Squirt. End Mass and Cue Flexibility.

LAMas

AzB Silver Member
Silver Member
For all these years, It has been held here that only end mass determines squirt and when I proffered that I thought that the flexing or bending of the shaft is also an important component, I and others were dismissed. One need not be a scientist to have good intuition and conscious reasoning, but here one is dissed unless he has a pedigree above that of a pool player.

I just found this old paper from 2006 that I had not been pointed to before here on AZ Billiards Forum since I joined 2003. I wonder but will not ask why?


Cue and ball deflection (or “squirt”) in billiards
Rod cross
Physics Department of Sydney, Sydney NSW 2006, Australia

VII Conclusion

....The experimental data shows that elasticity of the cue tip plays a dominant role in the collision process and suggests that cues with thin shafts might generate lower squirt angles as a result of their greater flexibility rather than their lower mass...

Acknowledgements
This article was inspired by previous theoretical efforts by Ray Higley and by Professors David Alciatore and Ron Shepard, concerning the origin of squirt in billiards,

http://www.physics.usyd.edu.au/~cross/PUBLICATIONS/39. squirt.pdf

This scientist could also be wrong even with an overhead camera and accelerometers etc,.

Be well
 

Bob Jewett

AZB Osmium Member
Staff member
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For all these years, It has been held here that only end mass determines squirt ...
I have held in the past that stiffness can affect squirt. It clearly will determine how much of the front of the stick will be included in the effective end mass. Whether there is a significant variation among maple shafts made by more or less standard methods including coring is a good question. What is clear is that weight near the front of the cue can have a large effect as shown by a lot of low-squirt designs (and Mike Page's vise-grips experiment).

Cross in his paper also says that the elasticity of the tip is important to squirt but that seems not to show up in the typical range of leather tips. Further, phenolic tips, which I would describe as inelastic for Cross' use, seem to have the same squirt characteristics, more or less, as leather tips.
 
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LAMas

AzB Silver Member
Silver Member
I have held in the past that stiffness can affect squirt. It clearly will determine how much of the front of the stick will be included in the effective end mass. Whether there is a significant variation among maple shafts made by more or less standard methods including coring is a good question. What is clear is that weight near the front of the cue can have a large effect as shown by a lot of low-squirt designs (and Mike Page's vise-grips experiment).

Apples and oranges?
What if the vise grip was attached to a noodle? :)
In the "past" you were intuitive as are many pool players that are not scientists.

Be well
 

KMRUNOUT

AzB Silver Member
Silver Member
I haven't read all the stuff on Dr. Dave's site about squirt, but I think he also says that shaft flexibility has *some* effect. I don't know how much effect. It does seem to me like it must play at least some role.

I guess the main argument against it is that the time it takes the compression wave, or is it the "transverse" wave? IDK...some wave..lol. Anyway the time it takes that wave to move down the shaft and cause the shaft to bend, the cue ball is already long gone.

This makes a lot of sense. I think there might be some high speed video to support this as well.

Good question though.

KMRUNOUT
 

LAMas

AzB Silver Member
Silver Member
I haven't read all the stuff on Dr. Dave's site about squirt, but I think he also says that shaft flexibility has *some* effect. I don't know how much effect. It does seem to me like it must play at least some role.

I guess the main argument against it is that the time it takes the compression wave, or is it the "transverse" wave? IDK...some wave..lol. Anyway the time it takes that wave to move down the shaft and cause the shaft to bend, the cue ball is already long gone.

This makes a lot of sense. I think there might be some high speed video to support this as well.

Good question though.

KMRUNOUT

I think that compression effects a transverse wave which implies that depending on the frequency, the CB could feel a few compressive forces during contact according to the article.

Be well
 

336Robin

Multiverse Operative
Silver Member
Interesting Paper

Lamas,
Interesting Paper but its 5am so I read some scanned some and went to the conclusion. There was a statement in this paper that I use that applies to aiming I found interesting verifying a theory of mine but again its 5am.

