Unique Observatory Controlled Transmitter.

A new video has been uploaded to YouTube of a Gents' Observatory [controlled] Transmitter. The very special [and unusually complicated] Gents' master clock dates back to 1932. Transmitter is a term used for electric master clocks which send out signals to slave clocks and other timing mechanisms. Controlling a distant "master" clock, like this one, would allow observatory clock precision without any of the vital environmental needs: A complete absence of vibration, a massive wall [or bedrock] and very steady temperature control. Caves, dungeons and cellars were all popular to house such precision clocks. [Regulators is the correct horological term.] 

I will attempt to describe the "Transmitter" mechanism as simply as possible: The clock is controlled by the six time pips sent out by the BBC at that time. The pips were timed to a very high level of precision by very precise clocks kept [and constantly checked against the movements of the stars] at astronomical observatories. Apart from astronomical studies, timekeeping was a major part of an observatory's duties. Most observatories at that time had one or more precision clocks.

A see-saw arrangement of two electromagnets is situated at the very top of the master clock mechanism. These electromagnets lift or lower a regulating weight onto a tray on the pendulum.

Another, separate timekeeping mechanism, in the middle of the clock case, decides if the clock is fast or slow compared with the observatory time signal.

Weight regulation of precision clocks has a long history. Normally, small weights are placed or removed manually onto a tray placed near the middle of the pendulum rod. Sometimes tweezers are used to place or remove these weights to ensure the pendulum is never disturbed.

The genius of Gents' engineers was to use electromagnets to place or remove the regulating weight on the pendulum tray. A clock with a weight added will slightly gain. [Go faster] When the weight is lifted free of the pendulum the clock will change to a slower rate.

If only it were that simple to achieve perfect time control from a reference precision clock at a distance. This was cutting edge technology for its time. An added Relay unit accepts the 6 timing pips sent down the telegraph wire from the distant observatory. This in turn passes on a brief signal to further [time checking] units on the transmitter. The seesaw unit will then be triggered to leave the weight alone, lower or raise the weight depending on the exact timing of the pendulum relative to the precise observatory signal.

Towards the end of the video a bell striking mechanism is also controlled by the transmitter via a series of accessory units. These are shown in action during the hourly strike run. All in all, a fascinating display of a whole series of Gent's timekeeping products in excellent, original [or finely restored] condition.

All of these fascinating units apply electricity to achieve remarkable results once entirely the domain of centuries of mechanical clocks. The increase in accuracy of timekeeping, reliability and the precise control of dials and bells is the stuff of electrical horology. Where a small number of British firms competed in the first half of the 20th century for the world market in improved timekeeping methods. This led to historical changes in timekeeping for the railways, offices and factories as universal timekeeping could be brought, at relatively low cost to every corner of commerce.

For the first time in history every clock dial could show the same time and required no regular and costly repairs for natural wear and tear. Imagine the effect on a huge factory complex where every clocking-in dial showed the same time. Or vast, multistory, office blocks where every wall dial agreed with every other. Where factory machine, run times and productivity could actually be measured and printed out. All without a single man, with a watch and a salary standing over every one of them.



Pulsynetic C6 & C7 master clock pendulum and bob.

Sometimes a Pulsynetic C7 master clock is obtained which lacks a pendulum. In the complete absence of factory spares and as a service to those faced with the construction of a completely new pendulum I offer the following images: The original flat rod would have been Invar with diagonal "scratches" [hatching?] to show its true heritage. The "bronze" finish on the bob was once popular on fireplaces and fittings.

The large rating nut could be turned to make coarse rating adjustments. Smaller changes to slow the clock's rate could be made by adding small weights to the top of the rating nut with tweezers. This avoided stopping the pendulum which often results in an erratic change of the original rate.

Weights could also be added to the top of the pendulum bob to speed up the clock's rate.

The threaded rating screw at the bottom of the pendulum rod is apparently a cycle thread. 5/16" x 26 TPI.

An ordinary, rear bicycle axle could no doubt provide the donor material and save the purchase of a special die to cut the thread on a bare rod.
A cycle wheel fixing nut would do at a pinch in the absence of an original.
The cast rating nut has the appearance of a water valve wheel. Here the underside is shown.

The rating nut now fitted but inverted when quickly posed for the photograph.

The slot in the Invar rod where the movement crutch pin fits. A slot provided freedom for vertical adjustment or change in position due to differential expansion without binding. Note the diagonal lines to indicate Invar rather than plain steel.
Invar is a nickel-steel alloy which has almost zero thermal expansion. Changes in temperature should not alter the rate of the clock.

A threaded crossbar [with large washers to trap the suspension spring] normally rests in the cast-in v-grooves in the Pulsynetic master clock movement.

The entire C6/C7 bob. Removing the small screws in the top plate will allow the inner weights to be fitted and removed for examination.

Click on any image for an enlargement.


WT for sale: Regulator Clock Company. UK


An interesting example of a later, stepped frame WT has appeared on the Regulator Clock Company [UK] website: The Regulator Clock Company

This C40B[?] WT movement is mounted in/on an exquisite mahogany table and case suitable for the highest standard of furnishing. Though some might argue that the WT never enjoyed such luxurious accommodation, in reality, that is hardly the point. Nobody really wants to place a highly collectible WT in a mock-up of a typical clock chamber with all its [usual] disadvantages of whitewash, squalor and detritus. At least not when that WT is to be housed in a comfortable home or smart office as a fascinating showpiece.

