close

Privacy guaranteed - Your email is not shared with anyone.

Center of Gravity

Discussion in 'The Okie Corral' started by bocaboca, Apr 30, 2012.

  1. bocaboca

    bocaboca

    Messages:
    914
    Likes Received:
    3
    Joined:
    Jul 25, 2008
    Location:
    Boca Raton Florida
    I was balancing my r/c heli blades using a fulcrum to find the CG. Easy enough.. when the blade is level I'm on the CG. But, that's only going left and right..... isn't the TRUE CG when you find the balance point both left and right and front and back? shouldn't both points be at the same spot regardless of what your trying to balance.
     
  2. droidfire

    droidfire

    Messages:
    4,025
    Likes Received:
    1,627
    Joined:
    Apr 11, 2012
    Location:
    All over, United States.
    In a perfect world, yes. Temperature can change this, uneven expansion, and the shape of the object itself can make it difficult to determine the balance point.

    I've been wanting a tiny entry-level rc heli for a while, it looks like a lot of fun but haven't been able to justify it in light of other things I need at the moment.

    My birthday is coming up, so i'm looking forward to getting one of these to play with then.
     

  3. GarySTL

    GarySTL NRA Life Member

    Messages:
    135
    Likes Received:
    1
    Joined:
    Aug 1, 2005
    Location:
    Warrenton, MO
    Not at all. Wings/blades are an airfoil and are generally thicker about 1/3 of the way back from the leading edge. This moves the fore/aft CG towards the leading edge. Take a broken blade, I'm sure you have some, and cut a piece about 2-3" long. See where the fore/ aft balance point is.


    Outdoor Hub mobile, the outdoor information engine
     
  4. GarySTL

    GarySTL NRA Life Member

    Messages:
    135
    Likes Received:
    1
    Joined:
    Aug 1, 2005
    Location:
    Warrenton, MO
    To make my self clearer, the overall CG is at one place on the blade, but the fore/aft CG is not on the blade centerline.


    Outdoor Hub mobile, the outdoor information engine
     
  5. EMTCOP

    EMTCOP

    Messages:
    317
    Likes Received:
    1
    Joined:
    Jun 30, 2008

    Get an MCPx!!!
     
  6. icantpick

    icantpick Señor Member

    Messages:
    543
    Likes Received:
    32
    Joined:
    Apr 3, 2005
    Location:
    Western Maryland
    The CG is the CG, if it seems to be moving about, it's just an illusion.
     
  7. JimmyN

    JimmyN

    Messages:
    1,266
    Likes Received:
    7
    Joined:
    Sep 29, 2006
    Location:
    Virginia
    It doesn't have to be, it doesn't rotate in that axis. You balance to eliminate vibration so the blades need to be equal weight on each side of the hub, but the hub doesn't spin top to bottom so CG in the top to bottom axis isn't important.

    Glue a lead washer to the top side of the hub. That would definitely move the CG to that side, but does it cause any vibration? Nope. Glue the lead washer to the bottom side of the hub, in fact add two washers and try it. Does it cause any vibration? Nope.

    If it's not rotating in that axis there is no need to balance it.