Landeron 248 setting eccentric studs

[Jon]

Hi guys,

I wrote a set of five lessons for my second year students regarding the Landeron 248 chronograph watch, which incidentally we are meeting tonight. They are going to be polishing pivots and pinion leaves of their 248s, before putting the movements through the cleaning machines.

This is number one of five. I posted number two of five the other day HERE

 

There are seven eccentric studs on this movement, so understanding what the studs do, how to set them, their actions and interactions with other parts of the chronograph mechanism is vitally important.

I found there is very little out there on the internet to help understand the principles of these eccentric studs, especially video content to show various faults and alleviations, so I put together quite detailed walkthroughs of various complicated movements usually consisting of 15 to 18 hours of learning/servicing in the workshop per movement/module

With any watchmaking, especially with complicated work, only make one adjustment and measure the results, if any. Be methodical in your approach.

The lesson was originally in PowerPoint and I had to convert it to PDF to post here, so a lot of the video content won't play, but the PowerPoint version is in my cloud storage here.

https://docs.google.com/presentation/d/10KJJ58P0v2BglKZSilIv9o69xBsbrQPI/edit?usp=sharing&ouid=107902587627140904870&rtpof=true&sd=true

You'll need quite a newer version of Microsoft Office (PowerPoint) so the video content will play, otherwise it won't. I hope you find this lesson useful and begin to get a better understanding of how to set eccentric studs. Sometimes you'll come across a stud that is too loose, or even too tight. Usually if one is problematic it will be because it is loose. This can't be left, as the stud will turn whilst the chronograph is stopped, started and reset, throwing the chrono mechanism setting off which could lead to the movement grinding to a halt. Don't fool yourself in thinking it will hold. Either a replacement stud is fabricated to suit the enlarged hole, or the hole can be closed up. In turning and setting the eccentric studs prior to disassembly of the movement, we are able to set the chronograph mechanism, especially the minute register mechanism correctly and test for any faults, such as a bent wheel over fourth arbor, or incorrect depth of the dart tooth with the sliding gear, or a mis-set minute runner jumper spring, to name a few possible faults and mis-settings. Also in turning these eccentric studs we can gain a 'feel' for how tight they are in the mainplate or bridge. The more they are turned the more the chance of the stud becoming looser increases. So once set correctly prior to cleaning, the less chance they will need setting once the chrono mechanism is assembled, only if a stud isn't tight enough in its setting in the first place.

This is for setting Landeron 248 eccentric studs, but once an understanding of their uses and actions is gained through theoretical aspects together with practical application, then this skill and knowledge can be used in most vintage chronographs to set their eccentric studs and even in modern timepieces where you'll find very few eccentric studs, such as an Omega Speedmaster or Tag Heuer Calibre 01 chronographs

Enjoy!

 

Lesson 22. Landeron 248 Chronograph.pdf

[RichardHarris123]

1 hour ago, Jon said:

Hi guys,

I wrote a set of five lessons for my second year students regarding the Landeron 248 chronograph watch, which incidentally we are meeting tonight. They are going to be polishing pivots and pinion leaves of their 248s, before putting the movements through the cleaning machines.

This is number one of five. I posted number two of five the other day HERE

 

There are seven eccentric studs on this movement, so understanding what the studs do, how to set them, their actions and interactions with other parts of the chronograph mechanism is vitally important.

I found there is very little out there on the internet to help understand the principles of these eccentric studs, especially video content to show various faults and alleviations, so I put together quite detailed walkthroughs of various complicated movements usually consisting of 15 to 18 hours of learning/servicing in the workshop per movement/module

With any watchmaking, especially with complicated work, only make one adjustment and measure the results, if any. Be methodical in your approach.

The lesson was originally in PowerPoint and I had to convert it to PDF to post here, so a lot of the video content won't play, but the PowerPoint version is in my cloud storage here.

https://docs.google.com/presentation/d/10KJJ58P0v2BglKZSilIv9o69xBsbrQPI/edit?usp=sharing&ouid=107902587627140904870&rtpof=true&sd=true

You'll need quite a newer version of Microsoft Office (PowerPoint) so the video content will play, otherwise it won't. I hope you find this lesson useful and begin to get a better understanding of how to set eccentric studs. Sometimes you'll come across a stud that is too loose, or even too tight. Usually if one is problematic it will be because it is loose. This can't be left, as the stud will turn whilst the chronograph is stopped, started and reset, throwing the chrono mechanism setting off which could lead to the movement grinding to a halt. Don't fool yourself in thinking it will hold. Either a replacement stud is fabricated to suit the enlarged hole, or the hole can be closed up. In turning and setting the eccentric studs prior to disassembly of the movement, we are able to set the chronograph mechanism, especially the minute register mechanism correctly and test for any faults, such as a bent wheel over fourth arbor, or incorrect depth of the dart tooth with the sliding gear, or a mis-set minute runner jumper spring, to name a few possible faults and mis-settings. Also in turning these eccentric studs we can gain a 'feel' for how tight they are in the mainplate or bridge. The more they are turned the more the chance of the stud becoming looser increases. So once set correctly prior to cleaning, the less chance they will need setting once the chrono mechanism is assembled, only if a stud isn't tight enough in its setting in the first place.

