Is a Straight Stroke All That Important?

ShootingArts said:
PJ,

At least we understand what each other is saying this time which is an advancement over the many years we have tried to talk.
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Yep. And without knives this time! Who'da thunkit? :)

Simply put, the stick is at totally different angles using backhand english and parallel english. Front hand english results in an angle between that created by back hand english and parallel english.
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Disagree (as you know).

Any shot requiring english can be made using any of the three styles of acquiring english.
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Agree, but we differ on how that happens.

Since the angles are different and we have agreed that hitting the cue ball in the same place at different angles gives different results we must be hitting the cue ball at different contact points to get the same results with different angles.
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Or we must be hitting the same contact point at the same angle. This is my belief.

A serious question: Have you ever tried front hand english?
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I choose the amount of tip offset I want and then adjust my cue angle as needed by feel. Sometimes I aim centerball first and then adjust, sometimes I just place my cue pre-aligned (without first aiming centerball).

In front hand english we move the bridge while leaving the grip hand in the same place as no english while setting up.
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That would mean a pivot point of 50 inches or so. Impossible.

You should be able to satisfy yourself that you get the same action off the rail with these two different angles.
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I don't think you can hit the same spot on the rail and get the same spin by hitting two different spots on the CB.

I have already performed a simple test for myself simply hitting a cue ball into the same point on the rail using back hand, front hand, and parallel english, three different angles as I apply them. All can produce identical results as closely as can be measured on a pool table.
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I'll do the same test and report my results. Will you do a simple one that I design?

pj
chgo
 
it would seem we all argue about all or nothing. Perhaps a true straight stroke is impossible but by continually seeking the straight stroke players likely get small improvements (or large ones for some players). it's all a matter of degrees.
 
sure if it doesn't involve hours

Patrick Johnson said:
Yep. And without knives this time! Who'da thunkit? :)


Disagree (as you know).


Agree, but we differ on how that happens.


Or we must be hitting the same contact point at the same angle. This is my belief.


I choose the amount of tip offset I want and then adjust my cue angle as needed by feel. Sometimes I aim centerball first and then adjust, sometimes I just place my cue pre-aligned (without first aiming centerball).


That would mean a pivot point of 50 inches or so. Impossible.

A pivot point of over fifty-nine inches is quite possible with my 60" cue. It may be impossible for a pivot point that long to work as you desire but that is a far cry from being physically impossible. With Earl's cue I could have a six foot pivot point! It is also physically possible to have a zero distance pivot point. By shifting both bridge and grip the effective pivot point doesn't even have to be anywhere on the cue, it can be in front of it or behind it.


I don't think you can hit the same spot on the rail and get the same spin by hitting two different spots on the CB.

This is our basic disagreement. Without this being true there would be only one possible english as you contend regardless of how you arrived at that line. Obviously I can't prove it but I suspect that when setting up for english by feel you are using a fairly unique angle yourself, a combination of front hand and back hand english which matches none of the conventional angles. This can work very well but definitely involve a lot of HAMB.


I'll do the same test and report my results. Will you do a simple one that I design?

Indeed I will if you do the test I outlined. Assuming a similarly simple and inexpensive test.

pj
chgo
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One thing I think it is fair to accept considering any of these results based tests: Once we establish a baseline, for example the amount of english a certain backhand english gives a cue ball as determined by where it hits the rail, then if another method gives both more and less spin in tests we will accept it is possible for it to give identical spin also. Our testing is imprecise at best but going beyond simple testing involves both dollars and a lot of time I don't have to spend on this. I'll have to drop in on a pool table away from my usual haunts to even do a simple test for you, no time to spend a day playing pool for quite awhile, a very large rush project is eating up my summer.

Hu
 
Me:
That would mean a pivot point of 50 inches or so. Impossible.
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Hu:
A pivot point of over fifty-nine inches is quite possible with my 60" cue. It may be impossible for a pivot point that long to work as you desire but that is a far cry from being physically impossible.
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I meant that no real cue really has a pivot point that far from the tip. Your claim (that different squirt compensation methods produce difference cue angles and tip/CB contact points for the same results) implies that the pivot point for a cue moves depending on the squirt compensation method you use. It doesn't.

Me:
I'll do the same test and report my results. Will you do a simple one that I design?
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Hu:
Indeed I will if you do the test I outlined. Assuming a similarly simple and inexpensive test.
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Cool. I'll think about how to keep it simple and get back to you. Meanwhile I'll do yours (probably tonight).

pj
chgo
 
just a quick note

Patrick Johnson said:
I meant that no real cue really has a pivot point that far from the tip. Your claim (that different squirt compensation methods produce difference cue angles and tip/CB contact points for the same results) implies that the pivot point for a cue moves depending on the squirt compensation method you use. It doesn't.


