Posted by: Jim (jwelborn@lexcominc.net) on Fri Nov 18 21:03:03 2005

> >>> I believe the hip slide or weight shift achieves two things. It initiates momentum that will be used in rotation; and it creates a favorable orientation for the axis of rotation by bringing the bottom end of the axis to the front heel which results in its familiar backwards tilt. <<<
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> Hi Jim
>
> I agree that for batters who are more erect in their stance, hip slide “creates a favorable orientation for the axis of rotation by bringing the bottom end of the axis to the front heel which results in its familiar backwards tilt.” I have also noted less hip slide with batters who have their axis tilted prior to the stride.
>
> Now let us assume weight shift does generate linear momentum that contributes to generating bat speed. The question then becomes – how much does it contribute? If we restrict a batter’s ability to shift weight forward, what percentage of bat speed would be lost?
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> As I discussed with Ray in an earlier post, we ran a simple test that would take weight shift out of the equation. We had the batter perform the swing while sitting in a swivel chair. The chair would now support his weight, and his legs were only used to rotate the body about a fixed axis. We found he could generate bat speeds about equal to his longer stride swing.
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> Jim, I realize this is just one test. But it does raise an important question – What percentage of the bat speed generated would you attribute to linear momentum? I would place it at zero to two percent – what figure would you estimate?
>
> Jack Mankin



Jack,

You stated, “As I discussed with Ray in an earlier post, we ran a simple test that would take weight shift out of the equation. We had the batter perform the swing while sitting in a swivel chair. The chair would now support his weight, and his legs were only used to rotate the body about a fixed axis. We found he could generate bat speeds about equal to his longer stride swing.”

When you performed your swivel chair experiment did you consider the effect of gravity? If the batter is supported by a chair, his leg muscles are not expending energy to support his weight. Therefore he could possibly have more energy available to direct into rotation resulting in artificially increased bat speed during the experiment.

On the other hand, during a real swing his legs are supporting his weight and some leg muscle energy must be consumed to perform the act of standing. By creating the positive linear move of the hips it is entirely conceivable that the resulting kinetic energy that is released would, in fact, result in enhanced rotation that would not be attainable without the linear move. In other words, the linear move provides energy that offsets energy consumed by the act of standing upright.

You asked the question, “What percentage of the bat speed generated would you attribute to linear momentum? I would place it at zero to two percent – what figure would you estimate?”

The answer is we have not experimented to quantify this. But we do train our batters to set up rotation with negative and positive movement. The ones who get it right do increase their power and percentages.

I commend you for your experiments, analysis, and willingness to discuss.

Jim