The Breitling Watch Source Forums

And so does every Swiss watch manufacturor who spec'ed their chronographs at 1/5 or 1/4 second. Breitling has done both over the years and continues to do so. Obviously, 3 small ticks marks between a second/minute marker divide the space into four equal parts (1/4 second chrono) and 4 small tick marks divide the space into five equal parts (1/5th second chrono). In fact, a 28,800 VPH movement (7750's, 2892's) moves the sweep chrono second hand forward eight times in a second. A 21,600 VPH movement (1873-1877) moves the sweep chrono second hand forward six times in a second. Tough for the human eye to discern the difference in either rate or spacing which dictates a specification that is apparent to the viewer when the chrono hand is stopped. (Hand width issue if nothing else.) Hope this makes sense for you. I proved the incrementation totals yesterday using a video camera with a frame time slowed to 1/4th real time in order to actually be able to see and count the "ticks" of the hand between second markers. Viewing the movement on the monitor at the reduced rate shows the number of movements ("ticks") precisely. Now the longstanding chrono incrementation issue is put to rest...
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

Thank goodness for that Ron!

I was still losing sleep trying to figure out how 28,800 at the escape wheel was translating to 1/5ths.

Now I can stop exploding my brain!

Phew Ron thanks for that, its a great to know we all share the obsession that is all things Breitling!




Ian

_________________
-------------------------------------------------------------------------------------------------------------------
Navitimer World, Callistino.
Omega Speedmaster Moon, Hamilton 992B, Steinhart BS LEII #2, B&R 01-92 Heritage

There is a good explanation of chrono drive in the 7750 at http://www.timezone.com/library/horolog ... 3433425752.

For those of you who are interested, the following is a boring description of the fundamentals of how the chrono works. You won't hurt my feelings if you skip over it.

The gear ratio of the chrono center wheel to the tilting pinion determines the arc of the center wheel relative to one rotation of the pinion. The tilting pinion couples the time train to the chrono train. The ratio of the fourth wheel to the pinion determines the number of rotations of the pinion for one rotation of the fourth wheel. The ratio of the fourth wheel to the escape wheel pinion determines the arc of the fourth wheel for one rotation of the escape wheel. The number of teeth on the escape wheel and the balance rate determine the amount of time it takes for one rotation of the escape wheel.

Obviously, the gear ratios of the time train are designed for the movement to display the time in increments relative to the balance rate. Independent of this, the gear ratios of the chrono train are designed to move the chrono sweep at the desired rate. This is all part of the design of the movement. Given the amount of space available and the number of teeth that can accurately be cut on a wheel of a certain diameter, the limitations of the chrono rate fall into a range that can be chosen for the chrono sweep. One could begin with a clean sheet of paper and design a movement that could run a 28,800 and sweep in 1/5 second steps on the chrono. Or, as is the case here, make it step at 1/8 second. It's all about gear ratios and the ability to machine the parts and make them fit into the available space.

Once the design is on the shelf and the movement is in production, it is pretty well cast in stone. From a manufacturing standpoint, it makes sense to use the same chrono parts in different movements running at different rates. So, it is no surprise that the sweep rate of the chrono is 1/6 second in a movement running at 21,600. These are probably the same parts used in everything operating from 18,000 to 28,800.

On a related topic, one can see the inherent problems with this design that cause the hands to jump when the chrono is started. The tilting pinion is always moving where the chrono center wheel is stationary. The instant the tilting pinion engages the center wheel when the chrono is started, there is an opposing force transmitted to the fourth wheel. The teeth on the tilting pinion may or may not be in perfect alignment when it is brought into contact with the center wheel. This inderminate alignment can create friction as the teeth are engaged. Also, there is a certain amount of inertia that must be overcome before things start to move. All these factors contribute to the opposing force transmitted to the fourth wheel. This causes the fourth wheel to pause momentarily.

Now, the motion works have a certain amount of backlash built in to allow for coupling the minute hand to the hour hand. To see this, pull the stem into the setting position (when the time is not in the date jump range) and rotate the stem forward and backward. There should be a slight motion of the stem that does not move the hands. That is the backlash.

So, the momentary pause of the fourth wheel is transmitted back up the time train to the motion works where the backlash in the gears can make the minute hand jump slightly as the time train stops and starts again ever so briefly. The amount of backlash determines to a great extent how much the minute hand jumps. The same pause also causes the second hand to jump.

This is probably more information than most of you care to know.

_________________
1809 Cosmonaute
1903 Navi
Navi Olympus
Super Avenger

I was just about to say exactly that

I read the 7750 explanation a few times when we had this discussion a few weeks ago and just when I think I get it I manage to confuse myself again. I think I just need to sit down with one in front of me and disect.

The jumping minute explanation makes perfect sense, but any ideas why some models seem to suffer more than others - the fundamental design is the same after all. The Motors has the 30 second chrono, but that wheel isn't subjected to these forces right?

