AzBilliards.com Physics-Minded..How does the CB know?
 Page 1 of 5 1 23 > Last »
 Physics-Minded..How does the CB know?
 (#1) CueAndMe AzB Silver Member   Status: Offline Posts: 1,771 vCash: 500 iTrader: 0 / 0% Join Date: Feb 2008 Location: NJ Physics-Minded..How does the CB know? - 03-11-2008, 12:20 PM I see it's been generally agreed upon that the mass in the first few inches of a shaft determines the amount of squirt. I can sort of grasp that, but I don't understand the effects of overall cue weight and weight distribution. 1)Say you're the cue ball. You're struck at the same speed and contact point by the same modern low-squirt shaft placed on two different butts. The first contact is from a 17 oz. total weight cue. The second contact is from a 25 oz. total weight cue. How do you know to react differently? 2)Same scenario, but the 17 oz. cue is being held with a death grip, and the 25 oz. cue is being held with a feather touch that allows the cue to be thrown into the cueball. Still both cues contacting the cueball at the same speed. How does this change things? Does the arm's mass with the 17 oz. shot come into play, in essence, fusing with the cue's mass? 3)How about 2 cues with the same shaft and overall weight but the first has most of its weight forward, the second has most of its weight rearward? 4)How about 2 cues with the same shaft and overall weight but the first has most of its weight around the perimeter, the second has most of its weight in its core? What answers above would change depending on stick speed or CB contact point? Thanks, Jeff

 (#2) worriedbeef The Voice of Reason     Status: Offline Posts: 1,832 vCash: 1300 iTrader: 0 / 0% Join Date: Mar 2006 Location: Birmingham, England 03-11-2008, 12:28 PM well let's change the way you're thinking about it. imagine you're the CUE, not the cue ball. because it's the cue that reacts to hitting a solid object not the other way round. so when a cue with minimal end mass hits the edge of a cue ball it bends and deflects away, resulting in less squirt on the cue ball. as for the weight distribution, it's not a key factor in squirt i don't think. it's stiffness. for example, if you had a cue with very low end mass towards the tip and it was hollow, but it was made out of steel, it would still squirt the cue ball off and not deflect. "I know someday you'll have a beautiful life I know you'll be a sun, in somebody else's sky but why, why, why can't it be mine?"
(#3)
Patrick Johnson
Fish of the Day

Status: Offline
Posts: 21,449
vCash: 1700
Join Date: Jun 2007

03-11-2008, 12:38 PM

Quote:
 ...as for the weight distribution, it's not a key factor in squirt i don't think. it's stiffness.
I think it's the other way around.

pj
chgo

 (#4) Franky woman I said NO!!!     Status: Offline Posts: 422 vCash: 500 iTrader: 0 / 0% Join Date: Mar 2007 Location: California 03-11-2008, 12:40 PM Remember that the contact between the cuetip and the cueball is not instantaneous. Keeping this in mind, understand that during that contact, both the cueball and the front of the cue are acting as a unit...although one that is undergoing acceleration. The heavier the front of the cue, the more it will push the cueball to the side away from the side of the English applied during this contact because the front of the cue has a higher percentage of the mass of the "system" (cueball and front of the cuestick) than the same system would have had had a low-deflection shaft been used. A lot of the energy that would go into deflecting the cueball with a traditional shaft instead goes into bending the front of the cue around the mass of the cueball in a lower deflection shaft. This is why most of these spliced shafts have vibration dampening material in them...because the shaft is going to flex more on contact, and that flex is going to straighten out after contact and wiggle a bit 'till it calms down. Hope this makes some sense. Casually, I switched tactics.
(#5)
worriedbeef
The Voice of Reason

Status: Offline
Posts: 1,832
vCash: 1300
Join Date: Mar 2006
Location: Birmingham, England

03-11-2008, 12:40 PM

Quote:
 Originally Posted by Patrick Johnson I think it's the other way around. pj chgo
can you please explain? i think i have a pretty good understanding about squirt and deflection, and doesn't my example about the steel cue prove my point?

"I know someday you'll have a beautiful life I know you'll be a sun, in somebody else's sky but why, why, why can't it be mine?"

