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Dynamic Balance

Discussion in 'Pro/Adv Discussion' started by redonk, Feb 13, 2016.

  1. redonk

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    Haven't had any issues with my P3 Adv to date but I purchased a Speedy Prop Balancer since I figured I might need it one day. I tried it out on my current props and was able to easily statically balance them but dynamically balancing them seems to be a lot more tricky.

    I have tried using super glue to add weight to the light side of the hubs but so far it seems I would need to use a really large blob of glue to achieve balance. So far the good amount of glue I have on light side of the hub is not doing much to balance the prop dynamically.

    Any tips or tricks? Is it even worth it to try and dynamically balance props that haven't been giving me any issues? I just don't want to have a huge zit of glue growing out of one side of the hub.
     
  2. msinger

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    I stick small, thin pieces of clear Scotch tape to the bottom of my props.
     
  3. alokbhargava

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    I sand the blades and hubs with fine grit paper.
     
  4. volcom7114

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    Dynamically balancing blades must be done on a very level surface or should be anyway. I use 220 grit sand paper sand the heavy side of the hub only removing/sanding a little before rechecking it or you could be chasing your tail.
     
  5. eaglegoaltender

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    true
    I understand you can carry out a successful "static balance" since this accomplished with a stationary object (prop) resting on a pair of "knife edge" rollers to identify the "heavy side" - this is when the prop's center of gravity is on the axis of rotation.

    In order to accomplish a true "dynamic balance" you would have to balance the props on the quads motors and running so as to balance it while in motion, where a vibration accelerometer is used to identify the amount of unbalance you have in mils (1 mil = .001" or velocity (in/sec) and a photo-tach to give you a once per rev signal & a reference point that is relative to the heavy spot(s)!

    Unless you have some kind of a balance rig that gives you the ability to rotate (spin) the prop at a defined and repeatable rpm you can't carry out a true "dynamic balance". Dynamic balancing will produce a result for correction at single, double or muliti-plane as to correction.

    As to correction for your 'static unbalance" with these small props - you are far better off removing weight from the "heavy side" via sanding as close to the hub as you need to get the proper effect. Try to avoid sanding at the leading or trailing edges of the prop so as not to have a negative effect on aerodynamics when in flight. Double check as you sand in order to not remove too much material - hence that heavy side becomes the light side and you start all over again!

    EDIT: keep in mind a big part of the reason for a prop falling to one side (bottom) is not necessarily the prop itself (blades) but rather an "off centre" hub (eccentric). Yes, you can accomplish the static balance however the hub remains off its center line and has an effect on the motor as to motor vibration. Proper balancing of the props to reduce vibration at the motor will extend the motor and its rotating components life.
     
    #5 eaglegoaltender, Feb 13, 2016
    Last edited: Feb 13, 2016
    SirAchie likes this.
  6. redonk

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    Thanks. Did a combo of glue on the light side of the hub and sanding on the heavy side. That seems to have done the trick.
     
  7. eaglegoaltender

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    Glad to hear you had success. Really for these props a static balance is all that is needed - in reality they change mode/shape ever so slightly when in flight and during specific maneuvers a dynamic balance just wouldn't be very effective on props so small and light. I see guys doing a so called "dynamic balance" by hand spinning the props and letting them come to a rest - that's still a static balance!