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Tennis ball machines have come a long way from the mechanical, hand-cranked versions first popularized in the 1920s.
Today, these machines can give you shots with different locations and heights, can vary speed, and can even add topspin or backspin.
But have you ever wondered, how do tennis ball machines work?
In this article we’ll give you the breakdown of the engineering that goes into making these deceptively complex machines.
Types of tennis ball machines
The original Lacoste machine shown in the video above was made using spring-loaded hammers to strike the balls.
As the crank is turned, flexible metal rods pass under a stopper that causes the rod to bend back under tension, and then to spring forward with force into the ball and shoot it forwards.
Spring-powered systems however are relatively uncommon today, found in only the most basic models, such as this machine by Tennis Twist.
The majority of commercial machines operate instead using one of two systems: pressurized air or rotating wheels.
This type of tennis ball machine was popularized in the 1970s by the company Prince, whose machines used vacuum motors to build up air pressure in the nozzle in order to launch balls at a constant speed.
These were the first tennis ball machines to gain widespread popularity in the sport.
Today, this type of system can still be found in some of the more entry-level machines, but these machines can be less consistent, especially across different types of balls, and as a result a large part of the industry has shifted to a different method of propulsion.
With this model, a machine feeds balls one by one in between two spinning, motorized wheels, which launch the ball out of the nozzle.
If you’ve ever been to a batting cage, the system is more or less the same.
Some benefits of this system are that the balls can be given spin by adjusting the speed of the wheels (topspin, for example, if the top wheel spins faster than the bottom), that the wheels can fire most models of tennis balls consistently at a variety of speeds, and that in general this technology is less noisy than air-powered machines.
One disadvantage, however, is that the friction caused by the spinning wheels wears out balls more quickly than systems using air pressure.
But many of today’s tennis ball machines do much more than simply spit out balls.
It is common for machines to offer features that vary frequency of shots, speed, height, and direction.
In fact, some machines even fake shots to simulate real gameplay, turning the nozzle in one direction before turning back and firing in the other.
All of these features are governed by a computer panel on the machine, which is responsible for controlling the speed of the motorized wheels, the feed rate of balls into the wheels, and the aim and direction of the nozzle.
These computers can be programmed to work specific routines, alternating forehand and backhand for instance, or can be randomized to work your mind as well as your body.
Building your own
On Youtube you can find several versions of homemade tennis ball machines which vary in complexity and functionality.
In this video, the designers have taken the most basic function of the machine, attaching two battery-operated motors to two rotating wheels in order to generate speed.
However, the machine must be held at the correct angle, and balls must be fed by hand, which is both impractical and potentially dangerous.
In this machine by tennis guru, however, the elevation is determined by hydraulic cylinders that adjust the angle of the machine, and the side-to-side oscillation is powered by another small motor connected to a hinge.
The speed of the shot can be adjusted by increasing or decreasing the power given to the main motor which are responsible for spinning the wheels.
High-end commercial machines use essentially the same technology, although they may include a more powerful motor for greater shot speed and more sophisticated controls, which allow many of the functions to be programmable and remotely adjustable.
How do tennis ball machines work?
So to sum up, almost all tennis ball machines use either spring-loaded hammers that strike the balls, pressurized air that builds up behind the ball and causes it to shoot out of a tube, or rotating wheels that grab onto the ball and propel it out of the tube.
In recent years, the addition of computerized technology has allowed tennis ball machines to perform a wide range of functions without the need for the player to manually adjust the machine.
Many machines can automatically adjust height, speed, positioning, and spin, and can even be programmed to perform these functions in set patterns or in random sequences to increase the training benefit.
So now that you know how your tennis ball machine works, it’s time to get out there and use it!
Featured image credit: DepositPhotos.com