Pool cue stiffness

fish2

AzB Silver Member
Silver Member
What effect does the stiffness of the pool cue (butt and shaft) have on your shot? Some of my cues, vibrates more than the others, I test this by assembling the cue and holding the cue at the handle area near the butt and then I tap the cue with my forearm. I noticed that some butts vibrates more than the others when using the same shaft
 

BC21

https://www.playpoolbetter.com
Gold Member
Silver Member
What effect does the stiffness of the pool cue (butt and shaft) have on your shot? Some of my cues, vibrates more than the others, I test this by assembling the cue and holding the cue at the handle area near the butt and then I tap the cue with my forearm. I noticed that some butts vibrates more than the others when using the same shaft

More shaft stiffness can cause more cb squirt. The butt end makes no difference, other than how it feels when you hit the ball.
 

Patrick Johnson

Fish of the Day
Silver Member
More shaft stiffness can cause more cb squirt.
Not much, if any.

pj
chgo


...stiffness does not have a significant direct effect on squirt. Per the what causes squirt resource page, it is endmass (not shaft stiffness) that is almost entirely responsible for squirt. The following analysis shows how little shaft stiffness contributes directly to squirt:

TP B.19 – Comparison of cue ball deflection (squirt) “endmass” and stiffness effects
 

BC21

https://www.playpoolbetter.com
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Not much, if any.

pj
chgo


Yes, I've read all this stuff and had a little back and forth with Dr. Dave some time back.

Why do you think the lighter end mass causes less cb deflection? I know you know the answer to that, but consider this: If a shaft had zero flexibility there would be maximum cb deflection, regardless of end mass.

Of course, this is on the extreme end of possible outcomes. But it shows that cb deflection relies on two factors: Shaft end mass and shaft deflection/flexibility.

Dr. Dave's response was something along the line of "all shafts have flexibility, so end mass is the determining factor". But until someone tests different shafts for flex strength (resistance to flex), and compares this data to different shaft end masses, it's all assumed.
 

Patrick Johnson

Fish of the Day
Silver Member
Dr. Dave's response was something along the line of "all shafts have flexibility, so end mass is the determining factor".
I think the highlighted part above is an oversimplification of what Dave says, which actually is "...lateral shaft stiffness can indirectly affect squirt by changing the effective “endmass” of the shaft. Lateral shaft stiffness can also have a direct effect on squirt since when a stiffer shaft is flexed (as the CB pushes the tip sideways), the shaft reacts with more sideways force, which can create more squirt. However, typical pool cue shafts are very flexible in the lateral direction (i.e., they don’t require much force to flex), and the shaft does not flex very much during the incredibly brief tip contact time anyway, so stiffness does not have a significant direct effect on squirt."

Another factoid for your database: I have a conical tapered (i.e., very stiff) shaft that squirts less than any other I've tested (~20" pivot length), due solely to its low end mass (small, hollowed tip).

pj
chgo
 
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3kushn

AzB Silver Member
Silver Member
I think the highlighted part above is an oversimplification of what Dave says, which actually is "...lateral shaft stiffness can indirectly affect squirt by changing the effective “endmass” of the shaft. Lateral shaft stiffness can also have a direct effect on squirt since when a stiffer shaft is flexed (as the CB pushes the tip sideways), the shaft reacts with more sideways force, which can create more squirt. However, typical pool cue shafts are very flexible in the lateral direction (i.e., they don’t require much force to flex), and the shaft does not flex very much during the incredibly brief tip contact time anyway, so stiffness does not have a significant direct effect on squirt."

Another factoid for your database: I have a conical tapered (i.e., very stiff) shaft that squirts less than any other I've tested (~20" pivot length), due solely to its low end mass (small, hollowed tip).

pj
chgo
The first custom carom cue I bought, the maker sent me 2 shafts to play around with for a few months to determine which taper I likes best.
One was a cone, the other was slightly relieved (just a tad bit more flex). I chose more flex. At the time I was used to conical shafts, from Longoni, so that wasn't part of the decision. It simply seemed I was able to apply more spin. Maybe it wasn't the case, but it did seem that way. Whatever the deflection is, I'm not bothered with it.

