$100 Spin Challenge

[Patrick Johnson]

I've decided to pay it to "iusedtoberich", to show it was a serious offer and because he was the only poster who actually tried to take it seriously.

I think Bob Jewett deserves it. Maybe his post seemed a little trouble-maker-ish, but he did make some excellent points.

I include Bob among the posters who already knew the answer. The challenge was for those who didn't, to try to get them to really engage the question. Iusedtoberich is the only one among them who really did with any sincerity.

For all that Bob has taught me over the years, $100 would be an insult.

pj
chgo

 

[Rich93]

(...) a few people trying to discuss nutrition while everybody else is having a food fight. (...)

Rep-worthy line, but I have to spread it around first.

 

[Jaden]

you are right....

The same "initial aim line" passes through the pivot points of both cues. It's just a coincidence that it also happens to pass through the bridge position of one of them. The bridge positions have nothing to do with it.

pj
chgo

Patrick in this case you are right. I should have said pivot point.... It is misleading to say bridge position.

The only reason I said bridge position, is because when most people hear about pivot points, they relate it to the cues pivot point that cancels out squirt. Because the pivot points on LD shafts are so different to other shafts, you have to use the same pivot point on both shafts for comparison.

If you do that, and you use the pivot point that cancels out squirt on the regular shaft as the comparison point, the same pivot point on the LD shaft will have a natural offset closer to cenerball on the CB even though the actual offset is identical.

I referenced bridge position because I hoped that would eleviate the possibility for confusion on pivot points with natural pivot points that are where the pivot cancels out squirt.

JAden

 

[dr_dave]

I include Bob among the posters who already knew the answer. The challenge was for those who didn't, to try to get them to really engage the question. Iusedtoberich is the only one among them who really did with any sincerity.

Fair enough.

For all that Bob has taught me over the years, $100 would be an insult.

Ditto! Although, I bet if everybody who learned a lot from Bob would send him $100, he wouldn't feel so insulted.

On the contrary, I bet he would be quite happy ... and ridiculously wealthy.

The least I can do for all I've learned is to offer to pay for his plane ticket the next time he comes out to visit me for a filming and experimentation session. Bob, if you are listening, that's a genuine and honest offer. Maybe next time, others can join us (e.g., you, Mike Page, Colin, Cornerman, Jal, etc.). PM or e-mail me if you are interested.

Regards,
Dave

 

[dr_dave]

(...) a few people trying to discuss nutrition while everybody else is having a food fight. (...)

Rep-worthy line, but I have to spread it around first.

Ditto! ... quite creative and accurate.

Happy New Year!
Dave

 

[lfigueroa]

You could also ask where's Bob Jewett or Mike Page (or several other very knowledgable RSB posters who have been mostly invisible here). They obviously stay out of here because there's too much "noise" here - when they do post here their excellent observations are lost like whispers in a hurricane.

Not to compare myself with them, but I only do it because I dislike misinformation more than I dislike mud wrestling.

pj
chgo

I ain't one of them "knowledgeable" RSB guys, but as I work my way through this "Animal House" cafeteria of a thread, I just want to compliment you, PJ, for staying the course and suffering the occasional overaged frat boy, with much more good grace than you would have ever shown any of us on RSB.

Lou Figueroa
remembers
the "old" Pat

 

[Jal]

Jim,

I'm not exactly sure what you mean by your you last (bolded) statement, but maybe your whole paragraph has something to do with the slight trend changes we saw with the squirt vs. speed data from our robot tests (see Diagram 2 in my February '08 article).

Regardless, I agree that any variation in squirt with speed is negligible (practically speaking). Now, "effective squirt" or "squerve" (the combined effects of squirt and swerve) is another story.

Regards,
Dave

Dr. Dave,

Glad to see you're apparently feeling better. What I meant was that the effective offset b' is given by:

b' = Rsin[arcsin(b/R) - A + k(Wav)T]

where b is the initial contact point offset, A the squirt angle, and the last term is the amount of ball rotation during impact that contributes to the final effective offset. For an approximately symmetric force function over time, Wav (the time-averaged angular velocity) is about half the final angular velocity. The factor k, as best I can figure, is something like 1/5 or 1/4, which comes from considerations of the time-averaged torque divided by the time averaged force. It's somewhat dependent on the shape of the force-time curve, but doesn't vary much with different curves.

