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Make Peace, Not War
The 30-Degree Rule can help you avoid obstacles and scratches and open clusters.
By "Dr. Dave" Alciatore
IF YOU don't know about the 30-degree rule, learning it can truly transform your game. Like the 90-degree rule - which predicts that a cue ball with stun (i.e., no top or bottom spin) will continue at a 90-degree angle from the object ball's direction - this principle helps you predict the path of a cue ball. Knowledge of the 30-degree rule will help immensely when you're planning to avoid obstacles, break open clusters, avoid scratches and plan carom and billiard shots.
The 30-degree rule states: When the cue ball hits an object ball with normal roll close to a half-ball hit, the cue ball will deflect approximately 30 degrees away from its initial aiming line (as shown in Diagram 1).
To be able to apply the 30-degree rule, you need to visualize an appropriate angle along which the cue ball will roll. For this, I've developed Dr. Dave's Peace Sign Technique. For most people, if you form a relaxed but firm "V" shape with your index finger and middle fingers (a "peace" or "victory" sign), the angle between your extended fingers will be very close to 30 degrees, as you can see in Diagram 2. If you point one of your fingers along the aiming line, the other finger will indicate the direction of the cue ball after impact. Just be sure to align the angle vertex point (where the lines of the two fingers meet) with the center of the ghost ball (the dotted-line ball in Diagram 1).
Avoid Obstacles: The 8-ball layout in Diagram 3 is a perfect example. You want to play position from the 1 to the 6 ball, going off the short rail. With natural roll, the cue ball will deflect to the left. With your peace sign, you know the cue ball will avoid the cluster of stripes, so you'll be in good shape to run out for the win.
Carom Shots: Both the 30-degree and 90-degree rules can be used to measure carom shots, where you deflect one ball (the cue ball or object ball) into another to make a shot. These shots can be difficult, but can be important weapons if you can predict the cue ball's path. In Diagram 4, you can see that a 30-degree hit on the 3 ball will send the cue ball straight into the 9 in the corner. This shot should be easy to make, as long as you the cue ball is rolling at impact with the 3.
Since 1978, Billiards Digest magazine has been the pool world’s best source for news, tournament coverage, player profiles, bold editorials, and advice on how to play pool. Our instructors include superstars Nick Varner and Jeanette Lee. Every issue features the pool accessories and equipment you love — pool cues, pool tables, instruction aids and more. Columnists Mike Shamos and R.A. Dyer examine legends like Willie Mosconi and Minnesota Fats, and dig deep into the histories of pool games like 8-ball, 9-ball and straight pool.
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