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Old Jul 21, 2010, 03:50 PM
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Originally Posted by _Sergey_ View Post
Haha! I'll post it here. I did it myself and it's free
THX!!!!!!

If you posted a Youtube vid of the steps it would prolly become an EDF classic.

There's so many people that could benefit from this rather than spending 200 on a balancing machine.

TIA
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Old Jul 21, 2010, 03:56 PM
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That's a great idea! I'll think about it
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Old Jul 21, 2010, 05:30 PM
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That's a great idea! I'll think about it
I want royalties!!! JK Say, how'd you get an ad on your yt video?
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Old Jul 21, 2010, 07:11 PM
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Originally Posted by _Sergey_ View Post
That's a great idea! I'll think about it
I did a search for balancing an EDF on youtube and all I found was a guy balancing the impeller. It was a good intructtional vid but as I was doing just as he said it occurred to me that I was only balancing part of the EDF. I was rather chuffed to find your technique as it answered the questions I had about balancing the motor also.

So I have an iPhone and I have seen the Vibrations app but I also found a free one that may do the job as well. Its called AccelGraph. I havent had a chance to use it yet but I will and post any results.

Also, for stage 2 of the balancing of impeller. If you dont have any suitable magnets, before you go and try and buy any, check if you have any old computer hard drives around. You will not find a better/stronger magnet for no cost.
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Old Jul 21, 2010, 07:22 PM
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Originally Posted by _Sergey_ View Post
You are correct about precision. There are also ways how to achieve more exact angle without it being too tedious. To increase precision one extra step is needed. After lowest vibration angle A(min) is identified in step 1 follow step 1a:

Step 1a:
a) Position fan at the angle A(min)-30 degrees
b) Take measurement
c) Rotate fan by +10 degrees
d) Repeat steps b-c 7 times

The result should look like a U-shaped curve with the bottom point is the minimum point of vibration with accuracy of 10 degrees with just extra seven measurements.

Theoretically step 1a can be repeated with new A(min) and +- 10 degrees spread to narrow down the minimum point to a three degree angle. But it may not be practical. First it is much harder to manually rotate fan by three degrees. Secondly there is a measurement error that can be larger than the result making single measurement impractical. There are ways to include this error as a factor in the calculation but this is going to be very tedious job with dozens of extra measurements and may require some sort of automation, where computer or phone controls the throttle, not human.

I hope this is helpful.
Thats a much quicker way than I thought of. Brilliant!

One could get down to the finer degrees much easier by measuring the circumference of the impellers hub then dividing it by 360. This would then give a mm value to every degree thereby allowing you to move those smaller degree's more accurately.

eg. Hub is 250mm in circumference. 250 / 360 = .7mm per degree.
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Old Jul 21, 2010, 10:01 PM
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Originally Posted by _Sergey_ View Post
Here are two videos. First one is the maiden flight with unbalanced motors. Check take off and cruise sound starting at 0:55. Second is after engines are balanced. Don't mind the landing on both videos, it's a coincidence.

Unbalanced fans:
http://www.youtube.com/watch?v=musF6PdabHA

Balanced fans:
http://www.youtube.com/watch?v=AO9-AEERSiI
No comparison! The balanced fans are waaay quieter and smoother
Now I'm stoked to remove the fans out of my edf's and re-do them the "Sergey" method!
BTW, nice flying Sergey What A380 model is that? the Windrider one
Thanks again for the info
Z
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Old Jul 21, 2010, 11:18 PM
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Originally Posted by jzuniga View Post
What A380 model is that? the Windrider one
Thanks! This one is not a Windrider. I bought it from pw-rc.com.
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Old Jul 22, 2010, 02:10 AM
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Originally Posted by jzuniga View Post
No comparison! The balanced fans are waaay quieter and smoother
Now I'm stoked to remove the fans out of my edf's and re-do them the "Sergey" method!
BTW, nice flying Sergey What A380 model is that? the Windrider one
Thanks again for the info
Z
You realize Sergey that you are going to be known as a pioneer and legend in the halls of RC Fame? As jzuniga says it will be known as "The Sergey Method"!

The Curtis Youngblood of EDF's!!
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Old Jul 22, 2010, 02:47 AM
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Originally Posted by Fubar69 View Post
You realize Sergey that you are going to be known as a pioneer and legend in the halls of RC Fame? As jzuniga says it will be known as "The Sergey Method"!

