The location of the Low RG axis (riser pin) to the bowling lane, i.e. vertical, horizontal, in-between, will be entirely dependent on what RG contour the PAP of the bowler throwing the ball starts on and how far the PAP precesses, which will depend on the bowl speed/rev rate relationship.stevespo wrote:
The pin rarely stands perfectly vertically, but the ball is generally trying to do this, it just doesn't have enough time. That's why I said "somewhat".
I also think it depends on the bowler and the ball. When I use a long pin to PAP and with my lower tilt and forward roll, the pin is standing pretty tall at the pins. Contrast this with people who spin the ball. For most people that low RG axis is somewhere between horizontal and vertical, but anything above horizontal should have more gyroscopic inertia. Core shape and asymmetry also factors in. Or so my simple mind likes to think.
The location of the Low RG axis at pin impact is essentially a pointless marker. You could just as easily look at the location of the thumb hole and gather the same amount of useful information.
The reason people want the ball in the roll phase when entering the pins is because at that point the ball is on a straight line path and will have less deflection. It has maximum traction.
You can think of the three phases like this:
The skid phase it's like driving on ice with ice tires. You can turn the wheel any direction and it won't impact the direction of the vehicle. A bump will easily change your direction. The hook phase is like driving in the rain with good tires making a turn. You're steering the vehicle, but not as well as in good weather. If you hit a bump, it is harder to recover than in good weather, but easier than on ice. The roll phase in like driving on a nice dry road with good tires. Bumps in the road don't as easily effect your direction.
Hitting the pins is like hitting a big bump in the road. If the ball is skidding it will have a big deflection, if it's hooking it will have less, and will have minimum deflection when in a roll.
Of course, where you hit the pins has a dig impact on deflection as well, but the above scenario is an all other things constant type of scenario.