Today I had my lecture on how to use the various timing machines we have in class. Timing machines can tell a lot of information about how the watch is running in a relatively short-time and concise fashion. When timing a watch, the part that is mainly being checked is the balance complete (balance wheel, pallet fork, escape wheel)-though based on the readings, you can ascertain some things about how the watch is running and where potential problems might be coming from.
This is a Witschi machine. Witschi makes some of the most popular timing machines. The black piece in the foreground is a microphone stand. You place the watch movement on it and the vibrations/noise from the watch movement get transmitted to the machine and compared against a quartz crystal/microchip set-up that measures three different things:
- Rate-How much time the watch is gaining or losing (displayed as seconds per day)
- Beat Error-If there is an asymmetrical oscillation of the balance wheel (remember, the balance wheel swings back and forth so a beat error can be simplified as the difference between the “tick tock” (swinging clockwise) and “tock tick” (once it reaches its apex on its clockwise swing it swings back))
- Amplitude-Angle from idle position to maximum displacement
At the bottom of the screen are the different parameters that can be set-the two that have a direct bearing on the calculations are beats per hour and lift angle. Beats (vibration) per hour is dependent on the watch movement (one beat or vibration is when the balance wheel swings in one direction. The swing back is a second beat/vibration. The two combined is considered an oscillation.). There are 4 common “BPH” that most watches will fall into:
- 18000 BPH (2.5 hz)
- 21600 BPH (3 hz)
- 28800 BPH (4 hz)
- 36000 BPH (5 hz)
In case you are wondering how to convert BPH to hz, you use the following formula:
The higher the BPH in a watch, the more accurate it should be, also it determines how many times the second hand jumps per second (anywhere from 5-10 times a second) The more times it jumps, the smoother the appearance of the “sweep” the seconds hand will have.
Lift Angle is a bit more tricky to explain, but basically, lift angle is the angle the balance passes through while interacting with the pallet fork.
Lift Angle and Amplitude are intertwined. Each movement/caliber has a certain lift angle, typically a watch is around 52°, but can be between 58-55°. If you have the wrong lift angle programmed in the machine, you will get the wrong amplitude.
Once you get the movement on the machine, you will have a graphical representation of what is going on.
With this watch, it is running +127 seconds a day, has a beat error of 9.3 milliseconds and an amplitude of 162°. In the middle of the screen, you can see two lines running relatively upwards and parallel to each other. All of this is “bad.” In any watch, you want as little rate variation and beat error, and the amplitude should be at least 250° minimum. Even without the rate amount, the trendlines running upwards means that the movement is running fast. Here are some other trends and what they mean (and the correct action to take with them)
Before you start playing around anything, it is important to make sure that you have the watch ready for timing. It needs to be clean and properly oiled. Besides that, you want to make sure that your escapement is in static beat. Static Beat is when the pallet fork is is equidistant between the banking pins with the roller jewel being in line with the center pin of the pallet fork, the arbors of the pallet fork and escape wheel.In order to do that, you need to make sure the watch is powered down. You then need to look at the pallet fork, and if it isn’t in static beat you will gently rotate the wheel clockwise/anti-clockwise and watch which direction it moves the pallet fork. Once you have noted that, you need to remove the balance bridge and separate the wheel from it to have access to the collet. Whatever direction the wheel needed to move in to center the fork, you need to rotate the collet in the opposite direction. After rotating the collet, you then put everything back together and check the position of the pallet fork. Repeat this procedure until you have the watch in static beat.
Once the watch is in static beat, you can start working on the timing. The quickest way to adjust the timing is to adjust the regulating arm on the balance.
If you look at the balance bridge of this watch, you will see a scale along with a + and – sign. The arm that is resting between the + and – is the regulating arm. If you move it towards the +, it will speed the watch up, and conversely moving it towards the – will slow it down. Assuming no problems with any other parts of the watch, you should be able to get the watch timed using this method.
I spent most of today learning how to use the timing machine and seeing what the impact of static beat can have on timing. It is definitely interesting to see how the precision of everything I have been doing the past couple months has been building towards this. Disassembling, cleaning, truing springs and gears, staffing and poising balances and oiling all have to be right and perfect to make sure that you are getting the right rates for timing (which is what horology is about-precision timekeeping). I still have a couple weeks left in the semester, so I am excited to see what is left.