Does Tip Hardness Influence Cueball Deflection?

Shaft said:
Is it possible to get the same friction with a hard, well-chalked tip as with a soft, poorly chalked tip? Yes, of course, but all things being equal, hardness affects friction.
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Are you implying that, with a hard tip, you might be getting a "partial miscue," where the tip slides slightly during contact? I think with typical pool shots the tip grabs the CB, and does not slide, during contact. If there was sliding, I think the resulting CB direction would vary too much from shot to shot (because the amount of sliding wouldn't be consistent). We have not seen this with testing ... the amount of squirt has been very repeatable with well-chalked tips in good condition. I think this is because the tip (regardless of hardness) actually grabs the CB during contact and doesn't slip.

Regards,
Dave
 
dr_dave said:
I'm not sure what your mean here. The robot delivered the cue at the same offset every time (regardless of the tip hardness). Or are you thinking about how the tip might interact with the CB differently based on the hardness. FYI, clips HSV A.98 through A.109 show various shots for different hardness tips, but the clips might not show what you want to see.
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What I meant was that with a hard tip I find that I hit the ball differently - and better. In particular, I seem to get more spin for the same cue speed / distance from the center of the cb strike.

There was a (rather inconclusive) thread on this http://forums.azbilliards.com/showthread.php?p=1480811#post1480811

If true, then this could conceivably influence the amount of deflection.

Any thoughts?
 
with a hard tip I find that I hit the ball differently - and better. In particular, I seem to get more spin for the same cue speed / distance from the center of the cb strike.
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You might get more CB speed from a hard tip, which can become more spin after hitting an OB (which removes more speed than spin), but the effect of this should be the same as simply hitting harder with the softer tip.

pj
chgo
 
No, no, no....

Since around 1992 the ONLY thing effecting deflection is the Predator logo on the shaft.

Prior to that, I think the patent on the phrase "zero deflection" was owned by Meucci.


Sorry, couldn't resist. :rotflmao1:
 
dr_dave said:
Are you implying that, with a hard tip, you might be getting a "partial miscue," where the tip slides slightly during contact? I think with typical pool shots the tip grabs the CB, and does not slide, during contact. If there was sliding, I think the resulting CB direction would vary too much from shot to shot (because the amount of sliding wouldn't be consistent). We have not seen this with testing ... the amount of squirt has been very repeatable with well-chalked tips in good condition. I think this is because the tip (regardless of hardness) actually grabs the CB during contact and doesn't slip.

Regards,
Dave
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No, I am not implying that hard tips create a partial miscue. I am assuming that tip hardness affects tip friction and I am arguing that tip friction affects squirt. Hardness affects contact area, does it not? I am assuming there is an allowable spectrum between "100% grab" and "100% miscue." I would not call that a "partial miscue."

It seems to me that all tips grab the cue and then at some point begin to slide past. The point of sliding might begin earlier for harder tips.

I am assuming that hardness affects the grab on the CB. If you say it does not, I'll believe you, but then I am a bit baffled by player preferences for one hardness over another.
 
Siz said:
What I meant was that with a hard tip I find that I hit the ball differently - and better. In particular, I seem to get more spin for the same cue speed / distance from the center of the cb strike.

There was a (rather inconclusive) thread on this http://forums.azbilliards.com/showthread.php?p=1480811#post1480811

If true, then this could conceivably influence the amount of deflection.

Any thoughts?
Click to expand...
My thoughts on the effects of tip hardness are summarized here:


Regards,
Dave
 
Shaft said:
I am assuming that hardness affects the grab on the CB. If you say it does not, I'll believe you, but then I am a bit baffled by player preferences for one hardness over another.
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The tip either grabs or it doesn't. I think that if it doesn't grab, then the amount of "squirt" would vary wildly from shot to shot.

Concerning why people have preferences for different hardnesses, I suggest what I think are plausible reasons here:


Regards,
Dave
 
Patrick Johnson said:
You might get more CB speed from a hard tip, which can become more spin after hitting an OB (which removes more speed than spin), but the effect of this should be the same as simply hitting harder with the softer tip.

pj
chgo
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Yes, I think you could be right here.
 
The cue ball squirt is more when you miscue because the shaft first deflects to the side of the cue ball, and then comes back and slaps the side of the cue ball, causing it to move sideways. Very little energy, in either plane, is transferred to the cue ball during the initial impact because of the miscue.

Well, this is what I believe anyway, and I have not proof to back it up.

Royce Bunnell
 
Good dr...

It wont be a partial miscue, it is only this:
A harder tip will have upon impact less surface area of contact with the cueball. It simply gives less. This said, spin should increase on a small level with increasingly softer tips.

There are some important things to consider - A cue with a softer tip requires a minutely harder hit to achieve the exact velocity of cue-ball as a cue with a harder hit. AND with less english. It is this small speed adjustment and small difference of where whitey is hit that should be noted as the cause of deflection differences percieved by players, as this forces the shaft to react differently.

How about a test that applies an exact amount of spin and speed(NOT one tip spin with this vs. one tip with that, with a pre-set robot velocity!!:) ) to a shot, to ultimately show the truth everyone is dying to see???
 
RBC said:
The cue ball squirt is more when you miscue because the shaft first deflects to the side of the cue ball, and then comes back and slaps the side of the cue ball, causing it to move sideways. Very little energy, in either plane, is transferred to the cue ball during the initial impact because of the miscue.

Well, this is what I believe anyway, and I have not proof to back it up.

Royce Bunnell
Click to expand...

