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After winding my 6R15A fully, I set it down face up, and it ran for 55 hours and 24 minutes! Is this typical for this movement? Do the 7S26Bs run this long?


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Myles
 

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I have had two 6306 and several 6309 have over a 50 hour power reserve.
7s26 I had one run something like 48 hours...
 

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Selym said:
After winding my 6R15A fully, I set it down face up, and it ran for 55 hours and 24 minutes! Is this typical for this movement? Do the 7S26Bs run this long?


Best,
Myles
Experience tells me the 7s26B has the same main spring as the 7s26A with the resulting same PR.

The new 4r15(based heavily on the 7s26) has an advertised PR of 50+ hours; so it is reasonable to assume it has the same main spring as the 6515. This spring with it's longer reserve is probably partly responsible for the better precision reported for these calibers as opposed to the 7sxx :)
 

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Yes, 50+ hours power reserve is typical for the 4R and 6R caliber family because they both use Seiko's Spron 510 mainspring material. Seiko-Epson developed this metal material completely in-house and its key benefits are increased power reserve and better accuracy thus preventing too drastic gain/loss of time when the main spring is winding down.


SEIKO developed a new high-elasticity alloy "Spron 510" for the mainspring.
SPRON 510[sup]*[/sup] is SEIKO's unique alloy and leads the industry and delivers extended power and accuracy.
*SPRON is a registered trademark of Seiko Instruments Inc.

Spron 510 is also used in Seiko's Spring Drive movements and Spron 610 was just released for the new Grand Seiko 9S automatic watches with 72 hour power reserve.


The 7S family does not benefit from Spron technology.
 

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Pin said:
Experience tells me the 7s26B has the same main spring as the 7s26A with the resulting same PR.

The new 4r15(based heavily on the 7s26) has an advertised PR of 50+ hours; so it is reasonable to assume it has the same main spring as the 6515. This spring with it's longer reserve is probably partly responsible for the better precision reported for these calibers as opposed to the 7sxx :)

Indeed, see my last response. The 4r15/4r16, 6r15, 6r20, 6r21, 6r24, etc, etc all use Spron 510 mainspring material.


The 7s26/36 does not benefit from it.
 

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minidriver said:
Indeed, see my last response. The 4r15/4r16, 6r15, 6r20, 6r21, 6r24, etc, etc all use Spron 510 mainspring material.


The 7s26/36 does not benefit from it.
Makes me wonder what the Chinese were using in the mid 70s for some of their near chronometer grade movements with 50+ hour reserve?
Mind you they are hand winders but I don't seem to remember any of the Seiko hand winders from the era with such long reserves.

I'm sure some astute watchmakers will be able to explain it though ;)
 

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Pin said:
Makes me wonder what the Chinese were using in the mid 70s for some of their near chronometer grade movements with 50+ hour reserve?
Mind you they are hand winders but I don't seem to remember any of the Seiko hand winders from the era with such long reserves.

I'm sure some astute watchmakers will be able to explain it though ;)
I think they just wound 'em tighter, Peter... :)


Actually I was just wondering how those very expensive Swiss watches manage to get 7 day and greater power reserve.
 

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^-^ I'll have to bow to your experience Pete, but the part #'s are definitely different between 7s26a & b movements- whether it is a different spring material or a superceded part # , I don't know for sure. I had surmised that the 7s26b mainspring was possibly spron 100 and not 510- which would explain a not so great improvement in PR. The 6r15b as one of it's upgrades over the "a" movement now has the 6r20b's mainspring/barrel (spron510). As the 6r15b mainspring is a different part # to the 6r20a movement -maybe the 6r20a also used the spron100 mainspring and was upgraded in the "b" incarnation??. The 6r20a is quoted as having "more than 45hrs reserve" whilst the 6r15b is quoted as "more than 50hrs reserve" . The 6r15a and 6r20b tech pdfs are (it seems) unfortunately not easily available . Part #'s for mainspring /barrel 7s26a 0201-024 ,7s26b 0201-075 , 6r15b 0201-267, 6r20a 0201-074 (notice that the 7s26b and 6r20a part #'s are only one number different) . Cheers, Dave.
 
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