why ain't my tangent lines tangent?

[ShootingArts]

In an effort to start some deeep meaningful pool related discussion on the front page, why ain't my tangent lines tangent?(note matching title!)

If I shoot slow to very moderate speed the cue ball does go off on the expected tangent. However with medium or firm speed the cue ball either carries forward a bit before taking off on the tangent or it comes off the object ball at slightly less than 90 degrees. A very slight touch of draw corrects this and I do make most of my billiards but the question remains why do I need that slight draw?

Eyeballs in need of recalibration? Vertical or angular?

Simply the nature of tangents?

Somebody been throwing bounce sheets in the ball cleaner again?

Hu

 

[pulzcul]

Possibly a weight difference between cue ball and object ball.Very evident in bar balls. The heavier cue ball overpowers the tangent line. Don

 

[ShootingArts]

good thought

Possibly a weight difference between cue ball and object ball.Very evident in bar balls. The heavier cue ball overpowers the tangent line. Don

Don,

That is a good thought but this is a consistent issue playing on the nine footers at the pool hall with over a dozen sets of balls in rotation.

Hu

 

[jsp]

In an effort to start some deeep meaningful pool related discussion on the front page, why ain't my tangent lines tangent?(note matching title!)

If I shoot slow to very moderate speed the cue ball does go off on the expected tangent. However with medium or firm speed the cue ball either carries forward a bit before taking off on the tangent or it comes off the object ball at slightly less than 90 degrees. A very slight touch of draw corrects this and I do make most of my billiards but the question remains why do I need that slight draw?

Eyeballs in need of recalibration? Vertical or angular?

Simply the nature of tangents?

Somebody been throwing bounce sheets in the ball cleaner again?

Hu

Throw and the fact that the balls aren't perfectly elastic are the reasons why the balls will depart slightly less than 90 degs from each other.

The throw effect should actually increase with speed, such that you'd notice the balls depart less than 90 degs the slower you hit it. Of course unless you use a bit of sidespin to compensate.

Though, I think the effect of the balls' inelasticity would increase with higher speeds. So this is probably what you're observing. EDIT: Though, I doubt any effects would be significant enough to notice, unless you're playing a table-length billiard.

 

[Patrick Johnson]

Hu:
...why ain't my tangent lines tangent?

Let's dispense with the basics first. (I assume you're not talking about playing with a mismatched cue ball.) Do you know that the cue ball will only follow the tangent line if it hits the object ball with no forward or backward rotation at all (i.e., sliding on the cloth)?

pj
chgo

 

[Actionhound]

Could be a number of things... maybe you havent found your "center ball" that goes with your stroke (some poeple's centerball is different than others by a small amount) or maybe your not stroking all the way through on your shot... i dont really know because im not an expert but this is my only answers.

 

[pulzcul]

Let's dispense with the basics first. (I assume you're not talking about playing with a mismatched cue ball.) Do you know that the cue ball will only follow the tangent line if it hits the object ball with no forward or backward rotation at all (i.e., sliding on the cloth)?

pj
chgo

In fact thats the first thing The Monk teaches in his books. The stun shot.

 

[juanbond]

Let's dispense with the basics first. (I assume you're not talking about playing with a mismatched cue ball.) Do you know that the cue ball will only follow the tangent line if it hits the object ball with no forward or backward rotation at all (i.e., sliding on the cloth)?

pj
chgo

This is the main reason you'll notice the less-than-90-degrees tangent. Assuming you're hitting the cueball dead center, then it's simply a matter of the cueball picking up rolling spin from the cloth. I'm surprised you notice perfect 90-degree tangents at slow speed...usually at slow speed, given enough distance of the cueball rolling before hitting the object ball, the angle will be quite less than 90 (many times closer to 30 degrees). Shots struck at higher speed often have no time for the cueball to develop any significant rolling spin, and thus the 90-degree tangent.

 

[UWPoolGod1]

Let's dispense with the basics first. (I assume you're not talking about playing with a mismatched cue ball.) Do you know that the cue ball will only follow the tangent line if it hits the object ball with no forward or backward rotation at all (i.e., sliding on the cloth)?

pj
chgo

This is the key. If the cueball is rolling when it contacts the OB it will slightly continue forward after contact. If you have too much draw on the cueball it will obviously make the cueball rebound a bit. The cueball must be sliding at contact to come off tangent and stay tangent. Hit the cueball below center with the proper speed so right at contact it has stopped its backspin and is just about to begin rolling with topspin.

