My thoughts on conventional shaft vs. low deflection shaft

[Patrick Johnson]

Cornerman:
You've either misunderstood my post or you don't have the technical understanding beyond the term "tip end mass."

I questioned this comment:

...when people say "it's the tip end mass," they either only say that to keep it as layman as possible or they don't fully understand the theory.

Players don't have robotically rigid grips (are you sure you don't mean bridges?) and decoupled tenons aren't available in the market today, so for practical purposes it is the tip end mass. I think that's why people say it.

pj
chgo

 

[Cornerman]

I questioned this comment:



Players don't have robotically rigid grips (are you sure you don't mean bridges?)

No ,I meant grip. Increased contact time was due to the rigid grip. The increased contact time led to increased effective tip end mass which led to the experimentors to use bubble wrap at the grip to give compliance.

The rigid bridgeconcept is another example of increasing the effective end mass that Bob Jewett mentioned on the other deflection thread, and one that I alluded to bymentioning the Myth Destroyer setup.

and decoupled tenons aren't available in the market today, so for practical purposes it is the tip end mass. I think that's why people say it.

It's important to use that tenon design as an example because it clearly shows that just saying "tip end mass" is incorrect. I'm not sure why you would balk at this.

If someone was going to try to do other things to reduce squirt, it's important that they understand that it's not just "tip end mass." To leave it at that is to throw away years of discussion on this subject. No thanks.

In Dr. Dave's write ups, he even says that shaft stiffness does in fact impact squirt, as he suggests that stiffer shaft have a faster transverse wave propogation rate. That would definitely then increase the mass in effect of the lateral collision.

Fred

 

[DaveK]

.... for squirt; as far as we can tell it's all in the endmass.

pj
chgo

In this article Dr. Dave suggests that tip hardness also affects cue ball path :

http://billiards.colostate.edu/bd_articles/2008/aug08.pdf

It seems like a simple two-tip test, and the subject could be a good candidate for further testing (there are more than two tip hardnesses available).

Do you feel that this is insignificant ? If so, why would Dr. Dave include this phenomena in his studies rather than just toss the idea aside as insignificant ?

Dave

 

[Bob Jewett]

... The rigid bridge concept is another example of increasing the effective end mass ...

An extreme example of this is the shot where you play as if for extreme draw and the tip/ferrule/shaft slide along the cloth as you make tip-ball contact. It is possible to do this without miscuing. In effect, the table is adding to the effective end mass, and you get lots of squirt.

This scoop/slide technique is actually taught in some British books, which is strange because in snooker it is illegal for the cue ball to go over a ball to get a good hit. Maybe it came from English billiards in which hiding the object ball is not a large factor.

I think very few pool players use a bridge short enough or firm enough to affect squirt, except for some robots. In the Jacksonville Experiments (and I think for all of the testing on Iron Willie), there was enough shaft between the bridge and the cue ball that "bridge induced end mass" was probably not an issue. As Fred mentioned above, the firmness of the grip was an issue, and it took a while (most of the testing time, as I recall) to realize that we needed the bubble wrap around the grip on Iron Willie for the "effective stick mass" to be correct.

 

[Bob Jewett]

In this article Dr. Dave suggests that tip hardness also affects cue ball path :

http://billiards.colostate.edu/bd_articles/2008/aug08.pdf

It seems like a simple two-tip test, and the subject could be a good candidate for further testing (there are more than two tip hardnesses available).

Do you feel that this is insignificant ? If so, why would Dr. Dave include this phenomena in his studies rather than just toss the idea aside as insignificant ?

Dave

Tip hardness is hard to measure. I think the usual hardness testing method is a static test with a fairly sharp probe (sharp compared to a cue ball).

The differences in squirt between a hard and soft tip are insignificant in the paper if there is no added weight on the front of the shaft.

As for why any researcher would include factors in a study that turn out to be insignificant, I think the answer is easy. Until you measure the effect of a factor, you don't know whether it is significant or not. Even if you have a fully developed theory that predicts that X has no effect, until you test the hypothesis, you have no confirmation of the theory. And any "confirmation" is simply a test that fails to disprove the theory. Theories can never be proven.

 

[PDX]

It is my understanding that LD shafts are trying to replicate how great solid maple shafts play. Some shafts from the 60's and 70's I have played with where amazing with just enough deflection. It just sucks that $8 in shoddy wood and some technology make a shaft cost $200, and it's made in China. Maybe if Predators where made in the states or where appropriately priced, more would like them. I think they cut down too much squirt. I use squirt in my game. It is easier to pull off a little curve when you get snookered with a normal shaft.

One is meant to have a certain amount of fat in their diet, just as one is meant to have a certain amount squirt in their game.

