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dr_dave
11-30-2004, 03:25 PM
This is a new thread I am starting to allow people to ask questions concerning my monthly "Illustrated Principles" instructional articles. I will also use the thread to post questions I have received to date, along with my answers. FYI, all of my past articles are available on my website at:

www.engr.colostate.edu/pool (http://www.engr.colostate.edu/pool)

The website includes:
<ul type="square"> a large collection of online narrated video demonstrations, covering everything from the basics to advanced techniques.
super-slow-motion video clips, filmed with a special high frame-rate camera, that reveal principles that often can't be "seen" with the human eye or a normal video camera.
technical proofs of various dynamics principles based on physics-based mathematical analyses (probably of interest to only those with strong physics or engineering backgrounds).
instructional articles for learning the principles and techniques of pool and billiards.
online glossary of pool and billiards terms and lingo.
concise online summary of 8-ball and 9-ball rules.
links to other useful resources on the web.[/list]
I hope you find some of these resources useful. I plan to continue to expand and improve the website over time, so check back periodically to see new stuff.

Good luck with your game, and practice hard.

Tom_In_Cincy
11-30-2004, 06:20 PM
Dr. Dave,
I have enjoyed your articles published in Billiards Digests and appreciate all your efforts with videoing of the vast amounts of different shots. I have seen them used as references in different forums.

Keep up the good work.

woody_968
11-30-2004, 06:30 PM
Sounds great, Ill look forward to reading your articles.

Wally_in_Cincy
12-01-2004, 07:00 AM
dr_dave, your 3 recent articles on the 30 and 90 degree tangent lines have helped my cue ball control a lot. Well done.

PQQLK9
12-01-2004, 08:10 AM
Hello Dr Dave, I enjoy your work, thanks.

Fred Agnir
12-01-2004, 08:49 AM
Since I have no idea who you are, could you give us (me) some background? How long have you been playing pool? Are you an instructor? And most importantly, are you a forum member of RSB?

I would find it astonishing if anyone who has put in even a tenth (or less) of the effort you have at the science of the game is ... unknown to the RSB world.

Fred

dr_dave
12-01-2004, 09:57 AM
Thank you. It feels good to get positive feedback. Since my articles, book, and DVD have come out, I have received hundreds of supportive messages. I appreciate them all and they inspire me to continue working hard.

dr_dave
12-01-2004, 10:04 AM
Thank you. I have received many messages concerning these articles, mostly supportive. The 30 degree rule has also generated some controversy. Soon I will be posting a thread of questions (from readers) and answers to help address some of the confusion. I also plan to write another series of articles (to start in February, 2005) providing more information.

dr_dave
12-01-2004, 10:28 AM
I have a short bio posted on my pool website at:
www.engr.colostate.edu/pool/dr_dave.html (http://www.engr.colostate.edu/~dga/pool/dr_dave.html)

I have played pool and have been a student of the game my whole life, but mostly since 1982, when I graduated from high school.

I have dedicated much energy to pool over the last five years reading many books (about 20), creating my website, shooting lots of video, writing "The Illustrated Principles of Pool and Billiards," doing mathematical physics-based analyses, and writing articles for BD.

I look at rec.sport.billiard periodically but haven't participated due to time constraints. This BD discussion board is the first forum in which I have decided to be active, mostly because my articles appear in BD. Unfortunately, it is difficult to find time to read messages and be active in more than one forum.

I also have another pool book project planned, while trying to finish the 3rd edition of a textbook on mechatronics (electronics for mechanical engineers), so I don't anticipate having much free time over the next year.

Fred Agnir
12-01-2004, 10:50 AM
<blockquote><font class="small">Quote dr_dave:</font><hr>
I look at rec.sport.billiard periodically but haven't participated due to time constraints. This BD discussion board is the first forum in which I have decided to be active, mostly because my articles appear in BD. Unfortunately, it is difficult to find time to read messages and be active in more than one forum.
<hr /></blockquote>The reason why I mention it is because there has probably been more scientific discussion (and learning frankly) on the game of pool due to rec.sport.billiard than any other forum, website, or book, IMO.

There could have been some great mutual benefit if you had been a participant in the glory years of RSB.

Fred

silverbullet
12-01-2004, 11:38 PM
<blockquote><font class="small">Quote Fred Agnir:</font><hr> Since I have no idea who you are, could you give us (me) some background? How long have you been playing pool? Are you an instructor? And most importantly, are you a forum member of RSB?

I would find it astonishing if anyone who has put in even a tenth (or less) of the effort you have at the science of the game is ... unknown to the RSB world.

Fred <hr /></blockquote>

Quote from article on pocket size. "Before I begin, I want to make it clear that all pool tables are not created equal. Pocket size and shape can vary significantly with table size and manufacturer. Also, pockets can be shimmed (decreasing their size) to create more challenging conditions."

Not sure about this one. Fred, need clarification on this. We moved to a league that shoots on 9 ft double shims. I just thought that the pockets were smaller, until I visited another poolhall with identical sized pockets and then returned to the double shimmed ones. It seems that the double shim pockets are not smaller, but the radiant approach angle is steeper, so you do not get normal action that I got on the other pockets of identical size. No doubt the double shims require a dead aim.

So I need clarification on this statment because of the way it is stated.Note he did not say the double shims are 'tighter', but specifically stated smaller. Does the double shim decrease the actual pocket size or just decrease the approach gradient of the pocket facing?

Laura

Jimmy B
12-02-2004, 02:58 AM
<blockquote><font class="small">Quote Fred Agnir:</font><hr> And most importantly, are you a forum member of RSB?

Fred <hr /></blockquote>

Fred, what is RSB??
And this RSB World you speak of?

JB

DavidMorris
12-02-2004, 06:08 AM
<blockquote><font class="small">Quote Jimmy B:</font><hr>
Fred, what is RSB??
And this RSB World you speak of?

JB <hr /></blockquote>
That would be the rec.sport.billiard newsgroup. You can use Google Groups (http://groups-beta.google.com/group/rec.sport.billiard) to read and post there, but serious newsgroup junkies use an NNTP reader -- Outlook Express, Mozilla/Thunderbird, or Forte Agent for example all have newsgroup support.

catscradle
12-02-2004, 07:39 AM
<blockquote><font class="small">Quote Jimmy B:</font><hr> <blockquote><font class="small">Quote Fred Agnir:</font><hr> And most importantly, are you a forum member of RSB?

Fred <hr /></blockquote>

Fred, what is RSB??
And this RSB World you speak of?

JB <hr /></blockquote>

/ccboard/images/graemlins/grin.gif /ccboard/images/graemlins/grin.gif /ccboard/images/graemlins/grin.gif

dr_dave
12-02-2004, 09:08 AM
I have had many questions and comments from readers concerning the 30-degree rule. In this discussion thread, I will post Q&amp;A's that might be of interest to others.

dr_dave
12-02-2004, 09:09 AM
Does the 30-degree rule apply only for a half-ball hit?

dr_dave
12-02-2004, 09:21 AM
No. The whole point of the 30-degree rule, and the reason why it is so useful, is that it applies over a very large range of cut angles. As long as the cue ball is rolling (i.e., not sliding) at object ball impact, the cue ball's direction will be deflected by very close to 30 degrees for cut angles ranging from a 1/4-ball hit to a 3/4 ball hit.

For more information, see:
<ul type="square"> my April-June, 2004 articles posted at:
http://www.engr.colostate.edu/pool/bd_articles
pages 48-56 in my book "The Illustrated Principles of Pool and Billiards"
videos 3.9, 3.10, and 7.4 at http://www.engr.colostate.edu/pool/normal_videos[/list]

dr_dave
12-02-2004, 09:24 AM
Is the 30-degree rule exact? In other words, does the cue ball deflect at exactly 30 degrees?

dr_dave
12-02-2004, 09:34 AM
No, the 30-degree rule is not exact. For a half-ball hit, the deflected angle is actually about 34 degrees, and for 1/4- and 3/4-ball hits, the deflected angle is about 26 degrees. But the reason why the rule is so useful is that the deflected angle is still very close to 30 degrees over this very large range of cut angles from a fairly thin hit to a fairly full hit. Because of this, the rule applies to many (even most) shots and can be used to plan and predict cue ball motion for:
<ul type="square"> position play.
safeties
carom and billiard shots
break-up shots
avoidance shots
etc![/list]
For more information, refer to my articles, videos, and technical proofs concerning the 30-degree rule on my website and pages 48-56 in "The Illustrated Principles of Pool and Billiards."

dr_dave
12-02-2004, 09:38 AM
When does the 30 degree rule apply?

wolfdancer
12-02-2004, 09:43 AM
Laura, I have 4" corner pocket openings...a bit smaller then the recommended size, of 4 1/2 to 5....I've seen different face angles on tables, and different cutouts on the slates. sometimes a normal size pocket, with the slate extending deep into the opening, and the angles a tad off....will reject any hard hit ball, that bounces off the facing. We had a table at my old favorite pool hall,tight pockets, that would reject any ball hit hard along the rail....Ernesto just changed the angle of the facings. Another room had the big openings, wrong angles, and the ball would just ricochet , and sit in the jaws.
So, all tables are not created equal, bigger ain't necessarily better, as regards to pockets.....and them double-shimmed tables that your league now plays on....ain't going to affect your game that much...unless you let it. In fact you might find your game moving up a notch, because you are now trying to be more precise with your aim.
"radient approach angles" ????? what's that, are these tables giving off radiation?

dr_dave
12-02-2004, 09:47 AM
The 30 degree rule applies for any shot where the cue ball is rolling (i.e., not sliding) at object ball impact. Figure 3.21 on p. 52 of "The Illustrated Principles of Pool and Billiards" shows the most common cases. When the cue ball is very close to the object ball, rolling can occur only with a follow shot. For a medium distance between the cue ball and object ball, slow speed or a follow shot results in rolling. For a large distance shot, the cue ball will be rolling at object ball impact for almost any shot, except a power draw. In other words, the 30 degree rule applies for many types of shots.

For a good player executing good position control, leaving natural angles on all shots, the 30 degree rule applies for almost every shot!

wolfdancer
12-02-2004, 09:55 AM
I think it's a "commie" org..although it may be quasi-religious like the Rosicrucians.they got secret signs, secret handshakes,blood oaths, etc...so that they'll recognise each other in a pool hall. One of the ways they identify themselves, hoping to meet ilk, is to twirl the cuestick like a baton, while wearing a "Hawaiian" shirt

Barbara
12-02-2004, 10:09 AM
Why don't you post the question and the answer in the same post?!

Barbara

wolfdancer
12-02-2004, 10:35 AM
<font color="blue"> </font color> "Dude" ????
<font color="black"> </font color> How rude....

Barbara
12-02-2004, 10:39 AM
I didn't mean to be rude, I just think it would be more effective to post the Q &amp; A in the same post instead of separately. I read my posts in threaded mode so I would have go back to the previous post to see what the Q was.

Barbara

silverbullet
12-02-2004, 11:10 AM
<blockquote><font class="small">Quote wolfdancer:</font><hr>
So, all tables are not created equal, bigger ain't necessarily better, as regards to pockets.....and them double-shimmed tables that your league now plays on....ain't going to affect your game that much...unless you let it. In fact you might find your game moving up a notch, because you are now trying to be more precise with your aim.
"radient approach angles" ????? what's that, are these tables giving off radiation?
<hr /></blockquote>

Perhaps I used the wrong terminology. the rail angle going into the pocket is steeper preventing you from 'slopping in the ball'. We used to play on a league with 8fts, with similar size pockets. People complained about those because the league had moved from a PH with 9 ft gold crowns where the pockets were 'bread baskets'.