I would have thought that shaft flexibility would have been included a long time ago in this theory but apparently it hasn't been after all the cue ball does have a weight and that weight would cause resistance to the stroke, none of which I could measure however I have seen a local painter here who also is a pool player who took a shaft and made it very whippy on home lathe and seems to play very well with it.

I would guess that further conversation concerning squirt will now cover shaft stiffness and butt flexibility as part of the equation and it rightfully should if it can be determined that there is a point that is physically attainable in a practical sense that those parameters can be obtained and used within the confines of a cue stick that can be used for normal play. The first question here being is the data from the Meucci test that seems to come up from time to time about butt flexibility and what was actually found out and it seems that there was some shaft and butt combinations that produced a lot less squirt than expected. I think I read some cautions about the efficacy of that testing as well due to the way things were setup for testing so we have more variables. Nice Post. I am not someone who understands anything really about Physics but I have worked with squirt and squirt variables enough to it can be understood enough by laymen such as myself to be able to put it into a plan where shots work out as planned but you have to adhere to one thing. You have to stroke as chosen in the planning phase. Nice one, Kudos.

What happened to PJ's thread on Swoop Stroke?

Robin

For all these years, It has been held here that only end mass determines squirt and when I proffered that I thought that the flexing or bending of the shaft is also an important component, I and others were dismissed. One need not be a scientist to have good intuition and conscious reasoning, but here one is dissed unless he has a pedigree above that of a pool player.

I just found this old paper from 2006 that I had not been pointed to before here on AZ Billiards Forum since I joined 2003. I wonder but will not ask why?


Cue and ball deflection (or “squirt”) in billiards
Rod cross
Physics Department of Sydney, Sydney NSW 2006, Australia

VII Conclusion

....The experimental data shows that elasticity of the cue tip plays a dominant role in the collision process and suggests that cues with thin shafts might generate lower squirt angles as a result of their greater flexibility rather than their lower mass...

Acknowledgements
This article was inspired by previous theoretical efforts by Ray Higley and by Professors David Alciatore and Ron Shepard, concerning the origin of squirt in billiards,

http://www.physics.usyd.edu.au/~cross/PUBLICATIONS/39. squirt.pdf

This scientist could also be wrong even with an overhead camera and accelerometers etc,.

Be well
 

dr_dave

Instructional Author
Gold Member
Silver Member
I haven't read all the stuff on Dr. Dave's site about squirt, but I think he also says that shaft flexibility has *some* effect. I don't know how much effect. It does seem to me like it must play at least some role.
First of all, it is important to distinguish between a cue's stiffness in the axial or longitudinal direction and stiffness in the sideways or transverse direction.

For a cue to be able to hit a CB effectively, it must have significant stiffness in the hitting direction (i.e., it must have a large axial of longitudinal stiffness). That's why any theoretical discussion like "What if the cue were a noodle?" is just downright silly (unless the "noodle" is fat and dry, and is able to resist buckling and fracture during a hit :grin-square:).

The sideways or transverse stiffness of the cue is much less than the axial or longitudinal stiffness (i.e., the cue is very flexible in response to sideways deflection; and these sideways deflections are very small anyway during an off-center hit, due to the incredibly brief tip contact time). However, transverse stiffness does affect the effective endmass of a shaft and amount of resulting CB deflection (squirt). A complete and detailed explanation of this, supported by numerous resources can be found here:

cue endmass and stiffness effects

Concerning the effects of tip elasticity; theoretically, one would think this would have a large effect on tip contact time and resulting squirt; but in reality, with real tips on real cues, the difference in squirt over a wide range of tip types and hardnesses is miniscule (i.e., of no practical significance). For proof, see cue tip hardness effects and the following video:

NV D.15 - Cue and Tip Testing for Cue Ball Deflection (Squirt)

Enjoy,
Dave
 
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garczar

AzB Silver Member
Silver Member
I remember when Bob Meucci came out with the '79 brochure. It had references to deflection and everyone looked at each other and said "WTF is deflection?" Cues in those days were mostly steel-jointed, ivory-ferruled telephone poles. Bob's cues felt like a 58" buggy whip but whatta' ya' know, they freakin' played awesome. At almost any big tourn. for 25yrs. almost all the top players played with one. Trendsetting cues for sure.
 

