Home, 2006-04-21
For a nice animation go to http://www.clockwatch.de/ and look under Theory->Escapements->Detached->Lever(Swiss).
Also take a look at Walt Odet's articles: "THE ANCHOR ESCAPEMENT" http://www.timezone.com/library/horologium/horologium631673198118416858 and THE BALANCE WHEEL OF A WATCH http://www.timezone.com/library/horologium/horologium0013.
The overcoil hairspring was invented by Breguet to improve isochronism (accuracy in different positions) and positional performance. The overcoil allows the outer end of the spring to be fixed close to the center of the spring, thus the mass of the spring is constant as it coils and uncoils (how is this related to the "concentric" movement of the spring? ).
Without an overcoiling hairspring, and with a regulator, it is necessary to bend the outmost part of the hairspring to make it have the same distance to the center of the balance (this is called a "dog bend").
As far as I understand, as new materials has been introduced, the importance of the overcoil has been reduced, but it is still necessary to reach exceptional positional performance (this is a matter of discussion).
One reason the use of overcoils has been reduced, is that they are costly to produce, another reason is the increased height of the movement: the use of a spring with overcoil can increase the height with more than 1 mm.
(The Breguet overcoil can be combined with a regulation device.)
NickDownes writes the following (http://www.network54.com/Forum/169624/thread/1132759341/Breguet+overcoil+-):
An ideal oscillator requires an ideal restoring force. The restoring force in a balance assembly is provided by the balance spring. An ideal spring would obey Hooke's laws, which state that (within the elastic limit) the force is proportional to the displacement. So, if the balance spring obeyed Hooke's laws, the force required to wind it up would be proportional to the rotation of the balance staff, and the restoring force applied when it unwound would be proportional to the rotation of the balance staff. As the balance expands and contracts, the fact that it is attached to fixed points means that supplementary forces are generated in the outer and inner portions of the spring, which make it deviate from Hooke's law and so make a non-ideal as a maintaining force for the balance. In a nut-shell, the end-result of the fixed inner and outer points is that the restoring force isn't constant for all amplitudes. Philippe Woodward (the horlogical mathematician) has demonstrated that this theoretically, and so shown that the balance spring with fixed attachment points is inherently anisochronous. The visual side-effect of this is that the effective center of the oscillating spring moves away from the balance staff due, and the balance is said to not "breath" correctly. I like to think of the overcoils as "isolators" that allow the majority of the spring (say 12 out of 14 turns) to oscillate as ideally as possible, with the effective center of the spring as close to the balance staff as possible. Simplistically, I think of a balance spring with 14 turns and overcoils as a balance spring with 12 turns and two flexible attachment points consisting of the two overcoils. The isolators allow the 12 turns to behave more closely to Hooke's law, and so the owverall spring is more isochronous. This isn't a perfect analysis, but it helps understand it. So why do modern balance springs not have overcoils? My understanding is that the ultimate objective of the overcoil is not to make the spring "breath" better (as old-timers would have said), but to get the spring to behave as closely as possible to Hooke's law, so ensuring that the restoring force is as constant as possible for all amplitudes. If this can be obtained using other methods, there's no need for an overcoil (which is expensive to manufacture and adds height to the movement). Modern balance springs use different techniques to obtain a similar effect, for example the dog-leg, and selective heat treatment of the outer portions of the coil. The inner attachment with a glued or similar attachment method behaves very differently to an old-fashioned attachement with a 90deg bend to the collet. These perhaps don't totally replace an overcoil, but they go a long way to doing so. Also, a modern spring is much smaller and lighter than an old blued-steel spring, and it has a different modulus of elasticity, so it is less susceptible to the "interference" due to fixed attachment points. I've seen hints and oblique references to this point in several books and reviews, but no hard info. (Woodward's analysis is based on a blued-steel spring, and it would be interesting to see the same exercise done for a modern spring to see if the magnitude of displacement of the effective center is the same.)
