Sticking chrono second hand

[freddy333]

What would cause the chrono second hand on a Valjoux 72 to cause the entire movement to stop running when it reaches the 12 position (the hand is definitely NOT coming into contact with anything on the dial side)?

The mainspring is fully wound & the movement has been running perfectly (including the chronograph) for over a week with only the 3 subdial hands installed on the dial. Today, after fitting the remaining minute, hour and chrono seconds hand, all was well until I started the chronograph. It ran fine until the chrono second hand reached 12 and then the hand stopped, twitched for a bit, and then just sat there. Within a second or two of the chrono second hand stopping, the balance came to a stop also. If I either press the upper pusher (to stop the chrono function) or tap the chrono second hand with a toothpick, the balance starts up again and the watch runs.

I just removed the chrono second hand and then restarted the chrono, but it stopped again just after the chrono minute counter (subdial at 3) clicked to the first marker. However, after I stopped and restarted the chrono, the watch and chrono have been running now for about 15 minutes. Though I do not think it will continue to run properly for long.

Again, the chrono seconds hand is NOT coming into contact with ANYTHING on the dial. I have carefully (through my loupe) watched the minute, hour and chrono seconds move around the dial to be sure they were not contacting any of the hour markers or each other, and they are not. Everything looks perfect, but something is definitely binding the chrono seconds hand or something related to the chronograph.

Ziggy or anyone know the cause and cure?

[Guest avitt]

Is your watch stopping before, during or after the advancement of the minute register?

[freddy333]

Right after, a second or two. But the second register definitely ticks over first.

Weird..

[RWG Technical]

I would suspect that the problem is with the chrono 30 minute timer section, where the center seconds engages and switches it.

Here's what I would do.

Reset the chrono.

Start the Chrono.

With your loop, watch the center seconds following the tab that engages and switches the 30 mintue timer, as the tab reaches and engages into the 30 minute gear, look at what is taking place...my guess is that you will find that the movement stops running not long after the engagement of the tab to the 30 minute gear.

You need to find what is causing the 30minute gear to not turn through a process of elimination...

RG

[Guest avitt]

I had a similar problem with one of my VJ72's. A couple of things come to mind...

Take a stong loupe, and check the teeth of the imtermediary wheel, and the seconds wheel. These teeth are very fine, and even the smallest amount of grit can cause the chrono to stop.

Also check the mesh of the gears...if they are too tight, it can cause the wheels to bind, which may occur at the same point of the rotation. (This clearance can be adjusted by turning the eccentric stud ES-2).

Another consideration may be the seconds wheel tension spring (mounted to the plate, below the seconds wheel). This may be out of alignment, rubbing against the staff of the seconds wheel.

[freddy333]

Ziggy & Avitt -- All of these make sense. I will check & report back.

[Guest avitt]

It doesn't sound like the problem is coming from the minutes register, since you say that the register is advancing before the watch stops (the seconds wheel dart tooth is only in contact with the intermediate wheel very briefly...just long enough to advance the minutes wheel). However, to rule this out as a possible cause, you could remove the minutes wheel altogether...Just remove the hand, remove the bridge, and lift out the wheel. Then you would know if it is the drive side, or the minutes wheel side that is causing the problem.

Edited August 6, 2007 by avitt

[freddy333]

I had a similar problem with one of my VJ72's. A couple of things come to mind...

Take a stong loupe, and check the teeth of the imtermediary wheel, and the seconds wheel. These teeth are very fine, and even the smallest amount of grit can cause the chrono to stop.

Avitt -- You called it exactly right. When I viewed the chrono gearing with a loupe, I found a small piece of grit between one of the teeth of the chrono seconds gear, precisely where the gear was getting stuck. Tapping the chrono second hand (gently) with a toothpick was apparently just enough force to push the gear past that point and get it to continue on its journey. I am sure that, eventually, that little piece of grit would have broken or worn down those two teeth. So it is probably lucky that it caused as much calamity as it did, otherwise I probably would not have found it in time (the teeth look fine). After removing the little 'boulder' with a pair of sharp tweezers, everything is meshing together just fine again.

______________

Which brings me to the final remaining problem -- How to fix the movement into the case so it does not flop around?

I have now exhausted every one of the 2 dozen case straps in my collection that fit the V72's case screws.

I have bent, twisted, filed and mangled these tiny bits of metal for a week now and the movement is still flopping around in the case. Nothing I fabricated has worked. Either they do not hold the movement in place or they are in the way of the case back and keep it from fitting or they bend out of shape as soon as I put the case back on the case. It is hard to believe that these seemingly simple case straps are all that is keeping the Newman project from completion.

Avitt or Ziggy -- Any more ideas for case straps?

[Guest avitt]

Excellent! I'm happy that your problem was so easy to work out

With regard to the case clamps, I'm at a loss. I can tell you that there is a wide variation in case clamp configurations among OEM VJ72 movements. The two that I have are both different, and neither looks like the one that you have. I guess I was furtunate: on one of mine, I was able to use the clamps and screws from a DW mystery movement...on the other, I used the OEM screws to secure the movement:

[freddy333]

Thanks Avitt. Now that I see how yours are put together, I see why I am having so much trouble with this one. It looks like the movement may have been modified specifically to fit the Flytimer's case, which had a very odd construction. Even still, I am surprised by the amount of variation among these movements, especially the method and location for fixing the movement into the case since this is part of the pillar plate (the core of the movement).

Looking at the movement & case, it seems like it ought to be very easy to fabricate a "Z" shaped piece of metal that locks the movement in & fits comfortably around the case back. And I guess if I had a machine shop with alot of metal stock, it would be. But this is proving, by far, to be the most difficult part of the entire procedure. I may end up having to just wedge a few pieces of folded cardboard in between the non-moving sections of the movement & the case to secure things. The idea well has run dry just as I am about to cross the finish line..

[bertieng]

I have the same problem with the clamps. Those come with DW are flat and they just won't secure the movement onto the case groove results in movement swirling around inside the case. Any idea how to use DW's clamp to fix the movt onto the DW case?

Thanks.

[slay]

You dont even wanna know how I fix my movements I would tell you, but I fear I will get bashed by ANY watchmaker reading it

[Guest avitt]

I have the same problem with the clamps. Those come with DW are flat and they just won't secure the movement onto the case groove results in movement swirling around inside the case. Any idea how to use DW's clamp to fix the movt onto the DW case?

Thanks.

As I recall, I had the same problem with the flat clamps. The solution is to give them a slight upward bend. It's easy to do, by holding the clamps in a pair of pliers, and pressing the tip against a hard surface. Here's a picture: