PURPOSE: To evaluate a ball in its symmetrization by detecting a signal of rotation of the respective balls by a torque detector while calculating the signal of rotation by an arithmetic processor and a resistance value of rotation and comparing a difference between the resistance values of rotation in a seam direction and a ball direction with a preset reference value.
CONSTITUTION: A golf ball 1a is arranged in vessel 10 filled with liquid W, and rotating the golf ball 1a, arranged in the before described liquid W, by a variable control motor 5 in a fixed speed (4,000rpm), a resistance value of rotation (torque) of the golf ball 1a is detected by a torque detector 2 and an arithmetic processor 6. The detected resistance value of rotation of golf balls 1a, 1b is printed out by a printer 7. When a difference between the resis tance values of rotation of the golf balls 1a, 1b is smaller than the preset refer ence value, the golf ball 1 is evaluated generating no difference on a flying quality by the ball hitting position, and the golf ball is decided to be in good symmetrization. When the difference between the resistance values of rotation is larger than the preset value, the golf ball is evaluated having bad symmetriza tion.
NINOMIYA TOSHIRO
NIWANO YOSHIAKI
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