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But doesn't time get slower with increased height? :-)


George Huxtable wrote:
> Bill Morris (engineer@clear.net.nz) wrote, about adding fine-adjustment
> weights to a precise pendulum clock-
>
>
> "The regulating weight is usually half to two thirds of the way up the
> pendulum. It has maximum effect at the half-way point, but it looks better a
> little higher. Adding weights to the top of the pendulum bob does work, but
> they have to be heavier. On the home-made regulator clock whose picture I
> include as an attachment, I use increments of 100 milligrams and can achieve
> a rate of two or three seconds a month, but as the brass-compensated Invar
> pendulum rod is not (yet) correctly compensated, the rate changes with the
> season."
>
> ==========================
>
> It isn't obvious to me whether adding an extra "regulating weight" to the
> top of the bob would speed the clock up or slow it down. There will be two
> effects, which work in opposite directions.
>
> 1. If we can consider the rod as of negligible weight and inertia, compared
> with the bob, then adding that exrea bit at the top will raise the centroid
> of the bob and therefore effectively shorten the length and speed the clock
> up.
> 2. On the other hand, if the rod is not weightless, then adding extra weight
> to the bob, at its centroid, would by increasing the weight of the bob,
> reduce by a small proportion the relative effect of the rod, thus slowing
> the pendulum down.
>
> So in the real situation, with a rod that isn't weightless, and an extra
> adjusting-weight that's above the centre of the bob, which of those effects
> wins?
>
> George.
>
> contact George Huxtable, at  george@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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