This provides a good description of how the balance wheel works: https://en.wikipedia.org/wiki/Balance_wheel https://en.wikipedia.org/wiki/Balance_wheel It is

This provides a good description of how the balance wheel works: https://en.wikipedia.org/wiki/Balance_wheel https://en.wikipedia.org/wiki/Balance_wheel It is manually tuned, via weights and spring tension, to oscillate at a precise interval.