So if you compare two shots struck at (2/5)R at two different speeds, with total ball rotations of 2 and 4 degrees (WavT), respectively, using k=.25, and assuming squirt angles of 2.5 degrees with a high squirt stick, and 1.8 degrees with a low squirt stick, the ratios of effective tip offset are:

lower speed (2 degrees of rotation):

(b'/R)lowSq/(b'/R)highSq = sin[23.578 - 1.8 + .25(2)]/sin[23.578 - 2.5 + .25(2)] = 1.031

higher speed (4 degrees of rotation):

(b'/R)lowSq/(b'/R)highSq = sin[23.578 - 1.8 + .25(4)]/sin[23.578 - 2.5 + .25(4)] = 1.030

The calculation is a "first order" type since everything affects everything else. But the "perturbations" are very small. Nevertheless, it seems I grossly overstated the effect of ball rotation at higher speeds smoothing out the differences between cues! Intuition suggested it would be more than this. Do you agree, more or less, with the logic and conclusion?

One thing that it indicates is that the difference in resultant spin/speed ratios between the hypothetical high and low-squirt cues is about 3%. This is pretty small, but larger than a fraction of a percent. Does this sound reasonable?

I re-read your article and think it goes a long way to dispelling some myths. As always, thanks for the work and for making it available to us. Have you an explanation for the dip in the curve for squirt angle versus speed graph yet?

Jim

 

[dr_dave]

Dr. Dave,

Glad to see you're apparently feeling better.

Thank you. I am also glad. I still haven't slept a full night in the 2 weeks since my surgery, but the periods of agony (and pain killers with side effects) are over now.

What I meant was that the effective offset b' is given by:

b' = Rsin[arcsin(b/R) - A + k(Wav)T]

where b is the initial contact point offset, A the squirt angle, and the last term is the amount of ball rotation during impact that contributes to the final effective offset. For an approximately symmetric force function over time, Wav (the time-averaged angular velocity) is about half the final angular velocity. The factor k, as best I can figure, is something like 1/5 or 1/4, which comes from considerations of the time-averaged torque divided by the time averaged force. It's somewhat dependent on the shape of the force-time curve, but doesn't vary much with different curves.

So if you compare two shots struck at (2/5)R at two different speeds, with total ball rotations of 2 and 4 degrees (WavT), respectively, using k=.25, and assuming squirt angles of 2.5 degrees with a high squirt stick, and 1.8 degrees with a low squirt stick, the ratios of effective tip offset are:

lower speed (2 degrees of rotation):

(b'/R)lowSq/(b'/R)highSq = sin[23.578 - 1.8 + .25(2)]/sin[23.578 - 2.5 + .25(2)] = 1.031

higher speed (4 degrees of rotation):

(b'/R)lowSq/(b'/R)highSq = sin[23.578 - 1.8 + .25(4)]/sin[23.578 - 2.5 + .25(4)] = 1.030

The calculation is a "first order" type since everything affects everything else. But the "perturbations" are very small. Nevertheless, it seems I grossly overstated the effect of ball rotation at higher speeds smoothing out the differences between cues! Intuition suggested it would be more than this. Do you agree, more or less, with the logic and conclusion?

One thing that it indicates is that the difference in resultant spin/speed ratios between the hypothetical high and low-squirt cues is about 3%. This is pretty small, but larger than a fraction of a percent. Does this sound reasonable?

I need to look back to see where I got the fractional percent. I'll let you know when I do. I also need to think about your assumptions and analysis a little more before I can comment.

I re-read your article and think it goes a long way to dispelling some myths. As always, thanks for the work and for making it available to us.

You are welcome. Thank you for the kind words.

Have you an explanation for the dip in the curve for squirt angle versus speed graph yet?

This is one of those things that has bugged me for a while. I still can't explain it. However, it was a relatively small effect, and we really didn't have enough data to verify whether or not it is a repeatable trend.

Regards,
Dave

 

[SJDinPHX]

puhleeeze !

This is something along these lines that I posted back in 1999

Is the range of spin-to-speed ratios larger for a low-squirt stick than
for a high squirt stick? I?m thinking the answer is yes.

For a given hit eccentricity, is the spin-to-speed ratio larger for a
low-squirt stick than for a high squirt stick? I?m thinking the answer to
that is yes also.

