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Proper Mounting of Reamed Graupner Props on Phantom?

Discussion in 'General Discussion' started by sn3ak3rp1mp, May 5, 2013.

  1. sn3ak3rp1mp

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    Hey All,

    Reamed / bored out my Graupner props to ~ 8mm today and just need to balance them before mounting on the Phantom. The only thing that has me scared is the lack of the motor shaft "key" which would prevent the prop from spinning freely on the shaft.

    How are all of you Graupner owners tightening down the props? From searching, I gather you just use loctite on the shaft threads and I've come across people using washers underneath (?) the prop ... anyone find the need to use lock-washers on the top of the prop (i.e. between the prop and the nut)? Are you replacing the nut? I plan on just using the aluminum dome / castle nuts which came with the Phantom.

    Thanks!
    Paul
     
  2. Gizmo3000

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    Location:
    Sherman Oaks, CA
    I've yet to mount my graupners (still trashing my plastic props gaining experience)

    but I bought some Fiber washers to use under the Graupners
    like these
    http://wedo.hillmangroup.com/item/rubbe ... ers/3819-k

    I've heard some people are still using their DJI prop nuts with them.
     
  3. tanasit

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    Graupner quality control is not perfect! Some of mine have the hub thickness less than the others.
    How do I know? Once reamed (note that the Phantom motor shaft on the bottom part is NOT 8 mm but 7.9 mm, so if you ream the hub with 8 mm reamer the hole will be somewhat sloppy!) with my modified reamer ( I used the Dremel with cutting disc filing off the teeth of the 8 mm section but only did that on half of the first part that goes into the hole) and installed with stock nut, some props can still be turned.
    Why? because the hob is NOT thick enough, so even when the nut is fully down, the skirt of the nut hit the shoulder of the shaft's bottom!
    What the fix then?
    The easiest is to use the washer (which is not easy to find so people use standard 5/16") underneath the prop. In effect the washer will raise the hub slightly so that when the nut is tighten down, the prop will be locked in.


    There are 2 more fixs:

    1. Bore the bottom of the nut with 9 mm brill bit to about 1 mm deep, this will allow the nut to pass through the shoulder of the shaft so that the skirt of the nut can go lower to do the job.

    [​IMG]

    2. Use the Dremel to file down the shoulder of the shaft's bottom. Do that carefully by removing the prop and keep the motor spinning while carefully tap it with the Dremel cutting disc. You only need 1 mm down and with this mod any thin prop will need no washers ;) See picture of before and after below:

    [​IMG]

    I modified my Graupner props to have the "key" simply by brushing 2 thin layers of CA and file flat!
    [​IMG]
     
  4. Gizmo3000

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    Location:
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    great idea on the CA to create a keyhole!!
    I'll have to try that!
     
  5. sn3ak3rp1mp

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    Thank you for the detailed reply tanasit! I picked up some fiber washers today from Home Depot and some blue loctite. I'll report back. Guess I'm just going to take the try it and see approach, and not fly over water until I'm comfortable the Graupners won't spin on the shaft while in flight.

    Cheers,
    Paul
     
  6. Gizmo3000

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    Location:
    Sherman Oaks, CA
    Be very careful with the loctite and be sure to keep it far, far away from plastic! (not sure how it reacts with CF).
    But always be sure your nuts are tight after every flying session
     
  7. tanasit

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    In stead of liquid Loctite, try the tape one:

    [​IMG]

    [​IMG]

    I cut it lengthwise in half about 1 " long and wrap "clockwise" onto the thread part.
    No drip, no leak!