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

John Hubert

The ‘notch’ is really a little file cut - and I don’t think it was always used, but I have seen it on some of my clocks.  It was not very accurate because things varied.  A variety of bob shapes and variations have been used; normal and shell type (at least two versions of shell type), iron/steel, lead, brass, possible other combinations (I have heard suggested brass case, lead fill).  In addition - various other ‘additions’ are occasionally used on the rod; weight trays are common, seconds switch ’trip’ is used on seconds clocks, synchroniser spring assembly is used on a few clocks etc, so it is only a very approximate mark for initial set up.  If you start by putting the rating nut about half way up the available thread, you will soon find you can work from there.  As you get close - you have to take more time, but the initial ‘coarse’ adjustment can be done simply by comparison with a seconds equipped radio controlled clock and typical can be got within a minute a day or so quite easily.  More patience is needed for the fine adjustment!  Very fine ’trimming’ can be achieved by a 4 or 6 BA washer (or two) on the bob top.


On 23 Feb 2021, at 13:36, Chris Wollaston <chris@...> wrote:

Hi, I've just fitted my backstop glass roller but it persisted in remaining in front of the Y-bracket thus not held in place and at risk of falling off and disappearing under the furniture (for a second time) so I've bent the backstop wire hopefully sufficiently to tuck one edge of the roller just behind the bracket. The next task is to get the count-wheel vane just a few thou from the latch as per the picture in Bob Miles' tome, p.238, because at the mo it's some way off.
Also, I read somewhere, either tvtesla or the manual that the pendulum's Invar steel rod is supposed to have a 'notch' showing where the top of the bob should be placed. Mine has no notch, just some oxidation roughly in the right place so can anyone give me a measurement from the top of the trunnion's upper brass block to top of bob please? Tks, Chris in E Sussex

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