Topics

Pendulum adjustment


John Haine
 

Thanks to the help I got for my enquiry about pallet design I'm making reasonable progress on my re-build.  I'm in the process of making a new pendulum, and wanted to tap the collective wisdom on how the rating nut is adjusted.
The synchronome bob is very heavy - mine is ~7 kg - and all that weight is taken on the nut and thread.  It strikes me that there will be a lot of friction so turning the nut can't be that easy.  In fact I suspect that unless some of the weight is taken off it, and also perhaps the rod held to stop it rotating with the nut, it will be nigh on impossible to turn.

So can I have some advice on the approach people take to adjusting the nit position please?  Is it worth considering placing a thrust race between the nut and bob to reduce at least some of the friction?  Of does one hold the rod and turn the bob, the nut turning with the bob?


Richard Marriott
 

Hi John,
Could I suggest getting the length of the pendulum approximately right by supporting the bob weight with your hand and adjusting the nut so it runs slightly slow. Run it for a few days and then fine adjustment can be carried out by adding coins to the top of the bob (if your clock does not have a weight tray higher up the pendulum). I've used weights successfully with both Synchronome and Gent and found it a lot easier and less chance of disturbing the clock.

Best of luck
Richard   

On ‎Saturday‎, ‎26‎ ‎January‎ ‎2019‎ ‎09‎:‎56‎:‎06‎ ‎GMT, John Haine <john.haine@...> wrote:


Thanks to the help I got for my enquiry about pallet design I'm making reasonable progress on my re-build.  I'm in the process of making a new pendulum, and wanted to tap the collective wisdom on how the rating nut is adjusted.
The synchronome bob is very heavy - mine is ~7 kg - and all that weight is taken on the nut and thread.  It strikes me that there will be a lot of friction so turning the nut can't be that easy.  In fact I suspect that unless some of the weight is taken off it, and also perhaps the rod held to stop it rotating with the nut, it will be nigh on impossible to turn.

So can I have some advice on the approach people take to adjusting the nit position please?  Is it worth considering placing a thrust race between the nut and bob to reduce at least some of the friction?  Of does one hold the rod and turn the bob, the nut turning with the bob?


John Haine
 

Yes, I'm fitting a weight tray.


Ian Richardson
 

John,

In the original Synchronome, there is a brass bush fitted into the hole in the bottom of the bob, with a hole for the rating screw to pass through.  Thus the rating nut is bearing on the brass bush, and not directly on the bob.  You are correct that the weight of the bob is born by this thread and rating nut, but it has never been a problem.  As for adjustment, I always find that holing the bob while turning the rating nut works fine.  There is usually about 1 inch of the rating threaded rod protruding below the rating nut, and this acts as a pointer to measure the arc relative to the beat plate mounted below.

Don't rely on the rating tray for coarse adjustment - get it to within a second or two per week with the rating screw and then make fime adjustments with the rating tray.

Best regards,
Ian R


-----Original Message-----
From: John Haine <john.haine@...>
To: synchronome1 <synchronome1@groups.io>
Sent: Sat, 26 Jan 2019 10:56
Subject: [synchronomeelectricclock] Pendulum adjustment

Thanks to the help I got for my enquiry about pallet design I'm making reasonable progress on my re-build.  I'm in the process of making a new pendulum, and wanted to tap the collective wisdom on how the rating nut is adjusted.
The synchronome bob is very heavy - mine is ~7 kg - and all that weight is taken on the nut and thread.  It strikes me that there will be a lot of friction so turning the nut can't be that easy.  In fact I suspect that unless some of the weight is taken off it, and also perhaps the rod held to stop it rotating with the nut, it will be nigh on impossible to turn.

So can I have some advice on the approach people take to adjusting the nit position please?  Is it worth considering placing a thrust race between the nut and bob to reduce at least some of the friction?  Of does one hold the rod and turn the bob, the nut turning with the bob?


Chris
 

Don't panic. A fine thread can provide a huge amount of lift without applying much torque to the rod itself.
Screw jacks lift cars and heavier objects without needing any heavier torque than a lady driver can apply working alone.

Holding the rod firmly with a rubber gloved hand will help to avoid any worry about turning the rod and damaging the suspension spring.
Though history recalls that few suspension springs suffer from such induced breakage. 



On 26/01/2019 10:56, John Haine wrote:
Thanks to the help I got for my enquiry about pallet design I'm making reasonable progress on my re-build.  I'm in the process of making a new pendulum, and wanted to tap the collective wisdom on how the rating nut is adjusted.
The synchronome bob is very heavy - mine is ~7 kg - and all that weight is taken on the nut and thread.  It strikes me that there will be a lot of friction so turning the nut can't be that easy.  In fact I suspect that unless some of the weight is taken off it, and also perhaps the rod held to stop it rotating with the nut, it will be nigh on impossible to turn.

So can I have some advice on the approach people take to adjusting the nit position please?  Is it worth considering placing a thrust race between the nut and bob to reduce at least some of the friction?  Of does one hold the rod and turn the bob, the nut turning with the bob?


John Haine
 

Thanks everyone for the input.  Part of my concern was the very high friction I was getting from the rating nut, made on the pattern of the one shown in Elliott Isaacs' articles in EIM.  This is in the form of a long tube that fits into a larger bore in the lower half of the bob with the "nut" at the top of the tube.  My problem was that the bore in the bob was a shade too small and not entirely concentric with the upper bore (quite hard drilling concentric holes from opposite directions in a large chunk of cast iron!).  I opened the lower bore out a trifle and most of the friction has gone away.