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A tennis ball is the
bouncing ball designed for the game of tennis, and is also one of the main
components of the game. In the early days, a tennis ball was made of
leather, stuffed with the hair or wool. In the 18th century, ¾”
strips of wool were wound tightly around a nucleus, made by rolling number
of strips into a little ball, and then tied with strings in many directions
around the ball, and a white cloth covering was sewn around the ball. At
present, this type of ball has a cork core but is still used for the
original game of tennis, now called real tennis. In the 1870’s lawn tennis
was introduced, with the introduction of this new type of tennis, vulcanized
rubber was first used to manufacture the tennis balls.
The modern tennis ball has
two major parts, the inner core and the outer cloth covering. The inner
core is made up of two half-shell pieces of formed rubber joined together
with adhesive to form a single core. The outer cloth covering are two
dumbbell shaped pieces of cloth that are attached to the ball core by
adhesive to give the tennis ball a classic appearance. The tennis ball’s
cloth density and thickness is matched to the court type which the ball is
designed for.
Tennis balls are subdivided
into two categories:
● Pressurized balls
wherein the core is pressurized with air or nitrogen. This type of tennis
ball lose their pressure over time so as their playing properties.
● Non-pressurized
balls are made from thicker rubber core where the pressure within the core
is equal to its ambient pressure; hence the balls tend to hold their playing
characteristics for a longer period of time and only the cloth
deteriorates.
In 1999, the International
Tennis Federation (ITF) approved an experiment wherein two new types of
balls were used in tournaments. These types of tennis balls were designed
to have different performance characteristics, differing in their dynamic
and aerodynamic properties. With the introduction of these two types of
balls, type I and type III, tennis balls have now three types
available for play, type I, II and III. These ball types can either be
pressurized or pressureless classified through their measurement of diameter
and compression test, which measures the forward and return deformation of
the ball under an applied load. The type I balls are harder than the
traditional type II balls and are designed for slow pace courts such
as clay. The type III balls are larger in diameter by approximately
6-8%. This type of ball is slower through the air due to its increased drag
properties and have steeper rebound angle giving more time for the receiver
to collect the ball.
ITF regulation currently
restricts the color of the tennis ball to greenish yellow or white and the
seams must be stitchless. Strict limits have also been placed for the mass
and diameter for each type of tennis ball. A rebound test was introduced in
1925 to determine the ball’s static stiffness and coefficient of restitution
(COR), and has remained unchanged since.
Even
though the tennis ball is used primarily for the game of tennis, it can be
used as a safe substitute for other games as well where a solid ball is
necessary.
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