Squirt. End Mass and Cue Flexibility.

[dr_dave]

My question to Lamas was with regards to the initial bend of the shaft. Is the initial very short time bend with the end angled in toward center ball with the 'mid' of the bend bowed out away form the ball...

or is that absorbed by the tip & the compression of the tip & the 'mid' shaft flex bows in, as in your diagram?

If the velocity of the shaft is met with resistance on the inside, toward center ball, would not the 'mid shaft' bow out initially? Would not that be the initial compression of the shaft until it is released & then rides 'out' & away from the ball?

This is exactly what I am attempting to illustrate in the modified diagram. A portion of the end of the shaft does flex out as your describe (as the tip bends to point closer to CB center), but the overall motion and flex of the shaft is away from the CB as shown in the diagram. It is not the change in tip direction that causes squirt ... it is the overall motion and flex of the entire end of the shaft away from the CB (which is forced by the rotation the CB picks up very quickly during impact). For more info, see: what causes squirt.

Regards,
Dave

 

[ENGLISH!]

A swooping or swiping action does change the effective line of action of a shot slightly, but the speed of the swoop or swipe is typically small in comparison to the forward speed of the cue. Also, the speed at which the endmass momentum and flex effects take place (over the incredibly brief tip contact time) make any swooping or swiping speed insignificant in a practical sense.

For those interested, the effects of a swooping or swiping stroke are covered in detail with numerous explanations and illustrations on the swoop stroke resource page. Also included there is a carefully-designed experiment that can easily be used to demonstrate if any theories related to a swoop or swipe stroke have any practical merit.

Please don't turn this thread into what the swoop/swipe thread became before it was killed. It would be a shame if this fruitful thread were also lost for all eternity.

Regards,
Dave

Dave,

I alone have no power to turn any thread into "WHAT". It's statements like yours here that can get things headed into the WRONG direction.

 

[ENGLISH!]

This is exactly what I am attempting to illustrate in the modified diagram. A portion of the end of the shaft does flex out as your describe (as the tip bends to point closer to CB center), but the overall motion and flex of the shaft is away from the CB as shown in the diagram. It is not the change in tip direction that causes squirt ... it is the overall motion and flex of the entire end of the shaft away from the CB (which is forced by the rotation the CB picks up very quickly during impact). For more info, see: what causes squirt.

Regards,
Dave

Dave,

The discussions have been & are two fold & are not just about what causes squirt but also about what reduces squirt over a 'normal' shaft, what ever that really is.

In the old days, pool cues were mostly all 14 & 13 mm tipped European/Conical shaped from tip to butt & with rather heavy ferrules & they were rather if not very stiff.

Then modifications came on line like a 'Pro Taper' (first short & then longer) & a butt that became more narrow & parallel vs the conical taper & lighter ferrules & more pliable ferrules, then shorter ferrules & wood ring ferrules.

Science is continuing study & not some of the extremely definitive statements that are at times made only to be corrected or modified in a relatively very short time in the future.

We are very visual beings & diagrams that are not always completely accurate can sometimes give rather misleading impressions... especially when they get out of their complete context.

I'm just say'in.

 

[dr_dave]

This is exactly what I am attempting to illustrate in the modified diagram. A portion of the end of the shaft does flex out as your describe (as the tip bends to point closer to CB center), but the overall motion and flex of the shaft is away from the CB as shown in the diagram. It is not the change in tip direction that causes squirt ... it is the overall motion and flex of the entire end of the shaft away from the CB (which is forced by the rotation the CB picks up very quickly during impact). For more info, see: what causes squirt.

The discussions have been & are two fold & are not just about what causes squirt but also about what reduces squirt over a 'normal' shaft

To reduce squirt, you need to understand what causes it. What is currently known to cause it is "effective endmass" (and shaft flex, to a lesser extent). It has been convincingly proven through extensive analysis, testing, and cue design, that reducing the endmass of a shaft reduces squirt. For more info, see the squirt endmass and stiffness resource page. Until somebody can convincingly demonstrate squirt reduction through some other means, the current theories and experimental evidence will remain as our "current best understanding."

We are very visual beings & diagrams that are not accurate can give rather misleading impressions... especially when they get out of their complete context.

Rick,

If you think the illustrations, video demonstrations, analyses, and experimental evidence I and others have provided are inaccurate or misleading, please create and share your own resources and explanations that better describe and illustrate any alternative theories you might have.

Regards,
Dave

 

[ENGLISH!]

