The Deflection Battle Heats Up!

[Colin Colenso]

Colenso Deflection Theory Part 2

Colenso Theory of Deflection: Part 2 Grip and Deflection

In part one of this series we learned about the current understanding of cue ball deflection and were introduced to a criticism of this generally accepted theory. In part 2 I will talk about the role that grip plays in deflection.

A diagram was presented at the end of part 1, to show that off center contact with the cue ball will produce no deflection if that contact has complete grip or a perfectly parallel transference of momentum. But as we do experience deflection on off center hits in the real world, I propose that in fact, we should not accept the idea that there is perfect grip, or no slip at the contact point. In fact, these terms are inappropriate to use to describe what is going on during a collision.

In reality, millions of minor elastic collisions are occurring at the surface interface. The attached diagram illustrates this idea.


By looking at the Tip to Cue Ball collision this way, it becomes obvious, that the main determinants of deflection are the surface characteristics of the two objects. Evidence of this is easily observed in the following situations:

1. Balls colliding deflect at almost 90 degrees.
2. Tips without chalk deflect at high angles. (Without obvious feeling of a miscue).
3. Poor quality chalks or tips deflect more.
4. Quality tips well chalked deflect less.

This evidence is observational, and hasn’t been tested in detail, but to most players they will seem quite obvious.

So why do tests show that tip endmass and distance from center are the key factors in determining cue ball deflection? The answer to this is quite simple. During testing, the tip and chalk qualities are kept almost constant.

With these new insights of the Colenso Theory of Deflection, a whole new horizon of experimental design becomes possible. This theory puts into perspective the most significant developments of cue technology in history. These were the invention of the leather tip by Francois Mingaud and the invention of what was then called twisting chalk by John Carr in the early 1800’s. Both of these developments reduced deflection of off center shots by large amounts as well as increasing the capacity to put spin on the cue ball.

We are now forced to re-examine the 2 factors that have been presumed as the only determinants of cue ball deflection.

Off Center Hit Deflection Factor: Obviously, the further off center we strike the cue ball, the greater will be the amount of minor collisions in a direction away from the line of the cue.

Tip Endmass Deflection Factor: This is harder to ascertain with any precision or certainty, but I will propose the following reason. While many of the contact points are supported along a line of connected molecules running up the length of the cue, a percentage of these contact points apply force across the line of the cue. The resultant forces for these contact points will be increased by a higher weight endmass. This theory suggests that the key in reducing tip endmass deflection will be to reduce the density at the very near end of the cue. Primarily at the tip and the end of the ferrule. Beyond one inch from the cue tip, additional weight will have a negligible effect.

With these new insights, we must consider a new range of factors that influence cue ball deflection. These include, but are not limited to chalk, tip, ferrule, ball and shaft properties. Part 3 in this series will investigate these factors and the influence they could have on future cue designs.
End of Part 2

 

[Colin Colenso]

Colenso Deflection Theory Part 3

Colenso Theory of Deflection: Part 3 Why the Colenso Theory of Deflection Matters?

In parts 1 and 2 of this series we learned about the prominent theory of cue ball deflection today and the new Colenso Theory of Cue Deflection. In this part of the series I will show how my own theory creates an entirely new landscape on thinking about how cues work and hence a new approach to the development of future cue design.

To illuminate this development, the following points will contrast the current popular beliefs as summarized by Ron Shepard in his physics paper on squirt (cue ball deflection) see: http://www.sfbilliards.com/Shepard_squirt.pdf and compare them to some conclusions that can be drawn by my own new theory.

Questions are followed by Ron Shepard’s answers and then my own:

How can squirt be minimized?
RS: By reducing the tip offset or by using a cue stick with a small endmass.

Colin: By various other methods in addition to these 2 factors. These additional factors include chalk, tip, ferrule, ball and shaft characteristics that are independent of cue endmass as well as cue speed.

Does shaft flexibility affect squirt?
RS: No, not directly. Shaft flexibility may affect the endmass and thereby affect squirt indirectly, but this is probably a relatively minor effect.

