On day 73 of the virtual pocket watch museum, in responce to Tonny's posting
of a steel cased IWC Pocket Watch, I shared this this steel cased watch with
you, and laid out a challenge to Jeroen. In short, can we save this bit of IWC
history and restore it ?
[Rust Bucket - See it here](/t/virtual-pocketwatchmuseum-
day-73-cal-57-steelandgold/31939/post/280693/)
Being the watchmaker he is, he accepted the challenge.
During the life time of the project, come good times or bad (as is the case
with most restoration projects that start out like this), we will share the
progress, trials and tribulations with you.
This will be in the form of a photo essay.
Day # 3 - Getting the movement back to former glory
So I'm privelaged and am sometimes allowed to watch (opening my mouth while
Jeroen has a miniture screwdriver in his hand....often costs me money so I've
learnt to be quiet). Before he even has unscewed a single screw or removed a
bridge he seems to be examing the then still complete movement (sans dial)
from all angles. Im perplexed, he has seen many a Cal. 57 before - why the
need to scrutinise it like this?
Then, I hear "Wow - dat is mooi", and taking it as an invitation to speak, I
ask "wat? " This is Dutch and translates to believe it or not "Wow - that is
nice" to which I responded "whats nice?".
His responce was (translated) to say "the Maltese Cross is still there!"
And indeed later when he has it strippd down further I get a birds I view of
this small little piece of metal which so pleases a watchmaker of repute.
Yes, there is is in all it's glory - the Croix de Malte , a small Gear
(actuall device) which is fixed on the barrel and is designed to both help
prevent overwinding, as well as rumoured to reduce the amount of wheels
necessary for winding the watch.
The most common stopwork in wristwatches is the Maltese cross. It is named
after a wheel the form of a cross with several arms. All arms except one have
a concave end. The Maltese cross is moved by a wheel with one finger fixed on
the axis of the barrel. This finger fits between the arms of the Maltese cross
while the arm of the Maltese cross fits into openings in the finger wheel on
both sides of that finger. This device will turn until the one longer arm
which does not fit into the openings of the finger wheel blocks the mechanism
and thus the unwinding of the barrel and prevents overwinding the mainspring.
While this mechanism does work well, it also has its disadvantages. The
Maltese cross is switched step by step, thus influencing the power delivered
by the barrel. The stopping is effected by metal sliding on metal, a process
prone to variations, again influencing the barrel.
By design, the bearing of the Maltese cross is fragile which is critical if
the barrel is fully wound up and all the power of winding the watch is
transferred onto the Maltese cross when it blocks. The force that comes to
bear in this instance is several times greater than the force produced by the
barrel. To avoid these problems, Andreas Strehler designed a free running
stopwork with only a minimal and continuous friction and without any
discernible influence on the precision of the watch. It's functioning - as
with most great inventions - is amazingly simple:
To the barrel-arbor is fixed a toothed pinion which continuously moves a gear
ring with inner toothing. This gear ring is embedded but moving freely in an
eccentric cut out of the barrel. The pinion has one longer tooth as a blocking
finger. This blocking finger is stopped by the gear ring both before the full
winding and before the complete unwinding of the mainspring. The gear ring has
enlarged tooth spaces allowing the blocking finger to pass freely. The reduced
tooth spaces of the gear ring only let the normal teeth of the pinion but not
the blocking finger. The axial play of the gear ring is limited by the
clearance between barrel and ratchet-wheel. Thanks to Andreas Strehler Master
Watch Bulder for the above clear explanation and graphic.
I'm happy that my watch still has it's maltese cross. Did I say still? Yes, I
did becuase Jeroen goes on to explain to me, that actually on the majority of
these old watches that have been serviced a multiple of times over the years,
that the maltese cross is simply missing. Missing? Yes delibertly left out by
the watchmakers when re-assembling the movements! Apparently this mechanism
requires a lot of oiling, and the watchmakers want to see as little as needed
oils on the movements, and then also exactly (and only) at the place they want
to see it!
But I digress ....we really should look to what's Jeroen busy with.
Seems like lots of gears are coming off that movement now.
