rjd8675309 wrote:This is a very interesting discussion but fails to address the primary question concerning the Anderson fastpitch bats.
The bats are not the specific weight advertised. They are approx. 2.8 oz. heavier than listed.
I was given an explanation by the former engineer that it is the swing weight. Considering I graduated with an advanced engineering degree 25 years ago, there must have been a fundamental change in the laws of physics between then and now.
The basic premise of f=ma is understood, and the application of MOI is correct, but the relevance to rotational velocity is flawed in respect to swing weight. In the case of these bats, the knob is weighted. The theory would be correct if the wrists were the only axis of rotation. I have never seen a batter swing only with his/her wrists. To get to the true physics behind a swing, multiple computations must be used due to multiple rotational axis (body rotation, wrist rotation, etc.).
The bottom line is that the bats are very good and comparable to carbon composites due to the additon weight (f=ma). If the batter can maintain bat speed, the heavier the bat, the better.
Okay, let me try it again
The full bat swing movement is a rotation within a rotation. The initial rotation (alpha rotation) is about the center of the body and the weight of the bat in this phase of the swing has a negligible effect on bat speed at impact. The reason for this is that alpha rotation is about the hitter’s center of gravity using very large muscle groups acting as the hips rotate and hands rotate into the zone. Comparing the mass of the body being accelerated in relation to the weight of the bat, the weight of the bat is very minor (2 lb vs. 100 lb) and has little effect on the speed of this alpha rotation.
The small secondary rotation (beta rotation) which happens at the hands begins after the alpha rotation is well under way and includes the shoulders to start, then arms and finally wrists and hands. Batspeed is a combination of the speed of both rotations. This beta rotation uses the smaller muscle groups controlling smaller body mass, wherein the weight of the bat becomes important. However, the weight of the bat only matters in reference to a rotational system. Of course, this weight equivalent is found to be the MOI of the bat with respect to the actual point of bat rotation. Granted, this point of rotation is not at 6 inches into the handle (between the hands) where manufacturers typically make a measurement. The actual point is seen to be somewhere a couple inches off the end of the knob, but neglecting particularly exotic bats, these two measurements of MOI are fairly proportional with respect to beta rotation. As it is this MOI, and not the overall weight of the bat, that has the greatest impact on the energy required to swing the bat, we reference this in speaking of swing weight. It is for this reason that our bats can have different swing weights from their actual weight or from equivalently weighted competitor’s bats.
It is our empirical experience that the way we choose to weight bats results in a superior feel throughout the swing, which corresponds to psychological benefits that produce very real performance benefits that would be difficult to further quantify here in scientific terms. However, regardless of this reason for how we weight our bats, the fact is that the swing weight of the bat is quite separable from the absolute mass of the bat. Further, while F=ma is true, the pseudo-ballistic collision of the bat with the ball results in a very short time of interaction (approximately 1 ms), meaning that energy stored in mass far from the barrel of the bat will be transferred more into vibrational energy of the bat rather than a kinetic event between bat and ball. Additionally, the integral of the velocity of each mass particle of the bat is what will determine the impulse delivered by the bat to the ball. Since my bat knob may be moving at only 25mph while my barrel is moving at 70mph, the mass in the barrel provides a larger impulse contribution than the mass in the knob. This and the factors outlined above are again why the swing weight of the bat (and the efficacy of the bat and ball collision) is quite separable from the absolute mass of the bat.
If it is excessive, call our service department and we'll take care of it.
