High beat/low beat question

[rionrlty]

I gave this reply to a comment received (below) regarding my recent review in Breitling forum of my New Navitimer 01, which has the (so called) “low beat” 21,600bph A7750 movement.

As it regards a subject that I would like to know more about I am starting a new string here in hopes that some of you more knowledgeable folks will comment on the subject.

Despite the fact that most seem to believe that this movement has a noticeably more stuttering second hand movement (it actually does seem to), because of the lower beat count, I am skeptical and spell out my reasoning below. Is it really that simple or are there other factors at play here?
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Yes, there is a “low beat” version of the 7750 in both the Chinese version as well as the older gen ETA versions, however the term “high beat” has always been a relative term.

I’m not an expert but my understanding is that there were many (high end) watches prior to the 1960’s, with accurate chronometer grade movements, which only ran in the 10-11,000 bph range.

I still have a Bulova automatic that I purchased new in 1965, which I believe runs in this range. Curiously the large second hand sweeps smoothly and the watch has always been quite accurate, even though it was only serviced once about 30 years ago and it was not treated gently during that time.

I believe that one of the first “high beat” movements was produced in the 1960s by Seiko. It only ran at 18,800bph. A few years later they produce one that ran at 36,000bph but ran into reliability problems with it. So, it would seem that, while the newer 7750 runs at 28,800, the older version at 21,600bph (while it is slower), in the long term scheme of things, should not be referred to as a “low beat” movement, only less high than the newer version.

The mystery to me is that when a true “low beat” (11,000bph) movement can reach chronometer grade accuracy, with a smooth running second hand, then why is the high beat version so important?

The second hand on my new Navitimer 01 (21,600bph) is clearly not as smooth as the one on my fighters, which has a Breitling B-13 caliber (ETA7750 based 28,800 bph) movement. What I can’t seem to figure out is why the second hand on my old Bulova, which runs at less than half that speed, appears just as smooth as the 28,800bph version. Could there be something else at play here contributing to the stutter.  I have heard much about the Chinese movements being dirty.  Could this be a factor in the stutter of the second hand?  Also, it would seem to me that the higher the beat the faster that parts, related to the balance and escapement, would wear out.

I would love to hear others opinions on this.

[torobravo]

28.8k for 7750 and 21.6k for 6497 manual is high beat