Hi Danny,

The arbor that rotates once per hour, and carries the minute hand, (indirectly if you like, via the cannon pinion), is usually the centre wheel, and its pinion (*not* the cannon pinion) is driven by the great wheel on the barrel. If there's another wheel between the barrel and the wheel arbor carrying the minute hand, that's another calculation.

For instance, if, say, there's a pinion of 10 leaves on the centre arbor, and the great wheel on the barrel which is driving it has 120 teeth, one revolution of the barrel will result in 12 revolutions of the centre wheel, or half a day. Now, if the spring calculator says that you'll get 14 turns of the barrel for a given spring thickness and length, that means that a full wind will run the clock for 7 days. (This has nothing to do with counting the rest of the train to discover what the beat rate is supposed to be).

Regards,

Graham