Freesprung balance, detached lever: defined, differentiated

Modersohn

Registered User
Nov 15, 2003
286
0
0
Hi, I was wondering how "freesprung" is defined as regards a balance, and how it interacts with the balance's being a detached or detached lever (is there another type of detachment?) balance.

Also, how does a vibrating stud--as opposed to a Breguet overcoil (? if I have that right ?) affect a balance;

and how does that interrelate to the idea of its being freesprung?

thanks, Jessica
 

Modersohn

Registered User
Nov 15, 2003
286
0
0
Hi, I was wondering how "freesprung" is defined as regards a balance, and how it interacts with the balance's being a detached or detached lever (is there another type of detachment?) balance.

Also, how does a vibrating stud--as opposed to a Breguet overcoil (? if I have that right ?) affect a balance;

and how does that interrelate to the idea of its being freesprung?

thanks, Jessica
 

doug sinclair

Registered User
Aug 27, 2000
14,364
62
48
Calgary, Alberta
Country
Region
Jessica,

A watch that has the usual regulator is equipped with an adjustable index with two curb pins on one end. The two curb pins "straddle" the outer coil of the hairspring. As the regulator is moved across the scale at one end, the curb pins move around the outer coil of the hairspring at the other end of the regulator. As this happens, the effective length of the hairspring is either lengthened (to slow the watch down), or shortened (to speed the watch up). The effective length of the hairspring is that portion of the spring from the curb pins on the regulator to the centre collet on the balance staff. A "freesprung" balance has a system of regulation that doesn't use curb pins. There is usually a set of regulating screws positioned radially around the rim of the balance wheel which can be turned outwards to slow the watch down, on inwards to speed the watch up.

The two most widely recognized forms of detatched lever escapement are the usual lever escapement, and the pivoted or sprung detent escapement such as the Earnshaw escapement. To put it briefly, the less contact the escapement has with the balance wheel during its rotation, the better. The detached escapement is the opposite of the "frictional rest" escapement (e. g. cylinder escapement). For further elucidation on these escapements, it would be best if you were to read about them for maximum understanding.

The vibrating stud is a form of temperature compensation which makes the temperature adjustment at the regulator curb pins rather than on the balance wheel. This system causes the distance between the curb pins to increase (as the watch cools), or decrease (as the watch warms up), thereby stabilizing the rate. This system is one of the early temperature compensating systems.

The Breguet overcoil hairspring can be found with curb pin regulator, a freesprung balance wheel, a detatched lever escapement (lever or detent type). I doubt that the Breguet hairspring has been used very often on watches with frictional rest escapement. As to whether it has ever been used with a vibrating stud, I wouldn't care to say.
 

Modersohn

Registered User
Nov 15, 2003
286
0
0
Thanks, Doug, that's very helpful. Could you recommend a good book?

I understand what you've written, it's extremely clear. Often, though, I don't quite understand descriptions of this material.

By the way, are there any models of watch you would identif, or chronological points, at which the innovations were made which meant that one of these methods replaced another?

Jessica

PS will look for Watch Escapement by Fried; thanks Leghorn.
 

doug sinclair

Registered User
Aug 27, 2000
14,364
62
48
Calgary, Alberta
Country
Region
Jessica,

I too would welcome suggestions as to books that could answer each and every question about horology that could be asked. I just checked several of my references for the definition of freesprung. And none of them defined it. I know if I kept searching the volumes in my ever growing library, I'd eventually find it defined. For a good source of information on escapements, check out the Shugart, Engel & Gilberts guides. As to a chronology outlining the great innovations in horology, again, information is all over the place. One of the most important aspects of the collecting I've done over the years is the books I've bought. An expert (myself not included) doesn't need to know everything, as long as he (she) knows where to find what he (she) needs to know.
 

SSWood

Registered User
Sep 27, 2004
19
0
1
I too , have problems understanding how some of the escapements work, but have found the animations at the following site of immense value : www.clockwatch.de
.. They can be found by clicking on "Theory", on the left hand menu.

Steve
 
D

D.H. Grace

Jessica,

Free springing has a few major advantages that haven't been mentioned here. Since the 18th century, watchmakers have realized that isochronism, or equal time for swings, was a problem. Balances don't always swing the same distance with each vibration, owing to tiny changes in the impulse force, changing friction at the balance pivots, changing viscosity of the oils, etc. Getting the long arcs and the short arcs to take exactly the same amount of time is difficult, and is partly dependent on the length of the spring. Using a regulator with curb pins to effectively shorten or lengthen the spring to regulate the balance's overall oscillation rate means that the spring will no longer be isochronous. Thus, the watch will not keep as steady a rate over the long haul as the oils at the pivots oxidize, etc.