(#6)
jongreve
AzB Silver Member

Status: Offline
Posts: 187
vCash: 500
Join Date: Feb 2008
Location: Chanute, KS

03-11-2008, 01:21 PM

Quote:
 Originally Posted by bluepepper I see it's been generally agreed upon that the mass in the first few inches of a shaft determines the amount of squirt. I can sort of grasp that, but I don't understand the effects of overall cue weight and weight distribution. 1)Say you're the cue ball. You're struck at the same speed and contact point by the same modern low-squirt shaft placed on two different butts. The first contact is from a 17 oz. total weight cue. The second contact is from a 25 oz. total weight cue. How do you know to react differently? 2)Same scenario, but the 17 oz. cue is being held with a death grip, and the 25 oz. cue is being held with a feather touch that allows the cue to be thrown into the cueball. Still both cues contacting the cueball at the same speed. How does this change things? Does the arm's mass with the 17 oz. shot come into play, in essence, fusing with the cue's mass? 3)How about 2 cues with the same shaft and overall weight but the first has most of its weight forward, the second has most of its weight rearward? 4)How about 2 cues with the same shaft and overall weight but the first has most of its weight around the perimeter, the second has most of its weight in its core? What answers above would change depending on stick speed or CB contact point? Thanks, Jeff

I would think that....

a higher momentum and/or force would more elongate the forward vector
(direction of travel)

momentum = mass x velocity
force = mass x acceleration
(it is near impossible NOT to have acceleration)

I also would think that....

a longer time of contact would more elongate the "squirt" vector

These statements assume identical deflection characteristics of the cues

Not exactly what you are looking for, but this is more complicated than it looks.

(#7)
Cornerman
Cue Author...Sometimes

Status: Offline
Posts: 12,264
vCash: 1700
Join Date: Oct 2005
Location: Clearwater, FL

03-11-2008, 01:32 PM

Quote:
 Originally Posted by bluepepper I see it's been generally agreed upon that the mass in the first few inches of a shaft determines the amount of squirt. I can sort of grasp that, but I don't understand the effects of overall cue weight and weight distribution. 1)Say you're the cue ball. You're struck at the same speed and contact point by the same modern low-squirt shaft placed on two different butts. The first contact is from a 17 oz. total weight cue. The second contact is from a 25 oz. total weight cue. How do you know to react differently? 2)Same scenario, but the 17 oz. cue is being held with a death grip, and the 25 oz. cue is being held with a feather touch that allows the cue to be thrown into the cueball. Still both cues contacting the cueball at the same speed. How does this change things? Does the arm's mass with the 17 oz. shot come into play, in essence, fusing with the cue's mass?
These are good questions that I believe have been answered before, but not as much as other squirt questions.

I believe the answer lies in the same question as "how much is 'the first few inches' and why?" The theory that makes the most sense is that the number of inches down the shaft is based on the lateral wave sent down and its speed. The normal axial shockwave is based on the speed of sound through the material, which is very fast. But the lateral wave is very slow. Predicted about 3 inches per millisecond. So, if the contact time is 2 milliseconds for the extreme english shots, then the cueball only "sees" about 6 inches worth of shaft. Therefore, theoretically, if this is correct then it won't matter what weight is behind those first several inches.

The unobtainable death grip (obtainable with a robot, but probably not with a human hand) would only affect things by increasing the contact time. Which it will. Lateral wave times the contact time equals more stick mass. The Jacksonville Project showed this. When they went to bubble wrap on the grip, it mimicked a human hand with its pliable flesh. Without the bubble wrap, the robot gave an unnatural amount of contact time, and really did "stroke through the cueball." Bob Jewett would have more information on that.

The other noteworthy area is if the bridge hand wasn't fleshy. Let's say, a solid V-block. If during tip contact, the lateral wave got to this solid block during tip/ball contact, then the cueball would again "see" more weight. I believe this is the problem with Bob Meucci's MythBuster set up, as far as testing Predator shafts is concerned.

None of these are set in stone, but I like the theories.

Fred

--------

Name: Freddie Agnir
Shooting Cue: 2017 Tascarella (w/blokid extension) or Schuler SC-250
Breaking Cue: BK Rush

Playing time: just a hair above zero
--------

"I don't care if you win, just cover the spread!"

