curving an object ball....

dr_dave said:
BTW, I want to thank Bob Jewett for suggesting the maximum-kick-angle challenge shot. Honestly, I was a little surprised by the amount and direction the CB curved after rebound. I expected the observed curve direction for the masse-shot cheat, assuming some of the masses pin remained after rebound, but not for the level-cue shots, where the CB had stun (with sidespin) into the cushion. Based on explanations earlier in the thread, one might have expected the CB to curve in the opposite direction since a ball stunned into a cushion usually picks up topspin on the rebound. Topspin would cause the CB to curve in the other direction, straightening the angle to the corner. Was anybody else surprised by the amount and direction of curve on this shot?
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I'm surprised nobody commented on this. Was nobody else surprised that the CB curved in the long direction? Obviously, the CB must be picking up masse spin off the cushion that overpowers the previously-described topspin-off-the-cushion effect that is presumed to make banks curve short after rebound.

Regards,
Dave
 
dr_dave said:
BTW, I want to thank Bob Jewett for suggesting the maximum-kick-angle challenge shot. Honestly, I was a little surprised by the amount and direction the CB curved after rebound. I expected the observed curve direction for the masse-shot cheat, assuming some of the masses pin remained after rebound, but not for the level-cue shots, where the CB had stun (with sidespin) into the cushion. Based on explanations earlier in the thread, one might have expected the CB to curve in the opposite direction since a ball stunned into a cushion usually picks up topspin on the rebound. Topspin would cause the CB to curve in the other direction, straightening the angle to the corner. Was anybody else surprised by the amount and direction of curve on this shot?

I think what is going on is a gyroscopic effect. When an object is spinning about one axis while you turn it about a 2nd axis, the object picks up spin about the 3rd axis (perpendicular to the 1st and 2nd axes). For the kick shot, the sidespin is about the vertical axis, and the topspin picked up off the cushion is about a horizontal axis parallel to the cushion. The gyroscopic effect causes masse spin about an axis perpendicular to both of the other axes. That's what causes the curve. That's my "theory" anyway. What do the "science guys" (or others) out there think?

Regards,
Dave

PS: If you've never heard of or seen the "gyroscopic effect" before and are curious, there's lots of videos on YouTube, and the Wikipedia page also describes and illustrates it well.
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I have a vague recollection of Don "The Preacher" Feeney, on one of his instructional videos, talking about a gyroscopic effect for position play. But apparently those brain cells were lost or damaged some time ago and cannot pull up additional info.

Lou Figueroa
damnit
 
lfigueroa said:
I have a vague recollection of Don "The Preacher" Feeney, on one of his instructional videos, talking about a gyroscopic effect for position play. But apparently those brain cells were lost or damaged some time ago and cannot pull up additional info.
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That's good those cells were lost, because they contained bad info, per my follow-up posts.

Regards,
Dave
 
dr_dave said:
That's good those cells were lost, because they contained bad info, per my follow-up posts.

Regards,
Dave
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Perhaps. But here's the funny thing: when I watched his videos, some 20 years ago, I recall trying the thing about the gyroscopic effect and it worked. Now, it may have been some other thing going on that wouldn't fit the right equations... but in real life and on a real pool table, for whatever reasons, it worked.

Lou Figueroa
 
Damn, y'all be talkin' all about vectors and wobbling poles and sh$t. All I know is how to run out. That and cucumbers taste better pickled.
 
lfigueroa said:
Perhaps. But here's the funny thing: when I watched his videos, some 20 years ago, I recall trying the thing about the gyroscopic effect and it worked. Now, it may have been some other thing going on that wouldn't fit the right equations... but in real life and on a real pool table, for whatever reasons, it worked.

Lou Figueroa
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It may have been really neat action but nothing really to do with gyroscopes.
 
Bob Jewett said:
So the experiment that might be done is to spin a ball in place and then shoot a soft 1/4-ball contact combo at it (where the striking ball is close to the spinning ball and so has no follow at contact). My prediction is that the two balls will go close to the same distance unaffected by whether there is spin or not. (This is the expected result for a 45-degree cut shot with stun -- both balls go the same distance.)
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I might guess the spinning ball will go a bit farther, consistently, because of friction....but that's just a guess based on some intuition.

But that's not what I'm getting at, though maybe it's related. I think if the ball comes off the rail with very little side spin, you might get more effective topspin, perhaps having something to do with John's shot. And if it comes off the rail with a lot of side spin, I think the top spin it picks up actually forces the masse action you see in Dave's challenge video.
 
Bob Jewett said:
It may have been really neat action but nothing really to do with gyroscopes.
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Granted. However, as someone who, as a kid played around with one of those dime store gyroscopes (that would be a Dollar Store for al the youngsters out there), his description of gyroscopic action made complete sense.

Lou Figueroa
 
FWIW, Feddy Bentivegna also demonstrates curving a bank shot on his DVD. I haven't checked his book to see if it is in there also.
 
