English longcase problem

[Clockworks999]

I've got a strange problem with a late 18th century English longcase clock. The clock has sat unused for many years, and was missing the intermediate date wheel and bell. I've re-finished the pivots, replaced several bushes, and removed the rust from the steel/iron parts. A replacement intermediate date wheel and bell have been fitted.

The clock starts with a swing of 80mm (at the rating nut), and rapidly increases to 120mm. To me, this indicates that there's plenty of power, and the drop is OK.

Now for the strange part. At seemingly random intervals, the escape arbor stops turning for a couple of minutes, it just rocks back and forth as the pendulum swings, pushed by the pallets. After a couple of minutes, the clock starts running again!

I've removed the motionwork and cannon pinion, so that only the basic train is running. Everything points to a binding pivot, or bad depthing after previous repairs, but, why does the clock suddenly burst into life again without being touched? The clock never actually stops completely.
Over a 24 hour period, it stops running for about 25 minutes.

 

[LaBounty]

I would suspect deep ruts in the escape pinion which is causing the escape wheel to become trapped, or wedged against the plate, and the end shake to disappear. After a short interval, the jam may clear and, if the pendulum hasn't come to a halt, the clock will continue to run.

Let us know what you find!

 

[Clockworks999]

The escape pinion is, indeed, quite worn. No worse than many others that I've worked on, though. I'll try moving the wheel below to a better part of the pinion, and see what happens.

 

[shutterbug]

You could also mark the EW to see if it always stops in the same place. Then the trouble is for sure as David said or a tooth a bit taller than the others.
If it's more random, it's back to the drawing board

 

[Scottie-TX]

Intermittent power interruptions can be very difficult to diagnose because many times are so subtle that only a bump, the motion of the mechanism, etc., is sufficient to move the problem wheels into operation again. As SHUT writes, the best way to start is to mark the Escape Wheel and determine if the problem occurs once every revolution of the escape wheel or another wheel.

 

[Mike Phelan]

If it's an 8-day, it will probably have a seconds hand. The EW will rotate once a minute, and the third wheel either 7.5 or 8 minutes.
There are exceptions, but not often.

David's idea is favourite, and can be fixed by moving the wheel below slightly endwise.

 

[Clockworks999]

I stopped all the other clocks in the workshop, so that I could hear the longcase better. As soon as it stopped, I marked the escape wheel and the one below (third wheel?).

The clock (8 day) actually hesitates for a few seconds every 3 or 4 minutes. Sometimes it stalls for longer, maybe 2 minutes. The escape wheel is always in the same position, the third wheel stops in 2 positions.

With the movement back on the bench, turning the great wheel with my finger, the escape wheel sticks at those points. The tiniest nudge on either wheel, or more pressure on the great wheel, starts the train running again.

With the 2 arbors in my depthing tool, all seems OK - no tight spots.

I've stripped the movement down again and polished the escape arbor pinion to smooth out the transition between the original ruts, and the newer ruts created when the arbors were shifted maybe 50 years ago. I also broached out the rear escape arbor bush, as it was a little tight.

It's back on test - fingers crossed!

 

[shutterbug]

If you have a lathe, and if you have to open it again, try tipping the teeth ever so slightly just to insure they're the same height. Check to be sure the EW is running true as well.

 

[Clockworks999]

So far it seems to be running OK, but I'll leave it for 24 hours to be sure.

It needs to come apart again, as I only fitted the going train for testing, so I'll run the escape wheel in my lathe, topping it if necessary.

 

[Clockworks999]

I don't know why I didn't think of this before, but I connected my timing machine (Microset Watchtimer Pro) up to the clock this morning, and left it running for a couple of hours. The machine makes fault finding so much easier than staring at the clock for hours. It records a continuous bar graph of the beats, and the missing beats are easily seen, along with the time stamp

The clock is still playing up, pausing for for or 5 seconds in a very regular pattern, based on the 8-minute rotation period of the 3rd wheel and the one minute period of the escape wheel. It actually pauses at 8 or 3-5 intervals, so it appears that I have one bad leaf on the escape pinion, and 2 bad teeth on the third wheel - one tooth being slightly worse than the other.