Some work may still be required to run a drive from one of the bevel wheels, via lead-off rods, out through the glass case to a suitable turret clock dial. Which would make it a far more interesting and attractive display for a purist. Drilling glass and polishing the hole is not a difficult task for a skilled glazier. Though making a hole in the glass "envelope" might open it up to the escape of typical WT 'noise.' Which the pretty case may well have helped to dampen somewhat.  WTs and domestic bliss do not [usually] make ideal bed fellows where disinterested partners are concerned. Though this fine example and its cabinet could never be described as "fugly."

The 2-handed pilot dial is also very unusual for a WT but rather attractively done. Most WTs enjoy a simple rotating disk attached to the "front" bevel wheel, with a fixed pointer. This is known as a time setting dial and is usually silvered and clear lacquered. The maker's name, "Pulsynetic" and some reference to patents is usually engraved thereon. Quite how the hands of this dial are driven is impossible to see from the illustrations provided. A mechanical drive from the bevel wheel cluster? Rather like a later, two hand conversion of an elderly, single-handed, 30-hour, long case clock?

Though painted black, as if of the earliest form, the later, stepped movement is usually to be found in battleship grey. Perhaps not to everybody's domestic taste? The eggshell black certainly looks the part against the plated parts typical of a later WT movement. Earlier movements would have had deep, gold lacquered brass or bronze components regardless of frame colour. The bandaged coils to the large, drive electromagnets are also later but still worthy of admiration. Their sheer size and workmanlike finish makes them interesting in their own right.

The large wormwheel indicates a heavy-duty model intended to drive the heavy hands of up to four, large, turret or tower clock dials. It is difficult to identify whether this is a Gent's C40B or C40C but the large bevel wheels and stepped form of the mainframe further confirm a larger model than the [almost] ubiquitous C40A.

One should ask how this WT is driven and controlled? Does it have a robust 24Vpower supply and electronic control unit to provide the vital half-minute, low voltage timekeeping pulse? It will certainly never keep good time nor operate in its typically, hypnotic fashion without some "electrickery."

As this WT is a commercial sale item perhaps I should not have pointed out the cosmetic "difficulties" in quite such a forthright and, shall we say,  'pedantic' manner? I am a clock enthusiast not a buyer of antique furnishing pieces. I see my task as accurately recording and illustrating the history of the components of the Gent's Pulsynetic timekeeping system for posterity.

Surely anyone contemplating the purchase of such a rare and unusual item might be tempted to search online for more information. If some homework is required before burning the plastic: The only known sources of information on Gent's Pulsynetic Waiting Train movements are my own WT blog, the Pulsynetic website and Colin Reynold's excellent books on the Gent's Pulsynetic timekeeping system.

The asking price for this WT and its pretty stand/case is not insubstantial but these things do not come up for auction every week, nor even once in a decade. How does one value such rarity? It is, without doubt, quite beautifully presented. Since I am not in the market for a larger WT at this elevated price level I will leave it at that.  The following link will take you straight back to the WT on offer:

The Regulator Clock Company

Had it been a bare movement, perhaps a rougher example and needing some skilled, TLC, but at only half the asking price, I might have been more than tempted. Let us hope this particular WT finds a comfortable, new home. Where it will be cherished for its true genius in design, hypnotic mechanical details [when working] its long history and its vital importance to 20th century, public timekeeping.

This WT is now SOLD.

Click on any image for an enlargement. 


Restored C40A Waiting Train movement for sale:


With the permission of the owner I have copied and resized the excellent original images from The Time Workshop website.

It must be remembered that all WT movements were hand built at the Gents factory. Steady improvements were incorporated over time rather than sudden overnight changes. WTs are rarely found for sale and those which have appeared on eBay [for example] have not always been kindly treated. To find a restored and tested example of this age, quality and completeness is very unusual indeed!

The original pendulum is included but not shown in these images. It is visible in the video at the bottom of the page.

This Gents Pulsynetic C40A WT movement, which has been restored by a turret clock expert, is offered for sale. It has been running well on test to ensure reliability.

The details of its many brass components certainly suggest pre-WW2. Possibly early 1930s? There is so little information in the public domain on exact dating that one must seek clues in the shape and materials of its construction and make "educated" comparisons.

There are no plated components which would date it as possibly early 1930s.

The coils lack of later, concealing, protective wax [late 1930s] and even later 'bandages' suggest an early example.

The 'hooked' form of the steel gathering pawl is also early.

While the support boss for the contact assembly is horizontally slotted, for adjustment, so not of the very earliest style.

The pendulum drive armature has a roller rather than the very earliest 'hook' form.    
The sinuous form of the cast mainframe over the electromagnets is definitely a pre-war sign. Later frames had a diagonal slope just here.

It is nice to see a full bevel gear cluster, correctly silvered time setting dial and pointer below the large crown wheel to the motionwork. The Hipp Toggle damper is also present. As is the eccentric depth stop drum and the time setting handle and crank. An unusually complete example.

The lacquering to the brasswork is not well seen in these images but adds a quality touch.