These pockets are not only smaller, but double shimmed. At first I played horrible on them, but now I am playing well on them, just had to work on getting my shooting more accurate. Since the 3s, 4s or whatever seemed so higher in skill then the other league, I had to get better. LOL.

Laura

Popcorn
12-02-2004, 11:18 AM
Out of curiosity, how will knowing all this stuff make me a better player? To me pool begins and ends with execution. In fact, most is played on the subconscious level. Once you start with all that messing with where to hit the ball or over thinking and conscious play you begin to dog it and your game wil go into the toilet. I can appreciate what you are trying to do, but much of it is a lot of unnecessary information in my opinion.

dr_dave
12-02-2004, 11:20 AM
Great suggestions. I'll do that for all future postings.

silverbullet
12-02-2004, 11:23 AM
<blockquote><font class="small">Quote dr_dave:</font><hr> No, the 30-degree rule is not exact. For a half-ball hit, the deflected angle is actually about 34 degrees, and for 1/4- and 3/4-ball hits, the deflected angle is about 26 degrees. But the reason why the rule is so useful is that the deflected angle is still very close to 30 degrees over this very large range of cut angles from a fairly thin hit to a fairly full hit. Because of this, the rule applies to many (even most) shots and can be used to plan and predict cue ball motion for:
<ul type="square"> position play.
safeties
carom and billiard shots
break-up shots
avoidance shots
etc![/list]
For more information, refer to my articles, videos, and technical proofs concerning the 30-degree rule on my website and pages 48-56 in "The Illustrated Principles of Pool and Billiards." <hr /></blockquote>

If your information is accurate, then it would be very useful. However, it does not exactly match up with what I read in the 'Science of pocket billiards' by jack koehler.But then jack talks about the 30 degree hit including variations depending on cb speed and distance between the balls. Oh geez. How am I supposed to know who is right???

There is a guy on az with phd in physics who is into this stuff, so guess I will have to ask him. /ccboard/images/graemlins/frown.gif

Laura

dr_dave
12-02-2004, 11:27 AM
Your point is well taken. Many players don't benefit from knowing and trying to apply principles. Also, nothing can beat intuition built from years of practice and success.

However, I think the 30 degree can dramatically improve the games of many people. This assumes that the player has good fundamentals and can make routine shots with ease. It is not worth thinking about position play and where the cue ball will go if one is going to miss easy shots.

Personally, the 30 degree rule helped bring my game to a new level. I am a much better player with the 30 degree rule than and was without it. I think this can be the case for others too.

dr_dave
12-02-2004, 11:44 AM
<blockquote><font class="small">Quote silverbullet:</font><hr>
If your information is accurate, then it would be very useful. However, it does not exactly match up with what I read in the 'Science of pocket billiards' by jack koehler.But then jack talks about the 30 degree hit including variations depending on cb speed and distance between the balls. Oh geez. How am I supposed to know who is right???

There is a guy on az with phd in physics who is into this stuff, so guess I will have to ask him. /ccboard/images/graemlins/frown.gif

Laura<hr /></blockquote>

The 30-degree rule is based on an analysis performed by two professors with PhDs in physics. If you want to see the detailed analysis, see TP 3.3 and the supporting technical paper on my website (www.engr.colostate.edu/pool (http://www.engr.colostate.edu/pool)).

Now, the exact path of the cue ball depends on shot speed. I will post a detailed discussion on this soon. Basically, the harder you hit the cue ball, the longer it persists along the tangent line (in the 90 degree direction), before it turns to the 30 degree direction, but the final deflected angle is still very close to 30 degrees for all rolling shots. For slow to medium speed shots, the cue ball deflects away from the tangent line in the 30 degree direction almost immediately. See my NV videos for demonstrations.

PS: At the risk of sounding defensive or conceited, FYI, I have a PhD in mechanical engineering and teach courses in advanced dynamics analysis, so I know a little about physics. I also back up most of the claims in my book and in my articles with video demonstrations, high-speed video, technical proofs, and intuition from experience. I hope you don't take offense at these statements ... that is not my intent.

SpiderMan
12-02-2004, 12:14 PM
<blockquote><font class="small">Quote Popcorn:</font><hr> Out of curiosity, how will knowing all this stuff make me a better player? To me pool begins and ends with execution. In fact, most is played on the subconscious level. Once you start with all that messing with where to hit the ball or over thinking and conscious play you begin to dog it and your game wil go into the toilet. I can appreciate what you are trying to do, but much of it is a lot of unnecessary information in my opinion. <hr /></blockquote>

Popcorn, you probably do know all this stuff, even if you don't write it down or try to quantify it, as it's become more intuitive for you. But I definitely benefit from consciously thinking about the physics while planning.

While I agree the best execution is intuitive, I think that an analytic understanding of the ball-ball interactions helps me to predict and (sometimes) control all of the balls that come into play during a shot. I don't have the benefit of thousands of hours of repetition, so I rely somewhat on quick analysis for tricky situations I haven't previously encountered. As I progress, more becomes intuition and less is analysis.

It's sort of like the process of learning to read - you can learn to piece together the syllables and sound it out, or you can call the whole words from your memory/experience. As your vocabulary increases, you do more of the latter and less of the former, but in your grasshopper stage the former does help you finish the book.

SpiderMan

wolfdancer
12-02-2004, 12:33 PM
Great reply...!!!!

wolfdancer
12-02-2004, 12:44 PM
See, the tighter pockets are actually helping your game....there's a point though of diminishing returns...we had a monthly member, a good player, that practised on a tight pocket table, and added pocket tighteners...there was no room for error...and he made about 1 out of 7 or 8 long shots...which was just negative feedback, imho...and since he couldn't also do anything with the cueball, while trying to make the shot..he was only practicing half of the game....hey, everybody can make shots, even those SL-3's in your league...not everybody can also get position for the next shot.
He did go on to beat Cory D. in one-pocket at Derby City...his 15 minutes of fame

silverbullet
12-02-2004, 12:56 PM
<blockquote><font class="small">Quote dr_dave:</font><hr>

The 30-degree rule is based on an analysis performed by two professors with PhDs in physics. If you want to see the detailed analysis, see TP 3.3 and the supporting technical paper on my website (www.engr.colostate.edu/pool (http://www.engr.colostate.edu/pool)).

Now, the exact path of the cue ball depends on shot speed. I will post a detailed discussion on this soon. Basically, the harder you hit the cue ball, the longer it persists along the tangent line (in the 90 degree direction), before it turns to the 30 degree direction, but the final deflected angle is still very close to 30 degrees for all rolling shots. For slow to medium speed shots, the cue ball deflects away from the tangent line in the 30 degree direction almost immediately. See my NV videos for demonstrations.

PS: At the risk of sounding defensive or conceited, FYI, I have a PhD in mechanical engineering and teach courses in advanced dynamics analysis, so I know a little about physics. I also back up most of the claims in my book and in my articles with video demonstrations, high-speed video, technical proofs, and intuition from experience. I hope you don't take offense at these statements ... that is not my intent. <hr /></blockquote>

No.Two years ago, when I first got on the forums, I believed everything. But I have seen enough books, etc, on the market,some of which sell many copies a year, yet are filled with inaccuracies, to have become a skeptic. So thanks for your answer. Without mentioning any names, I called a certain person who knows you and says you are ok and seemed up front.

Intuitively, the cb does seem to usually come off at the angle you state, when hit soft, with no side and either centerball, or a little top, but very little bottom, which I use for shape, safe etc, but like popcorn, I did not get that from a book LOL

Laura

dr_dave
12-02-2004, 01:21 PM
Q: What is the effect of speed on the 30 degree rule?

First, remember that the 30 degree rule applies only when the cue ball is rolling at object ball impact. For example, it does not apply for a stun shot (where the 90 degree rule applies) or for a draw shot (where the final deflected angle of the cue ball depends significantly on the amount of bottom spin).

Concerning speed, the harder you hit the cue ball, the longer it persists along the tangent line (in the 90 degree direction), before it turns to the 30 degree direction. However, the final deflected angle is still very close to 30 degrees. For slow to medium speed shots, the cue ball deflects away from the tangent line in the 30 degree direction almost immediately.

For more information, see Section 4.07 ("Controlling the Cue Ball Path") in "The Illustrated Principles of Pool and Billiards" (pp. 115-123), especially Figure 4.41 on p. 120. Also, I will be writing a series of follow-up articles on the 30 and 90 degree rules in Billiards Digest. They should appear in the magazine starting in February, 2005.

dr_dave
12-02-2004, 01:39 PM
Q (from a BD reader):
I was noticing that if you look at the 90 degree rule in the same way as the 30 degree rule, -- that is, measuring from the aim line to the deflected path...the 90 degree rule could actually be called a 45 degree rule. (I realize the traditional "tangent line" discussion is the 90 degree rule.)

The 90 degree rule looks at deflection path vs Object path but if you look at it as aim line vs deflection it is 45 degrees (for that 1/4 to 3/4 ball cuts range...)

Just thought I would mention that. Seems to me if both rules are presented with the same "point of reference"...the aim line, they might be easier to remember......


A (from me):
Thank you for your message and for your insights. I wish what you propose would work in every case, but unfortunately it does not. The 90 degree rule predicts a 45 degree cue ball deflection only for a cut angle close to 45 degrees (for a ball-hit fraction close to 0.3). For a very small cut-angle (a near full hit) stun shot, the deflected angle is close to 90 degrees. And for a very thin cut (near zero ball-hit fraction), the deflected angle is close to zero (i.e., the cue ball path deflects very little). In fact, for every cut angle, including those in the 1/4 and 3/4 ball-hit range, the deflected cue ball angle is different; but the angle between the deflected cue ball and object ball paths is always 90 degrees (for a stun shot only). I hope that makes sense.

For more information, see my January-July, 2004 articles at www.engr.colostate.edu/pool/bd_articles (http://www.engr.colostate.edu/pool/bd_articles) and pages 41-56 in "The Illustrated Principles of Pool and Billiards," especially Figure 3.10 on p. 42 and Figure 3.17 on p. 50.

nAz
12-02-2004, 01:50 PM
Dr. Dave glad to see your posting here, I have been a big fan of your work ever since i read an article on you in BD last year.
BD (http://www.billiardsdigest.com/ccboard/showflat.php?Cat=&amp;Board=ccb&amp;Number=116496&amp;Forum=Al l_Forums&amp;Words=Principles%20of%20Pool%20&amp;Match=Ent ire%20Phrase&amp;Searchpage=0&amp;Limit=25&amp;Old=allposts&amp;Ma in=116496&amp;Search=true#Post116496)


On shot HSV A.4 - 9-ball power break with follow and Draw (close-up, side view) was the cue ball directly behind the head string or was it off to a side?

BTW I love this particular HSV you can really see how the 1B bounceaway from the rack when shot with follow and how it spin back into the rack when it is shot with draw. Great job dude!

dr_dave
12-02-2004, 01:54 PM
Q (from a BD reader):
Physicist that I have talked to say the 90 degree rule applies on every shot. In other words, the cue ball always leaves along the tangent line, perpendicular to the direction of the object ball. I think your 30 degree rule violates the laws of physics.

A (from me):
Your physicist friends are partly correct. The cue ball does start out in the tangent line direction after impact with the object ball. However, topspin (e.g., from forward roll or a follow shot) or bottom spin (e.g., from a draw shot) start taking effect immediately. For high speed shots, the cue ball persists along the tangent line longer before the path curves. However, for slow to medium speed shots, the cue ball curves away from the tangent line very quickly. If you're not convinced, see the video demonstrations of the 30 degree rule (NV 3.8, 3.9, 3.10, and 7.4) on my website.

