Cue tip contact time

Also, doesn't the hardness of the tip effect
the duration of contact?
I like hard tips. Appx. 90a durometer.
I also prefer a stiff tapered cue.
I'd think that a thinner shaft with a soft tip would have a different
compression rate than a thicker shaft with a hard tip...
The stiffer cue remains on the ball longer but not with a hard tip.
In pool, we're generally taught to avoid pushing the cue ball,
which is how that video may appear to a person with a lack of basics.
I find this "concept" entirely fascinating due to so many affective factors.
 
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BeiberLvr said:
Umm, that good players have good timing.
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Which, I hope you will agree, says nothing. Good players play good. And?

He never really says what good timing is about. Or can you point out something specific? Is it a matter of actually accelerating at contact? Acceleration going to zero at about contact time for a minimum-effort shot? Uniform acceleration in the forward stroke? Smoothly peaked acceleration in the forward stroke? (Technically this last is with minimum "jerk". That's really a technical term.) Or is it just accurately hitting next to the miscue limit with good speed?

I hope he uses the 30,000 FPS camera to study the additional dynamics of a "good" stroke, including an actual time/position/velocity/acceleration profile. For a start on such a study, see Dr. Dave's link above.
 
wigglybridge said:
"... look at the way the grip functions on Any snooker player; the top ones all, without exception, open the grip on the backstroke, a ...
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I don't care what the back fingers are doing -- perhaps I should have mentioned that. From what I've seen, there is never any daylight between the cue stick and the webbing between the thumb and first finger for snooker players. As long as no daylight opens there, the distance from elbow joint to the cue stick axis (measured along the line of the arm) remains constant. All the snooker players I've watched have a totally closed grip as far as the thumb and index finger are concerned.

As for why the back fingers are opened and closed, I think there is less motion in the hand if the back of the hand is not fully closed. The wrist has to twist more if all the fingers are kept wrapped snugly around the cue stick. Some pool players advocate a thumb-and-middle-finger grip and it is reasonable to argue that since that is more directly in line with the line of the arm bones, it makes a "better" connection to the cue stick. Or, middle and ring finger along with the thumb.
 
conetip said:
The way the tip compresses differently.
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Is that because the tip is not centered on the ferrule or perhaps is not uniform hardness around? Or is it just because the hit is farther from the center of the cue ball? Surely the latter will cause a different compression. See the high-speed clip from the Austrians on Dr. Dave's site for some serious compression of a high Moori.
 
dr_dave said:
I don't remember that result from the Jacksonville Project. Bob, if you are listening, could you please verify this. I did not see mention of this in any of the articles on the Jacksonville Project resource page. I only tested center-ball hits when I did my cue tip contact time studies.

Thanks,
Dave
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As I recall, there was a 2:1 ratio of contact time for max vs. 0 spin. The result is a little questionable due to the fact that the robot had a very stiff, heavy hand and the grip was unhuman.

The contact time is more or less going to be the total distance travelled forward by the cue stick during contact divided by the average speed during that time. I think there are two opposing factors: the cue stick is slowed less so the average speed is faster but the cue stays on the ball over a longer distance as it goes "around the edge" of the ball some. I expect the latter to be the larger factor.

I recently unearthed my copy of the Jacksonville tape and I can try to find any related sequence. Unfortunately, that camera did not make very good images at speeds above 3000 FPS due to the limited total number of pixels per second. You need a very fast camera, as in the OP clip, to see speed differences. If the OP setup did some center-ball shots, that would tell us right away, except the stick speed needs to be roughly the same.
 
Bob Jewett said:
Is that because the tip is not centered on the ferrule or perhaps is not uniform hardness around? Or is it just because the hit is farther from the center of the cue ball? Surely the latter will cause a different compression. See the high-speed clip from the Austrians on Dr. Dave's site for some serious compression of a high Moori.
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I think it is because the accelerating stroke is changing the compression of the tip. So the spring of the tip is not so random. Also you can see the shaft frequency in the very high speed video. It will be interesting to look at how a carbon shaft behaves at these sort of resolution .
Certainly, it shows that the stroke of the player is a huge factor for the final result. A carbon shaft the speed of sound is like 20km/sec, where in a wood shaft it is like 4km/sec. I am sure that the sound reflection is effecting the shot, which is in the wave of the cue tip.
Neil
 
conetip said:
I think it is because the accelerating stroke is changing the compression of the tip. So the spring of the tip is not so random.
Neil
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The stroking force that keep the cue accelerating is virutally negligible once the impact begin. It quite comparable to the scenaniro that the "compression" of a car is mainly decided by the collision speed regardless whether the car was accelerating or not.

