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Why does the "correct" mainspring for ETA 2804 not fit ?


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Rebuilding an ETERNA with an ETA 2804 movement.

I got a new mainspring - listed on Cousins as GR3149

1435087252_Screenshot2020-10-01161425.thumb.png.f63ae0ed99b6b1a443e3e04ce7bc0337.png

The barrel measures about 11.1 mm, so all seemed well.

But when it came to fit, it doesn't by about 0.5 mm

So, unwind it, and use a spring winder.

Then discover the inner coil is way too big (I don't think I opened it up much to fit the winder) ..... and of course, it broke when trying to tighten the curve. Grrrr (why does this one cost so much !!)

Checking on other sources e.g. GR tables ( https://www.cousinsuk.com/document/category/mainsprings-by-size-watch-pocket ) gives the size as 11.5 mm

679214321_Screenshot2020-10-01162217.png.bb759ce0e79e572e3a08c1d9f1e31f9a.png 

If it's the correct spring, why doesn't it fit ?

 

Mike

 

 

 

Edited by mikepilk
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  • mikepilk changed the title to Why does the "correct" mainspring for ETA 2804 not fit ?
17 minutes ago, watchweasol said:

Hi Mike  Dr Ranfft quotes the spring as   1.20 X 11.0 X 0.125 X 370     yours at 420 I would have thought was close enough.

It's not the length, it's the diameter of 11.5 mm which doesn't fit the barrel. And the inner coil seems too big for the arbor. 

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It seems to be increasingly common that the inner hooking on these GR springs snap. I do wonder if they aren’t annealed correctly at the factory. 
 

You could try punching a new hole. Can do that with a small flat punch on the staking set and then file rectangular.

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8 hours ago, rodabod said:

It seems to be increasingly common that the inner hooking on these GR springs snap. I do wonder if they aren’t annealed correctly at the factory. 
 

You could try punching a new hole. Can do that with a small flat punch on the staking set and then file rectangular.

Good idea. I have tried that before and failed. It's very difficult trying to work on the inner coils. And I'm not sure I have a punch small enough.

Edited by mikepilk
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I think I can answer my own question. 

I assumed it was a standard ETA 2804 movement - I didn't realise that Eterna used modified versions.

I had wondered about the "1" stamped above the 2804, making it a 12804 Eterna movement. The mainspring for this is listed by Cousins as GR2976 - different to the ETA 2804

953525488_Screenshot2020-10-04161650.png.6e20ad94ece722006722533bc39949c8.png

There's also "064" stamped on the mainplate. Any ideas what that means ?

 

 

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I've had these issues with questionable mainspring sizes for barrel sizes.

Point is, never take what Cousins says as the truth when it come s to mainspring sizes. I check out different sources and invariably go with what Ranfft has in his database. I too think GR mainsprings have some issues. I had one completely bend its hook rendering it completely useless, as it just slipped like an auto and gave about 5 hours power reserve. One month of use shouldn't do that!

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10 minutes ago, Jon said:

I've had these issues with questionable mainspring sizes for barrel sizes.

Point is, never take what Cousins says as the truth when it come s to mainspring sizes. I check out different sources and invariably go with what Ranfft has in his database. I too think GR mainsprings have some issues. I had one completely bend its hook rendering it completely useless, as it just slipped like an auto and gave about 5 hours power reserve. One month of use shouldn't do that!

I use RANFFT as a database, but don't assume it is always correct e.g. The spring size for ETA 2804  does not agree with Cousins' listing, or the listing in the GR tables ( https://www.cousinsuk.com/document/category/mainsprings-by-size-watch-pocket )

WatchGuy also has a list of mainsprings here https://watchguy.co.uk/cgi-bin/mainsprings

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  • 2 weeks later...

And, another mainspring broken trying to fit it to the arbor. This is getting silly !
I've never had so much trouble trying to fit a non-auto spring

Has anyone found a list of the approximate arbor size for mainsprings?

The spring listed by Cousins for Eterna 12804 is  GR2976  1.20 x 0.12 x 380 x 11 
As the previous spring sized as "11" didn't fit, I got a 1.20 x 1.25 x 360 x 10.5

Again, the centre coil was much too big (the arbor is only 2.3mm) so I ordered some round nosed pliers.
I could only reduce the inner coil diameter by so much, by inserting one side of the pliers in to the coil and twisting.

The only way I could reduce the coil diameter further was pushing inwards on the outer edges of the inner coil.
And, again, it buckled. 

If I order (the third) and 'correct' spring GR2976 - is the inner coil going to be too large ?

If so, how can I safely reduce it. 