I have no data on when the Gents WTs moved away from the early semi-mat, black finish to the later marine blue-greens. Or even later battleship greys. Though black certainly looks highly appropriate against all the lacquered brasswork highlights. This always reminds me of glittering gold jewellery laid on a black, velvet cushion.  All very desirable in any WT. Even more so on one which could be 85 years old!

Gents' WT design was a very successful, compact and powerful electric turret clock movement. It made weight-driven clocks completely obsolete overnight. What made it even more remarkable was its timekeeping stability, reliability and precision despite constantly changing weather conditions.

When controlled by its master clock's time signals it provided seconds per-week-accuracy to public dials. The WT in larger sizes went on to drive the hands of record breaking sizes of clock dials around the globe. Such dials were completely beyond the ability of any practical or affordable weight driven clocks.

Now add in an end to the need for regular rewinding, its low maintenance and only occasional lubrication. The lack of massive weight chutes allowed a WT installation to be placed where clocks had never previously found a home. Dials appeared on factory chimneys, war memorials and on office blocks and towers where they ran reliably without constant attention. The WT was not only an engineering marvel but an architectural ones as well. Even this very compact C40A movement could manage the hands of exposed 6' dials in all weathers.

For the avid collector the WT offers the enjoyment of watching a real pendulum swing. This is no 'soulless' electric motor. The infamous Hipp toggle is renowned for its hypnotic effect on the fascinated observer. As the toggle rattles quietly across the V-block it almost fell into the notch on that last swing... but then keeps going... and going... until, finally it drops in and closes the contacts. The pendulum is given a push by the huge electromagnetic coils... and so the game begins all over again.

Here is a video of this WT in action.

Sellers website link:

Click on any image for an enlargement. 


An early C40A WT under restoration:


A member of the Antiquarian Horological Society has kindly sent me some images he took on a recent group outing. The AHS Electrical Group were visiting The Cumbria Clock Company in Penrith, Cumbria. [Formerly Cumberland in the north west of England]

The Cumbria Clock Company 

Electrical Horology Group - AHS - Antiquarian Horological Society

An early WT C40A was on test following restoration by the Cumbria Clock Company. I  have done my best to obscure the faces of members of the visiting group to avoid invading their privacy. I you think further work is required please contact me at the email address above.

The earliest WTs [Waiting Train movements] were usually painted black. Though this should not be taken as a fast rule for identifying an early WT. There is far more to it than that and WTs follow a series of changes over the years.

Note how the main frame casting has a gentle curve with a horizontal section before taking a sharp turn downward again. This is in the area just above the large drive electromagnets and is a sure sign of a pre-WW2 movement. Later, post-war movements had a straight, but sloping frame section, just here.

The electromagnet coils have visible wire with a thin coating. Later WT coils had a thick wax coating for better protection but which concealed the wire turns. This too gave way, after the war, to a form of bandage for even greater protection from damp and accidental damage.

Interestingly, this early WT has a later contact assembly. This is easily recognizable as having pressed steady bars with gentle bends. Rather than the earlier castings which had sharp bends.

The contact assembly support post is also later. Having a slot for adjustment of the Hipp V-block position relative to the toggle which is fixed to the pendulum rod.

However, the contact assembly is made of brass. Not the much later plated steel components of the same form.

In fact all of the minor components are of brass. Which is correct for an early movement. It is quite possible that the original contact assembly was replaced due to wear or damage. Complete replacement being more cost effective than trying to repair the original on-site.

The WT's contacts were probably prone to oiling should the clock keeper [or the vicar] was too enthusiastic with the lubricant. Particularly as the contacts were positioned immediately below the Hipp toggle assembly. Oiling the Hipp toggle on a moving pendulum was apt to become a messy business in unskilled hands! There are always those who think if a little is good then more must be better. It would never occur to them to mop up the excess oil before it ran down onto to the vital electrical contacts.

The pendulum suspension, bearing housing is also in black rather than the later plated finish.

While the armature for the twin, drive electromagnets is a roller rather than the simple hook form of the very earliest WTs. No doubt the Gent's factory staff would apply the latest modifications as each WT was hand built. This would result in a steady but limited change in appearance. Rather than fixed steps falling on clear dates. There would be no desire for originality or even a match of all components if something better had been developed along the way.

It is difficult to judge but the serial number on the WT relay, pivot plate [bridge?] seems to be 248 or possibly 243? This confirms an earlier date. With very little numbering data to go on I might have suggested early 1930s or late 1920s.  Certainly an attractive example of the most common size of C40A WT movement.

This image shows the Hipp toggle has dropped into the V-block and is about to close the drive contacts on the return swing to the right.

The freely swinging, Hipp toggle and its associated V-block were an earlier invention which set the minimum arc of the pendulum when driven by electricity. Whenever the arc of th pendulum fell below the limit set by the arrangement of toggle and V-block the toggle would fall into the V-block. On the return swing of pendulum the V-block is forced downwards, closing the electrical contacts just below.
Rear view of the WT movement showing the worm, wormwheel and bevel gear cluster.No attempt has been made to suggest earlier wiring to match the age of the movement. No doubt safety and reliability were considered of greater importance.