It definitey affects how the hit felt afterwards though, just that it shouldn't affect the impact much.
 
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conetip said:
I think it is because the accelerating stroke is changing the compression of the tip. ...
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I am confused. Which particular strokes are you saying are accelerating or not accelerating? There is no acceleration info in the video in the OP link.
 
Bob Jewett said:
I am confused. Which particular strokes are you saying are accelerating or not accelerating? There is no acceleration info in the video in the OP link.
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At the end of the video link is some very high speed clips. They have ticks above them on a what the cuest considers a good hit versus a poor or bad hit. Barry talks about the acceleration and trying to keep the cue tip in contact with the ball with the longest possible time, without pushing the ball. You can see the differences he is talking about in the video clips. It is in the way the cue tip decompresses I think is the key, as a result of the stroke technique. Like I said , there is a lot happening in the 35k/second video clips. It would have been better if they had more centre ball shots. But the ones they have do demonstrate very well the differences between a good hit versus a bad hit. I guess,what he needs is a poor or average player to do the same or similar shots, to see the real difference.
 
conetip said:
At the end of the video link is some very high speed clips. They have ticks above them on a what the cuest considers a good hit versus a poor or bad hit. Barry talks about the acceleration and trying to keep the cue tip in contact with the ball with the longest possible time, without pushing the ball. You can see the differences he is talking about in the video clips. It is in the way the cue tip decompresses I think is the key, as a result of the stroke technique. Like I said , there is a lot happening in the 35k/second video clips. It would have been better if they had more centre ball shots. But the ones they have do demonstrate very well the differences between a good hit versus a bad hit. I guess,what he needs is a poor or average player to do the same or similar shots, to see the real difference.
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My point is that you can measure acceleration from the video, although it is difficult. I do not see any measurement.

Are you familiar with the analysis that shows why acceleration at the time of impact is of negligible effect?
 
conetip said:
At the end of the video link is some very high speed clips. They have ticks above them on a what the cuest considers a good hit versus a poor or bad hit. Barry talks about the acceleration and trying to keep the cue tip in contact with the ball with the longest possible time, without pushing the ball. You can see the differences he is talking about in the video clips. It is in the way the cue tip decompresses I think is the key, as a result of the stroke technique. Like I said , there is a lot happening in the 35k/second video clips. It would have been better if they had more centre ball shots. But the ones they have do demonstrate very well the differences between a good hit versus a bad hit. I guess,what he needs is a poor or average player to do the same or similar shots, to see the real difference.
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I watched those shots too, and I think you're seeing what you want to see.

pj
chgo
 
goettlicher said:
Thank you Straightpool_99

Goes to prove what we have been teaching for 40 years.

For me it all started with "The Jacksonville Experience"

1/1000 of a second. Make the Stroke, everything else is secondary!


randyg
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That myth was busted by the Russians.. Dr Dave should have the high speed video on his site... The hard tip was around 1ms and a Kamui M was around 2ms and they did not test anything softer in the videos but based on the videos I would expect increased times as the tip got softer.....
 
Reading the youtube comments on the video is quite entertaining. The 15 or so I read all seem to be praising the video. Below is a small sampling:

Nice to see you back Sir, this knowledge is really wonderful and it does take place on every shot.
People who say it's rubbish, have no idea about physics.

Completely agree with your theory Barry. Even as a very average player you can definitely feel when you've timed the shot well, the sound and the feel of the vibration in your cueing hand tell you instantly whether you've timed well or not.

Barry this is quite amazing. I am a senior researcher at University of Wisconsin-S and I would love to publish an article anout your findings, citing you and giving you credit for all this. Let me know if you would like me to work on an academic articl about this, I believe it would be a first in the scientific community which would be quite amazing
 
iusedtoberich said:
Reading the youtube comments on the video is quite entertaining. The 15 or so I read all seem to be praising the video. ...
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You may want to look at the comments on his "rebound" video, which is basically about frozen ball kiss shots.
 
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