Colin: Yes, in at least three possible ways. Firstly, a flexible shaft could reduce the ability of the full weight of the cue to produce force along the line of the cue, meaning a stiff shaft could reduce deflection. Secondly, a flexible shaft could reduce tip endmass. Thirdly, flexibility could affect the way chalk interacts with the collision interface and affect the transference of forces.

Does tip curvature affect squirt?
RS: No, not according to the above analysis, except for the fact that the tip curvature affects the actual tip offset for a given shaft offset. However, there are data at the Predator web site that suggests that a rounder tip (i.e. a dime radius compared to the larger nickel radius) reduces squirt.

Colin: Yes, tip curvature is crucial to the collision interface and has a considerable effect on deflection. Not only does the Predator testing support this, but also any experienced player will attest to this.

Does squirt depend on shot speed?
RS: No, not directly. Shot speed might affect the endmass, but this is probably a relatively minor effect. The observation that different aiming is required for different shot speeds, particularly on longer shots, is probably due to cue ball swerve, not to squirt.

Colin: Yes, shot speed affects the shape of the tip, the degree of forces, the distribution of chalk and other aspects of the collision interface. Player experience indicates that increasing shot speed increases deflection.

Does squirt depend on the cue stick weight?
RS: Yes, but only when it affects the endmass. Weight added more than about 10 inches away from the tip apparently has little effect.

Colin: Yes, but not very much. A heavy butt on a stiff cue with low endmass may actually decrease deflection by increasing the forces at contact points in line with the cue. Testing a very short light cue can prove this hypothesis. In practice, I suspect, any benefits gained by a stiff cue with an extra dense butt are insignificant and would be counteracted by a loss of speed control.

Do ivory or brass ferrules have more squirt than synthetic materials?
RS: If so, it is primarily because of the density of the material and the resulting effect on the endmass. It appears unlikely that the hardness or other physical characteristics affect directly the squirt. However, a thick brass ferrule will probably have more squirt than a thin brass ferrule.

Colin: Yes, for the reason Ron mentions. But regarding hardness I disagree. Hardness, or other physical characteristics could effect the interaction at the collision interface. Ferrule material that may flex either along the line of the cue or perpendicular to it, or at other angles may have considerable effect on how the chalk interacts with the collision surface and how forces are distributed. I believe this will be an important area of research for cue development in the future.

Does tip hardness affect squirt?
RS: No, not according to the above analysis. This also suggests that the tip-ball contact time, which is related to tip hardness, does not directly affect squirt, but this has not been proven independently, and it is possible that contact time does play at least a minor role in determining the effective endmass.

Colin: Yes, because tip hardness is crucial to the collision interface. A thick soft tip can deform and then deflect the force back in the direction of the deformation, which will tend toward the center of the cue ball hence increasing deflection. It could also affect the way the chalk and surfaces interact. More testing is needed regarding tip hardness and thickness to determine how best to reduce deflection. I should mention that generally top-level players prefer harder tips and believe this reduces deflection.

Note: Some of Ron Shepard’s responses have been truncated for the sake of brevity and clarity. Refer to his full responses at the link provided above. I invite Ron to respond to this article.

In summary, here the evidence supporting my theory over Ron’s theory includes:

1. The effects of leather tips and chalk in reducing deflection.
2. Players experiencing greater deflection with increased cue speed.
3. Players preferring harder tips to decrease deflection.
4. Meucci Cue testing indicate stiffer shafts decrease deflection.
5. Predator testing and player experience showing tip diameter affects deflection.
6. That my theory considers the physics at the collision interface.

The Colenso Theory of Deflection is a new paradigm.
By contrasting the opinions above, it is readily apparent that my theory of cue ball deflection leads to a very different paradigm in understanding the causes of deflection and the possibilities of producing improved performance cues in the future. In the next article, I will discuss the how we may work toward finding ways to decrease deflection.
End of Part 3

Note: Further parts are still being completed and all of this series will appear on www.cuezine.com in coming weeks.

 

[drivermaker]

According to the paper "Everything You Always Wanted to Know About Cue Ball Squirt, But Were Afraid to Ask" by Ron Shepard...
( http://www.sfbilliards.com/Shepard_squirt.pdf )

Deflection will occur above or below the pivot point on a cue stick, but not *at* the pivot point! [Pivot point as discussed in the above paper.]