 

[ShootingArts]

stun

My stun shots work fine when I am using stun for other things and when I use my measles cue ball it does show it to be skidding into the first object ball. To come off on the 90 degree line I have to add maybe another quarter tip of low to what I use to stun the cue ball for other shots depending on distance to the second object ball. I'm not off much with my standard stun hit but enough that if I carom into a ball ten or twelve inches away from the pocket it is sometimes the difference between it dropping or rattling the pocket.

The reason I started this thread is that I notice that this is a consistent issue for me that the cue ball is a little shy of the ninety degree angle. Pulling the cue ball back into line with a little low works OK but of course complicates making the object ball I hit first when I am playing a two way shot.

Hu

 

[juanbond]

...the cue ball is a little shy of the ninety degree angle.

How are you measuring the angle?

 

[ShootingArts]

ye olde eyeball

How are you measuring the angle?

I am indeed using a finely calibrated eyeball to measure the angle. Works pretty good for most things. It could be an eyeball calibration problem but that would seem unlikely for several reasons. One is that I hit the object ball thin whichever side it is on, right or left. The other is that if I miss this shot, I miss it because of a thin hit on the second object ball. It would seem that if I wasn't seeing the angle properly I would hit thin angling one way and thick angling the other. If I were just a poor judge of a ninety degree angle, again it would seem I should be hitting thick and thin not a consistent issue.

Hu

 

[Bob Jewett]

In an effort to start some deeep meaningful pool related discussion on the front page, why ain't my tangent lines tangent?(note matching title!)
...

If the balls are matched, I suspect that you are not hitting the cue ball where you think. Try using the cue ball as the middle ball of a close combination and hit it with an object ball. That way, the cue ball goes into the object ball with very little spin. To make it more perfect, put up an extra ball or two in line with the shot. So, extra cue ball hits object ball which hits object ball which hits cue ball which hits object ball -- note which way the cue ball goes.

There should be 1mm of space between the balls.

This will also make sure the cue ball is not airborne when it hits the object ball.

It is expected that the cue ball will go very slightly ahead of the tangent line (as if it had a little follow) due to the inelasticity of the balls.

 

[Patrick Johnson]

If I were just a poor judge of a ninety degree angle, again it would seem I should be hitting thick and thin not a consistent issue.

You could be misjudging right angles in a consistent way, or misjudging how you need to hit the cue ball in a consistent way. I think a controlled test or two (like Bob Jewett's suggestion for using an "intermediate" cue ball placed 1 mm from the object ball to be sure it's sliding) is needed to isolate the problem.

pj
chgo

 

[ShootingArts]

could be

You could be misjudging right angles in a consistent way, or misjudging how you need to hit the cue ball in a consistent way. I think a controlled test or two (like Bob Jewett's suggestion for using an "intermediate" cue ball placed 1 mm from the object ball to be sure it's sliding) is needed to isolate the problem.

pj
chgo

PJ

My guess is that my ninety degrees is pretty close since I use right angles a lot in everyday work in my shop. If that were off, it would seem to be a strong eye weak eye issue that would reverse itself hitting ninety degrees left or ninety degrees right also.

Cue tip height I'm not quite as comfortable with because I can't remember testing how high and how low a cue ball can be hit and it still skid. However, except when I deliberately use a bit of reverse spin I am skidding into the first object ball, easily confirmed using a measles ball.

Bob's test will be tried. The issue may be as simple as the bit of forward movement he mentioned.

Hu

 

[seymore15074]

[...]A very slight touch of draw corrects this and I do make most of my billiards but the question remains why do I need that slight draw?

I'm not a fan of center-ball hits for this exact reason...I personally think they should be avoided. Before everyone jumps on my case, let me explain:

Just below center gives you the stun with a predictable tangent line...which is awesome.

Just above center doesn't fight the cloth to start rolling...which it wants to do anyway--role.

Certainly stay close to center-ball as often as possible, but exactly center doesn't seem to be such a great thing IMO.

 

[Scott Lee]

Hu...Bob Jewett already answered your question with the most likely accurate response...you're simply NOT striking the CB at REAL center. MOST poolplayers have a misconception of where center is (i.e.: many pro players maintain that they break with a 1/2 tip of draw. They don't...they just don't know where accurate center is!). This is mostly due to a visual misperception by each individual, due to the elevation of the cue, or the chin being a certain distance above the cuestick. Even if your chin were directly on the cue (ala A. Fisher), your eyes would still be several inches above the surface of the table (resulting in your eyes perceiving center ball at an incline...which is where the misperception comes in). The only way to accurately "see" center is to lay your head sideways on the cloth. Of course we can't play this way. The radius of the CB is 1 1/8 inches from the surface of the table. A piece of chalk is exactly 1 1/8 inches in diameter. If you hold a piece of chalk on the cloth on a diagonal, the middle of your ferrule should be at the point on the chalk. If you do this with the CB and a stripe, turned horizontally, you'll see what I mean. I teach my students where center really is, and how to adjust for it. Hope this helps...