All the brass components would have been lacquered in deep gold on the original. These parts look as if they have been lacquered with a clear finish. Deep gold, cold applied  lacquer is available. Though the original lacquer would have been applied to pre-heated components. Requiring considerable skill to achieve an even finish without runs or build up on sharp edges.

Yet again I must express my sincere gratitude for being sent these interesting photographs. Without which this blog would be much the poorer for content and interest.

The presence of people in these images is unusual and requires a decision whether they should remain or be digitally painted out. While they do offer a clear suggestion of the scale of items present I am unwilling to publish their images without prior consent. One could argue that by simply placing themselves in a public situation they should expect to appear online. This is obviously a matter of personal preference. Though the difficulty of identifying and then contacting all of those present, for permission to post their images, is all but impossible at a distance. I have therefore chosen to obscure their faces [albeit crudely at times] as a precaution against causing offense. No doubt more sophisticated software would have done a much better job but I do not have such software. PhotoFiltre is free image handling software and has a large range of basic options. Though not the magical "buttons" and controls of expensive software like Photoshop. Even if I could afford such software it would be largely wasted on me and would require a very steep learning curve to make the most of it.

Click on any image for an enlargement.


The lost, world record breaking Singer factory WT?

This large and complex WT movement from 1926 is shown on its rather crude, timber test bench. No doubt it would be erected on a prepared, concrete plinth placed centrally in its intended installation site.

This is believed to be the WT movement from the now-demolished Clydebank [Glasgow] Singer factory. Though there were plans to display the WT movement in a modest setting locally it was [apparently] lost or mislaid. Considering that this WT movement set a new world record for public clock dial size this lack of respect for Britain's industrial heritage leaves one saddened and bemused.

Why not display it in the Science museum in London if Scotland had no real interest in its own industrial history? It's not as if Singer was an obscure manufacturer of anonymous widgets. It was world famous for its sewing machines! Though less well known for its "difficult" employment relationships with its workers.

The sad tale of the Singer clock

The WT's timekeeping would not have been affected by its temporary, timber support while under test. The Waiting Train function would easily correct any variation of timekeeping. While the Hipp-based switch for the drive contacts would ensure a stable pendulum arc. [Swing] The Hipp V-block in this case has several "Vs" to allow a degree of variation and a further element of security against a miss as the toggle drops into one of the grooves to force the drive contacts, firmly together.

Note the huge scale of the driving wormwheel, [top left] dominating bevel gear cluster and massive lead-off couplings to drive the giant clock hands. Gents' skills at casting complex forms is also well seen in the flat, cast bed on which the entire movement is based.

The bevel gear cluster has four wheels so confirms it was intended for a high tower with a dial on each face. There would be absolutely no point in adding superfluous bevel wheels for non-existent dials. The scale of the movement suggests an extraordinarily large clock installation.

The image alongside is of a similar but even more complex WT movement.

Here is an illustration from Gent's WT promotional material. The detail is much better seen than in the original photograph above. With the relatively tiny, WT relay solenoid, on the extreme left, controlling the timekeeping. [A small, diagonal bar supports its pivots.]

The apparent complexity at middle-left obscures the movement's actual simplicity. A counter-weighted, electrical contact bar provides a reliable drive contact for the large electromagnets visible just beneath the large bevel wheels. To the left is the sturdy ratchet wheel with its heavy bearings. Which turns the heavy pendulum's linear swing into a powerful rotating force via a massive drive pawl.[hook]

The pendulum is driven by means of a crutch from the electromagnets' armature. Though the actual implementation is obscure or not seen. Small but clever details can be more easily be seen: Like the pendulum support bearings being constantly driven by a ratchet wheel to avoid flat spots on the outer race over time. This practice was carried over from the earlier, 1911 Liver Clock movements in Liverpool. The pendulum support,  journal bearings themselves did away with the fragile flat, suspension springs. Which has been common to most pendulum clocks for well over half a millennium.

The forward bevel wheel has a typical Gents' time setting dial attached. Though here it must be of quite extraordinary size. Handy for re-setting the clock hands accurately to British Summer and Winter time. The sheer power of such a movement to drive enormous and heavy clock hands in all weather conditions on a very high, exposed tower can only be imagined. Constructing a weight driven clock movement to accomplish such a task [to precision master clock, seconds per month, timekeeping standards] completely reliably and automatically would have been quite literally impossible. The WT has no use of architecturally-limiting weight shoots, massive drive weights, nor a team of exhausted winders to raise them at frequent intervals.

I have added captions to the third image for easy recognition of the vital components in this close-up. Left click for further enlargement to see the fine detail.

The Hipp toggle and V-block form the [minimum] pendulum arc regulating switch and are very typical of most WTs. Only the contacts themselves are more complex to carry the heavy DC electrical, pendulum drive loads reliably over a very long period of operation. A long lever and adjustable, coiled tension spring seem to be associated with the contacts. No doubt some means of extending the drive impulse were employed to maximize the electro-mechanical power available in difficult weather conditions. Ice and high winds would unbalance the clock hands demanding more torque and/or braking power.

Fortunately, the genius of the Hipp switch, combined with Gent's brilliant engineering, provided a near-miraculous, 30x increase in torque, instantly and on demand. In quiet conditions the pendulum might ask for a push only once every minute or even longer. While in winter storm conditions the clever Hipp switch can automatically demand a drive impulse on every other pendulum swing.

