Wednesday and Thursday were pretty intense. It’s kind of like the couple of weeks or so spent working with hairsprings.
We had our lecture on Wednesday where we learned about how to true gear train wheels. We are going to get into truing balance wheels later this semester, so starting with gear train wheels is akin to training wheels on a bicycle (you can also true the wheels on a bicycle as well, and it is just as difficult when you are learning how to do that).
In essence, when you true a wheel (gear train, balance or even bicycle), you are taking a wheel that has a deviation in it that is causing a wobble/dip while it spinning and making small adjustments until you get it to spin true (or flat-no wobble). Similar to a bicycle wheel, gear train wheels have spokes and a rim. The distortion causing the wobble can come from the spoke, the rim, or the wheel itself can be flexed or compressed.
Sadly, and probably the most common way is from watchmaker error-either when removing or reinserting the wheels from the watch, dropping them, etc. Other than that, if there is a substantial shock to the watch, there can be distortions to the gear train wheels.
To rectify wheels that aren’t true is a relatively straightforward process. You find the distortion and correct it. Finding the bend, well, that is a different story. There are a couple of different tools that you can use to find the bend, and they all essentially do the same thing. The set-up that we are using in class is relatively simple. We are using some truing calipers, a small brush, a benchtop anvil, a piece of vinyl and some peg-wood.
Once you have the wheel in place, you spin it with a brush and watch it. You look for the wobble and try to figure out where the distortion is. I took a video of what the gear looks like when it is spinning . Unfortunately, it is at an angle so you can’t see the wobble.
Once you find the bend, you use the peg wood and benchtop anvil to reverse the bend.
The piece of vinyl comes into play because when you are trying to correct the bend, you need to over-correct it a bit, so the vinyl allows enough cushion to apply the right amount of pressure needed to correct the bend. It also will help prevent scratches from the anvil. If the bend is coming from the spoke or the rim, you can use this method. If the wheel is flexed (imagine holding a frisbee in your hands and twisting it in your hands so there is a high and low side), you will hold it between your thumb and index fingers with both hands and gently reverse the bend. If the wheel is compressed, there is a different set-up needed to correct it, but essentially you are going to pull it apart.
For the project in class, we were given 9 wheels to true. I have 5 of the 9 completed. The other 4 are going to take me a while to finish. I have corrected them, just not completely. What this means is the wobble that I am working for is ever so slight, and the area that is distorted is very hard (for me) to see. Hopefully I will be able to finish the last 4 by Monday.
I would say that out of everything we have learned so far, this would be the second in difficulty just after hairspring corrections. That being said, it is still exciting and fun to do, even if it hard. I just need to keep reminding myself that I am still learning and developing my eyesight and skills.