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Shock Resistance

by Jordan Ficklin

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If you wear your watch it receives shocks (not the electrical kind). By shocks I mean it gets bumped around and makes sudden starts and stops. in fact this is what makes watches so different from clocks: They change position and they receive shocks. If they didn’t they would probably have pendulums in them instead of balance wheels and hairsprings.

There was a recent question on timezone about shock resistance and it inspired this post. There were some good answers.

WellsbroThere was a time when watch companies bragged about their watches being shock resistant, but today nearly every watch has some form of shock resistance so you don’t see it on the dial like you used to. This little Wellsbro says “Incabloc” on the dial.

When your watch receives a shock it affects timing because the sudden stop of the watch case transfers motion to the balance wheel. Imagine spinning a ball one direction on top of a surface moving the other direction, the motion will transfer and eventually the ball will be spining the same direction as the surface. Rotational shocks are the worst for timing, but probably the least common. Most shocks come from the side of the case or from the dial as we bang our wrist around on stuff.

Timing is one thing, but a bigger issue is things can break. Your watch experiences little car accidents all day long. In order to be “shock resistant” a swiss watch needs to be able to withstand a drop from one meter without the balance staff (or other components) breaking. This sudden impact supposedly generates about 5,000 G-forces of deceleration. I know from experience that a watch falling from a desk onto a carpet floor can cause the balance staff to break (if not shock protected.) I also know that a Rolex which falls on a tile floor causing the sapphire crystal to shatter usually escapes without damaging any of the pivots.

So, how does the shock system work? There is an excellent visual model on Incabloc’s web page which demonstrates the working principle behind shock absorbance. You should check it out and click on the arrows to simulate shocks. Click on [products] and then [shock absorbing function] to see the model. Basically the idea is to allow the staff to move so that a sturdy shoulder takes the blow instead of the tiny pivot. The jewel (with it’s oil) moves with the pivot and then is returned to it’s original position by a spring without displacing the lubricants or damaging the pivot. (Timing will still be affected, but nothing will break.) There is a great WOSTEP model for instruction which you can physically move and see the components do their job.

Without shock protection systems today’s clumsy (and sometimes careless) individuals would be making my job much more difficult (and in demand). It’s not a simple task to replace a balance staff!

Incabloc is just one of many similar systems for providing shock protection. There are other ways. Some companies have suspended their watches in oil, Caiso G-shock has only solid state components, and there are others.

Wyler BalanceThe Wyler company had another method for dealing with shock and that was to reduce the amount of force transfered to the pivot. They did this by supporting the rim of the balance wheel on curved flexible arms so that the mass of the wheel could continue moving without the staff.

Update:

Check out the video at alliancehorlogere.com if you want to see shock resistance in action.

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3 Trackbacks/Pingbacks

  1. [...] Original post here This entry was written by J.Peter and posted on May 2, 2008 at 8:19 pm and filed under watches, watchmaking. Bookmark the permalink. Follow any comments here with the RSS feed for this post. Post a comment or leave a trackback: Trackback URL. « Magnetism – Enemy of Isochronism [...]

  2. [...] talked about Shock Resistance before and highlighted a video as [...]

  3. [...] talked about shock protection before way back in 2008 and you may recognize this model as a very similar one appears in the video [...]

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