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    Re: Leap seconds at Big Ben.
    From: George Huxtable
    Date: 2009 Jan 1, 10:54 -0000

    Lu wrote, about altering the rate of Big Ben-
    
    | What I find puzzling, though, is that a pendulum's rate is controlled by
    | its length and not its weight.  So the only thing I can guess is that
    | the pennies added or subtracted move the center of the pendulum's mass
    | slightly upward or downward.
    
    =================
    
    Lu has got that exactly right. If the tray, that takes the old coppers, was
    at the same level as the weight on the pendulum, then adding extra weight
    would make no difference. It's because it is at a different radius, much
    closer to the pivot point, that adding or subtracting the pennies alters the
    period. I don't know where exactly that tray is placed, but if it is
    attached to the pendulum rod below the pivot point, much closer to it than
    the pendulum's bobweight, then adding weight there would make the clock run
    faster. If it was attached to a short extension of that rod, above the pivot
    point, then adding weight would slow the clock.
    
    George.
    
    contact George Huxtable, at  george{at}hux.me.uk
    or at +44 1865 820222 (from UK, 01865 820222)
    or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
    
    
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