WatchTech - Like portable electronics...

Like portable electronics...

Oct 13, 2012,13:23 PM

Hi Ken,
Like portable electronics, with a watch you have two possiblities to extend the autonomy.
1) Increase the amount of power on-board.
2) Reduce the power consumtion.

Portable computers and cell phones have been living from the fact that the big semiconductor companies have started putting many power reducing strategies that the watch industry has been using for decades in quartz watches into use for these other consumer products.
Although the batteries have barely changed in the last 10 or 15 years the power used by the devices has plumited and either the functionality increased with the same autonomy or the autonomy increased.

In a mechanical watch the way to reduce the power consumed is either to decrease the oscillating frequency or decrease the iniertia of the balance wheel, i.e. make it smaller. Both of these actions will, however, have an impact on the accuracy of the timekeeper. But all the long autonomy watches that come to mind have relatively small balance wheels.

The power stored by a battery is proportional to its volume and depends on the materials used in its manufacture.
Exactly the same is the case for a mainspring as we have seen in WT101.1.
Using several barrels allows placing this volume in several packages that give more freedom in the movement design.
Having one big barrel probably reduces the amount of passive volume that is not filled with mainspring material in the barrels, but I doubt that it makes a real big difference.

There is much development going on toward finding better spring materials that will allow storing more energy in a smaller volume. The class of materials know as glassy metals comes to mind.
On the other hand I am not aware of any Swiss manufacturer today using any material other than Nivaflex for their mainsprings so these developements are still ongoing.

Don

Comments: view entire thread

WatchTech101.2 - Main Spring Curvature

By: DonCorson : October 4th, 2012-10:57

WatchTech101.2 - Main Spring Curvature It is always interesting to see the beautiful curve of a main spring when removed from the barrel. It looks like it was drawn by an artist looking for a beautiful organic form. But it is, as so often, not an eye with...

Clear and elegant.

By: mkvc : October 4th, 2012-21:09

Many thanks. I'm curious whether anyone has experimented with obtaining the same result by graduating the thickness of the spring or even changing materials along the length of the spring. Couldn't the outer coils be thicker than the inner ones?

My first thought...

By: BDLJ : October 4th, 2012-22:15

...on varying the thickness of the spring is the difficulty of cold rolling (I believe this is how they are formed) a thickness variation without altering the cross-section. And whether the difference in the section would mean the thin end would be more w...

Exactly..

By: DonCorson : October 5th, 2012-12:52

BDLJ I think you have called it just right. In the next article in the series we will visit a main spring factory and see how the springs are made. The raw material is round wire which is rolled rectangular. The cross sectional area of the wire must match...

Another excellent post, Don

By: BDLJ : October 4th, 2012-21:49

And a question. Given mainsprings are rather brittle, how close to the elastic limit does one design the acceptable curve angle?

A little patience....

By: DonCorson : October 5th, 2012-12:31

next post in the series we visit a main spring factory. But actually, the elastic limit is not where the spring breaks, it just deforms. So in manufacturing the initial form is made so it will go above the elastic limit, it deforms so that it is just at t...

Elastic vs Plastic

By: BDLJ : October 5th, 2012-22:00

Sorry, I should have phrased it better. So, the 'S' curvature of the spring is designed to [ideally] provide a consistent stress throughout the length of the spring once it is loaded in the barrel. This stress is close to the elasic limit. If that limit i...

Thank you Don.

By: SamEE : October 7th, 2012-09:14

I have been waiting for your posts, they are very informative. I love watches, but never known how they work. Now finally you have taken the time to try to teach us what makes our watches tick. I am starting to appreciate how much planning and engineering...

How would a movement serviced . . .

By: Dr No : October 7th, 2012-15:06

. . . with too thin (or weak) a mainspring be affected? Would the timing be slow? And, would the discrepancy be reflected in the read-out of a timing machine, or would it manifest only under long-term observation? Just got a chance now to thoroughly read ...

A too weak mainspring...

By: DonCorson : October 8th, 2012-11:51

We need to go back to WT101.1 to see. This is the relevent graph and below the formula Your watch with it's designed in mainspring will start up somewhere between 1 and 1.5 turns of the barrel, from this graph let's claim that the watch starts from about ...

Interesting...

By: KIH : October 11th, 2012-16:00

These days, brands are trying to extend the power reserve or maintain the power reserve while reducing the number of the barrels (Lange's Grand Lange 1 comes to mind, for example). Would you elaborate about such efforts - what is the key to such result (h...

Like portable electronics...

By: DonCorson : October 13th, 2012-13:23