Follow English????

[FLICKit]

Hmmm.... In getting a bit nuance... Upon reflection a subtle twist to the conversation may be in relation to followthrough (distinct from accelerated stroke).

Since the high speed video does demonstrate a stopping of the cue stick upon impact, it could be concluded that technically the followthrough comes afterwards, thus having no impact.

EXCEPT that the followthrough could have an impact on the stroke leading up to that point. In other words, since basically nobody purposefully intends to stroke their shot such that they intentionally stop at impact, and then purposefully accelerate afterwards... What's humanly natural is to generate a stroke such that the end result has followthrough. This natural stroke approach could impart effects before or during contact, and thus exude all of the effects eluded in the previous post.

 

[DoomCue]

OK Bob, here we go. You and I had a bit of a tussle about this not too long ago, but it was related to draw instead.

In that discussion you pointed out that the stick basically stops at the point of impact. I disagreed, but the high speed video clearly showed basically a stopping motion and a very very short moment of impact between the stick and the cue ball. So, I'll admit to that and concur, and I've learned something from it. I think deep down, we're both similar in that we'd rather get to accurate information rather than just bravado of having to appear "right".

Now first of all, I have a very "strong opinion" that stroke matters, and matters quite a bit. I also believe that many expert players will agree with that "premise" just from their personal experience. The cue ball can be made to act quite differently depending on the type of stroke imparted.
Also I "suggest" that the most important factor relating to draw and follow is SPIN. If there is ample reverse spin on the cue ball after contacting the object ball, then it WILL draw back. And, if there is ample top spin on the cue ball after contact, then it WILL roll forward. Of course must also account for top spin generated from the friction between the cue ball and the felt. -- Excluding all other unnecessary factors -- And so, the type of stroke can impact the amount of spin imparted.

I also know that you, and a group of teachers believe that the high speed videos conclusively prove that stroke doesn't matter. And you infer that this is conclusive evidence based on the essentially stopping motion of the cue and the relatively small moment of impact between the cue ball and the stick.

Accepting your premise, it seemed reasonable at first and for awhile. After a period of time, I then came to the realization and surmised that the videos that I saw need surprisingly much more detail in order to be conclusive.

-------------------------------------------------------------------
Obviously we know that tip compression and tip decompression are a part of what occurs. Unfortunately this adds additional complexities which I'm not sure that we can just rule out.

Some factors need to be visible and distinguishable, or even better definable and measurable.

So, we have cue speed at the moment before impact. And the type of stroke (accelerated, decelerated, ...) Would be useful if visible/measurable here.

Then we'd need to know tip compression and its rate. Would also be useful if visible/measurable. And would need to know if type of stroke (accel., decel...) had any impact on the compression. Is the compression rate faster/slower/no difference? Is the compression deeper/shorter/no difference? Possibly even does it remain compressed for a longer/shorter/no difference period of time before it starts decompressing?

Might even need to know what's happening to the stick while the tip compression is occuring:
Change in speed of the stick during the tip compression, during the tip decompression, ...
Also flex factors of the stick (is it bending, how much, how fast, how long?) Is this any different depending on the type of stroke?

Gonna assume that all the factors of force and mass exerted (ie from the human) on the stick can be consistent and thus irrelevant.

All the information that we gathered during "compression" might also need to be gathered during "DEcompression", unless can be positive that contact is over and thus decompression has no relevancy...

Lastly, at what point is the impact over? During the tip compression, tip decompression, after tip decompression,...? Does the stick speed actually reach 0 or some speed very close to 0? And what is happening to the stick in this time period? And is there any change in this depending on initial stroke?

Obviously the stick then begins to accelerate in order to go from 0 back to something close to its original speed before impact for either a long distance (follow through), short distance or whatever... This part is what derives those conclusions that the stroke has no impact. And that the moment of impact is so short that stroke impact is not relevant.