It should be remembered that this single WT movement would be responsible for the incredibly accurate timekeeping of  four sets of clock hands on four different tower faces with tens of thousands of daily onlookers. Each exposed dial will suffer its own unique weather conditions from one hurricane force moment to the next and all high above the open sea. All of which is regulated, to a few seconds per month, by a remote master clock. Connected only by a thin length of wire carrying a short, low voltage, DC impulse at half minute intervals.

It would be nice to think that this huge WT is sitting quietly somewhere awaiting eventual discovery. Though it seems much less likely with every passing year. It was a unique and brilliant solution to a demand for accurate timekeeping on ever larger clock dials to add to industrial magnate's prestige. 1926 was barely two decades after the first simple, WTs were being manufactured. Yet this WT movement shows remarkable sophistication and a firm and confident grasp of the engineering required to do a job well beyond the limits of all previous experience. This movement alone speaks volumes about the skills and genius of the Gent's designers and the company's manufacturing abilities.

Click on any image for an enlargement.


A heavy duty turret slave.


A contact has kindly sent me some images of remarkably sturdy Gents turret slave. This one is much earlier than the grey finished slave in the previous post. Note the substantial base casting and the heavily built front and rear plates. The drive pawls are also built to withstand heavy loads over a long working life with little or poor maintenance. This movement even has a time setting dial just like a turret clock or WT.

Twin electromagnet coils are provided for increased power [hand driving torque]. The electromagnets briefly pull back against the tension of a spring on receiving a short electrical impulse from the master clock. When the electrical impulse stops the magnets switch off and the spring then pushes the clock hands around by a half minute every 30 seconds.

This method of doing things avoids the movement being made to physically overcome a complete lock-up in the drive to the clock hands. The spring isolates the electro-mechanical drive system from potential damage.

There is a large, brass, spoked wheel visible in the middle of the mechanism. This is not the drive wheel but belongs to the heavy-duty motionwork. As does the partially hidden wheel on its left. Their respective drive pinions are out of sight in the upper image. The drive wheel is almost hidden behind the large wheel but can be recognized by its 120 ratchet-shaped teeth.

A rotating, air-brake "fly" is visible on the far left of the movement. This is presumably to avoid the hands accelerating out of control in the event of serious clock hand imbalance. Turret clock hands are almost always balanced with counterweights. Which adds to the moment of the already heavy hands.

Advancing the clock hands to set the time requires that the direct drive and hand locking provided by the slave are interrupted. At such moments the system is more vulnerable to overrun through imbalance. Possibly through icing, flocks of birds resting on the hands or even from high wind forces. Even if the slave "clock" keeps accurate time it will still be required to be re-set to summer and winter time.

The forked, universal drive joint is seen in the middle of the back of the movement.

Click on any image for an enlargement.

A large, Gents, Turret Slave movement.

Large slave clock movements were used when a medium-large clock dial was given a glass cover or was installed in a protected [indoor] environment.  Perhaps within a railway station, a large office foyer or factory building. One large dial allowed the time to be read at a great distance. This saved the expense of many small dials and the greater risk of timekeeping scattering between them. Glass covered dials only worked well when the sky could not be reflected. 

A general view of the large slave movement. The maximum dimensions of the flanges on its white protective box are approximately 10" high x 8" wide. [25 x 20cm] The overall protective metal plating and paper covered coil indicate a later movement.

A slave movement was a far cheaper and simpler option than installing a weight driven turret clock or electro-magnetic Waiting Train movement. Being so compact, the large slave could be installed where nothing else would fit. Being highly reliable, it could be installed where maintenance access was very poor. Considerable effort was expended in making these large slave movements robust and well protected against deterioration due to weather, wear or condensation.

These turret slave mechanisms, like their much smaller brethren,  are really spring driven. Except that the spring is briefly tensioned only at each half minute by the large electromagnet. Once the brief electromagnet impulse ends, the magnetic circuit collapses and the spring pulls the hands around the dial in a single, half minute step. The electrical impulse was provided by an accurate master clock controlling a complete impulse timekeeping system. The large slave would usually be placed in electrical series with the rest of the many smaller dials and any other equipment in the time circuit. Though its relatively high resistance usually required a serious step-up in DC voltage to the system. Since this involved considerably greater expense, in the days of battery bank driven time systems, the slave dial might have been controlled by a relay and its own, separate power supply.

This image shows a closer view of the coil spring which drives the hands at half minute intervals. The spring's tension can be adjusted with the screwed rod on its left. Though here it is at its most relaxed position.

The various silver-coloured levers look rather complex but simply drive the ratchet wheel forward and prevent its backward movement. By the skilful design of these levers, the hands of the clock are prevented from ever moving too far at each step or falling back. Either of which would ruin the timekeeping.

Here is an even closer, labelled, view showing the coiled drive spring just above the double-locked, backstop lever. The long horizontal lever has a downward extending pawl which sits in the teeth of the drive wheel. This pawl stops the wheel from ever turning backwards. It is hinged on the left so that it can rise or fall slightly to allow only one tooth to pass at each electrical impulse.

On the right of the long lever is a reinforced ramp with a sturdy stop pin to prevent the backstop lever from rising beyond a predetermined height. No doubt the mass of the ramp also acts as a weight to further load the backstop lever against slippage. 

