horology Archives - Woody's Workshop

August 15, 2024August 15, 2024

3D Printed Length Gauge for In Barrel Mainsprings

As designed by William Smith

I had received a clock to repair and wasn’t sure if the mainspring was correctly dimensioned. I remembered that William Smith had described a gauge for checking this in his book ‘Clockmaking & Modelmaking Tools and Techniques’ (pages 21 – 26). This gauging tool consists of two profiled plates that slide together to overlay the end view into the clock barrel. Bill’s design used 1/16″ brass plate but it struck me that a 3D printed version would be equally suitable and much quicker and easier to make.

In use the gauge is overlaid on the end view of the barrel as shown below. The point A is aligned with the outer diameter of the barrel arbor. The top plate is then slide until the inside edge of the barrel wall is aligned with point B. For a correctly chosen mainspring it should align with the corners C and D.

I sketched Bill’s design in Fusion 360 and extruded the two component parts to have a 2mm thickness before printing on my Qidi X Smart 3 in PLA. The two parts are fastened together to be a sliding fit with two M4 screws. The threads for these are modelled in the 3D print. A handling knob can be added in a similar fashion.

Here is my PLA printed equivalent.

The STL print files can be downloaded on the link below. It is not something that you will use every day but just a ‘useful to have when needed’ item. “Better to have it and not need it, than need it and not have it” (Jimmy Diresta).

clock main spring guide Download

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June 12, 2024June 12, 2024

The “Modern Clock” by Goodrich

This is available as a free download from Gutenberg to a Kindle

I have been working on a John Wilding ‘Scroll Frame Skeleton Clock’ which has been somewhat entertaining. Getting the clock in beat has caused some frustration. The pendulum crutch is elbow hinged to allow the beat to be adjusted but the adjuster sits behind the pendulum rod. It is easy to tweak the hinge angle but the pendulum rod then masks access to the tightening screw. In the end I resorted to getting the beat somewhere near and then fine adjusting it using the levelling adjuster feet on the base. It now seems to be running nicely, the beat sounds strong and timekeeping is looking good so far. As shown below I’ve got the light sensor of the Microset Timer on it at the moment so we’ll see how well it performs long term.

To revert back to the post title, John Wilding’s book on this particular skeleton clock makes reference to two books as being worthy of any clockie bookshelf – Britten’s ‘Clock and Watchmaker’s Handbook’ and ‘The Modern Clock’ by Goodrich. The latter is a bit of misnomer in that it was published in 1905 but it is a very detailed book and worth a read.

Not having either of these books I did a search. The Britten book is available from Amazon. The Goodrich book is available as a free download from the Gutenberg library. The download is possible in various digital formats, one of which is EPUB3 which is Kindle friendly.

To load third party documents into your Kindle you have to email the document as an attachment to your personal Kindle upload email address. This address can be found in the Settings section of your Kindle. I use this quite regularly to store interesting documents such as technical PDFs. I now have quite a collection of personal and third party techie documents stored alongside John Le Carre, Gerald Seymour and others. You never know when you are going to be bored while sitting on a beach and in need of some technical stimulation.

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February 9, 2022February 9, 2022

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

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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January 4, 2022

An alternative Bull’s Foot file for clock plate smoothing

A Bull’s Foot file comes in various formats. In its simplest form it is a small circular filing surface mounted at right angles to a handle. Its common use is for making good after a clock plate has been re-bushed when there is a need to selectively finish the newly inserted bush material to be flush with the plate surface.

The commercially made files sometimes have a curved lower surface or have a periphery ring or bordering parallel strips of metal to ensure that the filing action cannot go deeper than the existing plate surface level. Without this the filing action would lead to unwanted scratching and disfigurement of the plate.

I have got around the commercial geometry by using a homemade flat filing surface with two protective spacing mediums. To get quickly to somewhere near flush I use a piece of 35mm film (5 thou thickness) with a suitable hole punched in it glued or held over the bush. This protects the plate from a wider area of damage caused by my flat homemade Bull’s Foot. There is graphical representation of the concept below. This is a method suggested by William Smith and John Wilding in their various books. If I want to get even closer to the plate surface I have some sticky backed shim material that is 1.2 thou thick that I stick around the bush.

Graphical representation of a Bull's Foot file in use

With the commercial items, the bush is filed until flush using an increasing finer grade abrasion on the Bull’s Foot disc. This means having to have a number of different abrasive Bull’s Foot files. These are unusually difficult to source and expensive to accumulate.

My solution to this is to have a few Bull’s foot metal ‘blanks’ to which I mount appropriate circles of different grades of wet and dry paper. The chosen wet and dry is simply held in place on the ‘foot’ with double sided tape.

Homemade Bull's Foot files — Homemade Bull’s Foot files and handles

The blanks (no more than 12mm diameter) are made from a disc of 3mm ground flat stock brazed onto a 3mm silver steel shaft. Once brazing is complete the disc is trued in the lathe by gripping the shaft. The shaft is then heated to allow bending at right angles and then mounted in a home made handle.

The handle is around 75mm long and is made from 15mm wooden dowel with a strengthening collar made from a 15mm length of 15mm copper water pipe. The dowel is turned down such that the collar is a push fit and a 3mm pilot hole is drilled in the end face. After preparation the dowel is varnished with the collar in place. These homemade handles get used on other tools around my workshop such as needle files and gravers.

I agree the wet and dry will not last for ever but it is a cost effective and flexible option to a box full of ‘proper but not used very often’ Bull’s Foot files. An alternative to using wet and dry is to Araldite shaped pieces of broken files onto a similar shaft and handle concept. These would last longer but once again more handles would be needed to cover the grades of file needed. The spacer medium would still be required to protect the plate surface.

For those of you more adventurous there is an alternative handheld solution detailed on the Sherline website.

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March 4, 2021March 4, 2021

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 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 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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