{"id":5135,"date":"2024-09-03T14:11:44","date_gmt":"2024-09-03T14:11:44","guid":{"rendered":"https:\/\/www.betrisey.ch\/microfoucault-n-26-tatonnements-et-donnees-techniques-part-2"},"modified":"2025-01-28T08:18:05","modified_gmt":"2025-01-28T08:18:05","slug":"microfoucault-n-26-tatonnements-et-donnees-techniques-part-2","status":"publish","type":"page","link":"https:\/\/www.betrisey.ch\/en\/microfoucault-n-26-tatonnements-et-donnees-techniques-part-2","title":{"rendered":"MicroFoucault n\u00b0 26: Trial and error and technical data. (Part 2)"},"content":{"rendered":"\n
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3 September 2024:<\/strong> It has slowed down a little, but is still 20% too fast on the last revolution. (third day)<\/p>\n\n\n\n

4 September:<\/strong> The experiment has become extremely stable over 4 days and will no longer provide me with any new information.<\/p>\n\n\n\n

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So it’s time to modify it with new parameters…<\/p>\n\n\n\n

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Trial 12<\/strong><\/p>\n\n\n\n

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The dips on the Y axis are where the pendulum turns fastest. If I can fill them, the total rotation time will be slower and the pendulum more accurate. Where do they come from, and how can I eliminate them?<\/p>\n\n\n\n

One potential culprit could be an off-centre pendulum.<\/p>\n\n\n\n

Another could be a tiny oscillation of the frame on the Y axis. (The X axis, on the other hand, is held firmly between the two walls.)<\/p>\n\n\n\n

Another could be due to the harmonic vibrations induced by the Charron ring. How can we tell?<\/p>\n\n\n\n

For example: what happens if I gently place a one-gram rifle pellet (5.5mm, calibre .22) on the Y axis of the balance?<\/p>\n\n\n\n

This was done at 7.25am.<\/p>\n\n\n

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The effect of placing the shot at 7.25 am can be seen very clearly in the time data:<\/p>\n\n\n

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But we can see that the pendulum resumed its normal course an hour and a half later, exactly as if nothing had happened. <\/p>\n\n\n\n

5 September:<\/strong> the previous day’s lead experiment can be seen here:<\/p>\n\n\n\n

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You can see that it had no influence on the speed of revolution of the pendulum, which still turned in 26 hours instead of 33. A semi-failure, then. Removing the lead.<\/p>\n\n\n\n

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Trial 13<\/strong><\/p>\n\n\n\n

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9:37: Another ‘hot’ experiment: fitting an external reinforcement to the Y axis, a large block of marble placed at the back of the pendulum. The graphs should show in 4 hours whether the dips are due to torsion of the frame in this axis. Here’s hoping.<\/p>\n\n\n\n

11am, 12pm, 1pm, 2pm, 3pm… failure. Cuisantissime failure. The pendulum has stopped, and is even moving backwards a little. I don’t understand it any more.<\/p>\n\n\n\n

4pm: The susceptible has decided to go back, and in the right direction…<\/p>\n\n\n\n

8 p.m.: All’s well…<\/p>\n\n\n\n

6 September: <\/strong>8 o’clock: the pendulum made its half-revolution during the night.<\/p>\n\n\n\n

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Observation: fitting the external reinforcement has no effect on the pendulum’s speed of revolution. Caramba, missed again.<\/p>\n\n\n\n

Another observation: the pendulum always turns at the right speed EXCEPT WHEN IT’S IN THE Y AXIS: it then turns 40\u00b0 in an hour, which is four times too much.<\/p>\n\n\n\n

If I can eliminate the hole in the Y axis, I’ll have a very accurate Foucault pendulum.<\/p>\n\n\n\n

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Test 14<\/strong><\/p>\n\n\n\n

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8.30 a.m.: I place two small vials of mercury on the pendulum chuck in the hope that the mercury will dampen the parasitic harmonic oscillations. One can dream…<\/p>\n\n\n\n

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8h40… Total failure after just ten minutes!<\/p>\n\n\n\n

9.18am: One of the vials of mercury is placed a little lower down, directly on<\/strong> the balance wheel.<\/p>\n\n\n\n

4.30pm: Failure. The pendulum does not turn at all. The vial of mercury is removed.<\/p>\n\n\n\n

7 p.m.: The pendulum turns. Suspension wire rotates 15′ clockwise.<\/p>\n\n\n\n

7 September 2021:<\/strong> The dip has also moved 15′ clockwise. The problem was simply there: the wire was the cause.<\/p>\n\n\n\n

Test 15<\/strong><\/p>\n\n\n\n

7 September 2021: I<\/strong> made a centring system for the electromagnet, a test pattern graduated in degrees and a revolution test pattern calibrated for my latitude and graduated in hours. Assembling the system, centring the Charron ring and the electromagnet. Very nice.<\/p>\n\n\n\n

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Launched at 6pm and running perfectly. I’m very happy with my brand new rotation indicator:<\/p>\n\n\n

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8 September:<\/strong> Made its half-revolution in 14 hours, still 20% too fast. The time curve is very clean and completely different from that of last week. The speed of revolution is twice as fast between -10\u00b0 and 90\u00b0 where the curve is at its lowest and the amplitude at its highest. So I need to smooth out the whole part of the curve that is below 0.381129 seconds. Understanding and solving this problem will be the programme for the coming weeks.<\/p>\n\n\n

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