Bowling ball

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A ten-pin bowling ball and two pins.

A bowling ball is a round ball made from rubber, urethane, plastic, isinglass, reactive resin (solid, particle, or pearl), or a combination of these materials which is used in the sport of bowling. Ten-pin bowling balls generally have a set of three holes drilled in them, one each for the ring and middle finger, and one for the thumb; however, rules allow for up to five finger holes. A five-pin bowling ball has no finger holes and is smaller so that the bowler can hold the ball in the palm of their hand. Candlepin bowling balls also fit in the hand, but are lighter than five-pin balls.

Most bowling alleys provide free balls for patrons to use, called house balls, although avid bowlers may purchase their own. These are often customized, and can feature specially sized finger holes (in the case of ten-pin balls) or monograms. Because purchased balls are usually drilled to match the owner's fingers, most can throw a customized bowling ball that is one to two pounds heavier than the house ball they previously used.

Bowling balls come in many varieties of colors, and are often either a single flat color, a swirl-like design of multiple colors, or a single color with an iridescent look. It is even possible to obtain transparent bowling balls, painted in such a way as to make it appear as though an object is inside. Some objects have included skulls, footballs, and baseballs.

Inside the ball is a core which makes each ball do something different. These cores are dynamically imbalanced to cause the ball to try to stabilize as it is rolling down the lane.^[1] This makes the ball roll over a different point on the surface every time it revolves and "flares" or causes multiple oil rings.

Bowling ball cores are constructed with different densities as well. Some are center heavy (low rg) and some cores are made with the weight distributed more towards the cover of the ball (high rg). Low rg balls will spin more easily than the high rg balls.^[2]

[edit] Ten-pin balls

Two reactive resin bowling balls. Both are the same model, but one is pearlized (right) and one is not (left).

Regulation ten-pin bowling balls must weigh no more than 16 pounds (7.2 kg) (governing bodies do not regulate how light a bowling ball may be) and have a diameter of 8.5 inches (21.6 cm). The lightest ball generally available is the six pound weight, which is used mainly by children. Ball weights between 12 and 16 are common in adult league play. Since the physical size of regulation balls is the same, while the weight may differ, lighter balls are much less dense than heavier ones. Thus, balls under 10 pounds will actually float when placed in water.

The behavior of a rolling ball on a surface is controlled by several factors, the most obvious being the bowler's delivery. In the delivery, the bowler can advantageously use or fight (intentionally or unintentionally) the force of gravity. After the ball is on the surface of the lane, a complex interaction of friction, gyroscopic inertia, and gravity becomes a factor that can range from subtle to perhaps amazing. These environmental influences can be segregated as either lane conditions or ball characteristics. Additionally, a bowling ball is not an absolutely uniform sphere—the gripping holes (and sometimes a balance hole) alone make that impossible.

Bowling ball materials, during the history of the USBC, have evolved from wood, to rubber, to plastic, to urethane, to reactive urethane, to particle, and to epoxy. Wood balls are now just museum pieces. Rubber balls are almost as hard to find; however, they may be found offered to casual bowlers at bowling centers, from their racks for those who don't own their own ball. Bowling balls have been constructed with a core made of one material, a spherical coverstock ("cover" or "shell") and a "pancake" weight block of denser material intended to compensate for the gripping holes.

House balls laying on ball return.

One of the most contentious issues that has arisen is whether significant restrictions should be imposed on bowling ball technology. Other considerations have been noted with regards to the weight of the bowling pins, lane oiling techniques, and with the construction materials and techniques used to build bowling lanes.

[edit] Finger holes and grips

The way the finger holes are arranged on the ball surface changes the core dynamics; this will change how the bowling ball hooks down the lane.^[3]

There are only two different types of bowling grips for bowling balls: conventional, and finger tip, all other grips of any name (i.e., Sarge-Easter Grip and Semi finger tip) are derivatives of these two. In a conventional grip, the bowler's ring and middle fingers are placed into the ball up to the second joint, while in a finger tip grip the ring and middle finger holes are made to accept the bowler's fingers only up to the first joint. Semi-finger has the bowler put their fingers in an unhappy medium between conventional and finger tip. A finger tip grip requires more strength, but it allows the bowler much more control in how the ball rotates after it is released. For the players with extremely high rates of revolution ("rev rates") and skill level, a Sarge-Easter Grip may be an option. This is when the middle finger is drilled to finger tip depth, while the ring is drilled to the conventional depth. It allows players with high revs to change their axis tilt and allow more forward roll as to keep the ball from over hooking.^[4]

[edit] The history of the bowling ball

Bowling can be traced back to approximately 5200 B.C., when the ancient Egyptians used stones for their balls.

The first bowling balls used in the United States were made of wood, especially oak. In about 1906 the first hard rubber balls were produced, and these remained the standard until the 1960s and 70s. These decades saw the emergence of plastic (polyester) balls.

In the early 1970s, people began experimenting with the hardness of the plastic balls, notably PBA member Don McCune. McCune at the time worked for Chuck Hamilton who invented the "soaker" - a plastic (usually polyester} ball he softened "in the garage" with chemical solvents such as MEK, sometimes to the point that the balls might even end up lopsided. These and balls subsequently manufactured with the resulting softer cover came under USBC scrutiny because of the increased scoring. A ball hardness rule of 72 was established, based on durometer readings, which barred some of the softer balls.

At some point in ball making and drilling the USBC introduced ball balance regulations to prevent people from taking advantage. It was possible to drill the grip at a location relative to the weight block so that it would achieve some effect, such as to help the bowler make it roll earlier or hook more.