This is for setting Landeron 248 eccentric studs, but once an understanding of their uses and actions is gained through theoretical aspects together with practical application, then this skill and knowledge can be used in most vintage chronographs to set their eccentric studs and even in modern timepieces where you'll find very few eccentric studs, such as an Omega Speedmaster or Tag Heuer Calibre 01 chronographs

Enjoy!

 

Lesson 22. Landeron 248 Chronograph.pdf 9.08 MB · 3 downloads

Hello Jon, I  get this.

[rossjackson01]

Thank you Jon. Although I will never get to work on such. So interesting and informative.

[RichardHarris123]

13 minutes ago, rossjackson01 said:

Thank you Jon. Although I will never get to work on such. So interesting and informative.

Could you open it?

[rossjackson01]

36 minutes ago, RichardHarris123 said:

Could you open it?

Oh yes. Both of them. Pdf document and PowerPoint in 'Office Libre'.

[nevenbekriev]

I opened it too, and can asure that it is good and thorough.

I can add something little for the minutes counter adjustment (will use the terms from this presentation) - sometimes is prefferdd that the T-line will be slightly tilted as to alow little bigger gap between the the tooth A and the dart tip, and the gap of C tooth is reduced to almost 0, as shown on the picture (from manual for 3133)

Also, there is one more option, offering the same result as the changing lenght of the dart or slope of the hammer head - this is changing the position of the heart on the minutes counter wheel. Sometimes just turning hte heart upside down changes slightly the wheel position and thus one can choose the better between the two. Then, the heart position can be totally changed by making new hole for the screw that fixes the heart

[Sirius]

If you have no Powerpoint at Hand (but Libre-Office or whatever..),

to get Access to the Videos in the pptx, make a Copy of the File, rename it to blabla.zip and unzip the File.

Now in the Folder ppt/media you have all Pictures and Videos......

 

hope this helps some of us

regards,

Ernst

[rossjackson01]

Sirius. Thank you for helping others with that information. This is why this forum is so good.

[Jon]

On 4/22/2024 at 7:42 PM, nevenbekriev said:

I opened it too, and can assure that it is good and thorough.

Thank you. I spent a lot of time on that.

 

On 4/22/2024 at 7:42 PM, nevenbekriev said:

sometimes is preferred that the T-line will be slightly tilted as to allow little bigger gap between the the tooth A and the dart tip, and the gap of C tooth is reduced to almost 0, as shown on the picture (from manual for 3133)

It never ceases to amaze me that there are so many slight adjustments that can be made to the chronograph mechanism through setting the eccentric studs to get them all to a concerto, like an orchestra with everything in time and to its most optimum. Understanding that setting one stud to the desired effect may throw another out is the fun of working on vintage chronographs.

Great pic of the 3133 dart tooth interaction and tilt of the tooth. I love working on 3133s. Slightly better than the 7733 in my opinion and you get a date at 6!

[RichardHarris123]

It opened today, excellent as usual. 

[Klassiker]

So much work has gone into this! Thanks again @Jon. I will go back and check my adjustments from last weekend.

A few questions for you, if you don't mind.

In the reset position, I can understand the problem if the gap between the hammer and the minute counter heart is too big (slide 77) but what is bad about both hammers being in contact with the cams (slide 76)?

I read somewhere that Landeron recommended grease on the runner cam, but the minute counter heart should be dry. Is that so, and why?

How many tads in a ligne?

[Jon]

On 4/24/2024 at 6:08 PM, Klassiker said:

In the reset position, I can understand the problem if the gap between the hammer and the minute counter heart is too big (slide 77) but what is bad about both hammers being in contact with the cams (slide 76)?

In some chronographs, this is what happens. The hammers are hard against both cams in a 7750, but in the 248, it's the jumper spring that gets the cam to the correct position. The hammer gets the minute runner to a certain point when the jumper spring snaps the counter into poisition.

 

On 4/24/2024 at 6:08 PM, Klassiker said:

I read somewhere that Landeron recommended grease on the runner cam, but the minute counter heart should be dry. Is that so, and why?

Both hammers or cams should be greased. Only the minute runner arbor isn't greased.