Bulle Bulle suspension spring installation

[Jeremy Woodoff]

Can someone help with the correct order of operations for replacing the silk suspension spring in a Bulle clock? I have a replacement spring from Timesavers. It appears that if the spring is removed without supporting the pendulum, the fine hairspring will get stretched and distorted. This means that the pendulum would have to be completely stabilized in place while the spring is removed.

The lower chop of the suspension spring is held by a single bolt and nut; removal of that seems straight-forward. However, the upper chop is held by a threaded rod with nuts at both sides, and then on one side the rod continues with a series of nuts and insulating washers and a brass bar that acts as the electrical conductor to the hairspring. Is it necessary to disassemble this whole assembly in order to replace the suspension spring? To do that, is it necessary to disconnect the hairspring from the pendulum? There is also a second screw and nut towards one side of the upper chop, but this doesn't seem to go through the chop--at least the replacement doesn't have a hole in this location. I don't know what the purpose of this screw/nut combination is or whether it has to be removed or loosened to remove the suspension spring.

Here are pictures of the suspension spring from both sides and the top and also of the new spring.

Thank you!

Jeremy

 

[sophiebear0_0]

Jeremy

The procedure I use is:

1) disconnect the hairspring from the electrical contact arm. This is a single screw/washer arrangement. You can leave the hairspring attached to the pendulum.

2) Remove the single screw holding the lower part of the suspension attached to the pendulum.

3) You can then carefully swing the pendulum forward and free of the movement.

4) You will need to completely remove the upper screw bolt to free the suspension from its upper mounting bracket.

5) Firstly loosen the small black stabilising screw. This allows the upper chops of the suspension to be fixed in place to compensate for any misalignment in levelling.

6) Loosen the nuts on the upper threaded bar to allow it to be removed. From memory, I think the upper suspension bracket is threaded, so you have to unscrew the bolt, rather than just pull it through.

7) Fitting the new suspension is the reverse of above. Do check that the centre hole on the new suspension is sufficiently large to accommodate the bolts. Also check that the new suspension isn't too thick to fit in the openings. It may require some light filing to reduce teh thickness.

Hope that helps.

Regards,

Peter

 

[Jeremy Woodoff]

Thanks so much, Peter, for these clear instructions. I'll have to steel myself for this; I do not get along with hairsprings of any type.

 

[sophiebear0_0]

Jeremy

You're very welcome.

One KEY point that I should have mentioned.

I would certainly recommend unlatching the iso-spring from the pendulum bobbin before attempting to change the suspension. The iso-spring is pretty delicate and it is easy to stretch/deform it. You will need to do this with a good quality pair of tweezers.

The downside or removing it is that the iso-spring can be a real devil to re-install. Different people will have preferred methods. Its not an easy process to describe. My best advice is a good pair of tweezers, good light and plenty of patience. I usually try to hook the spring on just one of the small holes initially. I then move the pendulum to the extreme position and fix it with a clothes peg. You can then very carefully manipulate the spring with the tweezers so that it passes through both small openings.

Good luck !

Peter

 

[Jeremy Woodoff]

Peter, is the iso spring the half-inch long coiled spring attached to the pendulum about half-way down? If the pendulum were wedged into position before starting the work, could this spring be left in place? It seems as though the suspension can be replaced without disturbing the position of the pendulum too much.

 

[sophiebear0_0]

Jeremy

Yes the iso-spring is held between 2 bobbins. The upper part is attached to a fixed bobbin on the movement, the lower part of the spring is attached to a bobbin on the pendulum. This bobbin is free to slide up and down to control the tension in the iso-spring. The purpose of the iso-spring is to compensate for the reduction in pendulum swing as the battery runs down. The greater the iso-spring tension, the faster the clock will run.

There is lots of excellent information about the Bulle clock on this forum. I would also highly recommend the website www.horologix.com.

Can you replace the suspension without detaching the iso-spring ? Yes in theory. I would say that you will have to be very careful that you don't allow the iso-spring to become stretched. If you plan to take this approach, I would be extra vigilant in making that the new suspension will fit easily into the upper support and the pendulum bracket. You certainly don't want to be having to struggle with the suspension fitting if the iso-spring is still attached.

You mentioned your phobia of hairsprings. Join the club ! The good news here is that the hairspring is there solely for electrical contact. Obviously it is best not to damage the hairspring, but they are generally quite robust and if you deform it slightly it won't make any difference to the running of the clock.

Good luck and let us know how it goes.

Regards,

Peter

 

[Jeremy Woodoff]

I successfully replaced the suspension spring! The holes in the new spring were too small and had to be opened up with a broach, and just enough filing done to remove the resulting burrs. I had no trouble keeping the pendulum stabilized so as not to damage the iso spring, which I left in place. After a little adjusting of the pin position in the yoke, which changed because of the new spring, the clock seems to be running just fine.

I had looked at that great Bulle forum a while ago. When I got this clock a couple of years ago I had trouble getting it to run, but a discussion on this MB helped me get it going. I'm fortunate the clock didn't have much wrong with it, as I wouldn't want to try to disassemble the movement entirely.

Thanks again, Peter!

 

[sophiebear0_0]

Jeremy

Well done, that's excellent news. You did very well to avoid damaging the iso-spring.

Good to hear that your clock is running well. One thing I did notice from your photographs is that the silver contact pin looks rather dirty. With time the contact pin and silver contact on the fork do accumulate a non-conductive layer. Eventually this may stop the clock running. The contacts are designed to be self-wiping, but this only cleans a local area. So if you move the clock, the clean surface may no longer be exposed.

The pin/contacts can be cleaned using light burnishing and a spray electrical contact cleaner. Always make sure you have good localised ventilation when applying the spray contact cleaner because it is highly flammable. And of course the contact itself is a source of sparking. Just don't leave the clock unattended immediately after applying any spray cleaner. I speak from experience !!!

Best regards,

Peter

 

[Jeremy Woodoff]

Jeremy

Well done, that's excellent news. You did very well to avoid damaging the iso-spring.

Good to hear that your clock is running well. One thing I did notice from your photographs is that the silver contact pin looks rather dirty. With time the contact pin and silver contact on the fork do accumulate a non-conductive layer. Eventually this may stop the clock running. The contacts are designed to be self-wiping, but this only cleans a local area. So if you move the clock, the clean surface may no longer be exposed.

The pin/contacts can be cleaned using light burnishing and a spray electrical contact cleaner. Always make sure you have good localised ventilation when applying the spray contact cleaner because it is highly flammable. And of course the contact itself is a source of sparking. Just don't leave the clock unattended immediately after applying any spray cleaner. I speak from experience !!!

Best regards,

Peter

The pin looks very dirty in the picture, much less so in person. But cleaning it is probably a good idea.