Effects of Tip Hardness

Andrew Manning

Andrew Manning

Aspiring know-it-all
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A question for the Bob Jewett and Dr. Dave crowd:

Has there been a scientific study of the effects of tip hardness on CB impulse, duration of contact, and location of miscue limit?

Aside from anecdotal evidence, "from my 30 years hitting pool balls and judging them qualitatively without any kind of measurement, I can definitively tell you that X is the gospel truth" BS advice you get everywhere you turn on here, and sales pitches, it occurs to me that I don't know the extent of the effect of tip hardness on these three quantitatively measurable properties.

Has anything resembling the scientific method been applied to the task of measuring these relationships? If so, what were the methods and conclusions?

-Andrew
 
Maniac

Maniac

2manyQ's
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Bump for answers to a good question. I have a lot of respect for the good Dr. Dave and Bob Jewett's opinions/research.

Maniac
 
randyg

randyg

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Refereed to as the "Jacksonville Experiments".

Bob Jewett would know for sure, he was there......SPF=randyg
 
Andrew Manning

Andrew Manning

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randyg said:
Refereed to as the "Jacksonville Experiments".

Bob Jewett would know for sure, he was there......SPF=randyg
Click to expand...

I thought those were deflection-based, measuring differences from shaft-to-shaft, rather than measuring the effects I mentioned (which can be summed up as how much a tip will "juice" the CB) from tip-to-tip.

-Andrew
 
LWW

LWW

MEMGO5
Silver Member
I would love to see some serious work on that.

I've always suspected that the soft tip being better because the ball stays on the tip longer sounded like snake oil.

Logic would be that a harder tip would compress less and therefore transfer power to the CB better and more consistently than a softer tip.

A softer tip does seem to have a more desirable "FEEL" to it, and I think that may be the root of the hypothesis.

Also, by logic, a softer tip should weigh less and thereby have a very minute effect on deflection.

That being said, those are merely my thoughts and I have done zero scientific research to bear them out.

LWW
 
Andrew Manning

Andrew Manning

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LWW said:
I would love to see some serious work on that.

I've always suspected that the soft tip being better because the ball stays on the tip longer sounded like snake oil.

Logic would be that a harder tip would compress less and therefore transfer power to the CB better and more consistently than a softer tip.
Click to expand...

But compression is only the first part of "transfer of power"; coefficient of restitution has at least as much to do with it. Non-sanctioned golf drivers hit the ball farther by compressing more than ordinary drivers, and then having a trampoline effect as the ball leaves the club face.

Which of these effects, along with whatever other variables may come into play, is the most significant, is far from clear cut in my view, and thus I think any relevant discussion of the topic has a strong need for empirical data found through scientifically controlled experiments.

LWW said:
Also, by logic, a softer tip should weigh less and thereby have a very minute effect on deflection.
Click to expand...

I'm not sure that follows. Is density strongly correlated with hardness in cue tips? I honestly have no idea.

-Andrew
 
Cornerman

Cornerman

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Andrew Manning said:
I thought those were deflection-based, measuring differences from shaft-to-shaft, rather than measuring the effects I mentioned (which can be summed up as how much a tip will "juice" the CB) from tip-to-tip.

-Andrew
Click to expand...
There were dozens of questions that the Jacksonville Project was trying to address. It certainly wasn't just focused on squirt. Contact time, rotation during contact, double vs. single hits at close range... these were the real important things that came out of this, IMO.

Here is a (not all-inclusive) list of things they were looking at:

http://groups.google.com/group/rec.sport.billiard/msg/5ae578d8941f2c63?dmode=source

Tip hardness, contact time, spin results from different hardnesses...

Fred
 
randyg

randyg

www.randygpool.com
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Cornerman said:
There were dozens of questions that the Jacksonville Project was trying to address. It certainly wasn't just focused on squirt. Contact time, rotation during contact, double vs. single hits at close range... these were the real important things that came out of this, IMO.

Here is a (not all-inclusive) list of things they were looking at:

http://groups.google.com/group/rec.sport.billiard/msg/5ae578d8941f2c63?dmode=source

Tip hardness, contact time, spin results from different hardnesses...

Fred
Click to expand...

Still my hero....:)
 
Andrew Manning

Andrew Manning

Aspiring know-it-all
Silver Member
Cornerman said:
There were dozens of questions that the Jacksonville Project was trying to address. It certainly wasn't just focused on squirt. Contact time, rotation during contact, double vs. single hits at close range... these were the real important things that came out of this, IMO.

