PDA

View Full Version : Cue Ball Deflection



slipstroke
01-21-2005, 01:43 PM
Was rereading articles in the Aug, Sep and Oct 2002 issues of Billiards Digest by Bob Jewett on cue ball deflection (squirt), so I guess my question would be for Bob, but anyone else can chime in if they like. Which causes more squirt, a shaft that is fairly flexible or one that is stiffer? This difference being measured in the portion of the shaft 12 to 15 inches from the tip.
Thanks,
Slipstroke

GeraldG
01-21-2005, 02:03 PM
I'm interested in hearing this too. It would seem intuitive to me that the stiffer shaft would cause more "squirt" when using sidespin. On a dead center shot on the cueball there shouldn't be any appreciable deflection from either shaft, but one shaft (probably the stiffer shaft) would cause more rapid acceleration of the cueball where the more flxible shaft would tend to absorb some of the energy. With sidespin, I would think that the stiffer shaft would produce more deflection because it will transfer more energy to the cueball both forward and sideways, whereas the "springier" shaft will absorb more of the sideways directed energy and will deflect (or bend) to the opposite side from the cueball somewhat more.

pooltchr
01-21-2005, 02:52 PM
This has come up once or twice before. The prevailing opinion is that it's not the flexibility of the shaft, but the mass (weight/density) of the end of the shaft around the tip and ferrule. The less mass in the end of the cue, the less cue ball deflection.

Now I'm going to sit back and watch. /ccboard/images/graemlins/grin.gif

DavidMorris
01-21-2005, 02:52 PM
I think the general scientific consensus will be that squirt is effected less by shaft flexibility and more by tip-end mass. The greater the mass at the tip end, the more it resists the tendency to deflect away from the CB when english is applied, thus it deflects the CB more. Predator shafts are believed to reduce squirt not so much because they are radially laminated (as is commonly believed), but more because the last 6 inches or so of the shaft is hollowed out and filled with foam, which reduces tip-end mass.

Although I've never tried it, I've heard it said to tape or rubber-band a weight to the ferrule of your cue, as close as you can to the tip without interfering with the CB, and stroke a few shots with english, aiming at a specific diamond or object ball at table length. The greater tip-end mass should result in more observed squirt.

DavidMorris
01-21-2005, 02:53 PM
Darn you pooltchr! Beat me by a sub-minute! /ccboard/images/graemlins/laugh.gif

GeraldG
01-21-2005, 03:19 PM
OK...I guess that makes sense, too.

Bob_Jewett
01-24-2005, 09:02 PM
<blockquote><font class="small">Quote slipstroke:</font><hr> ... Which causes more squirt, a shaft that is fairly flexible or one that is stiffer? This difference being measured in the portion of the shaft 12 to 15 inches from the tip.
... <hr /></blockquote>
There is a concept of "effective end mass" in squirt, which is how much of the shaft participates in pushing the cue ball to the side. I think that if all other things are equal, more stiffness will cause more of the shaft to participate and there will be more squirt. Usually, other things are not equal, so it is hard to do a good experiment. I see no easy way to vary just the stiffness, although playing with/against the grain (by rotating the shaft 90 degrees) might be one way to do a crude measurement. I think Bob Meucci has already reported on doing such a test.

dr_dave
01-25-2005, 03:22 PM
As others have pointed out, the amount of squirt is a function of the "effective end mass." All other things being equal, if the end mass is less, the end will also be less stiff (i.e., more flexible). So, in general, a low-squirt cue has less end-mass AND is more flexible (less stiff) in the shaft.

Rod
01-25-2005, 03:56 PM
I don't know this is necessarly true. That is, the more flexable part. I can't hit anything with a flexable shaft. The ball squirts off so far it would take me forever to get use to.

Predator, while fairly accurate, has a moderate amount of flex. So, there is a point and we don't know what that point is for everyone. I think it's more, who is using the cue and what their familiar with. A blanket statement here just doesn't work IMO.

Rod

SpiderMan
01-25-2005, 04:07 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> As others have pointed out, the amount of squirt is a function of the "effective end mass." All other things being equal, if the end mass is less, the end will also be less stiff (i.e., more flexible). So, in general, a low-squirt cue has less end-mass AND is more flexible (less stiff) in the shaft. <hr /></blockquote>

I'll have to disagree here. Stiffness and mass are not necessarily related. A shaft could be made of very flexible material, yet if the end mass were high it would result in substantial cueball deflection. The predator design had reduced end mass, yet was not overly flexible.

