Object ball on low deflection cue
- Thread starter giulichajari
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Read it. Good info that goes right along with I'm saying about shaft deflection. Greater shaft end mass produces more cb squirt. Lesser end mass produces less cb squirt. This is because the larger cue shaft mass will impact the cb's path more than it will impact the shaft's path. But if the last few inches of the shaft can be made significantly lighter, and the shaft has enough flexibility/whip to allow for good deflection, the cb path will be less impacted by the shaft's end mass, causing the shaft to squirt/deflect from its directional path instead of forcing the cb to squirt off its path.
We're probably saying the same thing, only in different ways.
I’m going in circles given this link. Low deflection can mean flex but not necessarily?
Does this mean that higher end mass = a minimally yielding cue stick path = a yielding (normal/high deflecting) cueball path? Conversely lower end mass = a yielding cue stick path = a minimally yielding (low deflecting) cue ball path?
Does a lower end mass (yielding) cue stick occur in one of two ways? Either it flexes...or it’s trajectory stiffly redirects off the cueball without flex. Does a low deflection cueball path = a high deflection shaft path?
As a thought experiment I’m thinking about a bamboo stick meeting the curve of a concrete ball versus a steel rod meeting the curve of a beach ball.
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Good stuff. The term "deflection" is often used incorrectly to describe the CB action after impact. But since the ball is stationary, there is no direction from which to be deflected. The shaft has an initial direction (stroke line), and when it confronts the sideways force (from striking the cb off-center) it gets deflected from its initial path. The cb isn't deflected from any initial path. It is pushed away from its intended path, or squirted off its course, hopefully swerving back on the intended path before it meets up with the ob.
Exactly, that's how I see it. But if the bamboo stick was super stiff, having zero flexibility, and the bridge hand and grip could remain fixed with no allowance for give, the bamboo would either break or force the bowling ball to squirt sideways. However, with enough flexibility the bamboo would deflect away from the bowling ball, reducing any squirt
action.
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Another option for the super stiff bamboo stick and fixed bridge hand would be your back hand feel a force pulling it towards or away from your body.
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CB deflection (squirt) directly depends only on the "endmass" of the shaft. However, shaft stiffness can have an indirect effect on shaft "endmass" per the info here:
squirt (CB deflection) endmass and stiffness effects
A shaft that is very whippy (not very stiff) will create lots of CB deflection (squirt) if it is heavy close to the tip (e.g., due to a heavy tip or ferrule, or due to dense, solid material in the shaft end). A stiff shaft (e.g., carbon fiber) can be very light close to the tip and produce very little CB deflection (squirt).
The key is the amount of endmass, not the amount of flex. Mass has inertia, and if you push against it, it pushes back. See the what causes squirt? resource page.
I am assuming the concrete ball is much larger than a pool ball; otherwise, the bamboo and pool-size concrete ball might behave similarly to a pool cue and pool ball (assuming the tip and ball surface were similar to pool conditions).
With a large, heavy concrete ball, if the bamboo had a tip similar to a pool cue, and the surface of the concrete were similar to a pool ball, there would be a miscue due to inadequate friction to rotate the concrete ball. And, theoretically, if there were enough friction to prevent a miscue, the bamboo would buckle out and snap. In either case, the concrete ball would not move or deflect very much.
The steel rod would deflect very little, and the beach ball would deflect a lot (whether there was a "miscue" or not).
For other useful "thought experiments," see the actual experiments here:
NV B.32 - Squirt and the effects of endmass
Diagram 4 in "Squirt - Part VII: cue test machine results" (BD, February, 2008)
Regards,
Dave
"CB deflection," as the term is commonly used, refers to the squirt of the CB away from its intended or expected path (assuming no squirt). The term "deflection" is also commonly used for the net effect of squirt and swerve (AKA squerve), referring to the deflected position (from the expected shot line) at the OB contact point.
