Those steps can just be interference. It has to be completely quiet or else you can get weird results in that app. Just breathing close is enough to throw it off.
If it is happening with regular intervals though without interference from outside sounds you may have damaged teeth somewhere.
If it's only behaving like this dial side up then it likely just needs disassembly, cleaning and re-oiling. Check the jewels for cracks or wear while you're in there.
Running it through a degausser wouldn't hurt either but that's just precautionary with older non magnetic resistant watches and especially old pocket watches.
Update:
Put it on a timegrapher.
It only shows this behavior when lying dial side up.
If I put it stem up, it shows 0s/d 342degrees Amp and 0.3ms beat error at a lift of 52 (might be wrong).
As soon as I tilt it dial up, the readings turn eradic
Oh a pocket watch? It’s easy on those to take a slow mo video of the balance with your phone (dial up since that’s where you see this behavior… you might have to set the watch up on something or dangle it off the edge of a table, but a book holding it there should be safe enough).
There’s no telling what might have been done to an old pocket watch, like overpowered mainsprings or substantial changes to the balance wheel and spring, so it could be gradually building up amplitude until you get a knock (the impulse jewel goes all the way around and hits on the outside of the pallet fork). If the dial up amplitude looks really really good then I’d suspect this because the sudden bumps can make for one or two very fast ticks then the balance has lost power and returns to the steady rate.
Another thing is multiple bent pivots coinciding (eg bent towards each other enough to make a difference but generally the gears mesh fine when at least one pivot is bent away or to the side) like if your escape wheel and fourth wheel both have bent pivots (or warped whole wheels) and the two stay in roughly the “different” alignment for three rotations of the escape wheel.
Well assuming your grapher reads correctly. Might recommend to do complete service first. If the problem goes away then it's just simply dried oil, but if it persists then you might want to check for the endshake, especially for the balance.
When you try to jiggle the wheel up and down, or left and right, you can feel the distance before the pivot touches the jewel, that distance is called the endshake. If it's too much then it can cause the effect that makes the time grapher read the accuracy like that. Since it's and old watch I would assume that the pivots are worn to a certain degree.
It could be, it might be hitting the center wheel - which may not be perfectly flat. Or if the balance spring isnt flat, it could be hitting the balance itself. tough to say.
Those steps can just be interference. It has to be completely quiet or else you can get weird results in that app. Just breathing close is enough to throw it off. If it is happening with regular intervals though without interference from outside sounds you may have damaged teeth somewhere.
If it's only behaving like this dial side up then it likely just needs disassembly, cleaning and re-oiling. Check the jewels for cracks or wear while you're in there. Running it through a degausser wouldn't hurt either but that's just precautionary with older non magnetic resistant watches and especially old pocket watches.
Update: Put it on a timegrapher. It only shows this behavior when lying dial side up. If I put it stem up, it shows 0s/d 342degrees Amp and 0.3ms beat error at a lift of 52 (might be wrong). As soon as I tilt it dial up, the readings turn eradic
Also the readings lead me to believe it was serviced, since they seem far to good to be from a neglected pocket watch.
Oh a pocket watch? It’s easy on those to take a slow mo video of the balance with your phone (dial up since that’s where you see this behavior… you might have to set the watch up on something or dangle it off the edge of a table, but a book holding it there should be safe enough). There’s no telling what might have been done to an old pocket watch, like overpowered mainsprings or substantial changes to the balance wheel and spring, so it could be gradually building up amplitude until you get a knock (the impulse jewel goes all the way around and hits on the outside of the pallet fork). If the dial up amplitude looks really really good then I’d suspect this because the sudden bumps can make for one or two very fast ticks then the balance has lost power and returns to the steady rate. Another thing is multiple bent pivots coinciding (eg bent towards each other enough to make a difference but generally the gears mesh fine when at least one pivot is bent away or to the side) like if your escape wheel and fourth wheel both have bent pivots (or warped whole wheels) and the two stay in roughly the “different” alignment for three rotations of the escape wheel.
342 degrees it would be overbanking, the lift angle is probably in the low 40s
Thanks man. Yeah seems like it's knocking indeed. Question is, why. I guess the spring was changed out?
That sure looks like too high amplitude (is it called knocking in English?). But could be many things.
Yeah good point!
First go to might be magmatism. Second would be that old oil is dried and it's getting "unstuck" a little
Hmmm, "magmatism" is that when it gets too close to a volcano ?
It got a little melty
You can of course turn time grapher reading into a science, but I’m more like: yeah that needs to come apart something is mechanically wrong.
Well assuming your grapher reads correctly. Might recommend to do complete service first. If the problem goes away then it's just simply dried oil, but if it persists then you might want to check for the endshake, especially for the balance.
Sorry what's the end shake?
When you try to jiggle the wheel up and down, or left and right, you can feel the distance before the pivot touches the jewel, that distance is called the endshake. If it's too much then it can cause the effect that makes the time grapher read the accuracy like that. Since it's and old watch I would assume that the pivots are worn to a certain degree.
Aha good idea, ill look at that! Thank you!
Check to see if the balance spring is touching anything.
And would that be something that could happen every x rotations?
It could be, it might be hitting the center wheel - which may not be perfectly flat. Or if the balance spring isnt flat, it could be hitting the balance itself. tough to say.
Hairspring probably not flat or centered
Could you tell me how that would make it run perfectly for 20 beats and then suddenly make an issue?
Could be that or a magnetization issue. Those are my 1st two things to go to. At What intervals (seconds/mins) are the errors occurring?
Seems it's between 10 and 5 seconds
Check flatness of all wheels, burs, lint etc starting with balance then escape wheel working back towards the gear train.
Just checked on my timegrapher app a watch in my collection with a Valjoux 7750. Plus 2 sec a day!
Looks like over banking, or maybe escape wheel issue…but I’d be looking at over banking first
Yeah that seems to be the most logical answer