Rules

Appendix I

Regulations for Making Tests Specified in Rule 3.

1. Unless otherwise specified all tests shall be made at a temperature of approximately 68° Fahrenheit (20° Centigrade) and a relative humidity of approximately 60 percent. All balls should be removed from their container and kept at the recognized temperature and humidity for 24 hours prior to testing, and shall be at that temperature and humidity when the test is commenced.

2. Unless otherwise specified the limits are for a test conducted in an atmospheric pressure resulting in a barometric reading of approximately 30 inches (76cm.).

3. Other standards may be fixed for localities where the average temperature, humidity or average barometric pressure at which the game is being played differ materially from 68° Fahrenheit (20° Centigrade), 60 per cent and 30 inches (76cm.) respectively.
   Applications for such adjusted standards may be made by any National Association to the International Tennis Federation and if approved shall be adopted for such localities.

4. In all tests for diameter a ring gauge shall be used consisting of a metal plate, preferably non-corrosive, of a uniform thickness of one-eighth of an inch (.318cm.) in which there are two circular openings 2.575 inches (6.541cm.) and 2.700 inches (6.858cm.) in diameter respectively. The inner surface of the gauge shall have a convex profile with a radius of one-sixteenth of an inch (.159cm.). The ball shall not drop through the smaller opening by its own weight and shall drop through the larger opening by its own weight.

5. In all tests for deformation under Rule 3, the machine designed by Percy Herbert Stevens and patented in Great Britain under Patent No. 230250, together with the subsequent additions and improvements thereto, including the modifications required to take return deformations, shall be employed. Other machines may be specified to give equivalent readings to the Stevens machine and these may be used for testing ball deformation where such machines have been given approval by the International Tennis Federation.

6. Procedure for carrying out tests:

   1. Pre-compression. Before any ball is tested it shall be steadily compressed by approximately one inch (2.54cm.) on each of three diameters at right angles to one another in succession; this process to be carried out three times (nine compressions in all). All tests to be completed within two hours of pre-compression.

   2. Bound test (as in Rule 3). Measurements are to be taken from the concrete base to the bottom of the ball.

   3. Size test (as in paragraph (iv) above).

   4. Weight test (as in Rule 3).

   5. Deformation test. The ball is placed in position on the modified Stevens machine so that neither platen of the machine is in contact with the cover seam. The contact weight is applied, the pointer and the mark brought level, and the dials set to zero. The test weight equivalent to 18 lb. (8.165kg.) is placed on the beam and pressure applied by turning the wheel at a uniform speed so that five seconds elapse from the instant the beam leaves its seat until the pointer is brought level with the mark. When turning ceases the reading is recorded (forward deformation). The wheel is turned again until figure ten is reached on the scale (one inch (2.54 cm.) deformation). The wheel is then rotated in the opposite direction at a uniform speed (thus releasing pressure) until the beam pointer again coincides with the mark. After waiting ten seconds the pointer is adjusted to the mark if necessary. The reading is then recorded (return deformation). This procedure is repeated on each ball across the two diameters at right angles to the initial position and to each other.