| Bowling can be traced back to | | | | delivery that starts the ball in a skid |
| approximately 5200 B.C., when the | | | | that evolves into a roll that hooks into |
| ancient Egyptians used stones for their | | | | the pins. |
| balls. | | | | It has been known since before the 1960s |
| The first bowling balls used in the | | | | that a "full-roller" type of delivery |
| United States were made of wood, | | | | does not hook as well as "3/4 rollers" |
| especially oak. In about 1906 the first | | | | on oily lanes. On successive rotations, |
| hard rubber balls were produced, and | | | | the "full roller" repeatedly contacts |
| these remained the standard until the | | | | the lane on the same full |
| 1960s and 70s. These decades saw the | | | | circumferential circle, on which the oil |
| emergence of plastic (polyester) balls. | | | | accumulates, making it harder for the |
| In the early 1970s, people began | | | | side-roll to find traction and create |
| experimenting with the hardness of the | | | | hooking action. The "full-roller" had |
| plastic balls, notably PBA member Don | | | | been the dominant choice before the |
| McCune, who invented the "soaker" - a | | | | changes in lane coatings and oil. The |
| plastic (usually polyester} ball he | | | | "semi-roller" is now preferred (it may |
| softened "in the garage" with chemical | | | | also be called "3/4 roller" or by other |
| solvents. These and balls subsequently | | | | slang terms). With a 3/4-roller a bowler |
| manufactured with the resulting softer | | | | puts the ball into a rotation whose |
| cover came under USBC scrutiny because | | | | contact ring is smaller, and on |
| of the increased scoring. A ball | | | | successive rotations enlarges |
| hardness rule was established, based on | | | | (subsequent examination of the ball |
| durometer readings, which barred some of | | | | often shows a flaring of the circles of |
| the softer balls. | | | | oil). This is because at every spot |
| At some point in ball making and | | | | along the circle friction reduces the |
| drilling the USBC introduced ball | | | | rotation, and that includes the spin |
| balance regulations to prevent people | | | | component, causing rotation on a |
| from taking advantage. It was possible | | | | continually larger circle. This has the |
| to drill the grip at a location relative | | | | effect of bringing relatively dry ball |
| to the weight block so that it would | | | | surface in contact with the lane, |
| achieve some effect, such as to help the | | | | increasing traction for both |
| bowler make it roll earlier or hook | | | | forward-roll and side-roll. It probably |
| more. | | | | goes without saying why bowlers often |
| In 1984 AMF and Columbia began | | | | wipe oil off the ball. |
| manufacture of the very first | | | | Another effect of ball imbalance (either |
| polyurethane cover stock bowling balls, | | | | static or dynamic) is the ability to |
| the AMF Angle and Columbia U-Dot, and | | | | introduce gyroscopic effects on the |
| this one change-likely meant to allow | | | | rotation. The component of imbalance |
| the ball to get a better grip on the | | | | along the rotation axis provides a |
| similar polyurethane varnishes used on | | | | leverage that can change the orientation |
| natural wood finish lane | | | | of the axis on its horizontal plane, an |
| surfaces-changed the nature of the | | | | action physicists call precession. It is |
| bowling game significantly, as never | | | | basically the same thing as a spinning |
| before. | | | | toy top "going around in a circle." In |
| Prior to about 1990, the USBC "static" | | | | the case of a rotating bowling ball, as |
| ball balance regulations were adequate. | | | | it moves along the lane, there is only |
| The core was usually a uniform sphere | | | | time for its total rotation axis to move |
| centered inside the ball. Then | | | | along a short arc, but this is enough to |
| competition among ball manufacturers | | | | reorient the total rotation so that some |
| motivated the production of balls | | | | of the forward-roll becomes side-roll, |
| designed to offer more than the "static | | | | increasing the side-roll provided in the |
| balance" tricks. Materials and | | | | bowler's delivery, thereby achieving |
| fabrication changes have since allowed | | | | more hook. It is possible to use dynamic |
| the assembly of balls whose interior | | | | ball balancing to achieve a stronger |
| components have a much greater range of | | | | gyroscopic effect than static balancing |
| density, thereby offering a new ball | | | | alone. |
| choice that, in physics terms, involves | | | | The advent of dynamic ball balancing |
| the moment of inertia of a solid sphere. | | | | meant that bowlers could achieve "ball |
| Eventually, "dynamic balance" | | | | flare" without the need for a 3/4 roller |
| regulations had to be adopted. | | | | delivery, and more hook. Additionally, |
| Weight Block Basics | | | | balls with covers that create higher |
| In order to continue this discussion, a | | | | friction, such as "particle" balls, |
| systematic description of ball rotation | | | | provide for more traction and hook. |
| must be introduced. For various | | | | Bowlers are embracing these choices, |
| formulaic purposes, physicists divide | | | | buying balls whose characteristics |
| rotation into three components, | | | | complement or enhance their deliveries. |
| assigning portions to x, y and z axes | | | | It is the opinion of many people in the |
| that are mutually perpendicular. For | | | | bowling community that these advances in |
| bowling, the x-axis can be assigned to a | | | | bowling ball technology have actually |
| line that is parallel to the foul line, | | | | undermined bowling skill and have made |
| the y-axis to the line parallel to the | | | | it more difficult for lane maintenance |
| boards, and the z-axis to the vertical. | | | | personnel to lay out fair and credible |
| Forward-roll is rotation about the | | | | conditions for participants. This is |
| x-axis, side-roll is rotation about the | | | | because advanced players using hi-tech |
| y-axis and mid-roll (or spin) is | | | | balls "need" more oil to score high and |
| rotation about the z-axis. The pure | | | | might complain about the radical |
| full-roller delivery is a combination of | | | | behavior of their balls on "dry" lanes. |
| forward- and side-roll only. | | | | At the same time, less aggressive |
| Semi-rollers include spin. Spinners may | | | | players might complain when they can't |
| have very little side roll. In a very | | | | get their balls to hook. These |
| strict physics sense, a ball may be | | | | complaints have actually been part of |
| delivered with rotation, but usually not | | | | the game throughout USBC history. It's |
| in a roll, because that would imply | | | | just been a matter of which group |
| complete traction. The technique of the | | | | prevails within the USBC - or what new |
| great majority of bowlers involves a | | | | technology comes along next. |