Grand Seiko Dual Impulse Escapement

[Tudor]

This, is beautiful...

 

[Nucejoe]

Unlike co-axial, only one escape wheel, dose the idea differ?

[Tudor]

I don’t have any more details. 

I’m guessing it would use two escape wheels based on this illustration. 

[Marc]

1 hour ago, Tudor said:

I’m guessing it would use two escape wheels

Only the one.

If you google Seiko Calibre 9SA5 there's a fair bit of interesting stuff out there.

or...

 

[Tudor]

That's cool.

Looks like 450 degrees of balance wheel rotation, at high beat! Crazy! I was not expecting more than a full rotation, but that probably adds to the timing accuracy.

 

[spectre6000]

Definitely different from the coaxial escapement. One of the big issues Daniels had with getting the coaxial ready for mass production was alignment of the two escape wheels (Smith, his protege, addressed this by making a more three dimensional wheel that is indexed during manufacture). This solves that, making it easier to mass produce. It reintroduces some sliding friction though, as the last jewel on the escape pallet is a fairly conventional geometry with a Swiss lever-like impulse face. Not only is that sliding friction itself a bit of a compromise, but the lubrication requirements also reduce the service interval compared to a coaxial, whose oil usage (at least on paper) is mostly for oxidation protection. The low tooth count on the escape wheel is interesting. With 8 teeth at 36000bpm, it's turning pretty fast. I count a total of 5 wheels between the second mainspring barrel and the escape wheel to make that reduction work. The losses added by those two extra wheels aren't super exciting. I'm not sure how the extra amplitude plays out; I've not read too deep on that subject. As I recall, additional amplitude reduces error, but only to a point. I'm not confident enough in that recollection to say anything definitive though.

 

The coaxial escapement eliminated a significant percentage of the Swiss lever's sliding friction losses, did not require any additional wheels and their requisite frictional losses, and managed to dramatically increase the service interval in the process. This dual impulse escapement cuts the sliding friction nearly in half compared to the Swiss lever, but adds back an appreciable percentage of it through the two additional wheels. Further, I wouldn't go so far as to say it doesn't increase the service interval at all, but it wouldn't likely do so by much. The coaxial is a definite improvement, where I feel this is more likely just novel. The asterisk is the amplitude (at least as presented in that animation); maybe a meaningful improvement, maybe not, maybe just an animator who didn't know better. 

[clockboy]

I am very impressed with these Grand Seiko's however no parts are available if one lands on your workbench. I had to replace a shock spring on a Rotary watch that was fitted with a Seiko movement but no shock springs are available so I had to modify a shock spring I had in my stock.

[Tudor]

Unfortunately, there's no "free lunch".

But, I have always admired the Seiko and Zenith high-beat movements. I think they're fantastic, and I aspire to own a high-beat El Primero some day...

 

I have a plan to coat a conventional 2824 escape wheel with DLC (diamond-like carbon) which is very slick and of course very hard. This may allow the stones to be run dry, which should free up some losses to oil sticktion on the stones. Of course the escape wheel may then cut into the stones.

I can also have the going train wheels and pinions coated (perhaps pivots too) but I'm not sure of the implications. This (pivot) change may require sapphire bearings rather than ruby. Not sure. But, it too may allow it to be run completely dry, which would not only reduce the drag, but allow a much wider operational range (much lower-arctic and/or space service) without special oils. Maybe.

I don't know enough about the micro-mechanics so I want to base it on a well-known movement with tons of empirical data available. That old 2824 seems like a good choice (although I prefer the 2892-A2). Plus there is the very real possibility of parts loss or damage in the coating process, so something with an easy parts supply also makes sense for this. Maybe a cheap 2824 clone movement would be an even better choice, as I can buy three for the price of one ETA.

Thinking...

[Nucejoe]

6 hours ago, Tudor said:

I don’t have any more details. 

I’m guessing it would use two escape wheels based on this illustration. 

Smart design, takes two impulse out of one wheel and three pallets or are there four? Again much like co- axial little run on escape teeth.

 

[jdm]

3 hours ago, clockboy said:

I am very impressed with these Grand Seiko's however no parts are available if one lands on your workbench.

Which being honest is very unlikely. Just some Swiss watch owners, Grand Seiko owners actually appreciate the exclusiveness of having their watch sent to the factory for service or repair. 

Quote

I had to replace a shock spring on a Rotary watch that was fitted with a Seiko movement but no shock springs are available so I had to modify a shock spring I had in my stock.

Strange because 7S26, 4R15, 6R15, NH36, NE15 etc shock springs are easily available from Cousins.

[clockboy]

4 minutes ago, jdm said:

Which being honest is very unlikely. Just some Swiss watch owners, Grand Seiko owners actually appreciate the exclusiveness of having their watch sent to the factory for service or repair. 

Strange because 7S26, 4R15, 6R15, NH36, NE15 etc shock springs are easily available from Cousins.

That is correct but the latest Seiko calibers have unique shock springs. They look like standard shock springs until fitting as they slightly different in size. I did put up a post a while ago with this issue.

[jdm]

8 minutes ago, clockboy said:

That is correct but the latest Seiko calibers have unique shock springs. They look like standard shock springs until fitting as they slightly different in size. I did put up a post a while ago with this issue.

Topic below? That is a Chinese movement, not a Seiko. For these, one could try the assortment that Cousins sells for the purpose.