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    Re: Sextant averager
    From: Gary LaPook
    Date: 2010 Oct 12, 13:03 -0700

      It took me a while to figure out how this averager works. At first I 
    thought it was as described
    at:
    http://fer3.com/arc/m2.aspx?i=018062&y=200410
    
    
    that it was simply and integrator that multiplied the displacement from 
    the starting altitude
    by the time. But when I took one apart I was surprised to find that the 
    time element was supplied
    by the ball moving across the disk and not by the rotation of the disk 
    which actually supplies the
    altitude component.
    
    I finally figured it out, it is all in the last movement, turning the 
    altitude knob back after the shot.
    I reasoned it out this way which might help in your understanding of 
    this device, refer to figure
    20 in the patent document at:
    
    http://www.fer3.com/arc/imgx/MA-2-Manual.pdf
    
    These examples should help. Starting with the altitude set to 30 degrees 
    you start the averager and then
    immediately change the altitude to 40 degrees where it stays until the 
    end of the averaging
    period, two minutes. Since, at the beginning the ball is located in the 
    center of the disk that
    rotates when you turn the altitude knob, changing the altitude transmits 
    no motion to the drum so
    the drum index dial doesn’t move. So when it comes to the point to 
    rotate the altitude knob to
    move the drum index dial back to zero, no change is required and you 
    read out the average as the
    final altitude, 40 degrees which is obvious since it stayed at this 
    value for the whole period.
    
    Second example. Starting again at 30 degrees you start the averager 
    running. Just before the end
    of the averaging period you rotate the altitude knob to 40 degrees and 
    then the averager stops.
    When the altitude knob was turned the ball had reached the edge of the 
    disk so it moved the
    drum the maximum amount possible and the drum index dial moved the 
    maximum amount also.
    Now, when you rotate the altitude knob to move the drum index dial back 
    to zero, it will move
    exactly the same amount as it moved when the altitude was changed from 
    30 degrees to 40
    degrees so the altitude readout will return to 30 degrees as the average 
    which makes sense since
    it stayed at this value for the entire shooting period.
    
    Third example. Again starting at 30 degrees you start the averager 
    running and at the one minute
    point you change the altitude to 40 degrees where it remains to the end 
    of the shooting period. At
    the one minute point the ball had moved only half way to the edge of the 
    disk so when the
    altitude was changed to 40 degrees the drum index dial only moves half 
    as far as it did in the
    second example. After the shot, when the altitude knob is rotated to 
    move the drum index dial
    back to zero, the ball has reached the edge of the disk so the drum 
    moves twice as fast as it did
    when the knob was rotated to change the altitude from 30 to 40 degrees. 
    So now rotating the
    knob back towards 30 degrees the drum index dial reaches the zero 
    position when the altitude
    readout has only gone back as far as 35 degrees which is the average.
    
    In the more normal case when there are variations in the altitudes 
    during the shooting period the
    operation of moving the drum index dial back to zero moves the altitude 
    readout back to the
    average of all the positions taken by the altitude readout during the 
    two minute period.
    
    gl
    
    
    
    
    
    On 10/10/2010 5:43 PM, Gary LaPook wrote:
    > Here is the patent on the Dreimel-Black averager used in the Kollsman 
    > sextant. The patent used an A-10 sextant to illustrate the invention.
    >
    > Also see:
    >
    > http://www.fer3.com/arc/imgx/MA-2-Manual.pdf
    >
    >
    > The following post describes the operation of the averager but has it 
    > wrong since the ball moves from the center to the edge of the rotating 
    > disk at a constant rate driven by clockwork and the rotating disk is 
    > turned by the altitude knob which is exactly the opposite of this 
    > description.
    >
    >
    > http://fer3.com/arc/m2.aspx?i=018062&y=200410
    >
    >
    >
    > gl
    
    
    
    
    

       
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