I'm new to the hobby and still building my first trainer. I would really appreciate any comments regarding methods of balancing propellers. From what I'm reading, it appears that balance can be achieved by addition or subtraction of weight. Do you have to buy fixture to balance a prop? How and where do you take weight off a prop? How do you add weight? Any other tips or comments?
Harlan
As a newbie prop balancing will be the least of your worries, especially as you'll liable to break it sooner rather than later. However, most modern props will only require a little removal or addition of weight. I've known colleagues just add paint to a tip or sand the edge just to remove or add weight.
For all information on propellers, refer to sub section "Propellers" at Alan's Hobby, Model & RC Web Links
Preferred method of balancing is to use fine sand paper and smooth all, if any, molding flash (sharp edges) from around the edge of prop. Lightly sand the back of the light tip, add a little bit of epoxy and sand that epoxy back until prop balances. much like balancing your car tires. The prop if in effect a wing lifting the plane forwards, do not sand the front of the propeller. regards Alan T. Alan's Hobby, Model & RC Web Links
I should have known that Alan's pages would provide information regarding this subject.
Harlan
Thats all you need. When you can get the prop to rest horizontal t the bench w/o one blade dropping, its balanced.
Bingo! ;) Two blades are easy, try four, or a six blade EDF impellor. :
-- Ralph Breka
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Not really, if you then rotate the prop 180 degrees and if it will g back to its original position, then still heavier on side.
When the prop is able to sit still in ANY position, then it is mas balanced properly.
OTOH, Does it really make a difference ? Probably not much unless i is way to heavy one one side. One thing you can do is balnce it lik suggested, then rotate 180 and check how fast it rotates back. I fast, too heavy on one side. If rather slow, then probably OK
-- indoruwe
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Oh, I'm always half-cooked.... :rolleyes: I think you're right though
it never hurts to check both sides. Too bad the guys atteh tire sho arent so thorough. ;
-- Ralph Breka
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They can only be as thourough as their machine is set up to be. Thos
machines do need to be calibrated once and a while and who knows whe the last time it was done ?? When you really want to be thorough, the you have to check everything that rotates !!
They (I did, when I worked part time when in college a very long tim ago) used to do it "on the car", with this gadget that spun the tire like mad (those that were not engine driven), and then you had to twea these three knobs in the middle of the attachment that was clamped o the wheel. Only told you how much and where on the diameter, but neve on which side of the wheel (inside or outside)
-- indoruwe
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Alan has given you fair instructions with one major item glossed over. REMOVE ALL EVIDENCE OF THE FLASHING down to the blade itself! That means remove the ridge that the flashing comes from to help reduce the cutting edge most non wood props have. This will not prevent injury, just reduce it when you get you digits entangled trying to tach the running engine. Oh, by the way do not do that, it hurts - a lot. Learn to tune the engine from behind the fan, it does not hurt as much.
Wild. :eek: Well, I use the primative dowel method and in the field
spin it on a screw driver. It's good enough; albeit NOT perfect
-- Ralph Breka
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AT that's the worst advice ever given regarding prop balancing.
For the rest of you, the prop should remain stationary in any position. To achieve this using a Dubro or TF balancer:
Now how does one remove or add material? In the horizontal, you can take a little off the tip or the back face or you can add material using epoxy, nail polish, or tape.
In the vertical, you can file down the hub or add material. If there are slots in the back face, you can pour in nail polish or epoxy. Some people lose material by drilling holes!
Whatever you do, don't fly with an unbalanced prop. The vibration can loosen every nut and glue joint and take a toll on the radio gear. Finally prop balancing is a real art, and it takes time to learn how to do it right.
Ciao,
Mr Akimoto
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