336Robin

Multiverse Operative
Silver Member
Absolutely!

I remember when Bob Meucci came out with the '79 brochure. It had references to deflection and everyone looked at each other and said "WTF is deflection?" Cues in those days were mostly steel-jointed, ivory-ferruled telephone poles. Bob's cues felt like a 58" buggy whip but whatta' ya' know, they freakin' played awesome. At almost any big tourn. for 25yrs. almost all the top players played with one. Trendsetting cues for sure.

Absolutely, the only thing I am unsure of is the size of the ferrule. I guess I like the idea of the smaller ferrule. His designs went way into the demographic of the Amateur Pool Player. Great marketing techniques.
 

Bob Jewett

AZB Osmium Member
Staff member
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Silver Member
"I have held in the past that stiffness can affect squirt...."
Bob Jewett

Was that intuition or an empirical deduction?

Be well
It was rough analysis based on transverse wave propagation. Stiffness affects the effective "impedance" of the interaction.

But I think a good scientist (or anyone who tries to understand how things work) relies on intuition to find promising directions. The important part comes after the direction is decided -- the analysis and objective testing of the idea begins.
 

ENGLISH!

Banned
Silver Member
I remember when Bob Meucci came out with the '79 brochure. It had references to deflection and everyone looked at each other and said "WTF is deflection?" Cues in those days were mostly steel-jointed, ivory-ferruled telephone poles. Bob's cues felt like a 58" buggy whip but whatta' ya' know, they freakin' played awesome. At almost any big tourn. for 25yrs. almost all the top players played with one. Trendsetting cues for sure.

-------:thumbup2:------

I never did like the whippy shafts, though. I was playing with a European/ conical tapered house cue that I had made into a Sneaky back then. I'm playing with a conical taper OB Pro now but with an 11.75 mm tip vs a nearly 13 mm tip back then.

Low front end mass & flex do not need to be mutually exclusive. There does NOT have to be only one contributing factor or parameter that contributes to reducing squirt.

Bob Meucci now has what he calls his Power Piston Butts.

In golf there is shaft flex that most are familiar with but then there is what Dr. Dave mentioned which in golf shafts is referred to as torque. When graphite shaft manufacture came along & given the extensive research & development for golf because of the huge monetary incentive it opened up a whole new area of shaft fitting for individual golf swings. It allowed different shaft 'flexes' to be matched up with different degrees of torque.

Bobby Jones hated his hickory shafted 7 iron. When technology allowed for testing an intact golf club & his set was tested all of his hickory shafted irons were very close but the 7 iron was way off & very different.

If the monetary incentive ever came along, I would not doubt that there would be synthetic material pool cue shafts being manufactured & used.

Best Wishes 2 You & All.
 
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Corwyn_8

Energy Curmudgeon
Silver Member
I haven't gotten all the way through it, but I did notice:

"The ball therefore rotates about two different axes simultaneously."

Which would appear to violate Euler's rotation theorem which states that "any displacement of a rigid body such that a point on the rigid body remains fixed, is equivalent to a single rotation about some axis that runs through the fixed point.".

One could argue that the point is semantic, but I wouldn't expect such a fundamental mistake in a peer reviewed article.

Thank you kindly.
 

336Robin

Multiverse Operative
Silver Member
What about Top Right or Left?

Im not qualified to talk about such but what about off center hits, high or low? Do they not spin sideways while rotating end over end to some degree?
 

