Dear All, Many interesting comments...
David Brown wrote: > ...the place where you add/remove the coins > is below the current C.G. This is a theoretical possibility but all the large pendulum clocks I have looked at have an annular tray round the shaft ABOVE the pendulum bob... There are good reasons for this. A long pendulum (mine is 4m long) swings in a pit which is not a convenient place to scrabble about in. More important is the safety element. Clock makers long ago discovered what devastation can be wrought if the line to a clock weight breaks. Second only to one of these lines breaking is the pendulum snapping off at the swinging point. My pendulum weighs 150kg and I wouldn't like that falling on my fingers. > ...if the clock has not been tampered > with, it is unlikely that the...clock > will have changed its previous LWG of > 0.5 s to 1.5 or even 2.5 s in the > space of a week. While "unlikely", this kind of jump in rate happens several times a year. I have a temperature compensated pendulum but this seems to be defeated if there is a sudden spell of hot sun shining on the face of the clock tower. Fritz wrote: > It seems that you would need to be > able to make two separate adjustments > (and probably more); one would be for > the clock's rate and a separate for > the reading. This is the most astute comment so far. Users of chronometers for navigation, never adjusted either the rate or the reading while at sea. They made corrections based on astronomical observations made in port. My clock is not as good as a chronometer and the rate changes with temperature and humidity [high humidity makes the bob more buoyant and effectively changes the value of g]. I have to change the rate BUT... I never change the reading except when the clocks change by an hour. Fritz suggests: > ... you would rather approach the > correction slowly over 5 weeks ... > .5 .4 .3 .2 .1 This is almost exactly my approach except that my goal each Sunday is to change the rate so that the clock is right next Sunday. This rarely happens. Sometimes I over-correct and sometimes I under-correct. I try to predict temperature and humidity but my predictions are not perfect! The formula I use is: Coins to add = (DG - LWG)/1.3 DG = Desired Gain LWG = Last Week's Gain Coins = U.K. pence This a linear relationship which I established by experiment. The factor 1.3 is a long-term average. Each week I determine what the correct factor should have been last week. In 2016 the value I should have used ranged from -4 to +6 which is disappointing. Roger Bailey wrote: > I expect the impoundment of > water in hydro power reservoirs > adds mass to northern hemisphere. Is this right? Where would the water goif it weren't impounded? Probably into a river which discharges into a northern hemisphere ocean. Most stored water is in the oceans and in ice. The north-south ice balance varies with the time of year but attempts to discern an associated effect on the Earth's rotation show a negligible change. You are probably safe to store water in reservoirs but be very careful about interfereing with the moon! Meantime, Mike Shaw and Dave Bell asked about the effect of tidal energy on the moon. Richard Langley's reply explains all. Frank --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
