Where is the Center of the Q Ball?

Something that bends when it hits will not place the same amount of force on all points of the circle that strikes the cue ball. In essence it is hitting with a glancing blow. There is more force at 3:00 o'clock than at 9:00 o'clock if the stick whips to the right.
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(Setting aside my suspicion that this effect is so miniscule as to be less than negligible...) Why would the difference between 3 o'clock and 9 o'clock be more for a whippier shaft? At the moment of impact they're at the same angle for both kinds of shaft.

if you look at the permissible error on some pool shots this can cause a miss on critical shots
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Based on what evidence?

Because the normal tremors in one's hand are one of the primary contributor to a lack of accuracy, a robot would not be of use. The inability to keep the stick on line is another major problem that a robot could not evaluate.
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Got me there. Even without tremors in one's hand there are enough variances in one's stroke to make a robot a poor imitator.

it makes sense that a larger tip allows more surface area to contact the cue ball
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You'll have to explain it to me. I explained why I didn't think so...

More surface area leads to more control.
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I know it seems so, but I don't think it's true. Total friction (what I think you mean by "more control") isn't increased by more surface area; the same amount is just spread out over a larger area.

Seems I have to edit every post to get the punctutation marks correct.
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And pool players don't even notice unless it's to think you're a suit.

pj
chgo
 
Given your interest in the science, I expect your tests were done with variables pretty well controlled (if you'd like to offer a more details...).
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Pretty simple. The idea is to shoot the cue ball many times straight into a side rail with the same amount of tip offset and at the same speed, and measure how far to the side they come to rest.

1. Mark the spot to shoot the cue ball from for repeatability (a paper hole reinforcer works well).

2. Restrict the point it can hit on a rail (two object balls with a just-larger-than-cueball space between works).

3. Use a marked ball as the cue ball (aiming at the edge of a vertically aligned stripe works), check the chalk mark after each shot and discard any shots that aren't hit with the correct tip offset.

4. Choose a distance you want the cue ball to travel (near the opposite rail is good) and discard any shots that go long or short.

This "discard the bad shots" kind of control means lots of wasted shots, but it works pretty well if you take the time to hit enough of them.

pj
chgo
 
Assuming that a 1 is the energy needed to move the CB one length of the table and a 2 moves the CB two lengths of the table, etc.

I took a 13mm house cue stick and hit the CB with a 3 hit to pocket the OB in the corner pocket three times. Apparently the diameter of the hit was about 1/4 inch (.25 inch) maybe a little less.

I repeated the procedure with a snooker stick (10 mm) and found a hit diameter of about 1/8, (.125 inch).

Calculating the area of a circle using the appropriate metric conversions, it can be concluded that the stick with 13mm diameter had a hit area = .05. while the 10mm stick hit area was .01

Apparently a house cue has much more surface area at contact than a snooker cue. If I assume 20% measurement error, the house cue has at least 50% more surface area in contact with the cue ball at time of contact. Seems to me that is a real difference.
 
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PJ said, "Setting aside my suspicion that this effect is so miniscule as to be less than negligible...) Why would the difference between 3 o'clock and 9 o'clock be more for a whippier shaft? At the moment of impact they're at the same angle for both kinds of shaft."

Well if there was not unequal pressures then follow through would not be so important right?

Permissible error - see Jack Koehler's "Science of Pocket Billiards," for a thorough discussion of permissible error.

Re larger tip see previous post.

Punctuation - As can be seen in my avatar, I am a suit. Common courtsey in the written word is best. It also speaks to clarity in communication.
 
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Patrick Johnson said:
I'm guessing you mean that the weaker spring takes longer to uncompress and push the object away.
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Yes, and longer to compress.

Patrick Johnson said:
Does this longer compress/uncompress action actually have time to operate fully during the time the tip is in contact with the ball, or does another action push the ball away before that has time to complete?

pj
chgo
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Looking at the stick/tip as two conjoined springs, the tip dominates their combined characteristic as far as contact time, because it is the weaker of the two. (If you drop a ball onto a thick rubber mat on a concrete floor, it will spend much more time in contact than if you drop it on the concrete.) But the stick is a part of this and its bending adds another mode of energy storage (as potential energy), along with its longitudinal compression. This (bending) should weaken the combined system and thus extend the compression phase in time.

