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

[Richard Knoppow via CW]

----- Original Message ----- 
From: "D.J.J. Ring, Jr. via CW" <cw at mailman.qth.net>
To: <sbjohnston at aol.com>; "CW Reflector" 
<cw at mailman.qth.net>
Sent: Sunday, December 21, 2014 10:40 AM
Subject: Re: [CW] Regarding the slowing down of bugs......


Steve,

You're talking about a gravity (or simple) pendulum, not a 
physical (or
compound) pendulum.  With a physical (compound) pendulum the 
period and
frequency depend on the length of gyration, the moment of 
inertia and the
MASS of the PENDULUM.

It's also measured to the center of gravity when calculating 
the pendulum
length, thus lots of weight concentrated on the end of the 
vibrator makes
the key send slower than if the same weights were 
distributed closer to the
origin of the vibrator - and this is what we see when we 
move the weights
towards the operator on a normal Vibroplex key.

*What is the difference between Simple and Compound 
Pendulums?*

• The period and, therefore, the frequency of the simple 
pendulum depends
only on the length of the string and the gravitational 
acceleration. The
period and the frequency of the compound pendulum depend on 
the length of
gyration, the moment of inertia, and the mass of the 
pendulum, as well as
the gravitational acceleration.

• The physical pendulum is the real life scenario of the 
simple pendulum.

73

DR
    For compound pendulum see:
http://farside.ph.utexas.edu/teaching/301/lectures/node141.html

    This is not quite what's in a bug. The compound pendulum 
still relies on the force of gravity as the restoring force. 
The vibrator in a bug would work about as well without 
gravity. The restoring force is the stiffness of the 
mainspring and period, or resonance, is determined by the 
stiffness and effective mass of the bar. In the case of the 
bug vibrator the position and mass of the weight dominate 
the mass and center of mass of the bar. The closest I can 
come to this structure is a clamped bar but of course there 
is some freedom allowed by the main spring which provides 
the stiffness rather than the elasticity of the bar itself.


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