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 HiOn 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
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