Testing an automatic mainspring for slippage in a barrel

[saswatch88]

1 hour ago, nickelsilver said:

Haha weeelll in my experience low amplitude is rarely due to the mainspring. But you did have the wrong height and the thickness could have been off a bit too, just 0.005mm makes a big difference.

so maybe he should use the 1.1 then which was originally in there, assuming someone else didnt have their hands in it before.

Mike i cant find any parts list for that caliber or part numbers. citizen is not the best when it comes to this which is why i always preferred seiko which parts lists can be obtained for almost every caliber and even full service manuals can be downloaded offline....

some avenues to try would be the citizen seiko forum https://www.thewatchsite.com/ also speedtimerkollektion has various parts and movements for citizen.

[mikepilk]

1 hour ago, saswatch88 said:

so maybe he should use the 1.1 then which was originally in there, assuming someone else didnt have their hands in it before.

Mike i cant find any parts list for that caliber or part numbers. citizen is not the best when it comes to this which is why i always preferred seiko which parts lists can be obtained for almost every caliber and even full service manuals can be downloaded offline....

some avenues to try would be the citizen seiko forum https://www.thewatchsite.com/ also speedtimerkollektion has various parts and movements for citizen.

Thanks @saswatch88. Speedtimerkollektion have a barrel for a cal 5204 but it doesn't look in great shape.

There are new barrels on ebay, but I don't know the part number.

This is my first Citizen, and I find it annoying that it's so hard to find information and parts. 

I've got several Seiko's - I like that it's so easy and cheap to find spares

[VWatchie]

Well, this thread is pretty old by now, but I'm really curious to know if you got this sorted and how?

I'm having the very same problem right now; an ORIENT cal. 46E40. The movement in itself is working perfectly but I only get out about 23H of power reserve (specified to 40H). The barrel looks very similar to SEIKO's 7S26 movements. It could be the same but I'm not sure.

I used a new Generale Ressorts spring and Moebius 8217 on the barrel wall. Perhaps I over lubricated or under lubricated it, or perhaps Moebius 8217 was the wrong grease? The aluminium on the barrel wall looked intact so maybe I shouldn't (or should?) try with Moebius 8213? Perhaps "rub around the inside with rough emery paper" as suggested by @nickelsilver. Not sure where to start...

The measurements of the original mainspring:
0.95 x .115 x 370 x 10.55 Automatic (Height x Thickness x Length x Barrel Diameter)

The measurements of the replacement mainspring (Generale Ressorts GR2378X):
0.95 x .12 x 400 x 10.5 Automatic (Height x Thickness x Length x Barrel Diameter)

I should mention that the alloy of the original mainspring felt very soft to handle. The Generale Ressorts spring on the other hand feels very steely and stiff. For this reason I accidently magled the original spring while I was cleaning it by hand or perhaps while I was (very thinly) lubing it with Moebius 8200 (can't remember which). Anyway, that's why I had to replace the spring.

[mikepilk]

2 hours ago, VWatchie said:

Well, this thread is pretty old by now, but I'm really curious to know if you got this sorted and how?

I'm having the very same problem right now; an ORIENT cal. 46E40. The movement in itself is working perfectly but I only get out about 23H of power reserve (specified to 40H). The barrel looks very similar to SEIKO's 7S26 movements. It could be the same but I'm not sure.

I used a new Generale Ressorts spring and Moebius 8217 on the barrel wall. Perhaps I over lubricated or under lubricated it, or perhaps Moebius 8217 was the wrong grease? The aluminium on the barrel wall looked intact so maybe I shouldn't (or should?) try with Moebius 8213? Perhaps "rub around the inside with rough emery paper" as suggested by @nickelsilver. Not sure where to start...

The measurements of the original mainspring:
0.95 x .115 x 370 x 10.55 Automatic (Height x Thickness x Length x Barrel Diameter)

The measurements of the replacement mainspring (Generale Ressorts GR2378X):
0.95 x .12 x 400 x 10.5 Automatic (Height x Thickness x Length x Barrel Diameter)

I should mention that the alloy of the original mainspring felt very soft to handle. The Generale Ressorts spring on the other hand feels very steely and stiff. For this reason I accidently magled the original spring while I was cleaning it by hand or perhaps while I was (very thinly) lubing it with Moebius 8200 (can't remember which). Anyway, that's why I had to replace the spring.