To the best of my knowledge, vibrating studs don't have anything to do with temperature compensation. Doug might have been thinking of compensation curbs, which work exactly as he described. The stud is the point where the balance spring is attached to the watch. It is usually rock solid, both pinned and screwed to the balance cock so that the spring itself is the only thing that flexes. With a fixed stud, impulse is delivered to the balance via something whacking the staff (usually either a lever or the escape wheel). Since the impulse whack is disruptive to the system, most escapements are designed to deliver it as close to the center of vibration as possible, when it will be least harmful. The transfer of energy is usually far from perfect. I believe with vibrating studs, the stud moves slightly to deliver impulse through the balance spring itself. They are not common, and didn't generally improve the quality of the timekeeping, but they definitely solved the impulse problem in an innovative way.

Breguet overcoils take the last loop or coil of the balance spring, lift it above the plane of the other coils, and give it a different curve to bring it across the top of the spring. The reason for the overcoil is to make the spring isochronous by changing its geometry. As the balance rotates, the spring reaches two extremes at either end of the oscillation--fully wound up, or fully unwound. At these extremes, an ordinary coiled spring tends to push or pull sideways at the points where it is fixed--the stud and the balance staff. That puts side pressure on the balance pivots, changes the friction in the system, which, in turn, messes up the timekeeping by making some oscillations take longer than others. With the right geometry, an overcoil can keep the spring's center of gravity constant and prevent the side pressure. For several generations after Breguet started using overcoils, watchmakers found the correct geometries by trial and error. The math and theory didn't catch up with practice until the second half of the 19th century, when a French mine engineer came up with a mathematical formula to explain the geometrical requirements for the curve.

I hope these explanations make sense.

Regards,

David Grace
 

Tom McIntyre

Technical Admin
Staff member
NAWCC Star Fellow
NAWCC Ruby Member
Sponsor
Aug 24, 2000
83,843
1,870
113
84
Boston
awco.org
Country
Region
Actually, I think David was describing one of the types escapement that generally are called Constant Force although that name is subject to wide debate also.

The Vibrating Hairspring Stud was invented by Charles T. Fogg at Waltham as a means of compromise between freesprung balances and the need to regulate.

In Fogg's vibrator, there is a pivoted arm to which the hairspring is attached. The arm in the standard form is pivoted at the back of the balance cock and passes between a cam and a fixed stud before receiving the attachment of the hairspring. As the balance rotates, the vibrating stud swings toward and away from the balance cock with the expansion and contraction of the hairspring. By adjusting the cam, the amount of swing can be controlled and the effective length of the hairspring changed.

Here is a picture of the Vibrating Hairspring Stud.
29.jpg

In this picture the blue screw on top of the balance cock is the cam and the screw at the left is the backing stop. As you can see the hairsrping does have a breguet overcoil. (Click the picture to make it bigger.)

The English used a similar scheme where they extended the end of the hairspring and pinned it to the base of the balance cock instead of having the steel arm. It shows up most often on watches by Dent.
 

Dr. Jon

Moderator
NAWCC Member
Dec 14, 2001
6,343
758
113
New Hampshire
Country
Region
Jessica

Just to sumarize,

Vibrating hairspring stud was a Wlatham invention that has gotten soem attenton recently. Its a hybrid between freeesprung and regulator mean time adjustment.

From the mid 18th to late 19 century informed opinion was that the best timing performance required an an overcoil balance spring with no regulator pins.

High end English makers usually made their best lever watche freesprung as did Waltham in the Stone Mountain 72 and Elgin with their Father Time Torpedo Boat watches and the Edward Howard Watch.

Detent Chronometers and the highest class Englsih watches were freesprung. Final time adjustment was by fine tuning of the balance screws. Rolex and Patek Phillipe still do this and have since at least the 1950's on their wrist watches. The Omega co axial movement are also freesprung.

This theory took a bit of blow with the advent of observatory timing trial in which the best watches had conventional regulators.

A good book on what people thought in the 19th Century is David Glasgow's "Watch and Clock Making" which has been reprinted a few times so is reasonable.

