The modern game of tennis is dominated by the amount of spin that players can impart to the ball. Creating more topspin allows players to hit the ball harder while still keeping the ball in control. Despite the importance of spin, until recently it was not well understood how spin is generated. A 10,000-frame-per-second high speed camera has shown that spin is generated by the slide and snap back movement of the main strings on the racket (see video).
SpinGen works by roughening the top surface of the main strings only where it is needed - where the string touches the tennis ball. The main strings can then grasp the tennis ball better. Underneath, the smoother inter-string surfaces allow strings to slide freely. This ensures that the main strings can slide and snap back efficiently for spin generation.
Today's commercial strings have a single surface, either smooth or rough, but not both. The SpinGen is designed to make ideal strings for spin generation by combining the advantages of smooth and rough surfaces.
The SpinGen can also be used to revive the spin strings when their top surfaces become smooth as shown in the 3 pictures below.
Left: Textured spin strings when new
Middle: After 2-3 hours of play, the top surface of the string becomes smooth in the racket sweet spot, and can no longer effectively generate spin.
Right: Use SpinGen to roughen the top surface of the main strings to regain the spin generation capability.
We conducted a simple rebound experiment to measure the increased spin capability. We shot batches of tennis balls at an angle to a mounted tennis racquet, before and after SpinGen was applied to the strings, and then we marked the locations where the balls landed (red spots are from the strings before SpinGen was applied, blue spots are from the strings after SpinGen was applied).
The balls consistently bounced off the SpinGen roughened string bed with more spin, which is why the balls curved more towards the center line perpendicular to the string bed.
The strings roughened withSpinGen grab the ball with increased friction and snap back with more power for spin generation. Our website has more information on this experiment and data analysis.
The SpinGen idea came about when Lu lost a tennis match using a newly strung racket with round, smooth strings coated with Teflon. Lu is an avid tennis player and noticed it was harder to generate spin with these smoother strings. As an engineer, Lu started to think of ways of roughening the strings for optimal spin, and decided to design a tool to make only the top surface of the strings rough, while leaving the rest of the string smooth for quick slide and snap back action.
Risks and challenges
Some risks and challenges might come our way when we start our first large-scale production of SpinGen. We are constantly working hard to mitigate any risks might arise during production.
We have machine shops and injection molding manufacturing partners that specialize in tooling and manufacturing. We have finalized our mold design with an experienced product design team, we have everything in place for full production.
Once all the parts are manufactured and pass QC checks, they will be shipped to our facility for assembly and packaging.
In all matters, we will keep lines of communication with our backers open, and update you about any developments. We expect to receive our products in Boston for packaging and distribution 8-12 weeks after successful funding.
We expect to have pre-production samples for final optimization of the manufacturing processes used for finishing the SpinGen. This finishing involves assembling and packaging the SpinGen. We have been manufacturing and selling our metal SpinGen from our website for over a year and we are confident that we will be production-ready when the parts arrive. This will give us sufficient time to assemble, package and distribute the SpinGen to our backers for our estimated ship date.Learn about accountability on Kickstarter
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