Here is a (not all-inclusive) list of things they were looking at:

http://groups.google.com/group/rec.sport.billiard/msg/5ae578d8941f2c63?dmode=source

Tip hardness, contact time, spin results from different hardnesses...

Fred
Click to expand...

I stand corrected.

Anyone know where the "findings" section of the Jacksonville write-up can be viewed?

-Andrew
 
Andrew Manning

Andrew Manning

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Patrick Johnson said:
Bob Jewett made tapes and notes available just after JAX, but I never saw a formal report. If there is such a thing Bob must have it.

FYI, here's a series of Billiards Digest articles about JAX (posted at SF Billiards Academy):

http://www.sfbilliards.com/jax_bd150.pdf

pj
chgo
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That was a very interesting link, and I enjoyed the read.

However, apart from one unsupported conclusion (that for a break cue, the efficiency of the tip is the most important factor in how much CB seed you get for a given stroke), that write-up didn't really address any of the questions of this thread. I still suspect it will take Mr. Jewett himself to provide anything definitive.

-Andrew
 
Siz

Siz

AzB Silver Member
Silver Member
The crucial question that the Jacksonville Experiments did not address (to my knowledge) is "Apart from the obvious, what is the difference in the way that the expert player with a great stroke hits the ball compared with the banger?" Certainly, experts give the impression of somehow having a better 'quality' of hit, but is this borne out by the physics?

For example, the experiments show that the length of the contact time is small - around 1/1000 s. But around this, is there a significant difference between the average contact time in a good hit and a 'bang'? :confused:
 
Gerry

Gerry

AzB Silver Member
Silver Member
Siz said:
The crucial question that the Jacksonville Experiments did not address (to my knowledge) is "Apart from the obvious, what is the difference in the way that the expert player with a great stroke hits the ball compared with the banger?" Certainly, experts give the impression of somehow having a better 'quality' of hit, but is this borne out by the physics?

For example, the experiments show that the length of the contact time is small - around 1/1000 s. But around this, is there a significant difference between the average contact time in a good hit and a 'bang'? :confused:
Click to expand...



great point there Siz!

it always comes down to the Human element IMO!

thats why Efren can be the worlds best with a $25 cue, and I can't run 25 balls with the worlds best cue! :)
 
Cornerman

Cornerman

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Siz said:
The crucial question that the Jacksonville Experiments did not address (to my knowledge) is "Apart from the obvious, what is the difference in the way that the expert player with a great stroke hits the ball compared with the banger?" Certainly, experts give the impression of somehow having a better 'quality' of hit, but is this borne out by the physics?

For example, the experiments show that the length of the contact time is small - around 1/1000 s. But around this, is there a significant difference between the average contact time in a good hit and a 'bang'? :confused:
Click to expand...

I thought it was answered, but in case you didn't know, one of the participants was a Artistic Billiards Champion. And if anyone has a stroke, it's an artistic billiards player.

Also, Bob Jewett was one of the participants. Not only is Bob a Master Instructor, he's run over a 100 balls in straight pool. I think that qualifies as "good."

Fred
 
Tennesseejoe

Tennesseejoe

AzB Silver Member
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You did not request 'deflection' specifically, but this information is on Dr. Dave's site if my memory serves me right.
 
Siz

Siz

AzB Silver Member
Silver Member
Cornerman said:
I thought it was answered, but in case you didn't know, one of the participants was a Artistic Billiards Champion. And if anyone has a stroke, it's an artistic billiards player.

Also, Bob Jewett was one of the participants. Not only is Bob a Master Instructor, he's run over a 100 balls in straight pool. I think that qualifies as "good."

Fred
Click to expand...

Yes, but did they have a banger to compare against?
 
M

MitchAlsup

AzB Silver Member
Silver Member
Andrew Manning said:
Has there been a scientific study of the effects of tip hardness on CB impulse, duration of contact, and location of miscue limit?
Click to expand...

The hardness of the tip only determines how big an area exists at the contact point. Hard tips have smaller area and vice versa. Large area means low pressure at contact, small area means larger pressure at contact.

The pressure at the contact point needs to be high enough that the chalk crystals dig into the leather surface and into the surface of the cue-ball. This allows friction to deliver spin to the CB. The pressure must not be so high that the chalk crystals turn to dust or the friction disapears instantly.