The Curtis Youngblood of EDF's!!
Especially if he puts out a YouTube video and it appeals to the masses... ie, us dumb dumbs when it comes to fan balancing... hehe
Z
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Old Jul 22, 2010, 02:06 PM
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Hehe, thank you guys! I'll work on the video, probably covering alternative method.
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Old Jul 22, 2010, 02:32 PM
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Alternative balancing method (no screw drivers or magnetic balancers)

Alternative balancing method


What ifÖ you cannot rotate the fan? It may be glued to the shaft or impractical to unmount, the fan itself is statically balanced or you are allergic to a screw driver and magnetic balancer gives you a headache? Can EDF unit still be dynamically balanced? Unless laws of physics prove opposite the answer is YES!
Here is howÖ

Theory


Letís take a look at the EDF system and centrifugal forces when unit is working.



Unbalanced fan produces force that is applied to the center of rotation (shaft) and directed toward its heaviest point (blue arrow). Unbalanced motor creates its own force which applied to the same center and directed toward its own heaviest point (green arrow). The resulting force of EDF system is sum of these two vectors (red arrow). In previous method fan unit is rotated to compensate one force with another. But what ifÖ we create our own force to compensate?

Take a look at the image below.



By creating new counter force in our EDF system we effectively compensate existing force responsible for vibration. All we need is add counter weight at the right location. The steps remain the same. In Step 1 we find that location and in Step 2 we add necessary weight to compensate unwanted force.

Before we start practical implementation there is one important point that deserves its own discussion. Where, or more precisely how far from the center of the shaft counter weight should be located? This may seem obvious but wrong place can result in unexpected consequences. The problem is the force created by rotating mass is proportional to the radius of rotation. Another words, one gram added to the blade tip creates stronger force than one gram added to the hub. This results in one level of vibration at low RPM and completely different vibration at higher RPM. For outrunner motors correct distance from the center of the shaft is where magnets are glued to the rotor. For inrunner motors answer can be more complicated, or instead much simplier, and probably should be discussed separately.


Practical implementation


First of all we need to find place on the Fan unit where counter force needs to be applied. We need couple of small squares of sticky tape. How many exactly can be determined experimentally. The counter weight should be small enough to not create too much stress and heavy enough to make measurable difference in balance.


Step 1
a) Mark fanís hub with a sharpie every 45 degrees. Make one of the marks different Ė it will be a starting point
b) Stick counterweight to the starting point
c) Start sensorís data recording
d) Gradually increase motorís RPM to the max and back during approximately 10 seconds interval
e) Stop recording and save result file
f) Un-stick counterweight and move to the next point
g) Repeat steps c-d-e-f until you reach angle of 315 degrees, which will be the last measurement point.

The result should look very similar to the spider chart produced by Step 1 in previous method. There will be a minimum vibration point where weight needs to be applied to compensate vibration.

Step 2

a) Stick counterweight to the minimum vibration point of the fan
b) Add one more piece of tape
c) Start sensorís recording
d) Gradually increase motorís RPM to the max and back during approximately 10 second interval
e) Stop recording and save result file
f) Repeat steps b-c-d-e few times

The data analysis is exactly the same as described in previous article.

This method is less labor-intensive and much quicker than previous one. No screw drivers, no fan balancers, just phone and masking tape.
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Old Jul 22, 2010, 03:06 PM
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Please...please youtube this...we can start a Sergey Fund...it'll be worth your time no doubt
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Old Jul 23, 2010, 02:25 AM
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Man you are just a genius . thank you very much for sharing

So has anyone find an app that can we use on iphones that export to csv file ? is Spectrum Analyzer okay?
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Old Jul 23, 2010, 09:12 AM
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Possible DIY solution if you don't have a cell phone with accelerometer....

http://www.dimensionengineering.com/...ter/Gmeter.htm

Around 40 dollars in parts...

I was also thinking another less expensive but less precise way to go was a glass of water and a home made EDF stand that was beefy and enough area space on the stand to put a glass of water.

Put the glass of water as close to unit as possible, the more ripples in the water throughout the rpm range the less balanced the fan is using your second method.

Sergey this is genius, I love the sound of balanced EDF fans
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Old Jul 23, 2010, 10:12 AM
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Originally Posted by iamzoli1 View Post
Man you are just a genius . thank you very much for sharing

So has anyone find an app that can we use on iphones that export to csv file ? is Spectrum Analyzer okay?
I downloaded "Vibration" on the app store on my iphone and it seems to be what I need?...
Z
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