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Quartz watches and their forebears

Before we get into the nitty-gritty of Quartz Watches and the exactitudes of their functions, let’s cast a look back over a few of those failed antecedents alluded to previously.

In the days before the ‘discovery’ of quartz’s useful properties, horologists the world over attempted to harness the powers of electricity in watchmaking. The attraction was simple: electricity could provide a constant power source, unlike the variable tension delivered by a spring. Not even an automatic watch could pretend to contend with the possible uniformity of electric power, and so watchmakers, at first, did the obvious: they ripped out the barrel and replaced it with a battery, resulting in a short-lived generation of watches known as Motor Balance watches or, more simply, Electronic Watches.

Electronic watches, the Dynatron for example, are technically more accurate due to the consistency of the power provided to the mechanical balance by the battery (as opposed to the mainspring, which winds down and provides less and less power over time), but given that the time-keeping element of an electronic watch is still a mechanical balance, the difference in time-keeping is negligible.

A later, and somewhat more fondly remembered venture, resulted in Tuning Fork Watches. The Tuning Fork operated in a theoretically similar way to quartz, using the regular vibrations of a physical medium (in this case the fork as opposed to the quartz crystal) to ‘count’ the time.

Tuning fork watches, the Accutron, for example, are slightly more accurate due to the higher operating frequency.

So what is a Quartz Watch? A Quartz Watch is so named because of the sliver of genuine quartz crystal that, remarkably, plays the same role as the hairspring would in a mechanical watch. When a quartz crystal is properly cut (normally in the shape of a tuning fork) and mounted, it can be made to distort in an electric field by applying a voltage to an electrode near or on the crystal, distorting the crystal. This property is known as piezoelectricity. When the field is removed, the quartz will generate an electric field as it returns to its previous shape, and this can generate a voltage. The result is that a quartz crystal behaves like a circuit composed of an inductor, capacitor and resistor, with a precise resonant frequency.

This frequency (32,768 Hz) is equal to 2 to the power of 15 cycles per second. The frequency is ideal due to the fact that it can be stepped down cleanly to allow the wheels in the watch to easily translate that impulse into one tick per second. Some quartz watches do not have a seconds hand and thus do not need to tick every second. This enables the mechanical element of the quartz movement to operate less frequently, which in turn reduces the drain on the battery resulting in a longer lifespan.

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In Safe Hands – the Escapement in Focus

You remember how I mentioned that the impulse jewel extends downwards from beneath the balance wheel? Well that is true, but it is actually attached to small stepped, cylinder known as the safety roller, which is affixed to the balance staff beneath the balance wheel.

The Roller is a single piece of metal, but has two parts, or ‘areas’. The first is the table, which is a wide, flat bit that presses up against the shelf of the balance staff to ensure its correct placement in the watch, and the other part is the can, which is a narrower, taller piece that would be perfectly cylindrical were it not for a crescent moon shaped recess cut out of one side.

The impulse Jewel is friction fitted (or sometimes glued) to the table and extends downwards in this crescent-shaped recess, which we refer to as the notch OR the passing hollow (I prefer the latter as this avoids confusion with the notch in the horns of the pallet fork).

The passing hollow/notch is very important to the safe and consistent functionality of the escapement. Without it, the escapement could mislock and jam up, stopping the watch completely.

Thanks to its influence, combined with that of the guard pin (a thin, pointed piece of metal attached to the underside of the pallet fork’s horns) the escapement can operate without fear of mislocking.

Here’s how:

The purpose of the passing hollow/notch, is to allow the guard pin to pass from one side to the other during the moment of impulse (also known as the lift).

An unwanted phenomenon known as OVER BANKING can be prevented by the guard pin in conjunction with the safety roller during the supplementary arc, and the extremities of the fork (horns) when the guard pin is adjacent to the passing hollow of the safety roller.

Horn shake is the distance travelled when the lever moves accidentally from its position against a banking pin, to the point where the horn comes into contact with the impulse pin. This forms part of the safety action when the impulse jewel is about to enter the notch of the lever. Horn shake should be approximately half of total lock.

If horn shake is excessive then the escapement could be unsafe. The escapement could unlock at the critical time when the impulse jewel is about to enter the notch should the watch receive a shock at this point.