- Annie Potts (Memaw from Young Sheldon)

(#8)
Bigjohn
Support Our Troops!

Status: Offline
Posts: 7,266
vCash: 3600
Join Date: Jul 2005
Location: Lonestar State

03-11-2008, 02:22 PM

Quote:
 Originally Posted by bluepepper I see it's been generally agreed upon that the mass in the first few inches of a shaft determines the amount of squirt. I can sort of grasp that, but I don't understand the effects of overall cue weight and weight distribution. 1)Say you're the cue ball. You're struck at the same speed and contact point by the same modern low-squirt shaft placed on two different butts. The first contact is from a 17 oz. total weight cue. The second contact is from a 25 oz. total weight cue. How do you know to react differently? 2)Same scenario, but the 17 oz. cue is being held with a death grip, and the 25 oz. cue is being held with a feather touch that allows the cue to be thrown into the cueball. Still both cues contacting the cueball at the same speed. How does this change things? Does the arm's mass with the 17 oz. shot come into play, in essence, fusing with the cue's mass? 3)How about 2 cues with the same shaft and overall weight but the first has most of its weight forward, the second has most of its weight rearward? 4)How about 2 cues with the same shaft and overall weight but the first has most of its weight around the perimeter, the second has most of its weight in its core? What answers above would change depending on stick speed or CB contact point? Thanks, Jeff
Who Cares?

(#9)
CueAndMe
AzB Silver Member

Status: Offline
Posts: 1,771
vCash: 500
Join Date: Feb 2008
Location: NJ

03-11-2008, 03:32 PM

Quote:
 Originally Posted by Bigjohn Who Cares?
It may seem like these questions are trivial, but after finding out that squirt is affected solely by a few inches at the end of the stick, I'm wondering if this area of the shaft is actually the ONLY thing important to how a cueball reacts, not just squirt-wise, but for all shots.

I understand the importance of choosing and customizing a cue for feel. But focusing solely on cueball response to a particular contact point at a particular speed with a particular shaft, does the rest of the cue matter?

Maybe it matters more on center ball hits than spin shots. Maybe it matters more with stiffer shafts than flexible ones. Maybe it matters more with high-squirt shafts than low-squirt shafts. I don't know. I'm curious.

Jeff

 (#10) CueAndMe AzB Silver Member   Status: Offline Posts: 1,771 vCash: 500 iTrader: 0 / 0% Join Date: Feb 2008 Location: NJ 03-11-2008, 03:35 PM Still trying to take in everyone's posts here, and will later pick your brains some more with a reply. To clarify, it may have seemed that I was asking only about squirt, but I was actually interested in all shots. Thanks for the replies. Jeff
(#11)
Patrick Johnson
Fish of the Day

Status: Offline
Posts: 21,449
vCash: 1700
Join Date: Jun 2007

03-11-2008, 04:04 PM

Quote:
 worriedbeef: ...as for the weight distribution, it's not a key factor in squirt i don't think. it's stiffness. Me: I think it's the other way around. worriedbeef: can you please explain?
Many shafts, flexible and stiff, have been tested for squirt, and flexibility or stiffness has not been shown to be much of a factor compared with "end mass" (weight near the tip). When a stiff low-tip-mass cue is compared with a flexible high-tip-mass cue, the stiff one produces less squirt. Stiffness doesn't seem to matter much, if at all.

Quote:
 ...doesn't my example about the steel cue prove my point?
It's not really an example unless you actually try it. It's not obvious from your "thought experiment" what would happen.

pj
chgo

(#12)
JoeyInCali
AzB Silver Member

Status: Offline
Posts: 24,487
vCash: 4400
Join Date: Jul 2004
Location: OC, California

03-11-2008, 04:13 PM

Quote:
 Originally Posted by Patrick Johnson Many shafts, flexible and stiff, have been tested for squirt, and flexibility or stiffness has not been shown to be much of a factor compared with "end mass" (weight near the tip). When a stiff low-tip-mass cue is compared with a flexible high-tip-mass cue, the stiff one produces less squirt. Stiffness doesn't seem to matter much, if at all. It's not really an example unless you actually try it. It's not obvious from your "thought experiment" what would happen. pj chgo
So does that mean if a 13MM tip shaft is retapered down to 12 MM with a longer taper, it will have less cueball squirt?