Regards,
Dave
Is it at least fair to say this? (My hypothesis)
Because of the curve of the ball, both the stick and the cueball will have their trajectory redirected from their initial alignment. With greater stick end mass, the cueball is redirected more and the stick is redirected less. With less end mass, the stick is redirected more and the cueball is redirected less.
Stick redirection is very much like a miscue except. A miscue has minimal friction during the moment of impact causing greater stick redirection. A LD impact still redirects the stick but there is friction at the point of impact (thanks chalk!).
And ultimately that redirection comes in the form of a stiff stick pivoting some off the fulcrum of the bridge, or comes in the form of a whippy stick flexing. (Acknowledging that a whippy stick with high end mass with not be low deflection).
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Because of the curve of the ball, both the stick and the cueball will have their trajectory redirected from their initial alignment. With greater stick end mass, the cueball is redirected more and the stick is redirected less. With less end mass, the stick is redirected more and the cueball is redirected less.
Stick redirection is very much like a miscue except. A miscue has minimal friction during the moment of impact causing greater stick redirection. A LD impact still redirects the stick but there is friction at the point of impact (thanks chalk!).
And ultimately that redirection comes in the form of a stiff stick pivoting some off the fulcrum of the bridge, or comes in the form of a whippy stick flexing. (Acknowledging that a whippy stick with high end mass with not be low deflection).
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Sounds good to me.
This is usually true, but the end of the cue can be very light and still be stiff, where both the CB and shaft "deflection" will be small. Again, it is the "endmass" and not the shaft stiffness that affects squirt.
Again, for those interested, this topic is covered in great detail, with explanations, illustrations, videos, and articles on the what causes squirt? resource page.
FYI, the bridge has no effect on squirt, per the info here:
non-effects of bridge length on squirt
Enjoy,
Dave
Greens to Dave (after I spread some more around) for taking the time to share his extensive knowledge about this stuff.
pj <- he could be a Professor of Pool
chgo
You're welcome. I aim to swerve. :grin-square:Greens to Dave (after I spread some more around) for taking the time to share his extensive knowledge about this stuff.
I have a BU Doctorate of Pool, and I'm the Dean and a Founding Professor of the BU. Does that count?
Regards,
Dave
The reason I’m harping on this is only because the common guidance about end mass around here (often quoting Dave) also de-emphasizes shaft flexibility to the point of being a non-factor. Yet this segment from Dave’s site indicates it can be relevant (when paired with / equated to low end mass).
Again, trying my best to put aside a hypothetical high end mass + flexible shaft scenario.
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Again, trying my best to put aside a hypothetical high end mass + flexible shaft scenario.
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Shaft stiffness has an indirect effect on shaft "endmass" (per the explanations on the endmass and stiffness resource page), but it is not as big of a direct factor as some people think, per the analysis in TP B.19 - Comparison of cue ball deflection (squirt) "endmass" and stiffness effects.
Per the experiment in Diagram 4 of "Squirt - Part VII: cue test machine results" (BD, February, 2008), if mass is added (or removed) from the end of a shaft, without changing the shaft stiffness, squirt (CB deflection) will be increased (or decreased).
Again, for those who want to learn more, what causes squirt? is a good place to start.
Regards,
Dave
It is a non-factor in practical terms. According to Dave's calculations (endmass and stiffness), shaft stiffness contributes less than 2% (1/50) of total squirt. The difference from one shaft to another is a fraction of that.
That's why it's common guidance.
pj
chgo
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Fair enough. I knew I’d be back here.
The big thing I’m seeing is that the stick must give so the cueball doesn’t have to. The tip will move along the curve of ball and ultimately out of the way of the ball (similar to a miscue but with friction) with a LD hit. It will move laterally because it has less mass toward the tip, meaning the cueball gives it more inertial resistance (it’s not a beach ball). How the tip moves laterally can either be flex or simply the entire stick’s trajectory is rerouted. Whichever mechanism allows the movement isn’t as influential as the fact that it does move. The amount of movement to affect squirt appears minimal because the moment of contact is so short. We are talking millimeters of shaft “give” to affect a degree or two of less squirt. The kinds of things the human eye sees aren’t as influential because those are macro observations that don’t effect the micro scale of the moment of impact, e.g. big staff bend, wobble or just steering the ball.
