bowl1820
Online Bowling Notes #01
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, 07-05-2014 at 05:57 PM (29689 Views)
RG: Radius Of Gyration.
The RG of a bowling ball tells you how soon the core is designed to roll.
A Low RG ball (aka: a Center Heavy ball) is easier to "rev up", rolls earlier and tends to mean earlier hook, more midlane reaction,a more evenly arcing ball used on wetter conditions.
A High RG ball (aka: a Cover Heavy ball) is harder to "rev up", rolls later and tends to mean later hook, more backend reaction, tends to be more angular.
The Low RG axis is the pin and the High RG axis is the PSA.
Total Diff = High RG - Low RG
Int Diff = High RG - Int RG
Simple RG scale (there are others):
Low RG: 2.460" - 2.570"
Med. RG: 2.570" - 2.680"
High RG: 2.680" - 2.800"
Here's another:
Low RG = 2.430 to 2.540
Med RG = 2.541 to 2.690
High RG = 2.691 to 2.80
The RG Differential aka:The Differential:
Shows the difference between the low RG and the high RG.
The Differential indicates 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.
Simple Differential scale (there are others):
Low Diff.-RG: .01 - .02 (low flare potential)
Med. Diff.-RG: .021 - .04 (med flare Potential)
High Diff.-RG: .041 - .08 (high flare potential)
Basic guide:
A lower RG ball with a low differential will produce an earlier rolling ball with a small arcing motion.
A lower RG ball with a high differential will produce an earlier rolling ball with a larger/stronger arcing motion.
A higher RG ball with a low differential will produce a later rolling ball with an angular backend motion.
A higher RG ball with a high differential will produce a later rolling ball with a strong, somewhat angular backend motion.
Suggestion for using the undrilled ball #s to help anticipate ball reaction.
1) Take the min. RG # and add 70% of the total diff to it. That'll give you the approximate RG of the PAP for about 80% of the layouts. The RG of the PAP is the only RG that matters to the motion of the drilled ball.
2) Divide the int. diff. of the undrilled ball by the total diff. of the undrilled ball. That'll give you the diff. ratio. That tells you the potential of the ball to respond to friction.
Diff. ratios (using the drilled diff.):
>.45 is strong reaction
.25 to .45 is medium reaction
<.25 is smooth reaction
Ball Motion:
There are 3 phases of ball motion, the skid phase, then the hook phase and finally the roll phase. The first and second transitions is what we call the points which seperates these phases. The skid and roll phases are linear in nature which means linear equations can be used to model the ball motion. The hook phase is modeled by a quadratic equation. The vertex of that parabolic curve coincides with the breakpoint. It occurs somewhere between the first and second transition.
Dual Angle Info:
The Dual Angle Layout Technique is made up of three measurements:
1. The Drilling Angle: Which affects the length of the skid phase of the ball.
Higher angles = A Longer Skid phase.
Lower angles = The quicker the transition into the hook phase.
2. The Pin to Positive Axis Point (Pin-to-PAP) distance:
The Pin to PAP distance affects the amount of the flare.
3. The Vertical Axis Line (VAL) angle: Controls how long the ball remains in the hook phase.
Smaller Angles to the VAL lowers the RG, and increases the total differential of the ball. This results in the ball reving up faster and transitioning faster from the hook into the roll phase of the ball.
Larger Angles to the VAL raises the RG, and decreases the total differential of the ball. This results in the ball reving up slower and transitioning slower from the hook into the roll phase of the ball.
The comparison of Drill angle and VAL angle is expressed as a Ratio... Drilling Angle:VAL Angle
Ratios determine the balls break shape.
1. The drill angle helps determine the length of the skid phase of ball motion.
2. The val angle helps determine the length of the hook phase of ball motion.
3. The drill angle + val angle = the total length of ball motion before the ball reaches the roll phase.
A. A higher ratio of the drill angle to the val angle = longer and quicker reaction to the dry. (more of a
skid /snap ball motion)
B. A lower ratio of the drill angle to the val angle = earlier and slower reaction to the dry (smoother &
more continuous ball motion.)
Some of the common Lane surfaces in order of decreasing friction are:
Guardian (most friction)
wood (different coatings change friction)
Brunswick Lane Shield
AMF HPL and SPL
Original Brunswick AnviLane (if it has been polished)
new Brunswick Pro AnviLane (textured)
early Brunswick Pro AnviLane (least friction)
The hardness of the sub strait, the foot print that the ball produces on the surface, and the texture are the determining factors in determining the friction between the ball and the lane.
USBC specs a minimum of 35 Sward hardness for synthetic panels. Though the exact hardness is proprietary info to the manufacturer.