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@..................>