28,800

Thread: 28,800

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  1. #1

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    28,800

    Apart from exotica like the Zenith El Primero, why do the majority of automatics run at 28,800 ? Is it some kind of magic number like the meaning of life or just a handy figure so cogs are easier to come by?

  2. #2
    Member dbluefish's Avatar
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    Re: 28,800

    In physics, the ideal number is 57,600bps but due to the natural limitations inherent in the material used in watches, the maximum was determined to be 36,800, and with the built in errors associated with production that was further limited to 28,800. Many very good watches are operating at 21,600 but that is their choice. Manual wind, due to the losses associated with hand winding and the natural curve of diminishing returns(as the spring winds down)will often be no more that 18,600bps.

    If the watch makers shifted to more exotic materials like ceramic/carbon fibre, they could achieve very close to the 57,600bps but Serrano's Law holds that for carbon fibre/ceramic to be viable it has to be at least 1mm in thickness so our watches would be quite large.

    I think the accuracy of our automatics using the 28,800 figure is quite remarkable. Quartz, which has an oscillation rate 10 times greater that the spring used in automatics, can thus be almost loss free in it's accuracy. But then until the spring drive, quartz had to move in jumps, not smoothly, and this was an aesthetic negative.

    Maybe in the future, we will find a material that will allow a greater bps.

    we will see.

    paul
    Doxa 600T Clive Cussler edition
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  3. #3
    Member HelloNasty1's Avatar
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    Re: 28,800

    Quote Originally Posted by dbluefish View Post
    In physics, the ideal number is 57,600bps but due to the natural limitations inherent in the material used in watches, the maximum was determined to be 36,800, and with the built in errors associated with production that was further limited to 28,800. Many very good watches are operating at 21,600 but that is their choice. Manual wind, due to the losses associated with hand winding and the natural curve of diminishing returns(as the spring winds down)will often be no more that 18,600bps.

    If the watch makers shifted to more exotic materials like ceramic/carbon fibre, they could achieve very close to the 57,600bps but Serrano's Law holds that for carbon fibre/ceramic to be viable it has to be at least 1mm in thickness so our watches would be quite large.

    I think the accuracy of our automatics using the 28,800 figure is quite remarkable. Quartz, which has an oscillation rate 10 times greater that the spring used in automatics, can thus be almost loss free in it's accuracy. But then until the spring drive, quartz had to move in jumps, not smoothly, and this was an aesthetic negative.

    Maybe in the future, we will find a material that will allow a greater bps.

    we will see.

    paul
    I believe it is actually BPH (beats per hour), unless I am not understanding your definition of BPS (guessing: beats per second).

    Anyway, it still amazes me to have something mechanical basically alive on you wrist.
    Better to regret something you have done, than something you haven't done...





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  5. #4
    Member dbluefish's Avatar
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    Re: 28,800

    Actually I was just pulling your collective legs, as an old saying goes. I have no idea how any of it really works but it is amazing that it does!

    paul
    Doxa 600T Clive Cussler edition
    Breitling Superocean A17345
    Omega 2531.80
    RGM Sea3 Custom
    Ocean 7 LM3 #119

    VINTAGE :

    Zodiac Astrographic 2000
    Zodiac Sea Wolf(1964)
    LeCoultre Master Mariner (1970)
    Hamilton Thinmatic (1968)

    Place of honor:

    my '80's Seiko 5 which has been through the mill and still runs and tell adequate time.

  6. #5
    Member lysanderxiii's Avatar
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    Re: 28,800

    The faster the beat the less the variations in the duration of the beat will affect accuracy. But, the faster the beat the wear and tear on the bearings increases and you start to get problems with keeping the oil in place.

    28,800 bph is a good compromise between speed (and therefore consistency in timing) and wear and oiling issues. 21,600 bph further reduces the stress on the parts and oil, with little affect on accuracy.

    36,000 bph is preferred by stopwatch movements because it gives 1/10 second resolution. 28,800 only gives 1/8 second and 21,600 gives 1/6 second resolution. Since stopwatches do not run continuously, wear and oiling issues are reduced to manageable levels. You will note that the Primero requires special oiling instructions.

  7. #6
    vandice
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    Re: 28,800

    The mechanical watch is affected by gravity (and similarly, acceleration). That is why COSC tests the watch in 5 positions because the timekeeping will be different at different positions.

    The higher the beat, the better the stability of the movement when under the influence of external forces (similar in principle to a spinning top. The faster it spins, the more vertical it stays). So with a higher beat, you'll get:

    1. a more stable rate in a variety of positions/wear pattern.
    2. a smoother sweep second.

    Conversely, you'll have to expend more energy and use finer/more gears to drive the movement, not to mention an upgraded mainspring with sufficient power to keep the power reserve within 40 hrs.

    All these cost money (the gears, the mainspring). Coupled with the added maintenance costs (the 36000 beat does have twice the wear of an 18000 beat run for the same amount of time) and the fact that most mechanical watch owners don't care for accuracy (it may have become popular if quartz hasn't been invented), this makes it probably too exp. for mid-tier use.

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