@DrDave, Bob Jewett - valid deflection test?

M

Meucciplayer

AzB Silver Member
Silver Member
I am specifically asking for your opinion, DrDave and Bob Jewett. Because you have put a lot of thought into deflection testing in the past and done quite a few experiments.

Would you consider this to be a valid test for measuring deflection? I have my doubts and I tend to believe you could achieve similar results with almost any shaft, LD, HD or CF. Maybe I'm wrong ...

https://www.youtube.com/watch?v=vWRuNjm5Vos
 
Interesting test.
I have a couple of questions.

1. Is there any chance you may have applied a little backhand english?
2. Have you tried the test on both sides of the table?

The reason I ask is that when I did your test with my 32" 11MM tip solid wood shaft, I got even less deflection.
Also, when I did the test Dr. Dave did, I got the same results.

Could it be a wood shaft with an 11MM tip and 3/8" ferrule can equal or beat a carbon shaft?
 
Just a quick reply: this is not MY test. It was posted to prove s.th. in another forum but I don't believe it is valid for any kind of proof. I may be mistaken, however.

My understanding is that really thin shafts cause less cb deflection - same density/material being used. But even there I am much less qualified than DrDave or Bob to answer.
 
It is NOT an invalid test (it does show something);

However it is not a definitive test (it is not consistently repeatable), either.
 
Since there's no way to know how he aims or hits the balls, or if he does it precisely the same way each time, there's no way to know how much squirt he's generating. His test needs controls.

pj
chgo
 
@ctyhntr: Those tests are different. I know what DrDave recommends for testing.

The "test" in the video is - as PJ mentioned - highly questionable, IMHO. I don't even know what exactly the guy tries to prove by shooting along the long rail. I don't see that you couldn't do it even with a really HD-shaft. But maybe I am missing something here.
 
Meucciplayer said:
@ctyhntr: Those tests are different. I know what DrDave recommends for testing.

The "test" in the video is - as PJ mentioned - highly questionable, IMHO. I don't even know what exactly the guy tries to prove by shooting along the long rail. I don't see that you couldn't do it even with a really HD-shaft. But maybe I am missing something here.
Click to expand...

I agree that it's not the most accurate test for shaft deflection. But it's a good idea. He uses the rail and camera angle to show how much offline the ball goes when hit with right english. With zero squirt the ob shouldn't move away from the rail at all. But, as already pointed out, there is no guarantee of consistency in speed and applied spin. So it's a flawed test in that respect. And with the ball starting out frozen to the rail the stroke must be perfectly parallel to the rail to avoid slightly shooting the ball into the rail, which would make it look like it squirted more.

And you are correct, it's assumed that a thinner shaft will have less end mass, and will therefore deflect more and cause less cb squirt. I say "assumed" because a heavier, more dense, material could make this untrue. In other words, you could actually have a 12mm shaft that's stiffer and has more end mass than a 14mm shaft made from a different wood or material. But, generally thinner means lighter and more flexible, so less cb deflection/squirt.
 
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MitchAlsup said:
It is NOT an invalid test (it does show something);

However it is not a definitive test (it is not consistently repeatable), either.
Click to expand...
Seems like it could be slightly more accurate test if the ball was placed 1/8" off the side rail to start with, which would rule out any possibility that the ball was accidentally hit slightly into the rail to start with, which could be a factor (in addition to deflection) causing it to leave the rail as travels down the table.
 
MitchAlsup said:
It is NOT an invalid test (it does show something)
Click to expand...
We can assume he's trying to stroke exactly parallel with the rail and trying to hit the same spot on the CB, and I think he hits it hard enough to make swerve negligible. But we don't know how well or consistently he's doing those things. And even if we assume the best it doesn't tell us how much the cues squirt, only how they roughly compare - if he did it a whole bunch of times and averaged.

pj
chgo
 
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Well, my own line of thinking is that it is almost impossible to set this up correctly to prove a minor deflection difference between cues. The reasons being that it is a) hard to set the cue ball up EXACTLY on the rail (1/100th of an inch would make a difference) b) an ever so slight angle while shooting into/out of the rail and c) adding to that all minor factors in the stroke itself.