Concerning the 30 degree rule violating the laws of physics, I know of two physics professors that would take offense at that statement. They prove the basis of the rule mathematically with valid physical principles (see TP 3.3 and the supporting paper on my website for more information). They also back up their claims with photographic evidence.

dr_dave
12-02-2004, 02:00 PM
<blockquote><font class="small">Quote nAz:</font><hr> Dr. Dave glad to see your posting here, I have been a big fan of your work ever since i read an article on you in BD last year.
BD (http://www.billiardsdigest.com/ccboard/showflat.php?Cat=&amp;Board=ccb&amp;Number=116496&amp;Forum=Al l_Forums&amp;Words=Principles%20of%20Pool%20&amp;Match=Ent ire%20Phrase&amp;Searchpage=0&amp;Limit=25&amp;Old=allposts&amp;Ma in=116496&amp;Search=true#Post116496)
<hr /></blockquote>
Thank you very much. Ever since my website and book have been released, I have been flooded by many positive (and sometimes negative) statements. They are all very flattering.:o


<blockquote><font class="small">Quote nAz:</font><hr> On shot HSV A.4 - 9-ball power break with follow and Draw (close-up, side view) was the cue ball directly behind the head string or was it off to a side?

BTW I love this particular HSV you can really see how the 1B bounceaway from the rack when shot with follow and how it spin back into the rack when it is shot with draw. Great job dude! <hr /></blockquote>

On this shot, I had the cue ball on the head spot in the center of the headstring. However, I'm not sure if I hit the 1-ball perfectly squarely. That's what I was attempting to do ... I think a came fairly close.

Popcorn
12-02-2004, 02:20 PM
This is going to sound like an insult to whoever chooses to take it that way but, when ever I run into someone who refers to themselves as a student of the game, they can't play. They spend so much time trying to discover some secret that will turn on a light that they remain a perpetual beginners never really developing a game. I know guys that have been playing for years and every week or so they come over with," I just discovered I haven't been positioning my feet correctly". The next week they are gripping their cue differently and it never ends. Good fundamentals and good practice habits will do the most for a player. You learn what the balls do by observing and developing the muscle memory and feeling to reproduce the required action. You get a feel for it as you play. You need an understanding what you are trying to accomplish but there is no need to over complicate something that is not that complicated in the first place. Pool is not that hard to play, there is a lot of repetition. Most of the time you are just doing general things you have done hundreds of times before. Just my opinion

Bob_Jewett
12-02-2004, 03:14 PM
<blockquote><font class="small">Quote Popcorn:</font><hr> Out of curiosity, how will knowing all this stuff make me a better player?... much of it is a lot of unnecessary information in my opinion. <hr /></blockquote>
I think that for many players, the information is of little use. This includes very experienced players who have subconsciously learned things like the half-ball carom angle as well as beginners who just don't understand abstract descriptions of physical systems.

But I think that for many beginners understanding the simple physical relationships can speed up the learning process. For example, I had a student the other day who practices frequently and plays on one or two league teams but was totally unaware of the 90-degree (initial carom path) rule. I think that knowing that rule will help him immediately to plan position shots.

Fred Agnir
12-02-2004, 03:51 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> The 30-degree rule is based on an analysis performed by two professors with PhDs in physics. If you want to see the detailed analysis, see TP 3.3 and the supporting technical paper on my website (www.engr.colostate.edu/pool (http://www.engr.colostate.edu/pool)).
<hr /></blockquote>

How do your answers compare to the graphs and analysis on APAPP?

Fred

dr_dave
12-02-2004, 04:19 PM
<blockquote><font class="small">Quote Fred Agnir:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> The 30-degree rule is based on an analysis performed by two professors with PhDs in physics. If you want to see the detailed analysis, see TP 3.3 and the supporting technical paper on my website (www.engr.colostate.edu/pool (http://www.engr.colostate.edu/pool)).
<hr /></blockquote>

How do your answers compare to the graphs and analysis on APAPP?

Fred <hr /></blockquote>

I'm not sure to what pages, problems, or sections you are referring; but if Ron Shepard includes similar analyses in his document, I would expect them to be valid and agree with the work I cited. All of Ron's work is thorough, with all I's dotted and all T's crossed.

Popcorn
12-02-2004, 06:53 PM
For the sake of discussion, I looked at some of your shots. In 7.10 what are you trying to illustrate. The shot is a hanger yet you double kiss the ball. If you had hit it where you say you will you would make the ball. From where the cue ball goes it is clear you hit the ball almost straight on intentionally double kissing. I don't get it.

wolfdancer
12-02-2004, 07:09 PM
Point taken!!!
I used to see the same thing on the golf course when I was playing 3 or four times a week.
But, I don't think the articles are aimed at advanced players like you, Fred, or anybody else trying to question their value. As Bob Jewett states, not everyone knows the fundamentals, to build their game on.
I guess I better hide my Robert Byrne book, where he wrote on the inside cover "To a fellow student of the game"
No wonder he fled the Bay Area for Iowa.....after making that self-effacing statement.

silverbullet
12-02-2004, 07:25 PM
<blockquote><font class="small">Quote Popcorn:</font><hr> This is going to sound like an insult to whoever chooses to take it that way but, when ever I run into someone who refers to themselves as a student of the game, they can't play. They spend so much time trying to discover some secret that will turn on a light that they remain a perpetual beginners never really developing a game. I know guys that have been playing for years and every week or so they come over with," I just discovered I haven't been positioning my feet correctly". The next week they are gripping their cue differently and it never ends. Just my opinion <hr /></blockquote>

I see this a lot, especially in players who have played a long time and think that they 'should' be better. You are right, it is something new every week. I just do not understand this. Unless someone points out something obviously wrong with my fundamentals, I am not changing the way I hold ,etc, expecting to jump 3 levels over night.. Within my first year of playing, I started calling these 'quick fixes'. They never did anything long term because there are no quick fixes. I know what my deficencies are what I need to work on, and it will take time and experience. There is no substitute for that.

For some reason, lots of folks that play pool need to call themselves something like student, lover of the game, player etc. Don't really get it. I tell people I like to play pool, without specifying what that means and if they want to know how long I have played, I tell them, end of discussion.

Laura

Popcorn
12-02-2004, 07:32 PM
Post deleted by Popcorn

wolfdancer
12-02-2004, 07:46 PM
He used to play at Palace Billiards in SF, and later on,at the Q Club, but not too often. He was "knocked" as a pool player, but a decent Billiards player, which was his game of choice....nice guy to talk to, and his video was the onset of quality instructional tapes...proved that they could be marketable.

dr_dave
12-03-2004, 08:23 AM
<blockquote><font class="small">Quote Popcorn:</font><hr> For the sake of discussion, I looked at some of your shots. In 7.10 what are you trying to illustrate. The shot is a hanger yet you double kiss the ball. If you had hit it where you say you will you would make the ball. From where the cue ball goes it is clear you hit the ball almost straight on intentionally double kissing. I don't get it. <hr /></blockquote>
The only point of that clip is to show a frozen-rail bank-shot double-kiss and its effect on the rebound angle off the rail. Several clips on the website are there just to provide a visual for something I discus in the book (where the clips are referenced, described, and illustrated in detail).

dr_dave
12-03-2004, 11:11 AM
Q (from a BD reader):
How can a train my hand to take the 30 degree shape you show in your videos?

A (from me):
I used a plastic 30-60-90 triangle (see NV 3.8 on my website) to practice to the point where I can form a 30 degree "V" sign with my hand very consistently. For most people, a firm "V" ("peace") sign is very close to 30 degrees, but it is still good to practice. You can purchase a drafting triangle at any arts supplies store or college bookstore. You can also make your own by cutting one out of cardboard or paper (see Figure 3.24 on p. 54 of "The Illustrated Principles of Pool and Billiards"). To cut one out, use the following dimensions:

triangle width = 1 foot (alternatively: 30 cm)
triangle height = 7 inches (alternatively: 17 cm)

Those dimensions result in a triangle with a 30 degree angle (or close enough for application of the 30 degree rule, which is not perfectly exact anyway).

dr_dave
12-03-2004, 11:41 AM
Q (from a BD reader):
First I would just like to say that I think that you videos online are extremely helpful and I would like to thank you for helping improve my game. My question is though; in the clips of Chapter 6, you mention the equal distant bank method, but when you say you are 4 diamonds away from the target pocket, it appears that you are not even parallel to a side pocket. I didn't know whether it was the tangent line farthest from the object ball on the cue ball that you refer to as being said diamonds away or not or maybe it is just the camera angle or not. Any help you could give I would really appreciate. Thank you very much for you time.

A (from me):
Thank you for your feedback.

Concerning your question; fortunately, the answer happens to be included in the sample pages from my book posted on my website. If you want to check it out, go to the website (http://www.engr.colostate.edu/pool), click on "book" and then "sample pages", you will find a detailed explanation on the last two pages.

Good luck with your game!

dr_dave
12-03-2004, 02:25 PM
Q (from a BD reader):
With respect to spin-induced throw (SIT), I have been teaching this phenomenon &amp; its use (a la Science of Pocket Billiards) for years. Recently, I've been told that the physics jockeys are now saying that no, while SIT may indeed be possible, it is too small an effect to use. Their "practical proof" is the following experiment: draw a line on the cloth (for example, a few feet on the long string), place a CB &amp; OB on the line, shoot the CB at the OB with sidespin, aiming to hit the OB full on. What one finds, doing this, is you can't get the CB to stay on the line while having the OB throw off the line.

So, this is very interesting, and sure enough, I couldn't demonstrate throw in the experiment. But, the old SIT hypothesis does indeed explain &amp; predict the types of results we get on the table, so while that model is at useful, I'd really like to know whether it is correct. They tell me what's really happening is simply that the CB is curving to the OB contact point that results in the line taken by the OB, giving the appearance that SIT is real.

A (from me):
SIT is definitely a real effect. Like cut-induced (collision-induced) throw, it is due to sideways friction force caused by relative sideways motion between the CB and OB during impact. NV 4.15, 4.16, 7.5, and 7.6 on my website (http://www.engr.colostate.edu/pool) show examples of various types of throw. The reason the CB does not remain on the impact line for a direct hit on the OB is because when the CB throws the OB in one direction, the OB pushes back on the CB in the opposite direction, which throws the CB off the impact line. This is a result of Isaac Newton's Third Law of Motion (for every action there is an equal and opposite reaction).

Throw, resulting from CB English or cut angle, is most definitely real (and sometimes very useful)! It also must be accounted for at times; if not, you will sometimes miss what appear to be easy shots.

For more information, see pages 101-114 in "The Illustrated Principles of Pool and Billiards."

dr_dave
12-03-2004, 02:31 PM
Q (from a BD reader):
Does English deflection (squirt) change with ball speed?

A (from me):
I've done some experiments and have posted a video to show the results. See NV A.17 on my website (http://www.engr.colostate.edu/pool/). Deflection (squirt) at high speed was about 3 times larger than deflection at low speeds. The deflection at low speed is small, but it is not zero. Practically speaking though, slow speed side-English shots would typically only be used for fairly short shots where deflection would not be of much concern (especially compared to English throw, which could be a major concern).