Scott Lee
www.poolknowledge.com

In an effort to start some deeep meaningful pool related discussion on the front page, why ain't my tangent lines tangent?(note matching title!)

If I shoot slow to very moderate speed the cue ball does go off on the expected tangent. However with medium or firm speed the cue ball either carries forward a bit before taking off on the tangent or it comes off the object ball at slightly less than 90 degrees. A very slight touch of draw corrects this and I do make most of my billiards but the question remains why do I need that slight draw?

Eyeballs in need of recalibration? Vertical or angular?

Simply the nature of tangents?

Somebody been throwing bounce sheets in the ball cleaner again?

Hu

 

[Jigger]

Dr. Dave online videos

In an effort to start some deeep meaningful pool related discussion on the front page, why ain't my tangent lines tangent?(note matching title!)

If I shoot slow to very moderate speed the cue ball does go off on the expected tangent. However with medium or firm speed the cue ball either carries forward a bit before taking off on the tangent or it comes off the object ball at slightly less than 90 degrees. A very slight touch of draw corrects this and I do make most of my billiards but the question remains why do I need that slight draw?

Eyeballs in need of recalibration? Vertical or angular?

Simply the nature of tangents?


Hu

I believe the 90 degree tangent rule is accurate if the cue ball is hit slightly below centerball (or stun). Hitting with follow will cause the cue ball to deflect slightly less than 90 degrees and hitting more of a stun or draw shot causes deflection of slightly more than the standard 90 degrees.

Dr. Dave explains this and many more pool fundamentals on his Colorado State site. Check it out:

http://billiards.colostate.edu/normal_videos/NV3-4.htm << 90 rule video

http://billiards.colostate.edu/ << various pool fundamental videos

Dr. Daves' produced dozens of excellent videos showing pool concepts including the notorious 90 and 30 degree rules. Great viewing/understanding for anyone looking to improve their game towards a B or higher.

 

[ShootingArts]

Scott a couple of questions please

Scott,

I have a couple of questions concerning true center please. As I have mentioned, the cue ball is skidding into the first object ball, easily seen using a stripe or the measle ball as a cue ball. Obviously a completely perfect true center ball hit is rarer than hen's teeth for any of us. If we were to measure to a thousandth or ten-thousandths, we would find that most of us miss center most of the time. So the first question, what is tolerance for center ball? Eighth tip, sixteenth, or? If the cue ball skids into the object ball without any apparent movement of the markings on the cue ball, isn't this effectively center ball hit for this discussion?

Another question is what is meant by center ball? For most shots I am considering the center of the cue ball which is equal distance from all surfaces as the center of the ball. Is this center ball for the sake of this discussion, requiring a hit slightly above the midpoint of the surface of the cue ball if the butt of the cue is elevated at all? Or is center ball considered to be the back surface of the cue ball at the midpoint of the arc from top to bottom of the ball?

Thanks,
Hu

Hu...Bob Jewett already answered your question with the most likely accurate response...you're simply NOT striking the CB at REAL center. MOST poolplayers have a misconception of where center is (i.e.: many pro players maintain that they break with a 1/2 tip of draw. They don't...they just don't know where accurate center is!). This is mostly due to a visual misperception by each individual, due to the elevation of the cue, or the chin being a certain distance above the cuestick. Even if your chin were directly on the cue (ala A. Fisher), your eyes would still be several inches above the surface of the table (resulting in your eyes perceiving center ball at an incline...which is where the misperception comes in). The only way to accurately "see" center is to lay your head sideways on the cloth. Of course we can't play this way. The radius of the CB is 1 1/8 inches from the surface of the table. A piece of chalk is exactly 1 1/8 inches in diameter. If you hold a piece of chalk on the cloth on a diagonal, the middle of your ferrule should be at the point on the chalk. If you do this with the CB and a stripe, turned horizontally, you'll see what I mean. I teach my students where center really is, and how to adjust for it. Hope this helps...

Scott Lee
www.poolknowledge.com

 

[TATE]

I keep telling you, you have to start controlling those force vectors and friction between the balls. What about gravity? Maybe it's pulling down on your balls.

Seriously, I try to get that ball to skid but the damn thing wants to spin!


Chris