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The Ultimate P3 Prop Balancer

Discussion in 'General Discussion' started by GreggC, Jan 6, 2016.

  1. GreggC

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    Hey guys,
    I built The Ultimate P3 Prop Balancer !!
    [​IMG]

    I never liked the available prop balancers because there were too many variables.
    The DuBro has 8 points of contact, way too much friction for my liking,
    The Speedy Prop Balancer (see below) has to be perfectly level and it has two points of contact / friction.
    I just don't like it.
    [​IMG]

    So I decided to build The Ultimate Prop Balancer,
    Here's how it's done;
    #1...you'll need a M6 x 1.0 RH thread bolt,
    #2...I search the world over and could not find a M6 x 1.0 LH thread bolt so I purchased a M6 x 1.0 LH thread all thread rod,
    #3...you'll need a Top Flight prop balancer,
    [​IMG]

    Cut the head off the bolt and cut an equal length peice of all thread,
    These are the balance shafts.
    [​IMG]

    Grind the sharpest point you possibly can onto the opposite end of each balance shaft.
    [​IMG]

    Mount one of the balance shafts onto the Top Flight Balancer,
    The Top Flight Balancer has two metal rods that join the two upright pieces where the magnets are,
    Measure the air gap, mine was 1.25",
    Cut the metal rods .25" less than the air gap, I cut 1" off mine.
    [​IMG]

    Assemble the Top Flight Balancer,
    Screw a prop onto one of the balancing shafts,
    Mount this assembly into the TopFlight Balancer,
    !! NOTE THE AIR GAP !!
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]

    So, what you now have is The Ultimate Prop Balancer, there is only one single pin point of contact and it is a tiny needle point, it has the absolute least amount of friction possible.
    One more thing, I used a torch and heated each one of the needle points till red hot, then I quenched them, this hardened that point, I then groomed each point till sharp....presto magic a hardened pin point with extremely low friction !!

    This prop was perfectly balanced with the Speedy Prop Balancer, now look at it, one blade dropped to the bottom, no way was this prop balanced.
    [​IMG]
     
    #1 GreggC, Jan 6, 2016
    Last edited: Mar 21, 2016
    Ron Davis and Mark The Droner like this.
  2. Mark The Droner

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    Pretty brilliant. Well done, sir.
     
  3. snerd

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    I've never gotten into the prop balancing yet. But from what little I've read, isn't there a vertical "and" a horizontal balance point?
     
  4. GreggC

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    I've always strived to balance horizontal because that tells me each side is the same weight.....meaning balanced.
    Maybe someone else will chime in.
     
  5. Mark The Droner

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    My understanding is it's the same concept as balancing a lawn mower blade although with more precision. I've never heard of verticle vs horizontal balancing. My understanding is you want each propeller end (or side) to weigh exactly the same as the other end to minimize / eliminate vibration as it spins - just like a lawn mower blade. On mower blades, you grind steel off the heavy side. Re props, many people instead add a small piece of tape onto the light side to counter the extra weight on the heavy side.
     
    #5 Mark The Droner, Jan 6, 2016
    Last edited: Jan 6, 2016
  6. GreggC

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    My background is in aviation,
    When we remove blades from a turbine engine we balance all blades to the exact same weight.
    When we remove blades from a two bladed prop we balance the hub then balance each blade to the exact same weight.
    As sensitive as this balancer is I'm comfortable with a horizontal balance, this tells me each side is of equal weight...this is what I want.
     
    BigAl07 likes this.
  7. Triakis

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    Any CMM operators / inspectors here? A ruby tipped stylus would give precision with low friction if you choose the ideal size...

    [​IMG]

    Another method could be having a motor with shaft just like the bird does and it would spin up and measure the vibration, shoot a laser at the points that need to be modified, map it in 3D so you can trim it later. Just like balancing a tire/wheel on the car. OK, that is getting ridiculous for the hobbyist perhaps but it would be interesting! ;)
     
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  8. discv

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    Some interesting ideas going on here. But- the assumption is taken that the DJI motors, shaft threads in particular, are perfectly machined.:(
     
  9. GreggC

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    I like the ruby tipped balancer shaft idea, I was thinking about teflon, anything with a coefficient of friction that is less than the hardened metal pin point that I have built would be interesting to test.
    Yeah,
    Laser 3D balancing is a bit much :)
     
  10. BigAl07

    BigAl07 Moderator
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    Now we understand why you wanted such a precision prop balancer. It all makes perfect sense now :)
     
  11. GreggC

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    Yeah,
    Im a bit of a perfectionist...or just nuts, you guys decide.
    If was a fun project and now all 20 of the props I own are spot on balanced :)
     
    Innrkid likes this.
  12. Triakis

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    That's a good point! The best dynamic, on hub balance would be achieved on the bird itself. An array of sensors attached the airframe while the motors are operated from idle to WOT (obviously the airframe have to be movement restricted!) and one could not only balance based on per shaft but interface interference using, for example, zero beat cancellation. The vibration could be reduced to nil. Of course change in temperature and a prop touching anything more than a finger flick and the process would have to be repeated. This would drive one nuts. Or maybe not. ;)

    PTFE is good for low friction but it's too soft and subject to plasticization deformation. Of course we're talking a precision level that's nearly in the ludicrous OCD range here. :)
     
    #12 Triakis, Jan 7, 2016
    Last edited: Jan 7, 2016
  13. BigAl07

    BigAl07 Moderator
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    I worked for a company (as a CNC mill/lathe programmer) where we made parts for GE and P&E jet engines so I can appreciate the perfectionist. I wish I still worked there because I had access to some phenomenal metals and compounds that just aren't available outside of the Aerospace industry.
     
  14. Skywalker

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    Just how much precision does a prop on a toy need? There comes a point of diminishing returns.
     
  15. GreggC

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    I am happy with the amount of precision I have obtained for my $1250 toy :)
     
  16. Trashpicker

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    WOW!
    Guys,I was over at Gregg's house the other day for some flight training and pizza and he was showing me all the parts and explaining how it will work. As a Mechanical Engineer I understood and thought it was a great idea. I am amazed that he got it all together in such a short time. Great job on the balancer and since you have all yours done how about if I bring all 15 1/2 of mine over so you can balance them????:)
     
  17. GreggC

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    Come on over buddy, Ill buy lunch !!
     
  18. Trashpicker

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    I really want to return to fly again, since we are still knee deep in snow here. It was 85 miles round trip! It will be my turn for lunch. Weather permitting tomorrow i might try the POI over the antique tractor surrounded by undisturbed snow. That should look pretty cool. By the way, the balancer looks great!
     
  19. nekit

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    Saw your idea with the Top Flight balancer and remember I have one of those for my RC Airplane days. Couldn't find a M6 X 1.0 LH bolt either and was kind of worried a bolt might be off centric. Instead I machined a hub that slips into the prop on the smooth bore outside the threads. See the pictures. Seems to work good. FYI out of all 8 of the stock P3 blades only 1 of them seemed to be out of balance enough to mess with. I stuck a 1/4" x 1/4" piece of "Scotch" tape on the other side and it balanced out. Not very far out of balance. I just sanded a bit on the heavy side and it was good. Some aftermarket ones might be worse.
     
  20. nekit

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