Clock adjuster rod for measuring spring and fusee drive power

 I was presented with a clock that seemed to be low on drive power and it was proving difficult to diagnose where the fault lay. I remembered seeing articles by both William Smith and John Wilding about a device that could give a relative measure of the drive power from the fusee.  There is also a brief mention of this in Donald de Carle’s – Practical Clock Repairing.

This will be difficult to describe but in essence it is an adjustable balancing rod that is mounted on the fusee winding square.  The movement’s centre wheel and second wheel are left in place but the escapement is removed.   The rod has a sliding weight that can be adjusted to counter the drive power from the spring through the fusee chain to the fusee itself.    By winding the fusee one step at a time and resetting and noting the counter weight position it is possible to derive a graph of fusee turns against drive power.  Here is a pictorial view of the device and below that a picture of my version.

A sketch of the principle of the balance rod for fusee drive checking
A sketch of the principle of the balance rod for fusee drive checking
Image of my version of the balance rod
My version of the balance rod. The winding socket is interchangeable for different fusee square sizes.

William Smith suggested making the mass of the sliding weight equal to 1lb and measuring the weight position in inches from the balance centre to the centre of the weight.   This results in a graph of drive in lbs/inches.

In practice the balance point is a little subjective to set.   You need to move the weight back and forth such that the rod remains horizontally balanced against the drive from the fusee square.  Once a balance point is achieved the distance from the moveable weight centre to the winding axis centre is recorded.

On this particular clock I plotted the results of the each turn of the full wind range of the fusee and the balance distance seemed to be reasonably repeatable and overall fairly flat. This suggested that perhaps there was not an individual fusee positional problem but something that was common mode across the range of the winding.   To me this indicated that the drive transfer through the centre wheel and the second wheel was potentially the issue.

Checking the arbors against the plate pivots did not reveal a great deal of wear but on dismantling and checking more closely one of the centre wheel pivots had a worn curved profile.   I re-made the pivot and re-bushed the plate and reassembled the movement. On re-running the test with the rod I found I had gained an extra 1″ movement of the balance weight along the rod.  This suggested that more power was now being transmitted to the train, that is the train was not presenting such a high resistance to motion and more power was being created to drive the clock.  

This appeared to solve the problem with the clock having a much stronger beat.   This result is indicative of the value of this simple tool.

William Smith also suggests that the balance rod is useful as a temporary drive source.  Suppose you have a clock stripped down and want to quickly check the train.  Without fitting the barrel and fusee chain, the balance rod and balance weight can be mounted on the fusee square to provide quite a few minutes of drive to quickly exercise the train without having to undertake a full movement rebuild.

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Update notes on modifications to the Devon Sea Clock

Finally Documented my Devon Sea Clock modifications

Following on from a number of enquiries I have updated my notes on the modifications I made to my Devon Sea Clock.   This includes creation of a new set of pallets and also set up notes.  A link is provided to download the details.

devon sea clock notes on modifications
My Devon Sea Clock as featured in these notes

I hope you find this useful and it allows a few more clocks to begin ticking reliably. 

The link will download a ZIP file with the written notes and 2D drawings of the components.

Sea Clock Notes May 2021

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A church clock problem and lockdown timekeeping

Keeping the village clock going

From previous posts you will be aware that I am regarded as ‘Tech Support’ for the local church clock.   The clock is a Cooke of York design dated from 1869. It has been running very well over the past months until a few days ago when ….twang … one strand of the strike wire rope gave way and twirled back up the rope and got wedged in the strike mechanism.   The going train continued to keep time and display on the dials but no bell strikes.  An eerie silence fell over the village. 

Strike chain drum showing the errant strand in the barrel wheel
Strike chain drum showing the errant strand in the barrel wheel and also the soft eye fastening onto the strike barrel.  The going train barrel can be seen in the background.

The errant stand of wire was easily cleared but on further inspection the strike weight rope looked to be in a dangerous condition.  I resolved to replace the rope and while doing this I would also replace the cable on the going train. 

The strike chain had jammed with the weight almost at the top so this needed to be gently let down to floor level.

Strike train weight stopped almost at full wind
Strike train weight stopped almost at full wind and needed to be lowered before any work could start on replacing the cable.

New fibre cored 6 x 19 galvanised wire rope was ordered.  The strike train had 6mm diameter and the going train 5mm and both needed around 30m of cable.   The chosen supplier was RAMS Lifting Gear in London and they agreed to put a 20mm diameter soft loop at one end of each cable.   This would loop over a button on each of the two barrels to anchor the cable.   RAMS delivered the cables very quickly.

Given the social distancing restrictions in place, my normal assistants were not available to help.  Instead I persuaded my wife to climb the bell tower with me to assist with the cable changes.   It is a bit intimidating to ascend up the two ladders for the first time but she overcame her nerves and after a few up and downs became quite at home with the surroundings. 

