The Index Mobile Rattrapante System from Dubey and Schaldenbrand

The Dubey and Schaldenbrand Index Mobile rattrapante chronograph system is a very unique and interesting alternative to the traditional, complex, and very costly rattrapante movement design. In my own experience with several implementations of the Index Mobile system, it has shown itself to be practical and reliable. And, it looks cool besides!

History

The origin of the Index Mobile rattrapante system goes back to 1946. In that year, Rene Schaldenbrand, Head of Production, Complicated Watches, had developed an economical flyback seconds chronograph design. Together with Georges Dubey, who at the time was also a professor of complicated horology at Technicum in La Chaux de Fonds, Schaldenbrand formed the Dubey and Schaldenbrand Company to produce and market the design, which they called the Index Mobile.

Patents were subequently applied for, and in 1948 Swiss and French patent rights were granted; US patent rights followed in 1951.

A partial description of the design from the US patent filing follows:

"...chronographs with two co-axial long seconds-hands, one of which is a fly-back hand. An important feature of the invention resides in that the movable elements of the two seconds-hands are connected with each other by means of a spiral spring and that one of the said hands carries a stop adapted to engage the other seconds-hands."

The original prototypes and early working models were based on the Valjoux 77 base chronograph caliber.

A number of different brands were used by Dubey and Schaldenbrand to market the Index Mobile system, including Edo (1950-1957) and Too Swiss (1962-1963), as well as the Dubey and Schaldenbrand name itself. The system was also adopted by other branded chronograph makers, including Breitling and Baume and Mercier (see below).

A later subsidiary patent was granted in the early 1950's on a design that moved the entire rattrapante system under the dial. I am attempting to verify if this design was ever implemented in a commercially released product (March 19, 2000).

In 1969, a major German collector, Adolf Benz, started Comor "to manufacture specialized and complicated wristwatches and pocket watches."
One of the model lines he released was based on the Index Mobile, which was contract produced for Comor by Dubey and Schaldenbrand. The model line was signed variously as either Comor or Adolf Benz, and was cased in stainless, gold plate, or solid 18k gold. The different models were variously released with either display backs or solid stainless steel backs. The Index Mobile were also marketed by other dealer channels, including pieces signed Tourneau.

Another significant person in this history is Ms. Cinette Robert. She started work at Martel Watch in 1960, and worked for Adolf Benz until his death in 1992, at which time she took over responsibility for the running of Comor. She continued in this role until 1995, when she acquired Dubey and Schaldenbrand from Bärtschi and Rosa, associates of Georges Dubey who had purchased Dubey and Schaldenbrand from the 70 year old G Dubey in 1982. Ms. Robert is still very actively involved (1999) with the entire operation of Dubey and Schaldenbrand.

The revived D&S, to commemorate the 50th anniversary of its founding in 1946, released a limited run of NOS movements in period correct new cases, signed Dubey and Schaldenbrand. This limited production run used up the remaining stock of NOS original Dubey and Schaldenbrand Index Mobile movements produced from the 1950's through the 1970's. (unconfirmed)

The pieces from this limited production run sold out very quickly to collectors. As far as I know, all of these pieces were released with display backs.

I have seen a few of the L.P. re-editions come back on the secondary market, but very rarely.

Technical and Operations

(mineral glass back, Comor 18k gold edition, negative reversed)

The movement caliber specifications for the Landeron cal. 248 are:

• 17 jewel
• 18,000 bph
• 13 3/4 ligne
• Ø (diameter) 31mm
• Manual handwind.

This caliber was originally developed and produced by Fabrique d`horologie de Fontainemelon (as distinguished from Hahn-Landeron movements).

Description of the mechanism from an Antiquorum catalog: "The system Index Mobile was patented in 1948 by Georges Dubey and René Schaldenbrand. It is a simplified sweep-hand construction, in which the two chronograph indicators are linked by a hairspring visible on the dial. The sweep hand is stopped by the coaxial pusher on the winding-crown, but only as long as the finger holds the pusher down. Wheel released, the sweep hand springs to the position of the actual chronograph indicator. (quote courtesy of Mr. S Sugiyama from the original source)

Closeup of the spiral spring
and central axle, rattrapante engaged.
(photo source - Dubey and Schaldenbrand)

Description of the mechanism from Europastar:

