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Old Dec 20, 2001, 09:33 AM
LJH
Moths do not fly inverted
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Greenwich CT.
Joined Sep 2000
4,191 Posts
MF/480 Balancing

I just did a quick search and came up with nothing. Can someone send me a link on this or give me a quick run down on the best way to do it. Should I worry about it useing a SP480 BB race motor. Looks like the F/18 will fly this weekend sans detailing.

Cheers,
Jim
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Old Dec 20, 2001, 10:15 AM
That should fly!
Admiral_Red's Avatar
San Antonio, Texas
Joined Oct 2001
2,406 Posts
You might want to contact Robert at EJF if you need some advice. I think that balancing helps at all power ranges, even 480 input. What I did with mine is balance it with a magnet balancer desgined for props, and sand the back side of the blade that was heavy. It took a while, but it is pretty close. Now from what I read in other posts, the spinner can be another source for the rotor being out of balance.

James
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Old Dec 20, 2001, 10:38 AM
Flying Welder Pilot
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Reno, Nevada
Joined Jan 2001
1,137 Posts
I use a magnetic balancer that has been modified to just balance rotors. I shortened the balance rod and the lower rods so I can balance Mini and Midi rotors. I used to have problems with the long balance rod getting bent and it was a real pain to balance anything accurately. I use pieces of aluminum tape stuck inside the rotor hub to add weight. After you do a few mini fans you will see that they need weight in the same place. Usually were you see the break off of the plastic spru. Balance the rotor by itself. If you like you can also balance the spinner separately. I usually fly all my minifans with out the spinners, and have not noticed an enormous loss of power. If you use the spinner: mount the rotor and spinner in the fan and give it gradual throttle if it vibrates loosen the screw and twist the spinner in 10 degree increments until the vibration is gone. Mark both the spinner and rotor with silver or white paint so you can align them again if you have to remove them.

Gordon
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Old Dec 20, 2001, 10:43 AM
That should fly!
Admiral_Red's Avatar
San Antonio, Texas
Joined Oct 2001
2,406 Posts
Hmm, foil tape....Brilliant!!!

James
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Old Dec 20, 2001, 12:47 PM
Lithium Member
Herb's Avatar
Irvine, Calif USA
Joined Feb 1999
12,158 Posts
I use a $3 balancer (I believe mine is made by Prather) & Neodymium magnets from a failed hard drive, I have used it on all sorts of fans, has worked for me to 42+krpms.

As Chris described some time ago, I use very small vinyl tape pieces on the inside of the rotor & spinner for balance. The centrifugal force will keep the tape in place securely. I first painstakingly balance the rotor, then mount the spinner on the rotor and balance again (the spinner). This avoids ruining your rotor with CA and getting same all over the place including your fingers.

There is no need to fly without the spinner, it results in a small loss in efficiency. Never needed any further adjustment once it was then mounted in the fan. I really never had a need for what some call dynamic balancing either, if the rotor is balanced, it's balanced - and will stay balanced when you put it on the (balanced) motor no matter what the rpm is (within reasonable limits)...

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Last edited by Herb; Nov 06, 2003 at 12:23 PM.
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Old Dec 20, 2001, 05:36 PM
3D Toy Designer
MicroRotors's Avatar
USA, CA, Hesperia
Joined May 2001
4,510 Posts
I myself do it a little differnt.

I balance it on a magnetic balancer like every one has explained but, instead of adding tape and what not, I put thick CA on the back side of the blade and wipe it with my finger to spread it evenly across the whole blade. I do this several times to build up a nice coat. Then I scrape it with a scraper to get it nice and smooth.

I also fill in the mold break off with ca.

I am finding it takes very little effort to do it this way, as you can take off little scrapeings at a time and I can get it dead nutz.

Bill
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Old Nov 05, 2003, 10:23 PM
Strange Planes INC.
spiro's Avatar
Mesa AZ, USA
Joined Jun 2003
132 Posts
Out of round rotor hub holes!

I just picked up my first WMT Mini Fan 480 and I am trying to balance this thing....

The rotor has some poorly cast hole entrances and the cones for my high point balancer don’t really center very well in there. Doing the best job I can do, when I spin the unit on the balancer the entire fan hub rotates out of round by perhaps 10 thousandths. I imagine I can’t even start to balance this thing until I have it sitting on the balancing shaft correctly...

Any ideas?

Has anybody else had poorly cast holes in the rotor hub?

Thanks in advance,
Spiro
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Old Nov 05, 2003, 11:50 PM
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Arthur Knowles's Avatar
Fallbrook, CA
Joined Oct 1998
1,113 Posts
Turn one cone around so the flat is pressing against the back of the backplate/fan. It will center properly then. At least mine do.
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Old Nov 06, 2003, 12:31 AM
smug in granny panties
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NorCal Silicon Valley
Joined Aug 2002
11,778 Posts
I use ABS GLue cause it sticks like it was part of the rotor and it's easily grinded for adjustments. Plus is doesnt leach the natural material out of the ABS like CA does weakening the part.


Barry
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Old Nov 06, 2003, 11:59 AM
Strange Planes INC.
spiro's Avatar
Mesa AZ, USA
Joined Jun 2003
132 Posts
I tried flipping one of the cones around, but the flat face of the fan hub has a rough pit that wont let the fan center up properly. It looks like this pit was left over from the casting process, perhaps where the fan was removed from a part tree. Sanding doesn’t seem to be an option, as the problem is a recess and not a bump. I would have to sand down the entire rest of the face to be level with the lowest pit surface!

As luck would have it, the motor shaft hole in the aluminum drive adapter is the same diameter as the balancing shaft. I just stuck the fan on the end of the shaft and set the balancer up as I would for an overhanging heli rotor head. The fan body still does not seem to be centered that well, though it is a vast improvement. Spinning the fan causes an obvious wobble.

I could balance the fan like this, but it just seems that it should sit on there straight... Has anyone else had similar experiences? Any suggestions?

Thanks again,
Spiro
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