I know this might sound too exhaustive, and maybe even too extreme for some. But, I believe that this is what it's going to take in order to prove it. Without that level of clarity, then I understand that people will come to conclusions based on what they have, which may be all we can do at this time.

There may be more to look through for more definitive results...
On the surface, one of the things I notice from Dave's examples is that his followthrough strokes produce more dramatic results. He's getting more draw from his followthrough strokes than his punch strokes.

Question: have you seen anywhere in this thread where someone has said stroke doesn't matter?

Question: where have you seen that "the cue ball can be made to act quite differently depending on the type of stroke imparted?"

Question: what are some different "types of strokes?"

Question: how do you make the leap in logic from "SPIN" to your declaration that "the type of stroke can impact the amount of spin imparted?"

Question: do you know any pool instructors who believe that strokes don't matter?

Question: do you think it's possible there may be other factors involved in Dr. Dave's follow-through examples? For instance, tip offset and tip velocity?

Maybe it's just the translation from spoken to written word, but I don't believe you'd said much in this long discourse, other than to misunderstand what others have said and make wild leaps in logic based on those misunderstandings. We have a saying in the IT world - "He knows enough to be dangerous." Unfortunately, you are missing the forest for the trees. Does the CB care about tip compression BEFORE, AFTER, or DURING contact? If you think anything other than DURING contact, I'm not too sure that it matters what anybody tells you.

-djb

 

[DoomCue]

Hmmm.... In getting a bit nuance... Upon reflection a subtle twist to the conversation may be in relation to followthrough (distinct from accelerated stroke).

Since the high speed video does demonstrate a stopping of the cue stick upon impact, it could be concluded that technically the followthrough comes afterwards, thus having no impact.

EXCEPT that the followthrough could have an impact on the stroke leading up to that point. In other words, since basically nobody purposefully intends to stroke their shot such that they intentionally stop at impact, and then purposefully accelerate afterwards... What's humanly natural is to generate a stroke such that the end result has followthrough. This natural stroke approach could impart effects before or during contact, and thus exude all of the effects eluded in the previous post.

"Technically" the followthrough comes afterwards? "Technically?" C'mon, why do you think it's called FOLLOW THROUGH?

How in the hell could effects be imparted BEFORE contact? Have you ever been in a fight? Did your nose bleed BEFORE you got hit?

-djb

 

[FLICKit]

Question: have you seen anywhere in this thread where someone has said stroke doesn't matter?

Question: where have you seen that "the cue ball can be made to act quite differently depending on the type of stroke imparted?"

Question: what are some different "types of strokes?"

Question: how do you make the leap in logic from "SPIN" to your declaration that "the type of stroke can impact the amount of spin imparted?"

Question: do you know any pool instructors who believe that strokes don't matter?

Question: do you think it's possible there may be other factors involved in Dr. Dave's follow-through examples? For instance, tip offset and tip velocity?

Doomcue, it looks like your post misrepresented alot of information above...

Most of your stroke questions are answered by the following statement:

And would need to know if type of stroke (accel., decel...) had any impact on the compression. Is the compression rate faster/slower/no difference? Is the compression deeper/shorter/no difference? Possibly even does it remain compressed for a longer/shorter/no difference period of time before it starts decompressing?

Compare apples to apples... if you look closely Dr. Dave accounts for different tip offsets and tip speeds... and also grips..

There may be more to look through for more definitive results...
On the surface, one of the things I notice from Dave's examples is that his followthrough strokes produce more dramatic results. He's getting more draw from his followthrough strokes than his punch strokes.

I will respond more thoroughly when I have more time... I apologize for the brevity...

 

[Rasta]

Sorry Rasta, I was mixing horizontal effects with vertical effects in that paragraph, because the mechanisms are the same, only the direction changes. I think we do understand each other and I agree that the vertical motion you've been refering to has a different cause (pendulum arc) than the one I've been refering to (cueball rotation pushing the tip further off-center).