"The principle of the function is simple: the center wheel, situated precisely on the center of the chronograph movement is pierced all the way through making way for a central axle to be placed on the dial side connected to the index hand equipped with its spiral spring connected to the direct-drive of the chronograph. On the movement side, a small lever or steadying spring can nudge up against the the head of the center axle, via the movement of the pusher and an intermediary lever or break spring blocks the index hand. When the chronograph is started it suffices, to measure the intermediate time, to press the pusher which pauses the index. It remains paused as long as the pressure is maintained on the pusher. When the pusher is released this sets off the index hand to catch up to the chronograph hand. The spring of the Index-Mobile is extremely thin and does not effect the chronograph function even with the pause mechanism. However, contrary to a classic rattrapante, this function cannot pause the index hand past 58 seconds. At that time the chronograph hand having made a complete tour hits against the index hand and the movement is stopped. However, with this consideration, 58 seconds represent a reasonable time to measure intermediary time."

While the previous description is unclear about the state of the timekeeping functions when the Index Mobile's rattrapante functions are engaged for more than 59 seconds, and therefore physically blocked, owners who have actually tried this verify that the watch continues to operate and keep time.

H Holland states, "(On) my D & S Index Mobile (one of the Limited Re-editions from 1996 -- rose gold case, silver dial)...The two chrono hands are linked by a coiled spring visible through the dial-side crystal. When the pusher centered in the crown is pushed, the top hand is stopped, and the lower hand continues the timing. The top hand stays stopped only as long as the pusher is held in, as it is stopped by a friction arm (visible through the back crystal). When the pusher is released, the spring instantly causes the top hand to catch up to the lower one.

But here's an issue: '(The Europastar article states that) ...contrary to a classic rattrapante, this function cannot pause the index hand past 58 seconds. At that time the chronograph hand having made a complete (turn) hits against the index hand and the movement is stopped. '

The problem is that the penultimate sentence of the quote leads one to believe that the watch's internal movement is stopped. Not so. Nothing is stopped. The lower hand simply bumps up against a little tab on the top hand (which also serves to stop it when it catches up) and carries it along, overcoming the friction which stopped it in the first place. I don't know why one would ever do this (other than to test it, as I did) but no harm is done. I wouldn't do it often or for long, though, because of the increased friction.

The other point is that some of the earlier writings about the movement have led one to believe that the rattrapante hand can only time up to 58 seconds. Again, not so. True, the (rattrapante) hand can only be held still for 58 seconds, but (practically) it can time any interval you chose (sic). The way these things are usually used (e.g. to measure elapsed time at various points in a horse race) I see no disadvantage at all. You simply have to make note of the time at each stopping interval before releasing the pusher and letting the index hand catch up so it can be stopped again. You can actually time for any interval you want. Although the minutes accumulator only goes up to 30 minutes, you could certainly (extrapolate) beyond that. "

Historically, Bovet had created and patented their Mono-rattrapante in the mid-1930's. The Bovet design used only one sweep second hand, which could be stopped to take an intermediate reading, and when released, would "catch up" to the continuous accumulated time, hence the name "mono-rattrapante."

It has been suggested that the Index Mobile system was an extension or derivative of the Bovet Mono-rattrapante design. Though there may be technical similarities, I would argue that they are in fact quite different practical means to a similar end. I must also add that I prefer the Index Mobile design for some very distinct, albeit non-technical, reasons -

• the more classical rattrapante look of super-imposed twin sweep second hands, and
• having the normal sweep second hand continue its motion while the rattrapante hand is stopped to take an intermediate reading, something impossible with only one sweep second hand, is somehow more reassuring, ...

It should be pointed out that both the Bovet Mono-rattrapante and the Dubey and Schaldenbrand Index Mobile should be distinguished from the fly back variation of a chronograph, also known as retour en vol. While the Mono-rattrapante and Index Mobile allow the user to stop and take an intermediate reading, then "catch up" to the continuous accumulated time, the fly back feature resets the sweep second AND accumulated time registers to zero without stopping the timing movement, thus immediately starting a new timing cycle.

Some examples of practical applications of the rattrapante function and its variations would be the timing of individual lap times as well as the total race elapsed time of a race car, or individual finishing times of a multiple member racing team, where all team members start together but each finishes at different times.

The fly back function is used to time immediately consecutive, but discrete, events, where stopping and starting the timer would throw off the precision of the timing. This is frequently encountered in precision flying, where specific maneuvers take precise periods of time, with no breaks between the end of one maneuver and the start of the next. In these cases, the total cumulative time is usually not critical.