To reduce squirt, you need to understand what causes it. What is currently known to cause it is "effective endmass" (and shaft flex, to a lesser extent). It has been convincingly proven through extensive analysis, testing, and cue design, that reducing the endmass of a shaft reduces squirt. For more info, see the squirt endmass and stiffness resource page. Until somebody can convincingly demonstrate squirt reduction through some other means, the current theories and experimental evidence will remain as our "current best understanding."

Rick,

If you think the illustrations, video demonstrations, analyses, and experimental evidence I and others have provided are inaccurate or misleading, please create and share your own resources and explanations that better describe and illustrate any alternative theories you might have.

Regards,
Dave

Dave,

You very often make modifications & that is certainly a good thing. You have been VERY willing to do that whenever any possible error has come to your attention, That too is a good thing.

Sometimes in haste to make a point though, matters are not always presented that are fully representative. Everyone makes mistakes even when trying to do their best & making what is thought to be their best effort.

I merely made a general statement about how sometimes simple diagrams can not always be completely representative & can at times be misleading & as I said, especially when presented out of their full context.

If you took offense at that, then you did so where none was intended.

You have readily made quite a few updates, etc. recently to make matters more clear & that is certainly a good thing.

I think this thread was a good exercise to show that continued discussion & the ideas of others can be productive.

This thread & the swipe/swoop thread have led you to expanding & improving what you have to offer on your site.

IF ever I wish to produce any illustrations, video demonstrations, analyses, and/or experimental evidence I will certainly do so...

but...

I do not HAVE to do so just because I might see something that I think may not be complete or is inaccurate, or misleading.

I am not in any competition with you in any manner.

I merely made a general statement about the inefficiency that can sometimes be a diagram that can sometimes be the cause of confusion or incorrect conclusions.

I'm sorry that you seem to have taken that as a personal affront.

It certainly was NOT intended as such.

 

[LAMas]

Thanks Dave,

I can't really see in the video.

My question to Lamas was with regards to the initial bend of the shaft. Is the initial very short time bend with the end angled in toward center ball with the 'mid' of the bend bowed out away from the ball...

From the high speed vids:
As the shaft is stroked forward into say the left side of the CB, the right side of the "soft" dime radius leather tip starts to compress as it contacts and is resisted by the mass of the CB (6 ounces).

The tips becomes distorted and extrudes to the right as it continues to be compressed between the "angled side" of the stationary CB and the forward thrust of the shaft.

When the tip cannot be compressed any further, it becomes solid and the mass of the tip and shaft overcomes the CB's mass. The CB then starts to move CW about its center axis perpendicular to where it contacts the cloth.

The tip and front of the shaft moves and bends to the left because of the heavier mass of the CB while being restrained by the bridge and grip hand while in contact with and moving forward with the rotating CB.

As the CB accelerates away from the tip, the tip regains its original dime shape. The tip may push against the CB a bit as it recovers like a spring just before separation.

or is that absorbed by the tip & the compression of the tip & the 'mid' shaft flex bows in, as in your diagram?

If the velocity of the shaft is met with resistance on the inside, toward center ball, would not the 'mid shaft' bow out initially? Would not that be the initial compression of the shaft until it is released & then rides 'out' & away from the ball?

Thanks in advance,

PS EDIT: Dave, Is your diagram now representing a double "S" bend of the shaft?

My simplistic answer/comment to your question in green.

 

[ENGLISH!]

My simplistic answer/comment to your question in green.

Good Morning E,

If the right side of the shaft is met with the resistance of the cue ball, why would the shaft not have a slight brief bend with the tip more to the right as the shaft bows left...

Then as the ball rotates the front end & tip restore themselves & the tip & front end 'waffle' to the left with the bow to the right as the ball leaves to the right?

The above is what I see in my minds eye.

If we were to take a small diameter wooden dowel & angle it on a concrete floor & then load it with a force from the upper end, would the dowel not bow in the upward direction vs bowing downward?

If I'm missing something, what is it?