Eric. said:
John Brumback said:
If you are going to test pool shots.... you need a pro shooting them. That is all.John B.
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But John, Dr. Dave has been scoring like a pro on his own Pool drill shots and he has been writing Pool instructional articles since when he was a D player...
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Funny! :p

I am certainly (and obviously) nowhere even close to being a pro-level player. I am able to get a high rating on the Masters-level BU playing-ability exams with well-practiced attempts, but this is very different from what a first-attempt rating might be (which is a more-realistic measure of one's current playing ability). A true world-champion pro should be able to do very well on the BU Exams (including the Doctorate-level Exam II), even with no previous practice with the exams. Again, there is a huge difference between a well-practiced attempt and a first attempt. Having said this, a true "D" or "C" player (and many "B" players, and even some "A" players) would not be able to get a pro-level rating on the BU playing-ability exams, even with lots of practice. Really high scores require a wide range of pool skills, mental focus, and playing ability. Regardless, you make a good point that a well-practiced BU rating is not necessarily an accurate measure of true playing ability. Anybody (including me) who knows anything about the BU playing-ability exams would agree with this 100%. (However, the challenge of attempting to increase one's scores on the exams is still a fun way to force oneself to put in high-quality and worthwhile practice. That's why I do it.)

Now, concerning demonstrating particular types of shots, I disagree with John that one needs to be a world-champion pro to be able to demonstrate and execute reasonable shots possible at a pool table. An amateur might not execute a shot perfectly the first time; but with enough attempts, and with a knowledge or understanding of what type of hit is required (concerning direction, speed, and spin), a decent amateur can execute any reasonable shot. Exceptions might include extreme power shots or super-advanced-technique trick shots. Those types of shot require special abilities and skills; and some amateurs (and even some pros) might not be able to replicate all of these types of shots, even with a large number of attempts. Also, some shots are not possible under certain conditions, and won't be possible on some tables. I think a post-rebound-curve bank shot might fall in this category, but I won't know for sure until I and/or others do more testing on different equipment over a range of hits at different angles, speeds, and spins.

Regards,
Dave

PS: Eric and others of similar mind, if you think the BU Exams are so easy, please show us how it's done by posting scores (and videos if available) on the AZB BU sticky thread, as many other AZB members have done. By the way you and some others "talk" on the forum, you guys should be able to crush the scores I have posted. Good luck! :grin-square:
 
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HawaiianEye said:
Dr. Dave,

I've watched a lot of your videos and was wondering what table you are using in them.

Aloha
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It's an 8' Connelly with Championship cloth, but I will be trying the post-rebound-curve banks on a variety of equipment types and conditions.

Regards,
Dave
 
dr_dave said:
PS: Eric and others of similar mind, if you think the BU Exams are so easy, please show us how it's done by posting scores (and videos if available) on the AZB BU sticky thread, as many other AZB members have done. By the way you and some others "talk" on the forum, you guys should be able to crush the scores I have posted. Good luck! :grin-square:
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Dave,

I'm sure you realize that i bust your balls because it was ludicrous when you were writing Billiards Digest articles, pontificating like an expert and...you shot like a rank beginner.

Anywho, i have a suggestion for you...why don't you enter a regional tournament and see how you do? You know, drill scores are great and all, especially if you practice the same set up over and over until it's perfected, but at the end of the day, don't you want to know where your skill level is, in the *real world*?


Eric
 
Eric. said:
Dave,

I'm sure you realize that i bust your balls because it was ludicrous when you were writing Billiards Digest articles, pontificating like an expert and...you shot like a rank beginner.

Anywho, i have a suggestion for you...why don't you enter a regional tournament and see how you do? You know, drill scores are great and all, especially if you practice the same set up over and over until it's perfected, but at the end of the day, don't you want to know where your skill level is, in the *real world*?


Eric
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I'm sure you have numerous examples of the nonsense Dr. Dave has been feeding us. Of course, it does go without saying that there are insights you can only learn from a pro, such as:

- There is no such thing as throw.

- A touch of inside english increases your margin of error.

- A handful of alignments can inexorably lead you to the shot line.

- Swooping generates more spin than you can get otherwise.

- Pros have special stroke that can make the cueball do things the rest of us can only envy.

Jim
 
I just wanted to comment a bit further about this discussion. I think that there is room for many perspectives, especially that of living bank pool legend John Brumback as well as the expertise of Dr Dave. As I see it, we get the best of both worlds here: a wealth of practical knowledge and the perspective of how to "sense" the shot and on the other side of the spectrum, the attempt to replicate, document, and explain and share the phenomenon from a scientific perspective. This means that we all win, imo.

I can personally vouch that JB can make a player better and I think that Dr Dave's high speed videos and more are awesome as well.
 
jalapus logan said:
I don't care how good or bad Dr. Dave plays. I like his analysis and enjoy what he brings to our game. Consider me a fan.
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I'm also a fan. I've been playing for over 60 years and enjoy everything that Dr. Dave has to say.
My thanks' to him for putting the time and effort to post here.
 
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