Irrational results: timing vs. time keeping

[TempusTortus]

Hello folks,
I am in need of advice regarding a semi-vintage ETA 2846 that I thought I had restored. On the timing machine, I have it adjusted (dial down) to about +1s/d, amplitude around 300, and 0ms BE. When I got to this point I thought I had it made, but not so! I cased the movement, set the time and as I watched, I could see that it was taking more than five seconds for the second hand to go across five seconds on the dial. Fully wound, it looses about 15 minutes per hour in the real world. But - if I put the watch on the timing machine, it still says it's running perfectly.

More info: In the DU position, the results are close to DD. With PU/PD there's a bit of variation, but just a few seconds/day. BE may increase to 0.2ms, but that's it. I've checked to see if there could be drag on the shafts or the hands against the dial or the crystal, but there doesn't appear to be. What have I missed? all ideas welcome.

Many thanks -
James

 

[Chris Radek]

Welcome to the forum!

ETA2846 is a 21600 bph movement. What does your timing machine say for bph when it's giving you this reading?

 

[musicguy]

Welcome to the NAWCC Forum!

moving to watch repair section


Rob

 

[John Runciman]

timing machines are interesting devices. They listen to the sound of the ticking based on that they'd tell you how fast or slow that is. The timing machine makes an assumption as to what the frequency is. that is if it's in the typical auto ranging mode.

ETA2846 is a 21600 bph movement. What does your timing machine say for bph when it's giving you this reading?

if in auto mode for some reason the timing machine decides it's a different frequency then interesting things can occur.
The other thing of interest for a timing machine it doesn't care if you have hands on the watch. It just tells you how closely the balance wheel frequency corresponds to the standard frequency it perceives that it is.

Fully wound, it looses about 15 minutes per hour in the real world.

ETA 2846 that I thought I had restored.

using their word restore is not the same as clean and overhaul necessarily? Did you change any components in the watch? reason I ask about changing components is there are some watches out there that parts will interchange with other calibers of different frequencies. You getting interesting problems if you mix-and-match parts that weren't supposed to go together.

Then the classic problems like the cannon pinion and driver. As this is one of those interesting one is for the Canon pinion snaps together with a wheel and those can definitely go bad. When you try to set the watch does it feel like you've and a friction at all? That would definitely be an issue if that goes bad.





bidfun-db Archive: Watch Movements: ETA 2846

 

[TempusTortus]

Welcome to the forum!

ETA2846 is a 21600 bph movement. What does your timing machine say for bph when it's giving you this reading?

Sadly (I guess) it reads 21,600 whether cased or not, and in every position.

 

[TempusTortus]

timing machines are interesting devices. They listen to the sound of the ticking based on that they'd tell you how fast or slow that is. The timing machine makes an assumption as to what the frequency is. that is if it's in the typical auto ranging mode.



if in auto mode for some reason the timing machine decides it's a different frequency then interesting things can occur.
The other thing of interest for a timing machine it doesn't care if you have hands on the watch. It just tells you how closely the balance wheel frequency corresponds to the standard frequency it perceives that it is.



using their word restore is not the same as clean and overhaul necessarily? Did you change any components in the watch? reason I ask about changing components is there are some watches out there that parts will interchange with other calibers of different frequencies. You getting interesting problems if you mix-and-match parts that weren't supposed to go together.

Then the classic problems like the cannon pinion and driver. As this is one of those interesting one is for the Canon pinion snaps together with a wheel and those can definitely go bad. When you try to set the watch does it feel like you've and a friction at all? That would definitely be an issue if that goes bad.





bidfun-db Archive: Watch Movements: ETA 2846

The tension on the stem while setting the hands feels normal enough. Winding tension is maybe a bit higher than I’d like, but not so high that I’m worried about the stem.

 

[Skutt50]

Haw did it run before you took it apart?

If there is no slippage in the hands, the timing machine is working properly and you still loose 15 minutes per hour something realy fishy is going on......

I once experienced a pocket watch that was crazy on the timing machine but did run well. Turned out someone had replaced a wheel with one that had the wrong number of teeth and adjusted the timing accordingly.

You may have to dissasemble the movement again. The long and boaring job of counting the teeth of the gears would tell you if the wheels are correct or if one wheel with icorrect number of teeth has been installed. By some multiplications and divisions you should be able to tell if e.g. 5 seconds on the seconds hand corresponds to the number of beats of the balance. Since you can tell by observing the seconds hand, that's where I would check i.e. at this point not bother about hour and minute hands.

If that still does not provide an answer you can assemble the parts needed for running the gear train and continue fault finding with a minimum of parts installed.

 

[TempusTortus]

Haw did it run before you took it apart?

If there is no slippage in the hands, the timing machine is working properly and you still loose 15 minutes per hour something realy fishy is going on......

I once experienced a pocket watch that was crazy on the timing machine but did run well. Turned out someone had replaced a wheel with one that had the wrong number of teeth and adjusted the timing accordingly.

You may have to dissasemble the movement again. The long and boaring job of counting the teeth of the gears would tell you if the wheels are correct or if one wheel with icorrect number of teeth has been installed. By some multiplications and divisions you should be able to tell if e.g. 5 seconds on the seconds hand corresponds to the number of beats of the balance. Since you can tell by observing the seconds hand, that's where I would check i.e. at this point not bother about hour and minute hands.

If that still does not provide an answer you can assemble the parts needed for running the gear train and continue fault finding with a minimum of parts installed.

The movement was dead when I received it. It didn’t run at all and was filled with dirt and dust and somewhat corroded. It had seen water, but just enough to create a light patina of rust here and there. I pulled the automatic bridge first and cleaned it. Aside from from some wear, it looked okay: worn, but not quite worn out. The rest of the movement actually looked better with the exception of the barrel bushings, but that’s a bridge I’ll cross another day if I can figure out the timing issue.

I’m thinking of substituting in parts from a 2824/2836 to see how it runs. If swapping power trains works - and I’m not even sure everything is the same - then I’ll compare the two wheel by wheel and go from there. There just aren’t that many possibilities!

 

[gmorse]

Hi Tempus,

Before you start swapping things around, just count the train as Skutt suggests.

Regards,

Graham

 

[John Runciman]

The tension on the stem while setting the hands feels normal enough

is this in the watch case or out of the case? Because often times you can't tell in the case because you're feeling the crown and his gasket not the actual watch itself.

I’m thinking of substituting in parts

before you start mixing and matching and possibly ending up with a new nightmare. When it you disassemble all of the stuff on the dial side down to the Canon pinion assembly and just put the minute hand on and see what happens. Also while the minute hand is on gently push it how easy is it to push? That would be another clue as to whether you have too much slippage there

then if you're going to start mixing and matching parts you want to go to a website like the link below and make sure that the parts you want to swap really interchange with the other movements. Like for instance this balance wheel does not interchange with either the movements you mentioned or for that matter anything its unique to this watch for some reason.

MATERIAL CGI UTILITY