Intermittent strike

[skinnb1]

I am having problems getting this clock to strike consistently. When the strike mainspring starts to run down after 3 days or so it misses the odd strike (usually the half-hour) so that when the minute hand is at 12 o'clock it strikes the missing half-hour and subsequent strikes are out. Sometime it misses another strike so that it is more in sync, but an hour slow.

What seems to happen is that it goes into warning but the pin in the picture below catches on the lever which should release it - sorry don't know the correct names. When the hour should strike this is released and the half-hour is struck and the perhaps twice in 24 hours the problem is repeated. I am assuming that the count wheel is not perfectly round.

I have been bending the lever up slightly but if I bend it too much it then doesn't stop striking. It seems really hard to get the amount of bending right. Should I have been doing something else? I suppose I could replace the mainspring so that there is more power and it would presumably work OK for longer.

Thanks for having a look.

 

[shutterbug]

I don't think you should bend anything on that one. I also don't think it has anything to do with the mainspring. It could be that the count wheel is slightly out of position. At 2:00, The count hook should hit right on top of that little raised part on the first strike, and fall right behind it on the second. If the first strike is not exactly on top of that raised part, loosen the screw that holds the count wheel and turn it slightly so it is.

 

[shimmystep]

I think shuts is on to the problem. if you look at the arrows in the pic below, you can see that the stop pin (Blue arrow) is stuck on the indent edge as opposed to on its face. So the count wheel knife edge is not dropping into the countwheel spaces properly (red arrow)

 

[skinnb1]

Thanks for the suggestions. I understand the principle, but I think what you see in the picture is the 12:30 strike stalling. The hook has been raised and has risen out of the count wheel slot. The gear wheel with the pin has started to move but is then caught by the lower edge of its lever. I have been going cross-eyed watching the count wheel rotate and the hook seems to drop into its slot correctly at the end of the hour strike then rise slightly with a small rotation of the wheel for the half-hour strike.

Wouldn't the problem be happening more frequently and even when the mainspring was fully wound if the count wheel was slightly off?

 

[R. Croswell]

Thanks for the suggestions. I understand the principle, but I think what you see in the picture is the 12:30 strike stalling. The hook has been raised and has risen out of the count wheel slot. The gear wheel with the pin has started to move but is then caught by the lower edge of its lever. I have been going cross-eyed watching the count wheel rotate and the hook seems to drop into its slot correctly at the end of the hour strike then rise slightly with a small rotation of the wheel for the half-hour strike.

Wouldn't the problem be happening more frequently and even when the mainspring was fully wound if the count wheel was slightly off?

Frequently failure of the strike train to start reliably as the spring runs down, if all else is correct, turns out to be that the strike hammer begins to lift and is left partly raised after the warning run. The hammer must be completely at rest after the warning run so the train can get speed before starting the lift.

RC

 

[shutterbug]

Also, the count hook should be fully into the groove, not raising until the next warning run.

 

[shimmystep]

Also, the count hook should be fully into the groove, not raising until the next warning run.

agree shuts. In my pic with the arrows, if the stop pin was on top of the indent as opposed to being stuck under it, the count hook would be in the groove as you say it should be.

 

[skinnb1]

Thanks for the various suggestions. I fear I may have confused the issue with my previous picture which showed the failure of a half-hour strike. Below is a picture showing a strike having taken place. You can't see the star wheel but the lever appears to be OK. I think this looks OK, but I'm happy to be corrected. I'm now in test mode waiting for the mainsprings to run down naturally.

 

[Tinker Dwight]

The stop detent already looks to far bent up.
I think we need a video. Don't bend any more.
I'm thinking there is a problem with the lift of the
cam.
It could also be a timing issue. The maintenance
cam could be dropping the count lever too close
to the warning pin hitting the stop lever.
And the count tooth for the stop at 12:30 looks
too narrow.
We need a video to make much sense of it.
Tinker Dwight

 

[shutterbug]

You'll have to post the video to Youtube and link it here

 

[skinnb1]

Thanks for all the advice. This seems to have resolved itself. I have adjusted the position of the strike lever relative to the star wheel but I noticed that the pin on the wheel controlling the striking was "kissing" the lever (detent?) when the gear wheel rotated during striking but only between about 9:30 and 12:30. My conclusion was that the count wheel wasn't perfectly circular or at least wasn't rotating perfectly. The bushing looks OK to me but perhaps I wasn't being critical enough. In any case I bent the lever which releases the strike and allows the strike train it to go into warning. I bent it very slightly although it was difficult to estimate how much it was being bent by. It has now been running for a week without missing a strike so I believe the problem is solved.

Thanks for the help.

Just for information the movement is a Badische Uhrenfabrik with the B and crescent trademark. It has unusual detachable barrels with the barrel and the rear pivot hole each with a cutout to allow the hook on the winding arbor to clear when the winding arbor is withdrawn although it's not clear to me how you disengage the hook from the mainspring to allow the winding arbor to be withdrawn or how you would engage it when inserting the arbor into the barrel when in the clock.