Getting a grip: load cells and tennis equipment testing
This year the Wimbledon grass has seen some serious action, as the world’s top tennis players battle it out for the coveted title (if not ranking points). Sadly, at time of writing, Britain’s Andy Murray and Emma Raducanu have both been knocked out of The Championships at Wimbledon, but Cameron Norrie is through to the third round.
In anticipation of another fab week of tennis at SW19, we look at the supporting role load cells have played in making tennis the fast-paced, all-action sport it is today.
Slip sliding away
Let’s start at the bottom, so to speak, with tennis shoes. It’s important that players maintain a good grip on the grass surface regardless of its conditions, be it wet grass or, often by the second week, a dusty strip behind the line.
Equally, grass is not the only surface, with tennis also played inside on acrylic courts, on clay courts, and outside hard courts at sports centres. A study in 2016 aimed to discover the optimal tread pattern for tennis shoe soles by creating tread patterns with different heights, spacing and spacing, and testing them on a traction rig.
“We performed experiments with different vertical loads and extracted both static and dynamic friction coefficients using force data supplied by load cells mounted vertically and horizontally. Variations in the compound’s tread geometry lead to different friction coefficients. We also rotated our tread patterns over a range of angles and extracted associated friction coefficients.”
Taking it to the net
A team from the University of Sheffield wanted to created a portable device that could “measure the tribological behaviour of shoe interactions with tennis courts”.
“The device consists of three main components: a sled, a pneumatic ram and a test shoe slider. Compact dimensions (800 × 400 × 150 mm) in use and an approximate weight of 10 kg without the applied weight, makes the device relatively light and portable.
“A test shoe slider is attached onto the sled … to replicate the desired shoe pressure. A solenoid valve (opens) the pneumatic cylinder providing a horizontal force to drive the sled. The horizontal force increases until sliding of the shoe test slider is initiated … A load cell and a LVDT in the horizontal direction provide the measurements necessary to define the friction provided.”
For more on tennis shoe traction studies see our other blog.
Good vibrations – not
Tennis racket design is crucial to any player’s success on court. A 2013 study aimed to “investigate design factors that contribute to reduced stress and improved vibrational dampening,”, again using load cells. The aim (pardon the pun!) was to compare ten different racket frame by repeated impacts to the centre of each racket:
- “Each racquet handle was secured to a load cell (maximum capacity of 5kN) via gripping plates such that the face of the racquet was perpendicular to the mounted handles. A 2.5lb (11N) weight was dropped at 18 inches (0.46m) with a mean acceleration of 24G’s onto the marked centre of each racket for five trials of impact.
- “The mounting of the racquets and design of the study minimized such variabilities due to the consistent nature of the test design. Each racquet handle was mounted and rigidly affixed to a calibrated load cell mounted to a materials test machine.”
String theory
Talking of strings, here’s a story from a previous blog on the Wimbledon Championship Tennis Tournament.
The world-famous Championships are a busy time for the in-house stringing team. They string on average over 2,000 racquets, using up to 40 miles of string. A championship-standard tennis racquet is a complex, lightweight mix of composite materials, capable of withstanding the impact of serving shots at 140mph. Load cells are used to test all aspects of string performance, including tensile strength, elongation, and knot strength. Load cells have also been used to examine the response of the string-bed on impact with the ball.
Looking for innovative ways to test sports equipment?
Call us to discuss your specific requirements. We have helped design bespoke load cell systems, and can manufacture to your exact criteria right here in Reading, Berkshire.