But I see them as connected for the purpose of understanding what effect the motion you're refering to has on the cueball. At large tip offsets, such as .4R, I don't believe you can get the tip moving away from center via your motion (vertical swoop) fast enough to keep up with the ball rotation. But you do get some vertical squirt relief because you're doing with your stroke what the cueball's rotation does anyway, but at the cost of squirt. And since variations in squirt make little difference to the ball's acquired spin, it seems unlikely that the swooping makes any significant difference to it. At small tip offsets it should have a much greater effect.

I don't believe them to be connected in such a manner that they can be modeled the same way. Shaft deflection and cue ball squirt cause translational motion of the CB and the end mass of the shaft. The vertical motion of the cue tip due to the pendulum swing causes rotational motion of the cue ball.

I agree that at smaller tip offsets the vertical motion from the pendulum swing will have a greater effect. However, I believe this is due more to properties of sines and cosines, and less from the vertical component of the tip velocity.

Incidentally, the vertical tip velocity can be increased by increasing bridge length, since it is the bridge hand that acts as the fulcrum. However, this decreases the mechanical advantage of the cue as a lever.

Since I believe what I said above, I suspect that what happened is that you began hitting lower on the cueball.

I'll admit that I'm not absoulutely sure of any of this, but am more or less persuaded by the argument. Some experimentation would help.

Jim

It is indeed possible that I was hitting the cueball lower. I'm hesitant to jump to that conclusion, however, due to the experience of the player that showed me the concept, and his experience with the effects of changing grip positions.

I will also admit that I am not absolutely sure of any of this any longer! Some experimentation would indeed be very helpful. I will also try to obtain a more thorough mathematical model, though that will take a bit of time.

I would like to add that I have thoroughly enjoyed this debate. Some of those folks over in NPR could learn a few things from us about keeping things civil!

Have a great weekend.

Good Rolls,
Rasta

 

[seymore15074]

I can draw & stop the CB & I am making some progress on making the CB deflect off the object ball &/or rail at predictable angles.

I am baffled when I try to make the CB follow the object ball. I hit above the equator of the CB, but the results are erratic. Help?!!

Follow is hard not to get. I'd bet you are getting it fine... Shoot a straight in shot and watch the cue-ball go forward...I'm sure this works, right?

Now, the thinner you cut a ball, the less the follow will change your angle...if you cut a ball 90-degrees with follow, nothing really changes as far as angles go.

The first thing to recognize is that the cue-ball comes off of the object ball at a 90-degree angle using a kill shot (the cue-ball is sliding, NOT rolling; use the 9-ball as the cue-ball to check this out). Look at where the cue-ball will come off at a 90, and now play the ball high. The cue-ball will "tighten up" this angle and come off at less than 90-degrees. That is the opposite of draw...

I'm sure it seems erratic, but just keep comparing your results to a 90-degree tangent line, and you'll know what's up in no time.

I suspect that you "follow" every shot, and that is why you do not see much of a difference. 90-degrees doesn't just happen, you have to make it happen...other than that, if it's not draw, it's follow! By this, I mean that the cue ball picks up follow (starts rolling forward) from the friction on the cloth...I could talk about this for hours, if you want more info just drop me a message...

Now, if you posted: "I can only follow a ball up, but I can't get extreme follow that makes my cue-ball dance around, curve, and speak," then everyone else should post. lol (no offense anyone, btw)

 

[Jal]

...Since the high speed video does demonstrate a stopping of the cue stick upon impact, it could be concluded that technically the followthrough comes afterwards, thus having no impact.

Hi Flickit,

The cue stick, as a whole, doesn't stop at impact. It never slows down to less than about half its pre-impact speed. This is because it's about three times heavier than the cueball. Yes, the outer surface of the tip does come to a halt, momentarily. And the portion of the shaft near the tip does slow down more than the rest of the cue. But taken as a whole, the cue never stops.

