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This project started out as a ‘proof of concept’ for me, I wanted to see if this movement could be defused. First I would like to thank a few members for their contributions and inspiration toward finding some ways to make the infamous 2824 CHS timebomb work without worrying about it. Tickleshoes for his original post explaining the workings of the timebomb jump click and it’s fault, Dr Fun Socks for working alongside me from afar in developing some potential fixes, and OldNavitimer for generously providing me with multiple watches and movements to analyze and work on. Thanks guys, this wouldn’t have happened without your help.
You can review some early research into this movement in the link below if interested.
https://forum.replica-watch.info/for...failing/page10
This movement really has two big faults. The jump click can break easily, and the Intermediate Date Wheel (IDW) can be dislodged out of position.
1. The jump click spring can break. The spring is located inside the two part GMT wheel, which is held together by a spring clip. The two halves of the GMT wheel can rotate separately if the click spring is intact. If it breaks, the two halves can be epoxied together. It makes no difference if the broken click spring is left inside the GMT wheel for the gluing, although it can act as a containment border for the glue. Once the halves are glued, the GMT and hour hands will be forever synched, but will retain their proper rotation periods (hour hand two cycles per 24 hours, GMT hand one cycle per 24 hours). Note that you can still create a GMT offset with the GMT hand by manually pressing the GMT hand away from the hour hand with the desired offset.
This broken spring is acting as an epoxy glue border as the two halves are glued together
2. The Intermediate Date Wheel (IDW) has no support arm on it in this movement like it does in a normal 2836 and 2824. It can get cocked up out of position separately from the click spring breaking. This is due to additional forces placed on it by the calendar driving wheel around the times of date change (10PM - 2AM). The result is the hour hand becomes stuck or lags behind or is not responsive to crown movements for as long as the IDW is out of position because the hour wheel has become disengaged. Sometimes the IDW will settle back down into position, sometimes not. The potential for this flaw to occur increases when the GMT wheel is glued together because the click spring is not available to absorb any of the pressure exerted on the solid GMT wheel. The fix to this flaw is a custom made IDW support arm fitted underneath the date jumper maintaining plate.
Here you can see a normal alignment of the IDW and the hour wheel (which sits atop the GMT wheel), and then a pic of the IDW when it gets displaced. This causes the teeth to skip or disengage altogether.
A watchmaker in Belgium has succeeded in manufacturing a more robust jump click spring. You can read about it here.
https://forum.replica-watch.info/for...ebomb-movement
However, even if you have a robust click spring, it will not prevent the IDW flaw from occurring. I have fixed that flaw in several of these movements where the click spring never broke. The IDW flaw may never occur, but it is not uncommon. You can see in this video where the better click spring was installed, the watchmaker had to reset the IDW at 1:20 for the movement to work normally again. It got pushed up out of position.
https://www.youtube.com/watch?v=Hco7...ature=youtu.be
So, if this movement is REALLY going to be worry free, it can benefit greatly from the following mods.
1. Buy and install the better quality click spring.
2. Whatever click spring you have, lubricate it in place in the GMT wheel. There is no manual for this modded movement so there are no lubrication instructions for the unique parts. But the gen 3185-660 jump click calls for lubricating with grease, so the same logic applies to the timebomb jump click. I started using a small blob of Molykote DX under the spring in the GMT wheel and saw an immediate improvement. Also, it stands to reason if it moves more easily it won’t hang up and break as readily.
3. Install the IDW support arm. It’s completely inexcusable that this was overlooked in the development of this movement. Below you can see that both the normal 2836 and the 2824 have a provision for the IDW to remain fixed in its place. The IDW is built into the maintaining plate in the 2824, and the plate covers it in the 2836.
Here’s a comparison shot of the IDW’s
The timebomb plate won’t catch the IDW because its lower gears are too small in diameter. If you turn the movement upside down the IDW can and often does just fall off.
So this mod requires making a support arm that will prevent the IDW from lifting up by pressure exerted on it from the calendar driving wheel. I used .15mm metal plating provided to me by Dr Fun Socks to craft these support arms. You start with a small rectangle, drill a couple holes in it with a bit in a pin vise and then sand/grind it to the desired shape. It takes about 45 minutes. No two that I’ve made are exactly alike, but you just need it anchored under the maintaining plate with a protruding arm.
The IDW support arm needs a slight double bend in it
Test fit looks good
Size comparison
The underside of the maintaining plate has to be filed out a little so it can still function normally
Mod complete
4. Next up is the most fun and exciting mod. Restoring the quickset date function. I was curious if this would work at all and at first did it only on repairs in which the click spring was glued together because otherwise you had to manually wind the hands around 24 hours to change the date. Then I found out on the latest mod in the video below, it can be done while the click spring is intact so you can achieve both hour jumping (forward only, which is best anyway) and have the quickset date feature back. Cool!
So this mod requires filing the hole on the mainplate beneath the date corrector. On the timebomb it’s just a single hole and the corrector doesn’t move. The mainplate is no match for a diamond file, and the hole is extended quite easily. I have come to steer the hole extension upward a little after I filed one a little too far down and the gears lost contact. D’oh.
Next you have to use a 2836 double corrector gear because it has a cam inside it that flips the datewheel. The timebomb corrector gear does not have this cam inside since it doesn’t need it.
Finally, you need to modify a minute train bridge to allow the double corrector to slide back and forth. You can use either a 2836 part and cut off the lower half, or the timebomb part and file down the underside a little. I’ve used both, they work equally well.
2836
Timebomb part
Once you get all your pieces made and installed, check to make sure everything's working right.
Then tear it all down and off to the cleaner for a full servicing.
