Re: Count wheel & backstop roller & Pendulum length to bob?


John Hubert
 

I have just had an (approximate) as they are running measure.

Clock No 1 - Lead bob about 16 lbs I believe - fitted with light early type weight tray.  Approx 90 cm from top of lower brass suspension block to top of bob
Clock No 2 -Steel bob - 16 lbs nominal - fitted with heavier pattern weight tray and seconds trip.  Again approx 90 cm from top of lower brass suspension block to top of bob

Both these clocks are running.

I can’t remember what the thread should be - but 8 BA is too small.  Mine is 4BA (about 3.5mm outside diameter) and the threaded section is approx 65mm with about 12mm unthreaded and reduced diameter unthreaded at the bottom.  These thread into the invar rod which has a female thread.  The bob should be nominally about 16 lbs.  On looking at a ’spare’ rod, there is no notch/mark.  

John

On 23 Feb 2021, at 14:43, Chris Wollaston <chris@...> wrote:

Hi John, Many tks for the info on various bobs and pendulum lengths. My pendulum doesn't have a weights tray and sadly, someone must have dropped the pendulum and snapped off a length of the 8BA? threaded end on which the brass rating nut travels. Thus, I've 41mm of thread sticking out the bottom of the rod but no record of how long it should be when intact?  The cylindrical brass bob weighs 4.4kg approx 9.25lbs and looks authentic so a very rough measurement guide from the top of the brass block above the suspension spring to the top of the bob would be a useful start? I'm suggesting 92cm, what do you reckon? Chris

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