Chalk manufactures add chemicals to alter the strength properties of the chalk crystals. So differnt chalk crystals break down at different pressure levels.

So, when talking about spin, mis-cue limits, and such; there is an optimum pressure where the tip is deformed to an area compatible with the chalk pressure characteristics. Thus tip hardness is a function of what chalk you end up liking.

To the best of my knowledge, the difference in the miscue limit between a soft tip and a hard tip, each with a chalk chosen for that tips hardness, is very tiny indeed. The amount of spin one can achieve between the tip hardness-es is similarly small--not nonexistent, just small. I happen to think with my tip hardness, chalk, and stroke, a hard tip give me more spin. You are free to believe just the opposite.

To the best of my knoledge, there is a useful difference in the energy transfer to the CB, with the harder tip delivering more energy into the CB. Less energy is absorbed in the inelastic deformation of the tip at impact. {Why do you think they put super hard tips on break and jump cues?}

Also, to the best of my knowledge, a single player may like a medium-soft tip when playing something like 14.1, a medium tip when playing 8-ball, and a hard tip when playing 9-ball--just because of the different kinds of strokes and actions involved in these games.
 
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Andrew Manning

Andrew Manning

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Silver Member
MitchAlsup said:
The hardness of the tip only determines how big an area exists at the contact point. Hard tips have smaller area and vice versa.
Click to expand...

I'm pretty sure this is true.

MitchAlsup said:
Large area means low pressure at contact, small area means larger pressure at contact.
Click to expand...

Only if the force between the two is equal. The force between the tip and the ball is equal to the amount of momentum transferred divided by the time it takes to transfer it, and I haven't seen any data telling me definitively how much the quantities vary with tip hardness. So I have no reason to believe that the force is equal.

MitchAlsup said:
The pressure at the contact point needs to be high enough that the chalk crystals dig into the leather surface and into the surface of the cue-ball. This allows friction to deliver spin to the CB. The pressure must not be so high that the chalk crystals turn to dust or the friction disapears instantly.

Chalk manufactures add chemicals to alter the strength properties of the chalk crystals. So differnt chalk crystals break down at different pressure levels.

So, when talking about spin, mis-cue limits, and such; there is an optimum pressure where the tip is deformed to an area compatible with the chalk pressure characteristics. Thus tip hardness is a function of what chalk you end up liking.
Click to expand...

This all sounds like conjecture, what's your source? What you're saying (that the silicon-dioxide in the chalk will actually break and thus lose grip if the tip is overly hard) sounds conceivable, but not likely, to me. I have a hard time taking your word for it without experimental data to back it up.

MitchAlsup said:
To the best of my knowledge, the difference in the miscue limit between a soft tip and a hard tip, each with a chalk chosen for that tips hardness, is very tiny indeed. The amount of spin one can achieve between the tip hardness-es is similarly small--not nonexistent, just small. I happen to think with my tip hardness, chalk, and stroke, a hard tip give me more spin. You are free to believe just the opposite.
Click to expand...

Fair enough, but I don't really want to "believe" one way or the other, I'd rather find some data that shed some light on the actual truth of the matter.

MitchAlsup said:
To the best of my knoledge, there is a useful difference in the energy transfer to the CB, with the harder tip delivering more energy into the CB. Less energy is absorbed in the inelastic deformation of the tip at impact. {Why do you think they put super hard tips on break and jump cues?}
Click to expand...

Again, I expect that what you're saying is true, about the amount of energy transfer, but I would like to know the extent. Between a soft and a hard playing tip (the extremes of the range people actually use on their playing cues), what's the variance in the energy transfer efficiency?

MitchAlsup said:
Also, to the best of my knowledge, a single player may like a medium-soft tip when playing something like 14.1, a medium tip when playing 8-ball, and a hard tip when playing 9-ball--just because of the different kinds of strokes and actions involved in these games.
Click to expand...

And this just comes back to what we already know; that when it comes to the "feel" of a cue, and how much touch and control a given player thinks he has with one cue vs. another, it all comes down to personal preference. The fact that the best players in the world have varying preferences in tip hardness sort of proves that none is objectively better when it comes to winning matches. But there should be an objective answer to the questions I asked in the first post, and I still hope Bob Jewett will chime in with some real experimental data.

-Andrew
 
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