[time-nuts] Cesium Mechanical Chronometer

Sun Feb 2 03:39:24 UTC 2020

I understand, though I was thinking a small coil could be placed
inside the case near the balance wheel. Worst case it seems fully
reversible (depending on mounting the coil and a small hole for the
wires to come out) and worth a try.

On Sat, Feb 1, 2020 at 10:31 PM Bob kb8tq <kb8tq at n1k.org> wrote:
>
> Hi
>
> Keep in mind that these particular chronometers were designed (as best as
> was possible) to be impervious to outside influences. Mag fields, rocking back
> and forth, orientation changes all should have whatever the lowest impact you
> could make them have.
>
> Bob
>
> > On Feb 1, 2020, at 9:58 PM, Ben Bradley <ben.pi.bradley at gmail.com> wrote:
> >
> > I'm wondering about the balance wheel, if it's ferromagnetic (has iron
> > or steel in it, which would probably make this idea not work), or if
> > it's perhaps all aluminum or similar non-magnetic material. Adding a
> > constant magnetic field from a coil and electric current source would
> > provide a magnetic induction-induced drag on the balance wheel and
> > slow it down (hopefully not so much that it stops). Setting the
> > chronometer to normally run slightly fast would allow it to be slowed
> > down and regulated by the strength of the magnetic field on the
> > balance wheel.
> >
> > On Sat, Feb 1, 2020 at 3:06 PM Bob kb8tq <kb8tq at n1k.org> wrote:
> >>
> >> Hi
> >>
> >> If the idea is to generate a rate card and keep it up to date ….. I think that
> >> can be done with just the GPS. The CSAC really does not add a lot that
> >> I can see to that case.
> >>
> >> Of course I may have (yet again) missed something ….
> >>
> >> ======
> >>
> >> The very standard  / “old school” approach for this is a microphone on the case
> >> of the M21. These days feed the mic preamp output into a cheap micro along
> >> with the GPS info and away you go.  Spit the results out to a little OLED display
> >> maybe …..
> >>
> >> Bob
> >>
> >>> On Feb 1, 2020, at 1:39 PM, Tom Bales <tob.starhouse at gmail.com> wrote:
> >>>
> >>>>
> >>>> Many thanks for everyone's response on my cesium-synchronized mechanical
> >>>> chronometer project.  I'll keep the group informed of progress.  Some
> >>>> responses to your questions and suggestions:
> >>>
> >>>
> >>>  - My current plan is to use a chronometer that has been adjusted for
> >>>  rate and is close to dead-on.  Of course, they're never dead-on, and that's
> >>>  why keeping track of the rate is important.  I haven't dismissed the idea
> >>>  of actually disciplining the chrono from the CSAC, but since this chrono's
> >>>  rate adjustment involves screws on the balance wheel (it has a free-sprung
> >>>  helical balance spring without any means of adjustment), that would be a
> >>>  great challenge.  Perhaps the best would be for the CSAC system to maintain
> >>>  a "rate card" of the chronometer, so that when all the electronics fail,
> >>>  and the user is left with only the chrono, at least they would have a
> >>>  really good knowledge of its rate and variation.  Doing so would require a
> >>>  feedback signal from the chrono, which could be acoustic or photoelectric.
> >>>  The electronic rate card could be updated now and then by turning off the
> >>>  sync impulse to the chrono and listening for the ticks to move relative to
> >>>  the 1pps.
> >>>  -  The chrono would need a bigger box in order to incorporate the
> >>>  CSAC/GPS system, microcontroller, and--the biggest part--backup batteries.
> >>>  That's part of the fun, and I'm thinking to mount the gimballed chrono in a
> >>>  purpose-built enclosure that will hold everything.  Connections to the
> >>>  chrono will have to be very flexible FFC or silicone wire.
> >>>  - I thiink auto-winding is a definite requirement.  The engineering
> >>>  challenge is to couple a small gearmotor to the winding system without
> >>>  disabling the manual-winding system that uses a ratcheted key.  Winding
> >>>  noise should be short in duration, so it probably won't affect the time
> >>>  sync.  People have wound chronos by turning them upside down in the gimbals
> >>>  and poking a key through a hole for a long time without any  big issues.
> >>>  - Coupling to the chrono balance and escapement might be difficult, or
> >>>  it might be easy.  If it takes hours or days to synchronize, that's OK, I
> >>>  think.  My guess is that anything that generates a slight impulse in the
> >>>  direction of the escapement detent or a torque pulse to couple to the
> >>>  balance will work well enough--a tiny little linear or rotary
> >>>  electromagnetic actuator should work.  We'll see.
> >>>  - The Hamilton M21 chrono beats at 2Hz, so driving it with a 1pps signal
> >>>  will probably work fine.
> >>>  - The idea that TVB suggests of disciplining the CSAC to match the
> >>>  chrono is fascinating, indeed.  Hadn't thought of that one.  It would be
> >>>  the easiest way to keep the chrono and CSAC in sync, and it would still use
> >>>  the traditional rate-card method of keeping track of the actual time.
> >>>  Hmmmm.
> >>>  - Yes, the CSAC modules are expensive!  Over $5k currently.  It seems
> >>>  like during the evaluation period the company sold them "at a discount" in
> >>>  order to build applications and sales (or so the court documents say).  Let
> >>>  me know if anyone sees a gyneesium one on *bay.  I thought long and hard
> >>>  before buying it, but idle hands are the devil's cash register.  (Oh,
> >>>  oh!--now I have an excuse to buy an HP 53230!)  In my initial measurements
> >>>  of rate (after GPS disciplining for 24 hours) the CSAC freewheels within
> >>>  1.7ms/yr.  Probably good enough.  Needs longer testing.
> >>>  - The M21 has a single balance wheel consisting of an Invar spoke and a
> >>>  stainless steel ring (it was Hamilton's magical way of doing temperature
> >>>  compensation to match the balance spring.  The Russian knock-offs have a
> >>>  standard bi-metal split balance wheel.  The Hamiltons beat just about
> >>>  anything in performance.  Besides, "Murica!".
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> >>
> >>
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