## PSN-L Email List Message

Subject: Re: Another horizontal boom/mast pivot to consider
From: ChrisAtUpw@.......
Date: Tue, 26 Nov 2002 19:06:06 EST

```In a message dated 24/11/2002, charles.r.patton@........ writes:

> Now for a way out concept - and be prepared to shoot it down!  A possible
> solution for making a self adjusting Lehman or similar pendulum system that
> can ignore slow soil tilt changes.  Imagine floating the entire Lehman on a
> boat-like platform in water.  Two problems jump to attention: 1) the
> damping of the 'boat' in the water is terrible and 2) now how do we
> transmit the ground motion to the seismo?  The simplistic answer is float
> the seismograph in Silly Putty (Dow Corning 3179
> Dilantant Compound).

Hi Charles,

OK, you set up your self levelling floating system. You then put a
Lehman on top with maybe a 2 kilo mass. Along comes a nice large slow seismic
wave and the boom goes to one side. In response, the platform tilts over a
bit in the same direction and so the mass never re-centralises. No thanks.

Regards,

Chris Chapman
In a message dated 24/11/2002, charles.r.patton@........ writes:

Now for a way out concept - and be prepared to shoot it down!  A possible solution for making a self adjusting Lehman or similar pendulum system that can ignore slow soil tilt changes.  Imagine floating the entire Lehman on a boat-like platform in water.  Two problems jump to attention: 1) the damping of the 'boat' in the water is terrible and 2) now how do we transmit the ground motion to the seismo?  The simplistic answer is float the seismograph in Silly Putty (Dow Corning 3179
Dilantant Compound).

Hi Charles,

OK, you set up your self levelling floating system. You then put a Lehman on top with maybe a 2 kilo mass. Along comes a nice large slow seismic wave and the boom goes to one side. In response, the platform tilts over a bit in the same direction and so the mass never re-centralises. No thanks.

Regards,

Chris Chapman
```