LD shaft for one pocket?

[dr_dave]

Anyone have any ideas why a LD shaft might be bad for one-hole? Or why it might be good?

I think an LD shaft might be bad for many 1P players because many 1P players are old-timers. Old-timers prefer regular shafts because that is what they have used most of their lives. LD shafts have many advantages and disadvantages for different people. For more info, with link to many useful resources on the topic, see:

http://billiards.colostate.edu/threads/cue.html#low_squirt​

Regards,
Dave

 

[dr_dave]

Mike Page has done an interesting experiment that suggests your bridge need to be very firm and less than 6 inches from the cue ball. Even then, the main expected result is an increase in squirt, which is usually not what players want.

I have also done many experiments, analysis, and video demos related to squirt (AKA cue ball deflection), and I support what PJ and Bob have stated in this thread. For those that are interested, I have links to many articles and videos dealing with many questions related to squirt here:

http://billiards.colostate.edu/threads/squirt.html​

A particularly relevant section dealing with possible bridge length effects, including a link to Mike Page's video, can be found here:

http://billiards.colostate.edu/threads/squirt.html#endmass​

Regards,
Dave

 

[dr_dave]

That's one point that I'm not sure about (which may just be my own ignorance). I haven't seen a lot of REALLY precise data on that topic. From Dr.Dave I've read that contact lasts "about 1 ms. with leather tips and about 0.5 ms with phenolic." But:

1) I haven't ever seen any REALLY precise contact times: If one hit lasts 0.8 ms, and another lasts 1.2 ms, the second is a full FIFTY PERCENT longer--yet they're both "about" 1 ms.

2) I haven't heard of anyone even TRYING to get good measurements (down to about a microsecond would be needed to make really definitive conclusions, I'm imagining/guessing). The work I've heard about has been done with high speed photography (or video). To realistically get microsecond level data you would need instead to place sensors under the tip--I haven't heard of anyone doing that. EVENTUALLY, I'll get around to it--look for the data in 2-3 years

3) It COULD be claimed, perhaps, that the elastic realities of phenolic (balls) and leather (tip) are such that no "interesting" information can pass between tip and CB in the microsecond time frame; i.e., it just wouldn't MATTER if contact time were, say, 0.8 ms vs 1.2 ms. I'd be interested in Dr.Dave's thoughts on that issue.

Good point about the tip contact times varying quite a bit with tip hardness. I would also be interested in seeing some more-precise experimental data to back up and improve the video results.

Since you asked, my thoughts on the matter are: Neither the bridge hand nor grip hand can have a significant effect during the extremely small tip contact times. 1.2ms is very different from 0.8ms, but they are both extremely small in relation to the response of human flesh. FYI, all of my current thoughts and results on this issue can be found under these topics in my FAQ pages:

cue tip contact time
effects of light vs. tight grip
shaft endmass and stiffness effects​

Regards,
Dave

 

[dr_dave]

Hi Bob. Like Kaufman, I have played many years with the same standard shaft(s) and so small aiming adjustments when using side english probably happen without me thinking about it. On a cut shot using inside english, particularly when the ball is on the rail, I think I sometimes use a certain stroke to introduce a little swerve to compensate for squirt. Do you have a feeling for if this is common or likely, or would you suspect the end result of my stroke at point of impact is really me using a little back-hand english?

EDIT: I just reread your 2004 article on back-hand english. What I am describing you call in that article aim and swerve...and a recipe for disaster.

Back-hand English (BHE) is very different from stroke swoop, but both can be effective at compensating for squirt; although, I agree with Bob that stroke swoop might be more difficult to control. FYI, I have some videos on this topic here:

http://billiards.colostate.edu/threads/stroke.html#swoop​

One advantage of the stroke swoop method is the initial alignment is center-ball which might be more comfortable for some people. With BHE, the pivot-before-stroke alignment can be disconcerting (because the final alignment looks crooked). However, it can be difficult (i.e., it takes lots of practice) to be consistent with a swooping stroke.

Regards,
Dave

 

[GetMeThere]

Since you asked, my thoughts on the matter are: Neither the bridge hand nor grip hand can have a significant effect during the extremely small tip contact times. 1.2ms is very different from 0.8ms, but they are both extremely small in relation to the response of human flesh.

I agree completely that the human nervous system can't do ANYTHING on that time frame--it takes longer for ion channels to open and relative charge start to change across a neuronal membrane than that. You can't suddenly move any part of any muscle, or even THINK about it, on that time frame.

But that doesn't answer the question about WHY the variability occurs. If "enough" can happen between the tip and CB over the span of 1ms, to make happen all the interesting things we see--then you have to wonder what DIFFERENT things might be happening by a FIFTY PERCENT VARIATION in that figure--whether or not those things arise from a human intention.

