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Old 10-05-2012, 08:03 PM   #228
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Originally Posted by kaiser View Post
So the MgR/I theory only applies during the backswing phase while the racket drops from high to low. Can you illustrate graphically what you mean when you say "the final angle of the racquetface at the end of this gravity-powered first portion of the swing is nearly entirely determined by the MgR/I value" and "if MgR/I is not tuned, then the second part of the swing will begin with the racquetface not quite at the right orientation"? How does the racket face orientation change during this phase?

I always understood that you were referring to the racketface orientation at the end of the stroke when it strikes the ball. As I understand it (see for a more authoritative description this article by Rod Cross:, the orientation of the racket face prior to impact changes as follows: During the second phase of the swing, as you defined it, the racketface first lags behind the wrist as the arm moves forward through the force applied by the player. Then, as the arm slows down at the end of the stroke, the racketface quickly catches up and accelerates forward through an arc around the wrist (dual pendulum), ideally striking the ball at the exact moment when the racketface is perpendicular to the intended hitting direction. Hence, slight variations in the timing of these processes during the second phase of the stroke will lead spraying of the ball from left to right. That's why I always thought you were referring to this second phase of the stroke when you were discussing MgI/R.

How does the timing of the first, backswing phase of the stroke affect the orientation of the racket face at impact? And doesn't the timing of the second, player-powered, phase of the stroke have a much more direct effect on the orientation of the racketface at impact and hence the accuracy of the shot?
I think Cross's statement is interesting:
"Having extra weight in the handle therefore allows a top player to control what he is doing. It slows down the forward motion of the handle and the backward motion of the head just enough so that he can swing the head around with a reasonable effort rather than an excessive amount of wrist torque."
The extra weight in the handle that Cross refers to (that permits swinging without wrist exertion) is the weight required to bring MgR/I up to a player's personal optimum value (most lightweight stock racquets lack enough handle mass for MgR/I to be optimized).

However, according to Cross's explanation, adding weight to the butt of the racquet would accomplish the task. But according to my findings, that is not true. The handle weighting must be higher in the handle to have the desired effect (i.e., increasing MgR/I). Thus Cross's explanation can be easily disproved (with a simple on-court experiment).
POG OS. 368 SW, 12.54" balance, 21.0 MgR/I.
Problend kevlar 16 / Prestretched SPPP 17, 72/50 lbs.

Last edited by travlerajm; 10-05-2012 at 08:16 PM.
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