Hi Randall,

Any possiblity of a close up of the ball point hinge arrangement?  The
picture can't define
what anchors the pen assembly or in which direction, or what the ball points
contacts.

Either way it "looks" like it might be a little difficult to initially set
up; i.e., the spring would
have to be adjusted just right for it to be reasonably consistently stable.

I suppose you've also tried having the ball points resting atop the cross
rectangular piece
at one time or the other....but I'd guess the pressure is too much there.

Thanks, Meredith Lamb

On Thu, Feb 14, 2008 at 11:56 AM, Randall Peters 
wrote:

> Those of you who like to build things might want to try your hand at a new
> design for the old
> LaCoste spring vertical seismometer.  Internal friction that limits
> performance has with
> previous designs been mainly concentrated in both (i) spring, and (ii)
> axis.  My design can
> radically reduce the hinge force influence, which should improve
> performance. A prototype is
> pictured at  http://physics.mercer.edu/hpage/new-z.html
>     The key to the smaller reaction forces at the hinge (pair of
> ball-point pens) is to add an angled
> boom appendage that allows the zero-length spring itself to be vertical,
> as opposced to the usual
> orientation (inclined)--and to place the inertial masses such that the
> center of mass is close to where the
> spring passes through the split region of the horizontal segment of the
> boom.
>    Although the prototype is shown with an SDC array to sense
> displacement, the instrument can be
> configured to operate with a magnet/coil (Faraday-law) velocity sensor.
>
>    Randall
>
>
Hi Randall,
 
Any possiblity of a close up of the ball point hinge arrangement?  The picture can't define
what anchors the pen assembly or in which direction, or what the ball points contacts.
 
Either way it "looks" like it might be a little difficult to initially set up; i.e., the spring would
have to be adjusted just right for it to be reasonably consistently stable.
 
I suppose you've also tried having the ball points resting atop the cross rectangular piece
at one time or the other....but I'd guess the pressure is too much there.
 
Thanks, Meredith Lamb
  

On Thu, Feb 14, 2008 at 11:56 AM, Randall Peters <PETERS_RD@..........> wrote:

Those of you who like to build things might want to try your hand at a new design for the old
LaCoste spring vertical seismometer.  Internal friction that limits performance has with

previous designs been mainly concentrated in both (i) spring, and (ii) axis.  My design can
radically reduce the hinge force influence, which should improve performance. A prototype is
pictured at  http://physics.mercer.edu/hpage/new-z.html

    The key to the smaller reaction forces at the hinge (pair of ball-point pens) is to add an angled
boom appendage that allows the zero-length spring itself to be vertical, as opposced to the usual
orientation (inclined)--and to place the inertial masses such that the center of mass is close to where the

spring passes through the split region of the horizontal segment of the boom.
   Although the prototype is shown with an SDC array to sense displacement, the instrument can be
configured to operate with a magnet/coil (Faraday-law) velocity sensor.


   Randall