The Breitling Watch Source Forums

Correct.

I am well aware that vph is a measure of balance oscillations jonci - at the risk of sounding arrogant I have written some articles on here about how escapements work!

As bnewbie says, and as I tried to explain earlier in the thread, you cannot compare vibrations directly to Hz, you have to divide by two. Wave frequency has to consider the part of the wave above the line, and below the line - there's some wave basics here - http://id.mind.net/~zona/mstm/physics/w ... eParts.htm

And I don't have a 'bro'

Sorry, I was wrong then. Thanks for the correction. But anyway, the 30s Bentley Motors are also 28,8kvph, and they are 1/8 accurate. I guess if they used a half as big center sec wheel as the current one the 7750s would be also 1/8.

Sorry for 'bro'-ing you...
Hope we are OK.

Hi Roff. Just to follow up a little bit for you, here's a Vacheron Constantin 1/5th second Chronograph for you with a caliber 1137 movement (21,600 vph)...

http://www.feelgoodwatches.com/product_ ... ts_id/3665

Once again, a 3HZ chrono incremented for 5, IOW, a 3/5 gearing ratio for the chrono. You'll find the same for the Audemars Piquet Royal Oak chrono, the Blancpain Air Command Chronograph "Trilogy", the Roger Dubuis G34, etc., etc., Wouldn't it be funny to watch a salesman at Tourneau explain to a customer a chrono second hand incrementing 3 times/second when the dial is marked for fifths?... Ain't gonna happen cuz that's not the way it works...
Best,
Ron

_________________
"The Sailor Who Fell From Grace With The Sea"...

Click to view: 500px Photo Gallery "Flow" or... 500px Photo Gallery or... Breitling Pics Slideshow

I'm trying to find out exactly how this 'acceleration' gearing works - it's hard to get your head around something ticking faster than the escapement because the escapement controls everything.

I know that the wheels are earlier in the drivetrain than the escapement, but it's still tough to get my head around how something moves 5 times for every 3 or 4 beats of the escapement - 6 or 8 makes more sense because it's a multiplier of the frequency, but I'm having a tough time with this.

I understand that it can be geared that way, but unlike say a car transmission a watch movement isn't moving constantly, it's always being stopped by the pallet fork, and that's where I'm struggling - in a 3/5 or 4/5 gearing the stops aren't going to be consistent.

I have been reluctant to weigh in on this one. But, at the risk of complicating the issue, my analysis of the discussion so far is that we are mixing apples and oranges.

The rate of the balance determines the smallest increment of time that can be resolved by the movement, while the chronograph hand displays measured time in increments marked on the dial. These two are not necessarily the same.

Take for example, the following:

VPH = 18,000 = 1/5 sec. resolution

Yes the frequency is 2.5 Hz, but the escape wheel advances at a 5Hz rate. It moves from the receiving pallet to the discharge pallet and back to the receiving pallet in one full cycle of the balance wheel. With the proper gear ratio, this allows the wheel with the seconds bit (hand) to step five times in one second.


Extending this, we get:

VPH = 21,600 = 1/6 sec.
VPH = 28,800 = 1/8 sec.
VPH = 36,000 = 1/10 sec.

At 36,000, the seconds bit appears to glide. It is almost impossible for the eye to see the steps.

Now to the chronograph.

The center sweep hand is driven by a wheel at the opposite end of the arbor. The wheel contains the correct number of teeth to advance it in the increment of time the watch is designed to display. There are at least two limiting factors in the chronograph. One is the number of increments that can be displayed on the dial and still be read by the human eye. The other is the size of the wheel on the sweep arbor and the number of teeth that can be accurately cut into it. Obviously, the wheel cannot step in an increment of time smaller than the resolution of the escapement. For example, a chronograph in a watch with a rate of 18,000 is limited to 1/5 second with direct gearing. With high rate escapements, the sweep hand is geared to advance at the increments displayed on the chronograph dial regardless of the rate of the balance.

So, we usually see chronograph dials with either 1/5 or 1/4 second increments. Regardless of the rate of the watch, the chronograph sweep is geared to step in the dial increment.

I'm sure this will fuel the fire! There may well be more things we can add to this discussion, but I tried to cover the basic operation of both parts of the watch.

I'm certainly not an expert in this area. I'm just an old watchmaker who owns several complicated watches, and I even work on them (with trepidation) when they need it.

Although, I'm the first to recommend sending high quality watches to authorized service centers. They have the correct parts and will not sell them to anyone except an authorized repair shop. Substituting aftermarket parts destroys the originality of the watch. At my age, I'm reluctant to invest six figures into a facility that will pass a Rolex inspection.

Onewatchnut

_________________
1809 Cosmonaute
1903 Navi
Navi Olympus
Super Avenger

I followed that most of the way (thank you).

Here's where I still get lost. In a 28,800vph / 4Hz movement, like a Breitling, how does a 1/5th second chrono actually opearte. I understand how it could be 1/4 or 1/8, but I am struggling with 5 ticks per second. I understand the gearing concept, but the chrono seconds is still driven by the running train and is therefore stopped by the escapement.

How is the issue of there being 1 1/4 ticks per Hz resolved? Gears can help, but the final chrono seconds wheel is still going to need the 5 per second gearing - isn't it?

Roff,

The fourth wheel is still rotating at one revolution per minute. With the 28,800 rate, it does it in 1/8 second increments. So it actually moves in 480 steps per minute while the center chrono wheel operating in 1/5 second increments has 300 steps per minute. The pinion that drives the center chrono wheel connects the fourth wheel to the center wheel. There is a great picture of it at http://www.timezone.com/library/horolog ... 3433425752. Scroll down and look at the sixth picture. That little pinion is the driver of the center wheel on the 7750. As you can see from the picture there are a different number of teeth at each end. That is what reduces the 8 steps of the fourth wheel to the 5 steps of the center wheel in one second.

I have yet to figure out how the Swiss find such elegant solutions to problems. They are really good at complications, and have been for a long time. I have some complcations that are at least 100 years old and they were good at it back then too!

_________________
1809 Cosmonaute
1903 Navi
Navi Olympus
Super Avenger

Got it!

Thanks onewatchnut - and feel free to allow me to look after some of those old watches when you get tired of them

Hi, Roff and OWN. Here is an animation which shows you how it's done...

http://www.zvisuel.com/montrespassion/english/

As you can see, the chronograph gear wheel is "hardwired" to the chronograph seconds hand (via its arbor) and only turns when it is engaged to the drive wheel in the gear chain. If the animation was large enough you could count the teeth on the chrono gear and the drive wheel and determine the gearing ratio. Of the twelve animations offered, the chrono animation is three down on the left. Hope this helps...
Best,
Ron

PS. Oh, BTW, while researching chrono's, I did read somewhere that the origin of the 1/5th second incrementation had something to do with timing horse races with stop watches!

PPS. And if you really want to do some reading "between the lines"....

http://www.faqs.org/patents/app/20090103398

and more...

http://www.faqs.org/patents/app/20090129209

_________________
"The Sailor Who Fell From Grace With The Sea"...

Click to view: 500px Photo Gallery "Flow" or... 500px Photo Gallery or... Breitling Pics Slideshow