Forms of bowling ball cores: Asymmetrical vs. Symmetrical
We have published several articles on bowling ball materials and shared recommendations for balls with various cover sheets, ranging from plastic to reactive resin.
However, today's post will focus on another part of the ball, which can come in several different types: the core of the ball.
In particular, there are asymmetrical and symmetrical bowling balls. What does this mean and how can you use that distinction to your advantage when choosing a bowling ball?
What are asymmetrical and symmetrical bowling balls?
The definitions can get a little technical, but here the main distinction, followed by the more important piece, is a discussion of why this is important:
For balls with a symmetrical core, “die RG (circle radius) The values of the Y-axes (High RG) and Z-axes (Intermediate RG) of the ball do not differ by more than 5% of the total differential of the ball. "
In contrast, asymmetrical core bowling balls have "the RG values (radius of gyration) of the Y-axes (high RG) and Z-axes (middle RG) of the ball differ by more than 5% of the total difference of the ball." (Source)
What exactly does that mean?
First, RG, or the gyro radius, is a measure (in inches) of the distance from the axis of rotation "at which the total mass of a body can be concentrated without changing its moment of inertia".
A ball with a small gyro radius (RG) spins faster and easier, which can lead to more ball movements and changes of direction. To name another frequently used term, the measured difference in the RG has an effect on the “stray light potential” of the ball.
One source describes well how this works.
With a symmetrically drilled ball you create "a smooth, controllable movement compared to an asymmetrical ball".
This asymmetrical ball, on the other hand, can “generate more surface at the break point and reacts faster to friction at the break point than symmetrical balls”. This can create more hooks, among other things.
The following image illustrates these concepts of symmetrical and asymmetrical bowling ball cores:
These exact measurements and terms may make more sense to a graduate physicist than even advanced bowlers, but hopefully the diagram and descriptions of the gyro radius and how it works with symmetrical and asymmetrical balls will be useful to you. While this isn't the most important consideration to bring when looking for the right bowling ball, it is definitely something to keep in mind.