[CW] Regarding the slowing down of bugs......

[Richard Knoppow via CW]

----- Original Message ----- 
From: "Steve WD8DAS via CW" <cw at mailman.qth.net>
To: <cw at mailman.qth.net>
Sent: Sunday, December 21, 2014 4:41 PM
Subject: Re: [CW] Regarding the slowing down of bugs......




Thanks for the insights regarding bugs and pendulums and 
vibrating arms.  I was imagining that the forces of the arm 
and contact springs were taking the place of gravity in this 
horizontal situation, but that the idea of the pendulum 
still applied.  The bug I modified as a kid had a scale 
stamped into the bar showing the speed for various positions 
of the weight, and it was marked slower the farther the 
weight as positioned out from the pivot, thus my assumption 
that it was indeed like a pendulum and it wanted a longer 
level arm to go slower.  And when I extended the arm it 
indeed went slower.

Adding weight did slow it, but a lot of weight was required 
to only reduce speed a little bit, thus my conclusion that 
the dominant factor was length rather than mass.  I also 
noted a lengthening of the dits with added weight, which was 
reinforced in my mind when I saw the idea of "weight" 
adjustments on electronic keyers.  Apparently I built a 
whole system of fake-physics in my head to explain my 
observations.

Thank you.




Steve WD8DAS

    The relationship is a lot like the electronic resonance 
formula, remember the square root of the combination of L 
and C. In the mechanical case mass is equivalent to 
inductance and spring stiffness to capacitance (actually, 
there is a reciprocal system but the square root is still 
there).  So, you must increase the mass by four to reduce 
the frequency to half. Thats also mostly why the two weights 
on a "original" bug don't result in half speed when they are 
both in place although the position is also contributes.
    I searched around trying to find a site with all this in 
fairly elementary form but couldn't. Someone else may have 
better luck.  I studied this stuff so long ago that I have 
to refresh myself to make sure I am not blundering around.
    One system of mechanical and acoustical analogies to 
electrical circuits was constructed by Harry F. Olson, long 
time head of RCA's acoustical labs. He wrote a book about it 
called "Dynamical Analogies" which can be found at:
http://www.tubebooks.org/technical_books_online.htm
    A more sophisticated system was devised by Frederick V. 
Hunt, of Harvard, which he described in one of his books but 
I am drawing a blank on the title. It was reprinted by the 
Acoustical Society of America and probably an Amazon search 
would find it.  I really need to straighten out my books too 
many of which are in storage.


--
Richard Knoppow
Los Angeles
WB6KBL
dickburk at ix.netcom.com