Given that the tip continues to move sideways after impact, I'm not sure how much (if any) of the potential energy stored in the bending mode is returned to the system during decompression. This loss of energy, however much, should also extend the contact time (if two things collide and all of the potential energy is converted to heat or permanent deformation, they'll stick together and never separate). But this part isn't going to help with more spin.

Jim
 
Crooked Stroke

When I was real little I used a Coke bottle and stroked through that so that I could train my muscle memory, the problem with this is you cannot pocket a ball and there is also the tendency to have your eyes looking at your cue so that you don't ding your shaft on the side of the bottle. If anyone really wants to learn about how to try and pocket a ball consistently and after the shot has been delivered then being able to 'check your work' I would suggest taking lessons. There are probably many instructors that have access to this info, however I have seen many instructional tapes that are trying but lack the foundation. I would only say that if your seriously interested in learning about your stroke then you have an open invite to MO (Show Me State) and I would be happy to help you. If it is too far for you to travel then PM me and I may know someone in your area that is qualified to teach this material.
Sincerely, Danny Harriman (World Bank Pool Champ)

OOPS Forgot to log on to my acc't, Scott and I are roomates.
 
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Jal said:
A more flexible shaft acts like a weaker spring; it causes the hit to be softer. An object colliding with a weaker spring remains in contact longer.
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Except it is the compressibility of the stick along its length that mostly determines the contact time, and the compression is mostly in the tip. Your assumption seems to be that the stick buckles significantly during contact with the cue ball. I believe that does not occur. It certainly does not occur for a center-ball hit (and a non-bowed stick).
 
JoeW:

I took a 13mm house cue stick and hit the CB with a 3 hit to pocket the OB in the corner pocket three times. Apparently the diameter of the hit was about 1/4 inch (.25 inch) maybe a little less.

I repeated the procedure with a snooker stick (10 mm) and found a hit diameter of about 1/8, (.125 inch).
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I don't see how this could be unless (1) the tips had different curvatures or (2) they were different hardnesses. The tip's diameter shouldn't matter (unless you're hitting on its edge).

As can be seen in my avatar, I am a suit. Common courtsey in the written word is best.
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I hope this doesn't mean you think I was being discourteous with my little joke about "suits". Apologies if it came across that way.

pj
chgo
 
Me:
Setting aside my suspicion that this effect is so miniscule as to be less than negligible...) Why would the difference between 3 o'clock and 9 o'clock be more for a whippier shaft? At the moment of impact they're at the same angle for both kinds of shaft.

JoeW:
Well if there was not unequal pressures then follow through would not be so important right?
 
Me:
Setting aside my suspicion that this effect is so miniscule as to be less than negligible...) Why would the difference between 3 o'clock and 9 o'clock be more for a whippier shaft? At the moment of impact they're at the same angle for both kinds of shaft.

JoeW:
Well if there was not unequal pressures then follow through would not be so important right?
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What does one have to do with the other?

pj
chgo
 
PJ, I did not think you were impolite.

Good follow through insures even (for lack of a better word) contact.

The tips were each a dime curvature and probably came from different companies. the 13 mm is a cheap house cue. The snooker cue is 30 years old. It came from Canada. The tip has not been changed in 10 years. A three hit is a pretty hard hit to insure a solid impression in the chalk. Until somone has better data, it is not a matter of belief is it.

I did make a concave tip on the house cue. Interestingly, in support of your position, I seemed to be able to place as much or nearly as much english with the sharp edge of the concave tip.

The concave tip with a center ball hit subjectively seemed to give a very solid hit. Though it could not be used for anything but center ball.
 
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Things I learned with a concave tip shaped to match the cueball.