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The cue does flex (deflect) and vibrate a lot after impact (due to the momentum imparted during tip contact), but this occurs after the CB is gone and has nothing to do with squirt. For good demonstrations of this, see the slow-mo videos on the cue vibration resource page.Fair enough. I knew I’d be back here.
The big thing I’m seeing is that the stick must give so the cueball doesn’t have to. The tip will move along the curve of ball and ultimately out of the way of the ball (similar to a miscue but with friction) with a LD hit. It will move laterally because it has less mass toward the tip, meaning the cueball gives it more inertial resistance (it’s not a beach ball). How the tip moves laterally can either be flex or simply the entire stick’s trajectory is rerouted. Whichever mechanism allows the movement isn’t as influential as the fact that it does move. The amount of movement to affect squirt appears minimal because the moment of contact is so short. We are talking millimeters of shaft “give” to affect a degree or two of less squirt. The kinds of things the human eye sees aren’t as influential because those are macro observations that don’t effect the micro scale of the moment of impact, e.g. big staff bend, wobble or just steering the ball.
Regards,
Dave
I understand the double use of the term "deflection" in pool. Just never liked the muddying up of terms.
Common sense is not so ambiguous. I mean, if I am skiing downhill in a straight line and hit the side of a barrel, I will be deflected from my path. The barrel will be pushed/knocked/shoved out of the way, squirting off at an angle according to where I hit it in relation to its center of mass. I was already on a path and got deviated from it, deflected. The barrel was not in motion, not on any path until I struck it and pushed it down a specific path.
I believe I read in your material somewhere that the shaft deflects and the CB squirts. This is the most straight forward way to say it. I get that after the cb begins its initial travel it can swerve back to an intended path, but saying squirt + serve = deflection is sort of muddying up the terminology. But I didn't invent the words so I guess anybody can say they mean whatever they want them to mean.
I just find it funny that LD shafts that are designed to maximize tip deflection off the CB, but they called "low deflection shafts"... I suppose it's more marketable than "Low Squirt Shafts".
Lol!
Fair enough. I knew I’d be back here.
The big thing I’m seeing is that the stick must give so the cueball doesn’t have to. The tip will move along the curve of ball and ultimately out of the way of the ball (similar to a miscue but with friction) with a LD hit. It will move laterally because it has less mass toward the tip, meaning the cueball gives it more inertial resistance (it’s not a beach ball). How the tip moves laterally can either be flex or simply the entire stick’s trajectory is rerouted. Whichever mechanism allows the movement isn’t as influential as the fact that it does move. The amount of movement to affect squirt appears minimal because the moment of contact is so short. We are talking millimeters of shaft “give” to affect a degree or two of less squirt. The kinds of things the human eye sees aren’t as influential because those are macro observations that don’t effect the micro scale of the moment of impact, e.g. big staff bend, wobble or just steering the ball.
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That's why I used a steel rod and an aluminum rod in my tests. Both shafts caused extreme cb squirt, no miss cues, though the steel rod had considerably more end mass. The aluminum rod was lighter than the cb, but it was too stiff to allow for any whip or flexing, so its super light end mass wasn't enough to decrease cb deflection/squirt. This means without some shaft give, some flexibility, end mass isn't a factor. Of course, your bridge hand and/or grip hand gives way to a stiff shaft deflecting, so maybe that's why stiffness doesn't affect the squirt too much. :shrug:
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LD shafts aren't "designed to maximize tip deflection off the CB", because that wouldn't help materially with low deflection - because (again) shaft deflection has insignificant effect on squirt.I just find it funny that LD shafts that are designed to maximize tip deflection off the CB, but they called "low deflection shafts"... I suppose it's more marketable than "Low Squirt Shafts".
pj
chgo