SECTION 2

TWEAKING THE MARK XII: PART 2.3

ADJUSTING THE MARK XII/887

by Walt Odets

7.

HEIGHT=”302″ ALIGN=”RIGHT” BORDER=”2″ NATURALSIZEFLAG=”3″ ALT=”Cock on work clamp”>The dial-up rate did, as expected, increase
more than dial-down, but the spread between the two was still
too large. Now, the dial-up amplitude was also dangerously high
(threatening knocking with any activity), but the previously
low dial-down amplitude
problem seemed to have spontaneously corrected. Changeable factors
too small to see even under very high magnification–including
debris in pivots, differences in lubrication, or tiny, imperceptible
changes in spring and regulator geometry–often play a role in
precise adjustment. The variability of too many measured parameters
now suggested that the escapement needed some examination and
reworking. I removed the balance cock, balance and spring from
the watch. An examination of the lower balance pivot revealed
no visible defects at 35 power magnification, but I used a pivot
polishing tool and a bit of jewelers rouge on a piece of pegwood,
to polish the pivot. I expected this to improve dial-down amplitude.
With the balance spring out of the watch, the outer coil (before
the regulator sweep) looked a bit out of center, and I reshaped
that, as well as the regulator sweep (which was repositioned
by the adjustment of the outer coil). I expected the horizontal
centering to improve positional performance. Then, having reinstalled
the balance cock in the movement, I reregulated for rate and
beat on the timer, and the figures were finally promising:






































  DIAL UP DIAL DOWN CROWN DOWN CROWN LEFT CROWN UP (CROWN RIGHT)
AMPLITUDE  306 302 265 281 286 269
 RATE -2 -2 +2 +1 -1 +2
BEAT ERROR 0.2 0 0.1 0.1 0.1 0.2

WIDTH=”238″ HEIGHT=”164″ ALIGN=”LEFT” BORDER=”2″ NATURALSIZEFLAG=”3″
ALT=”Balance poise cut”>The amplitude figures were close to or
better than original factory figures. The maximum rate difference
in five positions was now four seconds, although that spread
fell between dial-up and crown-down. Factory adjustment showed
only half that (two seconds) on these two critical positions. My crown-left
adjustment, the second most important vertical position (sitting
with your arm on the arm of a chair), showed a three second difference
from dial-up, identical to the factory’s. My crown-up was within
one second of dial-up, compared to the factory’s zero difference.
This was not a bad adjustment, but it was not as elegant as the
factory’s adjustment, despite the marginally smaller total spread.
It did not represent much of an improvement, if any.

8.

WIDTH=”266″ HEIGHT=”229″ ALIGN=”RIGHT” BORDER=”2″ NATURALSIZEFLAG=”3″
ALT=”Horizontal centering”>The factory point of attachment of the
balance spring at the collet (see “Tweaking the Mark XII,
Part 2.2″), which I had not changed, should have provided
the fastest vertical rates in the crown-left and crown-up positions.
My last reading showed the opposite of these expected figures,
with slightly higher rates in the crown-down and crown-right
positions. I thus suspected that there was still some horizontal centering error in the
spring and very slightly adjusted the regulator sweep
and dog leg to attempt improvement on the centering. Because
the regulator sweep must remain stationary to accommodate the
regulator, any adjustments made to it or the dog leg displace
the entire rest of the spring. The illustration right,
shows how adjustments of the spring at 1, 2, and
3 cause displacements at 4 and 5.

These very, very slight adjustments, and
a reregulation of rate and beat, finally brought the watch into
an adjustment that clearly improved on the original factory figures:






































  DIAL UP DIAL DOWN CROWN DOWN CROWN LEFT CROWN UP (CROWN RIGHT)
AMPLITUDE  311 293 281 279 282 273
 RATE +1 0 +1 +1 -1 +2
BEAT ERROR 0 0.1 0.1 0.2 0.1 0.1

All adjusted positions are with two seconds
of each other, and, most significantly, the three “important”
positions (dial-up, crown-down, and crown-left) are identical.
In the ever-quirky way of micro-mechanics, dial-down amplitude
was still lower than dial-up, but this was no longer producing
a higher dial-down rate–probably because of changes in centering
of the spring. Amplitude in the three adjusted vertical positions
was essentially identical, with the (more expected) result that
these positions were HEIGHT=”230″ ALIGN=”RIGHT” BORDER=”2″ NATURALSIZEFLAG=”3″ ALT=”Watch on Cyclomatic”>very
close in rate. The crown-up rate suggested that there was still
some minor residual horizontal decentering of the balance spring,
but there always is. One would not advisedly attempt to
correct for such a small error. It would be too easy to introduce
much larger errors.

