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 Post subject: Rules For Cores??
 Posted: Tue Apr 17, 2018 8:58 am Post Number: #1 Post
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When I look at all the various types of cores that I see out there, inside of bowling balls made by different manufacturers, it would seem apparent to me that the PBA has not set any regulations concerning the Cores. They all seem to be extremely different and unique.

For a while there, in the golfing world, golfers in the PGA were using long handled putters, which eventually got outlawed by the officials of the PGA.

In baseball you’re not allowed to put cork in your baseball bat.

So where is the regulation of the cores in a bowling ball? Has this already been addressed? What are the regulations concerning what you can put inside of a bowling ball; what size restrictions apply; where it can and cannot live, inside a bowling ball??

I bring this up, because I’m an advocate for leveling the playing field. Everything else being equal in bowling, I would imagine that there ought to be a set of standards that you cannot violate, in order to allow the average bowler to be just as able as the pro bowlers, if they set their mind to it, because the equipment is the same. Sort of like NASCAR, in the way that they regulate the cars going out on the track. Standardize the cores; by shape, size, and location. (DID find Rules about balls in “Section 11”
of the official Rules of Bowling, as found on the PBA.com website. I don’t see any “core” restrictions: https://www.pba.com/Content/images/memb ... leBook.pdf). Perhaps there SHOULD be??

(Side note: Yesterday I stumbled on a television show that ran in the early 70s called “Celebrity Bowling,” which ran for three years. It was interesting. Anyone remember that show?)

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 Post subject: Re: Rules For Cores??
 Posted: Tue Apr 17, 2018 11:42 am Post Number: #2 Post
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You are looking in the wrong place. The PBA does not set the standards and limits on bowling balls. They simply follow the rules set by the USBC, much like the PGA follows the rules set by the USGA. Check out the USBC website to find the current limitations set on bowling ball cores. These "rules" are set to change in the near future.


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 Post subject: Re: Rules For Cores??
 Posted: Tue Apr 17, 2018 3:02 pm Post Number: #3 Post
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There is a specification made by USBC that limits RGs which basically are a function of core shape, I´m pasting it from the USBC Bowling Technology Study:

"Radius of gyration (RG) specifications were first implemented in 1993, when the American Bowling Congress set the limits at 2.430 to 2.800. A decade later, in 2005, USBC changed the specification, reducing the maximum differential RG from 0.080 to 0.060. USBC stated the change was an effort to control flare and entry angle. In 2010, the lower RG specification was changed from 2.430 to 2.447 and set the minimum model average at 2.460."

There´s more information on it but right now I´m out of time.

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 Post subject: Re: Rules For Cores??
 Posted: Tue Apr 17, 2018 3:06 pm Post Number: #4 Post
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The current USBC specs are below. They are actually in a table which didn't copy and paste true, so the link at the bottom takes you to the USBC Equipment Specification Manual, look at Pages 6 & 7. -- JohnP

Specification Minimum Maximum Circumference 26.704” 27.002” Diameter 8.500” 8.595” Roundness None 0.010” total run out Hardness 72 None Radius of gyration** 2.460” 2.800” Differential radius of gyration* None 0.060” Coefficient of restitution* 0.650 0.750 Coefficient of friction* None 0.320 Mohs’ Hardness None 6.0 Surface Roughness – Ra None 50 μin


http://usbcongress.http.internapcdn.net ... Manual.pdf


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 Post subject: Re: Rules For Cores??
 Posted: Tue Apr 17, 2018 3:11 pm Post Number: #5 Post
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Thank you JohnP for the correction.

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 Post subject: Re: Rules For Cores??
 Posted: Wed Apr 25, 2018 9:34 am Post Number: #6 Post
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2y2 wrote:
There is a specification made by USBC that limits RGs which basically are a function of core shape, I´m pasting it from the USBC Bowling Technology Study:

"Radius of gyration (RG) specifications were first implemented in 1993, when the American Bowling Congress set the limits at 2.430 to 2.800. A decade later, in 2005, USBC changed the specification, reducing the maximum differential RG from 0.080 to 0.060. USBC stated the change was an effort to control flare and entry angle. In 2010, the lower RG specification was changed from 2.430 to 2.447 and set the minimum model average at 2.460."

There´s more information on it but right now I´m out of time.


I’m no expert, and I’m not going to pretend that I understand everything that’s in this regulation, and what it means, but......... unless I’m missing something, all of those specifications seem to relate to the outer surface of the bowling ball and the action of the bowling ball.

I suppose it makes sense that whatever shape the core is, has an effect on the flare and entry categories and so forth, but they don’t seem to speak directly to core shapes, core size limitations, the material the core is made out of, and so forth????????

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 Post subject: Re: Rules For Cores??
 Posted: Wed Apr 25, 2018 6:19 pm Post Number: #7 Post
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You cannot separate one thing from another, RGs are functions of the Moment of Inertia and moment of Inertia involves mass, cores are the heavier part of the bowling balls. The mass of the core and its shape is what change RGs distribution of the ball, a single material sphere will always have the same RG throughout the sphere, it is in the core where the RG changes occur, so when you regulate RG values, you´re indeed regulating core properties. Finally the bowlingball works as a system, the core by itself does nothing until it is bonded inside the ball and all RG measurements on any bowling represent the system as a whole because even when the densest part of a ball is the core, all other components add mass to the system modifying RGs distribution.

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