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La Joux Perret G100 stopped on impact - Why?


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A watch running La Joux Perret G100 automatic movement took an impact. The customer indicated that the watch knocked on a table edge quite hard. When inspecting the watch we noticed a small "ding" on the case that would confirm the impact. The impact appears to be on the 9H position of the watch (opposite side to the crown on 3H). The customer indicated that the watch had come to a complete stop upon impact, sent it in for us to look at it. We observed (before opening up the watch) that the crown positions worked flawlessly - winding works, date-setting position works, and the time-setting position works well too. However, no matter what we do, the watch won't run. The seconds hand had stopped at impact and won't move.

Our watchmaker opened the watch, and noticed that the balance had come to a stop. All he had to do was to "release" the power in the mainspring. As soon as he did that, the balance started moving and the watch appeared to be running. When on the timegrapher, the watch kept accurate time with good amplitude within the movement accuracy specifications.

What could have caused the movement to stop like it did on impact? And how could "releasing" the power from the mainspring get the watch started again? Is there a bigger problem in the movement we are missing?

PS: I am not a watchmaker, I am an independent brand owner. I intend to bring issues to this forum that our watchmaker isn't able to identify.

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I’m no expert either, just an enthusiast. From the description and symptoms/fix my fist thought is that the mainspring arbor became dislodged from the mainspring at the hook. When realigned, releasing mainspring tension/rewinding the arbor realigned and engaged properly with the mainspring. I wouldn’t use a G100 to repeat the experiment, however it is in reality a miyota 9015 redesigned to fit the movement diamentions of an ETA 2824 albeit with better materials and quality control that miyota work too. So if trying to recreate the issue the 9015 would be the best bet as it’s orders of magnitude cheaper than a G100.

 

Tom

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31 minutes ago, Microbrandowner said:

A watch running La Joux Perret G100 automatic movement took an impact. The customer indicated that the watch knocked on a table edge quite hard. When inspecting the watch we noticed a small "ding" on the case that would confirm the impact. The impact appears to be on the 9H position of the watch (opposite side to the crown on 3H). The customer indicated that the watch had come to a complete stop upon impact, sent it in for us to look at it. We observed (before opening up the watch) that the crown positions worked flawlessly - winding works, date-setting position works, and the time-setting position works well too. However, no matter what we do, the watch won't run. The seconds hand had stopped at impact and won't move.

Our watchmaker opened the watch, and noticed that the balance had come to a stop. All he had to do was to "release" the power in the mainspring. As soon as he did that, the balance started moving and the watch appeared to be running. When on the timegrapher, the watch kept accurate time with good amplitude within the movement accuracy specifications.

What could have caused the movement to stop like it did on impact? And how could "releasing" the power from the mainspring get the watch started again? Is there a bigger problem in the movement we are missing?

PS: I am not a watchmaker, I am an independent brand owner. I intend to bring issues to this forum that our watchmaker isn't able to identify.

A hard knock can cause a rebank, i had this a few months ago with a Timex, different quality obviously and more likely with a cheap escapement but its something that springs to mind.  Maybe a partial catch up of the impulse pin in the fork that just needed an energy release and re- wind of the barrel.

Thinking about it your watchmaker would have spotted this on close inspection , the impulse pin resting on top of a fork horn so the fault more possibly something non-visible

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49 minutes ago, tomh207 said:

the mainspring arbor became dislodged from the mainspring at the hook

Thank you for this suggestion Tom. It appears to be a logical explanation to the issue. Certainly we won't try to reproduce this with the G100. We have used Miyota 9015 for several years, and have never encountered this in the 9015. We have also been using Sellita SW200-1 recently and have seen this issue once or twice. 

20 minutes ago, Neverenoughwatches said:

A hard knock can cause a rebank

Thank you! I learnt a new term today. However, I looked up rebank and learnt that when a movement "rebanks", the watch is still running (albeit not perfectly). It means that the pallet fork knocks on the balance and it can be audible as "double-ticks".

OTOH, an "overbank" causes the impulse pin to be stuck outside the horns of the pallet fork, thereby putting the escapement "out of action". So this could be an "overbank" of the escapement - because the watch had stopped upon impact and wasn't running at all(?)

The question is then, how does an overbanked escapement start working as soon as the power is released from the main spring. I would assume that an overbanked escapement will need the watchmaker's intervention to fix the impulse pin in position for the escapement to start working again?