But why is this taking so long? Well simply this - each and every part is
carfully inspected and it seems that one or two of them are being put to one
side (ugh... what does that mean?).
Go take a look here :
One by one each individual part is scrutinized
The parts are coming off the mainplate.
Lots of parts...
See those three vital parts in the centre there?
Well these are the three components to the left of this educational diagram
below, which depicts the basic parts of a pocket watch movement (or for that
matter - any fine mechanical watch movement) - namely the Balance, entire
Pallet Fork assembly and the Escape Wheel. The Pallet (what I call the pallet
fork, is in the centre of the picture above and Iyou can see in the lever
escapement, a small
parallelepiped (big word
there! ... had to look it up myself) of
[ruby](www.hautehorlogerie.org/en/encyclopaedia/glossary-
of-
watchmaking/s/ruby-1/),
[sapphire](www.hautehorlogerie.org/en/encyclopaedia/glossary-
of-
watchmaking/s/sapphire-1/) or garnet, set in each of the lever's arms; one is
the entrance pallet and one is the exit pallet. Jeroen sometimes spends hours
on this part at the end of the projects - I hope not needed this time.
And the first thing you want to take notice of here, is that on the actual
balance itself in the photo you can see clearly the bimetallic balance. Heres
a clearer zoom of that.
This was the hight of haute horologe in those years.
A bimetallic balance is a screw balance wheel made of brass (on the outer rim)
and steel (on the interior rim). You can clearly see this in the zoom photo
above. Because of the differing temperature coefficients of these two metals,
they react differently under the influence of temperature. The steel
hairspring used with these bimetallic balances is so thin it too expands and
contracts under the influence of temperature. The fineness of the steel spring
causes it to behave more like brass, which is far more reactive than steel (it
has a higher temperature coefficient). In warm temperatures the brass will
expand and pull the arms of the bimetallic balance out. This mirrors the
effect an increase in temperature has on the steel hairspring. So when the
temperature rises the spring AND the wheel expand so that they are still
working in harmony. Similarly, under cold temperatures, the brass contracts,
pulling the arms in (see diagrams below) to mirror the reaction of the
hairspring. The steel component of the wheel is thick enough to not react to
temperature changes (unless they are incredibly extreme). To this end it acts
as a base against which the brass can push or pull. Without the steel
component of the wheel, the brass would be too reactive and flimsy and
timekeeping would be atrocious.
Bimetallic balances are expensive and have fallen out of favour due to the
discovery and refinement of new materials that boast a much lower temperature
coefficient such as Elinvar springs, Glucydur balance wheels and, more
recently, silicon.
IWC today mostly use Gluydur for their balance wheels.
And as for Jeroen, well in the meantime he has sorted all those parts and put
them into individual mesh containers
Ready for the second cleaning of the individual parts (well hopefully all as
I'm not to sure what happened to that smaller heap of a couple
of parts that Jeroen put to one side during the strip down).
Now, some of you have asked what descions have been made as to the overall
direction of the project. Some answers.
Dial: So, we already know that the shattered dial on the watch is original
to it. Watch left Schaffhausden with it. I so do like that inner 13/24 hour
time ring (and in fact people in the know in Schaffhusen subsequently have
told me that they have not seen that blue touch themselves ever before on
another pocket watch. So its a rare dial.
In extended discussion with Jeroen last night, we dicided on a two step
approach. The restoration of the watch will be done in the first instance
using the replacement dial I shared with you in Day #2 of this project.
In parallel I've started to run the mini side project to see if we can get the
enamel dial restored.
So today, I started that process - which begins with getting all dirt and
flaking glass spliters off the dial. Here you can see that someone had clearly
tried some repairs on the dial previously and the ink is begining to drift off
the dial at the 7 and 11 positions. Tomnorrow it will go off to an independant
dial restorer to see what can be ackomplished.
The Case: Well, as you already know from the previous post on the subject
of the rust bucket itself, Jeroen and I had a diference of opinion. This
discussion has been ongoing, and in the end I conceded. So, the final desicion
on the case is to get it totally rust free, and then for Jeroen to redo the
bluing of the original steel case complete, retaining it 's character /
patina
received from years of abuse by moisture.
Both Dial and Case progress will form part of a future post.