A regulator provides an easy way to adjust the balance (???) by changing the effective length of the spring, but the regulation works by distorting the shape of the spring. The distortion affects the accuracy of the balance in different ways depending on the position, which makes positional adjustment more difficult. Also, the position of the regulater can change over time or because of shocks (in effect requiring re-adjustments).
The freesprung balance is a balance without a regulator connected to the hair spring. This makes it possible to have an almost round hairspring. A freesprung balance is regulated by adjusting the inertia of the balance, this is done by screws (like Rolex' micro stella or special weights (like Patek's Gyromax, also used by many others including AP and VC)). The freesprung balance is considered to be the optimal solution, but it requires more work or complicated tools to regulate a free sprung balance. The question is how big difference it does make in reality?
ei8htohms on winding efficiency: http://www.network54.com/Forum/169624/thread/1132919395/An+old+post+from+ei8htohms+on+winding+efficiency+...
With cam and lever set movments, your finger pushes on the levers that engage the gears.
With a column wheel, your finger pushes on the column wheel. When the columns get out of the way, a spring pushes the gears in place with a constant, predictable force and speed.
I think domed crystals look a lot better than flat crystals, and they do not look as bad as flat crystals when attacked by fingerprints etc. Flat saphire seems to be the worst in terms of looks.
Sapphire is scratch resistant but expensive, an it will probably get scratches eventually. Mineral is looks better than sapphire, but is easily scratched. Both sapphire and mineral can shatter into sharp broken pieces of glass, sapphire will break into really small pieces (I have smashed a sapphire while wearing it and cannot recommend it).
Acrylic looks great and is the cheapest. It will get scratched fast, but small scratches can easily be polished away.
The five positions are:
ei8htohms writes (http://www.network54.com/Forum/169624/thread/1057200941/):
The best books I know of to learn about watches from a watchmaking
perspective are: Donald DeCarle's ("Practical Watch Repairing",
"Practical Watch Adjusting" and "Complicated Watches and Their Repair"
especially, but all of his books are good), Henry Fried's ("The
Watchmaker's Manual", "Bench Practices for Watch and Clockmakers" and
his book on escapements) and George Daniel's "Watchmaking"
(indispensible, but generally a more theoretical and/or impractical
approach than many people want: fabricating everything from
scratch). All these books are excellent and there are many more that
have great information. Francois Lecoultre's "Guide to Complicated
Watches" is also excellent.
Collecting older watchmaking books can be very amusing and the various
tricks and weird historical info you can pick up is a lot of fun
too. Many of them are hard to find so that can be half the fun also.
If you're interested in more modern stuff and a collector's angle more
than a watchmaker's angle, "Wristwatches, Armbanduhren,
Montres-bracelets" by Gisbert Brunner and Christian Pfeiffer-Belli is
excellent. Histories or most major brands (and some nearly forgotten
ones) with lots of pictures mostly but also has short articles on
automatics, chronographs, perpetual calendars, etc. A very good
general text and typically fiarly inexpensive for how substantial it
is. As the title might indicate, it's in English, German and French
and that makes it a little unwieldy but fun to see how different words
translate as well.
[...]http://forums.timezone.com/index.php?t=msg&th=466886&start=0&rid=10240
A watch is considered to be in beat when the balance takes equal times to swing clockwise and counterclockwise. Elgin watches were in beat when they left the factory. Since that time, most of them have been repaired numerous times and have had several balance staffs replaced. Each time the staff is replaced, the beat must be readjusted. The accuracy of setting the beat is dependent upon the watchmaker's skill and/or his attention to detail. The beat is adjusted by turning the hairsping collet. The watch is visually in beat when the pallet fork lies directly upon the line between the escape wheel arbor and the balance staff. Although visibly in beat, the collet may require a small further adjustment to have the watch acoustically in beat when measured with a watch rate recorder. The rate recorder listens for the sound of the roller jewel striking the pallet fork during the unlocking of the escapement. When the time interval between these sounds is the same, the watch is in beat. Generally, a watch visibly in beat will perform adequately, especially if one is working with vintage or antique pieces. (Jake B.) [...] Most current production watches will not encounter this difficulty because the beat is adjusted by rotating the hairspring stud support. In fact, the collets of these watches are not split and cannot be turned on the stall. These watches can be very accurately put into beat with acoustic watch rate recorders because the stud is easily and safely moved. (Jake B.)