Best 2 Ya & Stay Well,
Rick

 

[Mr. Bond]

Hey Dave, Thanks again for all the info and effort, here and in the real world.
Being a teacher can be tough I'm sure. Many kids these days are less than pleasant to deal with.
Speaking of, have you ever had a student that, because of obvious self esteem issues, wanted to argue with you and nitpick ad naseum, even when they didn't actually fully understand the topic at hand, and all while using grammar and vocabulary that is clearly above their own intellectual level? ( to sound " grown up")

Props to you for dealing with students whose parents may not have spent enough time " learnin' the youngins"

 

[dr_dave]

Hey Dave, Thanks again for all the info and effort, here and in the real world.
Being a teacher can be tough I'm sure. Many kids these days are less than pleasant to deal with.
Speaking of, have you ever had a student that, because of obvious self esteem issues, wanted to argue with you and nitpick ad naseum, even when they didn't actually fully understand the topic at hand, and all while using grammar and vocabulary that is clearly above their own intellectual level? ( to sound " grown up")

Props to you for dealing with students whose parents may not have spent enough time " learnin' the youngins"

I get "students" like this all of the time, especially on AZB.

Thanks,
Dave

 

[Jaden]

Can you link to. ..

This is exactly what I am attempting to illustrate in the modified diagram. A portion of the end of the shaft does flex out as your describe (as the tip bends to point closer to CB center), but the overall motion and flex of the shaft is away from the CB as shown in the diagram. It is not the change in tip direction that causes squirt ... it is the overall motion and flex of the entire end of the shaft away from the CB (which is forced by the rotation the CB picks up very quickly during impact). For more info, see: what causes squirt.

Regards,
Dave

Can you link to high speed video showing what you're illustrating here?

The only high speed video of yours I've seen shows only the impact zone close up, not the shaft bending in the direction you claim during impact past the end mass point.

It seems that it's only after impact that the shaft flexes away from the direction of the squirt. Which would be the reaction to the forces building up during contact in the opposite direction.

The tip and shaft both appear to flex in the direction of the squirt DURING impact.

If you have video showing the shaft past the end mass point during impact flexing that way please link to it. I would be most appreciative.

Jaden

 

[Jaden]

The answer to your question is that it does.

Good Morning E,

If the right side of the shaft is met with the resistance of the cue ball, why would the shaft not have a slight brief bend with the tip more to the right as the shaft bows left...

Then as the ball rotates the front end & tip restore themselves & the tip & front end 'waffle' to the left with the bow to the right as the ball leaves to the right?

The above is what I see in my minds eye.

If we were to take a small diameter wooden dowel & angle it on a concrete floor & then load it with a force from the upper end, would the dowel not bow in the upward direction vs bowing downward?

If I'm missing something, what is it?

Best 2 Ya & Stay Well,
Rick

DURING impact it does flex in the direction of the load. It has to. The mass of the ball is preventing it from being as obvious as the reaction that goes in the opposite direction once friction between the ball and tip begins to end and the tip starts to slip.

Jaden

The late Royce Bunnell and I discussed this concept at length.

 

[dr_dave]

A portion of the end of the shaft does flex out as your describe (as the tip bends to point closer to CB center), but the overall motion and flex of the shaft is away from the CB as shown in the diagram. It is not the change in tip direction that causes squirt ... it is the overall motion and flex of the entire end of the shaft away from the CB (which is forced by the rotation the CB picks up very quickly during impact). For more info, see: what causes squirt.

Can you link to high speed video showing what you're illustrating here?

First, be aware that the the amounts of flex and bend shown in the diagram are exaggerated significantly for clarity.

I don't have a perfect video showing these effects because it would require a very good camera (much, much faster than the one I have) with a large-enough view and good-enough resolution to see everything clearly.

However, I think the following videos do a decent job illustrating the effects (albeit, not perfectly):

HSV A.25 - Cue deflection and vibration due to firm stroke with english
HSV B.9 - Cue deflection and vibration
HSV A.76a - close-up of tip during off-center hit
Russian video

FYI, more related videos can be found via the links on the cue vibration resource page.

It seems that it's only after impact that the shaft flexes away from the direction of the squirt.

You are correct that the shaft does flex and vibrate a lot after the tip separates from the CB (as is clear in the videos above), but this is due to the sideways speed developed during tip contact. The amount of flex away from the ball does grow larger after tip separation, but it begins during tip contact.

Regardless, it has been convincingly proven that shaft flex is not the most important effect concerning squirt. The most important effect is the sideways speed and momentum delivered to the shaft endmass during tip contact. This momentum is what causes the cue to continue to flex away from the CB and vibrate after tip release. For more explanations, illustrations, demonstrations, and proof, see all of the resources (articles, videos, analyses, explanations) on the following pages:

what causes squirt
and
squirt endmass and stiffness effects

Regards,
Dave

 

[dr_dave]

... once friction between the ball and tip begins to end and the tip starts to slip.