No one has acutally written the tiem trials refuted this idea but if you check the 1905 Kew trail records on teh Elgin web site under non Elgin articles you will see that the fourth place finisher was a Patek Phillipe watch which beat a bunch of karrusels, tourbillons and freesprung watches.

It is also intersting that couple of Waltham Riverside maximu watches were in the trials. They came in toward teh bottom of the top 40 but they beat a lot Karrusels with and without freesprung levers.

Today the Freesprung watch carries a lot of prestige and has the advantage that its adjsutment is more robust than that of a regulator since very small perturbations can undo the fine adjustment in the regulator pins. (See the books by Walter Kleinlien on how to fine tune watches with reglator pin adjustment).



This is very high end performance and by my calculation any watch that got a Kew A rating woudl stay within better than 1 minute per year allowing for its established rate rate. With a high Kew SCore say 80 of better it might stay better than 15 sec/year.
 

Modersohn

Registered User
Nov 15, 2003
286
0
0
Thanks so much Dr. Jon, and Joe.

I'm looking for the Glasgow Book,and also will check the Elgin pages.

Just to recap, so I'm sure I understand:

freesprung balances are a way of coping with the problem isochronism, given the stress and disequilibrium created by the motion of the hairspring, which can not be absolutely regular.

Using a regulator, or curb pins mechanically lengthens or shortens the hairspring itself, so as to make the time of the arcs identical, by changing the length to suit the temperature or other conditions. However, while the overall motion of the balance will keep time, the motion of the hair spring is no longer isochronous,.

[I must admit I don't entirely understand this--except if the manipulation of the curb pins is too crude and the changes in temperature, etc, too frequent for the curb pins to be repeatedly attuned to each fluctuation--so therefore, the result may be within tolerable limits, but not internally caused to achieve by isochronicity naturally by the autonomous working of its design.]

Therefore the best, or most consistent, isochronism was thought to be made available by using an overcoil (to equalize the pressure--therefore distortion of equivalence) exerted on the hairspring by the momentum of the arcs, esp., at their extreme points).

The overcoil was supplemented by the mix of screws (or small metal rods) inserted into the balance wheel itself.

Was there,then, also a compensation balance, or the use of advanced temperature resistant materials, in the balance--siince isochronism is affected by changes in temperature, which are omnipresent.

The balance could then be adjusted--perhaps at intervals ?-- to assure that the disruptions of friction, congealing oil, etc, were also compensated for.

The Key Gardens test somewhat undermined the theory of the superiority of this method, by showing that watches with regulators could match, or surpass, freesprung balance mechanisms.

However, many high-end watches companies still prefer the use of overcoil and balance screws, and eschew the use of balance screws and curb pins.

Could I ask, though, what exactly are meantime pins?

I'm checking out that site of animated escapements and I may have a few really simplistic questions.

Again, thanks so much for these very detailed and (I hope) illuminating answers.

Jessica

PS I hope this is not impossible to understand; I also hope I understood your points.
 

Dr. Jon

Moderator
NAWCC Member
Dec 14, 2001
6,343
758
113
New Hampshire
Country
Region
Jessica


I am not familiar with "meantime pins" but most high end watches have mean time or "quarter" screws. These are at the arms and 90 degrees awayr from the arms, at the quarter positions on the balance. They have long threads compared to most of the screws on a balance.

We did not fully answer your question because the balances in freesprung watches are often special. They often have "wings" special shapes where the arm and rim meet. This is sometimes called a chronometer balance and allows the balance to be poised before any screws are added. This was thought to be especially useful. These balances are also used on high end regulator equipped watches too, but almost always on freesprung watches.

Rolex used special mean time screws. These had a star shaped head and worked with a special wrench which also had a special level on it calibrated in tiem increment adjustments. They still may do something and perhaps Doug Sinclair can comment. The Omega Co Axials use a specially shaped screw and tool to adjsut it.

Patek also has a special balance with weight sopen at one end that can turned to provide fine adjustment.

The theoretical argument against regulatos was that teh spring will usually have some freedom ebetween the pins. When it is not touching either pin its length is greater than when it touches. Changing this separation is one of the adjsutments used to tweak up the timing.

So far as I know all freesrung balances have at least a few screws or adjustable weights. Since most of these are wrist watches this strays a bit off this topic.

