[time-nuts] Cesium Mechanical Chronometer

[Dana Whitlow]

I believe that attempting to tune any resonator by damping (Q-spoiling)
said resonator by
adding drag would be a mistake.  It would not likely be very effective at
tuning, and has
great potential for degrading the frequency stability.  Hence my preference
for injection
locking by rocking about an axis parallel to the balance wheel's axis of
rotation.  If there's
only a single balance wheel, the watch should be responsive to this motion
regardless of
claims to the contrary.

For several years I've had grandiose notions of locking a grandfather clock
to a stable
external reference, but think it will be a tougher nut to crack subject to
constraints against
modifying it at all.  Perhaps mounting it on a motor-driven horizontal
translator?

Dana


On Sat, Feb 1, 2020 at 8:59 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!".
> > > _______________________________________________
> > > time-nuts mailing list -- time-nuts at lists.febo.com
> > > To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > > and follow the instructions there.
> >
> >
> > _______________________________________________
> > time-nuts mailing list -- time-nuts at lists.febo.com
> > To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > and follow the instructions there.
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>