Gyromax is Patek Philippe’s trade name for a balance wheel whose inertia can be adjusted by turning small weights set into its rim. It lets the watchmaker correct a watch that runs fast or slow without a conventional regulator. Patek Philippe fits it to its mechanical movements in place of the usual index.
How does a Gyromax balance work?
The classic Gyromax balance carries eight small round weights. Each one fits over a post sunk into the top of the balance rim. The weights are lopsided, and a slot in each one marks its light side. Turning a weight changes which way its heavier part points. That changes the inertia of the balance, and so the rate. A watch that runs fast or slow is corrected this way. The same adjustable blocks are used to poise the balance, so that its weight is evenly spread. The balance itself is made of Glucydur, an alloy.
How is it different from a regulator?
A conventional watch is regulated with an index, also called a regulator. Gyromax does away with it. Patek Philippe describes the system as a way of adjusting the balance and balance spring, and the assembly takes the place of the usual index. The weights differ too. A traditional balance carries screws around the outside of its rim. On a Gyromax, turnable weights sit in the top of the rim instead. Patek Philippe uses Gyromax in place of the traditional index in its movements. Calibre 16-250 is named as the exception.
Where it comes from
Patek Philippe received Swiss patents for the Gyromax in 1949 and 1951. The balance first appeared in watches in 1952. A specialist reference dates the design to 1949 and calls Patek Philippe the brand most closely tied to it. One advantage of the design is that the watch no longer needs a conventional regulator. Rolex’s Microstella balance is a similar design.
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