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Bowling balls and static weights – Part I

For some time there has been constant debate in the bowling world that has pretty much polarized the professional community. Do static weights REALLY matter?

Before you can even begin this discussion, you first have to understand what static weights are, how they are created and why they are such a big deal in the first place.

So, what are static weights? Static weights, in bowling terms are the static weight imbalances within a bowling ball. Bowling balls will weigh anywhere from 6lbs to 16lbs (2.72kg – 7.26kg). However, even in undrilled bowling balls, that weight is not evenly distributed about the geometric center of the ball. Due to manner in which bowling balls are constructed, a typical three piece ball consists of a dense inner core, a less dense outer core and cover. Static imbalance (static weights) are created by offsetting the center of gravity from the geometric center of the ball. How much you offset the inner core determines how much of a static imbalance you have. Pretty simple, right? Here is where the waters get a little muddied.

At the most, the inner core will only be moved 2mm or 3mm from the geometric center of the ball! That is a FRACTION of an inch! Every manufacturer marks the location of the heavy spot (Center of Gravity, or CG) on the surface of the ball. The location of the CG on the surface of the ball is simply the end point of the axis that extends from the geometric center of the ball, through the actual center of gravity to the surface of the ball. If center of gravity was located at the geometric center of the ball, the Pin locator would mark the CG as well. This kind of complicates issues for us, because the location of the CG is often several inches from the Pin locator. This makes it APPEAR like the CG is moved drastically within ball, when in fact, it has moved a miniscule amount.

Bowling balls are designed to have some top weight. If you align the ball with the CG at the top of the ball, there will a slight difference between the weight of the top half of the ball and the bottom half of the ball. This is top weight. In most cases, you have between 1oz and 3oz of top weight (28g – 85g), though I’ve heard of top weights as low as 0.5oz and as high as 5.5oz.

When we drill a ball, the static weight imbalances within the ball change, depending on where we remove weight from the ball! According to the USBC specifications, a drilled ball can have no more that 3oz top, or bottom weight and no more than 1oz of finger, thumb, or side weight. So, let’s define these terms for a drilled ball.

Like undrilled balls, top weight of a drilled ball is the difference between the top half of the ball and the bottom half of the ball. However, the top half is now found by placing the center of grip directly on the top of the ball. If there is more weight on the top half of the ball, the ball has top weight. If there is more in the bottom half, the ball has bottom weight.

Likewise, finger weight is found by extending a line through the center of grip, with the fingers above it and the thumb below. This is also known as the mid line. If there is more weight above the mid line, the ball has finger weight. If there is more weight below the mid line, it was thumb weight.

That leaves us with side weight. To find side weight, we draw a line that goes directly between the fingers and bisects the thumb hole. This line is also known as the center line. For right handers, if there is more weight on the right side of the center line, the ball has positive side weight. If there is more on the left side, the ball has negative side weight.

That seems like a good place to leave this article. In the next article, we will discuss in more depth how static weights are supposed to affect ball motion and why I think these thoughts are wrong.

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