1. Solid center ball feels better than regular tip with a three hit. Did not try to slow roll and tip is now mis-shapen.
2. Edge of concave puts as much or more English on cb than a regular tip.
3. Using power draw (one length of the table) I found that one side of the concave curve is most often hit thus CB comes back at an angle. Therefore, there is unequal pressure with a concave tip. This can be generalized to a regular tip's surface area? Power draw with a regular cue bring the cb straight back (so it is not me).
4. A 3 hit above and below center will change the shape to a dime with enough hits. Breaking flattens the tip and you loose the curve. Interesting idea on the need for a special break stick.
 
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Good follow through insures even (for lack of a better word) contact.
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As far as I know, follow through only helps to ensure that your stroke is straight (and maybe the right speed). I can't imagine how it would have any effect on the nature or quality of the momentary contact, since it happens after the cue ball is long gone from the tip.

The tips were each a dime curvature and probably came from different companies.
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Think of it this way: If you simply glued a new 1.5MM layer of leather around the outside of the 10MM tip you'd have the 13MM tip. Why would that cause it to flatten more when it hits the cue ball?

Now think of that in reverse: If you shaved a 1.5MM layer off the outside of a 13MM tip, why would the resulting 10MM tip flatten less?

Since I play with a 10MM tip, I'll try to remember to do the same test you did and report the results.

pj
chgo
 
OK lets use your numbers a snooker cue has .125 diameter circle surface area of contact on a medium stroke. If the stroke is off line on the contact point one side of the circle of contact on the cue stick will hit the target on the cb first and there will be more force applied on the side that is hit first.

Several people have pointed out that follow through is not needed as the contact time is miniscule compared with the hit itself. Assuming this to be true, follow through must have a function because lack of follow through is devastating to aim. I propose that follow through is used to insure that the target is hit square relative to the line of aim. By square I mean that follow through is used to insure that all sides of the target area are hit at the same time.

Corrections to my thinking are appreciated.
 
JoeW said:
OK lets use your numbers a snooker cue has .125 diameter circle surface area of contact on a medium stroke. If the stroke is off line on the contact point one side of the circle of contact on the cue stick will hit the target on the cb first and there will be more force applied on the side that is hit first.

Several people have pointed out that follow through is not needed as the contact time is miniscule compared with the hit itself. Assuming this to be true, follow through must have a function because lack of follow through is devastating to aim. I propose that follow through is used to insure that the target is hit square relative to the line of aim. By square I mean that follow through is used to insure that all sides of the target area are hit at the same time.

Corrections to my thinking are appreciated.
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Like I said above, follow through is important to your stroke, not to the contact. It only helps you stroke straight - it doesn't do anything for HOW the tip hits the ball, only for WHERE it hits it.

pj
chgo
 
PJ. You may be right and wrong on the diameter of the tip hit area. I went back and checked the tip on the house cue and it would appear that I did not re-sand the tip well enough before the test. It looked OK but when I compared two other cues I found that they too had a flattened peak. So this time I took my time dressing the cue stick and the hit area was smaller. This is more in line with you thinking.

However, I did find that two of the 13mm house cues each had about .25 inch flattened area on the tip. These are not my usual playing cues they are most often used by people who visit and do not bring their own cue.

Finally, I have a reasonably good Meucci cue stick for friends who shoot well and it too is slightly flattened, again in the .25 inch range. The better players use my Rick Howard Mace to break with and the Meucci is not beat up.

So it would seem that 13mm cues that start out with a dime radius soon develop about a .25 inch flat spot. While there are many reasons for this, I think that part of the reason has to do with the amount of cue tip on the target area at contact.

With enough study one can find what they are looking for.:D
 
PJ said, ?Like I said above, follow through is important to your stroke, not to the contact. It only helps you stroke straight - it doesn't do anything for HOW the tip hits the ball, only for WHERE it hits it.?

If this is true then I should be able to use a strong toothpick with a leather wrap as a cue tip and get the same result ? right?
 
JoeW said:
PJ said, ?Like I said above, follow through is important to your stroke, not to the contact. It only helps you stroke straight - it doesn't do anything for HOW the tip hits the ball, only for WHERE it hits it.?

If this is true then I should be able to use a strong toothpick with a leather wrap as a cue tip and get the same result ? right?
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If I understand you correctly, yes.

On
chgo
 
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