Ophiuchus
166
some basic rules then
for ANY mechanism that causes movement of any part in contact with another part- there WILL be wear if it is running.
Even if lubricated, there will be wear eventually. Especially with setting mechanism parts.
With that in mind, all mechanical chronographs (with the exception of very few that have their own gear trains and
dedicated balances, such as a bomb timer, which is essentially only run for short intervals, and doesn't keep time,
so much as record a passed time accurately) work in one fundamental way, with a fundamental flaw:
They interface with the timekeeping, or going train, of the movement they work in. Meaning, they are attached in some way
physically to one of the arbors of the gear train. Disengaged, they do not hurt timekeeping. Engaged, no matter the type,
they will cause a drop in amplitude of the balance, if only a little when adjusted well.
So, your timekeeping is less isochronous, and less accurate with a
chronograph running. Maybe a very small amount, but it's there.
Horizontal clutch chronographs (traditional style) have more independent
parts to keep turning from that one gear in the timekeeping
train, and because they use meshing gears, there is more chance for slop
of the chrono hand, and until they become fully engaged,
there is a slight lag of the chrono hand. These are "pretty" mechanisms to look at.
Vertical clutch chronographs (mostly Seiko) actually have more surface contact of components when engaged, so there is almost no
lag at all for the chrono hand on engagement of the chrono, and less
drag on the timekeeping train because of less components, and
more efficient design. Not "pretty" to look at, but works more efficiently.
Vertical clutch chronos, to my knowledge, are not "slipping" when disengaged. There is a small gap between the two pressure plates
that engage to touch only when running. No wear, except to the timekeeping train parts that are turning as they hold the vertical
clutch parts. The engagement with vertical clutch chronos is much more solid than horizontal types- so hand slipping would be LESS likely.
Usually, when a hand slips, it is due to extreme shock of resetting with the inertia of the hand itself, when the hand was not
properly checked for tight fit at service. In this case, a shock to the whole watch, from dropping, could also cause this, but only
if hand is not proper tightness.
On the 7750- you are right, both pivots for the minute counter hand and gear are not jeweled, so they would have more wear than
other types if constantly left running, compared to jeweled pivots.
Really, constant running of any chrono just causes your timekeeping to be potentially less accurate due to the drop in balance
amplitude, causes much decreased watch run time between winds using much more mainspring reserve, and will cause excess
wear to it's components that slide across others when moving, more with a traditional horizontal clutch chrono than with a vertical
clutch chrono, but on both to some degree.
It's just not needed, running them all the time. But then, you always see this from some people that like a big moving second hand.
It's just no benefit at all to leave them running constantly.
-O
This message has been edited by Ophiuchus on 2014-01-16 09:46:58
Keep chronograph running
This topic has indeed been discussed some months ago, but it is an interesting question,
Here is what I learned ...
Generally I would assume that a mechanical system ...
some basic rules then
Obviously, there's no benefit to running the chrono constantly...
the issue is complicated, but perhaps subtle enough as to not be so important
Thank you so much John