The next time I get access to the high-speed camera, I will try to shoot some video to help shed more light on the underlying physics of deflection (squirt).

dr_dave
12-03-2004, 02:41 PM
Q (from a BD reader):
The double bank-carom shot on page:
www.engr.colostate.edu/pool/normal_videos/new/NVA-14.htm (http://www.engr.colostate.edu/~dga/pool/normal_videos/new/NVA-14.htm)
seems to be explained wrongly, you say you bank the 2 ball, then carom it off the 7 into the RAIL THEN carom of the 5 into the corner pocket, but if my eyes don't deceive me, you carom the 2 ball of 7 into the 5 ball directly, it doesn't touch the end rail in between.

A (from me):
Thanks for pointing this out. You are absolutely correct. I wasn't aware of it until after I finished filming. I show both versions of the shot in my October, 2004 article at: www.engr.colostate.edu/pool/bd_articles/oct04.pdf (http://www.engr.colostate.edu/~dga/pool/bd_articles/oct04.pdf)

Ross
12-03-2004, 03:04 PM
Welcome to the board Dave. I've been following your website for awhile and have been very impressed. I also bought your book recently. Almost all of the info has been discussed on RSB over the years but no one has organized and presented the information so effectively in one place. The accompanying videos are a particularly nice touch since they both illustrate and verify the principles you are discussing. Nice work!

And to those posters that aren't analytical by nature, remember that no one is claiming that this knowledge is what makes a person a top player. We all understand that all of the great players learned by watching and by experience, not from a book. But some of us just enjoy learning the principles behind things and know that sometimes understanding the principles will save you from having to hit the ball a billion times to get that pro-level "feel". And for lower level players this kind of knowledge will speed up the process of learning cue ball control considerably. I remember years ago my game going up a ball or so quickly after Jerry Brieseth taught me the tangent rule and showed how it could really be applied to real life 9-ball layouts.

So Dave, I look forward to your continuing contributions to this board.

dr_dave
12-03-2004, 03:24 PM
<blockquote><font class="small">Quote Ross:</font><hr> Welcome to the board Dave. I've been following your website for awhile and have been very impressed. I also bought your book recently. Almost all of the info has been discussed on RSB over the years but no one has organized and presented the information so effectively in one place. The accompanying videos are a particularly nice touch since they both illustrate and verify the principles you are discussing. Nice work!<hr /></blockquote>
Thank you so much for your flattering and supportive remarks. It feels good to be appreciated.

<blockquote><font class="small">Quote Ross:</font><hr>
And to those posters that aren't analytical by nature, remember that no one is claiming that this knowledge is what makes a person a top player. We all understand that all of the great players learned by watching and by experience, not from a book. But some of us just enjoy learning the principles behind things and know that sometimes understanding the principles will save you from having to hit the ball a billion times to get that pro-level "feel". And for lower level players this kind of knowledge will speed up the process of learning cue ball control considerably. I remember years ago my game going up a ball or so quickly after Jerry Brieseth taught me the tangent rule and showed how it could really be applied to real life 9-ball layouts. <hr /></blockquote>
Thank you for these insightful remarks. I hope others agree.

<blockquote><font class="small">Quote Ross:</font><hr>
So Dave, I look forward to your continuing contributions to this board.<hr /></blockquote>
Me too. Thanks again! /ccboard/images/graemlins/smile.gif

Ross
12-03-2004, 04:31 PM
Dave, I don't think you can tell the speed/squirt relationship from your video for a couple of reasons. One is you are not subtracting out the effects of cb curve, which is greater at slower speeds and which works in the opposite direction to squirt. So what appears to be less squirt at slow speeds may be just the effect of the cb curving back on line more. An overhead shot on a precisely marked table would help determine if that is the case.

The second problem with your experiment is that it does not ensure that you are hitting the cb each time at the exact same sideways offset (or vertical axis either). If unconsciously you tend to hit the cb with a mm more side english when stroking hard than when stroking softly, this could explain most of the effects you see.

One way to check for this would be to look at the angle that the cb comes off the rail, but that only works if cb speed is kept constant. And I don't know enough physics to know how you could predict the rebound angles for a constant "amount of english" but differing cb speeds.

So I remain unconvinced that there is more squirt at higher speeds. You definitely have to compensate more at faster speeds but that may be due to reduced swerve effects and not increased squirt.

dr_dave
12-04-2004, 12:04 PM
<blockquote><font class="small">Quote Ross:</font><hr> Dave, I don't think you can tell the speed/squirt relationship from your video for a couple of reasons. One is you are not subtracting out the effects of cb curve, which is greater at slower speeds and which works in the opposite direction to squirt. So what appears to be less squirt at slow speeds may be just the effect of the cb curving back on line more. An overhead shot on a precisely marked table would help determine if that is the case.
<hr /></blockquote>

I doubt there is any significant curve (swerve) in the shots in my video. My cue stick was nearly horizontal and I hit through the cue ball horizontal plane on every shot. My actual cue stick elevation was only about 1.4 degrees per my measurements and analysis TP A.3 on my website (http://www.engr.colostate.edu/pool). Also, any curve (if there was any) was too small to observe, at any speed. This is difficult to prove from the low resolution video posted, but it was clear in person. Try the experiment yourself and let me know if you observe any curve.

<blockquote><font class="small">Quote Ross:</font><hr> The second problem with your experiment is that it does not ensure that you are hitting the cb each time at the exact same sideways offset (or vertical axis either). If unconsciously you tend to hit the cb with a mm more side english when stroking hard than when stroking softly, this could explain most of the effects you see.
<hr /></blockquote>

You are correct. I am not a machine and I am not able to guarantee a perfectly consistent stroke. However, by observing my follow-through (on the video) and the chalk mark on the cue ball after every shot, I assure you that my stroke was fairly consistent for every shot I included on the video. I actually executed many more shots than I included in the final version. I threw out all shots that were not consistent, due to direction of follow-through or chalk mark placement. Bottom line: I stand by my consistency, although I admit it might not have been perfect.

<blockquote><font class="small">Quote Ross:</font><hr> So I remain unconvinced that there is more squirt at higher speeds. You definitely have to compensate more at faster speeds but that may be due to reduced swerve effects and not increased squirt.
<hr /></blockquote>

Regardless of what we think and how we explain it, the effective "squirt" is larger at higher speed and it must be accounted for.

Rod
12-04-2004, 01:42 PM
I agree there Dr. Dave. The effect of swerve wonít really be a factor. Swerve needs an elevated cue at slower speeds, or a downward type stroke with side english. Itís very, very, tiny, minute effect, if any is immeasurable. Far more important is the quality of your stroke.

As an example I set up two balls to shoot between. They are 3/8Ē to each side of the c/b on the end rail. Some will need to set these balls farther apart, at least in the beginning. I set them slightly less, about 5/16Ē. Use the c/b on the end rail as a guide. This gives a person a clue how much there shaft squirts, quality of stroke, and how it affects aim. Really you should be able to drive a truck through there but for most it will be a toy truck. LOL

With no english at any speed it should be simple. Add English and speed, the target becomes much smaller for most.
An example of what should happen if you clear both balls at a very firm speed loaded with right English.
Wei Table (http://endeavor.med.nyu.edu/~wei/pool/) START(
%AC7Q0%BC7M9%Pg6O5%WW5E4%XC7O4%]D8O7%^g1O7%eC7a4

)END

If the c/b doesn't hit in this area and goes a lot longer then little or less right was used. If it hits well short, the speed was to slow. I think it's worth a note, the less English the more accurate.

Which brings me to -- How much does varying amounts of side English only, and at different speeds, effect squirt? I could be wrong but Iím saying amount of english has near or as much effect as speed.

Not that we really need to know all of this stuff because every player needs to know their stroke and equipment, thatís how we develop consistency. Knowing is fine but I doubt it would make a pimple on flyís butt. Itís curiosity more than anything because overanalyzing causes many players to fault an area when itís not even a factor.

Rod

dr_dave
12-04-2004, 01:47 PM
I've created a separate thread (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&amp;Board=ccb&amp;Number=168242&amp;page =0&amp;view=collapsed&amp;sb=5&amp;o=&amp;fpart=1) for this item and I will post your replay there, with my response.

Thanks.

dr_dave
12-04-2004, 02:10 PM
I have moved this discussion to a new thread (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&amp;Board=ccb&amp;Number=168248&amp;page =0&amp;view=collapsed&amp;sb=5&amp;o=&amp;fpart=1). Please go there instead.

Stretch
12-04-2004, 02:42 PM
<blockquote><font class="small">Quote silverbullet:</font><hr> <blockquote><font class="small">Quote Popcorn:</font><hr> This is going to sound like an insult to whoever chooses to take it that way but, when ever I run into someone who refers to themselves as a student of the game, they can't play. They spend so much time trying to discover some secret that will turn on a light that they remain a perpetual beginners never really developing a game. I know guys that have been playing for years and every week or so they come over with," I just discovered I haven't been positioning my feet correctly". The next week they are gripping their cue differently and it never ends. Just my opinion <hr /></blockquote>

I see this a lot, especially in players who have played a long time and think that they 'should' be better. You are right, it is something new every week. I just do not understand this. Unless someone points out something obviously wrong with my fundamentals, I am not changing the way I hold ,etc, expecting to jump 3 levels over night.. Within my first year of playing, I started calling these 'quick fixes'. They never did anything long term because there are no quick fixes. I know what my deficencies are what I need to work on, and it will take time and experience. There is no substitute for that.

For some reason, lots of folks that play pool need to call themselves something like student, lover of the game, player etc. Don't really get it. I tell people I like to play pool, without specifying what that means and if they want to know how long I have played, I tell them, end of discussion.

Laura


<hr /></blockquote>

To begin with, i do concider myself a student and no, i don't feel insulted by Popcorns (or anyone else's) contention that "students" don't have game. Even pro's play around constantly with thier stroke , stance, fundamentles, well everything. The big difference is developing players tend to spend "all" their practice time trying to break the stroke down into it's component parts, trying new grips, working on this, working on that. Then when they get into a game they "think" mechanicly. This is what kills a persons "game" more than anything else. In competition you don't make things happen, you let them happen. Big difference.

But here's the trap. Knowone knows just how long it takes to change something with the view of improveing on what you have. It would depend on how well you practice it, and how ingrained your bad habit was. Generaly speeking, when you can switch to your trusting mind and play the game without thinking about the change you've made, your ready for action. The problem is that most amatures are flooded with information that they try and work on, but they still want to play in the monday night league, or the weekend tournament before what they've been working on is "ingrained". So then after an intial spike in improvement they eventually revert to what they've been doing all along and are right back at square one.

A "good" pool player seeks help a little differently. When he/she seeks advice on something they might get 10 or twenty sugestions and mentaly say Nope, Nope, Nope, that's not it. Then one of those things they will intinctivly say YES this will help my game, and proceed to incorporate it. but only after it was worked on to the point where he could trust it without thinking about it. So there it is. Only bite off what you can chew! It bogles my mind how anyone can say go to a Pool School (sorry you teachers) and get bombarded with 15 million things and think it's going to make them better. You need to tackle improvement one thing at a time and have a long range plan. St. ~student for life~

Fred Agnir
12-04-2004, 03:18 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> Q (from a BD reader):
How can a train my hand to take the 30 degree shape you show in your videos?

A (from me):
I used a plastic 30-60-90 triangle (see NV 3.8 on my website) to practice to the point where I can form a 30 degree "V" sign with my hand very consistently. For most people, a firm "V" ("peace") sign is very close to 30 degrees, but it is still good to practice. <hr /></blockquote>Dave, there are diamonds on the rails that might be a little easier to use to make a 30 degree angle.