Just to the right of the backstop pawl is the drive pawl. Which looks rather like a downward turned bird's beak. The sharpened tip of the beak rests in the teeth of the drive wheel close to the backstop. Their closeness is important to avoid backlash between their actions. The drive pawl is hinged at the pin on the right and retained by the wire spring clip. Just below the pin is an adjustable stop screw to prevent the drive lever and its driving pawl from moving too far backwards.

Here, the slave movement has been [temporarily] placed on its side to show the entire drive lever extending from above the locking ramp, at the very top. [Seen at left.] Right down to the armature plate fixed on the bottom end near the core of the large electromagnet. [Seen on the right in this image.] These slave dials must always be used the correct way up or the gravity-aided levers lose their function. The electromagnet is usually placed at the bottom.

A thin spring blade can be seen running parallel with the drive lever. This spring ensures the drive pawl always stays in contact with the drive wheel teeth by applying a gentle downward force on the tip of the rocking "beak."

At each half minute, a brief electrical impulse energises the electromagnet. The drive lever's armature is quickly pulled in against the tension of the drive spring. The drive pawl at the top of the lever moves briefly to the right against its stop screw. As soon as the impulse is over the coiled spring pulls the drive pawl [beak] forwards to step the 120 tooth ratchet wheel forwards by only one tooth. The minute hand, on the same shaft as the ratchet wheel, is thus moved on by half a minute.

Meanwhile, the pin on the drive lever contacts the ramp on the backstop lever and prevents it from lifting high enough to allow free movement of the minute hand during the impulse. The long and heavy hands on the large clock dial might otherwise take control of the slave movement. It is vital that this can never happen or accurate timekeeping will be lost. The minute hand must always point accurately to a full minute. Or midway in between at the half minute. Any less or more will cause doubt in the person reading the time. Clocks are meant to be read at a glance. The advance of the minute hand is so quick that the casual watcher might not even notice it.                                                                                         

The view from the other side of the slave movement showing the large, ratchet-toothed, drive wheel [seen on edge] on the right.

The smaller gears are the motionwork which reduces the minute hand rotation by 12:1 to drive the clock dial's hour hand. These gearwheels are made robust enough to cope with heavy loads as the clock hands are stepped forwards each half minute. They must also act as brakes on the momentum of the heavy clock hands at the end of each sudden step forwards.

The electromagnet can be seen fixed at the bottom of the movement on a sturdy bracket. This bracket completes the magnetic circuit and acts as the electromagnet's keeper during each electrical impulse. Note the robust build of the entire slave movement and the care taken to prevent long term corrosion. The movement would be fitted behind its dial and then possibly forgotten for years unless something went wrong.

The view looking down from the top of the slave movement. With the coiled drive spring nearest the camera.

The ratchet toothed drive wheel can be seen below the reinforced backstop pawl.

Note the rubber gasket on the flange  to protect the movement from moisture when it is installed in its white, protective metal box.

The black plastic block with soldered wires attached is a rectifier. So my theory of an alternative power supply may be true.

Yet another view of the slave movement showing the ratchet toothed, drive wheel. Given an impulse every half minute the drive wheel will rotate once in one hour. [120/2 = 60 minutes.] The drive wheel shaft extends forwards, beyond the white metal case, to a squared arbor which holds the minute hand securely. The pivot for the backstop lever is well seen in the foreground. It is deliberately lowered on the movement backplate to ensure the correct geometry to avoid any chance of backlash or failure to lock in the teeth of the drive wheel. Any error in the movement or locking of the slave will result in the minute hand pointing incorrectly.

Here is the front plate of the turret slave movement with the protective metal box in place. The object sticking out of the box [at lower let] is a sprung plunger for advancing the movement in half minute steps. It presses the armature in as if an electrical timing impulse had activated it. The hands on the clock can then be rapidly advanced without affecting the rest of the timekeeping system. 

Note the massive, cylindrical bearing housing to support the heavy clock hands. Any weakness here could cause the hand shafts to sag. Possibly resulting in the hands contacting the face of the dial. Even if this did not stop the normal hand movement it might lead to an ugly scar on the clock dial. The cost of replacement or repair of the dial might be extremely high in an inaccessible situation. Remember that a large clock hand has considerable leverage. A minute amount of slop at the hub could lead to an inch of movement at the tip several feet away. Clock hands are usually counter-balanced to avoid them turning under their own weight.

Here is a close-up of the clock hand, fixing components. The large white boss and bronze cylinder both contain labyrinth seals to stop rain being driven inside the movement by the wind. The hour hand fits on the hour pipe seen just in front of the white boss. The hour pipe is driven by the 12:1 motionwork gearing inside the movement.

While the minute hand slides onto the squared shaft against the bronze cylindrical bush and is locked in place by the screws. The matching squares on the shaft and minute hand ensure no chance of slippage is ever possible. This minute shaft goes right back to the reinforced drive wheel inside the slave movement. The hour pipe acts as a sleeve bearing for the minute shaft and is itself supported by a sleeve bearing in the large white boss.

A clock hand on a public dial indicating the wrong time is far worse than useless. Many people's actions, even lives, could hang on the accurate time shown on the public clock dial. Catching connecting trains is a vital function of such clock dials at railway stations. If the dial is showing the wrong time the public won't know whether to walk leisurely to their platform. Perhaps even visit the platform café if they have time to kill. Or run flat out to catch their train by the skin of their teeth!