First let me give the qualitative argument. Imagine hitting a ball with
maximum right english and a very squirty (lead-weighted) stick. The ball
might squirt out 30 degrees or so as the heavy stick pushes back to avoid
being deflected sideways. The impulsive force of the collision, which
includes a forward component and a sideways component, can be thought of
as simultaneous hits from two hypothetical squirtless sticks. One of
these is directed just like the real stick and produces (if it acted
alone) a ball going in the direction of the real stick with a
spin-to-speed ratio (w/V) characteristic of the tip offset, b. The other
hypothetical squirtless stick is directed perpendicular to the first and
has the same contact point. It produces (if it acted alone) a
perpendicular-moving cueball with a spin-to-speed ratio characteristic of
it?s tip offset (which is related to but different from the first one).
The two velocities add vectorally to produce the observed velocity, and
the two spins add vectorally to produce the observed spin. The key
point is this: because the two velocities are perpendicular to one
another, the magnitude of the resultant is always larger than the
magnitude of either component, and because the two spin vectors point in
opposite directions, the resultant spin magnitude is always smaller than
either component. Here?s another way to look at it. While you?re aiming
and hitting for maximum right english, the part of the stick-ball force
that is producing the squirt is also trying to give the cueball a little
left english. This is a small amount, but it?s enough to cancel out some
of the desired right english.

So am I suggesting a low-squirt stick gives "superspin?" Well it depends
on what you mean by superspin. If you mean a spin-to-speed ratio larger
than w/V = b*M/I, then no. If it means the low-squirt stick gives more
spin than squirtier sticks give, then yes. What I?m really suggesting is
that squirty sticks give a spin-to-speed ratio that is less than that
given by the above equation.

So how big an effect is this?

The above separation of forces is valid by the principle of superposition
of forces. Say you?re aiming in the x direction, and you?re hitting with
right spin with offset b. Then (this equation is from APAPP)

M * Vx = I * w / b.

And for the sideways direction,

M * Vy = I * w / b?.

b? is related to b by

b?**2 = R**2 * b**2

The sine of the squirt angle is Vy / Vx

Sin(t) = Vy / Vx = (w? * b) / (w * b?)

The goal now is to get the total spin (wt) and divide it by the total
speed (Vt) to get the spin-to-speed ratio.

w? = b? * sin(t) * w / b = sqrt(R**2 * b**2) * w * sin(t) / b

wt = w * w? = w(1- sin(t) * sqrt(R**2 * b**2) / b)

Vt = Vx * sqrt[1 + (sin(t)**2)]

The next equation shows that the actual spin-to-speed ratio is the
hypothetical [ b * M / I] multiplied by a factor that is smaller than
unity.

wt/Vt = b* M/I * [1 *( sqrt ( R**2 * b**2))* sin(t) / b] / sqrt[1 +
(sin(t)**2)]

Now sin(t) can be replaced with b / pp, where pp is the squirt pivot
point, and sin(t)**2 can be neglected.

This gives, as a working equation,
wt / Vt = b * M / I * [1 * (R/ pp )* sqrt( 1 * (b/R)**2)]

If we suppose that maximum offset is b/R = 0.5, then this equation gives
the following spin-to-speed ratios (as percentages of the theoretical
maximum) for sticks of various pivot points:

pp (in) spin-to-speed ratio

6 84
10 90
12 92
16 94
24 96
50 98

The bottom line is that a 40-inch pivot point stick can give about 5% more
spin than an (about average ?) 14 inch pivot point stick.

Is this significant? I think so. If it's right [], then it bolsters
the less-squirt-is-better position. Since spin-to-speed ratio is hard to
measure, I think the way to test this relation is to go from average
squirt to lots of squirt. Perhaps clamp a moveable weight to the shaft of
a house cue and measure maximum spin-to-speed as the weight is moved
forward toward the tip.

Puhleeze Mike !!!

Did you actually look at your numrical rambling ? Do you really believe that anyone in their right mind would try to apply these theories in the heat of a high $$$ pool game ? Sorry but NO chance.
The lenghty disertation that you have put out there, cannot be understood by the average physicist, much less a top notch player.
Theres only about 3 people on here that actually have a clue as to what you are talking about, and they are all certifiable !

Dick <----has made the ball go in the hole many times, WITHOUT physic's, for a lot of years.

PS You are probably a nice guy Mike, but you need to get a grasp on reality, for your sake. The only numerical equation in pool, is whether or not you make the game ball for the cash !

 

[1 Pocket Ghost]

Puhleeze Mike !!!

Did you actually look at your lengthy rambling ? Do you really believe that anyone in their right mind would try to apply these theories in the heat of a high $$$ pool game ? Sorry but NO chance.
The mumbo-jumbo that you have put out there, cannot be understood by the average physicist, much less a top notch player.
Theres only about 3 people on here that actually might understand what you said, and they are all certifiable !