Hi @VWatchie

From what I remember,  I roughened up the wall of the barrel with a bit of wet and dry paper, and used a strong braking grease - 8213.

I think the spring was performing OK in the end.

I never did get great amplitude. As @nickelsilver suggested, this probably isn't due to the mainspring, but as it just sits in my collection, I'm not bothered. I'll have another go at it one day. It's an unconventional gear train, and the most complicated movement I've worked on - talk about springs !

Don't assume that new springs are OK - I've had several instances when I've repeatedly stripped movements to try and figure out why the amplitude has been so low, and it turned out that the 'new' mainsprings were dud - i.e. not springy

Good luck

[VWatchie]

42 minutes ago, mikepilk said:

From what I remember,  I roughened up the wall of the barrel with a bit of wet and dry paper, and used a strong braking grease - 8213.

Thanks! So, that's what I'll try as well. In my case I have no problem with the amplitude as seen in this post. The only problem (that I'm aware of, you never know) is the low power reserve.

45 minutes ago, mikepilk said:

Don't assume that new springs are OK - I've had several instances when I've repeatedly stripped movements to try and figure out why the amplitude has been so low, and it turned out that the 'new' mainsprings were dud - i.e. not springy

I very much assumed that new and unused mainsprings were "top notch" so thanks for the heads up. Goes to show that you can never, never take anything for granted.

 

47 minutes ago, mikepilk said:

It's an unconventional gear train, and the most complicated movement I've worked on - talk about springs !

I saw some pictures of it (or a similar calibre) somewhere  I hate springs, especially when having to wait for spares! 

[VWatchie]

Inspired by @Nucejoe's method I will try to test the slippage of my mainspring like this: According to the specs the power reserve of my movement should be 40h. The number of leaves on the centre wheel pinion is 12. The number of teeth on the barrel is 84. For the centre wheel then to rotate 40 turns, 480 barrel teeth is required (12 leaves x 40 hours = 480). 480 / 84 equals approx. 5.7. That is, after about 5.7 turns of the ratchet wheel the mainspring should slip. If it slips sooner (which is the likely scenario) it won't yield the 40 hours and I will have to take some action.

Big question though; will it really be possible hear and/or feel when the mainspring slips? What's your experience?

 

Edited May 27, 2020 by VWatchie

[Nucejoe]

2 minutes ago, VWatchie said:

Inspired by @Nucejoe's method I will try to test the slippage of my mainspring like this: According to the specs the power reserve of my movement should be 40h. The number of leaves on the centre wheel pinion is 12. The number of teeth on the barrel is 84. For the centre wheel then to rotate 40 turns, 480 barrel teeth is required (12 leaves x 40 hours = 480). 480 / 84 equals approx. 5.7. That is, after about 5.7 turns of the ratchet wheel the mainspring should slip. If it slips sooner (which is the likely scenario) it won't yield the 40 hours and I will have to take some action.

Big question though; will it really be possible hear and/or feel when the mainspring slips? What's your experience?

 

You can't miss the sound, hold the piece close to ears as when you hear the ticking, mainspring slipage sound is much louder.

[VWatchie]

1 hour ago, Nucejoe said:

You can't miss the sound, hold the piece close to ears as when you hear the ticking, mainspring slipage sound is much louder.

That sounds reassuring. I’ll see if I get a chance to give it a try tomorrow and will report back. Thanks Nuce!

[spectre6000]

23 hours ago, VWatchie said:

In my case I have no problem with the amplitude as seen in this post. The only problem (that I'm aware of, you never know) is the low power reserve.

I may be out of my depth, and if so, someone within their depth please correct me.

If your amplitude is fine, but your reserve is low, assuming everything else is truly as it should be and you replaced the spring with one that feels different in the way you described, Hooke's law suggests the spring is wrong. F=KX. Since F seems to be working out in the short term, it seems like K (spring constant, stiffness of the spring) is fine if your amplitude is where it should be, but since you're sputtering out soon, X (displacement) seems low. Displacement per beat is regulated by the gear train, so X at that level is finite, and K is the only variable, but over the long term, you could likely reduce K to some degree while increasing X in turn. Your amplitude will decrease per beat, but you'll get more beats per fully wound spring.

[VWatchie]

1 hour ago, spectre6000 said:

I may be out of my depth, and if so, someone within their depth please correct me.

