Splitting Seconds: Delving into a Rattrapante Pocket Timer

Part I: The Basic Movement


At the 2000 Olympic Games in Sydney, much of the focus is on the athletes’ quest to shave tenth or hundredths of a second off world record times.
While timing at the games today is done by electronic means, triggered
by sound, touch, or even optically, this has only been the case for
the last 40 years or so.

In the not so distant past, timing was done manually, by a team of timers, each assigned to record the lap and finishing times for a specific participating athlete. To provide some compensation for problems with equipment and to remove some of the human error in timing, multiple timers were assigned to each athlete, which were averaged for the official results.

The stopwatches or pocket timers used to measure
such events paralleled the technology in watch movements. The entire
range of production ran from the inexpensive pin-lever stopwatch
to timers with high quality movements incorporating jeweled escapements, column wheel control, and rattrapante mechanisms.

The Clebar pocket timer is an example of the latter.
It was probably made during the 1950’s, and, like the chronograph
wristwatch of that time, incorporates many technologies which have
only survived in the high-end wristwatches of today. While it contains a high-quality movement, complete with a coaxial pusher single-button
column wheel chronograph and a rattrapante mechanism (NOT of the
“index mobile” design), it was selling for less than $100 at an
antique coin and jewelry shop in Old Town Alexandria, despite being
in excellent condition. I’m guessing that this was due to the relatively obscure brand name on the dial, and maybe a little due to the fact
that it is marked in 1/100ths of a minute rather than seconds.

The movement is housed in a chrome plated open-face
case with a double-hinged back. The enamel dial, inside caseback,
and movement are all signed “Clebar Swiss”, indicating that the
watch was probably cased at the factory and imported as a complete

(Note: throughout this article, I will interchange
the terms “rattrapante” and “split seconds”, as they are the French
and English terms for the same function.)

Movement Basics

While some pocket timers are based heavily on pocket
watches, they have a much simpler design because the chronograph works
are the entire focus of the basic movement: there is no need for complex and delicate switching mechanisms between the time and chronograph
parts of the movement, and there is a lot more space available, which
simplifies the layout.

A glance at the top plate of the Clebar movement reveals that it is
of fairly straightforward construction and finishing, reminiscent
of a typical Swiss made pocket watch. It is of a 3/4 plate design,
with the Main Bridge (A) housing the barrel and wheel train, the Escape
Wheel Cock (B) holding the escape wheel, and a Balance Cock (C) that
wouldn’t call for a second glance in a regular timekeeping movement.
The movement is marked “Clebar Watch Co. Inc. Swiss”, “Unadjusted
Seven (7) Jewels”, and is marked with the import code “KXF” on the
balance cock. These codes were placed on many imported watches as
a means for customs officials to recognize the factory of origin.
A separate duty was placed on the movement (according to number of
jewels) and case (by composition).

inspection of the main plate under the balance wheel reveals that
the movement, in fact, is a Venus 121. The star logo was used by
Venus, while the surrounding shield indicated that the movement
was Swiss. Similar shields can still be seen today on movements
made by ETA; the use of the shield has since fallen into disuse
and is typically no longer seen outside of ETA movements.

In addition to pocket timer movements, Venus made
good mid-grade chronograph movements, which were used in watches
like the Breitling Cosmonaute (Venus 178). The Venus company was
a direct competitor to Valjoux, that ceased independent production
prior to the formation of SMH and Valjoux’s subsequent incorporation
into ETA. Some NOS Venus movements have been used recently in high-priced limited edition chronographs by Minerva and Jacques Etoile.

The movement is simply decorated, with a nice,
even matte finish to the nickel plating, and an unpolished grained
finish to the bottom plate. This kind of simple finishing should
not be confused with a crude or unfinished movement; all of the
holes and parts have been carefully smoothed and sometimes polished,
to remove all burrs or other contamination which could cause alignment or operational problems.

