Originally Posted by
JAnderson
The first part of "stacked leverage" is the pin position.
Here's what you need to know about layouts with a 3.5-4.0 inch pin-to-PAP (positive axis point) layout. This is the “leverage” part of “stacked leverage”. Disregard all other factors such as extra holes, mass bias, and center of gravity for the moment. This pin position allows the ball to tap into its maximum flare potential (You're "leveraging" the ball's full flare potential/imbalance). Flare potential changes from ball to ball, based on its core shape, density, placement, etc. The greater the radius of gyration differential (often just called “differential”) the greater the flare potential of the ball. Flare is the result of the core causing the ball to “wobble” as it travels down the lane. On a flaring ball, with each revolution of the ball, the ball rolls over a different part of its cover. You may see oil rings on your ball that resemble a bow tie in two places on the surface of the ball.
The end result of flare is that the ball will hook more in the oil. The reason being that as the ball revolves and flares, a new, clean part of the surface of the ball comes in contact with the lane allowing for maximum friction. The opposite would be a ball that does not flare or flares very little. Now, as the ball rolls through the oil, the same part of the surface of the ball contacts the lane and more and more oil/conditioner builds up on the same part of the ball. That means less friction and less hook.
More flare does not create more hook where there is no or little oil/conditioner. Actually, with a reactive resin ball, a flaring ball may hook less on the dry part of the lane than a non-flaring ball. This is because of the nature of what makes reactive resin “reactive”. As the ball encounters friction, the surface of the ball heats up. As “reactive” resin heats up, it become more tacky or “sticky”. That means a lower coefficient of sliding friction. The ball can "grab" onto the lane and hook more. A ball that flares will heat up the surface of the ball at different points on the surface of the ball. A non-flaring ball will heat up the part of the ball in contact with the lane over and over again. More heat, more tackiness, more grab, more reaction, more hook. (Assuming the ball isn't hooked out).
So if you add the two above together, balls with maximum flare tend to hook more in the oil and less on the dry than their non-flaring or weaker-flaring counter parts. The overall effect is that the shape of the ball will tend to be more like a banana and less like a hockey stick.
The other part of this layout, the “stacked” part of “stacked leverage” refers to the mass bias (and center of gravity on a symmetric cored ball) being directly “under” the pin - actually being the same distance from the positive axis point – thus the pin is “stacked” on top of the mass bias (center of gravity on symmetric balls).
There is much debate as to whether or not this part of the layout has any noticeable effect for balls with a symmetric core. I will not feed the trolls. For the sake of completeness, if there is a noticeable difference it is a small difference that can easily be created by changing any number of factors such as sanding the ball, polishing the ball, throwing the ball faster/slower, etc.
For balls with asymmetric cores, the layout creates the “strongest” starting point (or perhaps better worded as the most distant starting point) from which the ball can seek its preferred spin axis. If you don’t understand all that, don’t worry. You really need to have a good understanding of 4-dimensional physics (time being the 4rth) to understand intermediate spin differentials, preferred spin axis, axis migration time, etc. All you need to understand is that when the mass bias on an asymmetric ball is placed in this location, it aligns the core in such a fashion so that it delays hook as much as possible. That doesn’t mean that the ball will hook less, just that it will wait until it is further from the foul line before it hooks when compared to balls with (all other factors being equal) the same pin position but with the mass bias being in a different position. You’ve just taken your banana-like ball reaction shape and turned it into a banana-on-a-stick ball reaction.
Remember that none of this takes into account the bowler’s release, chosen line (is the bowler throwing it into the gutter?), rev rate, speed, etc. We’re isolating to the ball layout and comparing it to what other ball layouts create. You mileage can and will vary due to other factors.
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