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Billy_Bob
03-25-2007, 01:04 PM
Here is a little experiment I did. I unscrewed the shafts from various cues I have in my pool room. Then I placed just the tip of each shaft on my accurate scale (the joint end resting on the table).

Here are the various weights...
(I know this is not very scientific, but should get the point across.)

Predator 314 shaft A: 1.5 oz
Predator 314 shaft B: 1.55 oz
Predator 314 shaft C: 1.5 oz

Regular shaft A: 1.7 oz
Regular shaft B: 1.6 oz
Regular shaft C: 1.8 oz
Regular shaft D: 2.65 oz ("Laser Cue")

You can see that the predator 314 shafts were all pretty much the same. So they should have the same cue ball deflection (squirt) when using the same shape tip.

But the weights of the "regular shafts" were all over the place. Cue ball deflection (squirt) would be different for each shaft! FYI these "house cues" I have are in the price range of $60 to $150.

For the "Einstein" types, here is the scientific stuff about shafts and cue ball deflection (squirt)...

Everything You Always Wanted to Know About Cue Ball Squirt, But Were Afraid to Ask...
http://www.sfbilliards.com/Shepard_squirt.pdf

Jal
03-25-2007, 02:15 PM
BillyBob, this unfortunately doesn't tell you anything about the effective endmass of the cues. All it does tell you is the amount of upward force you need to apply at the tip to balance the gravitational torque about the joint end of the shaft caused by the mass distribution along the entire length of the shaft. Sorry about that. If it did produce useful information, it would appear that the Predators are not too different from your other cues, which might in fact be the case.

I really do wish you would do the pivot test modified as I suggested in another thread. I'd be willing to put up a whole dollar (American) that you would find that the pivot point is under 15" from the tip.

Jim

jjinfla
03-25-2007, 02:43 PM
You have too much spare time on your hands.

Jake

Jal
03-25-2007, 07:27 PM
<blockquote><font class="small">Quote jjinfla:</font><hr> You have too much spare time on your hands.

Jake <hr /></blockquote>And what about you? At least he's posting about something potentially relevant to pool. Maybe it is or maybe it isn't useful in this case, but he often comes up with interesting stuff...sans the smart remarks.

Jim

Billy_Bob
03-26-2007, 09:20 AM
<blockquote><font class="small">Quote Jal:</font><hr> ...I really do wish you would do the pivot test modified as I suggested in another thread. I'd be willing to put up a whole dollar (American) that you would find that the pivot point is under 15" from the tip. <hr /></blockquote>

Well I'll be the first to admit my pivot point testing is far from accurate. I think you really need to be a "robot" to do this.

I was just pointing out that maybe there is a difference between humans shooting and the testing with robots in that robots may tightly clamp the cue whereas humans have a bit of "cushion" due to the softness of skin around fingers. Maybe place some soft cloth between cue and robot cue clamps to replicate this?

Anyway so far as I am concerned, I found a cue (shaft) and a method of using that cue which allows me to shoot shots with english accurately. So no need for further testing on my part. This testing is a royal pain because I need to do it over and over to see if I get the same results.

But the bottom line is that there is no point in *my* doing this testing and then saying what my test results are. It is best to do this with a robot, but to make the robot as "human" as possible! This would be the most accurate.

Billy_Bob
03-26-2007, 09:37 AM
<blockquote><font class="small">Quote Jal:</font><hr> BillyBob, this unfortunately doesn't tell you anything about the effective endmass of the cues...<hr /></blockquote>

Is there anyway to measure this? Cut of first 6 inches of shaft and weight it? (I'm not going to do this to my cues BTW!)

What I'm thinking is that it would be nice for cue makers to have some way of rating regular shafts in advance for deflection or pivot point. Perhaps cut blocks of wood to the same size, then weight the wood before putting it on the lathe???

Then someone could get a shaft made of wood which is a certain density/weight/(mass?) to order.

What got me to thinking about this is someone on another forum who kept switching cues and was having problems making his shots. I was pointing out that different regular cues will have different deflection. Then I realized Predator has a "known" amount of deflection for its various shafts, but regular shafts do not.

And that I can go out and buy a new Predator 314 shaft, and it will play like my old Predator 314. But I guess it would be like shooting dice with regular shafts as to what deflection you would get?

