抄録
Strictly speaking, the torque of hairsprings is not linearly proportional to the angle of rotation of the balance wheel.
This arises from the fact that turning over.the hairspring, the small reaction force results at the outer fixed point besides the moment. In consequence of this non-linearity, the period of vibrations depends upon the amplitude of the balance wheel.
The author could measure this effect by using the optical experimental method which makes possible the extremely large magnification of time.
In this report, the results of preliminary experiments and a part of main experiments are described.
These are as follows :
i) The frictional resistance of the balance-staff dose not affect the measurement of the non-linearity of hairsprings.
ii) A little difference of the form of the outer terminal curve, which is deformed from Archimedes spiral in order to fix by the stud and curb-pins, does hardly affect the non-linearity.
iii) The effect of the strain, which is given to the hairspring in the radial direction at the curb-pins, is proportional to its amount.
iv) The effect of the direction of hairspring eccentricity, which is measured from the center of rotation to the geometrical center of spiral, is remarkable.
This effect was measured in 4 cases of the spiral angle, that is, 8 coils plus 270, 180, 90, 0 degrees from the pinning point to the curb-pins.