Case and Dial Design

The specific piece in the following description is from my personal collection. It was part of the Comor re-edition from the late 1970's, but unusually, was signed Dubey and Schaldenbrand, without the Index Mobile nomenclature. The case is 18k rose gold plated, with stainless back.

Below are more detailed scans of the dial and crown side of the watch. The dial has gold topped applied arrow markers and arabic 12 and rolled lance main hands. The dial is silver(ed), with sunken sub-dials, and printed scales.

Notice the symmetry and radial alignment of the minute and second hand length to the corresponding index tracks, as well as the hour hand length to the inner tip of the arrow markers. Notice also, however, the drop out on the printing of the unit digit 0 and some chapter indices in and around the 300 on the outer blue tachymetric scale.

The split second/rattrapante seconds are activated by the co-axially mounted crown pusher. Press in the pusher, and one of the second hands stop, while the other continues the time measurement. Release the pusher, and the stopped rattrapante hand "catches up" with the advancing sweep second hand.

The chrono pushers are a little unusual in their operation - the top only starts the chronograph functions; the bottom stops and resets. (Normally, the top starts and stops, the bottom only resets.)

The oversize crown and its large, well finished fins, give good purchase, and the "crown - case protrusion" is over the top of the case, rather than the typical bottom overhang. The crown winds, extracts, and sets very smoothly. (I find poorly designed or inappropriately sized crowns intolerable, especially on a manual wind movement!)

The crown pulls out, winds, and sets around the stationary, co-axial split second pusher. One of the things I love about this watch is the traditional rattrapante look of the crown mounted pusher.

Though not of Blancpain/PP/Lange quality, the case has very interesting bombe/horn lugs, and is nicely balanced at 38mm, not including lugs and crown/pushers.

Actual performance observations of this particular piece -

From February 29 through March 4, 2000, I used this watch on a regular basis. I rekindled the love affair with her based upon the ingenuity of the mechanical design, the case and dial design, and how well these areas are integrated.

I am somewhat disappointed at the quality of the case plating. I feel that given the uniqueness of the movement design, and the historic value of utilizing NOS movements from the "Golden Age" of Swiss mechanical watch making, the finished watch deserves better. The plating is uneven and much too thin for a watch of this "caliber" (pun intended, sorry!) The watch and all functions, including time keeping, all chronograph functions, and the Index Mobile rattrapante functions, have been working flawlessly. The pushers work with a light but positive click, all hands zero smartly, and the minute register hand "jumps" exactly at 59 seconds.

The observed power reserve seems a bit short at about 40 hours, with marked isochronism during the last 5% of the mainspring power cycle. Accuracy was a consistent +15 sec/24 hours, but when I let it run all the way to the end of the power reserve cycle, instead of winding it at the normal 22-28 hours, the accuracy dropped to -200 sec/38 hours.

Of course, the previous comments need to be tempered by the fact that these movements had been sitting unassembled, NOS for about 20 years, and then idle, assembled, unused, in my bank vault for the next 20 years. I have not had a chance to clean and lubricate the movement since "winding it back up," nor have I re-regulated it yet, so taking this into consideration, the performance is actually not too bad.

By comparison, a late-40's Minerva ch13-20 powered 18k chronograph, that had similarly been sitting for over a decade, has been running -1/24, but with a VERY short 30 hour power reserve. The Minerva is showing no detectable isochronism - it is keeping accurate time right up to the end of the power reserve cycle.

All in all, I am still in my re-visited honeymoon period with this piece and her cousins. Long may the honeymoon last!

Other Implementations of the Index Mobile movement

(left)

Baume & Mercier Triple Date Mono-Rattrapante, c. 1955

(right)

Breitling Serie Limitee
"Montbrilliant Rattrapante"
cal. Venus 170 - limited edition of 50 pieces (NOS)

Photos courtesy of S Sugiyama from their original sources

Comor in 18k case

Other variations of the Dubey and Schaldenbrand signed pieces

References (history, specifications, and scans):

H Holland
M Jeannot
M Finders
K. Pritchard
G-R. Lang
R. Meis
S Sugiyama
Dubey and Schaldenbrand
Comor
Misc original German and French language sources
Misc sources - anonymous owners and sellers
The Purist personal collection of watches and original product literature