The new cables were unreeled and laid out down the stairs from the tower into the church so they could take their own path and not twist. We had decided to use the existing cables to pull through the new ones.   This meant the soft loops and the associated crimps had to be pulled through each pulley.  This was tight on a couple of them but we managed.   

With the cables pulled through and into the clock cabinet we then pulled off the old cable from the drums and ran on the new ones.  Inspecting the old cables revealed that they were not in the best condition and could have been an accident waiting to happen had they snapped clean through.   There is no clock record to indicate when they were last changed.

The clock was soon up and running with its new shiny cables and normality was restored in the village and surrounds.

We received a number of appreciative comments from the villagers for getting the clock up and running again so quickly.  Considering these comments suggested that perhaps the chimes of the clock had taken on a new meaning in COVID lockdown.   Time precision had recalibrated.   Watches and clocks in and around the home had ceased to be the reference in the slow world of lockdown.  Nowhere to go or to be, meant watches lay on bedside tables unworn and unwanted.  Instead people had moved from watching minutes to referencing life by hours.   The village clock now subconsciously marked the passage of time with its hourly chimes.   Everything in between had become a slowed down lifestyle.   When to come or go into the garden or to the shops, when to think about a meal – all now seemed more likely to be triggered by the hourly chimes of the village clock.

Which is probably how life was in 1869 when the clock first broadcast its notes over the village.   

Did we perhaps lose something somewhere along the way ?

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Repairs to an ancient Thwaites clock completed

I have mentioned my activity on the Thwaites clock in a couple of blog posts and I can now confirm the work is complete.

Thwaites clock as originally received prior to the work taking place
The Thwaites clock as received before work commenced

This has been an interesting challenge and I am pleased with how it has worked out.  Once again I am impressed by the way that modern techniques and technology can all play their part in achieving a result that once upon a time would have been impossible using traditional circumscribed knowledge.

There is a full write up here on the Thwaites Clock Activity for anyone interested.

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Further 3D printed soft jaws for the Thwaites clock escape wheel

More use of 3D printed Soft Jaws

A few posts ago I talked about using 3D printed soft jaws for work holding in CNC operations.   This method does not replace conventional aluminium soft jaws where high accuracy machining operations are to take place.  Instead it is intended to allow second side ‘decking’ of what would have been excess stock on the material blank that had been used for work holding.

I am currently creating missing components for a Thwaites turret clock.  I had finished the pallets and I now moved onto the new escape wheel.   The design was created in Fusion 360 and integrated the pallets and the escape wheel together so the critical geometry was compatible.

The brass blank for the escape wheel was a 1/4″ brass block which I managed to hold tightly in the machine vice with a 1mm thickness of gripping stock.  (I don’t have Tallon grips or similar so I have to be generous).  I machined the wheel and was left with this 1mm to skim off the reverse side of the wheel.

I did not want the teeth on the new wheel to get damaged when gripped in the vice so the 3D printed soft jaw concept appealed.   The PLA would provide grip.   The teeth on the wheel could bite into the PLA without suffering any damage.

I had already created a single blank soft jaw In Fusion 360 for the previous pallet holding job.   This like it would be fine to accommodate the wheel dimensions.   I simply had to import two of these into the new soft jaw design (not forgetting to ‘Break the Link’ so the jaw models could be edited). I projected the wheel onto the soft jaw’s face and added a 0.2mm positive offset border.   I almost made the mistake of forgetting to invert the wheel as the soft jaw image must be a mirror of the Fusion top side view of the design to be gripped.

Fusion 360 view of the Thwaites wheel projected onto the PLA 3D printed soft jaws
Fusion 360 view of the Thwaites wheel projected onto the PLA 3D printed soft jaws.

The finished brass wheel did not accurately reflect the geometry of the Fusion design.  This is because the resolution of the tight corner CNC operations were limited to tool sizes.   I added fillets to all the ‘sharp’ edges in the soft jaw image to accommodate this.   I also had to do some tweaking of the inter jaw spacing 3D joint to reflect the wheel diameter and the amount of grip I judged might be needed.

Close up view of the fillet modifications to the sharp corners of the wheel outline
Close up view of the fillet modifications to the projected sharp corners of the wheel outline into the soft jaws.
Soft jaws and wheel ready to be skimmed
Soft jaws and the brass wheel ready to be skimmed.   The residual original square stock has been roughly trimmed around the wheel circumference.
The jaws were printed and I have to say were somewhat cosy tight around the wheel geometry.   When the jaws were mounted in the machine vice, the wheel was not going anywhere and the excess backing brass was skimmed off quickly and easily with no apparent movement of the wheel in the jaws.
Finished wheel mounted in the jaws after excess stock had been skimmed off
Finished wheel mounted in the jaws after the excess work holding stock had been skimmed off.
The finished escape wheel and pallets mounted in the Thwaites clock
The finished escape wheel and pallets mounted in the Thwaites clock

I am really warming to this technique.   It is quick and easy to implement and any mistakes can be quickly rectified with a new 3D print without having to remake aluminium versions.  I like it and recommend it.

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