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decksurgeon
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Straumann Double Hairspring Explained

been diggin up on the word "Straumann" and found that they are a global medial implant company!
in the dental implant website with the press releases they also have an association with H Moser.
One chap basically sits on the same board of both companies, how interesting.....

sorry to digress, but it was an interesting find thanks to google.
back to the double hairspring.......

The double hairspring basically prevents excessive forces on the center of the Arbor.

(1) FLAT CURVE HAIRSPRING:
In its most simple form of hairspring terminal curves is a flat curve and makes room for the hairspring stud.
While oscillating, the center of gravity is not remaining in the center, but is moving to and fro as the spring does not "breathe" concentrically about the center of the balance arbor/balance stuff.


so Breguet came along.........

(2) "BREGUET" OVERCOIL HAIRSPRING
Actually this is a description of hundreds of many different overcoil configurations described in watchmaking books.
There are other curves like the Grossmann curve with a special curve round the center of the collet. This allowed for compensation for the error which is called the Grossmann effect (it has to do with center of gravity in vertical positions of the watch and is complex).

Perhaps he best known of which are the Lossier curve and the Phillips curve. A Phillips curve has a characteristic "flat" spot while the Lossier curve is fully radiused and so on et cetera. What this overcoil attempts to achieve is to allow the hairspring to "breathe" more concentrically around its mounting axis. This still has some slight variation in the center of gravity & forces acting on the arbor/balance staff.


Then Straumann came along.......

(3) STRAUMANN DOUBLE HAIRPSPRING
What Straumann have done is to take two such "breguet" overcoil hairsprings and mount them on the same balance wheel in an opposing fashion.
This gives opposing symmetrical paths during oscillation and therefore any cumulative effects of forces are cancelled out. The resultant forces on the center of the arbor/balance staff remain constant and this has much less / no negative effects on the timing of the watch.




GRAPH SHOWING CENTER OF GRAVITY WITH DIFFERENT HAIRSPRINGS USING DIFFERENT TERMINAL CURVES
The trident like symbol shows the amplitude rotation of the hairspring, positive and negative denote the clockwise and counterclockwise rotation.
The resultant forces on the central arbor are then measured and plotted on a graph to show the deflection and forces along the X & Y axes.


The Straumann hair spring is made from Nivarox CT (PE 3000).
Nivarox was invented by Prof. Reinhard Straumann.
And the Straumann dental implant and H Moser hairspring companies now have the decendent of Prof Straumann sitting on the management boards.

How very interesting indeed when things go full circle (excuse the pun).......just like im told JLC make micro screws for another dental company.

and further google searching revealed the press release posted on this website:
click here