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Old Sep 20, 2014, 01:49 AM
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Joined Apr 2012
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Discussion
unbalanced fan in half throttle

Hello everyone,
I wanted to ask what could be the reason
the Fan unbalanced in half throttle
And about a third throttle it sounds balanced
You can hear at 1:07 in the video
Thanks in advance
Nati.
taft viper 90mm 8s (2 min 28 sec)
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Old Sep 20, 2014, 08:27 AM
Extreme CNC Alloy EDF
Extreme_RC's Avatar
Australia
Joined Mar 2006
11,545 Posts
Simply, it hasn't been properly balanced dynamically before it was fitted. You will need to remove it and then pull the spinner, check the rotor is running in balance first then fit and clock the spinner, if you cannot get it perfect you will need to add weight to the inside of the spinner. It can be done without specialized tools but will take some time if you have not done it before, and you might not get it perfect.
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Old Sep 20, 2014, 04:13 PM
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Thank you extreme
I'll try to balance as you said
By the way it is possible to fly without spinner?
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Old Sep 20, 2014, 10:35 PM
Calm before the storm
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United States, TX, Bullard
Joined Jun 2014
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it is possible because I use an Electrifly Ammo Brushless and it says in the maunal that the spinner, or nose cone adapter as they call it is arbitrary.
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Old Yesterday, 04:24 AM
Extreme CNC Alloy EDF
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Australia
Joined Mar 2006
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Yeah no issues without spinner, I seem to recall in the wemo white papers Oliver spoke about a vacuum in front of the rotor at the centre, making the spinner absent no issue. Need to look them up to confirm what he was saying.
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Old Yesterday, 05:56 AM
Big gov never Works
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Skunk Water, Rhode Island
Joined Jul 2002
12,327 Posts
I read the same thing, Mark. But yrs ago, Oliver wrote this, when normal power was 200-500W. Then mentioned again(by Oliver) when the Mini-Pro alum spinner came out.

I sometimes need to use a piece of masking tape inside the spinner. If it does not work, move the tape 45deg. If that makes it worse, move it back 180deg. It only takes a second to remove the spinner and find the proper place for the tape. And it's worth every effort.

Noise it not the only issue, airframe failure can occur and efficiency is less, un-balanced. This one reason(plus the bad noise) that I stopped using HET fans. No spinner to clock. And most times running the rotor in a different position on the shaft is a no-good.

Fuzz
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Old Yesterday, 08:18 AM
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Joined Apr 2012
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Thank you all for the comments
I tried to clock the spinner but did not help
Finally I pulled out the spinner and now it running Without vibrations
I guess I'll leave it without the spinner

nati.
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Old Yesterday, 12:38 PM
AKA Terry Till
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Alexandria, VA
Joined Apr 2002
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Quote:
Originally Posted by St. Martin View Post
I read the same thing, Mark. But yrs ago, Oliver wrote this, when normal power was 200-500W. Then mentioned again(by Oliver) when the Mini-Pro alum spinner came out.

I sometimes need to use a piece of masking tape inside the spinner. If it does not work, move the tape 45deg. If that makes it worse, move it back 180deg. It only takes a second to remove the spinner and find the proper place for the tape. And it's worth every effort.

Noise it not the only issue, airframe failure can occur and efficiency is less, un-balanced. This one reason(plus the bad noise) that I stopped using HET fans. No spinner to clock. And most times running the rotor in a different position on the shaft is a no-good.

Fuzz
I agree with you Fuzz.
I have two HET 6904 fans. Both needed additional balancing (tape on the inside) and both needed a few iterations of re-positioning on the shaft to get running smooth.
Never the less, the HET 6904 and EFlite Delta V-15, with their unitary impeller need a little more effort to get running smooth, as there's no spinner to clock.
Getting the shaft adapter to run true is the linch pin to getting a fan to run smooth. Otherwise it'll vibrate at certain throttle positions.

JMHO,

Terry
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Old Yesterday, 04:29 PM
Big gov never Works
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Skunk Water, Rhode Island
Joined Jul 2002
12,327 Posts
I did have one 6904 run perfect, plus I cut one down to 64mm(before the HET version was avail), it ran perfect too. But the high pitch whine was not good. A well balanced minifan, even pre Pro models are quite quiet. The HET sounds like one of my old Kirn Kraft .051's on 40%!

I have a few really old minifan rotors, before they were glass filled. These work better than the glass filled ones at -500W. The blades are thinner and sharper. Quieter than the glass filled.

Fuzz
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