skyeriding
900
This will be a little messy, I hope you can follow my text...
Mar 23, 2017,09:11 AM
A watch having xx Hz, multiply that by 2 to get "how many ticks per second it makes" i.e. the beats per second.
So for instance, the 5070 has a 2.5Hz. That means, every second the watch makes five ticks (or, 18,000 per hour). Now, minus one to that - that should be the number of subsecond indices between each minute indice for seconds hand.
Now, if you notice the subsecond indices of the 5070, it does have 4 sub-indice between every minute indice - i.e. it is correctly spaced for five ticks a second. I try to present it graphically below:
|,,,,|,,,,|,,,,|,,,,|
It means every second, the seconds hand of the chronograph counter will land perfectly on each sub-indice above.
2.5Hz is therefore a very desirable "slow-beating" frequency for chronographs as it allows the subsecond indices to be of the aesthetically pleasing 4 ticks between each minute indice. Here is a nice video demonstrating a 2.5Hz movement and the subsecond indices being precisely accurate: https://www.instagram.com/p/BL-FgxUgVgs/?hl=en
On the other hand, lets look at the 5170. It uses a more modern, higher beat 4Hz. That is eight ticks per second (or 28,800 per hour). However, the 5170 still uses 4 sub-indices between every minute indice - the dial is meant for a 2.5Hz chronograph, not a 4Hz! The "correct" dial would be to have only 3 sub-indices between each minute indice - which will align with the 4Hz.
|,,,|,,,|,,,|,,,|
The above is what the 5170 should use. But the 5170 uses a 4Hz movement with a 2.5Hz dial, it means the second hand will not land perfectly on the subsecond indices at all!
Note that we can also to be fully accurate, use seven subsecond indices but that would be way too cluttered.
|,,,,,,,|,,,,,,,|,,,,,,,|,,,,,,,|
So, the number of ticks are halved as we can read when a second hand falls "in between" sub-indices without too much difficulty...
For comparison, a Speedmaster using the 9300 movement beats at 4Hz too, and its dial is correctly spaced for 4Hz by having the above scale.
A watch like the Lange Double Split uses a 3Hz movement, which means it uses 2 sub-indices between every minute indice. Perhaps they thought that having 5 sub-indices would be too cluttered...
|,,|,,|,,|,,|
Hope this isn't too confusing!
This to me, is one detail the 5070 gets correct which is matching dial and movement beats. The 5170 makes the mistake of a mismatched dial subsecond indice. Why can't they get this right is beyond me..perhaps its an aesthetic thing. Another culprit is the Speedmaster Moonwatch using the Lemania 1861 movement - the movement is 3Hz but the dial is meant for a 2.5Hz chrono (which, is what the old Lemania 321 beats at!). I believe they do this purely to preserve the history/aesthetic of the original dial - despite the inaaccuracy that happens after swapping out the movement to the simpler, cam-based Lemania.
Note that, the 5370 "cheats" by not having any subsecond indices at all! So we can let that slide.... (its also a 4Hz movement, since its based off the 5170 movement).
Regards,
skyeriding