Please explain...I do not understand drawing a cue ball 3 rails with low OUTSIDE on a spot shot. A diagram would be perfect. Thanks in advance.
Tip shape
- Thread starter dquarasr
- Start date
I think you must mean 5.8 mm, which is 10 or 20 times the differences we're talking about.
pj
chgo
The 7% figure came from using an estimated 1mm difference in applied spin. Doing the actual math shows that the difference is less than 1mm. I came up with slightly different calculations:
Using a 14.3mm offset from ccb as maximum applied spin...
If a dime radius tip is used to hit a max spin shot at a 14.3mm offset, then using a nickel radius tip (same hardness) on the same shaft, same aim line and speed, would result in a 13.7mm offset, which would be 95.8% of maximum spin, a decrease of 4.2%.
Doesn't seem like a big deal, I know. And it's not when looking at it on paper. But our eyes and our fine sense of touch/motor skills can tell the difference.
Compare it to speed. I mean, a player can practice lagging speed and get a very good and consistent feel for landing the cb within an inch or two off the rail. Being off on speed by 4.2% would land the cb 7 to 8 inches off the rail.
The only thing certain here is the math. As far as how fine-tuned any given player might be to such tiny differences is a matter of opinion.
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Using maximum bottom right english...
UPDATE: disclaimer...The table I did this on last year was a new Diamond barbox with a shiny new set of balls. Anyway, I just wasted 15min on my 8ft table trying to pull it off, and there's no way I can do it. Still, I did it 3 or 4 times on that barbox with the cynergy cue, but I could not get the same action with my regular cue on that same table. I got much better then than I show here, but my cloth isn't new and the balls aren't new and polished.
Anyway, here are two shots I just recorded that are good stroke shots. The frozen rail shot should be learned and practiced...it's a handy rail-first shot to know that can be used in many situations.
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phreaticus
Well-known member
You’re right, sorry! I dropped a zero doing my head math in a pre-caffeinated state earlier. My bad
Brian pretty much summed it up. If/how much 4-7% difference “matters” really lives in the subjective realm, but I think long draw shot drills will bring it out.
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Damn...." You're a better man than I am, Gunga Din." Rudyard Kipling.
You're probably a much better man than I'll ever be! Lol.
I just have a big-table stroke, and this shot was on a Diamond barbox with a cuetec cynergy shaft. My regular playing cue is 12.8mm, and this was an 11.8mm. Not sure about tip hardness differences, but something sure did make a noticeable difference compared to shooting the shot with my cue. I did it several times in a row, but couldn't get that much action when trying it with my own cue.
I was either hitting a touch lower and not realizing it, or that carbon fiber cue just transfers more energy to the cb. I suppose I could practice hitting a touch lower with my cue to see if I can do it better, but it's not exactly a shot I care to waste practice time on.
Not a barbox...8ft diamond table.
PJ or Bob J.....
Do you think or know whether or not cb spin is different based on the portion (amount) of the tip that strikes the cb?
Here's why I ask....
At max spin, with an 11.8mm nickel-shaped tip, the contact point on the tip is 0.6mm from the tip's edge. Max spin using an 11.8mm dime-shaped tip results in tip contact being 1.4mm from the tip's edge.
With the average contact patch being about 4mm in diameter, it seems like the 0.6mm hit would have less "bite" on the cb, compared to a 1.4mm hit (tip contact point).
Along this same line of thinking, it seems that maximum spin would then be the result of striking the cb so that a full contact patch is achieved on the outermost portion of the tip (allowing room for a full contact patch). Am I making sense? Lol
If so, then max spin would be acheived by aiming to strike the cb 1 to 2mm thicker (closer to center), to get more bite, to get a larger contact area between the tip and the ball. The closer the contact point is to the edge of the tip, the smaller the contact patch will be (smaller amount of tip surface being used). So it seems like aiming for max spin near the miscue limit could actually create less spin than aiming a touch thicker.
What do you think?
Please shoot this theory down immediately if either of you or Dr. Dave has already proven or disproven it.
Do you think or know whether or not cb spin is different based on the portion (amount) of the tip that strikes the cb?
Here's why I ask....
At max spin, with an 11.8mm nickel-shaped tip, the contact point on the tip is 0.6mm from the tip's edge. Max spin using an 11.8mm dime-shaped tip results in tip contact being 1.4mm from the tip's edge.
With the average contact patch being about 4mm in diameter, it seems like the 0.6mm hit would have less "bite" on the cb, compared to a 1.4mm hit (tip contact point).
Along this same line of thinking, it seems that maximum spin would then be the result of striking the cb so that a full contact patch is achieved on the outermost portion of the tip (allowing room for a full contact patch). Am I making sense? Lol
If so, then max spin would be acheived by aiming to strike the cb 1 to 2mm thicker (closer to center), to get more bite, to get a larger contact area between the tip and the ball. The closer the contact point is to the edge of the tip, the smaller the contact patch will be (smaller amount of tip surface being used). So it seems like aiming for max spin near the miscue limit could actually create less spin than aiming a touch thicker.