Fred

Fred Agnir
12-04-2004, 03:26 PM
<blockquote><font class="small">Quote dr_dave:</font><hr>
I doubt there is any significant curve (swerve) in the shots in my video. My cue stick was nearly horizontal and I hit through the cue ball horizontal plane on every shot. <hr /></blockquote>
I think that this is a mistake to dismiss the effects of swerve. It's a greater effect than most people ever consider.

[ QUOTE ]
My actual cue stick elevation was only about 1.4 degrees per my measurements and analysis
<hr /></blockquote>1.4 degrees? Maybe I need to see the shot in question, in order to clear the cushion, aren't you at a minimum 2 degrees? And most people want their fingers to clear the cushion, so that might add more. How did you hit that shot? Were you leaned out over the table so that the cue stick was nearly flat? How could you guarantee repeatability?

Fred

Fred Agnir
12-04-2004, 03:32 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote Popcorn:</font><hr> For the sake of discussion, I looked at some of your shots. In 7.10 what are you trying to illustrate. The shot is a hanger yet you double kiss the ball. If you had hit it where you say you will you would make the ball. From where the cue ball goes it is clear you hit the ball almost straight on intentionally double kissing. I don't get it. <hr /></blockquote>
The only point of that clip is to show a frozen-rail bank-shot double-kiss and its effect on the rebound angle off the rail. Several clips on the website are there just to provide a visual for something I discus in the book (where the clips are referenced, described, and illustrated in detail).
<hr /></blockquote>But you've mislead the viewer. I think it's a valid question. You showed where you were going to hit it, then you shot somewhere completely different. Isn't there a poor message that you are conveying to a hopefull banker that he somehow will double-kiss this "shallow angle" bank shot, where in fact, it looks like you'd probably make it with ease if you shot where you said you were going to.

Fred

Popcorn
12-04-2004, 03:37 PM
You said what I was trying to say a little better then I did. Another problem is not having confidence in what you know. If a player goes into a slump, the worst thing they can do is changing everything thinking it will get better. If it worked before it will work again and changes may not help but just wreck your game. Now here is the rub. There is always something that may be able to be changed with a positive result. Something that could take you to the next level. I believe this is where an instructor may be of help. All things being equal though, the greatest tool and short cut to improvement is competition with better players. Like a child learns from emulating, so do adults on a subcsinious level.

It never fails, let a player start playing in a room with better players or playing tournaments and if he comes back to his old room he is amazingly a much better player, often in a very short time. That is also a little what I was talking in regards to the chronic practicer, (Student), who never competes, they don't really seem to get any better. If you go to some of the small tours such as the Joss tour or some of the tours around Florida you will see a phenomenon that is hard to believe. You will see a guy who during the week works for Bransdmart and is just a casual player, giving a seasoned professional fits and often beating top name players. How can this be?

It comes from competing, you just learn something that can't be gotten from a book, video, lecture or anywhere else. It is truly amazing. Back to the compulsive practicer. If his goal is to become a really good player it just won't happen constantly looking for the perfect place to place his feet or grip his cue. At a point you have to just use your god given tools and play without all the paralyzing over analysis. I think I have belabored this long enough. This is not meant to be a criticism of anyone, just honest thoughts from many years of observing players.

dr_dave
12-04-2004, 04:05 PM
<blockquote><font class="small">Quote Fred Agnir:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr>
I doubt there is any significant curve (swerve) in the shots in my video. My cue stick was nearly horizontal and I hit through the cue ball horizontal plane on every shot. <hr /></blockquote>
I think that this is a mistake to dismiss the effects of swerve. It's a greater effect than most people ever consider.<hr /></blockquote>

I agree that people often underestimate the potentially undesirable effects of swerve. However, swerve can be minimized by keeping the cue stick as horizontal as possible and by hitting the cue ball on its centerline (left and right of center without follow or draw).

<blockquote><font class="small">Quote Fred Agnir:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr>
&lt;/font&gt;&lt;blockquote&gt;&lt;font class="small"&gt;Quote:&lt;/font&gt;&lt;hr /&gt;
My actual cue stick elevation was only about 1.4 degrees per my measurements and analysis
<hr /></blockquote>1.4 degrees? Maybe I need to see the shot in question, in order to clear the cushion, aren't you at a minimum 2 degrees? And most people want their fingers to clear the cushion, so that might add more. How did you hit that shot? Were you leaned out over the table so that the cue stick was nearly flat? How could you guarantee repeatability?<hr /></blockquote>

TP A.3 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/new/TP_A-3.pdf) clearly shows my measurements and calculations. I assure you that my stick had minimal elevation (about 1 1/2 degrees). The stick was close to touching the end rail at cue ball contact. To help ensure repeatability, I shot the shot many times, throwing out the cases where everything did not seem right to me (in terms of straight follow-through, cue stick elevation, chalk mark position on the cue ball, etc.).

Please view the video (http://www.engr.colostate.edu/~dga/pool/normal_videos/new/NVA-17.htm). Many of your questions are answered there.

Stretch
12-04-2004, 08:19 PM
<blockquote><font class="small">Quote Popcorn:</font><hr> You said what I was trying to say a little better then I did. Another problem is not having confidence in what you know. If a player goes into a slump, the worst thing they can do is changing everything thinking it will get better. If it worked before it will work again and changes may not help but just wreck your game. Now here is the rub. There is always something that may be able to be changed with a positive result. Something that could take you to the next level. I believe this is where an instructor may be of help. All things being equal though, the greatest tool and short cut to improvement is competition with better players. Like a child learns from emulating, so do adults on a subcsinious level.

It never fails, let a player start playing in a room with better players or playing tournaments and if he comes back to his old room he is amazingly a much better player, often in a very short time. That is also a little what I was talking in regards to the chronic practicer, (Student), who never competes, they don't really seem to get any better. If you go to some of the small tours such as the Joss tour or some of the tours around Florida you will see a phenomenon that is hard to believe. You will see a guy who during the week works for Bransdmart and is just a casual player, giving a seasoned professional fits and often beating top name players. How can this be?

It comes from competing, you just learn something that can't be gotten from a book, video, lecture or anywhere else. It is truly amazing. Back to the compulsive practicer. If his goal is to become a really good player it just won't happen constantly looking for the perfect place to place his feet or grip his cue. At a point you have to just use your god given tools and play without all the paralyzing over analysis. I think I have belabored this long enough. This is not meant to be a criticism of anyone, just honest thoughts from many years of observing players. <hr /></blockquote>

Great post Popcorn. Knowone can do it on thier own. Turns out that your hardest competition is actually your greatest ally. St

SpiderMan
12-07-2004, 11:42 AM
Dave,

When I view your "8-on-the-break" high-speed videos, I can't see anything but the immediate area of the rack. The titles say "8 in side", "8 in near corner", etc, but since I can't see any of the pockets they don't illustrate the sequence for me. Do I need to change some computer settings? Does anyone else see the pockets on these videos?

SpiderMan

dr_dave
12-07-2004, 11:56 AM
<blockquote><font class="small">Quote SpiderMan:</font><hr>When I view your "8-on-the-break" high-speed videos, I can't see anything but the immediate area of the rack. The titles say "8 in side", "8 in near corner", etc, but since I can't see any of the pockets they don't illustrate the sequence for me. Do I need to change some computer settings? Does anyone else see the pockets on these videos?<hr /></blockquote>

You are not doing anything wrong. I purposely had the view zoomed up on the rack so one could see the high-speed ball interaction clearly (and because I didn't have enough ceiling height for the lense on the high-speed camera). If anyone else can see the pockets, they have extremely good visualization capabilities (and imaginations).

You have to imagine the rack on the foot spot and imagine where the pockets are relative to the rack. In each clip, the 8-ball does head toward the listed pocket. I had to break about 50 (or more ... I wasn't counting) racks to get these clips. The most common direction was toward the far side pocket (see HSV 7.10 and 7.11 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/index.html)).

hookster52
12-23-2004, 12:25 PM
hi there Dr Dave.
i would like to thank you for your help i think it is great.
i got your book and it is helping me a lot.
what i am wanting too know is how to calculate a carom shot if the cueball and the first object ball are not lined up in a 30 degree path. i know that the cueball follows a 30 degree path if the line of aim is in a 30 degree angle but what if the cueball and the first ball you are hitting to make cueball hit the ball your trying to make is not in a 30 degree angle defliction path. how do you calculate for cueball path ?? thanks

Stretch
12-23-2004, 04:59 PM
<blockquote><font class="small">Quote hookster52:</font><hr> hi there Dr Dave.
i would like to thank you for your help i think it is great.
i got your book and it is helping me a lot.
what i am wanting too know is how to calculate a carom shot if the cueball and the first object ball are not lined up in a 30 degree path. i know that the cueball follows a 30 degree path if the line of aim is in a 30 degree angle but what if the cueball and the first ball you are hitting to make cueball hit the ball your trying to make is not in a 30 degree angle defliction path. how do you calculate for cueball path ?? thanks <hr /></blockquote>

Seasons greetings Hookster. This might help.....when i'm looking at a carom of less than 30% your basically hitting "throught" the carom ball to get to the ob. OR you can cut the carom ball real thin and make the ob. I find that hitting through the ob much more dependable. What i do is draw a line from the ob's contact point to the carom ball. Where that line touches the carom ball is your target. It will be on the oposite side of where your standing behind the cue ball, but just aim for that point anyway as if the rest of the carom ball wasn't there. Use half a tip high and get natural roll or a little follow, remember it's a follow stroke. It dosn't take long to get the hang of it. St.

dr_dave
12-23-2004, 05:24 PM
<blockquote><font class="small">Quote hookster52:</font><hr> hi there Dr Dave.
i would like to thank you for your help i think it is great.
i got your book and it is helping me a lot.<hr /></blockquote>
I am glad you are finding my stuff useful.
<blockquote><font class="small">Quote hookster52:</font><hr>what i am wanting too know is how to calculate a carom shot if the cueball and the first object ball are not lined up in a 30 degree path. i know that the cueball follows a 30 degree path if the line of aim is in a 30 degree angle but what if the cueball and the first ball you are hitting to make cueball hit the ball your trying to make is not in a 30 degree angle defliction path. how do you calculate for cueball path ?? thanks <hr /></blockquote>
I've posted my reply on a new thread (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&amp;Board=ccb&amp;Number=171111&amp;page =0&amp;view=collapsed&amp;sb=5&amp;o=&amp;fpart=1). Please check it out there.

dr_dave
12-23-2004, 05:39 PM
Stretch,

I hope you don't mind, but I've posted your reply on the new thread (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&amp;Board=ccb&amp;Number=171111&amp;page =0&amp;view=collapsed&amp;sb=5&amp;o=&amp;fpart=1) so everything will be in one place.

Stretch
12-24-2004, 11:01 AM
<blockquote><font class="small">Quote dr_dave:</font><hr> Stretch,

I hope you don't mind, but I've posted your reply on the new thread (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&amp;Board=ccb&amp;Number=171111&amp;page =0&amp;view=collapsed&amp;sb=5&amp;o=&amp;fpart=1) so everything will be in one place. <hr /></blockquote>

......and there it went to a merciful end. lol St.

Scott Lee
12-25-2004, 06:12 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> Your point is well taken. Many players don't benefit from knowing and trying to apply principles. Also, nothing can beat intuition built from years of practice and success.

However, I think the 30 degree can dramatically improve the games of many people. This assumes that the player has good fundamentals and can make routine shots with ease. It is not worth thinking about position play and where the cue ball will go if one is going to miss easy shots.

