Correcting beat error

[Bonzer]

For about the first time ever, I've managed to do some successful hairspring manipulation and corrected a badly bent hairspring on a Longines 12.68n movement.

It all runs a lot better apart from the 7ms beat error. I did mark the original position of the collet but not accurately enough. The problem is, due to the way the watch is built, I cannot see the pallet fork when it's at rest so therefore cannot determine even in which direction the spring needs to move in relation to the balance wheel. 

How can the direction and amount be ascertained with minimal visual clues?

Secondly, is there a way of adjusting the collet without disassembling the balance each time? 

[watchweasol]

Hi is there any mileage in stripping the watch and re fitting the fork/pallet and the balance alone to determine the relationship ?.  Moving the collet whilst mounted in the watch is a dangerous thing to try it is best done off the watch and balance removed from the cock, for safety

[JohnR725]

it would be nice if you give us pictures. Like the hairspring in the watch the timing machine numbers the graphical display of the timing machine. Telling us the beat is fine but what was the amplitude?

21 hours ago, Bonzer said:

Secondly, is there a way of adjusting the collet without disassembling the balance each time

what do you mean by disassembling the balance?

all you have to do is rotate the collet. They make special tools for this basically a screwdriver with a really long taper because of you use the normal screwdriver and wage it in you spread the collet which is very bad./They make tools there are just a very very long taper that you can use the rotate the collet so literally that will drop in with no friction and then you just gently turn it anything that wages into the crack of the collet is very bad. But there's no need to disassemble which is why I am confused with what you're saying?

[Bonzer]

9 hours ago, watchweasol said:

Hi is there any mileage in stripping the watch and re fitting the fork/pallet and the balance alone to determine the relationship ?.  Moving the collet whilst mounted in the watch is a dangerous thing to try it is best done off the watch and balance removed from the cock, for safety

It would be a bit of a pain as I've already oiled everything so I'd imagine the stripped parts would need cleaning and re-oiling?

48 minutes ago, JohnR725 said:

 Telling us the beat is fine but what was the amplitude?

The amplitude was between 270 and 300, depending on position. I'll try and get some photos

48 minutes ago, JohnR725 said:

what do you mean by disassembling the balance?

Well, as watchweasol says, it's too risky trying to adjust it in place and in addition, it seems like it will be much safer to remove the balance wheel and spring completely from the balance cock before adjusting the collet. Is this correct?

 

[JohnR725]

18 minutes ago, Bonzer said:

Well, as watchweasol says, it's too risky trying to adjust it in place and in addition, it seems like it will be much safer to remove the balance wheel and spring completely from the balance cock before adjusting the collet. Is this correct?

part of the reason I ask the question was I've seen some people when adjusting beat claim that you have to entirely remove the hairspring and put it back on again. But definitely removing it from the watch from the bridge is a good thing. Another thing I've seen people do is hang the bridge on a balance tack and let it hang which in my case usually will distort the hairspring and try to do it that way but you can't really see what you're doing. The best way is the balance comes out you rotate the collet put it back in.

then there is an alternative way to supposedly tell if you're in beat I'm attaching an image.

[Bonzer]

That's an excellent suggestion John, I can see the pallet stones and escape teeth in this movement. I guess the trick is not to put so much power into the train that the escape wheel overpowers the balance wheel, knocking it off it's natural resting position

[JohnR725]

sso my understanding from reading the text would be let all the power off  gently wind it until you just  barely see the escape wheel have power on it  but not enough that runs the watch  then the only thing that bothers me about this is it does assume that the banking pins or where there supposed to be and adept stones or where there supposed to be. Because of you look at the drawing anywhere push one of the stones in it would change where it is.  So basically it assumes the escapement is set up correctly  and on vintage watches that becomes problematic..

But still it would give you an idea.. The other thing is if you site from the roller jewel to the balance wheel  and put a Mark on the top of the wheel that corresponds to the roller jewel you can then make sure that is in alignment.. Sometimes watches will conveniently have a screw  in the right place in the balance rim  corresponding where the  roller jewel is..

[Nucejoe]

However little you move the hairspring or collet,  you bring some impercision to the dynamic poise and create beat error too.

Persuambly you watch has a fixed stud holder, so there are two ways I try to correct for beat error without disturbing the dynamic poise.

1- Unpin the hairspring off of the stud, run the hairspring passed the stud whilst you are reading beat error on TG. Repin when you zero the beat error, having a long micro-pin for easy removal or repinning makes life easy here. but this is a one way street.

2- You can move the position of impulse pin by altering shape of the bend at the end of terminal curve or the portion of terminal curve passed beyond the regu arm, this is good for cases of small beat error. 

 You specially want to consider these two approaches for chrono grade oscilators. 

Regs

Joe

[Bonzer]

Thank you both for your help.

Interesting thought about the adjustment of the hairspring in the stud. When I first refitted the spring, there was a good 10mm of spring that was sticking out the other side of the stud and I got a beat error of 0.5ms! I 'corrected' this and got a higher beat error. 

Fortunately, I left the complete ling micro-pin uncut so I can still move the spring if needed.

[JohnR725]

1 minute ago, Bonzer said:

When I first refitted the spring, there was a good 10mm of spring that was sticking out the other side of the stud and I got a beat error of 0.5ms! I 'corrected' this and got a higher beat error. 

I just need a clarification here? So you had surplus spring sticking out and you fixed that by putting it where it's supposed to be? In other words supposed to be at the end somebody just screwed up and pinned it in the wrong place?

As you've discovered you can rotate the collet the change the beat. You can also unpin the hairspring and moving that and also changes the beats. The only problem is the length of the hairspring is used for timekeeping purposes. So if you did not repeat in the hairspring back where you found it conceivably going to have timekeeping issues and of course beat issues conceivably. A lot of times in vintage watches things weren't exactly an exact science and extra hairspring stuck out. It gave them room to adjust things and they just left it that way.

[Bonzer]

6 minutes ago, JohnR725 said:

I just need a clarification here? So you had surplus spring sticking out and you fixed that by putting it where it's supposed to be? In other words supposed to be at the end somebody just screwed up and pinned it in the wrong place?

Basically, yes. The hairspring was a a bit bent and sticking out the stud before I did anything. It was running at low amplitude and at circa -100s/d.

Its running at much better amplitude now and around +15 s/d but out of beat.... possibly because I thought I was doing the right thing in reducing the 'spare' length of spring.