Cool. I'll think about how to keep it simple and get back to you. Meanwhile I'll do yours (probably tonight).

pj
chgo
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PJ,

As so often we mean different things by the same word. I am talking a literal pivot point, the axis the cue or a line rotates around, the axis. You are talking about the pivot point used to cancel out forces using back hand english which we will agree is fixed for any exact situation, same shaft, same shot, same everything. Even this pivot point isn't a perfectly fixed pivot point. If we split hairs since both force and angle vary from shot to shot the pivot point is always slightly different even using backhand english. I haven't given it any real thought but the exact pivot point(the word as you are using it) that would cancel out forces would be different using front hand and back hand english. Front hand english has only roughly one third the angle of back hand english.

Hu
 
ShootingArts said:
...the exact pivot point (the word as you are using it) that would cancel out forces would be different using front hand and back hand english.
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By "cancel out forces" I assume you mean "compensate for squirt" - and I don't believe your statement is true.

BTW, the simple test I'll propose won't test the above directly - it will be designed to show that you can't get the same CB direction and spin by hitting the CB on different spots and/or at different angles. I believe that's what you claim to be able to do.

pj
chgo
 
ShootingArts said:
You were not in error or rude. In trying to explain the difference between backhand and parallel english I was talking about initial lines of force you were talking about something different. I didn't explain myself as well as I could have. I have a bit of a problem writing. As a former technical writer and illustrator of procedures in a nuclear power plant I have been trained to painfully dot every I and cross every T. When I try to be less wordy I tend to do a poor job of explaining myself. You have been far from rude also. Those that feel any difference of opinion is rude are those that have made technical discussion almost impossible on AZB. It is very nice to have a pleasant discussion with someone. As we continue we aren't really that far apart.
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Many thanks for those sentiments and not getting your feathers ruffled over this, especially since you're currently engaged in a two-front argument. You express things quite well as a matter of fact, and which of us doesn't put things ambiguously at times?

ShootingArts said:
Getting back to the discussion of this little shot, I would say that the swoop is far faster than the forward motion. Put another way, the swoop is the predominant motion in the shot. Another factor that might have made this effective is that back then I shot with tips that were about 12.75mm, flat across the center with a lightly radiused corner. My cue shop is in mothballs at the moment or I would like to shape a tip like this to play with awhile. The soft tips I commonly used, the large gripping surface, and the comparatively slow forward speed were probably all significant factors in that stroke. Executed perfectly there was no comparison to how much spin you could get from this shot as compared to what you could get with english before miscueing, I'm talking about the cue ball going straight into the rail and coming off at maybe a sixty to seventy-five degree angle from the angle it contacted the rail on. It compared to Mike Massey playing finger pool with the huge spin he gets.

Hu
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I agree that the shot your talking about is much more plausible. But I have to say that I'm still highly skeptical that you can't accomplish the same thing with a straight stroke at a larger offset from center. To my way of thinking, the maximum spin/speed ratio is set by the maximum coefficient of static friction (COF), which is the largest non-slip ratio of the tangential friction force to the force acting normal to the surface of the cueball. This, methinks, is principally determined by the nature of the materials. It's not obvious why it would change because the tip is coming in at a different angle (velocity-wise) and maybe taking on a little bit different shape because of it?

Jim
 
just a guess

Jal said:
Many thanks for those sentiments and not getting your feathers ruffled over this, especially since you're currently engaged in a two-front argument. You express things quite well as a matter of fact, and which of us doesn't put things ambiguously at times?

I agree that the shot your talking about is much more plausible. But I have to say that I'm still highly skeptical that you can't accomplish the same thing with a straight stroke at a larger offset from center. To my way of thinking, the maximum spin/speed ratio is set by the maximum coefficient of static friction (COF), which is the largest non-slip ratio of the tangential friction force to the force acting normal to the surface of the cueball. This, methinks, is principally determined by the nature of the materials. It's not obvious why it would change because the tip is coming in at a different angle (velocity-wise) and maybe taking on a little bit different shape because of it?

Jim
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Jim,

It might come down to the efficiency of force transfer while in contact and the length of time in contact. The further out we try to hit with english the less surface area we have to work with of course and this loss of surface area increases rapidly near the limits of being a miscue. A swipe starts with much more surface area than hitting with maximum english and has already started the ball spinning to some degree before it reaches the furtherst limit of contact, perhaps that earlier spin allows grip to be maintained a little longer since the cue ball and tip are starting to move in a similar direction. All just speculation, I don't know the nuts and bolts of why it works.

An area I don't wish to take this thread into after already derailing it pretty thoroughly into one direction but I have always wondered about the actual degree of slippage between a cue tip and cue ball. Is a hard tip or a soft tip more effective? I can make an excellent argument for a hard tip or a soft tip, both have advantages and disadvantages but it seems we could test with a mechanical set-up and answer once and for all if either was better.

If we had hard numbers for the COF of a cue tip contacting a cue ball at specific angles we would be well on our way to having a basis for saying this or that method is best. I have no idea if we get five percent slippage or fifty percent just to throw two numbers out. I feel sure that back hand english has the most slippage, front hand somewhere in the middle, and parallen english the least simply because of the different angles hitting the cue ball. Is this a few percent difference or maybe fifteen, twenty percent or more? If you are interested we could start another thread solely about slippage with different tips and angles. Of course it would start with that, who knows where it would end up? :)

Hu
 
I don't know a person that plays well with a crooked stroke. It may look crooked but it isn't. I can't recall one person.
 