Dick <----has made the ball go in the hole many times, without physic's for a lot of years.

PS You are probably a nice guy Mike, but you need to get a grasp on reality, for your sake. The only numerical equation in pool, is whether or not you make the game ball for the cash !

Give em hell Dick !!!

- Your old buddy, Ghost

 

[SpiderWebComm]

Puhleeze Mike !!!

Did you actually look at your numrical rambling ? Do you really believe that anyone in their right mind would try to apply these theories in the heat of a high $$$ pool game ? Sorry but NO chance.
The lenghty disertation that you have put out there, cannot be understood by the average physicist, much less a top notch player.
Theres only about 3 people on here that actually have a clue as to what you are talking about, and they are all certifiable !

Dick <----has made the ball go in the hole many times, without physic's for a lot of years.

PS You are probably a nice guy Mike, but you need to get a grasp on reality, for your sake. The only numerical equation in pool, is whether or not you make the game ball for the cash !

boy does that make sense or what. the only math you need is addition... counting the game balls

 

[Patrick Johnson]

Puhleeze Mike !!!

Did you actually look at your numrical rambling ? Do you really believe that anyone in their right mind would try to apply these theories in the heat of a high $$$ pool game ? Sorry but NO chance.
The lenghty disertation that you have put out there, cannot be understood by the average physicist, much less a top notch player.
Theres only about 3 people on here that actually have a clue as to what you are talking about, and they are all certifiable !

Dick <----has made the ball go in the hole many times, WITHOUT physic's, for a lot of years.

PS You are probably a nice guy Mike, but you need to get a grasp on reality, for your sake. The only numerical equation in pool, is whether or not you make the game ball for the cash !

Some people are actually able to play a decent game of pool and have an interest in the science behind it. Apparently you're not one of them. Is that what you have against it?

pj
chgo

 

[Jal]

...
Theres only about 3 people on here that actually have a clue as to what you are talking about, and they are all certifiable !

....has made the ball go in the hole many times, WITHOUT physic's, for a lot of years.

You should tell Mother Nature about that! Apparently she has a few delusions of her own.

It would help if you and the other posters who expressed similar sentiments understood what issue was being addressed....but that would be asking too much, I guess. It's much better to believe you can buy a cue that'll put 30% more spin on the ball than to have to come to grips with, hmmm, Reality.

Jim

 

[SJDinPHX]

Some people are actually able to play a decent game of pool and have an interest in the science behind it. Apparently you're not one of them. Is that what you have against it?

pj
chgo

No, Patrick that is not what I have against it. My take on all the numerical applicatons to pool are simply this.
As proven by the endless tirades you guy's seem to have with each other, the bottom line is "HAND-EYE CO-ORDINATION"
You will never convince me that any amount of scientific mumbo-jumbo can elevate someone to succeed at high level pool.
It is only a straw to grasp at for those who lack that God-given talent.
You may be able to help some beginner find a way to improve his shot-making skills, but it's going to take a Hell of a lot more than that to make him a top player. I'll give you C to B, but beyond that, its a joke.

Dick

(but it is fun to watch you guy's try.)

 

[JB Cases]

No, Patrick that is not what I have against it. My take on all the numerical applicatons to pool are simply this.
As proven by the endless tirades you guy's seem to have with each other, the bottom line is "HAND-EYE CO-ORDINATION"
You will never convince me that any amount of scientific mumbo-jumbo can elevate someone to succeed at high level pool.
It is only a straw to grasp at for those who lack that God-given talent.
You may be able to help some beginner find a way to improve his shot-making skills, but it's going to take a Hell of a lot more than that to make him a top player. I'll give you C to B, but beyond that, its a joke.

Dick

(but it is fun to watch you guy's try.)

Dick,

Why do you think that the discussions are intended to elevate anyone to a high level in pool?

You can take any sports activity and find hundreds of conversations/debates/arguments going on about the science/pseudo-science in the sport.

It's just conversation. We all know that none of this will make someone into a champion and I think that you might have the wrong idea what the goal is for the people who discuss these things are.

Actually the goal in a way is the same thing that you are saying. Pat's goal is to separate hype and myth from reality. Because sometimes the ads in our business do tend a little towards insinuating that if you play with x-product you will get much better. So while you are right that knowledge alone won't make a champion neither will the belief that a cue can produce 25% more spin all by itself. Something that a well known brand had advertised.

