> This puzzled me since yesterday as I discovered how the suspension of > pendulum clocks is made, that is a springy plate. There is less loss in a suspension like that than there would be in a pivot bearing. The spring doesn't change parameters as it gets dirty or the oil dries out. > -following the above, the lenght of the pendulum varies during a swing, > Ok that we can neglect the above yet having an extremely good approximation, > but is it conceptually right? With a constant length pendulum, there is a slight variation in the frequency with the height (width?) of the swing. (I haven't done the math since college physics which was a long time ago.) It would be interesting to see how much the length of a pendulum changes as the suspension spring bends and how much that changes the resonant frequency and how that compares with the length change due to temperature. I suspect it's down in the noise. -- These are my opinions. I hate spam.