phreaticus
Well-known member
Thats my take on it. I think we’re down to minuscule differences in time duration that the tip is actually contacting the cue ball. I think thats essentially whats going on with soft vs hard tips also.
Tip shape
- Thread starter dquarasr
- Start date
Friction is complicated. You could argue that the smaller tip with the higher pressures and forces bites into the ball better. Or you could argue the other way. I think the argument in either direction is not useful unless someone can demonstrate convincingly a benefit in play.
Max spin can be on a soft soft also. Of course, for faster shots the contact patch is much bigger than 4mm. But you'd have to be playing with a 14mm shaft to get 100% of a bigger contact patch.
And I understand what Bob is saying, that the force gets spread out over the patch area, but mostly concentrated at the point of impact. I agree with this, more so for a hard tip than soft. With a soft tip that compresses quite a bit, I'd say the force gets distributed pretty well across a bigger portion of the patch.
Not sure what difference any of it makes. But there has to be a reason why I and many others can tell a difference in spin amounts between smaller and bigger shafts, or between soft and hard tips, or between nickel and dime shaped tips.
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I think it's the increasing "slope" of the surface we're hitting - at center ball the surface is 90 degrees from the stick's angle of direction, but at the miscue limit it's sloped 30 degrees from the stick's direction.
pj
chgo
Yes, we aim so far from the center of the ball that there isn't enough tip-to-ball contact (friction) to grab or grip the ball.
And sure, as we approach maximum spin limits, the slope of the ball ducks away pretty quickly and the contact point ends up being on the outer edge of the tip, very little friction. That's miscue land for sure.
But what about that occassional miscue when we're not dancing around the outer borders of applying spin? With no friction between the tip and ball a miscue can occur just by aiming to apply a touch of spin, just 1 or 2 millimeters from a center ball hit.
When aiming left or right of center cb, isn't it Iike this?....
No friction between tip and cb = miscue and no spin
Friction = spin
Less friction = slippage, less spin but likely a partial miscue.
More friction = more spin, no miscue
I think it's rarely if ever the size of the contact patch - just that the steeper slope is more prone to slippage. If it was about the size of the contact patch, different tips would have different miscue limits - but they don't, far as I know.
pj
chgo
For shots beyond the miscue limit I agree.
But for max or near max spin, when the contact point on the tip surface is only a fraction of a millimeter from its edge, a full circle contact patch isn't created, unless you're using a 12.8mm tip with a dime shape. Using an 11.8 with a nickel shape will create a contact patch that looks like a 3/4 moon (waxing gibbous), where 25 to 30% of the possible tip-to-cb surface area isn't there to help grab and spin the cb.
I bet you could come up with a neat experiment to prove or disprove any benefits from having a 100% full contact patch. Lol. Let me know what you find.
How do you get these contact patch sizes? And is there any direct evidence that size matters?
pj <- not arguing yet
chgo
Size does matter. Don't let those women lie to you. Lol. Just kidding.
I used an average size contact patch of 4mm in diameter, according to Dr. Dave's material. Of course at faster speeds the patch is bigger, and at slower speeds it's smaller. And tip hardness plays a role also.
A 4mm patch has an area of 12.6mm². So that's what I used as my main/normal reference, a 100% patch.
Now, doing a little math shows that if we use an 11.8mm tip with a nickel radius, and aim to produce maximum spin, the point of contact on the tip will be 0.7mm from its edge. If we strike the cb at the correct speed to produce an average 4mm diameter contact patch, the center of the patch will be at this contact point.
With the center of our 4mm diameter patch only 0.7mm from the tip's edge, we won't get the full patch, because a 1.3mm chunk of it will be lost outside the edge of the tip. So the resulting contact patch won't be a complete circle of 12.6mm².
Doing a little more math shows that the portion lost outside the tip's edge is 3.5mm², which is about 28% of the patch's area if we had a big enough tip to get a full contact patch. Instead, we have a contact patch area that is 72% of what a full patch would be.
Using the same figuring based on a 12.8mm tip with a dime radius, we get a tip contact point that is 2.5mm from the tip's edge. So a 100% full contact patch (4mm diameter, 12.6mm² area) will fit the surface of the tip, and with half a millimeter to spare before reaching the edge of the tip.
This sketch is bit confusing, but it's a magified (10x) view of a tip. The right side is a nickel radius, left side is dime. The highlighted areas show how the 4mm contact patch fits the available tip surface. I'd like to redo the drawing, clean it up and get rid of a lot of the lines and unneeded measurements.
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You guys are a lot smarter than me so I’m just gonna throw this out as a hypothesis for you to ponder and i am curious to the replies
first assumption
the farther you go from center cue ball on the horizontal axis the more spin you get
so a pinpoint hit at the ultimate farthest spot from the center you can hit before miscue should produce the most spin
the smaller the spot the more concentrated the full impact is produced
so the “tighter” the hit spot the more spin
jmho
icbw
your thoughts greatly appreciated
first assumption
the farther you go from center cue ball on the horizontal axis the more spin you get
so a pinpoint hit at the ultimate farthest spot from the center you can hit before miscue should produce the most spin
the smaller the spot the more concentrated the full impact is produced
so the “tighter” the hit spot the more spin
jmho
icbw
your thoughts greatly appreciated
phreaticus
Well-known member
H
Hey, maybe this is why I settled into 12.5 mm w/medium-soft dime shaped tip as my preferred weapon of choice.
That's supposed to be correct. Not sure about the "smallest" spot being more concentrated though.
If you were to slap someone in the face, a full open-handed slap hard enough to turn their head sideways, do you think the same slap speed with less of your hand making contact would turn the persons head just as quickly or forcefully? I don't think so.
In karate a strike with the tip of your index finger is powerfull
dr dave says this on his site in the section on tips size and effects
...............
...............
- For shots with spin, the impact is more centralized to the core of the cue for a rounder tip. This might result in a better “feel” for some people with firm shots. Also, the efficiency of the hit might be slightly better since there will be slightly less cue vibration with the slightly-less offset from the cue’s center. Also, it has been suggested by Predator that a centralized hit helps reduce squirt. It certainly is true that if you remove more material by rounding the tip down to a dime, you might reduce endmass and squirt. Also, there might be less sideways tip and shaft flex with a more centralized hit, which could have an effect (see what causes squirt for more info).
- ...........................
- he also said this right after
- However, per the quotes from Patrick Johnson and Bob Jewett below, there really isn’t much difference between a “dime” shape and a “nickel” shape.
well you have a 19 oz cuestick behind the tip
just sayin
i should not speak for patrick but i want to post what patrick has posted in the past and is also on dr daves website
please give me a chance to post my comments after posting patricks material so i can explain my thoughts and how i think it relates to the discussion
please give me a chance to post my comments after posting patricks material so i can explain my thoughts and how i think it relates to the discussion
There are quite a few "might be" or "could be" statements there. And sure, as PJ and Bob J have said, there isn't much difference between a nickel and dime shaped tip.
But I find it hard to believe that striking the cb with more tip involved (a full 100% contact patch versus a partial contact patch) is insignificant. There is no data on it that I can find. So it's just as probable as any other "could be" or "might be" that Dr. Dave mentions in the above quote, though the math shows a big difference (nearly a 30% difference in the amount of tip surface area being used).
And too many experienced players have said that they get more action from different cues, different tips, so there's something to that. It's not simply that they "feel" like they get more action. They experience it, see it and feel it.