PSN-L Email List Message

Subject: Lehman??
From: "Ted Rogers" tedr@..................
Date: Thu, 12 Jul 2001 09:19:42 +1000



Hi

On a recent visit (about 3 months ago) to the UK I spent a part of a day =
in the Science Museum in London. Just before I left I came across a =
working seismograph. It was completely enclosed but with only glass on =
two sides. There was a couple of  interesting things about it, first, =
the  boom/arm was about waist height which meant that instead of a large =
drum the paper passed around a smaller drum of say 23cm (~9") dia by =
45cm (18") long down to a smaller drive roller at floor level, giving a =
paper belt of about 150cm (5'). The inking device appeared to be a =
capillary tube that started horizontally, looped upwards and come down =
vertically to the paper drawing a very fine line. Starting from the =
centre of the paper was another stylus which appeared to be recording =
the time. The whole paper belt would appear to move laterally for half =
the paper with. The other interesting point was the way the mass was =
used, this was hung about half way along the arm, I say hung as it was =
about 30cm (12") below the arm and consisted of a number of disks about =
23cm (9") dia and 2cm (.75") thick. There was also a complicated =
mechanism between the end of the arm and the stylus, time did not allow =
me time to work out what did but it obviously had a use.

The question I ask is: was it a Lehman and if so why hang the mass half =
way along and below the beam? Is it to magnify the amount the weight =
apparently moves??? And how were the oscillations damped, if indeed they =
were.

Any answers - somebody must know...


Ted

      








 
Hi
 
On a recent visit (about 3 months = ago) to the=20 UK I spent a part of a day in the Science Museum in London. Just before I left I came across a working = seismograph. It was=20 completely enclosed but with only glass on two sides. There was a couple = of  interesting things about it, first, the  boom/arm was = about waist=20 height which meant that instead of a large drum the paper passed around = a=20 smaller drum of say 23cm (~9") dia by 45cm (18") long down to a smaller = drive=20 roller at floor level, giving a paper belt of about 150cm (5'). The = inking=20 device appeared to be a capillary tube that started horizontally, looped = upwards=20 and come down vertically to the paper drawing a very fine line. Starting = from=20 the centre of the paper was another stylus which appeared to be = recording the=20 time. The whole paper belt would appear to move laterally for half the = paper=20 with. The other interesting point was the way the mass was used, this = was hung=20 about half way along the arm, I say hung as it was about 30cm (12") = below the=20 arm and consisted of a number of disks about 23cm (9") dia and 2cm = (.75") thick.=20 There was also a complicated mechanism between the end of the arm and = the=20 stylus, time did not allow me time to work out what did but it obviously = had a=20 use.
 
The question I ask is: was = it a Lehman=20 and if so why hang the mass half way along and below the beam? Is = it to=20 magnify the amount the weight apparently moves??? And how were the = oscillations=20 damped, if indeed they were.
 
Any answers - somebody must = know...
 

Ted

      <tedr@..................>
 

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Larry Cochrane <cochrane@..............>