This fault was obviously there before I got the clock, as the basic rate is set fast to try and compensate for the fault. The bob is adjusted to run 10 minutes a day fast.

I can also see a regular variation in beat, which is either an out-of-true escape wheel, or miss-spaced teeth. It's an early clock, with "marking out" rings scribed on all the wheels, so I guess that they are hand-cut, rather than mass produced. Some variation in rate is probably to be expected.

I'll top the escape wheel while it's out, and inspect the offending pinion leaf and 3rd wheel teeth.

 

[Mike Phelan]

I also broached out the rear escape arbor bush, as it was a little tight.

Surprising, unless someone has bushed it, as they're all usually fairly slack.

It actually pauses at 8 or 3-5 intervals, so it appears that I have one bad leaf on the escape pinion, and 2 bad teeth on the third wheel - one tooth being slightly worse than the other.

Seems like you've cracked it!

I can also see a regular variation in beat, which is either an out-of-true escape wheel, or miss-spaced teeth. It's an early clock, with "marking out" rings scribed on all the wheels, so I guess that they are hand-cut, rather than mass produced. Some variation in rate is probably to be expected.

Teeth would have been cut with a wheel engine, even in the earliest clocks like this; the wheels will be cast brass.
The teeth will have worn or bent over the centuries, but the beat difference is nothing to worry about.

If you're still stuck we're going to Cornwall for a week next year!!

 

[Clockworks999]

It was extremely worn, so I bushed it myself. I have a habit of bushing all clocks like they are French "drum" movements, i.e. precision instruments! Sometimes I have to open them up a bit more than I expected. This usually shows up when I run the train by hand. In this case, it didn't.

I've not had my timing machine for long - only a couple of months. I bought it because I'm learning how to repair my own watch collection, but it's also proving to be useful for clocks. It's certainly showing me how "irregular" clocks are compared to wrist watches.

What's the significance of the marking out circles scribed at the root of the teeth, if a wheel engine was used? Is it just a safety measure, to tell the machine operator when to stop feeding the cutter?


Whereabouts in Cornwall will you be going next year?

 

[Mike Phelan]

Ah - I see re the bushing. They are usually a bit slack, maybe through use, but generally not a problem, especially with the striking train.

Not completely sure about the circles except maybe it was to get the cutter deep enough to start with on the first tooth.

We'll be camping near Helston, probably late August. Feel free to pop in for a chat / meal / drink!

 

[Clockworks999]

I topped the escape wheel, and re-finished the offending teeth and pinion leaf. The beat error is now less than half what it was, and the pausing has stopped - been running for nearly 3 hours with no problems.

Whereabouts near Helston? I live in that area.

 

[Mike Phelan]

You're about to get a PM.

 

[Clockworks999]

Still working fine this morning. I'll reassemble the strike train and motionwork this afternoon.

 

[Jeremy Woodoff]

I was about to post a similar query when I came across this thread. In my case, I have an English long case with a 30-hour, endless-chain movement. It had worked without any problem for years, but then started losing inconsistently. I tried everything I could think of--cleaning and oiling, polishing pivots, burnishing strike levers--but nothing helped. Finally I discovered that the escape wheel was losing power and rocking back and forth, just as Clockworks found in his clock. I checked all pivot holes and wheel and pinion teeth--all fine. The three wheels of the time train would free-wheel smoothly, stopping at different positions each time. Finally, I looked at the plates with a loupe and saw that the pressure of the second wheel pivot had over many years thrown up a burr in its pivot hole. Couldn't feel it as it was in the oil sink and couldn't see it without the loupe. A few minutes cleaning it up took care of the problem.