Increasing the Power Reserve (Question for a Watchmaker)

knightindustries

Considering the following examples:

  • Tissot PRX Chronograph, driven by an ETA A05.H31: ~60 hours power reserve, based on the ETA 7753: 42 hours
  • Tissot PRX Powermatic 80 driven by an ETA C07.111: 80 hours power reserve, based on the ETA 2824-2: 42 hours

How is it technically possible for the power reserve to be almost doubled compared to the base movement? Why is it not included in the base movement by default? Does it imply any drawbacks?

Maybe Tissot is using a longer main spring? I guess it would need to be thinner in oder to fit into the same barrel, but is therefore maybe more prone of breaking?

Or is it made of a different material, which would make it too expensive to be included in the base movement?

#tissot #prx #movements #deeptech #powerreserve
Reply
thekris
·

It’s surprisingly difficult to find information on how companies improve power reserve. Everybody wants to tell you about mainsprings or explain the concept of an automatic watch, but thats It. 
 

I was able to find out that the powermagic 80 uses “…a new construction concept that integrates a new spring barrel…”. So there you have it!  Just kidding, that didn’t tell us much. 
 

All I can come up with is that companies tweak the mechanicals to try to achieve greater reserves. This could be by using different materials, better lubricants or needing less lubricant or things of that nature. I would think that reducing the number of moving parts and/or reducing their weight would help. Basically, anything that improves efficiency should help in this regard. Or course, a bigger or second mainspring could help, but then you start adding bulk and I think that’s generally frowned upon. 

OldSnafu
·

They can lower the beat rate to get more reserve or add another barrel. With the powermatic 80 they dropped the beat rate from 28k to 21k and improved the barrel.

knightindustries
·
OldSnafu

They can lower the beat rate to get more reserve or add another barrel. With the powermatic 80 they dropped the beat rate from 28k to 21k and improved the barrel.

The reduced beat rate is a good explanation for the 80 hours.

But the 60 hours is also a vast improvement and I doubt the 7750 spares room for an extra barrel.

And what does it mean they "improved the barrel"? It's just a case for the main spring so what is it about the barrel that could make a difference? It has to fit in the same base movement so they cannot just make it bigger.

OldSnafu
·

They could have raised the barrel diameter a couple millimeters for another couple coils or thicker for stronger coils. They tweaked them enough for it to be named different from original versions but using most of the previous versions parts for cost.