I've posted this on the BD CCB forum in the past, but I wanted to share it here also. Please let me know if you guys have any comments, suggestions, or questions.
Here's the question: How do you predict where the CB will go with different types of cut shots? My answers, including links with illustrations and examples, are below. Also, much more supporting info and links can also be found here:
http://billiards.colostate.edu/threads/30_and_90_degree_rule.html
Answers:
For a stun shot, most people know the right answer: in the tangent line direction, perpendicular to the OB direction. This is the 90-degree rule (see my Jan '04 article). If you want a more precise answer that accounts for various effects (e.g., friction and English), see my March-June '05 articles. FYI, here is a convenient one-page summary of the 90-degree rule.
For a rolling CB, the cue ball changes direction by about 30 degrees for a wide range of cut shots (1/4 to 3/4 ball hit). This is the 30 degree rule (see my April '04 article). If you want to be more precise, the angle is a little more (about 34 degrees) closer to a 1/2-ball hit and a little less (about 27 degrees) closer to a 1/4-ball or 3/4-ball hit. If you want to know how to account for speed effects, see my June '05 article. If you want an easy way to use your hand to accurately visualize the cue ball direction, use the Dr. Dave peace-sign technique (see NV 3.8). If you want to know how to precisely calibrate your hand for the 30 degree (or any other) angle, see using your hand to apply the rule. FYI, here is a convenient one-page summary of the 30-degree rule.
For a draw shot with good draw action, the trisect system is your answer (see my March '06 article). You can use a modified version of the peace-sign technique to predict the cue ball direction (see the article for illustrations and examples).
For shots "in between" all of these different cases, the cue ball will go somewhere in between the indicated directions. The only way to get a feel for how much "in between" the cue ball will go is to practice ... a lot!
Here's the question: How do you predict where the CB will go with different types of cut shots? My answers, including links with illustrations and examples, are below. Also, much more supporting info and links can also be found here:
http://billiards.colostate.edu/threads/30_and_90_degree_rule.html
Answers:
For a stun shot, most people know the right answer: in the tangent line direction, perpendicular to the OB direction. This is the 90-degree rule (see my Jan '04 article). If you want a more precise answer that accounts for various effects (e.g., friction and English), see my March-June '05 articles. FYI, here is a convenient one-page summary of the 90-degree rule.
For a rolling CB, the cue ball changes direction by about 30 degrees for a wide range of cut shots (1/4 to 3/4 ball hit). This is the 30 degree rule (see my April '04 article). If you want to be more precise, the angle is a little more (about 34 degrees) closer to a 1/2-ball hit and a little less (about 27 degrees) closer to a 1/4-ball or 3/4-ball hit. If you want to know how to account for speed effects, see my June '05 article. If you want an easy way to use your hand to accurately visualize the cue ball direction, use the Dr. Dave peace-sign technique (see NV 3.8). If you want to know how to precisely calibrate your hand for the 30 degree (or any other) angle, see using your hand to apply the rule. FYI, here is a convenient one-page summary of the 30-degree rule.
For a draw shot with good draw action, the trisect system is your answer (see my March '06 article). You can use a modified version of the peace-sign technique to predict the cue ball direction (see the article for illustrations and examples).
For shots "in between" all of these different cases, the cue ball will go somewhere in between the indicated directions. The only way to get a feel for how much "in between" the cue ball will go is to practice ... a lot!
