The church clock works intermittently! It used to be wound by hand (by Don Impey among others) and was fitted with an electric winder made by Paul Jaye around 1990. The Jayes moved away and the winder broke, and the clock stopped. Eventually David Smallridge and Richard Earl took matters in hand and the clock started working again in August 2011. Well done, chaps!
David designed and fitted the new winding mechanism, and Richard deals with maintenance and keeping the clock running to time. David gave Emrys Williams a guided tour on 10 November 2011 to help write this article.
The church tower is divided into three sections, one above the other. At the bottom is the tower base, the room behind the west door of the church. A spiral stair in the corner of the tower leads up to the clock room, where the clock mechanism sits. This room is also where the ropes for the bells hang, and where the bellringers stand. The driveshaft from the clock mechanism to the hands outdoors goes straight through the wall of the tower from here. The stairs lead on up to the bell room above, which, surprisingly, is where the bells are hung.
The photos here are of the real clock and were taken by the house incompetent photographer, Emrys Williams. Sorry about the photo quality, I’ll go back and make some better pictures, taking much longer. The technical information here is cribbed from the splendid The Turret Clock Keeper’s Handbook available free from Chris McKay.
This bit below is supposed to be an audio player where you can listen to the clock strike noon. First the clock ticks, then it strikes twelve. Then there’s a lot of whirring while the electric winder rewinds itself. Then there’s the extraordinary reaction of the listeners, Emrys Williams and David Smallridge, right at the end!
You can download that mp3 file by saving the target of this link.
The power supply
The clock was first powered by weights pulling down on steel cables wound around drums. Two power sources are needed, one to keep the clock ticking and the hands going round, and the other to power the striking mechanism that chimes the hours. These two separate mechanisms are called the going train and the striking train. There are two cable drums in the clock, and at least one of the weights is still present, but the cables have been removed and winding by hand is no longer needed. Both of the weight drives have been replaced by “climbing monkey” motorised chain mechanisms. It’s odd, but these mechanisms don’t seem to be commercially available. Every one seems to be custom made!
For a climbing monkey drive, a chain sprocket is added to the shaft that carried the winding drum for the original weight drive. In the picture below, the large sprocket wheel on the left is for the going train, and the small sprocket wheel on the right is for the striking train.
A loop of chain passes over each drive sprocket and hangs free beneath the clock. On one side of this loop hangs the climbing monkey. The image below shows the climbing monkey for the clock drive, just designed and installed by David Smallridge. He’s upset that it’s not neater. He designed it for a smaller weight, because nobody really understood what was required. Then experiment proved a larger weight was needed and odd bits of steel were stickytaped on. He vows he will get back and redo it properly in due course. The going train climbing monkey is powered by a pair of constantly charged car batteries, to provide plenty of reserve power should there be an AC failure.
The climbing monkey contains a switch assembly and an electric motor driving a small chain sprocket. The weight of the climbing monkey pulls one side of the chain loop down and causes the chain and monkey gradually to sink. When the monkey hits a limit near the floor, the switch assembly turns the motor on and the monkey climbs back up the chain in a few seconds. When the monkey hits a limit at the top, the switch assembly turns the motor off and the monkey stays in position on the chain. It takes several hours for the monkey to sink from the top limit to the bottom limit.
The sprocket wheel for the going train climbing monkey chain is attached to the shaft that carries the old winding drum for the original weight drive, the barrel arbor. This sprocket wheel has a much larger diameter than the drum, so, to provide the same constant drive torque to the clock, the climbing monkey’s weight must be much smaller than the original drive weight. [Does the orignal drive weight for the going train still exist?]
The sprocket wheel for the striking train is attached to the second arbor, not the barrel arbor. The second arbor is the shaft originally driven by cogs directly from the barrel arbor. This means that the striking train climbing monkey can be very much lighter than the original weight drive, but it has to climb much further. The monkey falls about a metre when the clock strikes twelve. This monkey doesn’t wait to hit the floor before it starts climbing, it climbs any time it isn’t in contact with the ceiling.
[to be expanded]
The mass of the going train monkey is …
The diameter of the going train chain sprocket is …
The diameter of the going train barrel was …
The mass of the striking train monkey is …
The diameter of the striking train chain sprocket is …
The diameter of the striking train barrel was …
The gear ratio between barrel arbor and second arbor is …
The mass of the old weight sitting on the floor under the clock is …
This general view of the back of the clock shows the internal clock face, which carries only an hour hand. The hand rotates anticlockwise, so the numbers on the internal clock face are altered to suit. The internal face is for the convenience of whoever has to set the time.
The cage that holds the clock mechanism is a posted frame type. This was popular from 1790 to 1850. The upright bars of the frame can be individually removed to repair the clock. The uprights at the ends are made of cast iron rather than wrought iron – it’s possible still to see the flash marks from the casting. It’s a side-by-side movement, with the going train on the left sitting alongside the striking train on the right.
The lever hanging down and tied up with string was probably part of the maintaining power mechanism. This acted to keep the going train running while it was actually being wound up. With the electric powered drive, this is no longer needed.
