Re: Newbie needs help
Hi all
I am in the process of trying to "sort" my ma-in-law's old Bulle clock.
With lots of help from Peter Smith's Horologix website and some new bits (fork, suspension) I have it running for the first time in 25 years, so feeling fairly chuffed.
Problem is it won't run to time. Loses about 15 mins a day! I've read the whole of this thread, and most of Peter's case histories, without finding the cure. I am worried that there is evidence of previously "unsympathetic" attempts to fix it. Evidence for this is the fork arbor which is not typical of any photo I've seen and seems to have the pawl pivot "mashed" onto it. We had to make a special bush to refit the fork. How do I tell if the gears are correct for this model?
Runs like a dream on 1.5v as you will see from the photo of the pendulum swing. Checked the pawl, definitely one tooth every swing (for the five minutes I watched before I went "boss-eyed"). I know the silver contact spring is missing at present but I don't see that as the issue.
All advice welcome. Serial No is 54166
Cheers. Ian
ps incidentally, I'm afraid the Horologix website is no longer a source for parts. Peter has posted a note to the effect that time/life has caught up with him and he's had to stop. he gives a new link for someone who has taken over the parts supply
Ian, welcome to the NAWCC Message Board! Thanks for your inquiring and for posting the photos of your MIL's Bulle, and congratulations on getting it to run. That's usually the biggest hurdle, after that we can usually find how to bring the clock to time.
Based on the movement serial number, the clock was made in the April-June quarter of 1924, just a little later than Steve Wolf's clock I just posted about. This is the third clock of this exact case design I have documented so far, so it's not really very common. The other two were made in 1927 and 1929.
You asked about whether the gear count is correct for this movement. Since it is within 15 minutes per day, there is no question it has the correct gearing. A change to the gearing of either the larger standard model or any of the smaller Clockette models would have you off by an hour or more per day.
First things first, I recommend you do the check that Tinker has proposed to be sure you aren't missing any teeth. There won't be any assurance with even a half-hour check and "going blind" while watching the action. Also it will give you a base line from which to do the adjustments I have outlined below.
I've looked closely at the photos you posted to see what I might observe about why it is running slow. Before going into the detail, I expect you have already found that using the rating nut will not speed up the clock enough to compensate for it being 15 min. per 24 hr slow. For this clock, one full turn of the rating nut will only change the rate by 2 minutes in 24 hours, not nearly enough to bring the clock to time from where you are by using that method.
Now let's look at other possibilities:
1) You have observed that the drive pawl is picking up one tooth at a time on the escape contrate wheel, so that can be eliminated.
2) It appears the pendulum assembly is about as short as it can be made and the pendulum coil is centered on the magnet, so there isn't much if any room to shorten that. Shortening the pendulum "will" speed up the clock but this is normally not a factor.
3) The suspension unit supporting the pendulum has the correct gap between the upper and lower brass chops and you mentioned it was new so no problem there.
4) I see there is yet plenty of adjustment room to add tension to the isochronous spring, possibly up to 5 or 6 mm. That's the spring connected between the back of the movement and the front pendulum rod.
Adding tension to this spring will speed up the clock. That is achieved by lowering the isochronous spring clamp on the front pendulum rod, which will speed up the clock about 5 min. per 24 hr. per millimeter of additional spring length.
Point 4 is the key to getting your clock to run to time, since it appears to be running steadily and not missing any teeth on the contrate wheel.
You need to lower the isochronous spring clamp to speed up the clock. This stretches the spring and thus increases tension. If you need to slow down, the reverse is true. This really a trial and error affair but my experience shows the approximate rate change you get with each mm of adjustment as noted above. You will need to make small adjustments each time and carefully record the actual time gain or loss per 24 hours after each change. These adjustments must be made with the pendulum rating nut in its present position.
Please note that before you try to use the rating nut on the bottom of the pendulum coil, you need to get within about 2 or 3 minutes per day of correct time by adjusting the isochronous spring. When you are within that range, either slightly slow or slightly fast, first let the clock run for a few days to "settle in" so you can be sure no further adjustment is needed to the isochronous spring. Then you can use the rating nut to make fine adjustments.
Keep us posted on your progress.