Topspin Lubricant
Here is an interesting scientific article on the effects of lubricants on ball spin.
Tennis Top Spin Comparison between New, Used and Lubricated
Used Strings by High Speed Video Analysis with Impact Simulation
Yoshihiko KAWAZOE* and Kenji OKIMOTO**
* Department of Mechanical Engineering, Saitama Institute of Technology, Saitama
** Sanai Ltd., Hiroshima
This paper made clear the mechanism of actual top spin and its improvement by lubrication of
used and notched strings at the intersections using 10,000frames/sec high-speed video analysis.
Contrary to the hypothetical conventional spin theory, as the main (longitudinal) strings stretch and
slide side ways more and they spring back by lubrication of notched strings, the
ball is given more spin when the ball is released from the strings. The notches at string
intersections reduce the spin rate of the ball. More spin produce longer contact time between ball
and strings, resulting in the reduction of shock vibrations of the wrist joint during impact according
to the impact simulation based on the experimental identification of racket-arm system.
Furthermore, it showed that the spin rate of a newly strung racket without notch is much larger
than that of a racket with lubricated used strings.
The lubricant materials are most effective to the notched used strings.
1. INTRODUCTION
The terms used in describing the performance of a tennis racket are still based on the feel or
perception of an experienced tester or a player even today.
The restitution characteristics between a ball and racket as well as the shock vibrations at the wrist
joint can be calculated for a simple forehand swing model at any given swing speed and at any
impact location on the string plane if the ball strikes the strings at normal incidence 1)-16).
However, the ball spin is the mystery. Very little is known about the relationship between the ball
spin and the string characteristics both for researchers and players.
Players often say that some strings provide a better grip and more spin than others, but ball spin
did not depend on string tension, gauge or type and the scatter of data was larger than the differ-
ence of strings in the past laboratory experiment for oblique impacts on a head-clamped racket or
a freely suspended racket. Even recent measurements made by several authors on rebound spin
17)-23) showed that there still be no significant difference in ball spin off natural and synthetic gut
strings, off thin and thick strings, off loose and tight strings, contrary to common belief.
There was no research work on the topspin to uncover what is really happening during actual ten-
nis impact owing to difficult experiment, although the topspin hitting is very popular among ama-
teur players in these days.
This paper will make clear the mechanism of actual top spin and its improvement by lubrication of
used notched strings at the intersections using 10,000 frames/sec high-speed video analysis. It
also
shows that more spin results in more reduction of shock vibrations of the wrist joint during impact
according to the impact simulation based on the experimental identification of racket-arm system.
Furthermore, it shows that the spin rate of newly strung racket without notch is much larger than
that of lubricated used racket.
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