In 1981 Ebonite began manufacturing the very first polyurethane cover stock bowling balls and sold the rights to AMF. Ebonite did not believe that bowlers would pay the $80.00 price this new technology would demand. That ball became the AMF Angle and this one coverstock change allowed the ball to get a better grip on the polyurethane finishes used on natural wood lane surfaces which changed the nature of the bowling game significantly.

Prior to about 1990, the USBC "static" ball balance regulations were adequate. The core was usually a uniform sphere centered inside the ball. Then competition among ball manufacturers motivated the production of balls designed to offer more than the "static balance" tricks. Materials and fabrication changes have since allowed the assembly of balls whose interior components have a much greater range of density, thereby offering a new ball choice that, in physics terms, involves the moment of inertia of a solid sphere. Eventually, "dynamic balance" regulations had to be adopted.

In order to continue this discussion, a systematic description of ball rotation must be introduced. For various formulaic purposes, physicists divide rotation into three components, assigning portions to x, y and z axes that are mutually perpendicular. For bowling, the x-axis can be assigned to a line that is parallel to the foul line, the y-axis to the line parallel to the boards, and the z-axis to the vertical. Forward-roll is rotation about the x-axis, side-roll is rotation about the y-axis and mid-roll (or spin) is rotation about the z-axis. The pure full-roller delivery is a combination of forward- and side-roll only. Semi-rollers include spin. Spinners may have very little side roll. In a very strict physics sense, a ball may be delivered with rotation, but usually not in a roll, because that would imply complete traction. The technique of the great majority of bowlers involves a delivery that starts the ball in a skid that evolves into a roll that hooks into the pins.

It has been known since before the 1960s that a "full-roller" type of delivery does not hook as well as "3/4 rollers" on oily lanes. On successive rotations, the "full roller" repeatedly contacts the lane on the same full circumferential circle, on which the oil accumulates, making it harder for the side-roll to find traction and create hooking action. The "full-roller" had been the dominant choice before the changes in lane coatings and oil. The "semi-roller" is now preferred (it may also be called "3/4 roller" or by other slang terms). With a 3/4-roller a bowler puts the ball into a rotation whose contact ring is smaller, and on successive rotations enlarges (subsequent examination of the ball often shows a flaring of the circles of oil). This is because at every spot along the circle friction reduces the rotation, and that includes the spin component, causing rotation on a continually larger circle. This has the effect of bringing relatively dry ball surface in contact with the lane, increasing traction for both forward-roll and side-roll. It probably goes without saying why bowlers often wipe oil off the ball.

Another effect of ball imbalance (either static or dynamic) is the ability to introduce gyroscopic effects on the rotation. The component of imbalance along the rotation axis provides a leverage that can change the orientation of the axis on its horizontal plane, an action physicists call precession. It is basically the same thing as a spinning toy top "going around in a circle." In the case of a rotating bowling ball, as it moves along the lane, there is only time for its total rotation axis to move along a short arc, but this is enough to reorient the total rotation so that some of the forward-roll becomes side-roll, increasing the side-roll provided in the bowler's delivery, thereby achieving more hook. It is possible to use dynamic ball balancing to achieve a stronger gyroscopic effect than static balancing alone.

The advent of dynamic ball balancing meant that bowlers could achieve "ball flare" without the need for a 3/4 roller delivery, and more hook. Additionally, balls with covers that create higher friction, such as "particle" balls, provide for more traction and hook. Bowlers are embracing these choices, buying balls whose characteristics complement or enhance their deliveries.

It is the opinion of many people in the bowling community that these advances in bowling ball technology have actually undermined bowling skill and have made it more difficult for lane maintenance personnel to lay out fair and credible conditions for participants. This is because advanced players using hi-tech balls "need" more oil to score high and might complain about the radical behavior of their balls on "dry" lanes. At the same time, less aggressive players might complain when they can't get their balls to hook. These complaints have actually been part of the game throughout USBC history. It's just been a matter of which group prevails within the USBC - or what new technology comes along next.

[edit] Manufacturers of ten-pin bowling balls

• Ebonite International, which includes
  • Columbia 300 Industries
  • Hammer Bowling
  • Track International
  • Dyno-Thane (Overseas brand only)
• Brunswick Corporation
  • Quantum Bowling
  • Revolution Bowling (Overseas brand only)
  • MoRich Enterprises (contract made by Brunswick)
• Visionary Bowling Products
  • Insite Bowling (contract made by by Visionary)
  • Banger Bowling Ltd. (contract made by Visionary)
• Storm Bowling
  • Roto Grip
• 900 Global
  • AMF
• Lane Masters
  • Legends Bowling
• Lane #1 Bowling

[edit] Five-pin bowling balls

Five-pin bowling balls have no finger holes and are between 4.75 to 5 inches (12.1–12.7 cm) in diameter. They weigh between 3.25 and 3.625 pounds (1.47–1.64 kg). The smaller size and lighter weight of the balls allows bowlers to hold the ball in the palm of their hand when throwing.

[edit] Candlepin bowling balls

The maximum regulation candlepin ball weight is 2 pounds 7 ounces (1.105 kg), and with the regulated pin weight being only slightly heavier at 2 pounds 8 ounces (1.134 kg) the candlepin sport could be said to pose a greater challenge to the player—due to the almost non-existent difference of the weight between the ball and one candlepin—than any of the other forms of bowling that use ten pins in them.

[edit] References

1. ^ Core / Cover Stock Descriptions at bowlingball.com
2. ^ Bowling Ball Dynamics
3. ^ Ball Dynamics and Hook Potential at bowlingball.com
4. ^ Tips on the Grip at bowlingball.com