BY WALT ODETS
The bottom plate of the caliber 452 is finished as handsomely as the top plate. The screwed cap jewel plate for the lower balance
pivot is visible at 8 o’clock.
The keyless works exhibits
classic Swiss design. But note the unusual and elegant clutch spring integral with the setting lever (arrow).
Like all high-grade movements of its day, the caliber 452 utilizes a split, bimetallic balance with overcoil balance spring.
As illustrated right, the balance rim is constructed of fused layers of brass (1) and steel (2). The difference in coefficients of expansion of the two metals
causes the two free (cut) ends of the rim to move outwards at lower temperatures (blue arrow) and inwards at higher temperatures (orange arrow). The change in effective
diameter of the balance adjusts rate and compensates for temperature effects on the balance spring. The balance contains threaded holes to accept screws (3), which serve to poise the balance,
adjust rate, and diminish or augment temperature compensation. Washers (4) can be added or removed from under the screw heads to adjust mass. Those screws nearest the cut ends (5)
affect temperature compensation most. The balance arm is visible at (6).
The terminal curve (overcoil) of the balance spring (1) and spring stud (2) are shown at
Upon completion of service, the Vacheron’s rate (left, 1) rate was +159 seconds/day with the regulator index fully
retarded. I corrected the position and angle of the stud (outer attachment) in the non-movable stud carrier, and also slightly adjusted the shape of the terminal curve to provide better centering of
the spring. The results are shown in (2). Rate had changed to + 91 seconds/day, the beat error was lower (from .5 to .3 milliseconds), and the amplitude had improved (249 to 277,
although these are not absolute figures).
Because the regulator index was still fully retarded at +91 seconds/day, it was
necessary to add a matched pair of gold washers to the two opposite “neutral” screws, one at each end of the two balance arms. Symmetrical adjustment does not affect poise. Screws in the neutral
area do not affect temperature compensation because they are removed from the cut ends of the balance.
“Timing washers” (which also
adjust poise and temperature compensation depending on which screws they are used on) are available in a variety of diameters, thicknesses and metals. At left, a selection of brass, silver,
gold, and platinum washers is shown. Note the millimeter scale at the bottom of the photograph.
With the two washers installed
on opposite sides of the balance, the rate changed from +91 to -67 seconds/day.
With the regulator index
adjusted as shown at left . . .
. . . the watch could now be adjusted to +2 seconds/day with minimal beat
error and excellent amplitude. Crown-down performance with this adjustment was -7 seconds/day–not a stellar positional performance by contemporary standards, but a very good one for a watch of this
The Vacheron with caliber 452 is a watch from the days when Vacheron, Audemars Piguet and Patek Philippe were the three, and only
three, great names at the pinnacle of Swiss watchmaking. While a vintage watch, with it’s age and quirks, does not appeal to all, it offers the possibility of owning something not easily found or
afforded in today’s market. Greatness. I think it’s worth the trouble.
© 2020 Bourne in Time Inc.