9.

It now remained to check adjustments at
partial states of wind, and to check rate in actual daily use.
I placed the Mark XII, fully wound, on a Cyclomatic-S timer,
which holds the watch at a 45 degree angle, thus splitting the
difference between dial-up and various vertical positions. But
I removed the rotor to prevent automatic winding. After 22 hours,
the watched had gained two seconds and showed the following timer
readings:






































  DIAL UP DIAL DOWN CROWN DOWN CROWN LEFT CROWN UP (CROWN RIGHT)
AMPLITUDE  277 273 255      
 RATE +10 +12 +13      
BEAT ERROR 0.1 0.3 0.3      

Lower amplitude figures (from lower mainspring
tension) were clearly evident. And, with lower amplitude, came
the expected faster rate–although these figures seemed
a bit too high. Beat had WIDTH=”297″ HEIGHT=”156″ ALIGN=”LEFT” BORDER=”2″ NATURALSIZEFLAG=”3″
ALT=”REgulator boot”>also drifted some. The spread between dial-up
and crown-down was now three seconds. Any residual faults in
the escapement are always more influential with lower amplitude
because irregularities have a greater influence on a shorter
swing. It was also likely that rate had “settled in”
and need a little reregulation. So I fully wound the watch before
any adjustments to compare it to the last fully wound test:

 






































  DIAL UP DIAL DOWN CROWN DOWN CROWN LEFT CROWN UP (CROWN RIGHT)
AMPLITUDE  306 306 291      
 RATE +4 +6 +5      
BEAT ERROR 0.2 0.3 0.2      

10.

Even at full wind, the rate had picked
up a bit, and beat was still slightly off. Reregulation of rate
and beat yielded:






































  DIAL UP DIAL DOWN CROWN DOWN CROWN LEFT CROWN UP (CROWN RIGHT)
AMPLITUDE  301 305 283 279 280 283
 RATE +1 +1 +4 +3 +2 +2
BEAT ERROR 0.1 0.1 0 0.1 0 0.2

11.

Over the next 24 hours, I wore the watch
for 12 hours, during which it lost 2 seconds. It sat dial up
for 12 hours, during which it gained 0.5 seconds. The total 24
hour rate in use produced a loss of about 1.5 seconds.

12.

WIDTH=”178″ HEIGHT=”208″ ALIGN=”RIGHT” BORDER=”2″ NATURALSIZEFLAG=”3″
ALT=”Balance arm and regulator”>At the end of the second day,
12 hours in wear, 12 hours dial-up, the watch had gained one
second and stood at a total loss of 0.5 seconds.

13.

The next 24 hours was spent back on the
Cyclomatic and produced a gain of 2.5 seconds, for a total gain
of 2 seconds for the three day period.

14.

The Mark XII spent the next three days
on the winder, and gained 32 seconds during this time. So I decided
to look at it on the timer again:






































  DIAL UP DIAL DOWN CROWN DOWN CROWN LEFT CROWN UP (CROWN RIGHT)
AMPLITUDE  311 300 246 289 281 285
 RATE +6 +8 +11 +9 +8 +7
BEAT ERROR 0 0.2 0 0.2 0.2 0

WIDTH=”180″ HEIGHT=”213″ ALIGN=”LEFT” BORDER=”2″ NATURALSIZEFLAG=”3″
ALT=”Weight on index”>The crown-down position was once again
showing somewhat low relative amplitude and subsequent higher
rate (now 5 seconds from dial-up). And the crown down position
was, once again, too fast. In the crown- down position the weight
of the spring places more pressure on the index (rather than
the boot) and I wondered if some irregularity in the index might
be binding the spring, making it effectively shorter, and increasing
rate.