The escapement – the mechanism that interacts with the pendulum to provide the timekeeping – is a deadbeat escapement. In the image below, the escape wheel is the cog with the odd-shaped teeth. The anchor is the inverted-vee bracket screwed to the rod above the escape wheel. The anchor swings back and fore as the pendulum moves. The pallets are the two metal ends of the anchor, the bits that actually engage with the teeth of the escape wheel. The features that make it a deadbeat escapement are (1) the pallets are curved, with locking faces (the face of the pallet that locks the escape wheel and prevents it from turning freely) that form part of a circle centred on the anchor’s pivot; and (2) there are separate locking faces and impulse faces, the slanted ends to the pallets. For most of the pendulum swing, the locking faces slide over the teeth of the escape wheel without moving the escape wheel at all, and without any force being applied by the escape wheel to the pendulum. Just as the anchor swings the edge of the locking face off the tip of the escape wheel tooth, the escape wheel starts to move round and pushes against the impulse face. This happens as the pendulum goes through the bottom of its swing. It’s this push that keeps the pendulum swinging. The deadbeat escapement was popular from about 1715 onwards, and was common throughout the 19th century.
There are thirty teeth on the escape wheel.
The going train
[to be completed]
The striking train
[to be completed]
The pendulum swings beneath the clock. There is a screw adjustment on the pendulum to regulate the timekeeping. The pendulum is quite heavy and is given a wooden case to minimise the effect of outside influences like draughts on the timekeeping. The end of the pendulum can be seen through the doorway in the case used to regulate it.
When the pendulum swings to the left at the bottom, the left hand pallet on the anchor rises out of the escape wheel teeth, and one tooth of the escape wheel gives the pendulum a slight push to the left as it slides over the left hand impulse face. The escape wheel moves round and comes to rest with a different tooth touching the locking face of the right hand pallet. All that action makes a tick sound and happens just after the pendulum moves left of bottom dead centre. When the pendulum swings back right of centre again, the right hand pallet disengages and another tooth of the escape wheel hits the left hand pallet locking face with a tock sound. In a well-constructed clock, the tick and tock sounds are indistinguishable, although one is made by the left hand pallet and one made by the right hand pallet.
EJW measured the period of the pendulum (that’s one whole swing left to right and back to left again) with the audio recording made of the noon chimes and the audacity audio editor program. A whole period is the time from a tick to a tock and back to a tick again. The best estimate was that the period was 3.533 seconds.
This estimate for the period and the count of 30 escape wheel teeth above would indicate that the escape wheel completes one revolution in 105.99 seconds – call it 106. That’s a bit odd, since that would imply that there was a 34:1 gear ratio between the escape wheel and the minute hand, and that’s a hard ratio to construct because its prime factors are 2 and 17, and a 17:1 gear ratio is physically quite had to manufacture. It would be helpful to go back to the clock and count the teeth on each gear carefully!
The pendulum length is ….
Screwing the pendulum adjustment up one turn adjusts the timekeeping by …
[to be completed]
The maker’s name on the clock is “Defontaine, London”. The church booklet St John the Baptist – A Brief Introduction states that the clock was installed in 1890. There is a reference to “De Fontaine, Louis of London A brief document giving some working dates for Louis De Fontaine of London (Updated 12 Oct 2009)” at http://www.clockswatches.com/showindex.php?em=D&page=2 but that requires paying money. Ancestry.com (which also requires paying money, but I already have a subscription) shows Louis Defontaine aged about 75 in the 1841 census, born abroad around 1766, a watchmaker living in St Pancras. He was listed in the 1825 Pigot’s Directory of London and in the 1848 Post Office directory, and the 1851 Post Office directory and the 1856 Post Office Directory with a clockmaking business at 70 Wilsted Street, St Pancras. It seems unlikely that this is all the same person in 1890. Maybe his business carried on in his name after his death, or maybe he had a son of the same name? But the 1841 census shows him living with a plasterer and his wife, with no servants, which sounds unlikely for the proprietor of a successful business. He may well have died in 1848, according to Freebmd:
Surname First name(s) District Vol Page
Deaths Jun 1847 De Fontaine Clara Mary St Pancras 1 270
Deaths Mar 1848 De Fontaine Louis St Pancras 1 327
Deaths Sep 1848 De Fontaine Frederick Peter S Pancras 1 *
These are the only De Fontaines to die in the whole country from 1841 to 1861, so it seems possible this was the right family.
Did his business continue after his death? Or is the date given for the church clock wrong? Or maybe the clock was second hand? Or maybe I have no idea what I’m talking about? Because Anceestry.com also has the text of G. H. Baillie, Watchmakers and Clockmakers of the World, London, England: A. R. Mowbray & Co. Limited, 1947. That book has various Fontaines and De Fontaines of varying dates and spellings, but doesn’t have the Louis De Fontaine from St Pancras. It could be some completely different company.
The Public Face of the Clock
Meanwhile, here is a picture of the clock face taken by Emrys Williams in May 2011 and placed by him in the public domain.