I have tried this and found that different cue sticks will have different pivot points at which *no* cue ball deflection will occur - This is discussed in the above paper. (My supply of different cue sticks and testing methods are of course limited.)

I have one stick with a 20" pivot point. Sure enough... Pivot for English at 10" or 30" and you get cue ball deflection. Pivot at 20" and *no* cue ball deflection! How did I find the pivot point? By using the test suggested in the above paper.

To get to my point/suggestion, I think cue sticks should *not* have little or zero deflection, rather the shaft should be "tuned" or weight adjusted so that the pivot point is exactly where you hold the butt of the cue stick. Then to aim, you would line up for a dead center aim, then move your bridge hand left/right for English and have no cue ball deflection.

So if the pivot point is further back than where you hold the butt of your cue, I think just the right amount of weight should be added to the tip so it moves the pivot point forward to where you hold the butt. Anyone thought of doing this?

Take one of your cues, actually multiple cues that have different amounts of squirt and test each of them. Place the CB directly on the head spot. You are going to try to shoot it directly over the foot spot as accurately as you can with english. However here's how you do it: Aim the exact vertical center at the top of the ball directly over the foot spot with your eyes alone while you're down in your normal position. Place the tip of the cue 1/2 of the way between the center of the CB and the edge of the ball to the right, all the while you're still lining up the CB only with the spot and your eyes, not your cue. Fact is your cue will be aiming off to the right somewhere, it doesn't matter, it should be to the right. Now, pivot your cue tip back to the exact center of the CB without moving your bridge hand and strike the CB at the foot spot. Does the CB now go directly over the spot without deflection, hit the end rail and spin off to the right? Do the same thing with the tip to the left and see what happens. Does it now go over the spot accurately and spin to the left from the end rail? Did anybody ever think of this?

 

[rocky]

Take one of your cues, actually multiple cues that have different amounts of squirt and test each of them. Place the CB directly on the head spot. You are going to try to shoot it directly over the foot spot as accurately as you can with english. However here's how you do it: Aim the exact vertical center at the top of the ball directly over the foot spot with your eyes alone while you're down in your normal position. Place the tip of the cue 1/2 of the way between the center of the CB and the edge of the ball to the right, all the while you're still lining up the CB only with the spot and your eyes, not your cue. Fact is your cue will be aiming off to the right somewhere, it doesn't matter, it should be to the right. Now, pivot your cue tip back to the exact center of the CB without moving your bridge hand and strike the CB at the foot spot. Does the CB now go directly over the spot without deflection, hit the end rail and spin off to the right? Do the same thing with the tip to the left and see what happens. Does it now go over the spot accurately and spin to the left from the end rail? Did anybody ever think of this?

That is back hand english and it is a guessing game. I will take my straight english with predictable results anyday. I used this demo on our table at the BCA's and even with back hand english our shaft still shot truer ( if that is a word if not I apoligise ) screwed onto the but that they were already using.

 

[Skeezicks]

Back when Mosconie made his high run, what kind of cue was he using? What kind of shaft?

He did it on an 8' table.

I gotta get a 8' table!

 

[Joseph Cues]

That is back hand english and it is a guessing game. I will take my straight english with predictable results anyday. I used this demo on our table at the BCA's and even with back hand english our shaft still shot truer ( if that is a word if not I apoligise ) screwed onto the but that they were already using.

How is that a guessing game, may I ask?
He's aiming like a center ball shot, and without moving his bridge hand, aims the tip for english, and shoots at medium speed.
With a low deflection shaft, wouldn't the throw be more than the squirt?
After all, the cb won't deflect so if the cb hits the contact point ( the true one, no allowance) and the cb is spinning, it will throw the ob.

 

[Skeezicks]

The old guys didn't have any of this stuff and played much better than the rest of us. What was their secret. How did they do it?

No secret. They didn't have lives. All they did was play pool.

 

[Skeezicks]

A nice looking cue is like a nice looking suit, it makes the wearer feel good about himself (herself?). Now, having sid that, a jerk in a good suit is still a jerk, and a ball banger with a $3000 custom cue is not going to play better, no matter how good he feels.

