Bulova 7 AA

Description

A tonneau-shaped movement that looks somewhat familiar at first glance is the Bulova 7 AA, which is said to be based on the ETA 735.

Measuring 7 3/4 x 11 lignes, it ranks among the “full-sized” shaped movements of the 1930s or 1940s.

The deep-red ruby ​​bearings—installed everywhere except for the mainspring barrel and minute wheel already attest to the high quality of this movement; when the numerous cap jewels are also taken into account, the result is an unusually high jewel count of 21 for a manual-wind movement.

The gear train features a conventional layout: the large barrel directly drives the central minute wheel, followed by the rather large third wheel, the decentral seconds wheel at 6 o’clock, and a steel escape wheel that, while not exactly tiny, is very delicately crafted.

The pallet fork of this Swiss pallet lever escapement is beautifully executed: All the edges of the bridged are finely beveled.

The Bulova 7 AA utilizes a screw balance, which still lacks a shock protection.

Using the long regulator arm, which limits the effective length of the hairspring (featuring a Breguet overcoil), this movement can be adjusted effectively to its nominal beat rate of 18,000 semi-oscillations per hour.

On the dial side, alongside several cap jewels, you can also see the yoke winding mechanism.

Technical data

Usage gallery