Remember that this slave movement came from the end of a long era when public clocks were far more important than now. In the past most people did not possess accurate watches. Nor other more modern devices which could give a really accurate time check. Every slave clock under the control of the master was as accurate as the master clock itself. Usually good to within a couple of seconds a week. Before quartz watches these time systems offered completely unprecedented accuracy to the general public. Only the speaking clock, provided by the telephone company, could match this timekeeping accuracy and had to be paid for each time it was used. It also had to be dialled on a public telephone and the customer then waited for the next spoken time signal and accurate beep. Church clocks and other public clock dials were often minutes adrift unless constantly monitored.  

The electrical details have been applied with Dymo tape labels. The electromagnet is separately marked as having a DC resistance  of 71.5 Ohms. This is a quite remarkably high figure compared with a normal [small] slave with a resistance of only a couple of Ohms. Such a high figure suggests a very large number of turns of copper wire to obtain a very strong magnetic pull during each very brief, electrical impulse from the master clock.

The movement is expected to operate on 24 Volts DC.

Yet again I am indebted to a fellow enthusiast for sending me these excellent images. I just hope that my use of them repays the kindness in providing them for free public access. Those who wish to share good quality images of Pulsynetic Waiting Train movements, or any other interesting or unusual impulse timekeeping system components, can find my email address at the top of the page.

Click on any image for an enlargement.


Gillett & Johnston Waiting Train installation.

One of my generous sources has sent me some more images. This time of a Gillet & Johnston installation which includes a fascinating Waiting Train turret clock movement.

These images offer a unique and vitally important record of a very rare timekeeping system. Gillet & Johnston are best known [renowned around the world] for their superb bell casting and high quality weight-driven turret clocks. The company still exists to offer turret clock repairs and modern timekeeping equipment.

Clock Makers, Clock Restorers and Bell Founders

Gillett & Johnston - Wikipedia, the free encyclopedia

Gent's and Synchronome must have seemed to dominate their dwindling market as weight driven turret clocks orders became harder to obtain. The previous funds for church clocks and bells from rich Victorian benefactors were probably no longer available after WWI's massive social upheaval.

G&J must have seen the  writing on the wall when Gents began to produce their compact and incredibly powerful WT electric turret clock movements. These went on to set numerous records for increased dial size in the early 20th Century.

So G&J came up with their own, unique electrical impulse master clock, slaves and WT designs.

G&J produced a quiet, and now very collectable, master clock of entirely their own design. Relatively few must have been made because they only rarely come come up for auction and usually fetch a very good price by ordinary Gents and Synchronome standards.

These images alongside show an early, G&J master clock. The attractive mouldings on the top and bottom of a master clock case are usually an indicator of an earlier model. The movement design is elegant and relatively complex for a British master clock. Going through several design iterations over time. Note that the slave unit behind its pilot dial has been installed at 90 degrees anticlockwise to its normal position. It is amazing that it still functions as the time indicator! 

The movement uses a swinging armature to reset the gravity arm so that no noisy contact takes place. Spring blades are used to further damp any noise produced by the mechanism. It even has an air damper cylinder to soften the resetting of the gravity arm.

It uses a 15 tooth ratchet wheel and gathering pawl like most other British master clocks. A single electromagnet is arranged at the bottom of the movement backplate. Padded stop screws are provided to set certain movement limits. The gravity arm has a roller which runs down an impulse ramp on the one second pendulum at half minute intervals. The gravity arm is dropped onto the ramp by a trip vane unlatched by the count wheel. A long wire and D-shaped jewel draw the count wheel around one tooth at a time on every swing to the right. So that the count wheel rotates once in half a minute [30 seconds.]

 Unlike Gents, G&J seems to have made a different WT for each installation. Or so it seems. I haven't seen two the same in the [only] several examples of which I have obtained images. Anybody out there with a Gillet & Johnston electric turret/tower clock in their charge is very welcome to add more images to the very meagre collection in the public domain which I have obtained so far.

These three images are all I have so far of this particular G&J, WT, turret clock movement. The original images were very dark as flash was not used for the photography. The WT movement was obviously still running because the slow exposure has not caught the bob movement sharply. Flash would have frozen the bob in its swing and helped to stop the camera shake visible in the images here. That said, any images, at all, of a movement so rare as a G&J WT are well worth having. I have done my humble best to lighten and sharpen these images using PhotoFiltre.

G&J has obviously used their own metal casting facilities to produce another very solid baseplate for its own unique WT design. The bob is massive and [very unusually] the cylinder is arranged horizontally so that it can swing in the oval cutaway provided in the main plate. This makes for a very compact movement. As does the shortness of the pendulum. Note that this is a working clock and not a perfectly restored example from a private collection. Lots of oil and a little rust are very typical of working turret clocks hidden out of public sight for 100 years!

Working down from the top, the first thing we notice is the use of bearing instead of a conventional spring blade to support the pendulum. The same, robust, construction feature was used on the Gents' Pulsynetic WTs.

At top right is a small electromagnet which we can safely assume is related to the Waiting Train mechanism. The armature is in contact with an L-shaped lever on its right. 