Jal said:
I might be being a bit rude by challenging your direct observation - it's unclear at this point which of the above situations you've generally been referring to. At times I've felt that I'm getting more spin by swiping, but given my understanding of the physics, such as it is, I don't even believe my own experience (i.e., I think I was simply making contact farther off-center).

Jim
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Jal,
If you do an Einstein "thought experiment," and just sit an imaginary little man at the end of the cue tip; at the moment of impact he will see the same thing whether you swoop or use parallel English (though with swooping you will be setting up the cue along a different shot line than that seen at impact). If the cue of the "swooper" and the cue of the parallel English zealot end up at the same place at the moment of impact, it is hard to see how there could be much if any difference to the cue ball.

If the contact time with the cue ball is as small as Dr. Dave claims, then these are just procedural differences - all the cue ball is going to understand is speed of the cue, location of impact, and direction of the force delivered at impact. It shouldn't matter how you got there if contact time is that small (any swooping during the moments of contact might add some effect, but with this time being so short it couldn't be much). JMO...I would be interested to hear what you think.
 
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spanish-sky.jpg


What do you see?
 
Grab a basketball, volleyball, or similar sized ball

For all of those that think the stroke angle is the same, as usual we can exaggerate things and make them clearer. Grab a large ball, volley ball sized or bigger, and lay it on the floor or a pool table if you have one at home.

Lay a cue stick pointing at it dead center, representing a standard centerline shot. Now grab the stick one foot from the tip and hold it in place as the bridge for back hand english. Grab the middle of the wrap area and swing the cue stick until the tip points at the halfway point between center ball and the edge. This illustrates backhand english. Note that line and return to the center ball line.

This time grip the cue in the middle of the wrap area and holding this in place, swing the cue tip to the same halfway point on the cue ball. Note this line, this represents front hand english. Return the cue to the original center ball location.

Now move both the bridge and the grip hand in the same direction to move the tip to the same point halfway between the center line of the cue ball and the edge. This represents parallel english.

By using the large ball anyone should be able to see that we are looking at three distinct angles. If you can't resist poking that big ball with a cue stick you will find that only slight adjustments to the contact point are required to send the ball to the same location using any of these three angles.

Hu
 
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Williebetmore said:
Jal,
If you do an Einstein "thought experiment," and just sit an imaginary little man at the end of the cue tip; at the moment of impact he will see the same thing whether you swoop or use parallel English (though with swooping you will be setting up the cue along a different shot line than that seen at impact). If the cue of the "swooper" and the cue of the parallel English zealot end up at the same place at the moment of impact, it is hard to see how there could be much if any difference to the cue ball.
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Willie, I essentially agree with you, particularly when considering shots at typical speeds (not extremely slow) and tip offsets not just slightly off-center. But I think you have to grant a little difference between swooping and a normal stroke.

As the cueball starts to spin up during contact, it has to push the tip sideways. This takes some force, and the same force acts "backward" on the cueball (action/reaction), thereby producing squirt. If you swipe across the contact point, you've pre-supplied some or all of the sideways motion of the tip during your stroke. The cueball then doesn't have as much (or any) work to do in pushing the tip aside. In principle then, you can eliminate squirt and there'll be a gain in spin rate because of this - but only a tad since squirt reduces the spin rate by only a few percentage points. However, if you look at how fast the tip has to be moving in the sideways direction just to accomplish this (completely eliminate squirt), I think it's all but impossible at typical shot speeds, particularly if you're generating the sideways motion with just a flick of the wrist.

Williebetmore said:
If the contact time with the cue ball is as small as Dr. Dave claims, then these are just procedural differences - all the cue ball is going to understand is speed of the cue, location of impact, and direction of the force delivered at impact. It shouldn't matter how you got there if contact time is that small (any swooping during the moments of contact might add some effect, but with this time being so short it couldn't be much). JMO...I would be interested to hear what you think.
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You're absolutely right. Once the tip reaches the ball, there's essentially nothing more you can do to affect the outcome. A part of the reason is what you said about the contact time, and a corollary is that the forces acting between the tip and the ball are much larger than anything you can supply with your stroking hand/arm. It is true, obviously, that the tip-ball forces are the result of what you did with your stroke before contact, but, you have something like a quarter to a half second to get the cue up to speed to produce them. The millisecond (or two, or three ...) of contact time just isn't enough to do anything of significance, as you point out. But if you start the swoop well before contact, that's different...although the gains are still going to be meager, per above.

Hu was talking mainly about a very slow shot, say, about 1 mph. There (without having done the numbers), I believe you could see some noticeable gains in spin compared to a straight stroke (same tip offset at contact), depending maybe on how far from center you make the contact. An obvious case is hitting center ball while swiping; you're going to get some spin, and "negative" squirt to go along with it.

Jim
 
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