Patrick Johnson

Fish of the Day
Silver Member
I have held in the past that stiffness can affect squirt. It clearly will determine how much of the front of the stick will be included in the effective end mass.
Do we have a sense for what fraction of total squirt effect is caused by end mass (including stiffness determining that) vs. stiffness directly resisting the CB's rotation?

I'm guessing direct resistance from stiffness is a very small part of the equation...

pj
chgo
 

LAMas

AzB Silver Member
Silver Member
It was rough analysis based on transverse wave propagation. Stiffness affects the effective "impedance" of the interaction.

But I think a good scientist (or anyone who tries to understand how things work) relies on intuition to find promising directions. The important part comes after the direction is decided -- the analysis and objective testing of the idea begins.

I concur.

"In the past" your intuition was correct. Today there is more empirical evidence of that.

"Stiffness affects effective impedance" ergo, stiffness is a component of "effective end mass" and not just the static weight (mass) of the front of the shaft alone.

Back 50 years ago, I used to sand my shaft diameter down and because being thinner it was easier to see the axial line. For me and without any instrumented empirical evidence, thought it played better as well and noticed it would bend away. Today I use a Z2 for the same reasons and no more sandpaper.

That's all and not a dig on your "past" if that was what you took away. I have learned a lot from you.

The article is what it is and it's conclusion can be challenged.

Thanks and be well.
 
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Jal

AzB Silver Member
Silver Member
For all these years, It has been held here that only end mass determines squirt and when I proffered that I thought that the flexing or bending of the shaft is also an important component, I and others were dismissed.
It is only endmass in the following sense:

1) The cueball is deflected in the transverse direction according to the mass of the cue that's put into motion in the opposite direction (momentum). If the end of a cue was perfectly rigid, but somehow lacked any effective endmass, no squirt would take place.

2) Stiffness, but in a sort of trivial way, is necessary for there to be any endmass at all (see Dr. Dave's reference to a wet noodle earlier). However, once you get to a stiffness level represented by a wooden rod, the differences in stiffness you're going to encounter amongst cues isn't likely going to make any significant difference in squirt. That's because:

2.1) Given the shape the end of the cue takes on as it bends, it's the mass nearest the tip that contributes the most to the momentum of the endmass.

2.2) Different stiffnesses primarily affect the shape of the bend further down the cue away from the tip. Because of that location, the additional mass doesn't contribute much to the cue's sideways momentum.

I once thought that stiffness was an integral part of endmass (it is in the trivial sense noted above), but repeated assertions by Patrick Johnson and Dr. Dave eventually drove home the "proper" view of it.

Now you can go. :) :)

Jim
 

Patrick Johnson

Fish of the Day
Silver Member
I haven't gotten all the way through it, but I did notice:



Which would appear to violate Euler's rotation theorem which states that "any displacement of a rigid body such that a point on the rigid body remains fixed, is equivalent to a single rotation about some axis that runs through the fixed point.".

One could argue that the point is semantic, but I wouldn't expect such a fundamental mistake in a peer reviewed article.

Thank you kindly.
You can express the same rotation as either rotation about a single axis or as the combined "components" of rotation about multiple axes.

For instance, a rolling ball with side spin rotates about a single tilted axis, which is also the combined components of rotation about the vertical axis and a horizontal axis. We choose to separate the single axis of rotation into vertical and horizontal rotational components because pool is played on a horizontal surface with vertical surface boundaries (rails), so those are the effects that matter most.

pj
chgo
 

dr_dave

Instructional Author
Gold Member
Silver Member
Do we have a sense for what fraction of total squirt effect is caused by end mass (including stiffness determining that) vs. stiffness directly resisting the CB's rotation?

I'm guessing direct resistance from stiffness is a very small part of the equation...
I haven't calculated and/or measured this before, but I'll add it to my list.

I would suspect that the direct stiffness effect would be a tiny fraction (maybe less than 1%) of the effective endmass effect.

I'll reply to this post if and when I'm able to do the calculations.

Regards,
Dave
 
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