 

 

 

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According to my GR 2 book the spring you originally purchase should fit:

 GR 3149  1.25x0.125x420x11.5

If the centre is too large for the arbour then it needs closing down. To do this without braking or distorting the spring the inside of the coil needs supporting with something that is round ie brass bar or a screwdriver shaft etc.  There certainly should be enough wriggle room to accommodate the 0.05mm. 

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10 minutes ago, clockboy said:

According to my GR 2 book the spring you originally purchase should fit:

 GR 3149  1.25x0.125x420x11.5

If the centre is too large for the arbour then it needs closing down. To do this without braking or distorting the spring the inside of the coil needs supporting with something that is round ie brass bar or a screwdriver shaft etc.  There certainly should be enough wriggle room to accommodate the 0.05mm. 

Hi @clockboy

The GR3149 is for an ETA 2804, which is what I assumed, as that's stamped on the baseplate. But there's a "1" stamped just above it, making it an Eterna 12804, which uses GR2976

GR 3149 is 0.5 mm too large, not 0.05 mm, and it definitely won't fit !

Edited by mikepilk
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In my GR  book there is no Eterna 12804 listed. GR 2976 is for Damas various & Eta,s various. I suggest you take measurements from the original spring. 

 

Maybe a Eterna 12801 (ETA 2801) = spring size 1.20 x 11.0 x 0.125 x 370mm

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1 hour ago, clockboy said:

In my GR  book there is no Eterna 12804 listed. GR 2976 is for Damas various & Eta,s various. I suggest you take measurements from the original spring. 

 

Maybe a Eterna 12801 (ETA 2801) = spring size 1.20 x 11.0 x 0.125 x 370mm

Eterna 12804 is the same as 2801 but with a calendar.

That's the size of spring I need - but what I want to know, is will it fit the arbor?

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  • 2 years later...
On 10/15/2020 at 10:02 PM, mikepilk said:

Eterna 12804 is the same as 2801 but with a calendar.

That's the size of spring I need - but what I want to know, is will it fit the arbor?

@mikepilk

Did you ever get this figured out? Having a GR3149 in my Cousins basket right now for a Hamilton housing an ETA 2804-2. But thought I'd wait for your input before I press the Checkout button.

The GR3149 (1.25 x .125 x 420 x 11 Non-Automatic) is recommended by http://cgi.julesborel.com/cgi-bin/matcgi2?ref=[cZDXJ\ and https://www.emmywatch.com/db/movement/eta--2804-2/

The GR2984 (1.20 x .125 x 380 x 11 Non-Automatic) is the closest I could find as specified by http://www.ranfft.de/cgi-bin/bidfun-db.cgi?10&ranfft&&2uswk&ETA_2804_2

The ETA2801770 (1.23 x .134 x 400 x 10.5 Non-Automatic) is recommend by Cousins https://www.cousinsuk.com/search?searchTerm=ETA2801770

Really confusing, and having to try to adjust the inner coil doesn't sound like much fun, at all 😬

Edited by VWatchie
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I never figured it out. Cost me 3 springs in the end with breakages.

You could try any of the above, but the critical thing I found was the inner coil size. I don't know why they made it so small - I mention above 2.3mm.  

All you can do is get your round nose pliers ready, anneal the inner coil, and hope it doesn't break. 

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3 hours ago, mikepilk said:

but the critical thing I found was the inner coil size

The problem would be that's not a specified size in the mainspring catalogs. I run into this occasionally with pocket watch mainsprings where they are more of a generic spring and the not taking into account the inner size. Where most of the time with a lot of annoyance and fiddling around I can get the arbor in most of the time. The worst problem is as when there to being then they have to be carefully closed without breaking them. But I think really what's going on is there more of a generic spring and because there is no specification that's where the problem becomes.

Out of the mainspring catalogs their recommendations

image.png.6d2cf7349df877714bd780238e3273f0.png

The problem with the catalog itself is its vintage and we don't have the -2 calibers and does that change anything?

image.png.6a570f940f9a34a76a4b1b2b4136e359.png

image.thumb.png.a72576e1f1145244a5806ca9848cf201.png

3 hours ago, VWatchie said:

ETA 2804-2.

On 10/1/2020 at 8:30 AM, mikepilk said:

ETA 2804

Wondering if there was a difference went to the bestfit online and it looks like at least for the barrel no difference at all

image.png.ec773fa2c8cfd534a9e656fc299e3a8e.png

Not going to the whole list but looks like basically everything is identical although apparently could have purchased a chronometer grade balance wheel have to wonder if that was ever available?

image.png.6bbc8bb0a89e4aafa6d1699dd9f62126.png

Then just because I'm here let's get some cross reference numbers

image.png.884d7ba973d481eb05f6d7e2be21cadc.png

Okay I decided to reread the entire discussion because we all seem be ending up with the exact same place.