(#13)
worriedbeef
The Voice of Reason

Status: Offline
Posts: 1,832
vCash: 1300
Join Date: Mar 2006
Location: Birmingham, England

03-11-2008, 04:17 PM

Quote:
 Originally Posted by Patrick Johnson Many shafts, flexible and stiff, have been tested for squirt, and flexibility or stiffness has not been shown to be much of a factor compared with "end mass" (weight near the tip). When a stiff low-tip-mass cue is compared with a flexible high-tip-mass cue, the stiff one produces less squirt. Stiffness doesn't seem to matter much, if at all. It's not really an example unless you actually try it. It's not obvious from your "thought experiment" what would happen. pj chgo
true i realise i havent really done a practical experiment but i cannot comprehend what i'm saying not being the case. oh well, i'll have to think about it some more. unfortunately i don't have a hollow stainless steel cue lol

"I know someday you'll have a beautiful life I know you'll be a sun, in somebody else's sky but why, why, why can't it be mine?"

(#14)
Bob Jewett
AZB Osmium Member

Status: Offline
Posts: 17,981
vCash: 1700
Join Date: Apr 2004
Location: Berkeley, CA

03-11-2008, 04:22 PM

Quote:
 Originally Posted by bluepepper I see it's been generally agreed upon that the mass in the first few inches of a shaft determines the amount of squirt. I can sort of grasp that, but I don't understand the effects of overall cue weight and weight distribution. 1)Say you're the cue ball. You're struck at the same speed and contact point by the same modern low-squirt shaft placed on two different butts. The first contact is from a 17 oz. total weight cue. The second contact is from a 25 oz. total weight cue. How do you know to react differently? 2)Same scenario, but the 17 oz. cue is being held with a death grip, and the 25 oz. cue is being held with a feather touch that allows the cue to be thrown into the cueball. Still both cues contacting the cueball at the same speed. How does this change things? Does the arm's mass with the 17 oz. shot come into play, in essence, fusing with the cue's mass? 3)How about 2 cues with the same shaft and overall weight but the first has most of its weight forward, the second has most of its weight rearward? 4)How about 2 cues with the same shaft and overall weight but the first has most of its weight around the perimeter, the second has most of its weight in its core? What answers above would change depending on stick speed or CB contact point? Thanks, Jeff
The stick transfers energy to the cue ball by compressing like a spring along its whole length. The compression wave happens at the speed of sound in the stick, which is about 13000 feet per second. This speed is the fastest that the butt can learn of something colliding with the tip. Some people make the mistake of thinking of the cue stick as being perfectly rigid and incompressible, but it's not. So, the shot proceeds like this: the stick is coming forward and the tip meets the ball. The tip starts to compress, force and acceleration of the cue ball start to build up. The ball also starts to compress, since it too is not incompressible. The ball has started to move, but is not up to the speed of the stick yet, and the stick has started to slow down as its energy is transferred to the cue ball. This continues until the tip (and ferrule and joint and butt) reach maximum compression along the length. At this exact point some amazing things are happening. The stick and ball are moving at the same speed. The force between stick and ball are at their maximum. The compression along the length of the stick (including the tip) is at its maximum. The energy stored in the spring-like compression of the tip (and stick and ball) are at their maximum. For a typical ball and stick, the speeds of the ball and stick are 75% of the original stick speed.

After this point of maximum compression, the ball is pushed forward from the tip by the compression of system. The ball starts to move even faster from this force and the stick continues to slow down. This "unwinding" process continues until the ball finally leaves the tip. At that point, the ball is going at about 130% of the original stick speed, and the stick has slowed down to about 50% of its original speed. (The 130% would be 150%, but the tip is not perfect in springing back to its original shape, and energy is lost.)

Now the hand comes in. Human flesh makes a much "softer" spring than the leather of a tip or the wood that is compressed along the length of the stick. Think of the tip as about the stiffest car spring you can imagine and your hand like a rubber band. The cue ball is gone by the time your hand -- which is still moving forward at full speed -- can wind up even a little. As the hand winds up on the stick and relaxes, which takes about 20 milliseconds, the hand is slowed to about 80% of its initial speed and the stick goes from 50% back up to 80% of its initial speed. Of course this re-acceleration of the stick by your hand is useless in that the cue ball is long gone.