I, too, have given this some thought. Do clothes make the man or not?

 

[Skeezicks]

Read that paper and almost fell asleep in the middle of it.

Sometimes I do that while reading this forum.

 

[drivermaker]

How is that a guessing game, may I ask?
He's aiming like a center ball shot, and without moving his bridge hand, aims the tip for english, and shoots at medium speed.
With a low deflection shaft, wouldn't the throw be more than the squirt?
After all, the cb won't deflect so if the cb hits the contact point ( the true one, no allowance) and the cb is spinning, it will throw the ob.

DING-DING-DING-DING-DING-DING Joseph Cues just hit the jackpot on the one million dollar slot machine!!! Geezus Key RICED...are you and I the only ones that know how to shoot backhand english around here?? Even a Predator has SOME squirt when shooting with english...it is NOT down to zero on the squirt issue. I want someone to tell me how you get squirt on a center ball hit. C'mon...explain it. Plus, you're right...there is more throw taking effect. Here's the deal...everyone out there do the shooting drill as I've laid out. Fact is, take the tip of your cue to 3/4 of the way out to the edge and not 1/2 and then pivot back to center with your backhand and you WILL NOT get SQUIRT...simple as that. You'll be going DEAD CENTER of the spot EVERY time and still getting your english. I don't give a damn how hard you hit the CB. That's why the pro's use it and are deadly.

 

[Bluewolf]

Ok Laura, here is my own theory, and I believe it is much easier to understand that Ron's analysis.
-------------------------------------------

1. Lighter tip, ferrule and shaft may reduce endmass.
2. Thinner cue end.
3. A more flexible shaft may reduce endmass.
4. A lighter cue may reduce endmass.
5. A looser grip may reduce endmass.

Points 1 and 2 are generally accepted, point 3 is often accepted, while the effects of points 4 and 5 are considered by most to be negligible.

An Erroneous Assumption about Slip

In part 2 of this series, I will expand upon the idea of what slip or grip is, and how it affects deflection.
End of Part 1

Well, even though you say one two and three are more important, the fact is that my grip is very loose and my cue at 17.2 oz is very light. When I played with the predator, it was nearly 19 oz. In fact, I found it to be so backweighted that I had about .5oz taken out of the back.

I have nothing against the predator. I know that many people like them but the balance of my scruggs is perfect, so think that the person who said to put a predator shaft on it, and when I stated, it would screw up the balance, well this person said that balance did not matter, only low deflection mattered, and that is what I disagreed with.

Last I heard charlie williams swears by predator so obviously it works for him, but according to those who have used or tried my scruggs say it has a very small amount of deflection but a very slight more than the predator.

Personally, although all this is interesting, I would take a perfectly balanced stick anyday over one that is less well balanced but has a minute amount of less deflection. One question though is this: it is possible to have a front weighted cue when a predator shaft is on it. The reason I ask this is because I really hate back weighted cues. The scruggs glides through my fingers like a musical instrument.<G>

JMO

Laura

 

[Bob Jewett]

Colin said:
> Firstly, they have never tried to define slip. Part of the reason for this is that slip,
> or grip is very hard to define in a physics sense. In fact, the entire field of frictional
> physics is full of assumptions, because to really investigate friction we need to
> analyze in deep detail the billions of tiny collisions occurring at a collision interface.

Well, sort of, but the definition of not slipping I'm sure Ron is using is that the contacting surfaces of the tip and ball do not move relative to each other. I think this is the absolutely standard definition used by pretty much everyone studying cases where static friction might turn into sliding friction. Do you think Ron means something else?

> So when the tip hits a cue ball at an angle, to say there is no slip, really assumes
> that the cue tip surface creates a contact surface on the cue ball that is at 90 degrees
> (perpendicular) to the line of the cue.

No, it does not. This seems to be a fundamental misunderstanding on your part. Ron Shepard explicitly calls out non-perpendicular contact surface.

Colin, usually people invent new theories when the current theory does not explain the observed phenomena. Which phenomena do you think are not explained by Shepard's paper?

 

[Bob Jewett]

Bob, does backhand english " aiming "apply to inside and outside english?

