Aren't we lucky that gravity is constant? Common sense tells me that when the watch is on its side, gravity will slow down the mechanism, more so as the power winds down. When the watch is facing up or down, gravity will have less effect on the escapement so it will go at normal speed, hence "faster" than when the watch is on its side.

No watch expert can dispute the reality of physics.

 

Well gravity is far from constant - at least gravitational force isn't across the earth's surface. It varies with the underground mass of the area where you are located - more mass underground, the greater the gravitational pull. This variation is detected by satellites in order to perform underground surveys for things like understanding the amount of water beneath the surface of the earth in a given area.

As far how gravity affects the balance, and how that affects timekeeping is a lot more complex than you are indicating. Yes, there is greater friction with the watch in a vertical position, and this will affect the balance amplitude, and that in turn will affect timing. But how exactly that affects timekeeping is not nearly so straightforward - it really depends on a number of factors that lead to how isochronous the watch is.

Generally speaking though, often a lower amplitude will result in s shorter swing of the balance, and a faster rate, not slower as you have indicated, but again it depends on the specifics of the watch in question.

Cheers, Al

 

We're talking about a watch that stays in the same room, so we're lucky to be able to measure its accuracy given a constant G. Now, I stand corrected that the shorter swing due to drag (not friction) caused by gravity when the watch is in vertical position would indeed make the timing go faster. But either way, the position of the watch will affect how slow or fast the clock ticks--it is not a matter of luck.

 

Depending on where you live and what's under the ground, the gravitational force in a given location may change over time. Not on a short timescale mind you, but it can change. For example in California where groundwater has been pumped out of the ground in massive amounts during drought cycles to grow food, this leaves more empty space under the ground and less mass, which gives less gravitational force over time. If those empty spaces don't collapse, then when the rains come, the water may come back to fill those voids, increasing gravitational forces in a given location again. This is well established science.

The reduced amplitude and shorter swing is caused by increased frictional loads, not drag. Drag would typically refer to the resistance of a body through a fluid or through air, and the relationship of the balance to the surrounding air inside the watch does not change when the orientation of the watch changes. When the watch is in a vertical position, greater surface area is in contact between the pivots and the jewel. The sides of the pivots will have more contact than the ends of the pivots do in a horizontal position, because the end of the pivot is rounded:



So consider a watch running dial up (horizontal position) and I've modified an existing diagram to explain - the entire balance is riding on one rounded pivot end of the balance staff. in this instance the surface contact between the balance staff and the cap jewel is minimal - almost a point contact, so the friction is very low:



If I now put the watch in a vertical position, say crown up just as example, now we have this:



Increased surface area as now instead of just one rounded pivot end, we have two parts of the balance staff in contact (one on each end) and a much greater surface area of the side of the pivots at both ends in contact with the sides of the hole in the jewel.

All this leads to a shorter swing of the balance, which in turn means fewer degrees of amplitude, and therefore shorter distance travelled. This reduces the period of the oscillation and speeds the watch up, however manufacturers of watches take great pains to prevent this change in timekeeping from happening. There are ways of mitigating this, and depending on the adjustments made and the type of balance it is and the regulating system used, how the timing reacts can vary wildly.

This is a complex system at play, and not easily reduced to broad sweeping generalizations.

Cheers, Al

 

The balance wheel is subjected to drag, and not much friction. And now you've illustrated the effect of gravity on the pivots. And there is much more to it than these two. Your post just proves my point even more, i.e. that the position of the watch affects the time keeping (which can be used to speed up or slow down the watch).

 

An opinion poll here: I plan to never have anything on my Railmaster 60LE polished or refinished (I'm actually enjoying seeing that it's collecting some "personality" as we venture through life together), but like usual (at least for me), the 12 o'clock side of the Trilogy bracelet is picking more scuffs than the 6 o'clock side. I'm wondering if I should reverse them to get them to wear more evenly, but that would make the more visible (to me) 6 o'clock side less attractive. Obviously, I plan to also reverse the clasp so it would keep its normal configuration.
But I'd love some opinions on this minor dilemma here...

