Can you tell me if the vertical design
had the magnet/coil correctly
oriented because to me it looks
like the magnetic lines of force
are not cutting the coil at right angles
to the motion.

It seems to me that if you used Chris's
style sensor you might get better
results all round.

It nice and simple and only needs
the sensor looked at closer along
with magnetic instead of fluid damping.

I like this vertical design
but I think Id need a two second version
which would be longer in height.

How does one keep the mass from any horizontal motion ?

Possibly three tethers in the horizontal plane
located at the mass 120deg spread apart.

Do such springs stretch with time
and need adjustment ?







----- Original Message ----- 
From: "FRANK COOPER" 
To: 
Sent: Wednesday, March 10, 2010 6:49 AM
Subject: Re: Popular Science Seismograph plans (1965)


Hi Benoit and all,
I constructed that very same seismograph in 1969 and believe that I did detect earthquakes with it. I just didn't recognize the 
earthquake wave forms that we are all so familiar with now. There was no PSN in those days and I was on my own. I believe that it 
could be made into a workable seismograph (sensor) even though made of wood. My 14 year old son, shown in one of the pictures, is 52 
years old now.

See my web page (url below) for pictures.  Click on "MY ANALOG SEISMOGRAPH IN 1969" (JUST BELOW THE PICTURE OF THE 
Shackleford-Gunderson seismograph sensor near the bottom of the page).

SEE MY WEB PAGE AT www.seequake.com

Frank Cooper, Friendswood, Texas, PSN and ATN member.

--- On Wed, 3/10/10, K.-Benoit Evans  wrote:

> From: K.-Benoit Evans 
> Subject: Re: Popular Science Seismograph plans (1965)
> To: psn-l@..............
> Date: Wednesday, March 10, 2010, 6:58 AM
> Does anyone have an
> opinion on the Pop Sci seismograph plans from 1965? Could it
> be modernized and be useful today?
> http://www.popsci.com/archive-viewer?id=WiYDAAAAMBAJ&pg=135&query=earthquake+detector
>
>
> Regards,
> Benoît Evans
>
>
>
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