Clock running fast

[DrewV]

I have an old (1870's) Lenzkirch (sp?) horse-style wall clock (3-weight) that appears to be all original. However, ever since I got it, it's been running about 15 minutes fast per day. I haven't found a really good clock man locally that I have enough faith in to really look into the problem.

The only ideas I can come up with is to lengthen the pendulum (currently lowered ALL the way, however), add some weight to the pendulum, or change the suspension spring.

My question is: could this be solved by doing something simple as I mentioned, or does it look like it will be something more complicated like a mismatched gear train or something like that?

If anyone thinks that I could solve the problem by changing the suspension spring, please let me know what steps I would take to begin investigating how to do that. I.e., do I just measure the existing spring and decrease the thickness by 0.0005" or something like that?

Thanks.

[DrewV]

I have an old (1870's) Lenzkirch (sp?) horse-style wall clock (3-weight) that appears to be all original. However, ever since I got it, it's been running about 15 minutes fast per day. I haven't found a really good clock man locally that I have enough faith in to really look into the problem.

The only ideas I can come up with is to lengthen the pendulum (currently lowered ALL the way, however), add some weight to the pendulum, or change the suspension spring.

My question is: could this be solved by doing something simple as I mentioned, or does it look like it will be something more complicated like a mismatched gear train or something like that?

If anyone thinks that I could solve the problem by changing the suspension spring, please let me know what steps I would take to begin investigating how to do that. I.e., do I just measure the existing spring and decrease the thickness by 0.0005" or something like that?

Thanks.

[Dick Feldman]

Drew,
Your best approach will be to try to lengthen the pendulum. It also sounds like a new, longer suspension spring is the key. Much of the process will be trial and error unless you have a device for measuring the BPH. There is always the possibility that the pendulum will swing in an arc (relative to the back board on the clock case) or wobble with the longer suspension spring. If so, use one with thicker material in the flexing portion of the spring.
My experience with adding weight to a pendulum is that the effect will be minimal on time keeping.
If you observe the pendulum dragging on the bottom of the case before you achieve acceptable timekeeping, check for extra movement mounting screw holes. It sometimes happens that movements are transplanted into cases that cannot accommodate them.
Best of luck with your project and let us know how it comes out.
Dick

[mrb]

if pendulum is original there should be no need to tamper . problem is probably due to wear. worn pallet faces will not provide proper impulse and result in a shorter pendulum travel, thus clock gaining.

[DrewV]

According to my calculations, I have to change the center of mass of the pendulum almost 1/2". That means adding quite a bit of weight right at the adjusting screw, because I'm already nearly scraping the bottom of the case as it is.

I'll make sure I check the pallet wear when I disassemble the movement. But just how much wear am I looking for? After all, I'm sure it's going to have steel pallets, so how bad can they be?

I suppose someone could have ground down the faces to polish it up and I wouldn't be able to tell. Maybe I'll have to check the drop/lock and see if there's excessive play?

I'm still very new to all this, so I appreciate everyone bearing with me.

[mrb]

you must have lock, when the pallets are worn two things can cause problems. friction from the scored surfaces and the elimination of lock. if you don't have lock the escape wheel teeth just hit the impulse plane and skip by.this provides little impulse to the pendulum and results in a decreased motion. sometimes the wear can be polished out, other times it musrt be corected, boots new faces etc.