the strobe straight in.


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