Now you have a movement that’s not a walking timebomb. You can also put some gen parts in if you want. One that I had to do out of necessity was a gen balance assembly. Sweet.
https://vimeo.com/475575544
Password Meteorite
Thanks for looking!
Sorry, but please don't PM me to do this mod for you. I can't possibly fix all of these!
You can review some early research into this movement in the link below if interested.
https://forum.replica-watch.info/for...failing/page10
This movement really has two big faults. The jump click can break easily, and the Intermediate Date Wheel (IDW) can be dislodged out of position.
1. The jump click spring can break. The spring is located inside the two part GMT wheel, which is held together by a spring clip. The two halves of the GMT wheel can rotate separately if the click spring is intact. If it breaks, the two halves can be epoxied together. It makes no difference if the broken click spring is left inside the GMT wheel for the gluing, although it can act as a containment border for the glue. Once the halves are glued, the GMT and hour hands will be forever synched, but will retain their proper rotation periods (hour hand two cycles per 24 hours, GMT hand one cycle per 24 hours). Note that you can still create a GMT offset with the GMT hand by manually pressing the GMT hand away from the hour hand with the desired offset.
This broken spring is acting as an epoxy glue border as the two halves are glued together
2. The Intermediate Date Wheel (IDW) has no support arm on it in this movement like it does in a normal 2836 and 2824. It can get cocked up out of position separately from the click spring breaking. This is due to additional forces placed on it by the calendar driving wheel around the times of date change (10PM - 2AM). The result is the hour hand becomes stuck or lags behind or is not responsive to crown movements for as long as the IDW is out of position because the hour wheel has become disengaged. Sometimes the IDW will settle back down into position, sometimes not. The potential for this flaw to occur increases when the GMT wheel is glued together because the click spring is not available to absorb any of the pressure exerted on the solid GMT wheel. The fix to this flaw is a custom made IDW support arm fitted underneath the date jumper maintaining plate.
Here you can see a normal alignment of the IDW and the hour wheel (which sits atop the GMT wheel), and then a pic of the IDW when it gets displaced. This causes the teeth to skip or disengage altogether.
A watchmaker in Belgium has succeeded in manufacturing a more robust jump click spring. You can read about it here.
https://forum.replica-watch.info/for...ebomb-movement
However, even if you have a robust click spring, it will not prevent the IDW flaw from occurring. I have fixed that flaw in several of these movements where the click spring never broke. The IDW flaw may never occur, but it is not uncommon. You can see in this video where the better click spring was installed, the watchmaker had to reset the IDW at 1:20 for the movement to work normally again. It got pushed up out of position.
https://www.youtube.com/watch?v=Hco7...ature=youtu.be
So, if this movement is REALLY going to be worry free, it can benefit greatly from the following mods.
1. Buy and install the better quality click spring.
2. Whatever click spring you have, lubricate it in place in the GMT wheel. There is no manual for this modded movement so there are no lubrication instructions for the unique parts. But the gen 3185-660 jump click calls for lubricating with grease, so the same logic applies to the timebomb jump click. I started using a small blob of Molykote DX under the spring in the GMT wheel and saw an immediate improvement. Also, it stands to reason if it moves more easily it won’t hang up and break as readily.
3. Install the IDW support arm. It’s completely inexcusable that this was overlooked in the development of this movement. Below you can see that both the normal 2836 and the 2824 have a provision for the IDW to remain fixed in its place. The IDW is built into the maintaining plate in the 2824, and the plate covers it in the 2836.
Here’s a comparison shot of the IDW’s
The timebomb plate won’t catch the IDW because its lower gears are too small in diameter. If you turn the movement upside down the IDW can and often does just fall off.
So this mod requires making a support arm that will prevent the IDW from lifting up by pressure exerted on it from the calendar driving wheel. I used .15mm metal plating provided to me by Dr Fun Socks to craft these support arms. You start with a small rectangle, drill a couple holes in it with a bit in a pin vise and then sand/grind it to the desired shape. It takes about 45 minutes. No two that I’ve made are exactly alike, but you just need it anchored under the maintaining plate with a protruding arm.
The IDW support arm needs a slight double bend in it
Test fit looks good
Size comparison
The underside of the maintaining plate has to be filed out a little so it can still function normally
Mod complete
4. Next up is the most fun and exciting mod. Restoring the quickset date function. I was curious if this would work at all and at first did it only on repairs in which the click spring was glued together because otherwise you had to manually wind the hands around 24 hours to change the date. Then I found out on the latest mod in the video below, it can be done while the click spring is intact so you can achieve both hour jumping (forward only, which is best anyway) and have the quickset date feature back. Cool!
So this mod requires filing the hole on the mainplate beneath the date corrector. On the timebomb it’s just a single hole and the corrector doesn’t move. The mainplate is no match for a diamond file, and the hole is extended quite easily. I have come to steer the hole extension upward a little after I filed one a little too far down and the gears lost contact. D’oh.
Next you have to use a 2836 double corrector gear because it has a cam inside it that flips the datewheel. The timebomb corrector gear does not have this cam inside since it doesn’t need it.
Finally, you need to modify a minute train bridge to allow the double corrector to slide back and forth. You can use either a 2836 part and cut off the lower half, or the timebomb part and file down the underside a little. I’ve used both, they work equally well.
2836
Timebomb part
Once you get all your pieces made and installed, check to make sure everything's working right.
Then tear it all down and off to the cleaner for a full servicing.
Now you have a movement that’s not a walking timebomb. You can also put some gen parts in if you want. One that I had to do out of necessity was a gen balance assembly. Sweet.
https://vimeo.com/475575544
Password Meteorite
Thanks for looking!
Sorry, but please don't PM me to do this mod for you. I can't possibly fix all of these!
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