Abstract

Measuring the contact time between two objects during a collision can be difficult and when one object is a cloth covered rubber ball, and the other is a woven net of polymer material the task becomes even more complex. At HEAD Sport AG an experimental method was devised to accurately measure the contact time between a tennis ball and racket string-bed. The tennis ball and racket string-bed were carefully prepared for the measurement by applying a layer of carbon fibres to the ball and thin copper wires wrapped around adjacent main stings. An incomplete electronic circuit was set up using the copper wrapped around the strings, a voltage generator and measurement apparatus. The circuit was completed only during the brief time of impact, when the carbon fibres on the ball touched the copper wrapped strings completing the circuit. This paper describes the method and validation of the test protocol, and presents results from a series of tests involving the measurement of contact time for the new HEAD Flexpoint rackets. Verf.-Referat