The idea of backhand english or the aim-and-pivot method of squirt compensation, which I take to be synonymous, implies no difference between whether the spin will be inside or outside as far as the object ball is concerned. The idea is to get the cue ball to land where it is originally pointed without side spin even though you pivot about your bridge hand to get side spin.

 

[Bob Jewett]

Deflection will occur above or below the pivot point on a cue stick, but not *at* the pivot point! [Pivot point as discussed in the above paper.]

Actually, the same amount of squirt occurs for all pivot points, but if you pivot about the particular pivot point of your cue stick, the change in angle of the pivoting exactly cancels the angle of the squirt, and the cue ball goes where you were hoping to send it.

It might appear that there is no squirt, but it's really still there.

 

[Bob Jewett]

Colin says:
> 1. Balls colliding deflect at almost 90 degrees.

This is true, but has almost nothing to do with the problem of squirt.

> 2. Tips without chalk deflect at high angles. (Without obvious feeling of a miscue).

This is false.

> 3. Poor quality chalks or tips deflect more.

This is false.

> 4. Quality tips well chalked deflect less.

This is false.

> This evidence is observational, and hasn’t been tested in detail, but to most
> players they will seem quite obvious.

I don't think so. Have you even tried to do any experiments?

 

[Colin Colenso]

Colin said:
> Firstly, they have never tried to define slip. Part of the reason for this is that slip,
> or grip is very hard to define in a physics sense. In fact, the entire field of frictional
> physics is full of assumptions, because to really investigate friction we need to
> analyze in deep detail the billions of tiny collisions occurring at a collision interface.

Well, sort of, but the definition of not slipping I'm sure Ron is using is that the contacting surfaces of the tip and ball do not move relative to each other. I think this is the absolutely standard definition used by pretty much everyone studying cases where static friction might turn into sliding friction. Do you think Ron means something else?

> So when the tip hits a cue ball at an angle, to say there is no slip, really assumes
> that the cue tip surface creates a contact surface on the cue ball that is at 90 degrees
> (perpendicular) to the line of the cue.

No, it does not. This seems to be a fundamental misunderstanding on your part. Ron Shepard explicitly calls out non-perpendicular contact surface.

Colin, usually people invent new theories when the current theory does not explain the observed phenomena. Which phenomena do you think are not explained by Shepard's paper?

I listed several observed phenomena that contradict RS's paper in the 3rd Part I posted: These are:
1. The effects of leather tips and chalk in reducing deflection.
2. Players experiencing greater deflection with increased cue speed.
3. Players preferring harder tips to decrease deflection.
4. Meucci Cue testing and player experience indicates stiffer shafts decrease deflection.
5. Predator testing and player experience showing tip diameter affects deflection.
6. That my theory considers the physics at the collision interface.

In fact, I've have not seen Ron be specific about what is going on at the collision interface at all, other that to make some very broad assumption and hence to discount the most important area of deflection effect. That is, the location where friction is occuring. Passing this off as a constant in deflection is like missing the forest for the trees.

I'm not sure what Ron meant by slip. Perhaps he meant that slip would indicate the tip sliding across the cue ball surface making collisions at various points. But if he is talking about that, why doesn't he differentiate the role of friction at the collision point. That is why I assume he is talking about static friction. Anyway, what he means does not effect the conclusions of my theory.

Ron's paper has failed to account for what is occuring at the surface interface. According to his theory, a low end mass cue with a phenolic tip would have low deflection. This would be nonsense. He might argue that slip is occuring, but the collision would not be sliding as you suggest he means the term to say. The collision would be similar to how two balls collide.

Can you show me anywhere that Ron or others have dealt with the collision surface interface in any detail?

 

[Colin Colenso]

Bob, my replies below yours market with *.

Colin says:
> 1. Balls colliding deflect at almost 90 degrees.

This is true, but has almost nothing to do with the problem of squirt.

* It is relevent when we begin to think about how collisions in terms of slide and static friction and beigin to realize that there is no difference between cue balls colliding compared to cue to cue ball collision apart from the surface properties and how this distributes forces.

> 2. Tips without chalk deflect at high angles. (Without obvious feeling of a miscue).

