so the cuestick at the moment it strikes the cueball has lost all its acceleration.? think about that statement for a minute.
the cueball would have to be maybe infinitely heavy. but you even said before contact.
Cue Tip Contact Myth-Busting Truths in Super Slow Motion
- Thread starter dr_dave
- Start date
the cueball would have to be maybe infinitely heavy. but you even said before contact.
maybe you didnt understand it at all.
Das Cue-Boot
Active member
I think what we are seeing is that there isn’t that much difference between a soft and hard playing tip. The contact time differences should come as no surprise—you can come up with essentially the same numbers by carefully stepping through his older high speed videos. Playing tip contact times go from about 1 to just under 3ms for hard to super soft tips. The total momentum imparted should be the same, which says the force is much larger for a shorter period for a harder tip. The second effect is that the tip compresses for a softer tip, so the pressure at impact is even lower for a softer tip since it spreads the lower force over a larger area.
When you go to a phenolic tip, the impact time is even lower and because of the hardness, the contact area is even smaller on the edge of the tip, so the pressure is now several times that of a playing tip. With the reduced ability to hold chalk, at some point you will exceed the shear stress for holding chalk on the edge of the cue and it will slip. This is a whole different problem than calculating friction coefficients since our assumptions about structure may no longer be valid for the chalk and the cue tip—you will at some point shear the chalk layer on the edge of the tip.
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Das Cue-Boot
Active member
The original is off copyright, so you can download a pdf of Coriolis’s work as it was originally published. Google has a project where they are attempting to preserve all of these classic works in their original form. Search for “Theorie Mathematique des effets du jeu de billiard google“ and you’ll find multiple download sites.
Your swoop stroke during testing doesn’t help. Pops up too many times. It seems you’re still not understanding the premise. Of why people say this. You’re literally testing to achieve a specific result. No testing to get varying results.
Reviewers talk about real world results and the conditions there fall out of infinity; including the individual player. Those nano differences may be far from irrelevant in something as trifling as a two ball run.
Das Cue-Boot
Active member
I put a bunch of tips on my high precision scale the other day (reads to 1 mg, but breathe on it wrong and it varies by a few mg). Density differences are overwhelmed by the dimensional differences, essentially the thickness of the tip, and there were some cases where a soft tip was more dense than medium tips. The one exception was for the phenolic tips, which had a density of about 1.5, the leather playing tips were in a narrow range right around 1.0.
I'm in the soft tip = more spin crowd. Just based on personal experience prior to knowing a soft tip was mythologized as having that property. I didn't go into it with any bias or looking for results. It was a discovery for me. But I'm a variable, not a machine. So I could just be plain wrong.
Would be interesting to see this tested once and for all with high speed video and a stroke robot someday to remove the human error. Count RPM. Of course there's going to be different ways to measure this, because of deflection, swerve....
Another thing of note to me is that when the whole phenolic tipped break cue thing began, all the pros I spoke to about this or overheard talking about it never cited more speed/power as being the benefit, but rather that these tips produced less spin. Spin was undesirable on the break. But, pros can be susceptible to myths too ...although, I tend to give weight to this "appeal to authority" ...
It is extremely interesting though that the video has finally proved that there is indeed a difference in contact time. There was debate over this in the past where some would say "it's exactly the same" ...well, it is not. How could it be when it is attributed to hard tips to be more efficient or create more speed.
I really appreciate DrDave, and I don't mean any disrespect at all, but hand-waving or blowing this difference off by saying it's a minuscule fraction of time does not seem correct since it's based on what? Per the provided results, there was a 46% difference in contact time between the soft tip and hard tip. Is that not a significant difference? It doesn't matter if relative to our perception that's all within 1ms, for how the tip interacts with the CB, within that time realm that's a big difference. It's like saying "atoms are all tiny, their differences don't matter". Perhaps the Dr was thinking about these people who claim they are perceptibly "driving" the ball, hence the graph about the acceleration, deceleration and again acceleration. In that context, sure I could see that comment making sense. However, not in the greater context of what might be the effect on the CB.
The question then is, does this significant difference in tip contact time translate to anything? The 2nd video sets to prove that it doesn't equate to more spin, but interestingly, hard tips are granted more speed. It could very well be that longer tip contact time does nothing. The whole myth is on the idea that longer contact off axis in some way helps spin the ball better. But what would that matter? All that should matter is energy transfer regardless of tip contact duration. Speed is a factor in this. So how is that we have this decoupling of speed from spin, attributed to harder tips, but not to softer? Shouldn't the harder tip give more spin if the mechanism was strictly energy transfer to a point on the CB regardless of contact duration? There's got to be more to the story....
Anyway, thank you so so much for doing this video, putting all the hard work into it and increasing the knowledge of pool.
Would be interesting to see this tested once and for all with high speed video and a stroke robot someday to remove the human error. Count RPM. Of course there's going to be different ways to measure this, because of deflection, swerve....
Another thing of note to me is that when the whole phenolic tipped break cue thing began, all the pros I spoke to about this or overheard talking about it never cited more speed/power as being the benefit, but rather that these tips produced less spin. Spin was undesirable on the break. But, pros can be susceptible to myths too ...although, I tend to give weight to this "appeal to authority" ...
