PSN-L Email List Message
Subject: Re: pendulum that generated 'rattle in seattle'
From: tchannel1@............
Date: Sun, 11 Nov 2007 20:05:22 -0700
Geoff, Please where are you located?
Ted
----- Original Message -----
From: "Geoff"
To:
Sent: Sunday, November 11, 2007 4:47 PM
Subject: Re: pendulum that generated 'rattle in seattle'
> Wunderbar, Thanks for the enlightenment;
>
> I still would like to know why voltages
> get higher near pointed objects
> sort of like a point is acting like a
> resistor so possibly you could
> get a good current moving that at the ends
> of a solid tapered piece of copper
> or silver or room temp superconductor
> might possibly generate decent voltages
> without all those loops of fine wire.
> Just a thought relating to antennas
> I used to play with, you can increase the
> impedances by using a gamma match ( smaller
> diameter conductor ) or by tapering their ends
> at the feed point on the driven element ??
>
> Do you know someone who makes and sells
> decent magnet coil sensors possibly according
> to my own wishes. I lack the resources to
> anything decent myself.
>
> I like that vertical seismometer that looks
> similar to a horizontal garden gate type
> but none seem to have a sensor arrangement
> which i like to see ??
>
> I have looked into custom springs but like
> the Century people want $100 + USD
> just to make a single spring ( They call it
> setup costs ) ??
> I guess if people like the spring one get
> somekind of gratuity in return from the company ??
>
> Thanks for your replies.
> I always like hearing from science peoples
> about science stuff.
> Here in SandRock Arizona we seem to be in the Stix.
>
> Regards;
> geoff
>
>
>
>
> ----- Original Message -----
> From: "Randall Peters"
> To:
> Sent: Saturday, November 10, 2007 8:21 AM
> Subject: pendulum that generated 'rattle in seattle'
>
>
>> Geoff,
>> The pendulum responsible for the now-famous picture you and Meredith
>> mention (and give the American Physical Society-hosted sebsite) is not
>> like the dangling pendulum we've been discussing.
>> As you noted, it is a 'toy'-version of the one that I studied
>> (responsible for the aforementioned article on chaos) and which has for
>> years been used to generate beautiful art-pieces.
>> A picture of that pendulum which I built (while still at Texas Tech
>> University) and which is here in the Mercer physics department is to be
>> found at
>> http://physics.mercer.edu/Science_Art/bowling_ball.htm
>> Also on this website are some of the myriad traces that have been
>> produced with the pendulum. Art-folks love these because of their
>> 'life-like' properties--no two exactly the same (quite unlike computer
>> generated patterns).
>> The bowling ball is supported by a pipe on one end, the other end of
>> which is connected to a universal joint (off a toyota pickup if I
>> remember correctly). Because of this U-joint, the x-y axes
>> are coupled, giving rise to a very large number of different patterns
>> during free decay. The moments of inertia in the
>> two axes are adjustable to provide additional control that assists the
>> near infinity of possible results. In the absence of friction, this
>> instrument would display what's called Hamiltonian chaos. The sensitive
>> dependence on initial
>> conditions (essence of the butterfly effect) means that long term
>> prediction (just like the weather) is
>> unpredictable. There are two capacitive sensors that map the motion of
>> the bowling ball, one in each of the perpendicular axes. The output from
>> the amplified signals is fed to an x-y (analog recorder) that with a
>> ball-point
>> pen generates the images on ordinary paper.
>> I have done a lot of chaos research in the last 15 years. The chaotic
>> pendulum that I designed and which is
>> online here at Mercer (when my colleague Matt Marone gets it back
>> operational after our move to the new
>> building) is at
>> http://physics.mercer.edu/PENDULUM/
>> This pendulum can be controlled from anywhere in the world over the
>> internet when operational. The parameter
>> that the user can adjust is the frequency of the drive. The pendulum's
>> motion is monitored by one of my SDC
>> sensors functioning as a velocity detector. An aluminum disk rotates
>> with the pendulum between rare-earth
>> magnets positioned on either side, which are on the end of a bending
>> cantilever. The output (velocity) is integrated
>> with a 'leaky' integrator to give the position.
>> Largely because of my pendulum chaos studies I was asked and wrote an
>> article on " math methods used by physicists to study chaos" for the 10th
>> Ed. of the McGraw Hill Encyclopedia of Science and Technology. I'm sure
>> that some readers will note the prominence of other authors in the chaos
>> section of the encylopedia (such as the creator of the butterfly effect,
>> Ed Lorenz) and then will say, "but who's this guy, Peters?".
>> You ask, Geoff, 'why use multiple turn coils for the Faraday-law
>> sensor. The answer is resident
>> within the statement of his law (generated, in the minds of most, by the
>> greatest experimentalist who ever
>> lived). Faraday's law states that the voltage generated within the wire
>> (historically called the electromotive force (emf) even though voltage is
>> not a force) is proportional to the number of turns of the coil times the
>> time rate of change of the magnetic flux passing through the coil. Thus
>> no matter how your amplifier is built (solid state or vacuum tubes) the
>> signal will be greater the larger number of turns you can wind within the
>> constraints of space limitations borne of wire size and increased
>> resistance that
>> results when the wire gets too small trying to put more turns into a
>> given place.
>> Randall
>>
>>
>>
>>
>
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