I don't claim to have any good ideas about what's happening; I'm only saying that I'm not used to seeing that much percentage variability in "simple reducible physical interactions."

I'd settle for an answer to the simple question: If a tip hits a CB at point X, with speed Y, from angle Z, and the contact lasts for 1.2 ms, then what changes in the outcome when X, Y, and Z happen and the contact lasts for 0.8 ms?

 

[Patrick Johnson]

Dave:
...Neither the bridge hand nor grip hand can have a significant effect during the extremely small tip contact times. 1.2ms is very different from 0.8ms, but they are both extremely small in relation to the response of human flesh.

GetMeThere:
I agree completely that the human nervous system can't do ANYTHING on that time frame

If I'm not mistaken, Dave was thinking of the way soft flesh yields upon tip/ball contact and is therefore unable to affect tip/ball interaction. The hand is effectively "uncoupled" from the stick during contact.

...If "enough" can happen between the tip and CB over the span of 1ms, to make happen all the interesting things we see

All what interesting things?

--then you have to wonder what DIFFERENT things might be happening by a FIFTY PERCENT VARIATION in that figure--whether or not those things arise from a human intention.

We already see variations in contact time up to at least 100% with no evident change in results.

pj
chgo

 

[Bob Jewett]

... I'd settle for an answer to the simple question: If a tip hits a CB at point X, with speed Y, from angle Z, and the contact lasts for 1.2 ms, then what changes in the outcome when X, Y, and Z happen and the contact lasts for 0.8 ms?

Physics says that essentially nothing changes for that change in contact time. If you're using side spin, there will be slightly more squirt, slightly more spin, and slightly less speed, but you could get the same difference pretty much by hitting slightly farther off center. In general, it's a bad idea to prolong the contact time.

 

[GetMeThere]

Physics says that essentially nothing changes for that change in contact time. If you're using side spin, there will be slightly more squirt, slightly more spin, and slightly less speed, but you could get the same difference pretty much by hitting slightly farther off center. In general, it's a bad idea to prolong the contact time.

Sorry, I just can't easily accept the notion that a FIFTY PERCENT change in a physical parameter can have virtually no effect. It's a huge difference.

What I'm leading to with this (or the main thing) is the idea of "mystical superstroke." It's pervasive throughout the pool world--and I can't deny having been susceptible to it myself: you see guys who can strike the ball seemingly almost casually--and draw the CB the length of the table.

Arguments that only the speed of the tip at time of contact, and the area it strikes, determine the amount of draw (for example) make perfect sense to me--which doesn't change the fact that many people observing pool feel they SEE THINGS differently.

Then, when I'm told that tip contact times do in fact vary a lot on a percentage scale (400 microseconds isn't a lot of time--I can't disagree, but neither is 800 microseconds. 1200 is MUCH different from 800, on a percentage basis)--I have to wonder if maybe that's where "the magic is."

So far (mostly from bouncing around at Dr. Dave's site) I've not noticed a solid and complete explication on this issue. One obvious reason why, is that you can't really do it practically and precisely via high-speed video--and I think that's all he has (and, I have a suspicion, all that ANYONE has).

What's needed is a pressure transducer under the tip, that can measure the magnitude and duration of these forces on the microsecond time scale.

I want to see absolute proof that, in a nice draw shot, for example, two hits can occur at X point on the CB, at Y speed of the tip--one contact lasting for 0.8 ms, and one lasting for 1.2 ms, and the draw distance is virtually the same. I've heard many ASSURANCES that it will be same--but I haven't seen the demonstration. And the existence of a potential 50% variation in contact time allows for room for doubt.

 

[GetMeThere]

If I'm not mistaken, Dave was thinking of the way soft flesh yields upon tip/ball contact and is therefore unable to affect tip/ball interaction. The hand is effectively "uncoupled" from the stick during contact.

That doesn't have to matter (I might presume). The difference could be in "how" the cue movement is delivered. For example, if there were constant acceleration, the "flesh factor" wouldn't necessarily matter: the flesh would already be stretched by the action of accelerating the cue. I'm not necessarily saying the cue action itself CHANGES over the 400 microsecond period. I'm saying that perhaps the METHOD by which the cue was delivered to that point contained some physical attribute that ALLOWED for the 400 microsecond difference, and that caused a different result. I don't know; I'm not saying I do. I'd just like to see data from an actual DEMONSTRATION.

All what interesting things?

Presumably, everything that DOES happen in pool, is "transduced" during the contact time between tip and ball. If that "everything" can happen in 800 microseconds, then perhaps something VERY DIFFERENT could occur over 1200 microseconds.

We already see variations in contact time up to at least 100% with no evident change in results.

