Ovvero come realizzo un fuoricampo per 50 centimetri, e forse anche meno, invece di essere preso al volo dall’esterno sulla recinzione, magari all’ultimo inning e sulla parità di punteggio, e la mia squadra vince il campionato.

Fino al 1999, le mazze da baseball venivano controllate in un punto preciso: il centro di percussione, ma le case costruttrici trovarono il modo di passare i test anche con mazze che sul campo avevano una performance maggiore di quella consentita. Aggiungevano massa alla mazza in un punto preciso, aumentando il momento d’inerzia, ma lasciando inalterati i valori sul centro di percussione.

Colpire un oggetto con un altro oggetto è la stessa azione che si fa migliaia di centinaia di volte su un campo da tennis.

centro-di-percussione.gif

It was possible to design a baseball or softball bat that would pass the BESR test but would perform much higher in the field. Essentially, manufacturers were able to cheat the test by manipulating the location of the COP. The figure at right shows experimentally determined bat performance as measured by the “bat-ball coefficient-of-restitution” (BBCOR) mentioned above in reference to the BPF test. The higher the BBCOR, the faster the ball comes off the bat. The blue data points are for an unmodified bat. Notice that the location of maximum performance is at 7-inches from the barrel end, while the location of the COP for this bat is only 5.75 inches from the barrel end. If the bat was tested at the COP the measured BBCOR would be 0.595 instead of the actual maximum value of 0.600. The red data points show the effect of adding 3-ounces of mass to the knob of the handle. Notice that the performance curve is essentially unaffected – that is, the maximum BBCOR is still 0.600 at a distance of 7-inches from the barrel end of the bat. But, the location of the COP has now shifted almost an inch closer to the barrel end. So, if the altered bat was tested at its COP the measured BBCOR would only be 0.575 instead of the actual maximum 0.600.

Physics and Acoustics of Baseball & Softball Bats
Daniel A. Russell, Ph.D.
Applied Physics, Kettering University
Contents of this are ©2005 Daniel A. Russell

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