Personally, the 30 degree rule helped bring my game to a new level. I am a much better player with the 30 degree rule than and was without it. I think this can be the case for others too. <hr /></blockquote>

dr. dave...Not to take anything away from your 'technical expertise', I believe that knowing simple physics, that show definitively that topspin causes the CB to curve across the tangent line, and backspin causes the CB to curve away from the tangent, are much more significant than applying a '30 degree rule'...which can be ruled out by how high or low you stroke the CB, and how much speed you shoot. Keep it simple! However, for the techies out there, your explanations are excellent and well illustrated.

Scott Lee

randyg
12-26-2004, 07:46 AM
Tap,tap. Nice answer Scott....randyg

dr_dave
12-26-2004, 08:08 AM
<blockquote><font class="small">Quote Scott Lee:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> Your point is well taken. Many players don't benefit from knowing and trying to apply principles. Also, nothing can beat intuition built from years of practice and success.

However, I think the 30 degree can dramatically improve the games of many people. This assumes that the player has good fundamentals and can make routine shots with ease. It is not worth thinking about position play and where the cue ball will go if one is going to miss easy shots.

Personally, the 30 degree rule helped bring my game to a new level. I am a much better player with the 30 degree rule than and was without it. I think this can be the case for others too. <hr /></blockquote>

dr. dave...Not to take anything away from your 'technical expertise', I believe that knowing simple physics, that show definitively that topspin causes the CB to curve across the tangent line, and backspin causes the CB to curve away from the tangent, are much more significant than applying a '30 degree rule'...which can be ruled out by how high or low you stroke the CB, and how much speed you shoot. Keep it simple! However, for the techies out there, your explanations are excellent and well illustrated.<hr /></blockquote>

Thank you for the compliment. FYI, much more information about the 30 degree, when it applies, and how it can be used (in simple and effective ways) can be found at:
30 degree rule thread (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&amp;Board=ccb&amp;Number=168248&amp;page =&amp;view=&amp;sb=&amp;o=)

Bob_Jewett
12-27-2004, 03:02 PM
<blockquote><font class="small">Quote Scott Lee:</font><hr> ... I believe that knowing simple physics, that show definitively that topspin causes the CB to curve across the tangent line, and backspin causes the CB to curve away from the tangent, are much more significant than applying a '30 degree rule'...which can be ruled out by how high or low you stroke the CB, and how much speed you shoot. Keep it simple! ... <hr /></blockquote>
Hi Scott,

If you ever have the chance, spend a few days to learn the basics of English Billiards with someone who knows the game well (frequent breaks over 50). I think it will be a real eye-opener to you with regards to the half-ball follow angle.

dr_dave
12-28-2004, 08:31 AM
<blockquote><font class="small">Quote Scott Lee:</font><hr>
dr. dave...Not to take anything away from your 'technical expertise', I believe that knowing simple physics, that show definitively that topspin causes the CB to curve across the tangent line, and backspin causes the CB to curve away from the tangent, are much more significant than applying a '30 degree rule'...which can be ruled out by how high or low you stroke the CB, and how much speed you shoot. Keep it simple! However, for the techies out there, your explanations are excellent and well illustrated.<hr /></blockquote>
Scott,

The 30 degree rule is not just for "techies." The derivation and physics behind it IS just for "techies," but knowing where the cue ball will go for basic shots is important to and attainable by ALL. For a stun shot, the cue ball heads directly in the tangent line direction. For a roll shot, the cue ball heads very close to the 30 degree direction, which is easy to visualize with your hand (see NV 3.8 (http://www.engr.colostate.edu/~dga/pool/normal_videos/index.html)). I think that's fairly simple.

To me, being able to judge where the cue ball will go with various draw and follow shots at different speeds is not simple. That ability, even if you know all of the principles, requires lots of intuition that can come only with years of practice and experience.

For more information on how to "keep it simple," see my January-July, '04 and February-March, '05 instructional articles online (http://www.engr.colostate.edu/~dga/pool/bd_articles/index.html).

dr_dave
12-28-2004, 09:13 PM
FYI, this discussion has been continued under a new thread (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&amp;Board=ccb&amp;Number=171548).

dave9ball
01-01-2005, 09:10 AM
I agree that a little knowledge can produce dramatic results. I consider myself a "student" - over 40 years of study and still learing. My fellow team members love the 30 and 90 degree rule. Just having the knowlege has reduced the team scratches. TAP skill levels 4-5-6 seem to benefit more. Frequently they fail to see when to apply theknowledge, or the execution may fail, but sometimes it all comes together and is quite rewarding for everyone. It is easy to share knowledge. Very difficult to share execution.

dave9ball
01-01-2005, 09:27 AM
I think the articles and web site are outstanding. My engineering is a little rusty, but I think the principles are great!
Your recent article discussed difficulty related to distance. I have used the following estimation for years. I am curious if it is close to valid. I take an object ball 1 diamond from the pocket and the cue ball 1 diamond from the OB to be a difficulty of 1. I multiply the Cue to OB distance by the OB to pocket distance to get a relative number. A shot with OB 2 diamonds from pocket and cue 3 diamonds from OB is difficulty 6 ( 6 times more difficult than a 1). It can be useful in shot selection as well as speed. I consider angle difficulty to be a function of the cosine of the shot angle. I think I got this from an old Bob Jewett article.

dave9ball
01-01-2005, 09:59 AM
Another theory - When trying to draw the ball, I will sometimes jump the ball off the table. I thought the primary reason was the cue tip contacting the cloth just before hitting the ball. HSV A.1 shows an illegal jump; scooping under a ball. Is that cue tip hitting the cloth before the ball?
Thanks

dr_dave
01-01-2005, 11:20 AM
FYI, I've posted a new thread (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&amp;Board=ccb&amp;Number=172122&amp;page =0&amp;view=collapsed&amp;sb=5&amp;o=&amp;fpart=1) to continue this discussion.

Qtec
01-01-2005, 12:41 PM
[ QUOTE ]
I consider myself a "student" - over 40 years of study and still learing. My fellow team members love the 30 and 90 degree rule. Just having the knowlege has reduced the team scratches. <hr /></blockquote>

If you really have been playing for 40 years and you didnt know the 90 degree rule [ which IS a rule], you must be a moron! /ccboard/images/graemlins/smile.gif
In fact, you should never be allowed to pick up a cue or get anywhere near a pool table. /ccboard/images/graemlins/smirk.gif

Dr Dave,s 30 degree rule IS NOT A RULE! It has been known from the begining of time as the NATURAL ANGLE!!

In fact, when challenged on his theory that speed affects sqirt, he has not yet given a reply. Why not?

Qtec [ thinks its strange that the only ones who are singing the praises of Dr D are the ones with few posts! No offence dave, but its just too obvious, even for us dumb pool players!]

dr_dave
01-01-2005, 03:06 PM
<blockquote><font class="small">Quote dave9ball:</font><hr> Another theory - When trying to draw the ball, I will sometimes jump the ball off the table. I thought the primary reason was the cue tip contacting the cloth just before hitting the ball. HSV A.1 shows an illegal jump; scooping under a ball. Is that cue tip hitting the cloth before the ball?
Thanks <hr /></blockquote>
If the cue ball is "scooped" up during a draw stroke, it is most likely due to a miscue. The effect is much like a miscue with a poorly hit shot with English, where the ball deflects (squirts) way to the side (e.g., see HSV 2.1 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/index.html)).

In HSV A.1 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/index.html)), the cue tip did not hit the cloth before the ball. The tip hits the ball first and then slides towards the cloth due to a miscue. However, I think the cue tip is in contact with both the ball and cloth at the same time as the cue ball launches into the air. I'm not sure if this is required for a "scoop" jump but it certainly helps. I think it is possible (and even likely) for the ferrule and even the cue stick to also hit the cue ball after the initial cue tip contact (as with the English miscues shown in HSV A.13 through HSV A.20 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/index.html).

I think significnt cue ball "scoop" can occur only if there is a miscue. Now I wish I had filmed many more shots to see scoops at various heights and from strokes of various speeds, elevations, and offsets. I'll add this to my list for my next video shoot.

Scott Lee
01-01-2005, 07:24 PM
Bob...Although I have not played English billiards, I am certainly familiar with the half-ball follow angle. I'd love to play that game some. Are you volunteering to teach me?

Scott Lee

dr_dave
01-06-2005, 09:44 AM
FYI, I have two new areas on my "Illustrated Principles" website (http://www.engr.colostate.edu/pool):<ul type="square"> The "Online Discussion Threads" (http://www.engr.colostate.edu/~dga/pool/threads.html) area has links to threads directly related to "Illustrated Principles" questions from CCB participants or BD readers (from my monthly column).

The "Upcoming Events" (http://www.engr.colostate.edu/~dga/pool/events.html) area lists dates and locations for my free "Illustrated Principles of Pool and Billiards" seminar. I will be presenting this multimedia talk over the next three years across the country, sponsored by the American Society of Mechanical Engineers. The talks are usually open to the public, so periodically check out the dates and locations on my website. It would be fun to have some CCB participants (and not just engineers) in the audience. The seminar is geared toward a general audience (even non pool players), but it is usually well received by both engineers and seasoned pool players.[/list]
I hope to meet some of you guys at my talks.

nhp
01-06-2005, 04:17 PM
<blockquote><font class="small">Quote Qtec:</font><hr> &lt;/font&gt;&lt;blockquote&gt;&lt;font class="small"&gt;Quote:&lt;/font&gt;&lt;hr /&gt;
I consider myself a "student" - over 40 years of study and still learing. My fellow team members love the 30 and 90 degree rule. Just having the knowlege has reduced the team scratches. <hr /></blockquote>

If you really have been playing for 40 years and you didnt know the 90 degree rule [ which IS a rule], you must be a moron! /ccboard/images/graemlins/smile.gif
In fact, you should never be allowed to pick up a cue or get anywhere near a pool table. /ccboard/images/graemlins/smirk.gif

Dr Dave,s 30 degree rule IS NOT A RULE! It has been known from the begining of time as the NATURAL ANGLE!!

In fact, when challenged on his theory that speed affects sqirt, he has not yet given a reply. Why not?

Qtec [ thinks its strange that the only ones who are singing the praises of Dr D are the ones with few posts! No offence dave, but its just too obvious, even for us dumb pool players!]
<hr /></blockquote>

I don't think Dave would go to lengths such as to borrow a friend's computer to make a new ID to praise his own self. Note the IP's are different from Dave9ball and Dr. Dave.

dr_dave
01-07-2005, 10:42 AM
<blockquote><font class="small">Quote nhp:</font><hr><blockquote><font class="small">Quote Qtec:</font><hr>thinks its strange that the only ones who are singing the praises of Dr D are the ones with few posts! No offence dave, but its just too obvious, even for us dumb pool players!<hr /></blockquote>
I don't think Dave would go to lengths such as to borrow a friend's computer to make a new ID to praise his own self. Note the IP's are different from Dave9ball and Dr. Dave. <hr /></blockquote>
nhp,
I don't think Qtec was accusing me of such a thing. I work hard on maintaining my website, writing articles, and responding to CCB postings and questions, and many people appreciate my efforts. I would take extreme offense if he really did have the malicious intent that you suggest.

dr_dave
01-07-2005, 11:03 AM
<blockquote><font class="small">Quote Qtec:</font><hr>In fact, when challenged on his theory that speed affects sqirt, he has not yet given a reply. Why not?<hr /></blockquote>
I thought the arguments I presented in my previous postings on cue stick elevation (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&amp;Board=ccb&amp;Number=168283&amp;Foru m=ccb&amp;Words=cue%20stick%20elevation&amp;Match=Entire%2 0Phrase&amp;Searchpage=0&amp;Limit=25&amp;Old=3months&amp;Main=167 746&amp;Search=true#Post168283) and the source of English curve (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&amp;Board=ccb&amp;Number=168768&amp;page =0&amp;view=collapsed&amp;sb=5&amp;o=&amp;vc=1) made a fairly solid argument that curve (swerve) was a minimal factor in my experiment (http://www.engr.colostate.edu/~dga/pool/normal_videos/new/NVA-17.htm).