The theory that favored freesprung watches led makers to dislike and eliminate the compensation curb. This is a bi metallic strip that adjusts the effective pinning length of the spring. Now not only does teh length of the spring vary over its swing but the pined length varies with temperature. This limited the effectiveness of position adjustment. So far we are still with pocket watches.

The bimetallic compensation balance elimianted compensation curves making the balance adjustments better. It also had "middle temperature error" The balance changes its effect as the square of temperature while the spring varies as the first power so if you correct at two temperatures you still have a residual error, typically 2 seconds per day.

This led to many experimetns during th e19th and 20th centuries and was solved with temperature compensating materials, invar, elinvar, nivarox etc. Until about WWII these wroked Ok but were not quite as good as harened steel balances for position and isocronism. These are fine points. The best Kew rate for such a balance was about 85 compared to high 90's for others. Both are very good time keeping.

Modern wrist watches use drilling and or laser trimming and no longer have screws. They are inherently temperature compensated to there is no need ot move screws to adjust the temperature compensation. The index adjusts mean time. This is how most wrist watches are made. The added benefit is that air resistance effects, admittedly very small are eliminated.

Elgin made some very interstng freesprung wrist watches they called "Dura balance" Check Waynes Elgin site by searching for "Forgotten masterpieces". Not pocket watches, but interesting and affordable freesrung examples.

Today even freesprung wrist watches have mean time weight adjustments either screw or weight but are inset to reduce air rsistance.

So far as I know all freesprung pocket watches have mean time screws.
 
D

D.H. Grace

Tom,

I wasn't aware of the Waltham stud, or that they called it a "vibrating stud", although I'm still not sure why they called it that, or what was actually new about it.

Isn't the Waltham stud essentially what the English and Swiss had, for sixty years or so, been calling a "resiliant" or "moveable" stud? How does the Waltham stud vary from Hardy's resiliant from 1805?

Second, does the Waltham model actually change the length of the balance spring, or the geometry of the spring? On a resiliant stud, the adjustment determines how close to the center the stud is drawn by flexure. If the Waltham stud changes the length, does it alter the beat of the watch?

I haven't been able to find pictures or a description of the watch I was thinking of, where impulse was delivered through the balance spring via a moving stud. I'll keep looking.

Jessica,

For explanatory books, consider giving a look at Claudius Saunier's "Treatise on Modern Horology in Theory and Practice". You should be able to get it from the lending library.


Regards,

David Grace
 

Ralph

NAWCC Member
Sponsor
Jan 22, 2002
5,136
263
83
Country
David,

I didn't get a chance to read the patent yet, but the number of the Waltham/Fogg patent is 41461.

Cheers, Ralph
 

Tom McIntyre

Technical Admin
Staff member
NAWCC Star Fellow
NAWCC Ruby Member
Sponsor
Aug 24, 2000
83,843
1,870
113
84
Boston
awco.org
Country
Region
David,

I don't have any information on a rigid privoted arm on English or European watches. I will try looking up your reference.

The ones I am familiar with have curb pins that may be advanced along the length of a straight extension of the hairspring.

As you can see in the picture, Fogg's patent was to use the excursion of the swinging arm as the regulation mechanism. I think it was pretty marginal since the vibrator could not be poised by its very design. However, it did allow you to add a functional jewel to the movement. :biggrin:
 

Modersohn

Registered User
Nov 15, 2003
286
0
0
Thanks, Dr. Jon and David. I will get the Saunier book, which I've heard of, and continue to ask questions. I really appreciate these answers.

Jessica
 

Dr. Jon

Moderator
NAWCC Member
Dec 14, 2001
6,343
758
113
New Hampshire
Country
Region
The Saunier Treatise on Modewren Horology (Circa 1870 when written in French but hte English versions are circa 1885) is very good. Original editions are bit pricey and there are reprints.

I also like the Glasgow Book on this topic which is also available in reprints.
 

Modersohn

Registered User
Nov 15, 2003
286
0
0
Thanks, Don. That looks a good article as well as having some find illustrations. I'm printing it out now.

The Saunier book is expensive- so I'll use interlibrary loan. I may get more time with it that way. I've ordered the Glasgow book, though.

Jessica

Member of Chapter 149
 

Forum statistics

Threads
164,686
Messages
1,432,664
Members
85,738
Latest member
cspeed8
Encyclopedia Pages
1,101
Total wiki contributions
2,863
Last edit
Rockford's early high grade movements by Greg Frauenhoff