PSA - CG shifts

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kellytehuna
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PSA - CG shifts

Post by kellytehuna »

Just a day or so ago, I was involved in a discussion on BBE about CG shifts and their effects on ball motion. It has been stated a number of times, with CAD proof might I add, that CG placement has NO EFFECT on the resultant ball motion.

My thought was this: Since there are some that swear that movement/placement does in fact change ball reaction, could it be because the CG shift they're talking about has an accompanying PSA shift, which changes the drilling angle and thus changes the way the ball rolls?

Is there merit to this line of thought, or am I clutching at straws? It seems to make sense in my head, but that doesn't mean its valid at all. LOL!
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charlest
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Re: PSA - CG shifts

Post by charlest »

As far as I have learned, the PSA for symmetric cored balls remains in the thumb hole. BUT when you add a weight hole, I have recently learned that that change (which changes the shape of the core) produces a change in the symmetry of the core making it into an asymmetric core. How strong the resulting PSA or mass bias strength is, I cannot say.

On the other side of the coin,I have also heard (without CAD or other confirmation) that, for slower ball speed bowlers (like myself) that the movement of the CG from one side to the other, with the pin remaining stable, can have an effect on the ball reaction. Like the overall hook being reduced by a firm or fast ball speed bowler, the overall hook is also increased, comparatively, by a slower ball speed bowler. Simialrly, I would guess that the CG has more of a visible or significant efffect, when the ball either hooks more or is thrown at a slower speed.
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Re: PSA - CG shifts

Post by purduepaul »

kellytehuna wrote:Just a day or so ago, I was involved in a discussion on BBE about CG shifts and their effects on ball motion. It has been stated a number of times, with CAD proof might I add, that CG placement has NO EFFECT on the resultant ball motion.

My thought was this: Since there are some that swear that movement/placement does in fact change ball reaction, could it be because the CG shift they're talking about has an accompanying PSA shift, which changes the drilling angle and thus changes the way the ball rolls?

Is there merit to this line of thought, or am I clutching at straws? It seems to make sense in my head, but that doesn't mean its valid at all. LOL!
Unfortunately you are grasping at straws, and allow me to explain. If you read the post on CG below you will see the data that says with a CG shift on a symmetrical ball. The center of gravity placement is just an imaginary spot in the ball. The PSA is determined by the Moment of Inertias of the bowling ball. If you read the center of gravity article it should clarify some more things.
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Re: PSA - CG shifts

Post by MathIsTruth »

charlest wrote:As far as I have learned, the PSA for symmetric cored balls remains in the thumb hole. BUT when you add a weight hole, I have recently learned that that change (which changes the shape of the core) produces a change in the symmetry of the core making it into an asymmetric core. How strong the resulting PSA or mass bias strength is, I cannot say.
I have produced CAD results on a symmetrically shaped core using a layout of 65x4x30 P4 with a total diff of 0.066 and int diff of 0.020. That is a diff ratio of .30. Keep in mind that a 65x4x30 P4 layout is a strong drilling.
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Re: PSA - CG shifts

Post by charlest »

MathIsTruth wrote: I have produced CAD results on a symmetrically shaped core using a layout of 65x4x30 P4 with a total diff of 0.066 and int diff of 0.020. That is a diff ratio of .30. Keep in mind that a 65x4x30 P4 layout is a strong drilling.
THAT'S HUGE!!!!
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Re: PSA - CG shifts

Post by Mo Pinel »

kellytehuna wrote:Just a day or so ago, I was involved in a discussion on BBE about CG shifts and their effects on ball motion. It has been stated a number of times, with CAD proof might I add, that CG placement has NO EFFECT on the resultant ball motion.

My thought was this: Since there are some that swear that movement/placement does in fact change ball reaction, could it be because the CG shift they're talking about has an accompanying PSA shift, which changes the drilling angle and thus changes the way the ball rolls?

Is there merit to this line of thought, or am I clutching at straws? It seems to make sense in my head, but that doesn't mean its valid at all. LOL!
Let me add my two cents. I invite purdue paul and Math Is Truth to comment.

When a hole is drilled into a bowling ball, the PSA moves toward that newly drilled hole and the cg mark on the surface of the ball moves away from that newly drilled hole. Therefore, the PSA and the cg mark move it opposite directions when a new hole is drilled into a ball. Paul and Steve elaborate if you choose.
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Re: PSA - CG shifts

Post by kellytehuna »

Thanks for that Mo. It's funny you should mention that. Just a few hours after creating this thread, I had a chat with Steve and he told me exactly what you just said. Once he said that, it was pretty obvious that the CG would shift in the opposite direction of the hole drilled. If you remove mass from one side of an object, the other side of the object now has more mass than the side you removed the mass from, thus pushing the CG in that direction. :)
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