My gut feeling is that there is something wrong with the balance - additional information: after monitoring the movement for two days, we tested again after casing up - the watch is suddenly off the charts - amplitude is all over the place, accuracy is not within bounds, and beat errors show up. Of course we decided to switch to a new movement on the customers watch, but I'd prefer to get to the bottom of this so we can handle this if it comes up again.

Edited by Microbrandowner
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Hi. It is quite possible that the shock system was temporarily displaced stopping the balance from operating and the subsequent letting down of the mainspring and incursion into the watch caused it to restart., I would check that both systems are seated correctly and not acting on the balance pivots. Might be prudent to check the balance staff for a bent pivot.

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11 minutes ago, Microbrandowner said:

Thank you for this suggestion Tom. It appears to be a logical explanation to the issue. Certainly we won't try to reproduce this with the G100. We have used Miyota 9015 for several years, and have never encountered this in the 9015. We have also been using Sellita SW200-1 recently and have seen this issue once or twice. 

Thank you! I learnt a new term today. However, I looked up rebank and learnt that when a movement "rebanks", the watch is still running (albeit not perfectly). It means that the pallet fork knocks on the balance and it can be audible as "double-ticks".

OTOH, an "overbank" causes the impulse pin to be stuck outside the horns of the pallet fork, thereby putting the escapement "out of action". So this could be an "overbank" of the escapement - because the watch had stopped upon impact and wasn't running at all(?)

The question is then, how does an overbanked escapement start working as soon as the power is released from the main spring. I would assume that an overbanked escapement will need the watchmaker's intervention to fix the impulse pin in position for the escapement to start working again?

My gut feeling is that there is something wrong with the balance - additional information: after monitoring the movement for two days, we tested again after casing up - the watch is suddenly off the charts - amplitude is all over the place, accuracy is not within bounds, and beat errors show up. Of course we decided to switch to a new movement on the customers watch, but I'd prefer to get to the bottom of this so we can handle this if it comes up again.

Haha actually i got 2 terms mixed up its not rebank its overbank lol

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10 minutes ago, Microbrandowner said:

Thank you for this suggestion Tom. It appears to be a logical explanation to the issue. Certainly we won't try to reproduce this with the G100. We have used Miyota 9015 for several years, and have never encountered this in the 9015. We have also been using Sellita SW200-1 recently and have seen this issue once or twice. 

Thank you! I learnt a new term today. However, I looked up rebank and learnt that when a movement "rebanks", the watch is still running (albeit not perfectly). It means that the pallet fork knocks on the balance and it can be audible as "double-ticks".

OTOH, an "overbank" causes the impulse pin to be stuck outside the horns of the pallet fork, thereby putting the escapement "out of action". So this could be an "overbank" of the escapement - because the watch had stopped upon impact and wasn't running at all(?)

The question is then, how does an overbanked escapement start working as soon as the power is released from the main spring. I would assume that an overbanked escapement will need the watchmaker's intervention to fix the impulse pin in position for the escapement to start working again?

My gut feeling is that there is something wrong with the balance - additional information: after monitoring the movement for two days, we tested again after casing up - the watch is suddenly off the charts - amplitude is all over the place, accuracy is not within bounds, and beat errors show up. Of course we decided to switch to a new movement on the customers watch, but I'd prefer to get to the bottom of this so we can handle this if it comes up again.

What gets confusing at times is different people at different times in our learning journey use terms incorrectly or interchangeably. My interpretation of rebanking and overbanking matches yours.

 

now with some additional data it does sound very much like the shock was enough to damage the escapement and that would be the place to investigate thoroughly.

 

Tom

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30 minutes ago, Neverenoughwatches said:

A hard knock can cause a rebank, i had this a few months ago with a Timex, different quality obviously and more likely with a cheap escapement but its something that springs to mind.  Maybe a partial catch up of the impulse pin in the fork that just needed an energy release and re- wind of the barrel.

Thinking about it your watchmaker would have spotted this on close inspection , the impulse pin resting on top of a fork horn so the fault more possibly something non-visible

Lol too early in the morn for me. Rebank is too much amplitude, causing the impulse pin to bank into the opposite side of a fork horn. Overbank is the impulse pin has jumped over a fork horn causing a non release of the escapement,  halting the watch, apologies its best i wake up properly before i answer anything else 😄

2 minutes ago, tomh207 said:

What gets confusing at times is different people at different times in our learning journey use terms incorrectly or interchangeably. My interpretation of rebanking and overbanking matches yours.

