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Only fools will go… step 2
After making the plate and bridges in the first installment I am continuing by jewelling and trying out the going train.
The first problem found was the barrel touching the plate, which required further recessing. Here you can see the barrel (just the square end of the arbor can be seen at the very left), intermediate wheel, rue moyenne, and second wheel. My machining tolerances seem to be pretty good. The jewels are fitting like a dream and the longitudinal positioning is just fine. My local watchmaker and tutor tells me I’m not allowing enough end shake. So I add some. And that screw too close to the edge of the bridge is just part of the “learning experience”.
Time to thin down and part out the anchor bridge, which will fit in the round recess in the foreground above and holds the upper anchor jewel. The pins for positioning it have already been planted.
Jeweled and in place the anchor moves freely at the slightest breath of air, at this point still without banking pins. And that one screw needs to be countersunk a bit more. The bridge looks very good round like that, but I will have to file out 2 windows to allow seeing the pallets when checking the escapement.
I am intrigued to see if the motion works will look as good as the going works. To start with, I need to turn axles of the correct diameter for the center wheel and cannon. In the 2824 they are both turning on the seconds tube. By deporting the seconds from the minutes/hours hands I need to make axles for them. After polishing the axles were pressed onto the holes prepared by reaming to the correct diameter. I pressed the minute wheel axle out of a 2824 plate so that was easy.
Mounted things look pretty good. You have certainly noticed that I am using two cannon pinions. The first, with the cannon portion turned off, is mounted as usual on the center wheel. It drives from there the minute wheel as always. The minute hand will be mounted on a second cannon on the other side of the minute wheel, this to displace the minutes/hours from the center of the movement.
Time to cut out and finish the motion works cover.
Here the hour wheel is mounted too. That nose on the motion works cover will (hopefully) keep the setting wheel from falling out when I get that far.
Before trying out the escapement and balance I need to be able to put some tension on the going train. While I am at it I will finish the complete train from the crown to the ratchet wheel. For the three crown wheels I made hubs in the place of the screw with integrated washer used in the 2824. They are positioned by a stud in the center and held in place by two screws.
The ratchet is on the last crown wheel and not on the ratchet wheel itself, as this is implemented on a 2824 also. The ratchet wheel spring is the first flat piece in spring steel to be made. This is surprisingly simple using a miniature cut-off wheel on a grinder. Working slowly the work piece does not warm much at all so I have not tried to re-harden and anneal it again. It seems to have retained its spring properties.
Oops, I forgot to shorten the threaded part of that click screw which replaces the temporary stud in the pictures above. Now it is too late to do it easily on the lathe. What a pain! I hope I will learn to think of things like this in time some day.
Why no ratchet wheel in the picture? This is the first major error of conception that I have found up ‘til now. In a 2824 the ratchet wheel is turned from the automatic mechanism using small teeth, and from the crown through the large teeth of the crown wheel. The teeth of the crown wheel span 2 teeth of the ratchet wheel. My error was not to realize that I cannot use the calculated pitch circles of the wheels to determine the distance between centers in this case, as the addendum of the larger teeth is much larger than the dedendum of the smaller teeth. As this movement will have only manual wind, I figured that for the time being I could manhandle the ratchet wheel and file out every other tooth using a triangular file, which I did, only to find that the ratchet wheel has an odd number of teeth. That leaves me with a wheel that binds terribly once every revolution. So now I have an almost workable, really bad looking ratchet wheel. Embarrassing. In the end I will end up cutting at least one wheel, the ratchet wheel, for this movement.
Here is the first fit of the winding stem, pinion and sliding pinion in place. Amazing, but it fits first try. Below I am nearing completion of the clutch lever using a cutoff wheel on a hand grinder. This is my interpretation of the method explained by W.O. Smith in his book Twenty-First Century Watchmaking cited by SWE on this forum recently.
If it wasn’t for that disastrous mangled ratchet wheel I would be smiling now and winding smoothly, but as it is winding is difficult, uneven and almost stops completely once each revolution of the ratchet wheel. For the time being it will stay that way, however.
A lot of work and it doesn’t seem that I have gotten all that much further toward my goal. But as I am learning, watchmaking cannot be approximated. Watchmaking consists of a sum of details each of which must be right in order to have a satisfactory product.
Coming soon, the balance bridge with mounted balance and hairspring is finally installed. Will it tick?
Copyright © 2005 Donald W. Corson