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How to balance EDF fans

Old 10-14-2011, 05:03 AM
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solentlife
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Default How to balance EDF fans

I know its been asked before ... but lets bring it up top date with a bit more meat to the examples ...

I've watched youtube vids ... read bits and pieces - but most lack a full description or run through.

I'm particularly interested in DIY solutions such as magnets in vices etc. Rare earth strong magnets are easily bought on ebay etc. - so - lets get to it ...

Fire away ... How do YOU do it ?
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Old 10-14-2011, 05:14 AM
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kyleservicetech
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[QUOTE=solentlife;839049]
I'm particularly interested in DIY solutions such as magnets in vices etc. Rare earth strong magnets are easily bought on ebay etc. - so - lets get to it ...

QUOTE]

For the wattflyer readers that have an interest in buying rare earth magnets, take a look:
http://www.kjmagnetics.com/products.asp?cat=11

Before retiring the company I worked for used a magnet that would lift a 400 pound block of steel. Got a finger in the way once, that finger did not stop bleeding for 8 hours. KJmagnetics sells a magnet that costs over a grand. Hate to ever get injured by that thing!
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Old 10-14-2011, 05:26 AM
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CHELLIE
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I Have to balance a 64mm EDF fan Blade too, I am going to use a Top Flite magnetic Balancer, and sand the back of the blade just a little to make it rough, and use 30 min epoxy on the back of the blade to balance it with, it wont take much, and you can remove the epoxy as needed with in 30 min so get the proper balance, some people use CA glue and hardener, but there is no way to remove the CA if you use to much of it, some people use scotch tape on the back of the edf blade, but i feel that could come off over time, IMHO I think epoxy may be the best to use, as its not going anywhere after it sets up Just my 2 cents worth, Take care and have fun, Chellie

http://www.amazon.com/Top-Flite-Powe.../dp/B0015H1FAG


Last edited by CHELLIE; 10-16-2011 at 10:46 AM.
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Old 10-14-2011, 05:34 AM
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CHELLIE
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Default How to dynamically balance EDF unit with a cell phone

http://www.rcgroups.com/forums/showthread.php?t=1267814
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Old 10-14-2011, 09:01 AM
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solentlife
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[QUOTE=kyleservicetech;839050]
Originally Posted by solentlife View Post
I'm particularly interested in DIY solutions such as magnets in vices etc. Rare earth strong magnets are easily bought on ebay etc. - so - lets get to it ...

QUOTE]

For the wattflyer readers that have an interest in buying rare earth magnets, take a look:
http://www.kjmagnetics.com/products.asp?cat=11

Before retiring the company I worked for used a magnet that would lift a 400 pound block of steel. Got a finger in the way once, that finger did not stop bleeding for 8 hours. KJmagnetics sells a magnet that costs over a grand. Hate to ever get injured by that thing!

I applaud the warning about STRONG magnets .......... but here we are talking about small button magnets in packs used for various hobby items including commercial balancers.

Back to topic ?
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Old 10-14-2011, 05:40 PM
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kyleservicetech
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[QUOTE=solentlife;839062]
Originally Posted by kyleservicetech View Post


I applaud the warning about STRONG magnets .......... but here we are talking about small button magnets in packs used for various hobby items including commercial balancers.

Back to topic ?
Agreed:
(Even small buttom magnets are extremely dangerous if a small child swallows several of them.)
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Old 10-15-2011, 02:07 AM
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[QUOTE=kyleservicetech;839127]
Originally Posted by solentlife View Post

Agreed:
(Even small buttom magnets are extremely dangerous if a small child swallows several of them.)
15 -15 .... didn't know we were in a tennis match ?

Considering the many small objects around homes, model dens, workshops ... aren't they just adding to the other thousands of small objects a child can swallow ?

Match point ?

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Old 10-15-2011, 02:56 AM
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[QUOTE=solentlife;839187]
Originally Posted by kyleservicetech View Post

15 -15 .... didn't know we were in a tennis match ?

Considering the many small objects around homes, model dens, workshops ... aren't they just adding to the other thousands of small objects a child can swallow ?

Agreed:
This is way off topic, but, if it saves a little kid some grief???

Problem with a PAIR of high powered button magnets is they tend to stick together. If they trap something in between them, that little kid is in real trouble, real fast. The usual result is emergency surgery. Something most parents would never even think about happening.
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Old 10-15-2011, 03:18 AM
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Default Sanding or epoxy

On the same sheet of music as Chellie use something like epoxy or sand the back of the blade to even them out. It worked for me. Though the more blades you get the more difficult it is.

On the other subject. The rare earth magnets are very toxic when the material under that nice shiny coating comes off or is chipped or cracked.
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Old 10-15-2011, 03:53 AM
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Originally Posted by cyclingsarge View Post
On the same sheet of music as Chellie use something like epoxy or sand the back of the blade to even them out. It worked for me. Though the more blades you get the more difficult it is.

On the other subject. The rare earth magnets are very toxic when the material under that nice shiny coating comes off or is chipped or cracked.
Epoxy / sanding etc.- ok ...

What about how you determine the balance ? Do you use mechanical shaft balance, magnetic, DIY .... ??

What I'm after is the devices .. ways people have of finding the balance / bias of the fan.

I'm hoping I can use my heli-blade balance shaft with two magnets in a frame ... I thought about the vice method as a Youtube vid shows ... bit undecided on that ... would like a more dedicated apparatus.


Ok ... on the magnet subject .. what size magnet would be needed to carry a shaft and say fans up to 90mm category ? Looking on ebay they vary from 1mm thick and up ... with diameters of 2mm and up... I was thinking of a maybe 5mm thick, 12 or more mm diameter ... ??

