Propeller Pitch gauge calibration

[Nat Penton]

Matt, you are correct. Feel free to help clarify my comments.                   Nat
  ----- Original Message ----- 
  From: Rcmaster199 at aol.com 
  To: discussion at nsrca.org 
  Sent: Saturday, October 16, 2004 12:02 AM
  Subject: Re: Propeller Pitch gauge calibration


  Nat, taking a hypothetical example of a 20x10 prop, the radius is 10 inches and coincidentally so is the pitch at the 70% station of the prop. 
  The 70% point is 7" from center. 
  The circumference of the circle at that station is 2x(7")x Pi. 
  The right triangle would then have a base of 2R x Pi and a height of 10"(prop pitch). 
  The hypotenuse inscribes angle which is the true pitch angle at the 70% station. 
  (Reducing the triangle down to say 5% of the original makes it manageable.)
  Is this what you mean?


  Matt


    Peter,
    Prop pitch is measured at the 70% station.Pitch distribution along the span ( deviation from true pitch ) is proprietary and is, in the case of APC, what accounts for their excellent performance and low noise.

    A way to calibrate your gauge is to make a template , a triangle with the x axis equal to the circumference  at a given blade station and a slope of ,say, 10 inches and check this against the guage reading at that station.

    i.e. at each station a prop will "twist" forward the same amount in one revolution if it has true pitch ( no slippage ).

    You do not need to express inches of pitch as degrees.
    When are you going to give me a report on the Alliance trim !!
      ----- Original Message ----- 
      From: Peter Pennisi 
      To: discussion at nsrca.org 
      Sent: Friday, October 15, 2004 5:18 PM
      Subject: Propeller Pitch gauge calibration


       

       

       

      Hi Guys,

       

      I have modified a propeller pitch gauge to accommodate larger propellers. The gauge I have is a very old prop shop model.

       

      I have decided to check my APC props because I was getting mixed performance results between all my prop sizes.

       

      Anyway I thought I would check my gauge with a new prop to see how accurate it was and the numbers I got were different to what was on the prop. I tried another new prop of exactly the same size I got a different result again. Anyway I am shocked to find that what is displayed on the prop is different to my measurements.

       

      What part of the prop should I be measuring my pitch as this varies slightly over the length of the blade?

       

      Secondly, how would I go about calibrating my unit because I can’t do it with new props because there all different.

       

      How do I express for example 13 inches of pitch as degrees?

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.f3a.us/pipermail/nsrca-discussion/attachments/20041016/6063c5aa/attachment.html