I have no idea but thanks for your input!

[spectre6000]

Don't think of it as math so much as relationships. F=KX is (F) Force equals (K) spring k/constant times (X) displacement. You're only really worried with how they relate to each other, not anything more precise. If you multiply numbers together, the result is bigger; if you divide them, the result is smaller. The end.

Force is exactly what you think it is. Displacement is a fancy word for distance. The spring k/constant is how stiff the spring is. For watchmakers, the important part here is that we can split apart the mainspring into component parts of stiffness (*) and distance (effective length; effective, because it's typically preferred that a spring is never fully wound or unwound for better isochronism).

* Stiffness in a mainspring is typically a function of its thickness, but if you have a really old coil mainspring vs a modern S spring, or an old school spring steel vs a modern alloy, or maybe the spring has set, these can all play a part.

The gear ratios in a gear train are fixed. For every release of the escapement, a certain degree of rotation of the mainspring barrel is unwound from the mainspring. That makes analysis even easier, because X is constant per beat. You simply get more X with a longer spring in the form of more beats.

Assuming everything else is in proper fettle, you have a finite amount of room in the mainspring barrel into which you can stuff a spring. That stuffing happens across the dimensions of length, and thickness; dimensions that correspond directly with X and K respectively. If it's too strong, the balance over banks, and you gotta problem. Additionally, but to a lesser degree, if your amplitude is higher than is required for isochronism, it's really not doing you any good, and is just a waste of spring. Too weak, and amplitude is low, and error creeps in (anisochronism). So you need a spring that is stiff enough to get you a good enough amplitude to ensure isochrony, but otherwise as long as you can to maximize power reserve.

If everything else is good, then you add a new mainspring which measures .007 thicker and feels harder (aka stiffer or higher K) and is .05 shorter (lower X), that's the precise recipe, according to Hooke's law, for a good amplitude but short power reserve. You made K larger, and X smaller, you just don't know the precise magnitude of each change... 

You can see through your amplitude that F is larger than would be expected for a given distance of mainspring travel since, per swing of the balance, X is fixed, that means K is higher than it should be. You can further see through the short power reserve that the overall X of the spring is shortened. 

312° is a really high amplitude; probably higher than just about any manufacturer requires for isochronistic reasons... On top of that, It sounds like Citizen kinda sucks for documentation, but they seem to be in the same school as Seiko who is good with documentation, and is known for preferring unusually low amplitudes while still achieving reasonable isochronism. Given that the point of a high amplitude is to mitigate anisochrony, they're going at the isochronism problem from a different angle (whatever that is, I don't know yet). I would shoot for a typical Seiko level amplitude, see how the power reserve comes out, then check isochronism against your preferred/available of spec or personal standard.

This has nothing to do with braking grease, internal barrel features, bridle wear, or anything else. Just the isolated variables as described. Also worth noting, this is how Roger Smith (George Daniels' protegé) chooses mainsprings for his highly esteemed movements according to... him in his own lectures**. Also also worth noting... I'm about as nooby a noob that ever noobed, so consider the entire manifesto above in that light.

Bottom line: Get a new mainspring that's thinner and longer. Since the alloy appears to be different, you may go more than a single step thinner, and see how long you can go and still functionally fit in the barrel. This, again, is inferred from the Roger Smith lecture, and he specifically states that he has a huge assortment of mainsprings at his disposal**, so YMMV.

**I think this is the lecture, but it's not exactly the key focus, and was really just a side note at some point... I don't remember where in the hour and change it came up or why, I'm just one of those people who remembers trivial details like that...

 

Edited May 28, 2020 by spectre6000

[VWatchie]

On 5/28/2020 at 3:55 AM, spectre6000 said:

Don't think of it as math so much as relationships.

Respect!  That must have taken you a while to compose!

Right or wrong, I just look at it like this; I have too little friction between the barrel wall and the bridle. Now waiting for some Moebius 8213 Strong Braking. In the meantime, I have sanded down the barrel wall to expose the brass and make it slightly rougher.

Doing some testing before removing the mainspring I noted 4.5 complete revolutions of the ratchet wheel before the spring slipped. I was expecting a very short and snappy slipping sound but instead it was a slithering sound that lasted for a little less than half a second. That, to me, indicates that the bridle was having problems attaching itself to the barrel wall again.

Anyway, once I get the new grease I'll let you know the result.