I for one, enjoy the conversations about the science of pool. I appreciate that there are people out there willing to put a lot of thought into what's really happening. I like to see the high speed videos and amateur videos of what people are doing and thinking about.

I expect that 2008/2009 will be a time when a lot of myths about pool are busted and then people who might be hampered by a lot of the bunk that surrounds pool will be free to work on the important things that are needed to become a champion - or at least become as good as their talent and dedication can take them.

You have to understand Dick that for most of us we don't have the type of experience that you and other top notchers have. Our pool experience comes from books and tapes and instruction by people who aren't top notchers. We don't get to spend nights on end battling with the best around and having our game forged by combat. We don't have ten hours a day to spend on endless repetition. So for us we want to try and understand pool in a cerebral way. We want to spend what time we do have trying to "think pool" so that when we do get on the table we can understand what comes instinctively to you.

I hope that you can understand that no one is trying to create champions out of a book. We just like to talk pool in this way. It's all done in the name of better pool.

 

[Patrick Johnson]

You will never convince me that any amount of scientific mumbo-jumbo can elevate someone to succeed at high level pool.

So what? I've never heard anybody claim that discussing pool science will make anybody play as well as you do, Dick, but where's the harm? Telling stories about old pool players won't do it either, but nobody complains when you do that. Different pool players are interested in talking about different aspects of pool.

I have the impression you're a live-and-let-live kinda guy, so your objection to scientific discussion kinda mystifies me. Maybe it isn't for you, but there are clearly some here who enjoy it.

pj
chgo

 

[dr_dave]

Dick,

Why do you think that the discussions are intended to elevate anyone to a high level in pool?

You can take any sports activity and find hundreds of conversations/debates/arguments going on about the science/pseudo-science in the sport.

It's just conversation. We all know that none of this will make someone into a champion and I think that you might have the wrong idea what the goal is for the people who discuss these things are.

Actually the goal in a way is the same thing that you are saying. Pat's goal is to separate hype and myth from reality. Because sometimes the ads in our business do tend a little towards insinuating that if you play with x-product you will get much better. So while you are right that knowledge alone won't make a champion neither will the belief that a cue can produce 25% more spin all by itself. Something that a well known brand had advertised.

I for one, enjoy the conversations about the science of pool. I appreciate that there are people out there willing to put a lot of thought into what's really happening. I like to see the high speed videos and amateur videos of what people are doing and thinking about.

I expect that 2008/2009 will be a time when a lot of myths about pool are busted and then people who might be hampered by a lot of the bunk that surrounds pool will be free to work on the important things that are needed to become a champion - or at least become as good as their talent and dedication can take them.

You have to understand Dick that for most of us we don't have the type of experience that you and other top notchers have. Our pool experience comes from books and tapes and instruction by people who aren't top notchers. We don't get to spend nights on end battling with the best around and having our game forged by combat. We don't have ten hours a day to spend on endless repetition. So for us we want to try and understand pool in a cerebral way. We want to spend what time we do have trying to "think pool" so that when we do get on the table we can understand what comes instinctively to you.

I hope that you can understand that no one is trying to create champions out of a book. We just like to talk pool in this way. It's all done in the name of better pool.

Excellent post.

I would like to add that sometimes improved understanding and knowledge does lead to useful information that can be applied at the table. It can also help somebody learn, teach, and improve more effectively. Also, sometimes physical understanding might help the cue industry create better products.

Bad information and myths can and have slowed progress of the industry and individuals wished to learn and improve at the game. I don't think we need to defend ourselves for trying to help create understanding, even if this understanding can't "create a champion." I think it is ridiculous to even suggest information, knowledge, and understanding can "create a champion." Champion-level pool requires too much feel, hand-eye coordination, visual perception, etc. That kind of stuff can come only with natural talent and many years of successful practice and experience.

Regards,
Dave

 

[Patrick Johnson]

Fading the bet...

Iusedtoberich, here's the donation you asked me to make.

A generous, pool-supporting decision. Thanks.

pj
chgo

 

[iusedtoberich]

Thank you for the eye opening thread!

 

[Alex Kanapilly]

That prompts me to ask - where is Ron Shepard these days? Given up pool, given up posting, or just being anonymous?

I don't know but he was playing pool not too long ago. I met up with him at Pro Tyme in Orland Park near Chicago in September of '07. We played one pocket for a few hours. Very nice guy... and all of that scientific information crammed in his head didn't seem to negatively affect his game.