However, I think this topic is kind of like abortion. We can discuss it until we are blue in the face and many people's opinions will still not change (including mine, unless I see undeniable experimental and/or theoretical proof that I am wrong). And honestly, I don't think it matters too much what one does or does not believe about the source of the "effective squirt." The fact still remains that you need to adjust more at higher speed.

Qtec
01-07-2005, 12:46 PM
No offence intended Dave. Just a poor example of my warped english humour. /ccboard/images/graemlins/laugh.gif

Q

dr_dave
01-07-2005, 01:09 PM
<blockquote><font class="small">Quote Qtec:</font><hr> No offence intended Dave. Just a poor example of my warped english humour. /ccboard/images/graemlins/laugh.gif<hr /></blockquote>
Thank you very much for making that clear. I appreciate it. I have a British buddy (from the snooker world) that I play pool with regularly and I very much enjoy his warped sense of humor.

grizli30
01-18-2005, 01:41 AM
Dear Dr. Dave

I already buy your book Illustrated principles of Pool and Billiard by Amazon, and now I'd like to buy your DVD with the same title. I didn't find this item by Amazon so please tell me where can I buy this item. I'm from Evrope.

Best regards

dr_dave
01-18-2005, 08:16 AM
<blockquote><font class="small">Quote grizli30:</font><hr>I already buy your book Illustrated principles of Pool and Billiard by Amazon, and now I'd like to buy your DVD with the same title. I didn't find this item by Amazon so please tell me where can I buy this item. I'm from Europe.<hr /></blockquote>
The DVD and CD-ROM are available only through my website (http://www.engr.colostate.edu/~dga/pool/purchase.html). Sorry for the inconvenience. I do ship worldwide.

dr_dave
01-18-2005, 09:28 AM
<blockquote><font class="small">Quote BD reader:</font><hr>
Dr. Dave

Last night I while playing a game of 8 ball I scratched on a shot and, since we had decided earlier not to play the ball in hand rules, that all such shots would be played from the kitchen. At the time he had only one ball remaining on the table and that ball was also in the kitchen. . I have always played that under these circumstances, all shots had to be played from the kitchen to a ball outside the kitchen. Unfortunately, his one remaining ball was also in the kitchen. With this set of conditions, the people I have always played with insisted that the cue ball had to be played from the kitchen to a cushion and banked to the remaining ball. My opponent last night insisted that he had the right to spot his ball on the head spot so that he had a direct line to his ball. I have never heard of a rule variation like this and he insisted that this is universal. Can you clarify this for us?<hr /></blockquote>
I have not heard of this before; but it doesn't surprise me, because whenever people use unpublished "bar" rules, they seem to make up all kinds of stuff. I recommend that you try to use standard published rules. You can print a copy of a concise summary of BCA's rules (http://www.engr.colostate.edu/pool/rules_summary.pdf) from my website. That way, if a question arises, you can refer to the sheet.

Wally_in_Cincy
01-18-2005, 09:49 AM
[ QUOTE ]
My opponent last night insisted that he had the right to spot his ball on the head spot <hr /></blockquote>

I also had never heard of this until a old-school player brought it up in a game of barbox 9-ball. After checking with some of the veteran players on the CCB it turns out that it used to be quite common, before BIH rules were commonplace

SpiderMan
01-18-2005, 11:45 AM
Spotting a ball from in the kitchen was once quite common. I can see where someone who had been sheltered from playing other variations might think it universal.

SpiderMan

grizli30
01-18-2005, 01:24 PM
How much are the shipping costs for Slowenia ( country near Italy )

Best regards

grizli30
01-18-2005, 01:34 PM
Dr. Dave

Is there any major difference between DVD and CD-ROM. Do I need to buy both of them.

Best regards,

Grizli30

dr_dave
01-18-2005, 01:41 PM
<blockquote><font class="small">Quote grizli30:</font><hr> How much are the shipping costs for Slowenia ( country near Italy )<hr /></blockquote>
The shipping costs are the same for all non-US countries. Please refer to the non US portion of the website (http://www.engr.colostate.edu/~dga/pool/purchase_non_us.html) for details.

Please ask these sort of questions through private messages or emails. This type of question is really not appropriate for the CCB forum. Thanks.

dr_dave
01-18-2005, 01:45 PM
<blockquote><font class="small">Quote grizli30:</font><hr>Is there any major difference between DVD and CD-ROM. Do I need to buy both of them?<hr /></blockquote>
The differences are summarized on the website (see DVD list (http://www.engr.colostate.edu/~dga/pool/why_buy_dvd.html) and CD-ROM list (http://www.engr.colostate.edu/~dga/pool/why_buy_cdrom.html)). Both products have their own advantages. If you only want to purchase one, I would recommend the DVD.

If you have further questions, please send me a private message or e-mail. These types of questions really are not appropriate for the CCB forum.

dr_dave
01-21-2005, 10:58 AM
FYI, I have just updated TP 3.4 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/TP_3-4.pdf) on my website to include an example based on the discussion of required accuracy in the half ball hit angle range (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&amp;Board=ccb&amp;Number=172705&amp;page =0&amp;view=collapsed&amp;sb=5&amp;o=&amp;fpart=1) thread. Check it out. It shows how big of an effect distance and cut angle can have on required shot accuracy. For more discussion on this, see the thread on shot difficulty as a function of distance (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&amp;Board=ccb&amp;Number=172122&amp;page =&amp;view=&amp;sb=&amp;o=).

Popcorn
01-21-2005, 11:12 AM
Distance makes sloppiness show up. You can get away with being sloppy on close easy shots but when it gets farther away the error is magnified. So what do you do with this information? You learn to play a precision game at all times. Hit even the easiest shot precisely. If you get in the habit of this the longer shots will not present any problem. You will miss more long shots then you will close shots simply because the margin error is smaller, but that is to be expected. It least it won't be due to laziness on the easy shots.

Bob_Jewett
01-24-2005, 08:56 PM
<blockquote><font class="small">Quote Popcorn:</font><hr> ... You learn to play a precision game at all times. Hit even the easiest shot precisely. If you get in the habit of this the longer shots will not present any problem. You will miss more long shots then you will close shots simply because the margin error is smaller, but that is to be expected.... <hr /></blockquote>
Irving Crane said that the thing that really separated him from the other players was the accuracy of his pocketing. Hitting the center of the pocket consistently -- rather that having some laziness or bias ruining your accuracy -- is a huge advantage.

dr_dave
01-26-2005, 11:18 AM
FYI,
I just posted updated and improved versions of the following videos:
<ul type="square"> NV 4.15 - Using throw to make a partially blocked shot (http://www.engr.colostate.edu/~dga/pool/normal_videos/NV4-15.htm)
NV 7.6 - Frozen cue ball throw (http://www.engr.colostate.edu/~dga/pool/normal_videos/NV7-6.htm)
NV 7.10 - Double kiss of a ball frozen to a rail (http://www.engr.colostate.edu/~dga/pool/normal_videos/NV7-10.htm)[/list]
The new videos represent the pertinent concepts more clearly and correspond more precisely to the figures in the book.

dr_dave
01-26-2005, 11:52 AM
<blockquote><font class="small">Quote dr_dave:</font><hr> FYI,
I just posted updated and improved versions of the following videos:
<ul type="square"> NV 4.15 - Using throw to make a partially blocked shot (http://www.engr.colostate.edu/~dga/pool/normal_videos/NV4-15.htm)
NV 7.6 - Frozen cue ball throw (http://www.engr.colostate.edu/~dga/pool/normal_videos/NV7-6.htm)
NV 7.10 - Double kiss of a ball frozen to a rail (http://www.engr.colostate.edu/~dga/pool/normal_videos/NV7-10.htm)[/list]
The new videos represent the pertinent concepts more clearly and correspond more precisely to the figures in the book. <hr /></blockquote>
I apologize that my original videos did not provide a totally accurate representation of the intended topics. I think the updated versions do a much better job.

It is more than likely that other videos (http://www.engr.colostate.edu/~dga/pool/normal_videos/index.html) on my site have imperfections. If you think any of the videos should be re-shot because they don't adequately represent the intended concept, please let me know so I can add them to my re-shoot list.

I'm not making excuses, but it was very difficult to have all of my original videos come out perfect. For starters, I'm not a professional pool player and my technique is far from perfect. Also, I serve as camera operator (with the help of a tripod and remote control), lighting supervisor, author, technical consultant, narrator, shooter, editor, and webmaster all at once. I have no help whatsoever when I create the clips ... it's just me in my basement. Professionally produced videos involve many more people and lots of money. I think I shouted more profanities during my original taping session, which lasted over two weeks, than I have the rest of my life. It was often frustrating and stressful when I would have to continually re-shoot clips because I stuttered, missed a shot, hit the tripod by accident, casted an annoying shadow, etc. I was very glad when it was over and I am fairly happy that I don't have more mistakes than I do. But again, please let me know if you have any advice for further improvements.

dr_dave
01-26-2005, 12:18 PM
Several people have asked me about how I make and post my videos, so I thought I would share the procedure with others that might be interested:

1) Shoot raw footage with a mini-DV digital video camera mounted in a 4-way adjustable tripod. For overhead shots, I either have the tripod fully or partially on the table, with the help of bar stools; otherwise, it stands on the floor. I often shoot multiple "takes" of the same shot because of missed shots, narration errors, bad lighting or camera views, etc.

2) Download the video from the camera to my laptop through a firewire interface, using Pinnacle Studio software. Video requires lots of disk space (about 3-4 MB/sec ... that's megabytes per second!).

3) Use Pinnacle Studio to edit out the bad "takes" and trim the beginning and end of the best take. I also remove pauses and errors made (and later corrected) in the middle of a "take." That's why you sometimes see jumps in the middle of a clip.

4) Use Pinnacle Studio to store the edited video clip as a compressed Windows Media Video (WMV) file so it won't take up so much disk space and so it will be easily downloadable via the Internet. An uncompressed AVI video file can take up 50-100 more space than a compressed WMV file! In other words, if I didn't compress the video, it would take 50-100 times longer to download it via your Internet connection. The downside (because there are no "free lunches") is that the video image size and quality is not as good.

5) Use Dreamweaver software to edit my website and add links to the new video clips.

6) Use Dreamweaver to upload the new website and video files to my webserver (www.engr.colostate.edu) so they can be viewed by anyone in the world.

That's it ... difficult to learn at first, but very easy once you have done it for a while. It also helps being at a university where there are people around that know how to do all of this stuff and are willing (and excited) to show you how.

Fred Agnir
01-26-2005, 12:25 PM
<blockquote><font class="small">Quote dr_dave:</font><hr>


1) Shoot raw footage with a mini-DV digital video camera <hr /></blockquote>Do you have any issues with frame speed? Your high-res slow motion shots aren't done with MiniDV are they?

Fred

dr_dave
01-26-2005, 12:42 PM
<blockquote><font class="small">Quote Fred Agnir:</font><hr> <blockquote><font class="small">Quote dr_dave1) Shoot raw footage with a mini-DV digital video camera [/quote:</font><hr>Do you have any issues with frame speed? Your high-res slow motion shots aren't done with MiniDV are they?<hr /></blockquote>
The super slow motion video clips (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/index.html) are filmed with a special, and very expensive, high-speed camera. A photograph, information, and a procedure can be found on my website (see high-speed camera (http://www.engr.colostate.edu/~dga/me324/Labs/Lab%204/Camera%20Setup.htm)). Other than the camera, the other steps in the process are the same.