 

now with some additional data it does sound very much like the shock was enough to damage the escapement and that would be the place to investigate thoroughly.

 

Tom

Haha i just caught that mistake in my head Tom before you commented 

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21 minutes ago, Microbrandowner said:

Thank you for this suggestion Tom. It appears to be a logical explanation to the issue. Certainly we won't try to reproduce this with the G100. We have used Miyota 9015 for several years, and have never encountered this in the 9015. We have also been using Sellita SW200-1 recently and have seen this issue once or twice. 

Thank you! I learnt a new term today. However, I looked up rebank and learnt that when a movement "rebanks", the watch is still running (albeit not perfectly). It means that the pallet fork knocks on the balance and it can be audible as "double-ticks".

OTOH, an "overbank" causes the impulse pin to be stuck outside the horns of the pallet fork, thereby putting the escapement "out of action". So this could be an "overbank" of the escapement - because the watch had stopped upon impact and wasn't running at all(?)

The question is then, how does an overbanked escapement start working as soon as the power is released from the main spring. I would assume that an overbanked escapement will need the watchmaker's intervention to fix the impulse pin in position for the escapement to start working again?

My gut feeling is that there is something wrong with the balance - additional information: after monitoring the movement for two days, we tested again after casing up - the watch is suddenly off the charts - amplitude is all over the place, accuracy is not within bounds, and beat errors show up. Of course we decided to switch to a new movement on the customers watch, but I'd prefer to get to the bottom of this so we can handle this if it comes up again.

Absolutely correct , you caught me. Its actually really easy to remember which is which, overbanked the impulse pin has jumped OVER the fork horn, no eyed 🐐 how i fluffed that 🤣

1 minute ago, watchweasol said:

Hi  @Neverenoughwatches   The term I learnt was overbanked meaning that the fork and the impulse pin were displaced, the impulse pin being on the wrong side of the horn. This is due to a shock/knock causing the fork to jump to the wrong side during the oscillation of the balance and the balance returns to rest outside the horn

Ok i know i know , can all stop ragging on me now , ive only just woke up 🤣🤣🤣🤣

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28 minutes ago, Microbrandowner said:

Thank you! I learnt a new term today. However, I looked up rebank and learnt that when a movement "rebanks", the watch is still running (albeit not perfectly). It means that the pallet fork knocks on the balance and it can be audible as "double-ticks".

👍It makes a galloping sound within the movement 

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51 minutes ago, watchweasol said:

Hi @Neverenoughwatches  you will feel better after your coffee and toast,  by the way the Sun is shining in Scotland.

Haha i had a crap night's sleep after an evening of junk food, the missus exiled me to the sofa, my stomach was making the strangest of noises. Alls forgiven now , treating me to a breakfast out 🤣

50 minutes ago, RichardHarris123 said:

I don't think it could of overbanked as letting down the power wouldn't make the impulse jewel move to the correct side of the fork.

Possibly a partial catch Rich, pin resting on top of a horn. 

1 hour ago, Microbrandowner said:

The question is then, how does an overbanked escapement start working as soon as the power is released from the main spring. I would assume that an overbanked escapement will need the watchmaker's intervention to fix the impulse pin in position for the escapement to start working again?

A fully overbanked escapement would need the balance removing and replacing. Possible that the impulse pin was just caught half way, sat on a fork horn, I'd expect your repair guy would have picked that up easily.  But an unwinding and rewind of the mainspring might have been enough to drop the pin back inside the fork slot. This might account for the tg snowstorm, damage to the pivots of the balance or the pallet fork, movement of the fork's guard pin, damage/displacement to pallet stones/impulse pin. Check all these areas,  the safety clearances may have changed. 

Does this look like an attempt to redeem myself  🤣🤣🤣🤣🤣.

Edited by Neverenoughwatches
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1 hour ago, watchweasol said:

Hi @Neverenoughwatches redemption.  Hell no.  You got your thinking head on. Where are you having brekkies,  full English .?…..

.

Haha yes WW just got back , the missus treat me to a full English in Beverley,  you might remember that place,  from your time in Hull , a small town just outside of Hull. perhaps your brother has mentionded it ?  Getting too old for evening snack binges, plays havoc aging digestive system 😄

30 minutes ago, oldhippy said:

It could be as simple as a speck of dirt had lodged in the train and by letting the power off it released it from its place and moved out of the way. You won't find the true problem until you take it apart and inspect all the parts. 