On 10/4/2020 at 8:20 AM, mikepilk said:

I assumed it was a standard ETA 2804 movement - I didn't realise that Eterna used modified versions.

Always the problem with the modification as we don't know what they modify

On 10/1/2020 at 3:54 PM, rodabod said:

It seems to be increasingly common that the inner hooking on these GR springs snap. I do wonder if they aren’t annealed correctly at the factory.

If you had a blued steel spring then the other part is not hardened But these modern white spring as they are hardened which is of course why they break. It's also why the mainspring winders themselves have a different kind of hook for the white Springs versus the blue because they are so tightly made there supposed to go on very specific arbors. This is also why is this specific mainspring winders sets for exact Springs.

Thinking of mainspring winders I'm attaching a PDF that someone else in the group had previously given us.

On 10/1/2020 at 8:30 AM, mikepilk said:

unwind it, and use a spring winder.

Which Winder in other words which exact Winder one of the one specified for a eta watch or one of the generic ones?

On 10/1/2020 at 12:12 PM, mikepilk said:

It's not the length, it's the diameter of 11.5 mm which doesn't fit the barrel. And the inner coil seems too big for the arbor.

It looks like for the PDF the barrel diameter is 10.9 at least that's with the tool is using so that should drop in. Don't know about the handle parts

another thing to try when you're closing of the center part is to put something inside so a new trying to squeeze with your pliers you can't squeeze beyond a certain point I find that's where things break like what I'm doing a pocket watch spring I put a piece of piglet in and then what I squeeze that keeps me from squeezing too much and if you're really patient you can actually squeeze without tempering. Although I usually let my boss do that can be seems be really good at doing it without breaking it. But something in the middle does keep you from squeezing to budge otherwise tempering would be the way to go.

It appears to be that everything takes us right back to the exact same place where you started from. A mainspring company in Switzerland making a generic replacement spring that doesn't actually fall exacting specifications like they should. It's all goes back to if we could get original mainsprings somewhere in the universe something that did not come from this one particular company.

I was looking at a different mainspring list I think the problem is the half sizes in both the width and the thickness. Which is why some of the sites dropped the half-size and just go a little smaller and thinner. Then looking for mainspring I stumble across barrel complete top right-hand side of the page. You get a part number 182/1280A I wonder if anyone else has this that would solve the problem?

https://www.ofrei.com/page1439.html#35376

 

HJ-Mainspring-Winders.pdf

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14 hours ago, JohnR725 said:

.... I'm doing a pocket watch spring I put a piece of piglet in and then what I squeeze that keeps me from 

I think you might be in trouble with the animal rights activists 🤣🤣

Since first posting, I am much better at manipulating the coils. Using round nose pliers made the biggest difference. I do put something round in the coil to stop it squashing - tube, screwdriver blade, rarely anything porcine. I've successfully reduced many coils since.

But, the problem with the above spring is that the inner coil needs to be reduced by so much, and to about 2.3mm. Round nose pliers are not fine enough. When reducing the inner coil, you need to squeeze it smaller than 2.3mm for it to deform.  It's very hard to do at that size.

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  • 3 months later...
On 6/22/2023 at 2:50 PM, VWatchie said:

@mikepilk

Did you ever get this figured out? Having a GR3149 in my Cousins basket right now for a Hamilton housing an ETA 2804-2. But thought I'd wait for your input before I press the Checkout button.

The GR3149 (1.25 x .125 x 420 x 11 Non-Automatic) is recommended by http://cgi.julesborel.com/cgi-bin/matcgi2?ref=[cZDXJ\ and https://www.emmywatch.com/db/movement/eta--2804-2/

The GR2984 (1.20 x .125 x 380 x 11 Non-Automatic) is the closest I could find as specified by http://www.ranfft.de/cgi-bin/bidfun-db.cgi?10&ranfft&&2uswk&ETA_2804_2

The ETA2801770 (1.23 x .134 x 400 x 10.5 Non-Automatic) is recommend by Cousins https://www.cousinsuk.com/search?searchTerm=ETA2801770

Really confusing, and having to try to adjust the inner coil doesn't sound like much fun, at all 😬

I should have followed up sooner but better late than never I guess. So, I did order all of the above-mentioned mainsprings and the only one that would fit without any modification to the inner coil was the spring recommended by CousinsUK (ETA2801770). Plus it performs nothing short of perfectly. Mind you that my version of the movement is the 2804-2, so there is no guarantee it would work as well for other versions of the 2804.

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