I remember mid 70's when I bought a Meucci. That shaft really vibrated compared to the Adams.

As far as various Butts vibrating differently?? Ringing a cue is a nice test. Probably the shaft is more in tune with one butt over another.
 

Zerksies

Well-known member
The first 12" of your cue effects your shot. The rest just makes you feel all warm and fuzzy on the inside.
 

BC21

https://www.playpoolbetter.com
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I think the highlighted part above is an oversimplification of what Dave says, which actually is "...lateral shaft stiffness can indirectly affect squirt by changing the effective “endmass” of the shaft. Lateral shaft stiffness can also have a direct effect on squirt since when a stiffer shaft is flexed (as the CB pushes the tip sideways), the shaft reacts with more sideways force, which can create more squirt. However, typical pool cue shafts are very flexible in the lateral direction (i.e., they don’t require much force to flex), and the shaft does not flex very much during the incredibly brief tip contact time anyway, so stiffness does not have a significant direct effect on squirt."

Another factoid for your database: I have a conical tapered (i.e., very stiff) shaft that squirts less than any other I've tested (~20" pivot length), due solely to its low end mass (small, hollowed tip).

pj
chgo

This part, where Dr. Dave says, "the shaft does not flex very much during the incredibly brief tip contact time anyway, so stiffness does not have a significant direct effect on squirt." makes very little sense to me.

The shaft must deflect enough to keep the cue's weight from influencing the cue ball too much. In other words, regardless of shaft end mass, if the shaft had zero flex then the cb would get max squirt because the entire mass of the cue would be pushing through the side of the cb, giving way only by whatever amount of play room or cushion there is in the bridge hand. So to say that shaft stiffness/flex is insignificant when it comes to cb squirt seems to a bit of a stretch, or at best pure guesswork.

An interesting experiment would be to test the stiffness of a LD carbon fiber shaft (a Revo) and a LD maple shaft. Then cut the last 3 or 4 inches off of each shaft and weigh the pieces with ferrule and tip. I suspect they will be very close to the same weight, but the stiffness measured in each shaft will likely be quite different. Actually, the carbon fiber would probably weigh a little less than the wood, but I wonder what the stiffness comparison would show.

Dave talks about "typical" pool cue shafts being very flexible, and even though that's true, I would say the flex properties of different shafts vary enough to cause significantly different amounts of cb squirt.

I bet if someone could test a fiberglass shaft with the same end mass as a carbon fiber shaft, the fiberglass shaft would produce less cb squirt because it is much more flexible than carbon fiber.

Anybody wanna cut the ends off your cues and weigh the pieces for us? Lol. Probably not.
 
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Patrick Johnson

Fish of the Day
Silver Member
The shaft must deflect enough to keep the cue's weight from influencing the cue ball too much.
And it seems that Dave is saying the range of actual shaft deflection among pool cues during the 1/1000 second of contact is so small that any differences are too small to make a practical difference in CB squirt. You know he's a recently retired mechanical engineering professor, right?

pj
chgo
 
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BC21

https://www.playpoolbetter.com
Gold Member
Silver Member
And it seems that Dave is saying the range of actual shaft deflection among pool cues during the 1/1000 second of contact is so small that any differences are too small to make a practical difference in CB squirt. You know he's a recently retired mechanical engineering professor, right?

pj
chgo

Yes, and retired mechanical engineering professors are never wrong. Lol

In that 1/1000 of a second impact, every millimeter that the cb doesn't squirt off line is due to the fact that the shaft is forced off line. The lighter the end mass, the easier it is for the 6oz cb to push the end of the shaft out of the way. But the only way the shaft can move out of the way is through the little bit of squishy play in the bridge hand and the actual flexing/bending properties of the shaft.
 

