From the Unoffical BR FAQ:MASS BIAS
Simply put, the mass bias in a bowling ball occurs when the mass (weight block or portion of weight block) is bias (more dominant) in one direction inside of an object (in this case a bowling ball). If you took a bulb shaped, single density core and positioned it dead center from side to side inside the ball, there would be no mass bias. You also would have a ball that is a pin in.
In order to kick the c.g. away from the pin to create a pin out ball, you have to "tilt" the core inside the ball, or place the entire core slightly off center. This became a common practice among manufacturers as the demand for pin out balls increased. When this is done however, you create a "dynamic imbalance" inside the ball because the mass is more dominant or "bias" in the direction of the "tilt" or "offset". That is the most important factor when discussing the mass bias, it is a DYNAMIC POINT ON THE BALL. Positioning the mass bias in different positions when laying out a ball will have a great impact on the "motion" the ball will make as it is going down the lane (even arc, hook/set, skid/flip and so on).
There are people who will argue that static imbalances (finger weight, side weight etc) are more important than dynamic imbalances. My reply to that, is that a dynamic imbalance is a real point in the ball, it is constant and does not change unless you alter it by drilling into it with a drill bit. A static imbalance or the c.g., will change as soon as you put one hole in the ball. It will change again with each additional hole you put in the ball as well. While static weights can be used to "fine tune" the reaction of the ball at the break point, it is the dynamic lay out that dictates the roll of the ball. If a pro shop operator truly understands the principals of the mass bias and how to apply them, they can greatly increase your overall satisfaction with the ball you purchase.
On a ball that does not have a premarked MB its theoretical position can be found by measuring from the pin through the CG 6.75".
AFFECT OF PIN PLACEMENT
Pin to PAP distance:
0" - minimum flare potential, core is in its most stable position, earliest roll with smoothest arc.
1 1/8" - 1/3 of flare potential, stable core position, earlier roll with smooth arc.
2 1/4" - 2/3 of flare potential, semi stable core position, early roll with strong arc.
3 3/8" - max flare potential, most unstable core position, medium length with the most hook potential.
4 1/2" - 2/3 of flare potential, semi stable core position, late roll with flip/arc reaction.
5 5/8" - 1/3 of flare potential, stable core position, later roll with a flip reaction.
6 3/4" - minimum flare potential, stable core position, latest roll with strongest flip.
Remember : These reaction characteristics are all relative to the conditions they are being used on and may not perform as expected due to burning up too early or not setting up early enough.
AFFECTS OF MASS BIAS (MB) PLACEMENT
As the angle goes from 75° (strong/flip) to 0° length will be reduced and have more of an arc reaction. From 75° to 105° length will increase and have more of an arc reaction. Beyond 105° the reaction will keep a very similar reaction but with more length.
Remember : These only enhance the characteristics of the given ball and Pin placement and the flip (strong) position may not necessarily have the biggest backend reaction on given condition due to many other variables that affect ball reaction (bowlers specs, lane condition, etc.)
DEGREE SYSTEM
The degree system of drilling a ball is when a drill pattern is described or laid out by using the relationship between the angles of the lines from PAP to Pin and Pin to MB.
Examples: (A=PAP, P=Pin X=MB)
P-A-X is 0° P-A is 45° P-A is 90° P-A is 135° X-P-A is 180°
..................\............|............/................
...................X...........X..........X.................
These are obviously not exact but they are good enough to get the meaning across.
PAP (POSITIVE AXIS POINT)
The axis of the ball during the first few revolutions that is created totally by the bowlers release style. The point on the ball that is equidistant from all points of the release ball track.
Ways to find it:
Least accurate: Draw a perpendicular (90°) line 6.75" from your track through grip center the end of the line will be close to your PAP.
Very accurate: Use an Armadillo Axis point locator tool. Place the Armadillo on your track using the line that most closely represents your track arc and mark the spot indicated by the Armadillo.
Exact: Roll low flare (spare) ball down the center of the lane where the highest concentration of oil is then using a grease pencil trace your track. Place the ball in a spinner with the track down and orient the ball to where when it it spinning the trace line does not wobble up and down. Then take the pencil and place it on the top of the ball and move it around until it goes from making a circle to a defined dot, or use a quarter scale/pro sect tool and draw a line connecting your track at points that are 180° from each other and repeat the step at a point near 90° from the first line where the 2 lines intersect is your PAP. If you do not have a low flare ball you can use any ball as long as you use the track that is closest to your thumb and farthest from your fingers. This is the release track, because as a ball flares the track migrates away from the thumb and towards the fingers.
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BR FAQEdited on 12/15/2010 0:09 AM