👍 that simple, doesn't take much to stop low torque wheels like the escape wheel, a small hair fibre caught up at either end of the lever. 

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Like any somewhat modern movement, the Miyota 9015 has a safety roller, and a pallet fork a guard pin, making it impossible to overbank. I agree with OH, no need to speculate. Take it apart and investigate!

Edited by VWatchie
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If due to a shock, impulse jewel jumps over a horn of the fork !    it remains  stuck between the horn it betrayed and banking pin, in such case  no amount of power let down lets impulse jewel get back to where it belongs.

Letting the power down is good practice whenever you intend to remove the fork.  

Weasel's advice is plausible, but your repairman must have either raised the balance cock a bit or pushed down on the fork horn 🫣    to clear the way for impulse back in between the horns.

The escapement must be checked now, as it might need/ have needed  adjusting.

I wont worry about a pivot having been bent, cuz timegrapher has already said, 

WE FEEL GOOD DOWN HERE, HOW ABOUT YOU GUYS.   

Please give some wind now, says the poor watch.

Rgds

Edited by Nucejoe
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54 minutes ago, VWatchie said:

Like any somewhat modern movement, the Miyota 9015 has a safety roller, and a pallet fork a guard pin, making it impossible to overbank. I agree with OH, no need to speculate. Take it apart and investigate!

👍in normal running circumstances H, but the impact may have damaged a safety feature allowing an overbank to occur. Without a gaurd pin tracking the safety roller to bump off, a quick flick of the wrist can trigger an overbank.

Caught halfway might be the only overbank scenario to explain a restart without intervention 

The impulse pin could have been caught right at the tip of the horn, its not forced to jump completely to the opposite side, releasing tension on the lever after unwinding the mainspring may have been enough to reposition the pin back in the fork slot 🤷‍♂️.  Waaayyy too much speculation,  time to move on . A disney song from Frozen now springs to my mind   "Let it go, let it go"  

Edited by Neverenoughwatches
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@Neverenoughwatches yes, you've redeemed yourself now, sir 🙂

Thanks everyone for participating in the discussion. From all the responses, I have drawn out a few possible causes of the problem:

1) The sudden impact to the watch caused an overbank that resulted in the watch to stop abruptly. This doesn't explain how the watch started without an intervention to the escapement.

2) The sudden impact to the watch caused a "partial overbank" that caused the watch to stop. (Thanks @Neverenoughwatches for proposing this theory). This explains how no intervention was required to get the watch started again.

3) A lose speck of dirt remained in the watch (perhaps during the assembly and casing of the watch) that lodged itself in the gear train during the impact. This must have caused the abrupt stop, and also explains how no intervention was required to get the watch started again. (Thanks @oldhippy for this theory).

4) The cause was none of the above, the entire movement has to be taken apart and inspected to identify root cause.

I mentioned earlier that after 2-3 days of monitoring, this watch has again started showing issues on the TG - off the charts amplitude, accuracy, and beat errors. So a thorough investigation is required. I will ask our watchmaker to do this and come back with any observations. 

Cheers and have a great Sunday everyone!

Over and out.

 

Edited by Microbrandowner
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12 minutes ago, Microbrandowner said:

The cause was none of the above, the entire movement has to be taken apart and inspected to identify root cause.

I can varify without doubt that the root cause was a rather hard knock on the edge of a table ( I definitely have it right this time ) As to the remaining issue please let us know what your watch guy finds. Its ok you can just tell me i can keep secrets.

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3 minutes ago, Neverenoughwatches said:

rather hard knock on the edge of a table

This opens a can of worms though - our watch cases are made of 316L Steel, 10 ATM water tightness, Sapphire crystals. We don't use plastic movement holders, and only use metal movement holders. Second - the movement is LJP G100. I am confident it is built with some form of shock resistance - either Novodiac, or Incabloc. The watches are built well - and it is shocking (no pun intended) to hear that a hard knock on the table could cause the watch to come to a complete stop. Could a knock to the table or a door-knob cause the movement to overbank? Are modern-day Swiss movements that easy to break? OTOH, the speck of dust argument is more likely, and explains why the watch would stop.

 

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