 

[LAMas]

In this article Dr. Dave suggests that tip hardness also affects cue ball path :

http://billiards.colostate.edu/bd_articles/2008/aug08.pdf

It seems like a simple two-tip test, and the subject could be a good candidate for further testing (there are more than two tip hardnesses available).

Do you feel that this is insignificant ? If so, why would Dr. Dave include this phenomena in his studies rather than just toss the idea aside as insignificant ?

Dave

Thanks for the link.
What I was interested in was the characteristics of the squirt when the Beaver Cue/Shaft was rotated 90 degrees:

Diagram 3 shows results for what I call the “Beaver Cue” experiment. We took a Meucci Red-Dot cue (made from a single piece of wood, not laminated like the Black-Dot tested for my February ’08 article) and cut away wood from both sides of the shaft, leaving a narrow section of wood, as illustrated in the inset figure in Diagram 3. The goal was to test the effects of shaft-end stiffness on endmass and squirt. One would expect the 0º orientation of the cue, where the narrow section of the cut is vertical, to be the least stiff, and the 90º orientation, where the section is horizontal, to be the most stiff. The data does show radial inconsistency (the squirt is about 20% smaller at 90º and about 20% larger at 180º), but I think many people would have expected to see a much larger variation in squirt with the beaver cue. Squirt does change with cue twist angle for this grossly malformed, asymmetric cue, but it doesn’t seem to change much with unmodified cues (for the ones we have tested to date, anyway). This makes sense because the mass of the end of the shaft doesn’t change with orientation. However, the effective endmass does depend on the stiffness of the end of the shaft (see TP A.31), and stiffness can vary with cue orientation. Stiffness variation is what I think explains the trend in Diagram 3.

 

[qbilder]

Whether you prefer low deflection or prefer a certain amount of deflection, is totally a personal preference. I wouldn't try to steer anybody away from what they feel best with.

After six pages of debate, i'm now wondering exactly what it is we are debating. Clearly, we all seem to understand deflection & the affect it has on the game. Clearly, we all agree that some people like low deflection & some people do not. So what exactly are we even talking about?

The point I was trying to make with some facetious questing was that any shaft can be low deflection, no matter what it looks like. And obviously, many people are going to assume that a conventional shaft is not going to be low deflection.

 

[ridewiththewind]

Whether you prefer low deflection or prefer a certain amount of deflection, is totally a personal preference. I wouldn't try to steer anybody away from what they feel best with.

After six pages of debate, i'm now wondering exactly what it is we are debating. Clearly, we all seem to understand deflection & the affect it has on the game. Clearly, we all agree that some people like low deflection & some people do not. So what exactly are we even talking about?

The point I was trying to make with some facetious questing was that any shaft can be low deflection, no matter what it looks like. And obviously, many people are going to assume that a conventional shaft is not going to be low deflection.

LoL, Eric....sometimes these threads leave you feeling like you're chasing you own tail!

Lisa

 

[Patrick Johnson]

In this article Dr. Dave suggests that tip hardness also affects cue ball path :

http://billiards.colostate.edu/bd_articles/2008/aug08.pdf

It seems like a simple two-tip test, and the subject could be a good candidate for further testing (there are more than two tip hardnesses available).

Do you feel that this is insignificant ? If so, why would Dr. Dave include this phenomena in his studies rather than just toss the idea aside as insignificant ?

Dave

Dave's test shows maybe 1/10th of one degree (about 3%) difference in squirt between a hard and a soft tip. I doubt this is significant, and given that he used two different shafts I don't think it's even a reliable measurement. He says as much in the article.

pj
chgo

 

[DaveK]

Tip hardness is hard to measure. I think the usual hardness testing method is a static test with a fairly sharp probe (sharp compared to a cue ball).

Hardness testing has been done across a wide range of materials using many different scales. It seems to me to be a standard well developed science. Does the testing of cue tips require an adjustment to the available test methods ? Perhaps ... as you say a cueball is relatively blunt compared to the test points and balls used in commercial standard test apparatus. Also, it might be better to measure a tips coefficient of restitution, this would need to be investigated (read "more testing"). Hardness testing is often permanant deformation testing, which is not what happens to a tip when it contacts a ball.

The differences in squirt between a hard and soft tip are insignificant in the paper if there is no added weight on the front of the shaft.

Dr. Dave points out his own testing limitations, and suggests some improvements. I suggest that this is a very cursory test, and does not definatively answer the question "does tip hardness affect cueball path".

As for why any researcher would include factors in a study that turn out to be insignificant, I think the answer is easy. Until you measure the effect of a factor, you don't know whether it is significant or not. Even if you have a fully developed theory that predicts that X has no effect, until you test the hypothesis, you have no confirmation of the theory. And any "confirmation" is simply a test that fails to disprove the theory. Theories can never be proven.