If the horn shake is excessive, the banking pins should be closed on a watch with adjustable banking pins. On a watch with fixed banking, the pallet bridge should be checked and, if necessary, replaced. In exceptional cases, the lever itself may be worn on the sides and might need replacing to correct the problem.

The Horn shake must be greater than the guard pin shake so that the impulse jewel does not hit the fork as it is trying to enter the notch.

Some watches have adjustable banking pins, responsible for restricting the LATERAL MOVEMENT OF THE PALLET LEVER. Most modern watches have fixed banking, which is part of a pallet bridge. These can be adjusted, but it is a risky job as it requires the watchmaker to physically and permanently alter the piece in question. To increase banking the pallet bridge can be filed away, and to reduce it, the underside of the pallet bridge can be peened with a peening hammer so that the metal is stretched and flared to close the gap within which the pallet lever can travel. Of course, this modified pallet bridge will almost certainly need some further finishing to make smooth and even the fixed banking. It’s a tough and tricky process and shouldn’t be attempted by anyone without significant skill or experience and, preferable, an electroplating machine that can be used to cover up the horrible mess you’ll no doubt make of the pallet bridge’s original aesthetics.

These are the steps, listed in the correct order, that one should follow in order to adjust an escapement with banking pins.
1. Division: of escape wheel/pallets and balance/safety roller.
2. Hornshake: can be adjusted by moving banking pins. Should be equal on both sides.
3. Guard pin: can be shortened or lengthened, stoned It must be less than Hornshake.
4. Depth of lock: can be adjusted by moving the pallet stones with consideration to the run to banking. The lock and run to banking should be equal on both sides.
5. Safety action

The draw is the angle of the pallet stones that encourages the escape wheel tooth to slide down the locking face when under impulse of the mainspring until the lever of the pallet makes contact with the banking pin and is held clear of the oscillator/balance so that the fork and notch of the pallet are positioned correctly to receive the impulse jewel. This prevents mislocking. This is achieved by the angle of the locking face of the pallet from the centre line of the escape wheel, normally 14 degrees (13-16 degrees).

The clearance angle the pallet travels after impulse, caused by the angle of the pallet stone locking face, to ensure the correct position of the fork to receive the impulse jewel.

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Nice teeth and classic curves

The teeth on wheels in watches may look pretty bog-standard, but they are actually a different type of tooth than the ones you would find on bigger machines that use similar-looking cogs, such as car engines and the like.

If you made the wheels you found in a car engine the size of watch wheels, the teeth would instantly snap off due to the incredible stress on the material. It seems a funny thing to consider – logic might lead you to believe that force is relative to size and that scaling down the wheel, would also scale down the force, but that isn’t the case.

As with the straight and conical pivots, car engine wheels use their form of teeth because, at that size, they can get away with it, but for watchmaking, the teeth need to be a modified EPICYCLODIC curve.

So what’s an epicyclodic curve? Put quite simply, it is the trace of a point on the outside of a circle as that circle rolls around the outside of another circle.

You might hear the following terms, but do not confuse them with EPICYCLODIC.

Cyclodic curve: the trace of a point on the outside of a circle as that circle rolls along a flat and straight line.

Hypocyclodic curve: the trace of a point on the outside of a circle as that circle rolls around the inside of another circle.

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Chronograph Functions in Detail

As defined previously, a chronograph is a watch that tells the time and records elapsed time on demand.

It’s basically a watch with a stopwatch attached to it. To make such a thing possible, a lot of parts, specially tailored to keep friction to a minimum, are necessary.

I know I keep banging on about friction, but it really is the main problem horologists must overcome if their produce is going to function as well as it must to maintain the reputation of our industry.

We all understand that friction is a big enough problem in a regular watch. In a chronograph, it is out of this world. Imagine bolting a second unit, full of teeth, leaves and springs, onto a watch and expecting it to drive itself and the additional unit. It is asking a lot, and if we as watchmakers expect that poor little mechanism to perform, the least we can do is ease its burden as much as possible.

So, familiarise yourself with the following parts. They are commonly found in a chronograph. Explanations of those parts which are not self-explanatory will follow, but for now, know that when you see any of the below, we’re talking chronographs.