 

I'd keep the 6 o'clock side pristine and leave the 12 o'clock side absorb the brunt of desktop diving. Incidentally, my bracelet also has some battle scars, particularly near the clasp. It's all part of life.

 

Is it just my poor observational skills or are all the spring bars that come with the Trilogy watches, the ones installed on the bracelet as well as the spares in the spring bar tool, all the same length? I thought ones for bracelets were supposed to be shorter and ones used for NATO straps were supposed to be longer - at least that's how it is for the moon watch box sets. The trilogy set comes with a NATO and a leather strap but the spring bars all seem the same length to me. Has Omega done away with that?

 

Ok, I will leave it as is....thanks for the input....
I almost wish that the Trilogy pieces were made of 904L steel just for more scuffs and scratches!
(I understand that 316 steel is higher on the hardness scale and thus more scratch-resistant)...too bad

 

If your point is that watches have variation in positions, and that can be used to self regulate by storing it in different positions at night, then yes of course that is common knowledge - there's nothing to prove there. Just keep in mind that the bulk of the work in timing the watch is to eliminate as much positional variation as possible, so having less variation is the goal. It's very difficult to get zero variation, but sometimes you can get very close - total variation over 6 positions of 1.6 seconds:



The balance certainly has aerodynamic drag, and how much drag a particular balance may have is greatly affected by the style and shape. For example all else being equal a smooth balance like this:



Will have less drag than a balance with screws, like this:



But the amount of aerodynamic drag is constant, and doesn't change with the position of the watch - it would only change if the balance was changed somehow. If you are asserting that it does change with position, you will have to explain exactly how that happens.

The friction in the system isn't huge certainly (or the manufacturer isn't doing their job very well), but you appear to be underestimating it's effects. The photo of the pivot I showed in a previous post was one I was burnishing round again, as it had flattened over years of running. Just to give some perspective on how much a small amount of added friction can make on balance amplitude, this is the pivot before the final burnishing was done - you can see it has a rather large flat spot, and only a small radius on the end:



Burnishing in the Jacot tool:





And the pivot end is almost completely rounded:



This pivot is 7/100ths of a mm in diameter, and just this amount of additional burnishing making it rounder and eliminating a very small amount of friction, changed the balance amplitude 20 degrees in the horizontal position, so although the amount of friction is indeed very small, it doesn't take a lot of it to have a large impact on balance amplitude.

Positional variation is made of up of a lot of things and balance amplitude loss from frictional loads is one of them. There are a host of different factors that come into play, so everything from pinning point of the balance spring, spacing of regulating pins, location of balance spring between regulating pins, how well the balance is poised both statically and dynamically in particular (acceleration through the lift angle being -ve or +ve), and many other things determine how a watch runs in positions. But all the work I do on a watch to get it running properly is meant to compensate for these problems.

As I've been saying all along, it's a complex system that is not well suited to simple generalizations.

Cheers, Al

 

Aerodynamic drag--i.e. the interaction of a body through air--is not the same as the drag caused by the force of gravity acting on the balance wheel. And certainly, the position will not change the aerodynamics.

I don't need to explain exactly how gravity affects the motion of the balance wheel. It's unnecessary. It's common sense.

 

Fault me for sloppy reading, but was this actually said?

 

Sorry, but have you ever taken a physics course before?

 

We agree completely that the position of the balance will not change the aerodynamic drag - I've said this a couple of times already.

How it can affect the "motion of the balance" is far from common sense, which I take to mean common knowledge that is easily understood by a large number of average people. Unless you are a watchmaker or have a rather extensive understanding of dynamics, I'm not sure you really understand how complex this system is. If you want to explain how a poise error affects the positional variation as it passes through the lift angle with +ve or -ve acceleration, then I'll believe that you have a full understanding of how all this works, and the true effects of gravity on the motion of the balance. I'm not expecting you to know this by the way, because it is far from common knowledge that is easily undertood by a large number of average people...