Exactly. Those facts plus the manufacturor specifications (Chronologs) are the data which leads one to determine incrementation specificity, although my real-time test proves those specifications as false. That said, justification for 1/5 or 1/4 second incrementation markings is easily realized. Historically, 1/5 second timing has been (still is) applied to horse racing since the 19th century. Stopwatches for trainers and enthusiasts purchased today are marked 1/5 second increments. For a 21,600 VPH wristwatch chronograph (Lemania Cossie, Omega Speedmaster), the difference between 1/5th spacing or 1/6th spacing are simply not discernible to the naked eye. That assertion is also true for the 28,800 VPH movements marked in 1/4th second increments. As stated earlier, the width of the sweep second hand is greater than the difference between 1/8th second and 1/4 second. The manufacturor specifications then become misleading we might say, but aesthetics, practicality, manufacturing limitations, mechanical start/stop variances, human "reaction" limitations, and lastly our vision are the real reasons for more or less "standardization" of wristwatch chronograph incrementation markings...
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

The time train from the fourth wheel back and the motion works are the only parts of the movement, other than the chrono train, that are affected by the engagement of the tilting pinion. Any instability in the chrono itself is unrelated to the opposing force transmitted by the pinion. There will be a slight inconsistency in the chrono operation from the indeterminate gear tooth alignment, but it is so small it goes unnoticed. The operation of the counters is another discussion.

Is the 7750 movement in the Motors? I've never looked at those because they just don't appeal to me. I'm pretty much a Navitimer enthusiast.

There are a lot of factors involved in why some movements have hands that jump more than others. Most of it is related to backlash (and differences in the amount thereof) in the motion works. There is also some small amount of backlash in the time train. So, how much wear exists in the train, condition of lubrication, etc. all come into play. Variations on the same movement for different models may help or hurt. It's hard to say why some are better than others. You could probably set a dozen or so of the same model side by side and see differences in the amount of jump. As hard as they try, machining tolerances still creep in and cause small inconsistencies.

_________________
1809 Cosmonaute
1903 Navi
Navi Olympus
Super Avenger

It's a 2892 based movement.

Very interesting thread gentlemen. Thanks for the info Ron and onewatchnut, I'm very interested in the technical side of these fantastic instruments and thoroughly enjoyed the read

_________________
Happines is Good Health and a Bad Memory.
"Ingrid Bergman"

Hi, Tim. YW. Wanna No what got me started on this crusade? (Besides having read many articles on movement and chronograph operation... ) It was Breitling Chronolog specifications for the chronograph pieces. I happened to notice that the increment markings on my 2001 Crosswind (discontinued after 2004) concurred with the 1/5th second specification in not only the Chronolog but also the 2004-2005 sales handbook. However, there were two dial "styles" available for the CW, the one like mine with "slanted" arabics in the subdials and the other with "straight" arabics in the subs. The latter was marked for 1/4 second incrementation! Ooops! Why the disparity? I went back through all the Chronologs and found the same issue for the CW. Slanted subs=1/5th sec., straight subs=1/4th second markings. Hmmmmmmm... Next I checked specs on my 21,600VPH Lemania Cossie and my caliber 22 Flyback Cossie (2892-A2 movement, 28,800 VPH) and found both marked on the dials for 1/5th second and indeed spec'ed that way in the Chronologs and Sales Handbooks. Something wasn't adding up. I began to research chronograph operation relentlessly and was never able to find an adequate explanation for the disparity in markings. Detailed study of the movements led me to conclude it had to be gearing ratios in the chrono train and nothing else. Still, it seemed as though the "dirty little secret" would not be revealed with research and conclusions alone. A controlled "test" was the only way to prove with finality what many of us suspected or denied. That is the reason I set up the camera and software and used four of my Breitlings as test subjects. Fortunately I have available all examples of the calibers and markings necessary to make the test conclusive and accurate. A little embarrasing for me to have to "stand corrected" from false early conclusions but lacking "finality" was nagging at me hence the decision to set up the test. Glad I did it and I hope it helps those of us who are truly intrigued by what many would consider to be trivial and unimportant.
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

Sounds like you went to a lot of trouble to find your answer - good on you. There's nothing worse than being uncertain about something, then putting in a lot of research only to discover that you still don't have an answer; that can it be very frustrating. Impressive too that you actually experimented as a means of discovery.

No doubt you feel a great sense of satisfaction from your efforts and so you should. Thanks for sharing

_________________
Happines is Good Health and a Bad Memory.
"Ingrid Bergman"

So, where is the video?

I've understood this entire thread, but what the heck is a chronograph?????

_________________
SHARKMAN

It's that device that spins, uses a needle and plays music!

C'mon Shark... get with the new technology .

_________________
Chrono Jetstream
Montbrilliant 1903
Aerospace E79362

Oh that thing. All these fancy new fangled words the kids are using these days.


Sent from my iPhone using Tapatalk

_________________
SHARKMAN