15.

I thus burnished the inside surface of
the index with a very fine, polished steel needle, and slightly
opened the spread between index and boot (to slow the vertical
positions slightly). Because the watch had spent it’s three days
on the winder in a safe, I also demagnetized it with the case
back still off.






































  DIAL UP DIAL DOWN CROWN DOWN CROWN LEFT CROWN UP (CROWN RIGHT)
AMPLITUDE  302 305 284 285 279 280
 RATE +1/+3 +1 0 +4 +2 +2
BEAT ERROR 0.2 0 0 0.1 0.1 0.2

WIDTH=”350″ HEIGHT=”137″ ALIGN=”RIGHT” BORDER=”2″ NATURALSIZEFLAG=”3″
ALT=”Tape with chatter”>On this reading, the evenness of amplitude
across horizontal and across vertical positions is remarkably
good. The dial-up rate was slightly unstable, however, and the
timer clearly showed why. As shown at right, there
was now some chatter of the spring dial-up, due to some irregular
interaction between spring and regulator.

16.

I subsequently adjusted the regulator index
to close it slightly, and made very slight adjustments to assure
that the regulator sweep was as perfectly vertical as I could
make it. If the balance spring is not absolutely vertical as
it passes between index and boot, one edge of the spring can
contact one of the regulator parts and produce chatter and uneven
rate. I then backed off the Triovis screw to slightly reduce
the overall rate. These provided my final figures in adjustment
of the Mark XII/887. They may be compared to the original factory
figures below the first table.






































FINAL DIAL UP DIAL DOWN CROWN DOWN CROWN LEFT CROWN UP (CROWN RIGHT)
AMPLITUDE 313 303 285 293 292 291
 RATE +1 0 +2 +3 +1 +3
BEAT ERROR 0.1 0.2 0.2 0.3 0.2 0.1






































 FACTORY DIAL UP DIAL DOWN CROWN DOWN CROWN LEFT CROWN UP (CROWN RIGHT)
AMPLITUDE  292 288 282 263 273 275
 RATE +7 +5 +5 +10 +7 +6
BEAT ERROR 0.2 0 0 0.1 0.1 0.2

DISCUSSION

HEIGHT=”295″ ALIGN=”LEFT” BORDER=”2″ NATURALSIZEFLAG=”3″ ALT=”Timer tapes, final”>In
daily use, my final figures provide a watch that runs within
a second or two a day, generally losing a second or so during
the day (full wind, high amplitude) and picking it back up at
night (partial wind, lower amplitude). Occasionally checking
against a reference, the watch is plus or minus one second, with
no longer-term drift in either direction. As I rarely wear a
single watch for more than a week or two, I do not have impressions
beyond this period.

The improvement over original factory figures
is a small one in terms of utility, but substantial in terms
of watch adjustment. My adjustments achieved a total spread over
the five positions of three seconds (versus the factory’s five
seconds); a dial-up / crown-down discrepancy of one second (versus
the factory’s two seconds); and a dial-up / crown-down / crown-left
discrepancy of two seconds (versus the factory’s five seconds).
Including the unadjusted crown-right, my adjustments provided
a spread over the six positions of three seconds, compared to
the factory’s five. WIDTH=”270″ HEIGHT=”242″ ALIGN=”RIGHT” BORDER=”2″ NATURALSIZEFLAG=”3″
ALT=”Spinning balance wheel”>

Is such “tweaking” worth the
considerable work involved? That all depends on why you’re doing
it. As an exercise in watch craft–and sometimes witchcraft–it
can be very satisfying. As a practical matter, it is certainly
not worth the cost. The precision of the adjustments I made provided
a watch that–so far–hardly ever needs resetting. But
following the next cleaning, it will have to be done all over
again. And, in the meantime, a good hard knock may well undo
much of my work by forcing a distorting excursion of the balance
spring.


RETURN TO SECTION 1 OF THE ARTICLE

 
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