All of those possible error sources added together would IMHO make a greater difference than the minor deflection difference caused by those two cues (Revo and Cuetec cf shafts).

So in the end my reasoning was that DrDaves suggested tests for deflection take away a couple of those possible sources of testing flaws. But maybe this test isn't as bad as I think it is because with a relatively straight shot the error margin isn't quite as great as I take it to be ... ?
 
Meucciplayer said:
I am specifically asking for your opinion, DrDave and Bob Jewett. Because you have put a lot of thought into deflection testing in the past and done quite a few experiments.

Would you consider this to be a valid test for measuring deflection? I have my doubts and I tend to believe you could achieve similar results with almost any shaft, LD, HD or CF. Maybe I'm wrong ...

https://www.youtube.com/watch?v=vWRuNjm5Vos
Click to expand...
A test like that can be valid if the shooter aims consistently, hits the CB in the same place with every shot (and with the same cue elevation), uses a consistent CB speed, and does a large number of trials. It is difficult to verify these things from the video.

An easier and more reliable way to test and compare shafts is to measure the natural pivot length using the simple procedure starting at the 4:22 point in the following video:

NV J.12 - How to Select a Pool Cue, Cue Ball Deflection, Carbon Fiber, Revo vs. Cuetec

Regards,
Dave

PS: FYI, guidelines that should be followed when doing shaft CB deflection tests are summarized here:

Rules of CB Deflection Testing
 
Question - how does learning to MEASURE deflection help one become a better player??

Learning how to MANAGE, or use, or incorporate deflection helps your game.

But this is like measuring a board to cut it, but you don't know how to use the saw.

JMO. YMMV.

-von
 
VonRhett said:
Question - how does learning to MEASURE deflection help one become a better player??
Click to expand...
Knowing where your cue's pivot point is can help learn to adjust for squirt/swerve - for instance by knowing where to pivot for backhand english.

pj
chgo
 
Thanks PJ.

Actually, it was a rhetorical question. :grin:

My point was that too many young and/or inexperienced players focus on the physics, stats and measurements, long before they have developed the stroke, skills and knowledge to apply them.

-von
 
dr_dave said:
A test like that can be valid if the shooter aims consistently, hits the CB in the same place with every shot (and with the same cue elevation), uses a consistent CB speed, and does a large number of trials. It is difficult to verify these things from the video.

An easier and more reliable way to test and compare shafts is to measure the natural pivot length using the simple procedure starting at the 4:22 point in the following video:

NV J.12 - How to Select a Pool Cue, Cue Ball Deflection, Carbon Fiber, Revo vs. Cuetec

Regards,
Dave

PS: FYI, guidelines that should be followed when doing shaft CB deflection tests are summarized here:

Rules of CB Deflection Testing
Click to expand...

If you want to have one of the most popular videos on youtube just create a video of your deflection test of all the CF shafts available and their direct comparison of pivot points and how much the ball squirts on table length shots with fast, medium and slow speed ;) But be sure to name all of them in video description, maybe even in the title!
 
dr_dave said:
A test like that can be valid if the shooter aims consistently, hits the CB in the same place with every shot (and with the same cue elevation), uses a consistent CB speed, and does a large number of trials. It is difficult to verify these things from the video.

An easier and more reliable way to test and compare shafts is to measure the natural pivot length using the simple procedure starting at the 4:22 point in the following video:

NV J.12 - How to Select a Pool Cue, Cue Ball Deflection, Carbon Fiber, Revo vs. Cuetec

Regards,
Dave

PS: FYI, guidelines that should be followed when doing shaft CB deflection tests are summarized here:

Rules of CB Deflection Testing
Click to expand...