The parts of a chronograph:

1. Intermediate Chronograph Lever Spring
2. Eccentric for Chronograph Lever
3. Drive Wheel
4. Clutch wheel
5. Heart Cam for Seconds
6. Chronograph Wheel (centre)
7. Minute Jumper Spring
8. Minute Counter Jumper
9. Heart Cam for Minutes
10. Zero Pusher Piece
11. Rocking Lever Spring
12. Hammers
13. Brake Lever
14. Brake Lever Spring
15. Main operating Lever
16. Rocking Lever
17. Lower Cam
18. Intermediate Operating Lever
19. Upper Cam
20. Zero hammer Spring
21. Eccentric stop pin for Intermediate Chronograph Bridge
22. Cam Jumper Spring
23. Minute Counter Wheel
24. Intermediate Minute Counter Wheel

Most every chronograph will have a seconds register. Of that, you can be relatively sure. The next surest inclusion on the dial of a chronograph, will be a minutes register. After that you’d expect to find an hour counter (we’ll get to the operation of those shortly), but sometimes they are replaced with something else or omitted completely.

But for now let’s just concern ourselves with the parts and operations of those parts that you will expect to find in the minute counter of a chronograph.

There are 7 main components to remember:

Chronograph wheel finger
Intermediate minute counter wheel
Minute counter wheel with Heart Cam and Minute counter hand (dial side)
Minute counter jumper
Minute counter jumper spring
Chronograph Bridge (and screw)
Chronograph Zero Hammers

The chronograph finger, which is mounted on the chronograph wheel, advances the intermediate minute wheel one tooth at a time, every revolution of the second hand, which in turn advances the minute counting wheel once a minute.

Normally the minute counter had 30 teeth and a hand to display the passing minute on the dial, which is held in position by the minute jumper and minute jumper spring, which applies the appropriate tension to ensure that the minute counter wheel advances only one minute each time. The chronograph bridge carries the bearings for the seconds and minute counting wheel. The zero hammers, in conjunction with the heart cam, return the counting hand to zero.

As well as the standard minute counter, which creeps into its new position over the last few seconds of the preceding minute, such a thing known as an Instantaneous Minute Counter exists.

Quite simply, the Instantaneous Minute Counter is a slightly more complex system that enables the minute hand to jump INSTANTANEOUSLY when the second hand ticks past 12. This is opposed to rolling counters that are geared up to creep constantly and the more common system that sees the minute hand move slightly before the second hand reaches 12 (these use a finger on the chronograph wheel, as you would ifnd in a standard ETA 861 calibre).

In place of the finger on the chronograph wheel is a snail on which rests a lever under the influence of a spring. Attached to the lever is a pawl or click.

The minute counting wheel has ratchet shaped teeth and is positioned by a conventional jumper.

The lever with the pawl is lifted by the snail and the click gathers one tooth on the minute recording wheel.

As the lever reaches the high point of the snail and falls to the lower part of the lever and pawl advances the minute counting wheel instantaneously.

Just like any good relationship, the proper functioning of any good chronograph is reliant on minimal friction and just the right amount of tension in all the right places.

Here are a couple of things to check for in regards to tension:

If insufficient tension is created in the friction spring, the second hand will judder when the chronograph is started due to the backlash in the teeth of the wheels.

If the amplitude of a chronograph falls drastically at each jump of the minute register, you should check the tension of the jumper spring for the minute counter.

If a chronograph mechanism is activated and the amplitude falls drastically, you should check the depth of the clutch wheel teeth and the chronograph wheel to ensure they mesh correctly (50% depth), and the tension of the chronograph wheel friction spring to ensure it is not pressing the chronograph wheel into the jewel.

Here’s another potential problem to watch out for:

If the minute counter of a Chronograph jumps 2 steps each time the second hand passes the 12 o’clock position, you need to check the depth of the penetration of the finger of the chronograph centre wheel and the intermediate counter wheel AND the position of the minute counter jumper.

The hour counter records timed hours (normally 12) and is usually driven from the barrel via a gear and friction device, the recording is stopped and started via a switch (the hour counter operating lever) that passes through the movement to connect with the chronograph column wheel. The hour recorder is zeroed by a separate hammer, which operates at the same time as the chronograph hammers.