FYI, the tip doesn't ever really slip on the CB. It just releases as the force acting in the CB forward direction dissipate. If the tip slipped at all during contact, the shot would react like miscue or "partial miscue," and the amount of squirt (CB deflection) would likely be larger than expected.

Regards,
Dave

 

[Jaden]

No it hasn't.

First, be aware that the the amounts of flex and bend shown in the diagram are exaggerated significantly for clarity.

I don't have a perfect video showing these effects because it would require a very good camera (much, much faster than the one I have) with a large-enough view and good-enough resolution to see everything clearly.

However, I think the following videos do a decent job illustrating the effects (albeit, not perfectly):

HSV A.25 - Cue deflection and vibration due to firm stroke with english
HSV B.9 - Cue deflection and vibration
HSV A.76a - close-up of tip during off-center hit
Russian video

FYI, more related videos can be found via the links on the cue vibration resource page.


You are correct that the shaft does flex and vibrate a lot after the tip separates from the CB (as is clear in the videos above), but this is due to the sideways speed developed during tip contact. The amount of flex away from the ball does grow larger after tip separation, but it begins during tip contact.

Regardless, it has been convincingly proven that shaft flex is not the most important effect concerning squirt. The most important effect is the sideways speed and momentum delivered to the shaft endmass during tip contact. This momentum is what causes the cue to continue to flex away from the CB and vibrate after tip release. For more explanations, illustrations, demonstrations, and proof, see all of the resources (articles, videos, analyses, explanations) on the following pages:

what causes squirt
and
squirt endmass and stiffness effects

Regards,
Dave

The primary force moves the ball forward, it does not create the spin. The spin cannot have enough force to make the shaft move away until after the primary force has been exerted. It's possible that there is enough left to be pushing the ball slightly sideways but it is more likely until given more reason than people saying so that the simpler explanation that the tip and shaft are pointing in the direction the ball travels during the primary force transfer is the cause of squirt.

I would love to see what the level of correlation is between direction the ball travels and the direction the shaft and tip deformity is pointing during primary force transfer when the ball starts to move away from the cue.

Jaden

I think this is the reason for the disparity between your hard hit only tests of my tip and my more moderate speed tests.

When only striking hard you're going to force even the hardest of tips to deform in that direction or the shaft to deform enough to make the difference.

And again I didn't design my tips to be low deflection. During testing I discovered then to show lower squirt characteristics since I use bhe and the pivot point had noticeably changed.

 

[ENGLISH!]

DURING impact it does flex in the direction of the load. It has to. The mass of the ball is preventing it from being as obvious as the reaction that goes in the opposite direction once friction between the ball and tip begins to end and the tip starts to slip.

Jaden

The late Royce Bunnell and I discussed this concept at length.

Hi Jaden,

That's how I see it, in my minds eye & have been 'feeling' it that way for decades.

I don't think some 'feel' the cue ball on the cue stick. Perhaps that is from not hitting off center enough to garner that type of 'feel' or perhaps due to using hard tips. I don't know...

but it just seems that many consider it just a hit.

I guess it could be like one that hits the tennis ball flat or with unintentional spin from a fault in their stroke or bad timing.

When one intentionally hits the tennis ball with top & bottom spin one can start to 'feel' the ball on the strings & then begin to control the ball instead of just hitting it & 'trampolining' it back over or into the net.

A top spin back hand was the most difficult for me to get & I did not get it until I started 'sitting down' by flexing my knees & 'springing' into, through, & over it, the ball.

Anyway, I guess I was just looking for some 'verbal' confirmation from another.

Thanks for your post & Best 2 Ya,
Rick

 

[dr_dave]

The primary force moves the ball forward

Correct.

it does not create the spin.

Incorrect. The line of action of the primary force that pushes the CB forward acts off center (with an off-center hit). The resulting moment or torque is what creates CB spin.

The spin cannot have enough force to make the shaft move away until after the primary force has been exerted.

Incorrect. The primary force is very large during the brief contact time (peaking somewhere in the middle of the contact time). This force creates both CB forward motion and CB spin during contact. The spin is what pushes away and imparts sideways speed to the endmass.

Think about it. It the CB didn't develop both forward speed and spin during tip contact, how and when would they develop?