The horizontal, main drive shaft is driven by a wormwheel and worm. The worm is mounted on the same shaft [arbor] as the gathering wheel. The gathering, or count wheel, is pulled round a tooth at a time by the gathering pawl. A backstop pawl hangs at the left of the gathering wheel to prevent backwards rotation. I believe the wheel is rotated anticlockwise by the bifurcated gathering pawl.

Unfortunately none of the images is quite clear enough to be absolutely sure of the WT mechanism's actual function. If it follows Gents' practice then the gathering pawl will be briefly lifted out of the teeth of the count wheel by a pin on the count wheel where it is latched. The pawl is then allowed to drop [by a small electromagnet] to its normal [active] position to gather teeth once again. The electromagnet will be activated by the half minute, timekeeping pulse from the master clock.

I think it is safe to assume the following: The electromagnet's armature is horizontal and seems to be hinged on the left. A right-angled L-shaped lever is a two position latch hinged at its 'elbow.' As the count wheel rotates, a pin lifts the L-shaped arm and thence the gathering pallet. The armature will now be free to drop out of the deep notch by gravity. The armature tip will then lock the L-shaped arm safely in a raised position just below the [normal] latching notch. The gathering pawl will slide ineffectively back and forth, for a few brief moments, clear of the count wheel teeth.

Then the electromagnet gets its half-minute electrical impulse from the master clock and attracts the armature. Allowing the L-shaped lever to drop [clockwise due to gravity] so that the armature re-latches the L-shaped arm by the deep notch in its normal position and clear of the gathering pawl. The gathering pawl can now continue to gather teeth to drive the hands on the clock dials. The armature will be raised to its normal position against its electromagnet's core. 

It is the precise timing of the armature's release of the [raised] L-shaped lever [allowing the gathering pawl to drop into the wheel teeth] which resets the timekeeping to the master clock's own standard at every half minute. The WT must slavishly follow the accurate timekeeping of the precision master clock.

A Waiting Train movement is not a true clock. It is a rather complex slave with its own driving power for the clock hands but has no timekeeping ability of its own. Take away the master clock's electrical impulse and the WT [turret slave] will gain very rapidly indeed. In fact it must always get to the half minute a little too soon to allow itself to be paused by its own WT mechanism. It is the brief pause in the drive to the clock hands which gives the "Waiting Train" mechanism its name and ensures its remarkably accurate timekeeping ability. 

On the left end of the main horizontal shaft [arbor] are the first bevel gears of the lead-off work to the distant dials. A second bevel gear turns the minute hand drive vertically. A typical universal-expansion joint takes up the vertical drive to allow for movement in the building's structure.

The main shaft is supported by sturdy cast brackets. As are the wormwheel and its worm. All very obvious from the images so far.

Well below the horizontal drive shaft is a set of electrical contacts. Presumably they are operated by a Hipp Toggle and V-block mechanism. The exact detail is rather hard to see in these images but the typical Hipp toggle and block may be hidden behind the pendulum rod. The actual contacts seem to be on the left of the two horizontal contact rods. A Hipp switch system allows the pendulum to swing freely until its arc falls below a predetermined limit. The Hipp Toggle drops into the V-block and the contacts are closed. The pendulum is then given a strong push and the pendulum regains its lost arc.

The problem now is deciding how the pendulum is pushed. The top image shows what appears to be an electromagnet  coil just below the bob. It is quite possible that G&J decided to use this classic and well proven method of maintaining a pendulum's swing. This same arrangement had been used for domestic and precision electric clocks since Hipp first presented his ingenious Toggle and V-block back in 1843.

I believe the two sturdy horizontal crossbars just above the swinging bob are there to catch the pendulum if the pendulum support should fail. Or perhaps to limit its maximum swing? 

Here we see the vertical lead-off rod emerging from the WT movement below to meet the crown-wheel cluster of bevel gears. Another expansion-universal joint allows for thermal expansion of the lead-off rod. The bevel gear cluster is strongly supported by am open, timber framework. Three further bevel gears lead off from the larger crown bevel gear to the exposed skeleton dials. All perfectly standard practice in turret clocks of all types and ages.

A close-up of the typically, very high quality bevel gear cluster produced by master turret clock makers. Note the sturdy, cast, hanging bracket. Each lead off rod to the dials has its own expansion-universal joints. The bracket must support not only all the bevel gears but all lead off rods as well. Including the vertical rod rising from the WT movement on a floor somewhere down below.

Here we see the high quality 12:1 dial motionwork and one heavy hand counterbalance. Each dial will be so equipped. As they will also have yet another expansion-universal joint. Not only are the lead-off rods quite long but temperatures in open bell and clock towers can soar in summer and plunge in winter. As the rods contract and grow in length, with changing temperature, these joints protect the clock hand drive system from binding and potentially damaging end-loads. They also allow for a degree of  misalignment due to changes in the building's structure with temperature, wind, settlement and humidity. The clamping screw on the joint can allow an individual change in hand setting on a dial after maintenance.

Here is a Gillet & Johnston bell dated 1922. Would it be a wild guess to assume that the entire G&J clock installation matches the date on the bell? The bell is struck electromagnetically by a large hammer driven by a powerful electromagnet in the box in the foreground.

Click on any image for an enlargement.