But back to gravity and it's affect on balance amplitude...

Let's look at your marked up photo:



I'm not sure what it is exactly you are trying to illustrate here that I have not already shown in the previous post where I explain how the friction on the pivots changes from vertical to horizontal. The same amount of gravity is acting on the balance when it is oriented like this:



(Arrow indicates contact point with cap jewel)

Or like this:



Which is the same as this:



(Arrows indicate contact points with hole jewels)

The measure of the force of gravity acting upon a body is it's weight, and the weight of the balance doesn't change when you turn it from one orientation to another. The only difference is the amount of surface area of the staff in contact with the jewels. There is more with the balance in a vertical position, and therefore as I've stated, the frictional loads increase and the balance amplitude drops. What you are calling "drag caused by the force of gravity acting on the balance wheel" is again simply the additional frictional loads I've already described in detail.

I'm not sure if there is a language barrier getting in the way here, or if you are just not used to the technical terms, but the drop in amplitude is clearly caused by added friction between the staff and jewels. The vague notion of "drag" you insist on using really muddies the waters if you want to have a serious technical discussion...

Cheers, Al

 

Gravity affects the frictional load at the center of the balance wheel AND the very motion of the wheel itself.

 

Please feel free to elaborate on this - explain the mechanism of action involved.

 

I'll just use this link about the pendulum (which is similar in many ways to a balance wheel). Both motion and friction are mentioned.

https://sciencing.com/affects-swing-rate-pendulum-8113160.html

Motion
Pull a pendulum back and release it. You can let the pendulum swing back and forth on its own, or in the case of a clock, have it swing powered by the gears. Either way the principle of periodic motion affects the pendulum. The force of gravity pulls the weight, or bob, down as it swings. The pendulum acts like a falling body, moving toward the center of motion at a steady rate and then returning.

Air Resistance/Friction
In a real-world application air resistance affects the swing rate. Each swing encounters that resistance and it slows down the swing, although it might not be enough to be noticeable during one swing. Friction also slows down the swing. If the pendulum is swinging based upon inertia from the initial release eventually it will come to a stop.

Forgive me as I'm too lazy to elaborate.

Anyway, let's just enjoy our watches. Hope to see how each position of the Railmaster affects the speed of the watch so I can "regulate" mine.

 

I'll snip the Googled knowledge here, and just say that a pendulum isn't really the same as a balance wheel as you believe. The balance wheel is not "returned" by gravity like a pendulum is, but by the balance spring. Also, a balance in an ideal situation is not a "weight on a string" like a pendulum is - it is a wheel that is poised specifically to eliminate any heavy spot, where a pendulum is essentially just one big heavy spot at the end of a string or metal rod - completely different situation. In a balance, it pivots around the center of mass - not the same at all for a pendulum as it's pivot point is far away from the center of mass.

When there is a serious poise error in the balance, this leads to a timing error that will show in only the vertical positions - this is one way where gravity can affect the timing that is not related to friction, but it has nothing to do with going from horizontal to vertical. I've already stated this several times in previous posts referring to the acceleration being positive or negative through the lift angle.

The key thing that drops amplitude in that transition from horizontal to vertical is F=uN.

Common sense isn't always so common...

Cheers, Al

 

Balance wheels work in Space, pendulums don't. Very different processes.

 

I said "similar," not "the same."

https://www.hodinkee.com/watch101/balance-wheel

The hairspring and balance wheel together are the regulating organ of the mechanical watch. This harmonic oscillator is very resistant to outside disturbances, which makes it especially suited to keeping track of time. The balance wheel and hairspring is very similar to the pendulum in a clock. The major difference is that the balance wheel and hairspring are portable, while the pendulum is not.