Propeller Pitch gauge calibration

[Rcmaster199 at aol.com]

Nat, so if someone were to reverse engineer the famous APC prop blade pitch  
distribution, one could start by making a bunch of cardboard right triangles 
fit  under the blade, at, say, 1" intervals, moving out from center. Then one 
can  determine what the pitch at each station is by simple graphical means from 
the  triangles, and plot that against radius (stations). I would hazzard to 
guess a  parabollic distribution.
 
Of course, if one isn't so inclined, he can always call Tony and buy the  
sucker, but what has he learned?? LOL. Tongue planted firmly in cheek.
 
MattK, pontificating again, but what the hell. BTW isn't that what the  
rubber band wielding free flighters do with the props they build from  sticks?
 
 
 
Matt, you are correct. Feel free to help clarify my  comments.                
    Nat


----- Original Message ----- 
From:  _Rcmaster199 at aol.com_ (mailto:Rcmaster199 at aol.com)  
To: _discussion at nsrca.org_ (mailto: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_ (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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