Shulou(Shulou.com)11/24 Report--

In the last issue, we introduced the winding, gear, escapement and pendulum wheel group of the mechanical watch, and in this issue we continue to introduce the movement of the mechanical watch.

Splint Let's start with the main splint, which forms the main body of the movement:

Note that the main splint has many different openings-we will use the parts that were built before they were installed in this section. The pink part of the picture is also a ruby (the same as the Matsai stone at the top of the escape fork and the core of the swinging wheel). They act as bearings so that the shafts of the parts can be rotated. Let's take a closer look at it:

There is a small cavity in the gem. In order to further reduce the energy loss of the rotating parts, the cavity is coated with a small amount of special lubricating oil. The lubricating oil will stick to the gem and the rotating shaft in the gem hole to further reduce friction, prolong the running time of the watch after a single winding, and reduce wear between precision mechanical parts. The first two parts we are going to install on the main splint are the escape wheel and the escape fork:

After installing these two parts, we cover the escapement fork with an escapement splint. The splint holds the other end of the shaft of the escape fork and is fixed on the main splint by two screws:

Notice that the swing of this escapement fork is limited by the shape of the two bulges in the center of the escapement splint:

This ensures that the escapement wheel can only push the escapement fork so far, and the further push will be stopped by these bulges. Then we can install the rest of the gears. The position of the four gears is carefully arranged, so that they will only take up a small part of the space.

Notice that the fourth gear goes through the center of the watch-you can see the shaft through which it passes on the other side of the main splint. At the end of the assembly process, we will install the second hand on this long axis. In order to ensure that all the gears are fixed, we cover them with a gear splint, which also provides a fixed point for the other end of the gear shaft. The gear set splint is also fixed to the main splint by screws so that everything is fixed.

Among the core parts, only the pendulum wheel group has not been installed yet. It is very special and requires a specially designed fixed mechanism. Let's first put all the parts on the pendulum set splint.

Notice that the hairspring as a balance spring is very fine, and its end is connected to the pendulum wheel. The name of hairspring comes from its fineness, which is why it is called hairspring in English. The yellow and cyan parts are used to adjust the vibration frequency of the hairspring. Let's see how they actually work:

The yellow part is tightly fixed to the hairspring, and by turning it, we can adjust the position of the pendulum wheel and the core above it in a state of free relaxation. This ensures that the wobble phase of the "drop" and "answer" of the pendulum wheel will go through the same time. The cyan part can slide freely on the hairspring, and it can prevent the free vibration of the hairspring tail, thus changing the effective length of the hairspring vibration. By adjusting the cyan part, we can adjust the period of the pendulum wheel to make the watch go a little faster or slower. We can also fine-tune the speed of the meter by adjusting the screw at the top-the head of the screw is not centered, so turning it will also slightly turn the small fork in the cyan part. The hairspring is made of special alloys, such as Nivalokes (Nivarox), whose stiffness coefficient remains constant at different temperatures, which improves the accuracy of mechanical watches. The last step in installing the pendulum wheel set is to install a shockproof mechanism, which contains a sleeve, two precious stones and a small spring for fixing.

When the watch is suddenly shaken, this structure protects the fragile tip of the pendulum shaft from being broken. Let's see how these parts work together to protect the axle when it shakes.

When the watch is shaken, the energy from the motion of the pendulum shaft is absorbed by the spring, much like the suspension system of a car. If the vibration is strong, the thicker and stronger parts of the pendulum shaft will transmit the load through the lid, thus protecting the fragile shaft tip. After this last step, we finally assembled the parts floating in the air into the watch movement completely. However, you may remember that I skipped the question of how to wind up the main winding. What will happen if we wind it up directly with the winding axis? To answer this question clearly, in the following picture I hit the lid of the development box so that you can see the clockwork inside:

As long as the clockwork axis is fixed, the main clockwork can drive the mechanical watch-you can see the second hand attached to the fourth gear turning on the other side. However, when we loosen the spindle, the main spring will be "broken"-by turning the axis back to release torque, so that the clockwork will quickly lose the stored energy and the mechanical watch will stop. In order to prevent the main spring from turning in the opposite direction spontaneously, we need to prevent the axis of the winding from turning counterclockwise, but at the same time allow it to rotate clockwise so that we can wind it up. This problem seems complicated, but it can be solved by a very simple device, which is the pawl. Let's see how it works.

In order to continue to improve our device, we first have to install a spring box splint as a solid substrate, which can secure the winding box and provide a fixed structure for other parts. Since this splint will cover part of the area, let's put a small lever together, and we'll talk about its role in the next issue.

Next, we use screws to fix a ratchet on the clockwork shaft. The ratchet has a square hole, which is consistent with the square at the top of the clockwork shaft.

This matching square allows the ratchet to rotate with the clockwork axis. Let me remove the screw for the time being so that everyone can see it more clearly:

Now install three important parts. The first part is a small pawl, which we first put on the open top of the splint on the winding box.

Within its limited angle, the pawl can rotate around its axis:

The second part is the pawl spring. This metal gadget is very springy, and when we press it, it produces a strong resilience.

Let's press the pawl spring a little bit and put it into the splint on the winding box.

When we turn the pawl and release it, the pawl spring will push it back in an instant.

