Audemars Piguet Caliber 2870 – Part 2

On September 16, 2002

THE AUDEMARS PIGUET CALIBER 2870

Part 2

BY WALT ODETS

THE TOURBILLON

With
the exception of it’s (now relatively common) titanium cage,
the tourbillon of the 2870 is conventional in design.
As illustrated (right ), the cage (1)
is screwed to a base plate (2). The base plate
carries a pivot on the bottom that runs in a combination
jewel in the top plate. The cage carries a top
pivot (5) for the tourbillon assembly that runs in
a combination jewel in the tourbillon bridge (6,
inset). Both the base plate and tourbillon
cage carry combination jewel assemblies (behind the tourbillon
pivots) for the balance wheel (3). No shock
protection is provided for the balance.

As
seen from below, the tourbillon base plate carries the jewel
for the lower pivot of the pallet lever (1);
the escape wheel pivot and pinion (2 ) (which
travels around the fixed fourth wheel attached to the top
plate); and the lower tourbillon pivot (3).

The
top of the tourbillon base plate (4) carries the
typical truncated tourbillon pallet lever (1), the
escape wheel (2) and a bridge (3) to support
these components. The lower balance wheel pivot is
seen at (5). Because the balance pivots are
inside the tourbillon pivots, cleaning and lubrication require
a complete disassembly of the tourbillon assembly.

The safety
roller is made of ruby, and the impulse jewel is mounted,
not on a roller, but on the balance arm.

The fixed fourth
wheel, around which the escape wheel pinion rotates, is visible
in the bottom plate. The lower tourbillon assembly pivot
sits in it’s center.

CONCLUSIONS

In some ways
unabashedly extravagant, the caliber 2870 is also a
frugally elegant piece of engineering. The entire movement
is comprised of approximately 120 parts, including screws.
General, it is extremely well finished. If there is
a small complaint about finish quality, it would apply
to the tourbillon assembly itself, which is a small cut below
the standards of the tourbillons from Patek, Blancpain, and
Breguet that I have examined.

As tourbillon calibers go, the 2870 is also relatively
demanding of the watchmaker (and thus the owner’s wallet)
because of the tourbillon’s very small size and the compactness
of the entire movement. It is, however, an intelligently
designed movement and offers surprisingly robust construction.

Like most tourbillons, the movement does not provide balance
shock protection; requires disassembly of the tourbillon
for service of the balance pivots; and suffers from compromised
pallet lever geometry. Among contemporary tourbillons,
only Blancpain has been able to solve these problems.

All that said, the 2870 is a wonderful piece, and among
the small handful of truly original horological creations
for the wrist. It is simply not a watch for the faint
of heart or the light of pocketbook.

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