Main Bridge also incorporates an uncommon feature – a spare parts
bin (right photo)! This bin, which appears to be a plastic capsule
set into an unused part of the bridge, incorporates a transparent
plastic lid held in place by a small screw. An inventory of the
parts reveals a spare balance staff (A), a replacement wheel arbor
(B), some spare screws (C), a spare click spring and crown wheel
return spring (both marked D). Pupils of the TZ Watch School, rejoice! If nothing else, this clearly indicates that the stopwatch was intended
to be serviceable by a watchmaker.

While such spare parts bins are not unknown in
vintage watches, it is a shame that this practice never caught on
more widely; perhaps the replacement century label slide on the
IWC perpetuals is the only contemporary example of this practice.
(It has been reported that some other companies have packaged spare
screws packed inside certain watches – but I’ve never seen or heard
of it firsthand.)

exactly is a crown wheel return spring, anyway? Well, this is the
first example of several features which distinguishes a pocket timer
from a watch. Since the crown on this watch is only rotated for
winding, there is a simple winding pinion (left photo, A) set directly on the square stem, with no clutch, pull out piece, or other keyless
works components.

The lack of a clutch thus means that there must
be some method for allowing the crown to “idle” when rotated in
the non-winding direction. Venus incorporated a rotating crown wheel
bridge (B) with a slide-way milled into the top (C). When the winding
pinion is moved in the direction marked by the arrow, the crown
wheel moves with it until the crown wheel teeth clear the ratchet
wheel teeth (upper left gear in the scan, not labeled). At this
point, the crown wheel is free to rotate. The crown wheel return
spring moves the wheel back into contact with the ratchet wheel
once force on the winding pinion is removed.

Why do it this way? Well, the keyless works is
a prime area for wear in a normal watch, as it is both potentially
open to moisture and dirt in the environment, and also is subject
to handling by the user. This simplified design replaces the high-wear small parts with larger ones located away from the stem, which results
in a much more robust design. Unfortunately, this design would be
difficult to adapt to a time movement, as it capitalizes on the
lack of need for a time setting position.

Once the bridges have been removed from the bottom plate, the wheel
train is revealed. All of the usual components are present, including
the barrel (A), the second wheel (B), the third wheel (C), the fourth
wheel (D), escape wheel (E), and escape lever (F). Again, because
of the lack of a constant timekeeping mechanism, the wheel train locations have been modified to provide for a directly driven center seconds
and minute subregister. Also, the gearing of the wheel train has been
modified in that the second wheel completes a rotation in 30 minutes
rather than 60. Note the fourth wheel brake protruding through the
circular hole in the bottom plate, just to the lower right of the
fourth wheel label (D).

balance cock and escapement of the Venus 121 is very much like a
regular pocket watch, but has a nickel balance wheel and nickel
alloy flat hairspring. Unlike most pocketwatches from this era,
some rudimentary shock protection is provided by the retaining clip
(A) – this has two extended arms which are screwed (red arrows)
to the cock away from the cap jewel, and thus allows for a small
amount of up-and-down motion if subjected to a hard shock. This
method of protection is quite similar in principle to the original
“Parachut” shock protection credited to Abraham-Louis Breguet.

Other features visible in this photo are the regulator
index (B), the balance wheel brake (C), and the movement maker code
(D). The balance wheel brake is actually a small pin or wire, which
protrudes through a rectangular cut-out in the plate. Remember this
feature in the next part of the article, where the chronograph works
are discussed.

This photo shows the underside of the balance. The standard double
roller is present, and again, the entire assembly would not be out
of place in a regular watch movement. The balance has been poised
through the removal of some material from the underside of the rim
(red arrows). Also visible is the regulator (tail of blue arrow
and inset), which is extremely well finished, and has a well designed
“foot” on the outer pin which prevents the hairspring from being
dislodged from the regulator. It also prevents other coils of the
hairspring from being caught as well.


This is the end of Part I.

Click Here to go to Part II

Copyright (c) 2000 Edward Hahn