I agree, however, with Bob Jewett's observation that stiffness would play a part in deflection. The stiffer a shaft, the more of the length is rigidly coupled to the "end", which would result in an increased effective end mass and increased deflection.

It makes me wonder which variable dominates, and by how much? At what point do you begin to see dimished returns from reducing true mass, if you don't also reduce stiffness and coupling?

SpiderMan

dr_dave
01-25-2005, 04:09 PM
<blockquote><font class="small">Quote Rod:</font><hr> I don't know this is necessarly true. That is, the more flexable part. I can't hit anything with a flexable shaft. The ball squirts off so far it would take me forever to get use to.

Predator, while fairly accurate, has a moderate amount of flex. So, there is a point and we don't know what that point is for everyone. I think it's more, who is using the cue and what their familiar with. A blanket statement here just doesn't work IMO.<hr /></blockquote>
What I am saying is:

If you take a wood shaft and drill out its core at the ferrule end, the shaft will:
<ul type="square"> have less end mass
be less stiff (more flexible) at the ferrule end of the shaft, because you have removed some material that helps provide stiffness
exhibit less squirt[/list]
Does that sound reasonable?

On the flip side, if you build up the ferrule end of a shaft by adding material, you would increase end mass, add stiffness to the shaft, and increase squirt.

PS: I wouldn't recommend trying these experiments with your favorite cue /ccboard/images/graemlins/wink.gif

dr_dave
01-25-2005, 04:14 PM
<blockquote><font class="small">Quote SpiderMan:</font><hr>I'll have to disagree here. Stiffness and mass are not necessarily related. A shaft could be made of very flexible material, yet if the end mass were high it would result in substantial cueball deflection. The predator design had reduced end mass, yet was not overly flexible.<hr /></blockquote>
Please see my answer to Rod (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&amp;Board=ccb&amp;Number=176714&amp;page =&amp;view=&amp;sb=&amp;o=&amp;vc=1) and let us know what you think.

Rod
01-25-2005, 04:15 PM
[ QUOTE ]
Does that sound reasonable?
<hr /></blockquote>

Yes it does Dave.

dr_dave
01-25-2005, 04:20 PM
<blockquote><font class="small">Quote Rod:</font><hr> &lt;/font&gt;&lt;blockquote&gt;&lt;font class="small"&gt;Quote:&lt;/font&gt;&lt;hr /&gt;
Does that sound reasonable?
<hr /></blockquote>

Yes it does Dave. <hr /></blockquote>
Thank you, Rod. You are a true gentleman.

Rod
01-25-2005, 04:27 PM
[ QUOTE ]
It makes me wonder which variable dominates, and by how much? At what point do you begin to see dimished returns from reducing true mass, if you don't also reduce stiffness and coupling <hr /></blockquote>

I haven't a clue, but I really don't wonder either. /ccboard/images/graemlins/laugh.gif However for a well made shaft within those parimeters, I'd bet the aim point wouldn't vary more than a knats a$$ wide! /ccboard/images/graemlins/laugh.gif Just a tougue in cheek statement but not far fetched. People should be concerned with stroke fundamentals, there is far more error there alone. Not saying you Marty, just a comment.

Rod

SpiderMan
01-26-2005, 03:24 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> What I am saying is:

If you take a wood shaft and drill out its core at the ferrule end, the shaft will:
<ul type="square"> have less end mass
be less stiff (more flexible) at the ferrule end of the shaft, because you have removed some material that helps provide stiffness
exhibit less squirt[/list]
Does that sound reasonable?

On the flip side, if you build up the ferrule end of a shaft by adding material, you would increase end mass, add stiffness to the shaft, and increase squirt.
<hr /></blockquote>

Dave,

I agree completely with both of the above assertions. My disagreement was with your original statement:

<blockquote><font class="small">Quote Dr Dave:</font><hr>"All other things being equal, if the end mass is less, the end will also be less stiff (i.e., more flexible). So, in general, a low-squirt cue has less end-mass AND is more flexible (less stiff) in the shaft."<hr /></blockquote>

This is not, in general, the case. To repeat an example, the Predator 314 has reduced end mass but is relatively stiff. Stiffness and mass are not absolutely linked, but are functions of material choice and many other design parameters.

SpiderMan