So I guess depending on the density of the wood... The same species of wood could be less dense or more dense depending on the weather while the tree was growing.

Am I making sense here or am I "dense"? /ccboard/images/graemlins/confused.gif

Jal
03-26-2007, 01:34 PM
<blockquote><font class="small">Quote Billy_Bob:</font><hr>Well I'll be the first to admit my pivot point testing is far from accurate. ...<hr /></blockquote>I wouldn't suggest that your testing is any more inaccurate than anyone else's. A number of people, technically adroit, including Ron Shepard I believe, have gotten pivot distances in the range you've reported (40-50").

<blockquote><font class="small">Quote Billy_Bob:</font><hr>I was just pointing out that maybe there is a difference between humans shooting and the testing with robots in that robots may tightly clamp the cue whereas humans have a bit of "cushion" due to the softness of skin around fingers. Maybe place some soft cloth between cue and robot cue clamps to replicate this?<hr /></blockquote>To my understanding, this shouldn't affect squirt. You can add effective mass to the cue with "steely" grip, but this should only increase the cueball's speed a little, with a tiny effect on squirt. This could be wrong, but both theory and the tests at Platinum (squirt vs speed) seem to support this.

<blockquote><font class="small">Quote Billy_Bob:</font><hr>Anyway so far as I am concerned, I found a cue (shaft) and a method of using that cue which allows me to shoot shots with english accurately. So no need for further testing on my part. This testing is a royal pain because I need to do it over and over to see if I get the same results.<hr /></blockquote>It is tedius, but I'm surprised you don't want an answer enough to put that aside. If I owned a Predator, I think I would jump at the chance since after years and years of discussion, the huge discrepancy remains. (That said, there are plenty of things I should be doing but am not.)

<blockquote><font class="small">Quote Billy_Bob:</font><hr>But the bottom line is that there is no point in *my* doing this testing and then saying what my test results are. It is best to do this with a robot, but to make the robot as "human" as possible! This would be the most accurate. <hr /></blockquote>Maybe the robot is best, but as a practical matter, you, not a robot, have a need to shoot shots with english. I appreciate that you've got a method that works and perhaps don't want to muck with it. If you think that finding out that the true pivot point is somewhere other than where you think it is would harm your game, then by all means forget the test.

Jim

Jal
03-26-2007, 01:46 PM
<blockquote><font class="small">Quote Billy_Bob:</font><hr>Is there anyway to measure this? Cut of first 6 inches of shaft and weight it? (I'm not going to do this to my cues BTW!)<hr /></blockquote>I don't think that even that would do it, although it comes much closer. The mass at the tip is more important than the mass further down, even within that 6" end piece. So it would be hard to compare amongst different ferrule materials vs different wood densities, thicknesses, etc. And stiffness is, to some extent, an integral part of the "endmass", which doesn't get measured here.

<blockquote><font class="small">Quote Billy_Bob:</font><hr>What I'm thinking is that it would be nice for cue makers to have some way of rating regular shafts in advance for deflection or pivot point.<hr /></blockquote>Others have echoed your sentiments, but probably the vast majority of players don't know about squirt/pivot points and couldn't care less.

<blockquote><font class="small">Quote Billy_Bob:</font><hr>Then someone could get a shaft made of wood which is a certain density/weight/(mass?) to order.

What got me to thinking about this is someone on another forum who kept switching cues and was having problems making his shots. I was pointing out that different regular cues will have different deflection. Then I realized Predator has a "known" amount of deflection for its various shafts, but regular shafts do not.

And that I can go out and buy a new Predator 314 shaft, and it will play like my old Predator 314. But I guess it would be like shooting dice with regular shafts as to what deflection you would get?

So I guess depending on the density of the wood... The same species of wood could be less dense or more dense depending on the weather while the tree was growing.

Am I making sense here or am I "dense"? /ccboard/images/graemlins/confused.gif <hr /></blockquote>Those in the know would agree that having a consistent squirt characteristic from cue to cue could only help. I think you're making perfect sense.

Jim

Billy_Bob
03-27-2007, 10:30 AM
<blockquote><font class="small">Quote Jal:</font><hr> ...I appreciate that you've got a method that works and perhaps don't want to muck with it. If you think that finding out that the true pivot point is somewhere other than where you think it is would harm your game, then by all means forget the test.<hr /></blockquote>

Precisely... If it works, don't fix it!