Popcorn
01-26-2005, 01:20 PM
I wish you would start new threads instead of pulling up these old long threads with half of the posts made by you..

Wally_in_Cincy
01-26-2005, 01:21 PM
<blockquote><font class="small">Quote Popcorn:</font><hr> I wish you would start new threads instead of pulling up these old long threads with half of the posts made by you.. <hr /></blockquote>

I'll second that. Often times worthwhile things in short threads get lost due the prescence of extremely long threads that keep coming back up again and again.

dr_dave
01-26-2005, 01:35 PM
<blockquote><font class="small">Quote Popcorn:</font><hr> I wish you would start new threads instead of pulling up these old long threads<hr /></blockquote>
I do start new threads when I anticipate lengthy discussion. Otherwise, I use this thread to post updates and informational items as a service to the readers of my articles. Also, sometimes people post questions here; although, like you, I wish they would start new threads if they anticipate discussion. I will do my best to continue to redirect important discussion to new, dedicated threads.

SpiderMan
01-26-2005, 03:06 PM
I'll definitely second that. I prefer one topic per thread, because you often can't detect a change in topic by looking at the titles of posts. Most people don't bother to re-label their post when they shift gears.

I don't like to sift through a lot of junk in order to determine whether there is new life in one dead horse, or if someone has substitued a possum.

SpiderMan

iacas
12-22-2005, 08:29 AM
<blockquote><font class="small">Quote dr_dave:</font><hr>You are correct. I am not a machine and I am not able to guarantee a perfectly consistent stroke. However, by observing my follow-through (on the video) and the chalk mark on the cue ball after every shot, I assure you that my stroke was fairly consistent for every shot I included on the video. I actually executed many more shots than I included in the final version. I threw out all shots that were not consistent, due to direction of follow-through or chalk mark placement. Bottom line: I stand by my consistency, although I admit it might not have been perfect.<hr /></blockquote>

So why not build a machine? The Meucci example may be a bit extreme, but then again, you're a physics prof and mechanical engineer, so there's no doubt in my mind the parts are available to you.

Dave Pelz was an aeronautical engineer (or something) for NASA, but he built a mechanical human to help him understand the perfect (in his mind) putting stroke. He nicknamed his mechanical creation "Perfy" and he's used "Perfy" to demonstrate a lot of things with scientific precision.

Could you not do something similar? Why rely on your own abilities when, as demonstrated by the person who prompted your quoted response, they cast doubt on the whole process?

tdurden87
12-22-2005, 02:42 PM
I don't really understand the difference between the 30 and 90 degree rules. Can anyone explain the difference to me?

Deeman3
12-22-2005, 03:47 PM
<blockquote><font class="small">Quote tdurden87:</font><hr> I don't really understand the difference between the 30 and 90 degree rules. Can anyone explain the difference to me? <hr /></blockquote> <font color="blue">

Quite simply, a cue ball with natural forward roll departs it's collision with another ball at approximately 30 degrees.

A cue ball with no forward or reverse spin departs it's collisioion with another ball at approximately 90 degrees.

This can be veryuseful in determining the path of the cue ball. </font color>

Deeman

Bob_Jewett
12-22-2005, 03:52 PM
<blockquote><font class="small">Quote Deeman3:</font><hr> ... Quite simply, a cue ball with natural forward roll departs it's collision with another ball at approximately 30 degrees.
...<hr /></blockquote>
You really need to qualify this with: "when the cut angle is between roughly 15 and 45 degrees." The actual cue ball carom angle varies over this range of cuts from about 25 to 35 degrees of deflection from the original cue ball path.

For fuller or thinner hits, there are other rules of thumb to use to find the carom angle.

iacas
12-23-2005, 12:17 PM
<blockquote><font class="small">Quote Bob_Jewett:</font><hr> <blockquote><font class="small">Quote Deeman3:</font><hr> ... Quite simply, a cue ball with natural forward roll departs it's collision with another ball at approximately 30 degrees.
...<hr /></blockquote>
You really need to qualify this with: "when the cut angle is between roughly 15 and 45 degrees." The actual cue ball carom angle varies over this range of cuts from about 25 to 35 degrees of deflection from the original cue ball path.

For fuller or thinner hits, there are other rules of thumb to use to find the carom angle. <hr /></blockquote>

Yeah, and the angles are measured from different lines, too.

The 30-degree rule is for cut angles from 1/4 to 3/4 ball and is measured from a continuation of the cue ball's path.

The 90-degree rule is on a stun shot and is measured from the object ball's path.

dr_dave
12-29-2005, 11:07 AM
<blockquote><font class="small">Quote iacas:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr>You are correct. I am not a machine and I am not able to guarantee a perfectly consistent stroke. However, by observing my follow-through (on the video) and the chalk mark on the cue ball after every shot, I assure you that my stroke was fairly consistent for every shot I included on the video. I actually executed many more shots than I included in the final version. I threw out all shots that were not consistent, due to direction of follow-through or chalk mark placement. Bottom line: I stand by my consistency, although I admit it might not have been perfect.<hr /></blockquote>

So why not build a machine? The Meucci example may be a bit extreme, but then again, you're a physics prof and mechanical engineer, so there's no doubt in my mind the parts are available to you.

Dave Pelz was an aeronautical engineer (or something) for NASA, but he built a mechanical human to help him understand the perfect (in his mind) putting stroke. He nicknamed his mechanical creation "Perfy" and he's used "Perfy" to demonstrate a lot of things with scientific precision.

Could you not do something similar? Why rely on your own abilities when, as demonstrated by the person who prompted your quoted response, they cast doubt on the whole process? <hr /></blockquote>
Sorry for the late reply, but I was out of town the last week without convenient access to the Internet.

Thanks for the suggestion to build a pool-shooting machine. I have thought about this before, but it would take lots of time and money to design and construct a device that would do everything I would want it to do accurately, repeatably, and efficiently. Maybe if I retire one day, I'll have the motivation and time to pursue such a project.

Regards,
Dr. Dave

PS: Some guys in Canada are working on a sophisticated pool-playing robot. It is a very sophisticated and chalenging project. (Although, that level of sopistication would not be required for a more basic aligning and shooting machine). For more info, see the thread I posted previously (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&amp;Board=ccb&amp;Number=211842&amp;page =0&amp;view=collapsed&amp;sb=5&amp;o=&amp;fpart=&amp;vc=).

dr_dave
12-29-2005, 11:17 AM
<blockquote><font class="small">Quote tdurden87:</font><hr> I don't really understand the difference between the 30 and 90 degree rules. Can anyone explain the difference to me? <hr /></blockquote>
Sorry for my late response. I was out of town the last week without convenient access to the Internet.

It looks loke Deeman, Bob_Jewett, and iacas have summarized the important point fairly well. For more information and lots of examples and illustrations, see the links under "30 degree rule" in the threads summary area of my website (http://www.engr.colostate.edu/~dga/pool/threads.html). Also, I have written many instructional articles (http://www.engr.colostate.edu/~dga/pool/bd_articles/index.html) on these topics. My July '04 article (http://www.engr.colostate.edu/~dga/pool/bd_articles/july04.pdf) probably does the best job answering your question.

I hope that helps,
Dr. Dave

dr_dave
02-27-2006, 02:18 PM
<blockquote><font class="small">Quote e-mail question from reader:</font><hr>On page 46 you have figure 3.13 (Object ball and cue ball speeds versus cut angle) How can you have the summation of both balls greater than 100% ? For example at 45 degrees your chart indicates that both the cue and object ball have about 70% speed each. The sum is 140%. Are you trying to illustrate that the cue ball has70% and the object ball has 30% speed at 45 degrees??<hr /></blockquote>
The graph is correct. After impact, both the CB and OB each have about 70% of the original (pre-impact) cue ball speed. The speeds are being compared to the original cue ball speed. The final speeds are not required to add up to the original speed. I know it doesn't seem right on the surface, but it is (see TP 3.2 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/TP_3-2.pdf) if you want to see the technical details).

Regards,
Dr. Dave

SpiderMan
02-27-2006, 04:13 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote e-mail question from reader:</font><hr>On page 46 you have figure 3.13 (Object ball and cue ball speeds versus cut angle) How can you have the summation of both balls greater than 100% ? For example at 45 degrees your chart indicates that both the cue and object ball have about 70% speed each. The sum is 140%. Are you trying to illustrate that the cue ball has70% and the object ball has 30% speed at 45 degrees??<hr /></blockquote>
The graph is correct. After impact, both the CB and OB each have about 70% of the original (pre-impact) cue ball speed. The speeds are being compared to the original cue ball speed. The final speeds are not required to add up to the original speed. I know it doesn't seem right on the surface, but it is (see TP 3.2 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/TP_3-2.pdf) if you want to see the technical details).

Regards,
Dr. Dave <hr /></blockquote>

Dave,

You might add, for clarification, that the squares of the two speeds will add up to the square of the original cueball speed (conservation of energy). Of course if the collision is not perfectly elastic, there will be losses.

In this case, (0.7)*(0.7) + (0.7)*(0.7) = 0.98, which is very nearly equal to (1.0)*(1.0). I could claim this to represent 2% energy loss, or just recognize that it's tough to read a graph that closely /ccboard/images/graemlins/smile.gif

SpiderMan

dr_dave
02-27-2006, 04:16 PM
Thanks, Spiderman.

Good clarification.

Dave

<blockquote><font class="small">Quote SpiderMan:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote e-mail question from reader:</font><hr>On page 46 you have figure 3.13 (Object ball and cue ball speeds versus cut angle) How can you have the summation of both balls greater than 100% ? For example at 45 degrees your chart indicates that both the cue and object ball have about 70% speed each. The sum is 140%. Are you trying to illustrate that the cue ball has70% and the object ball has 30% speed at 45 degrees??<hr /></blockquote>
The graph is correct. After impact, both the CB and OB each have about 70% of the original (pre-impact) cue ball speed. The speeds are being compared to the original cue ball speed. The final speeds are not required to add up to the original speed. I know it doesn't seem right on the surface, but it is (see TP 3.2 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/TP_3-2.pdf) if you want to see the technical details).

Regards,
Dr. Dave <hr /></blockquote>

Dave,

You might add, for clarification, that the squares of the two speeds will add up to the square of the original cueball speed (conservation of energy). Of course if the collision is not perfectly elastic, there will be losses.

In this case, (0.7)*(0.7) + (0.7)*(0.7) = 0.98, which is very nearly equal to (1.0)*(1.0). I could claim this to represent 2% energy loss, or just recognize that it's tough to read a graph that closely /ccboard/images/graemlins/smile.gif

SpiderMan <hr /></blockquote>

dr_dave
02-09-2007, 09:09 AM
<blockquote><font class="small">Quote BD reader:</font><hr>Dr. Dave,

I was wondering how to shoot a rail shot where the cb is on the long rail on one side of the side pocket and the ob is on the same rail on the other side of the side pocket.

Thanks<hr /></blockquote>
Most people recommend using low, rail-side English, aiming straight at the OB. With the right speed, the CB will squirt away from the rail and swerve back, avoiding the side pocket, and hit the OB squarely. Also, the small cut angle effect will tend to be cancelled by a small throw effect, sending the OB straight up the rail.

Regards,
Dave