EXCEPT that the followthrough could have an impact on the stroke leading up to that point. In other words, since basically nobody purposefully intends to stroke their shot such that they intentionally stop at impact, and then purposefully accelerate afterwards... What's humanly natural is to generate a stroke such that the end result has followthrough. This natural stroke approach could impart effects before or during contact, and thus exude all of the effects eluded in the previous post.

Absolutely. It's similar to a baseball hitter trying to beat out a ground ball. Technically, it doesn't matter if he runs past first base by 2', or 20', or stops on the bag. But it is important as an indicator of what he was doing up until reaching first base.

When someone makes a point that follow through doesn't matter, they mean it in the technical sense.

Jim

 

[Bob Jewett]

... In that discussion you pointed out that the stick basically stops at the point of impact. I disagreed, but the high speed video clearly showed basically a stopping motion and a very very short moment of impact between the stick and the cue ball. So, I'll admit to that and concur, and I've learned something from it. ...

I have never claimed such a thing, nor do I believe it, nor was it shown on the Jacksonville video. You may want to review my on-line article about what happens to cue stick speed during the entire shot. It is available at http://www.sfbilliards.com/jax_bd150.pdf as the last page of the PDF.

If we start from false premises we are unlikely to come to correct conclusions.

 

[FLICKit]

I have never claimed such a thing, nor do I believe it, nor was it shown on the Jacksonville video. You may want to review my on-line article about what happens to cue stick speed during the entire shot. It is available at http://www.sfbilliards.com/jax_bd150.pdf as the last page of the PDF.

If we start from false premises we are unlikely to come to correct conclusions.

Bob,

Thanks. That does clear up quite a bit.
I apologize for misrepresenting you in any way.

It seems that I had read in this forum in another thread that someone mentioned that the cue stick stops at impact (I'll likely look it up and get more clarification at a different time). The high speed videos that I looked at, showed some evidence to support that claim. Not having any evidence to dispute it, I thus had to accept it.

These high speed videos are more in-line with my original hypothesis. Clearly the cue doesn't stop at any point during contact. I can accept that much more readily.

I have some additional questions which unfortunately will have to be for a later time as well...

 

[renard]

I can draw & stop the CB & I am making some progress on making the CB deflect off the object ball &/or rail at predictable angles.

I am baffled when I try to make the CB follow the object ball. I hit above the equator of the CB, but the results are erratic. Help?!!

Your backhand is too far forward on the cue. This causes you to A) Shorten up your follow thru... and most importantly B) Lowers your tip at impact because your backhand is rising up at impact. Thus you are not hitting the cueball as high as you think you are.

That explains why you can draw but not follow...

 

[berlowmj]

Your backhand is too far forward on the cue. This causes you to A) Shorten up your follow thru... and most importantly B) Lowers your tip at impact because your backhand is rising up at impact. Thus you are not hitting the cueball as high as you think you are.

That explains why you can draw but not follow...

Thank you. I will experiment with my backhand. I thought that the major issue for my backhand was to place my grip on the cue so that my forearm & tricep region maintain a 90 degree angle.

 

[renard]

Thank you. I will experiment with my backhand. I thought that the major issue for my backhand was to place my grip on the cue so that my forearm & tricep region maintain a 90 degree angle.

You are correct with the 90 degree angle, but try this: Line up as you normally would with the tip addressing the cueball and freeze everything. Look back and ensure that there is a 90 degree. Then with everything locked frozen slide everything forward til you move the cueball. With the pendulum at its lowest point is when contact should be made.

The reasoning for this is that some people when they are down with thier chin on the stick they percieve the tip as almost touching the cueball. When in fact is actually farther away (up to 2 inches). To compound this they drop or raise thier elbow during the stroke. The stoke is the forearm nothing else. Why add more moving parts that can change the outcome of a simple to and fro movement. Again video or a mirror works wonders...

One guy described a player he was watching as having a Monkey motion stroke. He said, "This guy has added so much monkey motion in his stroke that it reminded him of the board game, "Mousetrap" or a "Tom a Jerry cartoon." He added, "Why try and build a better mouse trap? Keep it simple." Made since to me.

