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Effect of Orientation Error on Racket Swingweight Measurement

A customer with an SW1 recently asked if it matters whether the racket is oriented with the head perfectly vertical, for swingweight, or perfectly horizontal, for spinweight measurements. I suspected that the result wouldn’t be very sensitive, but I wanted to quantify it.

I modeled a racket in CAD and adjusted the material densities to get a string bed of 17 grams and overall mass properties close to a typical tennis racket:

  • Mass: 333.5 grams
  • Balance: 33.2 cm
  • Swingweight: 306.8 kg·cm²
  • Twistweight: 13.6 kg·cm²

Then, I twisted it in 1° increments and output the moment of inertia about the swingweight axis:

Twist (°)Swingweight (kg·cm²)Difference (kg·cm²)
306.82
306.82+0.00
306.83+0.01
306.85+0.03
306.88+0.06
306.92+0.10
306.96+0.14
307.01+0.19
307.07+0.25
307.14+0.32
10°307.21+0.39

From the data, it seems unnecessary to be extremely accurate with racket orientation for typical swingweight measurements. At 5° of twist, which is easy to see, the swingweight result is only off 0.1 kg·cm². However, if measuring swingweight and spinweight to determine twistweight from the difference, orientation accuracy is more important. An error of 0.1 kg·cm² is more significant relative to the magnitude of twistweight.

These results should be valid for any swingweight measurement method.

If you have any questions about the SW1 or racquet measurement, leave a comment below.

4 thoughts on “Effect of Orientation Error on Racket Swingweight Measurement

  1. Is Twist weight really equal to Spin weight less Swing weight?

    1. Good question. I started to look into it, and I think I’ll create another post to address it.

      1. Thanks for the answer!

        I find this stuff fascinating! Eager to see your twist weight device

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