Tennis Umpire Must-Read

Author: Tao Zhixiang / et al.
Editor-in-Chief: Xie Zhenjie
Publisher:
Publish Date: 1998-08-01
Features:
Excerpt:
(II) The Ball
1. Players use the ball to wipe sweat from their forehead or arms, making the ball wet. Is this allowed?
Answer: Not allowed. Players should be advised not to engage in actions that substantially alter the ball's shape or condition. If they persist, a penalty according to the Level 3 Penalty Table should be imposed.
2. How are the ball's elasticity, diameter, and deformation tests conducted?
Answer: The test regulations are as follows:
(1) Except as otherwise specified, tennis ball tests should be conducted under conditions of approximately 20 degrees Celsius (68 degrees Fahrenheit) and a relative humidity of about 60%. The balls should be removed from their containers 24 hours before testing and placed in an environment with the required temperature and humidity.
(2) The tests should be conducted under conditions of a barometric pressure reading of approximately 76 cm (30 inches) of mercury.
(3) If the average temperature, humidity, or barometric pressure at the venue differs significantly from the specified conditions, localized test standards may be used. These adjusted standards can be requested by any national tennis association from the International Tennis Federation (ITF). If approved, they shall apply to that region.
(4) All tests related to the ball's diameter should use a metal caliper with consistent thickness of 0.32 cm. The caliper should have two circular holes with diameters of 6.54 cm and 6.68 cm, respectively. The inner surface of the caliper should have a convex side with a radius of 0.16 cm. The ball should not fall through the smaller circular hole under its own weight but should fall through the larger circular hole under its own weight.
(5) The tests for the ball's deformation are as follows:
① Pre-compression: Before testing, any ball should be continuously and stably compressed by about 2.54 cm along three mutually perpendicular diameters. This operation should be performed three times (a total of nine pre-compressions). All tests should be completed within two hours after pre-compression.
② Elasticity test.
③ Diameter test.
④ Weight test.
⑤ Deformation test: Place the ball on an improved Stevens machine, ensuring that the ball's seams do not contact either of the two pressure rods. Add a contact weight to align the pointer with the reference line and set the scale to zero. Place an 8.165 kg test weight on the beam, and rotate the wheel at a uniform speed to apply pressure. The beam should remain 5 seconds away from its original position before returning to level. After stopping the rotation, record the reading. Then, rotate the wheel to the 10-mark on the scale. Reverse the pressure wheel at a uniform speed until the beam pointer aligns with the reference line again, and record the reading. Repeat this procedure at two additional points on diameters perpendicular to the initial test point's diameter line.