Absolutely, all the more reason to do more testing. Dismissing a factor as insignificant without testing the factor is not science, it's more like marketing

Thanks for the comments Bob.

Dave

 

[Cornerman]

Whether you prefer low deflection or prefer a certain amount of deflection, is totally a personal preference. I wouldn't try to steer anybody away from what they feel best with.

I definitely agree.

The point I was trying to make with some facetious questing was that any shaft can be low deflection, no matter what it looks like.

Agree (on normal definition of 'any shaft' )

And obviously, many people are going to assume that a conventional shaft is not going to be low deflection.

Ditto.

Fred <~~~ IMO

 

[enzo]

In this article Dr. Dave suggests that tip hardness also affects cue ball path :

http://billiards.colostate.edu/bd_articles/2008/aug08.pdf

It seems like a simple two-tip test, and the subject could be a good candidate for further testing (there are more than two tip hardnesses available).

Do you feel that this is insignificant ? If so, why would Dr. Dave include this phenomena in his studies rather than just toss the idea aside as insignificant ?

Dave

tip hardness (or more specifically, one particular tip getting harder and harder as it wears down) definitely affects deflection, i don't need no scientific test to tell you that is 100% true. im actually surprised this isn't just total common knowledge to be honest.

 

[Patrick Johnson]

Fred:
It's important to use that tenon design as an example because it clearly shows that just saying "tip end mass" is incorrect. I'm not sure why you would balk at this.

I balk at confusing what we know with what we theorize, because it misleads Joe Cueshopper, who wants to know what definitely matters in cues available today. And I must assume that Joe Cueshopper outnumbers cuebuilders and technogeeks like you and me by a wide margin on AZB.

So I don't mind talking about what technicalities might affect squirt, but we should keep in mind that the vast majority of readers here can't sort the known factors from the theoretical ones or the significant ones from the insignificant ones, so we have to be clear about the differences. The message that matters most to most readers here is that, despite lots of testing of lots of different cues, the only thing we know today that significantly affects squirt in today's cues is end mass.

pj
chgo

 

[KMRUNOUT]

Shaft flexibility doesn't matter to squirt. Two shafts with the same endmass, but one flexible and the other stiff, will squirt the same.

pj
chgo

That may be true. I didn't know that. It is hard to believe, however, that an *extremely* flexible shaft would squirt more than an *extremely* rigid shaft. (I think I'm thinking of going outside the normal parameters for wood)

Any thoughts?

 

[LAMas]

That may be true. I didn't know that. It is hard to believe, however, that an *extremely* flexible shaft would squirt more than an *extremely* rigid shaft. (I think I'm thinking of going outside the normal parameters for wood)

Any thoughts?

Bob Jewett wrote - post #86:
"An extreme example of this is the shot where you play as if for extreme draw and the tip/ferrule/shaft slide along the cloth as you make tip-ball contact. It is possible to do this without miscuing. In effect, the table is adding to the effective end mass, and you get lots of squirt."

Have you ever tried this shot and have the cue ball jump up? It contacted the tip and was deflected/squirted into the air before contacting the table again. This is an extreme example of "adding effective mass", too me this is also what, to some degreee, an inflexable/rigid shaft would also impart if held tightly in your bridge hand, especially if you bridge close to the cue ball.:smile:

 

[greyghost]

That may be true. I didn't know that. It is hard to believe, however, that an *extremely* flexible shaft would squirt more than an *extremely* rigid shaft. (I think I'm thinking of going outside the normal parameters for wood)

Any thoughts?

a stiffer shaft will take the hit and keep its center axis better, you don't have to get as far out of the center for english. This can also lead to increased spin. However you can def be too stiff and the ratio dives backwards and its no good, just the same as the idea with the copper pipe in the shaft. There's so much weight it just plays freakish.

 

[LAMas]

a stiffer shaft will take the hit and keep its center axis better, you don't have to get as far out of the center for english. This can also lead to increased spin. However you can def be too stiff and the ratio dives backwards and its no good, just the same as the idea with the copper pipe in the shaft. There's so much weight it just plays freakish.

How about a shaft made of pine wood which is less dense/lighter/cubic inch. than maple? Too fragile?

 

[Patrick Johnson]

It is hard to believe, however, that an *extremely* flexible shaft would squirt more than an *extremely* rigid shaft. (I think I'm thinking of going outside the normal parameters for wood)

Any thoughts?

I think that doesn't matter in real life.

pj
chgo

 

[greyghost]

How about a shaft made of pine wood which is less dense/lighter/cubic inch. than maple? Too fragile?

not exactly fragile, more like too soft...its a soft wood and its not nearly as rigid as say a maple. Or say maple to purple heart, purple heart is stiffer...thats why they use it in break shafts.