Horological Meandering

In this case, the chrono minute hand is driven by the second wheel of the train gear, with an added clutch system of lever and wheels (since that gear turns continuously), and not by the chrono seconds wheel, which is on the opposite side of the movement. Chrono minute hands placed in sub-dial arrangements might require other designs?

But in my initial post, which asked why this difference is rarely delineated, Cazalea was kind enough to rummage around and find a good diagram of the classic, spring-driven, semi-instant design in an old IWC manual. 

[For those few readers who are not already aware, Richard worked for IWC early in his career, where he distinguished himself by developing the first affordable rattrapante (split) chronograph built on the venerable Valjoux 7750. Until that date, the split was a really pricy object, as it took great skill (and time) to fashion it from not one, but two column wheels. The advantage of Richard’s solution was a module that added a second cam to the 7750’s far simpler cam lever system. Viola! (allow me a string player joke, here) an affordable split!]

Regarding the third type—or “true snap”as I have chosen to call it—Richard was kind enough to furnish the following video of Lange & Söhne’s solution, found in their Datograph.

HERE

And a bit more on the caliber, as a whole, is available HERE.

Habring points out that 

1)  Since both of these designs have gathered the energy for the "snap" over (nearly) the entire minute before, the instant of the snap does not cause undue pressure against the drive train.

2)  On the other hand, the semi-instant (spring) design requires that all of the energy required to move the spring be gathered and released in that second or so during which we can actually see (at least in my 1863) the chrono minute hand move just slightly before it "jumps" to the next minute marker.

3)  Although this design (#2) causes more pressure against the drive train for a moment during each passing minute (enough, actually, to cause the watch to stop if it is near the end of its power reserve), design #1 actually requires more total energy for movement function, due to the additional wheels/cams/levers required.

It was interesting to me to learn that Habring uses both the direct drive and semi-instant designs in his watches, a continuous (from the center) movement in his Doppel 3.1, and what he termed the “classical” semi-instant design in the Doppel-Felix; Doppel 3; and Chrono-Felix models. But wait! There’s more!

When Richard heard that I wished to post my findings on the site he pointed out that their new Perpetual-Doppel, a watch that celebrates the brand’s 15^thanniversary, hadn’t yet been reviewed here. Would I be willing to furnish a link? Well, of course—particularly as the watch features my preferred semi-instantaneous “jump” of the chrono minute hand! 

Specific information on this new piece may be accessed HERE. 

***

As cordial as Mr. Habring is, and as important as it was to have the input of a watchmaker on this topic (and quite a watchmaker this!), I must say it has been equally delightful to see how insightful and knowledgeable my colleagues on the Forum have shown themselves to be in their responses to my previous posts. Cazalea started us out with a diagram of the “classic” semi-instant design; Dr. No wondered intuitively if the additional hardware necessary for a true “snap” might not be a point of power drain; rdenney furnished an informative photo of Eble's caliber 139, and skyeriding, in addition to offering an important perspective on how prominently friction figures into some designs, furnished a concise list of calibers of all three types. And all of this before Richard’s final word! But this can hardly be surprising, considering the passionate following the mechanical watch enjoys on the WatchProSite.

Through this discussion I have been able to add several watches to my list that distinguishes chronographs by chrono minute hand movement. But this will be a work in progress for some time. So keep sending discoveries as you make them. I appreciate greatly the interest and support of my WPS brothers!

Fred Halgedahl