How Drilling and Core Shape Affect Performance

For the pro shops out there, this blog of Creating the Difference will compare two different layouts in various core shapes for a specific style of player to see which hooks more – a 3.5 pin from the axis or a 5.5 pin from the axis. In this test, we will examine the performance effect of these layouts as well as the mass property changes through drilling.

To begin, here is some information about the bowler used in this test:

• Left-handed
• League average 247
• High Series 899
• Rev Rate 450 RPM
• Ball Speed 21.16 MPH
• Axis Rotation 45 degrees
• Axis Tilt 10 degrees
• Axis Point 5 inches over by 1⁄2 inch up

We used three different types of core shapes for this test: a simple pancake core, a symmetrical core shape and a High Mass Bias asymmetrical core shape. See Figure 1.

For all of the balls, we used two different layouts. The first layout is a 5.5 inch pin away from the bowler’s positive axis point with the Mass Bias at 45 degrees. The second layout is a 3.5 inch pin from the bowler’s positive axis point with the Mass Bias at 45 degrees. We did not use weight holes in any of the balls during this test.  This allows for all core mass property changes to be purely a function of drilling. All of the balls have a 4 ¾ total span. The finger holes are drilled with a 31/32 inch bit 1.5 inches deep. The thumb hole is drilled with a 1 inch bit 2.5 inches deep. See Figure 2.

For the test, we used actual physical measurements as well as computer design software to give us an in-depth look into the mass properties of the ball. We also collected performance data during the testing and evaluation.

Test 1 - The Pancake Core Shape

Figure 3 shows the mass properties for the undrilled ball as well as both the 3.5 inch pin and the 5.5 inch pin drilled balls.

In comparing the 5.5 inch pin ball to the 3.5 inch pin ball, there are slight differences in the mass properties of the two drilled layouts.

We then took both of these balls and collected performance information. See Figure 4.

In comparing the performance data, the 3.5 inch layout added performance in the area of total hook as well as backend. The 5.5 inch pin went further down the lane and to the left before hooking back to the pocket. Overall, the 3.5 inch pin was a stronger performing ball for the pancake core shape.

Test 2 - The Symmetric Core Shape

Figure 5 shows the mass properties for the undrilled ball as well as both the 3.5 inch pin and the 5.5 inch pin drilled balls.

In comparing the 5.5 inch pin ball to the 3.5 inch pin ball. You can notice the mass property values have greater differences between the two core types.  In both cores, the 5.5 inch pin has less differential than the 3.5 inch pin. The Mass Bias however, is higher in the 5.5 inch pin than the 3.5 inch pin for both cases. More gross weight is removed from the 3.5 inch pin than the 5.5 inch pin in both cases. Figure 6 shows the performance of the two drilled balls.

In this case the 3.5 inch pin layout was earlier but gave less total hook than the 5.5 inch pin layout. The 5.5 inch pin layout had more backend recovery this time as well. Overall the 5.5 inch pin was a stronger performing ball for the symmetric core shape.

Test 3 - The High Mass Bias Asymmetric Core Shape

Figure 7 shows the mass properties for the undrilled ball as well as both the 3.5 inch pin and the 5.5 inch pin drilled balls.

In comparing the 5.5 inch pin ball to the 3.5 inch pin ball, the mass property values have the most difference in the Mass Bias value. There is less differential and higher mass bias in the 5.5 inch pin compared to the 3.5 inch pin. Figure 8 illustrates the performance of the two drilled balls.

By comparison, it can be noted the 3.5 inch pin layout in this case went longer than the 5.5 inch pin layout and had significantly less backend recovery. The 5.5 inch pin layout hooked earlier still and had more overall hook than the 3.5 inch pin. Overall, the 5.5 inch pin was a stronger performing ball for the High Mass Bias asymmetric core shape.

RESULTS

In comparing the different tests, it can be noted the mass property values, in terms of Mass Bias and differential, tend to go up as we went from pancake to symmetrical to High Mass Bias asymmetrical core shape. The results indicate the higher the mass property values are undrilled, the stronger the drilled performance is going to be noticed in the 5.5 inch pin over the 3.5 inch pin. The drilling has a tendency to change the mass properties differently as we move from pancake to symmetrical to High Mass Bias asymmetrical core shape. This is a function of the core shape and the weight blocks that are impacted by the drilling.

So, which one hooks more?

As different bowlers have different statistics, the performance effect of core and drilling can change the results. The more you go toward the core being Asymmetrical, the stronger the overall performance is in the 5.5 inch pin over the 3.5 inch pin.

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