Here is a list of the parts you can expect to find in a standard hour counter mechanism:

1. Hour counter operating lever
2. Intermediate hour counter operating lever
3. Hour counting brake lever
4. Hour counting brake spring
5. Pinion attached to barrel via friction spring
6. Hour counting wheel
7. Hour counting indicator hand
8. Hour counting heart cam
9. Hour counting zero hammers
10. Hour counter hammer spring
11. Hour counter bridge

The above eleven components can be said to ‘interact’ with the Hour Counter.

Everything in horology, much as it is in life, is bound by a simple equation: C:E.

That’s Cause and Effect, people. Never forget that. An action creates a reaction. In watchmaking, any movement of any piece will effect the operation of the watch. When it comes to the starting and stopping of the hour counter mechanism in a chronograph, it is most certainly the case. Please read the following carefully and slowly. Have a labelled diagram of a standard chronograph in front of you. Look at all the parts. Visualise their movement. Visualise the point at which they make contact with other parts. Get inside the watch.

Feel the action. Be part of the reaction.

Take a deep breath…

GO!

When the start/stop pusher is depressed, the main operating lever slides along the plate and, by way of the intermediate operating lever (held in place by the rocking lever and the rocking lever spring), engages with the lower level of the cam/column wheel, which clicks into a new position. The hour counting operating lever/yoke has a pin that extends through the plate to the dial side. When the hour counting operating lever/yoke is moved by the cam/column wheel, this pin engages with the switch on the dial side, which lifts the hour brake lever away from the hour counting wheel, which is driven directly by the drive pinion on the barrel. Thus, the hour counting mechanism begins operation.

The stop command works in much the same way, except the intermediate operating lever makes contact with a different part of the lower level cam, which allows the Cam Jumper Spring and hour counting operating lever/yoke to return to their original positions. Thus the hour counting operating lever/yoke disengages the switch from the hour counter wheel brake and the brake, given tension by the hour counter brake spring, snaps back into place and stops the chronograph.

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Isochronism and the escapement

The word isochronism is bandied around a lot when discussing the quality of high-end timepieces and deserves a solid definition so that it can be easily understood.

It comes from Greek and literally means ‘Same’ (Iso) ‘Time’ (Chronos). It relates to the consistency of a watch’s timekeeping in all tested positions of wear. This is largely controlled by the poise of the balance wheel and the flatness and centring of the hairspring.

There are several factors that can impair the isochronism of a watch. Eight such disturbances are:

Gravity
Friction
Regulating pins
Escapement
External Shock
Temperature
Out of poise balance/out of poise hairspring
Magnetism

So how does the escapement – the distribution organ of a mechanical watch – affect isochronism? The Swiss Lever escapement has an inherent loss. Impulse before the centre line (0 degrees) causes a gain. Impulse after the line of centres causes a loss. A disturbance before the line of centres causes a loss. A disturbance after the line of centres causes a gain.

Since the unlocking (a disturbance) occurs before the centre line, causing a loss, and the majority of the impulse occurs after the line of centres, a further loss is caused. Therefore the effect of the escapement interference causes a loss. As the lift angle is 52 degrees (in a standard watch), and becomes proportionally more influential as the amplitude decreases, the loss too becomes greater.

The lift angle is the angle of travel through which there is contact between the impulse jewel and the notch. It is classified as a disturbance and thus as the amplitude drops and the lift angle remains the same, it becomes a relatively longer and more influential disturbance.

So how do we define the isochronous error of a watch? To check the isochronism of a watch, you must test the watch in all five positions when fully wound, and then again when half wound (often 24 hours later). The readings are then totalled (separately) and an average rate is found. The difference between those rates is then referred to as the isochronous error. Here’s a theoretical example:

Test 1 (fully wound):

Dial up: +25
Dial down: +5
3 o’clock up: -5
6 o’clock up: +0
9 o’clock up: +5
Variation: 30/5=6

Test 2 (half wound):

Dial up: +20
Dial down: +10
3 o’clock up: -8
6 o’clock up: +0
9 o’clock up: +6

Variation: 28/5=5.6

In this case, the Isochronous error is 0.4

The mean daily rate would be 6+5.6/2=5.8

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