We had now covered the majority of our exam preparation, with the exam not until October and the first year almost coming to a close, we got the chance to do a bit more work on our school watches. The second year of the course is much more demanding especially to begin with as we cover things like hairsprings so I wanted to get the most time consuming parts of my watch done.
As you will have seen in my previous posts, I planned to build a watch with a regulateur complication but so far the idea was only in my head and on a few scraps of paper. I needed to build a functioning prototype, not just to check it worked ok but also to find the best way of producing all the components. I was confident that my idea would function and seeing it come to life would be a fantastic feeling.
My first task was to create the gears that would turn the mainsprings energy into a hand on the watch the does one complete rotation every 12 hours. The 6498 has a 6 o’clock sub dial displaying the running seconds so I wanted my sub dial displaying hours to be at 12 o’clock to keep things symmetrical. My finished watch would then display hours in the 12 o’clock sundial, minutes around the outer edge of the dial as normal and the seconds in a 6 o’clock sub dial.
In a watch the hour wheel turns once every 12 hours so my task was transmit this speed of rotation from the centre of the watch to the a position at 12 o’clock mirroring the 6 o’clock sub dial. The easiest solution I came up with was to create a gear train consisting entirely of hour wheels albeit modified ones. This way I would retain the turning ratio of the standard hour wheel as all the wheels have the same number of teeth.
To make it work I needed to modify 3 additional hour wheels create the gear train that would turn the hour hand. For the first wheel I turned off the tube and broached out the hole, it was then friction fitted over the standard hour wheel. The idea being to lift the hour wheel above the top of the main plate and allow it to drive the other 2 wheels on top.
The other to wheels needed to be modified to carry pivots in order for them to sit in the main plate and carry the hour hand. I began by again turning off both tubes and broaching out each hole to allow them to carry an arbor with pivots. My next task was to turn to arbors with pivots out of a piece of blued steel. The first arbor would be for the intermediate drive wheel to allow it to sit in the main plate, the size of the pivots for the prototype didn’t really matter so I went for 0.5mm. I have decided to turn a post similar to a minute wheel post for my finished watch to give more stability and negate the need for a pivot hole in my dial.
The second wheel I modified would carry the hour hand so the top pivot diameter and length needed to match that of the fourth wheel, which carries the second-hand, so I could utilise a standard ETA hand. The bottom pivot was once again made to 0.5mm as this was just a prototype. The arbor on both wheels was made slightly thicker than the hour wheel and friction fitted into the centre of the wheel using a Horia jeweling tool.
The next job was to drill the holes in the main plate to accommodate the wheels, I used a deputing tool to measure the distance from the centre jewel to the fourth wheel jewel, this allowed me to precisely position the 12 o’clock sub dial so it was a mirror image of the 6 o’clock one. This hole was then drilled and the wheel carrying the hour hand fitted in position, I could then position the hole for the intermediate wheel so that the teeth meshed correctly with the other two wheels. This was then drilled and all the wheels put in position.
I didn’t quite get the teeth of the intermediate hour wheel and the standard hour wheel to mesh deep enough but it will allow the prototype to function and can be rectified when I produce my actual watch. With all the wheels in position and turning each other as planned, I decided to assemble a complete 6498 and check everything was working correctly with the watch running.
Thankfully everything ran smoothly and the time could be adjusted accurately in the handset position, to say I was pleased would be an understatement. Its an amazing feeling to see an idea become a reality and before I started the course, I could never have imagined that I would be able to produce something like this. It just shows that anything is possible if you put your mind to it and put the hard work in. All I have to do now is recreate everything with a few minor improvements and with better precision and I will have a finished watch with a complication.
Instead of just producing a bridge, I’m going to produce a dial and bridge combined from a single piece of brass and this will be my next task to complete before we finish for the summer break. After the brilliant result of this prototype, I’m very much looking forward to the challenge.
A few videos that show the prototype in action…