Patrick Johnson

Fish of the Day
Silver Member
Yes, and retired mechanical engineering professors are never wrong. Lol.
I think it’s fair to say they’re right about mechanics far more often than non-mechanical engineering professors - especially the subtle mechanics of the personal passion that they’ve devoted decades of research and instruction to.

You’re no slouch yourself, but I think you might be underestimating the good doctor’s scientific diligence.

pj <- no kind of professor
chgo
 

BC21

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I think it’s fair to say they’re right about mechanics far more often than non-mechanical engineering professors - especially the subtle mechanics of the personal passion that they’ve devoted decades of research and instruction to.

You’re no slouch yourself, but I think you might be underestimating the good doctor’s scientific diligence.

pj <- no kind of professor
chgo

I should not have insinuated that Dave is wrong. I mean, he is 100% correct, based on the testing he's done. It just seems that there are other tests and checks that could be made before reaching a definite conclusion that shaft stiffness is insignificant when it comes to cb squirt/deflection.

One thing is certain, there's a very good chance that I'm wrong. Lol. But when I think of extreme scenarios, it seems obvious that a super flexible shaft would cause less cb squirt than a stiffer shaft, if both end masses were equal.

I understand what Dr. Dave is saying about shaft flexibility, that there isn't an effective difference between different shafts. But it would be nice to know if any shafts have actually been tested for stiffness/flexibility, or if so much focus has been on end mass (because that has proven to be a significant factor) that stiffness hasn't really been looked at that closely.
 

FranCrimi

AzB Silver Member
Silver Member
I should not have insinuated that Dave is wrong. I mean, he is 100% correct, based on the testing he's done. It just seems that there are other tests and checks that could be made before reaching a definite conclusion that shaft stiffness is insignificant when it comes to cb squirt/deflection.

One thing is certain, there's a very good chance that I'm wrong. Lol. But when I think of extreme scenarios, it seems obvious that a super flexible shaft would cause less cb squirt than a stiffer shaft, if both end masses were equal.

I understand what Dr. Dave is saying about shaft flexibility, that there isn't an effective difference between different shafts. But it would be nice to know if any shafts have actually been tested for stiffness/flexibility, or if so much focus has been on end mass (because that has proven to be a significant factor) that stiffness hasn't really been looked at that closely.
Thank you for saying this. I see this a lot in our industry. I'm very grateful for scientific information about our sport, but please 1) Consider variables that may not support your hypothesis, but may support the truth, and 2) Don't be so definite with your answer as if it were the only answer. There may be other tests worth trying.
 

fish2

AzB Silver Member
Silver Member
If a shaft has a lighter end mass, it would move out of the way, reducing squirt, more than a heavier end mass cue, A whippy shaft will also move out of the way more than a stiff shaft, reducing squirt, somebody please test this scientifically...
 

Bob Jewett

AZB Osmium Member
Staff member
Gold Member
Silver Member
If a shaft has a lighter end mass, it would move out of the way, reducing squirt, more than a heavier end mass cue, A whippy shaft will also move out of the way more than a stiff shaft, reducing squirt, somebody please test this scientifically...
Changing just the end mass is a relatively very easy thing to do. Simple, effective experiments were done by participants here (and predecessor discussion groups) over 20 years ago. Changing stiffness without changing other parameters is a very difficult thing to so.

As has been stated already, very stiff shafts -- conical carom taper -- can have very low squirt. But that's also with very short ferrules and small tips, Theory does say that more stiffness will increase squirt but in all the practical situations we see, stiffness seems unimportant.

In the end, the causes are interesting to some fanatics but they are useful only to cue designers. I imagine that Predator has done some testing with their robot of the effect of stiffness, but I think they are primarily interested in achieving a low level of squirt in a practical, manufacturable shaft.
 
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