What do you think?
Please shoot this theory down immediately if either of you or Dr. Dave has already proven or disproven it.
It could be tested if you have a way to measure spin, like angle change off a rail.
pj
chgo
pj
chgo
WobblyStroke
Well-known member
or go high tech and put those little reflective dots on the ball like they do golf balls and measure exact spin with tracman or GCquad.
Either way, whether perception of where the tip is hitting is different, or whether contact surface between tip and CB, or whether the 5.7% displacement actually causes a noticeable amount of spin difference.... I experience more spin with smaller diameter, rounder tips. Would be nice to have that spin data tho.
The math looks promising, and it may explain the reason why an 11.8mm tip witg a dime radius feels more effective when applying spin.
Using 4mm as an average diameter for a contact patch, the following percentages can be calculated pertaining to contact patch area used at max spin:
Nickle Tip
12.8mm tip allows for 88% of a 4mm contact patch.
11.8mm tip at allows for 72% of a 4mm contact patch
Dime Tip
12.8mm tip allows for 100% of a 4mm contact patch
11.8mm tip allows for 97% of a 4mm contact patch
This shows that an 11.8mm dime shape tip allows for more area of the tip to contact the cb, which could give it a substantially bigger bite of the ball. It's not as much as a 12.8mm with a dime shape tip, but it could explain why some of us say we get more spin with a smaller shaft. Most smaller shafts likely have tips that are dime shaped, while thicker shafts are nickel shape.
Looks like the dime shape could be most efficient and most effective, especially on a bigger/thicker shaft.
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I think the contact patch has an effective center. There will be different tip/ball pressures in different parts of the contact patch, and you have to weight the pressure (force) over the area of the patch. The effective center is probably going to be pretty close to the geometric center and that is probably where the maximum pressure is.
In addition you have the problem that for an off-center hit, the ball is rotating while the tip is on the ball, which means that the contact patch changes shape and location during the hit. That means that the effective "lever arm" (eccentricity of hit) changes during tip/ball contact.
(Off-topic, but that last point is an argument against trying to lengthen the tip-ball contact time. If the tip stays on the ball for longer it rides around the ball into the miscue zone, and you will get a partial miscue which has mostly the right spin and direction. Also, the average "lever arm" for a soft tip is reduced because you have to start the tip closer to center to avoid that partial miscue.)
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WobblyStroke
Well-known member
Check out this slow mo vid by Dr. Dave... The first shot is a draw shot which clearly shows the tip make contact, compress (so nearly half the tip is in contact with the ball), then ride down the ball as Bob pointed out (as in remains in contact at same point of contact but releases lower, not sliding on to different parts of the ball....which is how I erroneously misread Bob's post at first).
Either way, it appears as though, once you factor in tip deformation at contact, the contact patch is much larger than the 4mm you used above.
Regarding the miscue zone, it does seem like a rounder tip would allow you to ride around the ball a bit more without that partial miscue happening compared to a nickel shaped tip. Whether that amounts to more than JJ's 5.77% I don't know.
4mm is considered the average size contact patch for normal speed. What Dave shows in the video is slow motion fast-speed hits, so the tip definitely compress more. Neat video.
So...despite the contact patch changing shape and location as it grabs the ball and the ball begins to move, wouldn't a bigger contact patch (more tip surface touching the cb) be a more effective/forceful "lever arm" to generate spin?
Or do you think a contact patch of 9 sq-mm would produce the same spin as a contact patch of 12 sq-mm, all else being equal (same speed and same applied english/off-center hit)?
The only difference would be tip radius. One tip allowing for 100% of available tip surface to contact the cb, and the other only allowing for 75% of available tip surface to contact the cb.
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As long as the tip does not slip on the ball, the size of the contact patch is irrelevant.
Lol. Let me reword this. I am asking if a bigger contact patch would grab the cb better than a smaller contact patch. Two identical strokes, the only difference being tip radius. One tip allowing for 100% of available tip surface to contact the cb, and the other only allowing for 75% of available tip surface to contact the cb.
You say as long as the tip doesn't slip, the contact patch is irrelevant. But wouldn't a larger surface contact area between tip and ball be less prone to slipping, and therefore grip the ball better?
I mean, what causes a miscue? I thought it was because we aim too far from center cb to allow enough tip surface to grab the ball, so the tip slips off the ball.
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WobblyStroke
Well-known member
yep. But when we are talking about max spin and 3 cushion draws, we really are talking about these higher speed hits.
Yes, but would a larger contact patch make it more likely that some portion of that patch remains in contact with the ball longer than a smaller patch which also doesn't slip but loses contact completely sooner? It would make sense to me for a bigger contact patch that comes off the ball gradually to remain in contact with the ball for a longer time with at least some part of it, allowing the cue to impart for force/spin on the ball.