Do we? If I KNEW that were true (if I could see someone's precision data) then my question would be resolved. I want to see two examples, in which all other parameters are the same (tip speed, CB contact point, and CB response--like a lot of draw, for example), where the tip-ball contact time varied by 50 %. Then I could know that a 50% variation in tip contact time means nothing.

 

[GetMeThere]

One classic example is given here, at about time 1:55. It's Corey Deuel making the CB bend a huge amount with draw, after hitting the rail.

The entire crowd (including Mika Immonen--we're told by Jim Wych) is unable to inhibit their oohs and aahs. Even Billy Incardona is overcome.

If only the CB contact point and speed matter, why are all these highly experienced players (like Mika and Billy--and Jim Wych) so blown away by the extent of the draw?

One reason is that he really doesn't even seem to hit the ball that hard. Looking at the time the CB takes to travel to the OB, it would look to me about HALF the speed of a break shot.

It's these types of shots that create the idea of "superstroke."

 

[lfigueroa]

One classic example is given here, at about time 1:55. It's Corey Deuel making the CB bend a huge amount with draw, after hitting the rail.

The entire crowd (including Mika Immonen--we're told by Jim Wych) is unable to inhibit their oohs and aahs. Even Billy Incardona is overcome.

If only the CB contact point and speed matter, why are all these highly experienced players (like Mika and Billy--and Jim Wych) so blown away by the extent of the draw?

One reason is that he really doesn't even seem to hit the ball that hard. Looking at the time the CB takes to travel to the OB, it would look to me about HALF the speed of a break shot.

It's these types of shots that create the idea of "superstroke."

Did someone say "superstroke?" (inside joke for some here.)

Here's my thought about superstroke: sometimes, something almost magical happens on a pool table. The cue ball moves in wondeous ways; the object balls make a different sound; your cue feels alive and you can almost feel the cue ball on your tip, right through five feet of wood, up into your arm, brain, and soul.

When I'm playing well, I feel like I can go through the cue ball at all different kinds of angles, with all kinds of different motions, at a wide variety of speeds. I truly believe the expression, "How'd he dab that one?!" is more expressive and insightful that most folks understand. Because that's what I feel when I'm running racks: I'm "dabbing" the ball -- not stroking it. It's like being in front of a canvas and creating something beyond the scientific formulas

Sometimes, it's almost hard to keep from overdrawing the ball with hardly any effort or speed. (Other times, the cue ball seems like it's made of lead.) I have my own set of balls and usually practice on the same table, so I don't subscribe to the idea of this being equipment related. And, I'm usually pretty methodical about setting up,so I also don't subscribe to this being an issue of how low you hit the ball. So what's left?

Here's my own personal pet theory, which to a certain extent, I've tested out: I think on some days my grip is slightly cocked to the rear. As you sit at your computer, hold your grip hand down as if holding a cue. Now, if you're a right-hander, rotate it slightly counterclockwise. Now compare the wrist action between the two. When you cock your wrist, the action, at least for me, becomes much more fluid, faster, and feels more powerful. I think this wrist position, perhaps with some additional elements related to how tight or loose the grip is, how far back the wrist is cocked, and maybe how much elevation is created, combine for the "superstoke" effect, for Lou. Somehow the delivery is altered and whether it's tip speed, contact time, or whatever, there's a significant difference in what happens on the table. The trick then becomes creating this effect and sustaining maximum accuracy.

I'm not quite there yet, but I be trying.

Lou Figueroa

 

[GetMeThere]

Lou,

I know exactly what you're saying about the feel of hitting. Sometimes you feel "the life" in your arm, and it transmits beautifully to CB action (usually in draw), and sometimes you know the hit is going to feel like lead--and all the life comes out of CB response.

But I'm not a believer in magic--and I don't think you are, either.

Maybe there's a special "sweet spot" in draw that's not well understood. I admit being surprised by reading on Dr. Dave's site that the difference in non-over-spinning topspin vs over-spinning topspin, amounts to a 0.05 inch difference in where the CB is hit. Maybe there's a similar extremely small area in draw, where 0.05 inches up or down results in vastly less efficient draw response.

I don't like to argue with physics--but I can't deny very strong perceptions, either.

The question can be settled with a super-precise jig that allows movement of the cue to hit the CB with precision down to 0.01", and a "cue-driver" that allows for the application of various precisely controlled velocities and accelerations. One could then discover if there is a "super draw spot" to be hit--and/or just see under what conditions "superstroke" occurs.

EDIT: You mention the sound of the OBs is different. For me it's the sound of the tip hitting the CB. When things are working "just right," IMO, my hit sound is different than when things are "just normal." Perhaps I should record the sounds and look at them on the oscilloscope...Certainly a difference in sound would be the one physical effect it would be possible for a human to detect, in terms of differences in tip contact time.

 

[Bob Jewett]

Sorry, I just can't easily accept the notion that a FIFTY PERCENT change in a physical parameter can have virtually no effect. It's a huge difference. ...