Thank you very much, DrDave. Yes, I know your deflection tests and have used them myself already. For me personally, it was more of an exercise to find out my personal pivot point, as others have stated. A little curiosity might also have been involved WRT the deflection properties of my Meucci shafts.

I used another test you recommended before your last videos. Back then, your set-up consisted of a ball lying about 1 diamond from a corner pocket in a 45 degree angle. You had to ensure you could accomplish a perfect stop shot and then do the same stop shot with varying pivot lengths and English to find out the natural pivot length. I suppose you now prefer the new method with the cueball passing between the 2 balls in the jaws of a pocket? (Well, the old method worked for me to find out my natural pivot length). I suppose your new method has a little less margin for error.

So, I guess it is safe to say that your current method of determining deflection/natural pivot length is way superior to the method shown in the video.
 
Meucciplayer said:
I am specifically asking for your opinion, DrDave and Bob Jewett. Because you have put a lot of thought into deflection testing in the past and done quite a few experiments.

Would you consider this to be a valid test for measuring deflection? I have my doubts and I tend to believe you could achieve similar results with almost any shaft, LD, HD or CF. Maybe I'm wrong ...

https://www.youtube.com/watch?v=vWRuNjm5Vos
Click to expand...
I see a technical issue with the test that might be a problem.

It looks like the distance of the shaft from the cushion is set by the thickness of his finger if his finger is tight against the nose of the cushion. It is good to control the left-right position of the cue stick. The problem though is that you want to control the other side of the shaft -- the one that hits the ball. (More exactly, it would be a point a little inside the other side of the shaft where the actual contact point on the ball is.)

Imagine a 2-inch diameter shaft. The bridge will force him to hit almost on the wrong side of the cue ball. That is an extreme case just to show you the direction of the influence. This points out that if the shafts are different diameters and the bridge does anchor the side of the shaft to the rail a systematic error is introduced.

When I demo squirt I show the shot I originally proposed to measure squirt: play a 90-degree cut shot with a ball frozen on the center of the far end rail by hitting rail first and using extreme inside english. I ask the student to estimate where my stick is actually pointed on a shot that makes the ball, such as for what looks like a full-ball aim or even aim on the wrong side of the ball. (I try to be near the miscue limit.)

Of course I should hit the ball at the same speed and with the same spin for each cue stick I do the demo with and maybe I come close to such control. For the purpose of demoing squirt and the fact that different cues have different amounts of squirt, that's not so important. In fact, I may have a similar error as the OP test for shafts of different diameter if I'm setting up the middle of the shaft in the same place -- I will have less side spin for thick shafts.
 
This is why I linked to Dr. Dave's templates and resources. Dr. Dave has provided a repeatable and superior method for others to conduct testing.

Meucciplayer said:
@ctyhntr: Those tests are different. I know what DrDave recommends for testing.

The "test" in the video is - as PJ mentioned - highly questionable, IMHO. I don't even know what exactly the guy tries to prove by shooting along the long rail. I don't see that you couldn't do it even with a really HD-shaft. But maybe I am missing something here.
Click to expand...
 
Meucciplayer said:
I am specifically asking for your opinion, DrDave and Bob Jewett. Because you have put a lot of thought into deflection testing in the past and done quite a few experiments.

Would you consider this to be a valid test for measuring deflection? I have my doubts and I tend to believe you could achieve similar results with almost any shaft, LD, HD or CF. Maybe I'm wrong ...

https://www.youtube.com/watch?v=vWRuNjm5Vos
Click to expand...

I just played with a Cuetec CF shaft, it deflects more than the REVO. From using it a for a few racks, I would say the Cuetec CF is about the same deflection as a standard good quality LD shaft, the hit feel and deflection is not much different from a wood shaft. Which really defeats the purpose of having a new tech shaft for me.

I don't know if I would trust a specific LD test done by a human to know exactly how shafts compare past "more deflection" or "less deflection".
 
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