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dougb
05-15-2009, 08:51 PM
Can someone explain to me the difference between the two, in simple terms?

I understand the difference when I throw the balls, as every asymmetrical ball I threw made a hard snap at the break-point. I prefer the predictability of symmetrical cores, as I like a smooth, continuous arc to the pocket.

But I don't know the science behind the ball reaction. Please explain!

Thanks

onefrombills
05-15-2009, 10:30 PM
A bowling ball has a heavy core of given density; the core has an asymmetrical shape that affords no planes of symmetry. The core is encompassed by a spherical shell of lower density; the shell may include two layers, a relatively hard outer layer of an acrylated resin or urethane resin and a more resilient, softer inner layer, usually of urethane or filled polyester resin. A balancing weight, to compensate for finger holes to be drilled into the shell, is preferably an integral part of the bowling ball core. The density of the balancing weight is usually greater than the density of the rest of the core.

bowl1820
05-15-2009, 10:37 PM
This might not be just what your looking for but! these have some interesting info on ball dynamics.Which might be helpful.

See in " The Mo Number" part, they talk about Non-Symmetrical and Symmetrical Weight Blocks
Matching Ball to Bowler (http://www.bowlingcoach.com/CEOct02.pdf)

also see this one
Balls Point of view (http://www.bowlingcoach.com/CESept02.pdf)

JAnderson
05-18-2009, 05:52 PM
Sometimes, I wonder if the ball companies themselves are confused about what constitutes a symmetric or asymmetric core. Generally speaking, it appears a core is considered symmetric if, from one end of the core to the other (the pin being the top end of the core) it is radially symmetrical.

Radial Symmetry is defined by Merriam-Webster as "the condition of having similar parts regularly arranged around a central axis". Here are some radially symmetrical patterns (http://www.childs.mccsc.edu/art2001/art1p2.htm).

Most asymmetric cores have a single spoke or "knob" on one side of the core that doesn't exist on the other (again, along the Z-axis or top-bottom axis).

USBC research (http://www.bowl.com/articleView.aspx?i=13372&f=21) on this subject has not been 100% completed to my knowledge. The key question is listed at the bottom of the article.

Ball manufacturers and self-proclaimed gurus often claim that asymmetric cores can be drilled to create an earlier, smoother hook, but any scientific evidence or good, physically accurate explanation as to why is lacking.


I understand the difference when I throw the balls, as every asymmetrical ball I threw made a hard snap at the break-point. I prefer the predictability of symmetrical cores, as I like a smooth, continuous arc to the pocket.

I'm a "proof is in the pudding" kind of guy, but there are probably other variables in play that have helped you form this conclusion including the surface of the ball, the surface of the lane in use, the pattern applied to the lane, release, and ball drill/layout. That doesn't mean the conclusion is wrong, just that we don't know all of these other factors.

Having thrown a large number of different balls from different manufacturers across a large number of different lane surfaces and conditions, I can't honestly say I've noticed any particular tendency of motion in asymmetric cores versus symmetric cores. That's not to say it doesn't exist, but the affect may be too slight to make a noticeable impact.

JAnderson
05-18-2009, 05:58 PM
Here's a US patent for Bowling ball with asymmetrical core (http://www.freepatentsonline.com/5951407.html). Kind of interesting.

bowl1820
05-23-2009, 04:17 PM
But I don't know the science behind the ball reaction. Please explain!


Ok this should help, of course your eyes might glaze over after a bit.

what_makes_a_bowling_ball_hook.pdf (http://bowlingknowledge.info/images/stories/what_makes_a_bowling_ball_hook.pdf)

This article, by Cliff Frohlich, was published in a 2004 issue of the American Journal of Physics. A scholarly look at ball motion.

Sample-
"This article presents exact equations of motion for a rotating bowling ball in a form that explicitly
separates contributions due to nonequal principal moments of inertia, center-of-mass offset, and
friction between the ball and lane."