This is false.

* This is easy to proove, and anyone who has been forced to play without chalk has noticed this. Go wipe your tip and play 30 shots without chalk with just enough side so that you don't feel strong vibrations (which is really what a miscue is). You'll see some horible squirt and find it nearly impossible to pot with any side at all.

> 3. Poor quality chalks or tips deflect more.

This is false.

* As above. Try playing with some of that cheap crystaline chalk some bars have. It will gloss the tip up like the surface of a billiard ball. The effects are the same as above.

> 4. Quality tips well chalked deflect less.

This is false.

* As for bad tips, with bad shape the same is true. Try a few games with the cardboard tips that come with most cues.

> This evidence is observational, and hasn’t been tested in detail, but to most
> players they will seem quite obvious.

I don't think so. Have you even tried to do any experiments?

* Yeah, 30 years of hard thinking, playing, testing and observation and taking into account every idea I could find.

I believe the problem here is that you guys think there is a binary type situation going on at the collision interface. That there is either (grip, no slip, a good contact) or it is a miscue.

This may appear to be case, becuase there is a small area range at which the collision effect varies markedly. But it is not an on/off case. There is a transition area.

One problem is understanding and defining what a miscue is. I invite you to try. There is a range of severity of what we call miscues. Some we see but hardly feel, others we see and feel but no one else does, others make the whole room turn around.

Actually, a really bad miscue is just like a collision between two smooth objects such as billiard balls. The reason we notice it so much is that the tip is connected to the cue and as it bounces off the cue ball, it pulls the cue shaft with it, creating quite powerful vibrations and a decent noise. Saying that the cue is slipping along the surface is actually incorrect, but this seems to be what Ron and you guys are thinking. That would be like saying that billiard balls slide along each other's surfaces.

You might point out that the cue is being pushed and so catches back up to the cue ball re-colliding many times. But some simple physics calculation about the speed of the separating objects based on the initial elastic collision would show this to be highly improbable. High speed photography can also provide evidence. Watch here: http://www.engr.colostate.edu/~dga/pool/high_speed_videos/HSV2-1.htm

After the initial collision, there is separation. After that, the cue may bend back into the cue ball. But it is the initial collision we are talking about and this is the same as what we see between billiard balls.

I'm interested in the SF Billiard Academy official position on what a miscue is.

 

[Colin Colenso]

More Video Clips

Actually, this is a much better video:
http://www.engr.colostate.edu/~dga/pool/high_speed_videos/new/HSVA-15.htm

There are several other good videos there:
http://www.engr.colostate.edu/~dga/pool/high_speed_videos/index.html

See the Additional clips near the bottom of the page.

 

[drivermaker]

I wanted to let your post sit for awhile to see if anybody responded to your question about the front weighting aspect. I knew that zilch would reply because it won't happen unless your butt is about 11.5 oz. Would you like to play with a 15 oz. cue or less? You have discovered the true essence of a well made cue...BALANCE. My preference is also forward weighting. The way you've described your Scruggs has me drooling to try it. If we ever meet, can I please try your cue Laura...huh-huh-huh...please Laura...pretty please with whipped cream and cherries on it...

 

[Bluewolf]

I wanted to let your post sit for awhile to see if anybody responded to your question about the front weighting aspect. I knew that zilch would reply because it won't happen unless your butt is about 11.5 oz. Would you like to play with a 15 oz. cue or less? You have discovered the true essence of a well made cue...BALANCE. My preference is also forward weighting. The way you've described your Scruggs has me drooling to try it. If we ever meet, can I please try your cue Laura...huh-huh-huh...please Laura...pretty please with whipped cream and cherries on it...

You got me laughing. Of course you can try my cue. It is funny, the guys in the poolhall do not like it because they are used to their cheap backweighted cues. It is hard to explain. I know the cue is front balance because Tim told me, but rather than feeling the front balance, I do not feel that, what I feel is perfect balance.

To give you another idea. When we first visited Scruggs, he let us shoot with different weighted cues and got us to guess the weight without telling us what it was. We were wrong every single time. The 17oz felt perfect, so did the 19 oz (once we knew what the weights were). That is why we ordered the cue.

Laura