(I think I got this from Timezone, I have always wondered why it should not be possible to do exactly this)
Small scratches can be polished out using jewler's rouge.
A watch considered WR can be put into hot water (maybe 50 degrees C), this will expand the air inside the watch and bubbles will escape if it has leaks. Water should not enter the watch as the ressure is higher inside the watch.
Started in 1881 by Louis Audemars and Edward Auguste Piguet. Created the smallest minute repeater in 1891 (18mm), in 1946 the thinnest watch at 1.64mm, in 1967 the thinnest automatic, in 1978 the thinnest perputal calender, and in 1986 the first and smallest tourbillon.
Still belongs to the two families. Have owned 40% of JLC (until Richemont bought JLC). AP has used calibers from JLC and Lemania (2310).
Audemars Piguet Photo Gallery and Reference Page http://www.network54.com/Forum/200844
Started in 1833 by Charles A. LeCoultre who made instruments, including a tool to measure precision down to 1/1000mm. In 1925 joined by Edmond Jaeger, who helped produce the first watch finished in 1929.
Calibers for AP, Patek Philippe, and Vacheron Constantin. Now owned by Richemont.
Started in 1832(?) as Patek, Czepak & Co. In 1844 Jean A. Philippe designs and presents the first watch caliber to be wound without a key. Phillipe joined the company that changed name to Patek Phillipe in 1851. Did their first wrist watch in 1868. Made some super complicated pocket watches in the 1920'es.
Dalai Lama repairs watches:
International Earth Rotation and Reference Systems Service (IERS): http://www.iers.org/
John Harrison and the Longitude problem: http://www.nmm.ac.uk/site/request/setTemplate:singlecontent/contentTypeA/conWebDoc/contentId/355
LeapSecond.com, A web site dedicated to precise Time & Frequency ...one man's quest for the most accurate clock: http://www.leapsecond.com/
Long now foundation (10,000 year clock): http://longnow.org/
On the Units of Time: http://www.timezone.com/library/tmachine/tmachine0004
Why the World's Clocks Are Wrong: http://www.wired.com/wired/archive/11.11/start.html?pg=5
WORLD MAP OF TIME ZONES: http://www.worldtimezone.com/
Written by SteveG in http://www.network54.com/Forum/thread?forumid=169624&messageid=1123264282:
The term "chronometer" began in 1715 with English watchmaker Jeremy Thacker, for a sea watch using a verge movement. John Arnold extended the use to pocketwatches in 1782 for those having spring or pivoted detent escapements. When the Swiss designed lever escapements with equivalent or better precision, the term came to indicate the high precision, rather than the escapement type.
A grand complication contains one of each of:
(see http://www.europastar.com/europastar/watch_tech/nicolet7.jsp)
French measure, 1 line = 2.2558 mm.
Example: the 11.5 line eta 2824 is around 26mm.
A watch rated to be Xm water resistant, is resistant to 1 atm + X/10 bar of absolute pressure. Typically, if the resistance is measured in bar, it accounts only for the additional pressure the watch can withstand.
For water rho is around 1000 kg/m^3. So if I move my arm with 36 km/h = 10 m/s, then:
Shoulderless bars are springloaded bars that cannot be removed without cutting them.
Swiss quality depends on the amount of work actually carried out on a watch in Switzerland. It therefore requires that the assembly work on the movement (the motor of the watch) and on the watch itself (fitting the movement with the dial, hands and the various parts of the case) should be carried out in Switzerland, along with the final testing of the movement. It also requires that at least 50% of the components of the movement should be manufactured in Switzerland. http://www.fhs.ch/en/swissm.php