Bulova 11AOAC, 11AOACB, and 11AOACD: Technical Overview and Service Guide

The Bulova 11AOAC movement family represents a series of high-grade automatic mechanical movements manufactured in the 1970s. These calibers—11AOAC, 11AOACB, and 11AOACD—combine precision engineering with innovative self-winding technology and day-date complications. Originally used in mid-range to premium Bulova wristwatches, these movements continue to be valued by collectors and watchmakers for their reliable performance and easily serviceable construction.

Movement Specifications

All three movements in the 11AOAC series are automatic, equipped with lever escapements, beryllium copper balances, and shock-resistant KIF Elastor systems. They operate at a frequency of 21,600 beats per hour and offer a 42-hour power reserve.

• Jewels: 17 or 23

• Diameter: 25.60 mm

• Height:

  • 11AOAC: 4.50 mm

  • 11AOACD: 4.50 mm

  • 11AOACB: 5.27 mm (due to additional day-date mechanism)

• Features: Instant date setting, center sweep seconds, self-lubricated mainspring, adjustable stud holder

These movements are designed with a screwless balance wheel and a compensating alloy hairspring, offering stability and resistance to temperature variations.

Automatic Winding System

A defining characteristic of the 11AOAC family is its bi-directional automatic winding system. The oscillating weight, made of a heavy alloy, rotates freely in either direction and is mounted centrally. Its motion is transmitted to the barrel arbor through:

• Two reversing gear units

• A connecting wheel

• A reduction gear

• Driving gear for the crown wheel

One reversing gear engages while the other slips, ensuring a near-constant winding action. Importantly, manual winding is also possible using the crown.

Disassembly and Servicing Notes

The movement is secured in the case using either casing clamps or a movement ring. Removing the dial and calendar mechanism requires unscrewing two lateral dial screws. Servicing highlights include:

• Minute wheel and clutch lever springs are riveted to the pillar plate and not sold separately.

• The oscillating weight axle is integrated into the combined bridge, necessitating full replacement of the bridge if damaged.

• For proper assembly, specific setting wheel orientations and minute wheel spring tension must be observed.

Oiling is carefully prescribed throughout, with recommended Moebius oils such as 8030, 8300, and 9010 used for various contact points including pallet stones, cannon pinions, and the automatic train.

Calendar and Day Mechanism (11AOACB)

The 11AOACB adds a day and date complication, with instant date change functionality. The date is advanced by pulling the crown from position one to position three. Special attention is needed for:

• Alignment of the date corrector setting wheel (631) relative to the "E" mark on the plate

• Ensuring the day jumper seats between two teeth when installing the day disk (591)

• Verifying the intermediate day wheel (609) and date driving wheel (574) interact correctly

Improper assembly can cause date advancement issues or jamming.

Common Wear and Troubleshooting

• If the power reserve drops below 35 hours despite proper performance, replace the complete barrel assembly.

• The minute hand should return under spring tension after manual forward pressure, verifying correct minute wheel spring action.

• If the automatic system fails to wind properly, inspect the Breguet spring or look for friction in the reversing gear train.

Conclusion

The Bulova 11AOAC movement family reflects an era of intelligent watch design, offering reliable performance with thoughtful ease-of-service. With its robust architecture, multiple jewel options, and detailed technical documentation, it remains a favorite for both vintage watch collectors and professional horologists. Understanding its unique structure and following the correct servicing procedures will ensure these timepieces continue ticking for decades to come.