Where did the idea come from?
During a tennis match, the SpinGen creator broke a string (textured, rough) on a newly strung racquet. He grabbed his backup, the same racquet strung with the same string, except this string was not new. As a savvy tennis player, he found that it was harder to “lift” up the ball over the net with his backup racquet. It was as if it had less power. He lost the match and wanted to restring his racquet before the next match. However, just before cutting the string on the backup racquet, out of curiosity he measured its tension and was surprised to find that no tension had been lost. Instead, the problem was that the friction marks on the strings’ top surfaces were worn off. If the friction marks could be put back on, the strings would work the same as new and wouldn’t need to be replaced…
After a few years and many prototypes, the SpinGen was born.

What Types of strings can generate more spin?
Rough strings because they have rough top surfaces for a better grip on the ball?
Studies have shown that the most useful strings are those with ball/string friction > 0.3 and that the performance of the strings deteriorates sharply if the friction drops below about 0.3.  See article: “Effects of friction between the ball and strings in tennis” by Mr. Rob Cross published in “Sports Engineering (2000) 3, 85 – 97”. “…a small decrease in the coefficient of sliding friction (between ball and string) below about 0.3 results in a large change in the rebound angle of the ball. This is accompanied by a slight change in rebound speed of the ball, but players are more likely to perceive these effects as a decrease in racket power since the ball lands short of the target and since the amount of topspin imparted to the ball is reduced…” 

Or, smooth strings because they have smooth string intersections for main strings to slide and snap back more efficiently?

In 2008, a Japanese Professor, Yoshihiko Kawazoe published an article: “Tennis Top Spin Comparison between New, Used and Lubricated Used Strings by High Speed Video Analysis with Impact Simulation” (Theoretical and Applied Mechanics Japan, Volume 57, National Committee for IUTAM, Science Council of Japan (2008), 511-522). In 2011, The Atlantic magazine published an article: “The New Physics of Tennis”by Mr. Joshua Speckman. The article includes a 10,000- frame-per-second video of strings hitting a tennis ball. These articles show that the smooth strings can actually generate more spin than the rough strings because the smooth string intersection allows the main strings to slide and snap back more easily. 

Both types of strings have their advantages, but you can’t have both…

These articles, however, do not contradict each other. When rough strings’ ball/string friction drops because their top surfaces are worn smooth by the ball, and friction between the rough strings remains high (making them hard to slide and snap back against each other), the string performance will drop.  Comparing rough and smooth strings when they are both new, smooth strings can generate more spin because the main string’s "slide and snap" movement plays a more important role in spin generation than a rough top string surface. But the rough strings do have a better grip on the ball. 

Until now...
​SpinGen works by combining the benefits of both rough and smooth strings. It only makes the top surfaces rough without increasing the friction between the strings. SpinGen is especially effective on smooth poly strings, such as Luxilon Alu Power and Babolat RPM Blast. These are the most popular tennis strings on tour, and are the string of choice for Novak Djokovic and Rafael Nadal, respectively. Strings treated with SpinGen grip the ball better, allowing the main strings to slide farther and faster along the cross strings. This lets them store more energy, and where the main strings snap back, more energy is added to the ball for spin generation. 

Lastly, see "How String-To-Ball Friction Affects Spin"posted by the Tennis Warehouse University. At the end of this article, it concludes that "...Thus, it would seem that the ultimate spin string (i.e., maximum spin generation) involves maximizing string-to-ball friction while minimizing inter-string friction. The data above demonstrates that this is indeed possible..." It is exactly what SpinGen is designed to do. 

1. Before using the SpinGen, we mounted the racquet on a stand and then shot tennis balls at a 45 degree angle to the string bed. We recorded each ball’s rebound landing location.
2.  We then used SpinGen to roughen the main strings of the same string bed. We shot tennis balls to the same string bed at the same angle and at the same speed, and recorded each ball’s rebound landing location.

3. In this experiment, the average rebound angle before SpinGen is 33 degrees; after SpinGen it is 25 degrees. The more the rebounded ball spins, the closer the rebound trajectory is to the perpendicular line.

4. Knowing the rebound angle, we could plot and estimate the slide/snap-back distance of the main strings during ball contact. In this experiment, before SpinGen: 4.1 mm; after SpinGen: 6 mm, about 50% farther.

5. Knowing the rebound angle, we could also plot and estimate the rebounded ball spin. In this experiment, before SpinGen: 1380 RPM; after SpinGen: 1880 RPM, about 30% more spin.

​More about this experiment >>

Main String Back Side

Watch How it Works video on Youtube

US Patent No: 8,622,096; 8,631,834 Content copyright 2020. Hansinova, LLC. All rights reserved.

Our Rebound Experiment
One way to estimate improved spin is by measuring the ball rebound angles before and after using SpinGen. We set up an experiment to measure this, and these results show that SpinGen improved spin.

ball: US Open heavy duty; ball speed: ~55 MPH; ball machine spin: none; ball shooting angle: ~45 degree
string: Luxilon Alu Power. main :60 lbs. cross: 62 lbs.
racquet: Head Prestige Microgel mid sizeType your paragraph here.

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Main String Front Side

A simple rebound experiment shows SpinGen treated string bed generates more spin...

SpinGen increases friction between strings and the ball without increasing friction between the strings themselves, so they can slide against each other.

Make Your Strings Bite!

SpinGen works by increasing the string-ball friction without increasing the string-string friction.  It roughens the top surface of your racquet's main strings where they make contact with the ball. This increases the friction between the ball and the strings, which allows the main strings to grab the ball better. At the same time, there is no increased friction between the strings themselves, and so the main strings will slide along the cross strings even farther and faster than before. This increased lateral movement of the strings stores more energy, and when the main strings snap back into place more energy is imparted to the ball for spin generation.  Our study shows that strings treated with SpinGen generate up to 30% more spin.

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