Last updated 3 weeks ago
Good day PingSkills. When the celluloid ball was used, the rule was the ball shall bounce up 24–26 cm (9.4–10.2 in) when dropped from a height of 30.5 cm (12.0 in). Since the change to the plastic ball, has the rule changed? I'm asking, because I'm noticing a big difference in bounce for the DHS plastic balls compared to the other plastic balls like the Xushaofa plastic ball.
This is the directive now.
Bounce is measured by releasing the ball mechanically without spin. After its bounce on a standard steel plate the ball is monitored with a digital camera with a calibrated mm scale in the background. The photos are evaluated. The geometric mean of three determinations then permits calculation of the maximum height of bounce of the “south pole” of the ball. A standard steel plate is made of Steel S235 with a surface roughness of Ra <= 1.0 μm and Rmax <= 7.5 μm. The size is no smaller than 20mm thick and 200 x 200 mm large.
B.7 Bounce Conformity
All 24 balls must rebound to a height of not less than 240mm and not more than 260mm when dropped from a height of 305mm on to a standard steel block.
For non-celluloid balls all 24 balls must rebound to a height of not less than 240mm and not more than 265mm when dropped from a height of 305mm to a standard steel block.
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