It does sound like you have some 2870 wheels in there as its running at 28800. I don't know this calibre but, are all three hands running fast? I suspect it's just the second hand.
You can calculate thus calibres correct rate by counting the teeth on each wheel as pointed out by Marc. Here's an example for an Omega 561 where the barrel drives the second wheel which is attached to the cannon pinion so:
The second wheel large gear has 64 teeth and rotates once per hour (3600 seconds) by definition as the minute hand is connected to it via the cannon pinion.
The 3rd wheel has a small gear of 8 teeth which meshes with the large gear of the 2nd wheel. So, for one rotation of the centre wheel, the 3rd wheel rotates 64/8 = 8 times. Therefore, it rotates once in 3600/8 = 450 seconds. It also has a large gear and that has 60 teeth.
That large gear meshes with the small gear on the 4th wheel which has 8 teeth as well. So, for one rotation of the 3rd wheel, the 4th wheel rotates 60/8 = 7.5 times. Therefore, it rotates once in 450/7.5 = 60 seconds. It also has a large gear and that has 77 teeth.
That large gear meshes with the small gear on the escape wheel which has 7 teeth. So, for one rotation of the 4th wheel, the escape wheel rotates 77/7 = 11 times. Therefore, it rotates once in 60/11 = 5.4545 seconds. It also has a large gear and that has 15 teeth. This is the one that meshes with the pallet fork and so, the teeth pass the fork every 5.45/15 = 0.3636 seconds. There has been a little rounding of numbers in this paragraph for simplicity.
This tells us that this watch beats at 2.75 Hz ( 19800 A/hour = 2.75*60*60*2) as 2.75 times per second means one beat is in 0.3636 seconds.
I just copied this from something else I wrote but, it will make sense to everyone here.
If I wanted to change this movement to run at, say, 28800 A/h, I could do it just by changing the number of teeth on one or two wheels. I can't immediately see a way to do it with one as it would have a lot of small teeth.
Usually the fourth wheel runs at one revolution per minute as then we can easily mount a sub second hand on it. So, maintaining that but changing its large gear to have 96 teeth (was 77) and the small gear on the escape wheel to have 6 (was 7), it becomes a 28800 movement. Nothing else needs to change and it now runs at 4/3 speed (a bit like my life since I passed 50...)
All you need is the correct wheels from Cousins for a 2871.
Hope this help, Chris
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