I don't think the CB reaction from a miscue is squirt at all. I think it's more like the (relatively) frictionless impact of one ball with another. The shaft doesn't have to hit the ball a second time to cause it.

pj
chgo
 
eyesjr said:
A harder tip will have upon impact less surface area of contact with the cueball.
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I don't believe the amount of contact area has much to do with total friction. A smaller contact area usually has the same total amount of friction, just spread over a smaller area.

pj
chgo
 
dr_dave said:
[...]
See my August '08 article. Tip hardness has only a slight effect on squirt (AKA "cue ball deflection"). In the article, I show plots of real data taken with a cue-testing robot.

[...]
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Dave - What I saw in the article, amongst other things of course, was the squirt for hard and soft tips with small and large added mass. And as you say there is a little more squirt with the softer tip. This makes sense: if the contact time is a longer, the effective endmass is a little larger.

Have you done the soft/hard tip comparison with no added mass?

Seems to me tip hardness is in the same category as stiffness--a property that in principle can affect the squirt but perhaps doesn't much in practice.

For instance if you keep increasing the stiffness of the shaft--beyond the stiffest shaft on any actual cue, eventually stiffness will affect the squirt. Likewise if you keep increasing the contact time through softer and softer tips, then eventually the ball will "see" more of the shaft --more endmass.

In fact if and when stiffness does come into play, it's going to come into play first with a soft tip.

So here's another assignment Dave [;-)]. How about you test with no added mass the effect of hard versus soft tips on a pool cue or two (you've probably already done this). And then to get a worst case scenario, try putting a soft tip on a stiff billiard cue. I think the soft tip might increase squirt more noticeably there.
 
dr_dave said:
My thoughts on the effects of tip hardness are summarized here:


Regards,
Dave
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Here's one more. Even if soft and hard tips held chalk exactly the same, it's possible the soft tip might reduce the chance of miscue. For instance, suppose a miscue occurs when less than 50% of the contact patch has chalk. If the bald regions are small, then this standard may be violated more frequently for a hard tip with its small contact patch.
 
patrick,

What I think happens on a miscue is that the tip slides off,and past the ball. Remember, the ball does not move much because there is very little friction between the tip and the ball, so almost no energy is transfered, so the ball doesn't really move that much. The reason the cue ball goes tremendously to the side is because the shaft rebounds to the flex and attempts to straighten out. When it comes back to straight, it hits the side of the cue ball which has moved very little. This side impact on the cue ball not only moves it almost directly sideways, it also explains the sound or click that you here which is the slap of the cue shaft against the side of the cue ball.

As far as the frictionless impact with another ball theory, the only problem with this comparison is the impact with another ball is an impact with two equal weight parts. The tip end of the cue shaft is much lighter than the cue ball so if there is a very low friction impact between them, the cue shaft will almost all of the deflecting leaving the cue ball to move very little.


I absolutely agree with you on the contact area versus total friction topic. Lets face it, either you have no slip, or almost all slip. Meaning total friction, or almost no friction, which is the miscue.

By the way, I always enjoy your posts!

Royce Bunnell
 
mikepage said:
Here's one more. Even if soft and hard tips held chalk exactly the same, it's possible the soft tip might reduce the chance of miscue. For instance, suppose a miscue occurs when less than 50% of the contact patch has chalk. If the bald regions are small, then this standard may be violated more frequently for a hard tip with its small contact patch.
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Good one. I've added your quote to my "cue tip hardness" FAQ page.

Regards,
Dave
 
RBC said:
j[...]
I would like to thank Dr Dave, Bob Jewett, and Mike Page for all they have done to provide us with answers to questions like these.
[...]
Click to expand...

Hey thanks Royce.

You, me, and cornerman Fred will have to share a couple dozen beers again and REALLY solve some of these problems... ;-)
 
RBC said:
patrick,

What I think happens on a miscue is that the tip slides off,and past the ball. Remember, the ball does not move much because there is very little friction between the tip and the ball, so almost no energy is transfered, so the ball doesn't really move that much.
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RBC,

What Patrick said is right. Think of the force acting on the cueball as comprised of a normal force acting through its center, and a friction force acting perpendicular to it (tangentially to the surface). On a normal shot without miscue, they both add up (vectorally) so that the combined force points almost straight ahead. The squirt phenomenon makes it such that it's not exactly straight ahead, but nearly so. When a miscue occurs, however, the tangential component of the total force is greatly reduced. The normal force now dominates (though it's also affected) and pushes the cueball well off to the side, as well as forward.

RBC said:
The reason the cue ball goes tremendously to the side is because the shaft rebounds to the flex and attempts to straighten out. When it comes back to straight, it hits the side of the cue ball which has moved very little. This side impact on the cue ball not only moves it almost directly sideways, it also explains the sound or click that you here which is the slap of the cue shaft against the side of the cue ball.
Click to expand...
That's true too. But even without this happening, the cueball would be shoved to the side, as per above. Which produces the greater sideways motion, the normal force or the slapping action? Have to think about it but I suspect the normal force.

Jim
 
Last edited:
Jal,

You are right that the cue ball would go to the side in a miscue, even without the shaft slapping it from the side, but it would not travel very far. Most of the energy of the cue shaft would remain in the cue shaft and not be transfered to the cue ball because there is very little friction between the two. Therefore, when you miscue and the cue ball moves significantly to the side, that is cause by the shaft hitting the side of the cue ball. Occasionally you will see someone miscue so bad that the barely graze the side of the cue ball and it moves just a few inches. However, in most cases the cue ball moves at least a few feet to the side which means that it must have received that energy from something, and that something is the cue shaft slapping the cue ball from the side. You can actually here the second impact if you listen carefully.


Royce Bunnell
 
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