Propeller Pitch gauge calibration

[Rcmaster199 at aol.com]

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_ (mailto:pentagon.systems at bigpond.com)  
To: _discussion at nsrca.org_ (mailto: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?





 
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