Landeron 248 stopping when chrono function in use.

[JONICURN]

Recently serviced a Landeron 248 and I'm getting 40+ hr power reserve.  Seeing an lower amplitudes of 250 chrono off and 220 chrono on.  New mainspring.  I get full, accurate 40+ hrs when chrono is not activated and between 15min and 2hrs when chrono is activated before movement stops.  Resetting or stopping chrono allows balance to start back up again.  Every time the movement stops, the chrono seconds hand is at 12.  Seems just not enough power to keep advancing the minute recording wheel.   I still feel this new mainspring is the culprit - not giving enough power.  What do you think?

[Delgetti]

I don't think its about the mainspring but the area of the minute recorder. So I would check everything here:

- recorder spring too much tension?

- both bearings (minute recorder and gear) absolutly clean, not oiled and turning freely if blown with a blower

- engagement of finger to gear and gear to minute recorder calibrated correctly by the excenters?

[JONICURN]

On 1/23/2020 at 7:11 AM, Delgetti said:

I don't think its about the mainspring but the area of the minute recorder. So I would check everything here:

- recorder spring too much tension?

- both bearings (minute recorder and gear) absolutly clean, not oiled and turning freely if blown with a blower

- engagement of finger to gear and gear to minute recorder calibrated correctly by the excenters?

Good advice so here's what I did:  removed the minute recorder jumper spring - movement stopped.  Removed minute recording wheel - movement stopped, disengaged sliding gear - movement stopped, Tonight I removed chrono wheel so I will see tomorrow if it stopped again.  Though I doubt it will because as long as chrono function was not in use, movement never stopped.  Never applied any lubricant to chrono or minute pivots or chrono tension spring.  Minute recording wheel and sliding gear both would spin freely with puff of air prior to removal.  Do notice amplitude of 188 at full wind during chrono engagement.  Still stumped.  Thanks so much for your help though. 

[Delgetti]

Ah, ok, as you mentioned 220 Amp with chrono running I didn't think about this area.

 

So here are more candidates:

- remove chrono runner friction spring nd observe amp (to check if tension was too high)

- check engagement of driving wheel-clutch wheel-chrono runner (if its too high and teeth are touching the opposite wheels ground amp will collapse). Do the check with the chrono running for a whole minute in case not all the wheels are 100% concentric.

 

I think you already checked that all bearings are absolutely clean and no teeth are damaged (esp on the runner).

[JONICURN]

Chrono tension spring was decreased, checked,  and also removed with no improvement.   Adjusted eccentric on coupling clutch to go from 30% tooth depth to 70% with no improvement.  No damaged teeth noted and bearings are clean.   Clutch wheel also spins with air puff.  Thinking of just getting another Landeron 248, servicing it and swapping chrono parts out one by one just to find fault.   I appreciate all the help immensely and any new thoughts are greatly appreciated.  

Edited January 28, 2020 by JONICURN

[Delgetti]

Thanks for the update, interesting problem.

But I still didn't understand at which point the drop of amplitude occurs.

Coupling clutch is out of the movement -> movement runs with about 250 amp, right?

Coupling clutch is in the movement, chrono function is activated, chrono runner is out -> movement runs with about 250 amp, right?

And so on, part by part. At which point of this reassembly part by part does the amplitude drop to 188?

 

[rogart63]

I have had one interesting problem with a landeron 148 . The chronograph hand  was either to long or to thick in the tube. If i pressed it on to tight the chronograph stopped . I changed to an other hand and it worked fine. Don't now if this help . As i don't know if you have the hands on . 

[JONICURN]

On 1/28/2020 at 5:06 PM, rogart63 said:

I have had one interesting problem with a landeron 148 . The chronograph hand  was either to long or to thick in the tube. If i pressed it on to tight the chronograph stopped . I changed to an other hand and it worked fine. Don't now if this help . As i don't know if you have the hands on . 

Thanks for the input.  I questioned that myself so I removed all 5 hands and it didn't help

.  

Edited February 2, 2020 by JONICURN

[JONICURN]

On 1/28/2020 at 1:54 AM, Delgetti said:

Thanks for the update, interesting problem.

But I still didn't understand at which point the drop of amplitude occurs.

Coupling clutch is out of the movement -> movement runs with about 250 amp, right?

Coupling clutch is in the movement, chrono function is activated, chrono runner is out -> movement runs with about 250 amp, right?

And so on, part by part. At which point of this reassembly part by part does the amplitude drop to 188?

 

As for the 188 Amplitude, I don't know why it was so low that day.  I did what you said with removing and adding back chrono gears to see where the drop in amplitude was.  See photos.  The movement still stops in chrono mode and still anywhere by 10min and 90 min of chrono usage. Timegrapher set with 42 degrees lift angle. 

Edited February 2, 2020 by JONICURN

[JONICURN]

Just to satisfy my curiosity i am thinking of upgrading the mainspring strength but i'm concerned about rebanking. Standard mainspring size for Landeron 248 is 1.35 x 12.0 x 0.14 x 360mm which is what i used in replacement,   While maintaining a 1.35 width, if wanted to improve amplitude, what would be too thick causing concern for rebanking?  Ofrei offers higher strengths of  0.145mm and 0.16mm.

Edited February 3, 2020 by JONICURN

[nickelsilver]

1 hour ago, JONICURN said:

Just to satisfy my curiosity i am thinking of upgrading the mainspring strength but i'm concerned about rebanking. Standard mainspring size for Landeron 248 is 1.35 x 12.0 x 0.14 x 360mm which is what i used in replacement,   While maintaining a 1.35 width, if wanted to improve amplitude, what would be too thick causing concern for rebanking?  Ofrei offers higher strengths of  0.145mm and 0.16mm.

Your problem isn't the mainspring. However, if you really want to increase the strength I would suggest going to 0.13 thick maximum. Going higher will almost certainly cause rebanking and you will lose power reserve and cause undue stress and wear on the gear train as well.

 

I am fairly convinced that you do have one or more damaged teeth either in the chrono runner or the clutch wheel or both. More likely is the chrono runner. That your problem is consistently with the chrono runner at 12h; this is the position that the coupling clutch engages the chrono from zero and the most likely to exhibit wear or damage. The damage can be very very small, and function OK, until it finds a tooth on the clutch wheel it doesn't like and then bang you're stopped. Just a tiny burr will suffice.

 

 

[JONICURN]

9 hours ago, nickelsilver said:

Your problem isn't the mainspring. However, if you really want to increase the strength I would suggest going to 0.13 thick maximum. Going higher will almost certainly cause rebanking and you will lose power reserve and cause undue stress and wear on the gear train as well.

 

I am fairly convinced that you do have one or more damaged teeth either in the chrono runner or the clutch wheel or both. More likely is the chrono runner. That your problem is consistently with the chrono runner at 12h; this is the position that the coupling clutch engages the chrono from zero and the most likely to exhibit wear or damage. The damage can be very very small, and function OK, until it finds a tooth on the clutch wheel it doesn't like and then bang you're stopped. Just a tiny burr will suffice.

 

 

Thank you, i will investigate that chrono runner further.  What you said made a lot of sense.   I love this forum. 

[JONICURN]

So, I'm embarrassed to say but i noticed a small piece of peg wood in the teeth of the mainspring barrel.  Removed it and now the watch doesn't stop in chono mode.  I learned a lot from you guys though.  Thanks again. 

[Nucejoe]

Thanks to you and delgetti for the complete tutorial on Chrono complication.