 

[DoomCue]

Thank you. I will experiment with my backhand. I thought that the major issue for my backhand was to place my grip on the cue so that my forearm & tricep region maintain a 90 degree angle.

The angle between forearm and upper arm is not important - it may or may not be 90 degrees (it usually isn't). Whether it is or isn't depends upon your body type. Regardless of body type, the important angle is between the forearm and the floor. The forearm should be perpendicular to the floor (90 degrees) when you contact the cue ball. In order to maintain this angle, your grip position will need to change depending upon your bridge length. If you have a short bridge length, you'll need to bridge closer to the joint of the cue to achieve that perpendicular state at contact. If you have a long bridge length, you'll need to bridge closer to the butt.

Again, I strongly suggest seeking out proper instruction - a good instructor will be able to show you how to make the corrections in your stance and grip. Look for an instructor who does video analysis - slow motion video can really show where your form is breaking down.

-djb

 

[Stretch]

For follow shots i always use an open bridge with a level cue. On full ball hits or nearly full ball hits a naturally rolling cb will roll through the space that the ob occupied. How far it rolls after contact is then just a matter of speed control, but very predictable with a little practice. It's this predictablility which makes this a vital shot to know.

Being able to stroke a naturaly rolling cb is the trick. It relates to speed and distance. For instance if the ob is just 6 or 8 inches away, but you need 2 feet of follow, this cannot be done with a naturaly rolling cb. You must hit it a lot harder so that it is sliding into the ob with topspin. As we know a sliding cb will have a stun effect. With no top spin it will stop or stun along the tangent line if not dead straight. then it's a function of how much residuale topspin is left over to take it to where you want it.

If you need 2 feet of follow but your cb is 4 feet away then a naturally rolling cb can easily get you there because the distance insures a good forward roll so speed of hit is basicaly your only concern.

Sometimes you need to follow only a short distance on a long shot. This is where it gets tricky because then you'd have to slow roll the cb so slow that your ob might not make it to the pocket, or the cb may drift off line. In cases like this you need to use a draw stroke and hit it so that the back spin wares off and forward roll begins just pryer to contacting the ob. I belive the term for this is called a stun runthrough.

As you can see it's a very complex issue. You can learn alot by setting up shots that you can get the leave you want with a soft hit, then try and get the leave you want with a hard hit. You will need this knowledge for advanced play.

Stretch.

 

[FLICKit]

Bob,

If I understand correctly the results of the Jacksonville Experiment link...


It looks like the images in Fig 4 may have generated an extra 3 frames of contact with the cue ball likely resulting from compression of the tip or hand. This would be followed by 8 frames of compressed contact, then 4 more frames of decompressing contact. Or were the actual results more visible and slightly different, than what appears in this version of the photograph due to the detail level?
(BTW: pretty cool display)

"De Jagar had a theory that the most spin can be imparted if the cue tip is actually accelerating at the moment of impact. Jewett doubted that a human being can accomplish that. Years of debate ended in about an hour when tried the experiment. No matter how anyone stroked, the best we could do was to have the cue stick move at constant speed for the last few inches before it hits the ball."

That quote is quite shocking that you guys were unable to generate an accelerating stroke into impact. Obviously acceleration has to do with a change in velocity (a=delta v/s), so with such a miniscule period of time, creating a change in velocity would have some difficulties. But, nonetheless you were able to generate some quite noticeable changes in velocities at other parts of the stroke as exhibited in diagram 7. So, it would seem that even if you had to resort to setting aside any principle of a relatively level cue at the point of contact, just for the sake of ensuring some acceleration, at least that would seem plausible.

Even so, were there any conclusions which could be drawn from a stroke which you or De Jager felt like or imagined was an accelerated stroke?