Anyone care to measure their magnets and say sizes ? What fan max size do you do with them etc. ?
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Old 10-15-2011, 01:37 PM
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Sorry I can't really add anything constructive here, but I can add that I have this magnetic Top Flight Power Point Precision Balancer and it was useless trying to balance my 64mm edf fans:

http://www.top-flite.com/accys/topq5700.html

I haven't made the leap to a smart phone yet, to try the method Chellie linked, so I'm still waiting for a balance method for the masses.
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Old 10-16-2011, 11:01 AM
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CHELLIE
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I thought this was neet

http://www.rcgroups.com/forums/showthread.php?t=1337162

Cheap prop balancer, can't remember where I bought it from. 20.0 KB Views: 250
Rest between 2 fairly flat surface like wine glasses. 42.2 KB Views: 342
Put tape inside of "cone" on the side that rests up. Repeat until fan will stay still in any rotation angle. 19.2 KB Views: 363
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Old 10-16-2011, 11:12 AM
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a Little more info

http://wattflyer.com/forums/showthread.php?t=59872
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Old 10-17-2011, 12:51 AM
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most smaller fans 70-64-55-50mm fans are simply dynamically ballanced. as some balancer sharts can be too small.

simple rotate the impeller on the shaft untill it is running sooth.

i routinely have more trouble with the spinners(if a seperate peice) than the impeller. really so on a turbax fan.
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Old 10-17-2011, 01:33 AM
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Originally Posted by CHELLIE View Post
I thought this was neet

http://www.rcgroups.com/forums/showthread.php?t=1337162

Cheap prop balancer, can't remember where I bought it from. 20.0 KB Views: 250
Rest between 2 fairly flat surface like wine glasses. 42.2 KB Views: 342
Put tape inside of "cone" on the side that rests up. Repeat until fan will stay still in any rotation angle. 19.2 KB Views: 363
Thats same as my heli-blade balancer ...

The only problem here is that the cones are sometimes not exactly even in drilled / threaded hole. On rotor blades / propellors - this is not so critical but on a fan ... it could be similar amount inbalance to the fans ... according to some online reports.
I reckon to try the shaft without cones ....
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Old 10-17-2011, 01:35 AM
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Originally Posted by tampaflyer View Post
most smaller fans 70-64-55-50mm fans are simply dynamically ballanced. as some balancer sharts can be too small.

simple rotate the impeller on the shaft untill it is running sooth.

i routinely have more trouble with the spinners(if a seperate peice) than the impeller. really so on a turbax fan.
This is something that occurred to me as well ... that on small fans ... the shaft / motor could be greater inbalance than the fan.
Is there any way the whole assembly can be balanced ? Is it worth extracting shaft / rotating part of motor ... with fan fitted and balancing ?
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Old 12-09-2011, 08:05 PM
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Chellie's method works good for extremely small diameter fans with minimum hub diameters.

In the mid 80's we utilized an index wheel (circle). Maybe this is a cross over from automotive experience. Diameter of wheel
is that of the fan's root "inside diameter". From the "center" point of the circle draw three concentric circles. Smalles is size
of the motor shaft or diameter of motor shaft adapter to match fan to shaft. Outside circle is same as the inside diameter of
fan hub. Exactly half way between is a third circle (on larger diameter fans).

Correcting dynamic imbalance is most easily achieved by either removing or adding of material to the blade (set). Typically
blade set is withdrawn or ejected from a mold too early (nick-named pulling green). This can effect pitch and asymetric
continuity blade to blade. With recip use of smaller diameter fans we would raise the rotating mass by adding a slug (aka
fender washer) to the hub. In addition to centering up the molded shape to the slug to mean out hub warp, this provided
substantial material to remove material by drilling small holes until we counter mass balanced the fan.

Card stock circle is a dial index to zero in on heaviest portion of hub circumference so you can logically begin drilling/aka
removing material to balance. Draw lines across the diameter of the circle at right angles to each other. Larger diameter
fan hubs will benefit from dividing into eight segments.

After creating the index guide mount it to the balancer shaft against hub such that it is not going to slip and rotate during
this process. When mounted in balancer lightly blow against the fan blades to initiate rotation. If initial rotation is difficult
don't be surprised. Rotate the fan on the balancer shaft 180 degrees...repeat with blowing moderately on the fan blades to
initiate rotation. When the fan stops rotating, place a small colored dot on the circle close to its outside diameter at the
bottom inside of the hub. Repeat, when fan stops place a second dot with a different color felt marker at the bottom inside
of the hub.

At this point I expect the two dots to be on the same half of the hub face, but apart by about 1/3 diamter of circle half.
You repeat this process twice more without putting any more dots on the circle. Repeated rotations should be within the
same 1/3 of circle diameter...this is a validator as you home in on the sweet spot.

Sweet spot is located within the area 180 degrees out from the heaviest portion of fan. Using cellephane tape, place small
pieces of tape on either blade face or back 180 degrees opposite the heaviest side. Rotation cycle is performed per above
before you add more tape.

Continue until blade stops at no one particular point (aka patience trying work).

Eventually you reach a point of non-destructive balance. Key word here is non-destructive. At this point there is no alteration
of the blade set which provides multiple methods of balancing the fan now that you have identified mass of the imbalance. If
you were good at placing small pieces of cellephane on top of each other so to maintain the smallest footprint of your balance
medium...you see the center of the target zone for adding material of your choice...be it epoxy or CA.

The choice from here on is add or remove material. The two schools are there for you to select from. You know where to add
or 180 degrees from that exact point remove material in order to balance the fan. I prefer a small diameter drill to remove
material equal to mass of cellephane tape. If you add material it should be to the hub's "inside" perimeter 180 degrees out from
the heaviest blade.

Remember you have to rotate fan immediately after adding or removing to the fan...each time you add or remove... :^)

Be patient if you want high performance.
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