ETA 2892A2 with GMT and Power Reserve Meter

[VWatchie]

For a long time now, I've wanted to try my hands on an ETA 2892. I even got myself a used Horotec oscillating weight bolt tool in preparation for it, in case I would need to replace the rotor bearing. Also, for a long time, I've wanted to try my hands on a movement with a power reserve meter. I have no idea about how a power reserve meter complication is implemented and have been trying to figure it out, but my ideas always ended up in a blind alley.

Anyway, I just spotted this watch on eBay housing an ETA 2892A2 having both a power reserve meter and a GMT complication for what seems to be a reasonable price. However, I'm sort of worried that I might mess up or won't be able to handle the power reserve meter complication as I have zero knowledge about how it works.

So far I've successfully overhauled quite a few watches but the most advanced complication so far has just been day and date calendars and no chronograph. So any advice or info about power reserve meter complications would be very much appreciated!

[Kalanag]

46 minutes ago, VWatchie said:

…So any advice or info about power reserve meter complications would be very much appreciated!

In principle you need a gear train that is connected to the barrel wheel as well as to the ratchet wheel. Turning the ratchet wheel lets the indicator hand move up and turning the barrel wheel lets it go down. What you want to be indicated is the „differential“ between ratchet and barrel rotations. Often a so called „differential gear“ does the job. It looks like a differential in a car drive train. But it‘s important to know that there are several very different setups for this differential function.

https://loupiosity.com/2013/12/uncomplicate-complications-power-reserve/

[VWatchie]

37 minutes ago, Kalanag said:

But it‘s important to know that there are several very different setups for this differential function.

https://loupiosity.com/2013/12/uncomplicate-complications-power-reserve/

Interesting! So, in the article that you link to, two different systems are explained, the "Differential gear" and the "Differential screw" systems. It would be really interesting to know what system would be found in the ETA 2892A2 that I linked to in my previous post.

I believe the GMT and Power Reserve indicator complications have been added to the movement by someone else than ETA as I couldn't find any documents for this movement having these complications on ETA's website!? This document is the closest I got: https://shopb2b.eta.ch/technicaldocuments/index/pdf/id/1621/ but it only has hours, minutes, central second, and date.

[Kalanag]

It‘s most likely a modul from Duboit-Depraz or Soprod. There seems no documentation available.

Edited June 6, 2022 by Kalanag

[Kalanag]

This should be the caliber in your watch: Soprod 9035

The differential function seems to be realised by a planetary gear set which keeps the construction flat.

Edited June 7, 2022 by Kalanag