It is extremely interesting though that the video has finally proved that there is indeed a difference in contact time. There was debate over this in the past where some would say "it's exactly the same" ...well, it is not. How could it be when it is attributed to hard tips to be more efficient or create more speed.
I really appreciate DrDave, and I don't mean any disrespect at all, but hand-waving or blowing this difference off by saying it's a minuscule fraction of time does not seem correct since it's based on what? Per the provided results, there was a 46% difference in contact time between the soft tip and hard tip. Is that not a significant difference? It doesn't matter if relative to our perception that's all within 1ms, for how the tip interacts with the CB, within that time realm that's a big difference. It's like saying "atoms are all tiny, their differences don't matter". Perhaps the Dr was thinking about these people who claim they are perceptibly "driving" the ball, hence the graph about the acceleration, deceleration and again acceleration. In that context, sure I could see that comment making sense. However, not in the greater context of what might be the effect on the CB.
The question then is, does this significant difference in tip contact time translate to anything? The 2nd video sets to prove that it doesn't equate to more spin, but interestingly, hard tips are granted more speed. It could very well be that longer tip contact time does nothing. The whole myth is on the idea that longer contact off axis in some way helps spin the ball better. But what would that matter? All that should matter is energy transfer regardless of tip contact duration. Speed is a factor in this. So how is that we have this decoupling of speed from spin, attributed to harder tips, but not to softer? Shouldn't the harder tip give more spin if the mechanism was strictly energy transfer to a point on the CB regardless of contact duration? There's got to be more to the story....
Anyway, thank you so so much for doing this video, putting all the hard work into it and increasing the knowledge of pool.
I don't know much about physics but i thought larger contact area have more friction than small.
Somehow i get impression that miscue limit is same. I believe that. But smaller area of contact of tip to ball you have less friction.. Here i get impression it does not matter. I think it matters.
Somehow i get impression that miscue limit is same. I believe that. But smaller area of contact of tip to ball you have less friction.. Here i get impression it does not matter. I think it matters.
This is why it would help to know just how much slippage there is between tip and cue ball if we are to answer the questions rather than concluding too little difference to matter.
We have two options: I hate to use square inches when talking about such tiny areas but that is easiest to use. We have the choice of a smaller contact area with more pounds per square inch on each chalk grit contact point or we can have a larger number of contact points with less pounds per square inch holding the sharp grit in contact with the cue ball and tip. There is also the question as to what the chalk between pieces of grit is worth in terms of
Things are far from definitively answered and past experiences with Dave lead me to conclude they are unlikely to be answered. However, I am convinced that the differences in grip between a hard tip and a soft tip are too small to be reliably exploited in our play. Over five hundred posts to finish right where I started, humans don't have the speed control or accuracy to consistently get maximum performance from a cue tip and chalk.
After all of the cyphering and statements, true, false, proven, unproven, I can't say I know a bit more than when this thread started. I do suspect that "feel" is a little better with a soft cue tip and since I generally shoot softly and emphasize minimum cue ball movement a soft tip is probably best for me. I found that I favored soft tips 53 years ago so other than reinforcing my decisions over the years, nothing has changed.
Hu
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Hoping you were tossing an apple joke. But just in case:
Zero acceleration means constant velocity in the linear direction of the cue stroke. Of course there is still gravity acting on it, but we’re concentrating on the cuetip to cueball, both of which are in the same Newtonian bubble.
If you were suggesting that in the Force equation, zero acceleration must mean huge mass to get any force, that would be a misunderstanding of what the Force is before contact vs during contact. The Force during contact can be me measured by the deceleration of the cue during contact. We can also revers calculate it by examining the change of momentum (the impulse). But the linear Force of the cue on its own just before it reaches the cue tip drops to zero, and its momentum would be at a maximum.
All the acceleration happens before the cuetip get to the tip. This is well-documented fact, or dare I say, acceleration at tip contact has been a busted myth for over twenty years. Today, Dr Dave’s and others’ continued tests and measurements give even clearer understanding of the motion of the tip in terms of acceleration and velocity.
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I actually played hard tips few years. When I then tried again Elk Master I felt i found my lost love. Month ago I alsoI tried Taom Fusion also which is close to Elk.. It was okay but I still took it away after week play due couple shots that I started miscue with it. If I can´t trust tip 100% I think it is worthless.
Facts/data/video may have finally worn them down.
false.
That is not the case. For a given total force pushing the surfaces together, there is greater pressure (force per area) over a smaller contact patch area, which creates greater friction in the same proportion. For more info, see the discussion of contact patch on the cue tip hardness effects page.
Pubo
Active member
I have a question not about this post, just about spin rate. When we talk about quality of spin, what is the quantity that is being measured? Just the angular velocity of CB or the (angular velocity)/(CB speed) measured right after impact?
For quality of spin, it’s the spin to speed ratio (angular velocity/CB speed) right after tip/ball separation.
For spin rate, it’s RPMs
Two different attributes.
That's the question at the heart of the disagreements here. Mainly people not getting that there's a difference.
And that's the answer.
"Quality of spin" means the kind of spin that makes the most difference in pool results (i.e., spin-to-speed ratio).
pj
chgo