Please check out all of the explanations, illustrations, videos, and articles available via the links on the resource pages. I think they might help improve your understanding of the physics involved with squirt (CB deflection). I'm not writing this to be condescending. I honestly think the resources will help. Here they are again:

what causes squirt

squirt endmass and stiffness effects

Regards,
Dave

 

[Jaden]

Yes I know this

FYI, the tip doesn't ever really slip on the CB. It just releases as the force acting in the CB forward direction dissipate. If the tip slipped at all during contact, the shot would react like miscue or "partial miscue," and the amount of squirt (CB deflection) would likely be larger than expected.

Regards,
Dave

I know.

I'm typing all this from my phone and it was easier to say slip than lose grip or move away from the ball.

My batteries are dying on my phone and I'm in the ER so it may be a while before I come back on.

Jaden

 

[Jaden]

I'm limited in how much I can type from my phone.

Correct.

Incorrect. The line of action of the primary force that pushes the CB forward acts off center (with an off-center hit). The resulting moment or torque is what creates CB spin.

Incorrect. The primary force is very large during the brief contact time (peaking somewhere in the middle of the contact time). This force creates both CB forward motion and CB spin during contact. The spin is what pushes away and imparts sideways speed to the endmass.

Think about it. It the CB didn't develop both forward speed and spin during tip contact, how and when would they develop?

Please check out all of the explanations, illustrations, videos, and articles available via the links on the resource pages. I think they might help improve your understanding of the physics involved with squirt (CB deflection). I'm not writing this to be condescending. I honestly think the resources will help. Here they are again:

what causes squirt

squirt endmass and stiffness effects

Regards,
Dave

Obviously I didn't communicate what I was saying in depth enough.

The primary motion on the ball is forward. So the majority of the force is creating the forward motion on the ball the shaft doesn't start to move away from the initial direction until at least after the midway point where the majority of the force has already been imparted. It can't because the mass of the ball is preventing the shaft from flexing outward and is creating the force in the shaft that causes it to flex outward.

I suggest that the spin is being created due to the continued friction between the tip and the ball after the mass of the ball has started to move away releasing the built up tension in the shaft and allowing it to react to the force that built up in the shaft towards the side of the shaft that the force was exerted on.

It is the reaction to that built up force that causes the shaft to move opposite the center of mass of the ball and the continued friction that imparts spin on the ball.

Jaden

 

[dr_dave]

The primary motion on the ball is forward. So the majority of the force is creating the forward motion on the ball the shaft doesn't start to move away from the initial direction until at least after the midway point where the majority of the force has already been imparted. It can't because the mass of the ball is preventing the shaft from flexing outward and is creating the force in the shaft that causes it to flex outward.

I suggest that the spin is being created due to the continued friction between the tip and the ball after the mass of the ball has started to move away releasing the built up tension in the shaft and allowing it to react to the force that built up in the shaft towards the side of the shaft that the force was exerted on.

It is the reaction to that built up force that causes the shaft to move opposite the center of mass of the ball and the continued friction that imparts spin on the ball.

This is a good explanation of a "proposed theory" for what might cause squirt, but it seems at odds with collision physics and the generally-accepted squirt theory which has withstood the test of time and is well-supported with many analyses, demonstrations, and experimental results.

I think one thing that might be causing confusion is this:

The flex of the tip and the flex of the end of the shaft toward CB center are results of the primary forward force imparted to the ball, they are not the causes of the primary force (nor are they the causes for the spin). Also, the grabbing force of the tip is not separate from the primary force ... it is necessary to help create the primary force pushing the CB forward. I hope that make sense.

When you get some time, try to carefully look through the previously-linked resources and try to see the perspective they present (which backs up the currently understood and well-tested theory for what causes squirt).

Regards,
Dave

 

[Jal]

The primary motion on the ball is forward.

Not necessarily. When struck at 2/5'ths of its radius off-center, its surface speed from spin is equal to its forward speed. At 1/2 radius (the miscue limit), its surface speed can be slightly greater than its forward speed.

So the majority of the force is creating the forward motion on the ball the shaft doesn't start to move away from the initial direction until at least after the midway point where the majority of the force has already been imparted.

Anytime it's struck off-center, spin is created simultaneously with forward motion. This happens from the very first moment the tip comes into contact with the cueball. Every ounce of forward force generates not only translational velocity, but a concomitant amount of spin, depending on the tip offset. Spin is not a delayed reaction. Jaden, this is very, very basic physics.

Take these words by Dr. Dave to heart, if you would:

"Also, the grabbing force of the tip is not separate from the primary force ... it is necessary to help create the primary force pushing the CB forward."

Jim