For example, could attempt to generate the same speed (ie 1.9 meters/second) with not only a 22 cm backstroke, but a 5 cm backstroke, and an elongated backstroke. These would be changes in acceleration (from a slightly different context). Just for the purpose of measuring the rotation caused by each.

Maybe even add in some similar experiments with different followthrough stroke lengths...

Then add in the graph paper as shown in Fig. 2 (demonstrating rotation resulting from throw). This could produce some measurable results of rotation from those various types of strokes.
Note: would probably want the graph paper to show both sides of the ball, if possible.


This explanation may not sound clear, so I've put this down here.
Obviously the robot or human are able to accelerate in the early parts of the stroke (once again as demonstrated by diagram 7). If you were able to insert a piece or extend the device (for simplicity/imagery sake let's say an 8 inch plank) between cue stick and hand (human or robot), then could have acceleration to impact, and also have a relatively level cue.
Now, as I understand things, this may not have been feasible to do, because for time and expense reasons your crew were maximizing utilization of the camera time. Thus didn't have alotta time altering or improvising solutions...

Also in reference to Diagram 7
- At 18 cm it shows a dot which seems to fall outside of the reasonable margin of error... Any idea of what that is...
- Before the big sudden drop (presumably impact), at 20-22cm it shows 3 dots in a line downwards, is this as a result of compression?


If there is anything that I need to clarify, please let me know...

 

[Bob Jewett]

.... That quote is quite shocking that you guys were unable to generate an accelerating stroke into impact. ...

The thing is that it is very unnatural to be significantly accelerating when you hit the cue ball. It is a very inefficient and inaccurate (speed-wise) way to hit the cue ball. If you hit the cue ball at peak acceleration, it will only go at half the speed as at zero acceleration (when peak stick speed occurs). I think that anyone with a good stroke has learned this intuitively. It is the easy, efficient and accurate way to hit the cue ball.

 

[Bob Jewett]

... Obviously the robot or human are able to accelerate in the early parts of the stroke (once again as demonstrated by diagram 7). If you were able to insert a piece or extend the device (for simplicity/imagery sake let's say an 8 inch plank) between cue stick and hand (human or robot), then could have acceleration to impact, and also have a relatively level cue.
Now, as I understand things, this may not have been feasible to do, because for time and expense reasons your crew were maximizing utilization of the camera time. Thus didn't have alotta time altering or improvising solutions...

Also in reference to Diagram 7
- At 18 cm it shows a dot which seems to fall outside of the reasonable margin of error... Any idea of what that is...
- Before the big sudden drop (presumably impact), at 20-22cm it shows 3 dots in a line downwards, is this as a result of compression?... .

All of the speed profile measurements were taken with human shooters. At that time the Predator robot was not a good approximation to a human stroke because the grip was too firm.

The main problem with the week of taping that we did (12-16 hours per day) is that we did not have time to interpret the results in between and figure out other things to do. Also, fatigue set in after a few days. There are quite a few other measurements we could have done in retrospect.

As far as the out-of-bound dot on the plot, the way the time/speed/distance measurement was done was by taping a piece of graph paper onto the stick and video taping the paper during the stroke. This necessarily leads to errors in measurement when trying to extract the data especially at times of high acceleration. The smooth line is the artist's concept of what the curve was like. The actual data points are also there so you can decide for yourself whether the drawn curve is reasonable. Not included are the estimated errors for each point.

A better way to have made the measurement would have been to mark and record the shaft so a much tighter camera angle could have been used on finer gradations and to have a higher frame rate.

 

[CoryNYC]

I didn't see anyone post this one, have you thought about your angle? if you get too steep, you will not be able to follow because you're hitting down on the ball not through it. Flatten your cue, you'll see what I mean.

 

[CoryNYC]

I didn't see anyone post this one, have you thought about your angle? if you get too steep, you will not be able to follow because you're hitting down on the ball not through it. Flatten your cue, you'll see what I mean. You can also try stroking up, until you get the hang of it.