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 Post subject: Differential
 Posted: Thu Dec 28, 2017 9:48 pm Post Number: #1 Post
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Hello from Greece!
I have a question because I'm confused... What is the definition of Differential and what measurements are used to find it? It would be great if i can have an example because I'm visual learner!!! ;)


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 Post subject: Re: Differential
 Posted: Thu Dec 28, 2017 10:13 pm Post Number: #2 Post
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The Radius of Gyration (RG) Differential aka:The Differential:
Shows the difference between the low Radius of Gyration (RG) and the high Radius of Gyration (RG).

The Low RG axis is the balls "pin" and the High RG axis is the "PSA". (PSA=Preferred Spin Axis aka: Mass Bias (MB))

(see the video below at about the 1:40 mark for how they measure the high & low rg RG)

The Differential is a indicator of the potential for track flare.

The lower the differential the closer together the track flare rings are.

The higher the differential the further apart the track flare rings are. Also the ball tends to hook more sharply as compared to the low diff. ball.

Also read these for how RG is measured:
Radius of Gyration (RG) of Asymmetrical Bowling Balls (SOP-BALL-1)
http://usbcongress.http.internapcdn.net/usbcongress/bowl/equipandspecs/pdfs/SOP-BALL-1%20Asymm%20RG.pdf

Radius of Gyration (RG) of a Symmetrical Bowling Ball (SOP-BALL-2)
http://usbcongress.http.internapcdn.net/usbcongress/bowl/equipandspecs/pdfs/SOP-BALL-2%20Symm%20RG.pdf

USBC Ball Approval Process

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 Post subject: Re: Differential
 Posted: Fri Dec 29, 2017 8:31 am Post Number: #3 Post
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bowl1820 wrote:
The Low RG axis is the balls "pin" and the High RG axis is the "PSA". (PSA=Preferred Spin Axis aka: Mass Bias (MB))

A lot of great explanations as usual from bowl1820.

I thought I would add this just for clarification sake:
Symmetrical balls have both a low RG axis and a High RG axis and do not have a PSA until after drilling. The High RG axis is not the PSA. The PSA or "mass bias" is the "Intermediate Differential" (difference between the Intermediate RG and the High RG).

MathIsTruth explained it this way:
"Instead of planes, lets think of the axis through the ball at various locations. The PSA is one endpoint of the high RG axis. The pin and Low RG have similar relationship. The difference between the High and Low Rg values is the total diff. The high and low rg axes are always perpendicular to each other. The int RG axis is perpendicular to both the high and low RG axes. The difference between the high and int RG values is the intermediate differential."

viewtopic.php?t=2976


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