8912 double barrel question (aka paging Archer ;)

HiBoost · Jan 7, 2022

There were a series of interesting comments in this 2015 thread but my overall takeaway was that one barrel has a fixed spring and the other has a slipping spring to deal with the rotor's never-ending input. On my new SM300 if the rotor swings around to the right position I can see the toothed edges of both barrels. They are even labeled 😀 Given the description, I was expecting that if I hand wound the movement I would eventually see one of the two barrels stop turning while the other would continue to turn. The watch was already wound and running after a week of wearing but I did another 40 winds and both kept turning in unison. Do I have the wrong expectation/understanding, or did I simply not wind long enough?

I know hand winding is not necessary, I just thought this would be a neat visual indicator of full wind if in fact one barrel does stop turning at some point.

Deafcon · Jan 8, 2022

Both barrels wind and unwind together. Barrel 1 is where the input winding is and the fixed spring. Barrel two contains the slipping spring. The first wheel is driven off barrel 2 which then drives the rest of the train. In training it was explained like having two water jugs linked together at the bottom. If you pour water into jug 1, jug two will fill more or less at the same rate. The outlet is on jug 2, both jugs would empty more or less at the same rate.

View attachment 1348228 View attachment 1348230 View attachment 1348231

Deafcon · Jan 8, 2022

I made up a quick diagram. Hopefully this makes sense. Omega's main intent with double barrels was not to obtain longer run times. The design intent was to provide more consistent torque across the entire run time.

Archer · Jan 8, 2022

Yes, it's all pretty clear in that previous thread - one person wasn't getting it but it's actually very simple in practice.

Duckie · Jan 8, 2022

HiBoost
There were a series of interesting comments in this 2015 thread but my overall takeaway was that one barrel has a fixed spring and the other has a slipping spring to deal with the rotor's never-ending input. On my new SM300 if the rotor swings around to the right position I can see the toothed edges of both barrels. They are even labeled 😀 Given the description, I was expecting that if I hand wound the movement I would eventually see one of the two barrels stop turning while the other would continue to turn. The watch was already wound and running after a week of wearing but I did another 40 winds and both kept turning in unison. Do I have the wrong expectation/understanding, or did I simply not wind long enough?

I know hand winding is not necessary, I just thought this would be a neat visual indicator of full wind if in fact one barrel does stop turning at some point.

Use your observations to come to the most likely conclusion.

HiBoost · Jan 9, 2022

Deafcon

I made up a quick diagram. Hopefully this makes sense. Omega's main intent with double barrels was not to obtain longer run times. The design intent was to provide more consistent torque across the entire run time.

Ah, this helps a lot, thank you. So even though the spring in the first barrel is fixed and cannot "accept" any more winding, the outer visible barrel will still be spinning when the crown is turned (or presumably when the rotor spins) and this direct connection goes to the second barrel which in turn has the ability to slip internally. Is that correct?

hen · Jan 10, 2022

Thanks Defcon 👍

Deafcon · Jan 12, 2022

HiBoost
Ah, this helps a lot, thank you. So even though the spring in the first barrel is fixed and cannot "accept" any more winding, the outer visible barrel will still be spinning when the crown is turned (or presumably when the rotor spins) and this direct connection goes to the second barrel which in turn has the ability to slip internally. Is that correct?

Yes, that is correct.

8912 double barrel question (aka paging Archer ;)

HiBoost

Deafcon

Deafcon

Archer

Duckie

HiBoost

hen

Deafcon

Similar threads

Question about double barrells on Planet Ocean

8900 movement barrel question

Paradoxical rate increase over mainspring power reserve decrease; coaxial double barrel movement

Basic watchmaking tips - Oiling Part 2 (the mainspring barrel)