## PSN-L Email List Message

Subject: Re: Crossed wire mass pendulum signal extension/s
From: "meredith lamb" paleoartifact@.........
Date: Fri, 19 Sep 2008 21:24:30 -0600

```Hi Charles,

The X-suspension sounds most interesting; especially the adjustable period
(amazing)!    It "reads" to be ~ similar to the
crossed wire pendulum at this URL below; but different; with the adjustable
mass in between the plates, and, both plates are
"X" suspended.

http://www.phy.mtu.edu/~suits/PH3110/pendulums.html

Take care, Meredith

On Fri, Sep 19, 2008 at 12:43 PM, Charles Patton
wrote:

> Meredith,
> We're (Brett, Chris and I) putting the finishing touches on a white paper
> on pivots with spreadsheet calculations of actual locus points, errors, etc.
> that shortly I'll put up on a web site.  It includes your pivot that I'm
> calling the X-roll.  It's problem is that it doesn't have an easy way of
> obtaining long periods except the use of  force feedback at which point I
> would argue that the lever arm extension probably doesn't add much.

>  I toss out an alternate idea.  The paper will include the equations for
> something I'm calling the X-suspension that comes from work on LIGO.  It's
> essentially two flat plates suspended with crossed wires and a mass attached
> to the lower plate and adjusted in height between the the plates. This can
> be set for any period.  It would have the property you mention, so a lever
> arm attached to the bottom plate and extended away from the bottom would
> magnify the movement.  I haven't done it yet, but it seems to me that
> although for the LIGO work they used flat flexures with traditional clamps,
> the scheme is very amenable to use of rolls and wire or bands for very low
> friction.  I think it could be accomplished with 3 bands minimum, but 4
> equal width bands would make construction easier and very high Q.
>
> Regards,
> Charles Patton
>
>
>
Hi Charles,The X-suspension sounds most interestin=
quot; to be ~ similar to the crossed wire pendulum at this URL below; b=
ut different; with the adjustable mass in between the plates, and, both pla=
tes are

"X" suspended.  http://www.phy.mtu.edu/~sui=
ts/PH3110/pendulums.htmlTake care, Meredith
On Fri, Sep 19, 2008 at 12:43 PM, Charles Patton <charles.r.patton=
@........> wrote:
Meredith,
We're (Brett, Chris and I) putting the finishing touches on a white pap=
er on pivots with spreadsheet calculations of actual locus points, errors, =
etc. that shortly I'll put up on a web site.  It includes your piv=
ot that I'm calling the X-roll.  It's problem is that it doesn=
't have an easy way of obtaining long periods except the use of  f=
orce feedback at which point I would argue that the lever arm extension pro=

=
I toss out an alternate idea.  The paper will include the equat=
ions for something I'm calling the X-suspension that comes from work on=
LIGO.  It's essentially two flat plates suspended with crossed wi=
res and a mass attached to the lower plate and adjusted in height between t=
he the plates. This can be set for any period.  It would have the prop=
erty you mention, so a lever arm attached to the bottom plate and extended =
away from the bottom would magnify the movement.  I haven't done i=
t yet, but it seems to me that although for the LIGO work they used flat fl=
exures with traditional clamps, the scheme is very amenable to use of rolls=
and wire or bands for very low friction.  I think it could be accompl=
ished with 3 bands minimum, but 4 equal width bands would make construction=
easier and very high Q.

Regards,
Charles Patton

```