Tuesday, February 25, 2014

Finished Escapement Model

Finished line draft
Today I finished the CAD version of my escapement.  This was done using Google sketchup.


This week we are doing a drafting module in class.  The old Chicago School of Watchmaking program has a 'drawing of the Swiss lever escapement' chapter so we are following the steps outline in that program to complete a reproduction of a standard Swiss lever.  In class I have been working with traditional drafting equipment: pencil, compass, square, protractor, etc. 

However I also have been working with CAD software which makes the process much more accurate and much cleaner.  See the pictures below.

Here is the CAD layout for the escape wheel

CAD escape wheel finished.  Next step is to layout the fork, pallet and roller.

Sunday, February 16, 2014

Power Flow

As a watchmaker it's important to understand how power is transmitted in a watch.  This enables one to more easily troubleshoot problems that may arise in the system.

A common question that comes up on tests in class and in certification exams deal with how power is transmitted in a watch.  Sometimes it's difficult to create a mental picture of these systems as they are condensed and typically inhabit 2 sides of the watch.

For visualization and study I have constructed a flow chart which is helpful in understanding the movement of power in the system.  This particular chart is for a 2824-2 and watches of similar design sans the automatic and calendar systems.

Friday, February 14, 2014

7751 Chronograph Components Assembly

Today I finished the overhaul of the 7751.  It just takes a bit longer than the 7750 because of the extra parts on the dial side.  Overall the process took around 5 hours to complete.  These practice sessions are important because we have to service 7750 chronographs for both the SAWTA 4 and CW21 testing.  Next week I will be working on a 7750 installed in a Tudor case that has been thoroughly mucked up by my instructor.  I will try and post results.

Chronograph base components technical documentation
Here is the cam jumper and cam installed.  The cam synchronizes and controls the functions of the chrongraph.
Here the lock and the ratchet wheel driving wheel have been installed
Chronograph bridge, installed
Here is the operating lever spring, lubricated and installed.  This is what pushes back on the chronograph buttons when they are depressed
Here is the operating lever, notice some more of the white grease on the end where it interacts with the cam
Testing the operating lever and its interaction with the cam

The next phase

Here the chronograph and minute counting wheels have been installed along with the tiny oscillating pinion which is the disconnect between the watch and the chronograph mechanisms

Here is the clutch, reversing wheel and reduction wheel installed

The automatic bridge, installed.  The hammer has also been added before the bridge is installed

The long curved thick spring on the left side is the hammer spring, it puts pressure on the return to zero hammer

Here is the depthing engagement between the oscillating pinion and the chronograph wheel.  The depth is controlled by the clutch and its eccentric, here depthing is slightly shallow as you want about 2/3 engagement

Increased engagement slightly, enough to have good positive contact but not enough to increase friction beyond tolerance

Finally the minute counter jumper spring must rest perfectly on 2 teeth of the minute counter when the hammer has been activated.  This prevents the minute counter hand from moving when the hammer is reset
Time to flip the watch over and work on the dial side components

The driving pinion is pressed on.  This is the friction point in the watch that allows the hands to move freely during setting but in normal operation is still moved by the mechanism

Here is some more of the motion work, the minute wheel and free cannon pinion have been installed

Here are the hour counter return to zero components and wheel

Here is the day corrector and its spring

Here are the 12 and 24 hour wheels installed

Finally, on this level, the calendar driving wheel
The penultimate page!  This is all jumpers and correctors
Date star wheel installed with the date corrector

Here are all of the jumpers and springs.  These index the day and month dials, along with the moonphase indicator
The final page of assembly, some final plates and the indicators
Here are the 3 indicator wheels installed along with the moonphase platform and combined maintaining plate

Dial is installed, hands are installed
Using a hand press to apply subdial hands
Completed movement, ready for casing
Cased and finished

Thursday, February 13, 2014

7751 Chronograph Base Movement

Today in class we did some practice for some of the tasks likely to come up on the CW21 test.  These include a staff replacement and a barrel bushing manufacture and install.  Once I had finished with those I started a reassembly of a 7751 which I was assigned yesterday.  It's the same as a 7750, but has a more complicated assembly on the dial side.  Below you will find step by step (more or less) assembly of the base movement.  The chronograph components will follow shortly.

These are the oils I will be using for this movement, from left to right (9415)(9010)(molycote dx grease)(D5)
Here is the oiling and assembly chart for the winding and setting mechanism

Grease is used on the sliding metal-on-on metal surfaces.  I wick the D5 heavy oil into the parts which rotate on a pivot point.  Here from left to right you have the: time setting gear, yoke spring, rocking bar, yoke, sliding and winding pinions and the setting lever

All of the setting components are held down by this combined setting lever jumper/plate which also holds the intermediate setting wheel.  Notice the white molycote on the jumper teeth to the lower right

Now that winding and setting are taken care of, time to flip over to the movement side and get the movement side components installed!
The going-train assembly instructions

Moving counter-clockwise from the large silver barrel at 12 o'clock you have: the great whee, third wheel, second wheel, escape wheel.  The thin silver metal bar in the middle is called the hack.  This stops the watch when you move the watch into time-setting position
After installing the barrel bridge plate which holds all of the train wheels down it's time to install the pallet fork.  Here it is with its bridge installed, you can see how the jewel pallets interact with the teeth of the silver escape wheel.

Now the rest of the winding components, here I have applied grease to the area where the crown wheel rides.  It's important to have this area generously lubricated due to the large amount of friction latent in the design.

Lubricating the underside of the plate that holds down the crown wheel

Crown wheel installed, I also wicked some oil down underneath the return to zero operating lever above the wheel.

Now all of the wheel pivots must be oiled.  Everywhere you see a red circle must be oiled (in this case with either D5 of 9010)  with the exception of the pallet jewel which does not receive oil.  The barrel arbor also needs oil.  This must be done on both sides of the movement
Here is the ratchet wheel installed, minus its screw.  This is the wheel that connects directly to barrel allowing winding but also making sure it does not unwind freely due to its interaction with the click.  The click in the thin metal wire you see engaging the ratchet wheel at 4 o'clock.

Time to oil the balance.  Here I have removed the in-setting and cap jewel from the block.  The shock spring and balance pivot are visible.

These parts are extremely small and very easy to lose if you are not careful.  The watchmaker must put a tiny drop of oil (in this case 9010) on the cap of the assembly then sandwich these parts back together.  Once installed in the watch it lowers friction on the balance pivots tremendously.

Here I am setting up the regulating pins for proper timekeeping, it's hard to see but the hairspring must be perfectly centered between the regulating pins before you close then to be just shy of touching the spring.  This guarantees the best time performance of the watch in differnt orientations.

Time to make sure the base movement is keeping good time before moving on with the chronograph assembly

The delta is good for this movement at 6.2, amplitude is okay at 262 between all positions and rate is slightly fast, but we save final regulation for the completed watch.