Pendulum woes

[lad111]

I have an old Junghams clock A13 works. The clock is running fast (about 20 min. every 12 hours). I have tried lowering the pendulum and have bottomed out on the case. Should I add weight to the pendulum or try and find a lighter one? Thanks for any input.

[willofiam]

I would check the lock and drop, if I remember correctly it can be adjusted on the back plate with the “back cock”, also length or strength of suspension spring could be wrong. If you think the pendulum is the correct one then adjustments can be made without adding weight or changing the pendulum. I believe a Junghans A13 beats at 8400 bph, the length of the pendulum should be 7.2 inches. Hope this helps and have a great day, William

[lad111]

Thank you for your response. I am not familiar with the “lock and drop” you mention. Would you please give me more info as to where this might be. As far as I know the spring is the same and possibly the pendulum as well. I have tried adding more weight to the pendulum with no results. Once again thank you for your response and any help will be appreciated.

[bernie weishapl]

Lock and drop are between the escape wheel and verge. Get Donald De Carle’s book on Practical Clock Repairing and I would also get Ward Goodrich’s The Modern Clock. These two are a must in my opinion and are two of the first books I studied. They are both excellent and explain about anything you will run across. The lock and drop are the escape wheel teeth entering and exiting the verge. Sometimes the depth can be adjusted from the back on the block that holds the pivot on the verge. Some have two screws holding this and can be adjusted up or down for depth. If the verge has adjustable pallets that(which I have seen adjusted and shouldn’t be unless you understand it well) have been adjust by some repairman before. I would not adjust pallets except as a last resort. If the escape teeth entering and exiting the verge is small you will have very little pendulum movement. It could also allow more than one tooth at a time to escape the verge causing the clock to seem to run fast. If they are to deep generally there is almost always one tooth slightly longer than the rest and can stop the clock from running. So I would study this pretty good because you will run across this quite often.

Another problem could be the suspension spring could have been changed at some time. If it is the wrong one that could cause your problem. The strength of the suspension spring will also determine the arc of the pendulum. A thicker (stronger) suspension spring changes the arc, or swing of the pendulum to be less; it usually makes the swing shorter therefore runs faster. Too thick (strong) and the clock will stop. Too thin (weak) and the clock will stop. A thinner (weaker) suspension spring changes the arc, it usually makes the pendulum arc increase. Remember, when the pendulum arc (swing) increases there is more time between ticks and the escape wheel turns more slowly which makes the clock run slower. All of these factors interact in a very complex way mathematically. Sometimes timekeeping is affected in ways that seem illogical. As soon as you start changing things you will need to be very careful because you can get yourself into more trouble. So a thinner suspension spring can slow the clock down.

So if the pendulum is original to the clock I would not think the pendulum is the problem. If it worked once it should work again.

[lad111]

Thank you for your response and suggestions. Not sure if I am comfortable trying to adjust the lock and drop but……guess I may have to dive in, think I’ll practice on another movement before I tackle this one. Once again thank you.

[bernie weishapl]

Like I said if you get one or both of those books it will go a long way in helping you understand escapements.

[stevefitzwater]

Can you share the history of this clock, is it something you just bought? or something someone brought to you?

Has it been cleaned and oil recently?

For it to be running fast and out of pendulum adjustment, says that something else is wrong, (i.e. wrong suspension spring, etc).

Give as much information as possible and pictures help identify all of the possible casues.

[willofiam]

@Bernie Weishapl wrote:

Like I said if you get one or both of those books it will go a long way in helping you understand escapements.

I second that Bernie….. Not that I really know anything, but, you can save alot of headache by getting a bit of a understanding of the theory involved in the escapement, William

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