The third part is the crown gear, which is also installed on the splint on the winding box. It is fixed by a left-handed screw, which, unlike most conventional gears, is tightened by rotating counterclockwise:

Notice how the teeth of the crown gear engage the ratchet. Although the crown gear seems to be missing one tooth for every other tooth, it and the ratchet can still mesh and work properly. The backlash of the crown gear can accommodate the small rod on the pawl to fall into it. If we turn the crown gear counterclockwise, he will engage the ratchet and wind it up. Notice how the teeth of the crown gear push the pawl away, and how quickly the pawl bounces back when it turns to the backlash.

When the pawl bounces back and hits the crown gear, it clicks, so it is also called "click" in English. Turning the crown gear counterclockwise will tighten the main winding, so what happens when you move clockwise? In the following simulation demonstration, notice how the teeth of the crown gear are stuck by the pawl, which prevents the crown gear from being reversed:

This simple device allows us to wind up by turning the crown gear. You can take a look at the illustration below. This pawl also prevents the main spring from reversing and releasing itself-which is why you can't drag the slider backwards unless you restart the entire demo control.

The second hand on the other side of the watch shows how to count seconds, but a complete watch should show both the minute and the clock. Let's see how the mechanical watch achieves this goal with a series of transmission gears.

The transmission gear is in our movement, and the second hand is installed on the fourth transmission gear, because it turns exactly once a minute. In order for the minute hand to rotate at the correct speed, we need a rotating shaft that is 60 times slower than the second hand gear speed. Fortunately, the designers of the mechanical watch movement have used an excellent way to "sleeve" the required speed from another gear. If you look closely from the front of the watch, you will see that the pinion on the third wheel shows a little bit from a small opening. We can put a wheel tube in the center of the watch (because it has a tube like a cannon cannon, so it is called cannon pinion). The wheel tube has a drive wheel, and we mesh it into the pinion mentioned earlier:

When the third wheel turns, it drives the driving wheel and the wheel tube. By attaching the minute hand to the wheel tube, we can record the minutes-the gears involved have precisely set the number of teeth to achieve the goal of 60 times slower than the second hand. We can see how the second hand and minute hand work from the picture below. The slider below simulates the flow rate of time, and you can slide it to control the speed of the presentation time.

The hour hand turns 12 times slower than the minute hand, but we only need to add two more gears to achieve it. Meshing the needle dividing wheel as an intermediary with the wheel tube, and then meshing the needle wheel with the pinion on the minute needle wheel:

The hour wheels are loosely mounted on the wheel tube, and they can rotate independently of each other. Put the hour hand on the hour hand wheel, and we have completed the device to drive the watch hand. I also added a dial marked for 12 hours, which allows us to accurately read the time indicated by the pointer.

The daily counting device of this table consists of four main parts-the locating rod spring, the indicating gear, the date splint and the attached gear, and the date ring printed with all possible 31 dates:

In order to explain how it works, I first hide the irrelevant parts. I will also remove the lid of the indicator gear and I can see a small torsion spring underneath. Let's see how these parts are driven by clockwise wheels.

When the needle wheel rotates, it will drive the gear of the date splint. The pinion on the other side drives the indicator gear and the torsion spring above it. The spring will be caught by the teeth on the date ring and bend, but at some point it will start to push the date plate. When the current ring rotates long enough, the locating rod spring will suddenly release the date ring and let it jump to the next position. You may wonder why we have to design such a complex device. Some readers may naively think that we just need to make the hour needle wheel turn around with the date, just as we used to let the minute needle wheel turn with the hour wheel. I'm sorry, but that will cause the "current date" displayed in the small window of the dial to rotate continuously, which makes it difficult to read which day it is. You can see this effect on the left side of the image below.

On the right, you can see the date indicated by the device we just built-it will only change around midnight. As you may be aware, the daily counting function of our movement is not so smart, it always counts 31 days a month, so we have to set the date back one day after the end of the last day of the small month. In addition, if the mechanical watch has not been running for a while, its time will go wrong. We need to find a way to correct the date and time for it. Fortunately, the gears that drive the minute hand, hour hand and date ring are all connected, so we only need to adjust one of the gears to adjust all the gears. I will briefly hide the clock wheel in the diagram to make it easier to illustrate:

Notice that when I turn the needle wheel, only the wheel tube turns. The wheel tube is tightly inserted in the driving gear, so it can usually be driven by the driving gear. However, because the other gears in the gear set can only rotate according to the rhythm of the winding box, the driving gear will be blocked by other gears while setting the time, but the wheel tube can overcome the friction with the driving gear and turn on its own. This allows us to set the time without affecting the gear set and prevent damage to precision parts. When the hour wheel is installed, we will see that the rotating minute wheel will also adjust the hour hand, and if we turn enough, we can adjust the date together:

Step by step, our mechanical watch becomes more and more perfect, but it still has some inconveniences. In order to adjust the time and wind up, we have to turn the gears inside the movement, which are usually safely placed in the watch case. In addition, in each month with less than 31 days, we can only adjust the date by adjusting the time, because this is the only way to adjust the date at present. Ideally, we should find a way to set the date independently of the set time. In order to solve these problems, we will install a rotating handle on the mechanical watch in the next issue.

This article comes from the official account of Wechat: Institute of Physics, Chinese Academy of Sciences (ID:cas-iop), author: Ciechanowski, translator: shepherd, revision: * 0

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