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Old 02-08-2013, 06:25 AM   #31
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Join Date: Feb 2006
Location: Stuck in the Matrix somewhere in Santa Clara CA
Posts: 10,575

Here are a couple of links of my posts from 2008 & 2009 that might shed more lights on X, Y and Z axis spins:

The following link talks a bit more about Z-axis spin (aka bullet spin):

In the old Operation Doubles web site, Kathy Krajco talks about the altered axis of rotation for a twist serve. She does not give a name to the Z-axis component of spin but she does talk about how the resultant spin axis is different for a twist serve than it is for a regular topspin-slice serve.

For most shots that we discuss in tennis (with topspin, underspin & sidespin), the actual axis of rotation of the spinning will be perpendicular to the flight of the ball. However, due to the presence of a Z-axis spin, the actual rotation of the ball on a twist serve is no longer perpendicular to the flight of the ball -- it is offset somewhat from the perpendicular.

Here is an archive of the late Kathy Krajco's old OD web site page. Unfortunately, some of her excellent gifs showing the spins may no longer work:

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