How does a heavier stick affect things? It changes that 130% number. The formula is in Byrne's Advanced book, and somewhere in my columns in Billiards Digest and certainly in Ron Shepard's paper and Dr. Dave's book. A heavier stick through the spring action, puts slightly more energy into the cue ball.

As for how the weight of the stick affects the squirt, I think the answer is that it doesn't, much. Squirt is caused by the spinning cue ball pushing the stick to the side during the contact time of an off-center hit. The amount of squirt is determined by the mass that is being pushed to the side. Since the stick is very floppy side-to-side (as compared to length-wise compression), only the front part of the stick can participate in the squirt during the 1 millisecond or so of contact time. A heavier stick will increase the contact time a little, and that will increase the squirt a little, but I think this effect is pretty small.

Phrased technically, the transverse wave has a very slow propagation velocity along the length of the stick, and so the joint and butt cannot participate in the sideways push that causes squirt.

You should find Mike Page's discussion of his experiment with vise grips on the shaft which determined how much of the shaft participates in squirt.

As Fred mentioned, a major problem with some of the Jacksonville Project was that Iron Willie had too stiff a grip -- like vise grips -- and too hard a bridge. I have heard that Predator's current cue testing robot has fixed those problems to hold the cue more like a human at both ends.

As for some of your other questions, in theory the squirt should depend on stiffness of the cue since that should change the speed of the transverse wave. In practice, "end mass" seems to be a much better indicator of squirt than stiffness. There are stiff cues with little squirt and stiff cues with lots of squirt. A major red herring along the path of squirt studies was the fact that carom cues tend to be stiff but have relatively low squirt. They usually have smaller tips than pool cues.

Bob Jewett

Last edited by Bob Jewett; 03-11-2008 at 04:27 PM.

(#15)
JoeyInCali
AzB Silver Member

Status: Offline
Posts: 24,487
vCash: 4400
Join Date: Jul 2004
Location: OC, California

03-11-2008, 04:26 PM

Quote:
 Originally Posted by worriedbeef true i realise i havent really done a practical experiment but i cannot comprehend what i'm saying not being the case. oh well, i'll have to think about it some more. unfortunately i don't have a hollow stainless steel cue lol
The low end mass works on wooden shafts b/c they are flexible enough that the front-end would deflect OFF the cueball before the cueball deflects off the tip.
A low end mass on steel shafts wouldn't be much of help because it will not bend away from the ball.

 Page 1 of 5 1 23 > Last »

 Thread Tools Rate This Thread Rate This Thread: 5 : Excellent 4 : Good 3 : Average 2 : Bad 1 : Terrible

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is Off Forum Rules
 Forum Jump User Control Panel Private Messages Subscriptions Who's Online Search Forums Forums Home Main Category     Main Forum     Live Stream Area     Wanted/For Sale         For Sale Items         eBay Auctions         Wanted     Room Owner Discussion     14.1 Pool     Canadian Pool     Snooker     Carom Billiards     Memories of Steve Mizerak     English Pool     Billiard and Pool History in the U.S.     BEF Juniors Pool     Test Area     Cuesports: Rules & Strategies     AzB Hall of Fame     Pool Room Reviews Tournament Talk     U.S. Tournament Announcements     European Tournament Annoucements     Asian Tournament Announcements     Super Billiards Expo     Junior National 9-Ball Championships     World Championships     US Open Championships     Derby City Classic/Southern Classic     BCA Pool League World Championships     US Bar Table Championship     WPBA     Matchroom Events     Eurotour     Other Tours & Events Products Talk     Pool Tables and Accessories Reviews     Cue Reviews     Cue and shaft reviews     Cue Case Reviews     Cue Machinery and Supplies     Cue & Case Gallery     Ask The Cuemaker     Cue Accessory reviews     Other Item reviews     Talk To A Mechanic Instruction & Ask the pros     Aiming Conversation     George 'Ginky' San Souci     Instructional Material reviews     Instructor Reviews     Melissa Morris     Sarah Rousey     Ask The Instructor