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Old Jun 13, 2012, 09:54 AM
Groundloop World Champion
old_dude's Avatar
USA, AZ, Glendale
Joined Jan 2002
1,178 Posts
Question
EDF Impeller Balance

Hi,

I'm in the process of balancing the fan of a HET 6404 EDF.
I'm using a Tower Hobbies magnetic balancer.

Seems the fan was balanced at the factory BUT my magnetic
balancer says the factory put the epoxy weight in the WRONG
place !! Yep, Every time I spin the fan the side with the factory
added weight comes out on the bottom

Has anybody experienced such an error by the factory ???

Thanks

Old_dude

My first venture into the EDF world
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Old Jun 13, 2012, 10:45 AM
EDF all the way!
bruff's Avatar
Gilbert, Az
Joined Jun 1999
7,957 Posts
There is a difference between static balance and dynamic balance. Have you tried running it up? HET are dynamic balanced.
Bob
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Old Jun 13, 2012, 11:07 AM
Groundloop World Champion
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USA, AZ, Glendale
Joined Jan 2002
1,178 Posts
Waiting for the motor ... not yet.

Thanks
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Old Jun 28, 2012, 08:46 AM
Registered User
United States, AR, Jacksonville
Joined Jul 2004
451 Posts
I was under the impression that dynamic balancing is done on the combination of both the fan and the motor married together. Seperating and not using the two components together would disrupt the combined balance. Am I wrong?

If I'm not wrong, then there's a possibility the factory motor used for the balancing is imbalanced itself. The factory would have added the weight to account for this during the process. The result would be a fan, that by itself, is not in balance. It would only be balanced on the motor it was calibrated on, and only if it remained in the same clock position on the motor shaft at the time of calibration.

I would readjust the weight as you see needed with your own balancing methods, since you don't have the full set up that the fan was balanced with.
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Old Jun 28, 2012, 09:00 AM
AKA Terry Till
ex-racr's Avatar
Alexandria, VA
Joined Apr 2002
1,517 Posts
If you're talking about the Top Flite balancer, most of the shafts are not absolutely straight.
If it's bent a little, it'll give you misleading results.
If you use the finger tip balancer with the magnets you get much better results:
http://www3.towerhobbies.com/cgi-bin...?&I=LXK247&P=7
You should be able to move the fan by barely breathing on it. If you can't, there's too much friction somewhere.
FWIW, I've had to refine the balance of the 6904 70mm fans with little bits of tape to get them perfectly smooth.
It's also possible some one at the factory put the putty on the wrong side. It is HET after all
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Old Jun 28, 2012, 03:57 PM
High Dynamic Thrust
stoneenforcer's Avatar
United States, FL, Mt Dora
Joined Feb 2007
2,297 Posts
the rotor should have arrived balanced. half the rotors they send out are poorly balanced. same goes for wemo rotors. using a magnetic balancer is fine and gives the same end results as a dynamic
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Old Jun 28, 2012, 04:34 PM
Aka: Tom Jenkins
ApexAero's Avatar
Palm Beach County, Fl.
Joined Aug 2008
4,444 Posts
The over the counter magnetic balancer is good for 10" props but not for an edf impeller. the friction cones are molded out of whack. Du-Bro is about the best you can get easily and the shaft is ground hardened steel one cone is fixed while the other cone is twist lock and machined, the shaft rides on 2" wheels. Next best thing is a short Helli blade type machined, threaded, balance tool and your own mfg magnet towers. Factory dynamic balancing is done on a balanced low rpm motor and stroboscope(electronic) Efflux RC uses one!
The easiest way to tune an impeller is, mounted with lower voltage to feel for vibrations, loosen the nut, tweak the blade on the adpter shaft a few degrees, tighten down and do again and again until you get it smooth! Then try higher rpms otherwise you just may blow up your fan. Low rpms at the start of tweaking an impeller yields way less scrubbing and impeller tip damage. Ask me how I know!
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Last edited by ApexAero; Jun 28, 2012 at 07:44 PM.
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Old Aug 23, 2012, 06:44 PM
Groundloop World Champion
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USA, AZ, Glendale
Joined Jan 2002
1,178 Posts
Epilogue

Well Guys,

i finally discovered that the motor was the source of the vibrations !!
Yes, I decided to change out Warp4 2-turn for a cheap C2835-3900KV. And, Walla.... very very little vibration and now I have a 400+ watt setup to power my HL/HK SkyRay EDF.

Old_dude
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Old Nov 16, 2012, 04:24 AM
Good vibrations.
dynexhobby's Avatar
Joined Nov 2012
234 Posts
Might want to consider the Vortex. It will perform dynamic balancing.

www.dynexhobby.com

regards

DH
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