Independents

theCROWNprince
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Doomed to Fail!

When I first became aware of this concept, I too thought this was a romantically great idea but the cost of such superficial attractiveness is that she is a money grubbing whack job. 

Adding meantime screws defeats the purpose of adjusting the length of the hairspring.

Adjusting the hairspring length between two rollers damages the structural integrity and basic performance of the hairspring.
Rolling makes the hairspring thinner, until it no longer rolls but fits loosely which is never a good thing. Rolling the hairspring thinner makes the tension in that portion of the hairspring change as well as the dynamic shape should the rollers not be perfectly aligned. As any good watchmaker knows, I am sure John can attest to it, the hairspring is everything when it comes to precision timing. Any manipulation can have serious consequences. The hairspring's job is to expand and contract in an even manner, nothing else. The simpler this can be accomplished the better. K.I.S.S.! As soon as you start asking it to perform other tasks you will have problems.  This is the same reason I don't have my barber work on my car or my mechanic cut my hair.

Adjusting the effective length of a hairspring as an easy short cut to more precise hairspring design is more safely accomplished by use of rollers that do not "roll"  the hairspring but we call those regulating pins. The standard regulating pins cause far less distortion of the metal of a hairspring than the roller method. The regulating pins however do still distort the hairspring material. I am no metalurgist, so someone may be able to explain better, but the elasticity of the material changes after a few million flexings agains a regulating pin. Much like bending a wire hanger is most difficult the first time but bending it repeatedly will cause catastrophic failure of the material. Regulating pins do not cause such sharp bends but none the less, today you see specialty treatments of the terminal bend to strengthen this area. This helps avoid a negative decline in rate from the softening of the hairspring at the regulating point. This doesn't address the design deficiencies of regulating pins in relation to the dynamic performance of a watch over its life span (change in amplitude) only the effects on the material of the hairspring itself. Another thing to note is the material used for the rollers or regulating pins. Rubber rollers would be better (might not fair well in standard cleaning solvents) as they would distort the hairspring less but still not a good idea. As for regulating pins, they are much like banking pins and are very dynamic. Both kinds of pins need to perform as a shock absorber and yet retain their position. This is why brass (or similar material) is best. Howard and Patek used ruby banking pins for the pallet fork, Rolex and others experimented with ruby regulating pins, all with disasterous results. Ruby regulating pins tend to "cut" the hairspring in two, ruby banking pins return too much of the impact force back to the pallet fork causing it to bounce against the safety roller, thus interferring with the timing and amplitude of the balance wheel. Sorry to get off topic...

 The reason free-sprung balance springs work so well is the lack of interference and or damage to the hairspring and its performance.  This roller design was a nice thought in history but so was the amphibious car and prescription meth for depressed house wives.


TCP