Unless you study the interaction, it's impossible for you to tell which factors are important. For a center-ball hit, taking a cue stick weight from 20 ounces to 200 ounces and keeping the stick speed the same only increases the speed of the cue ball by 29%, from 150% of the stick speed to about 194% of the stick speed. It may seem strange that the ball ends up going faster than the stick and that the speed change is only 29% for a 900% increase in stick weight, but that's the way the physics works.

For the same shot with just the 20-ounce stick, if you make the tip "softer" (that is, with a smaller spring constant), by a factor of 2, you increase the contact time by a factor of about 1.414 but do not change the speed of the cue ball at all*. That's really counterintuitive for many, but that's what physics and measurement say.

* There are some minor effects when you look closely, such as typical tips that lose about 20% of the expected energy transfer, and a correction for the fact that the tip's surface is round rather than flat, but those are also mostly understood and reasonably well modeled.

 

[dr_dave]

...Neither the bridge hand nor grip hand can have a significant effect during the extremely small tip contact times. 1.2ms is very different from 0.8ms, but they are both extremely small in relation to the response of human flesh.

I agree completely that the human nervous system can't do ANYTHING on that time frame

If I'm not mistaken, Dave was thinking of the way soft flesh yields upon tip/ball contact and is therefore unable to affect tip/ball interaction. The hand is effectively "uncoupled" from the stick during contact.

Bingo!

Actually, the flesh doesn't necessarily yield "upon tip/ball contact." The bridge hand flesh doesn't yield until a transverse elastic wave travels from the tip to the bridge after cue tip impact ... or during, if the bridge is within about 6 inches of the tip (for more info, see shaft endmass and stiffness effects). But even if the bridge is close to the tip (which usually isn't the case), it takes time for the fingers to flex and generate force, and it takes time for that force to be "felt" by the tip. The CB will be long gone by the time this happens.

The grip hand does not generate much force until the cue slows and the hand moves forward enough (due to its momentum) to create enough skin flex. Again, the CB is long gone by the time this happens.

Bottom line: The CB is long gone before any "flesh effects" can be "felt" by the tip.

Regards,
Dave

 

[dr_dave]

... I'd settle for an answer to the simple question: If a tip hits a CB at point X, with speed Y, from angle Z, and the contact lasts for 1.2 ms, then what changes in the outcome when X, Y, and Z happen and the contact lasts for 0.8 ms?

Physics says that essentially nothing changes for that change in contact time. If you're using side spin, there will be slightly more squirt, slightly more spin, and slightly less speed, but you could get the same difference pretty much by hitting slightly farther off center. In general, it's a bad idea to prolong the contact time.

One thing that does changes is: The peak force isn't as large with a longer contact time (i.e., the force is spread out over a longer time). Therefore, the "hit" might "feel" slightly different to the player. However, the momentum effects (cue and ball speed changes) will still be the same, assuming the tips being compared have the same efficiency. Another thing that might be different is that a shorter contact time is usually associated with a harder tip, and a harder tip might have better efficiency, so the CB might have slightly more speed for a given cue mass and speed. For more info and resources (including videos) on these topics, see:

tip contact time
tip hardness effects
cue tip efficiency
cue "hit," "feel" and "playability​

Regards,
Dave

 

[u12armresl]

No one in Kokomo can play anyway, so don't worry.

I used a LD shaft when I only played 9ball or 8ball (predator and OB1). I decided Id rather just stay with good regular shafts, but its always in my head that maybe I shot a little better with the LD shafts. There are a few people around here that cant stand the idea of using a LD shaft for one-hole, but I cant for the life of me figure out why??? The only reason I can think of is maybe, and I mean maybe, there are a small amount of shots where the deflection might help whitey get outta the way doin some cross banks. Anyone have any ideas why a LD shaft might be bad for one-hole? Or why it might be good? Or a guess about any of it? lol.


Joe

 

[GetMeThere]

Bob and Dave,

Those are excellent answers. But they don't address exactly the issues I'm interested in, which involve these:

1) Does anyone possess enough contact time data, under different speed variations, and with precise enough time measurements, to allow correlation of the variations in contact time to some pre-shot parameter--like variations in cue velocity? Something a bit stronger than (paraphrasing here): Faster shots have shorter contact times? IOW, is there a clear, substantiated explanation for the variation in contact time data now in your possession?

[Part of my problem may be that I'm unaware what data is really out there. Sometimes I suspect that maybe you two guys (in particular) have data you haven't made public. I have the impression that maybe not too much data is in ANYBODY'S hands--maybe I'm wrong. Does anyone have data from pressure transducers--I get the idea that Dave's statement about peak pressure comes from theory (total area under the pressure curve) rather than experiment (which doesn't mean it's wrong, of course)?]

2) How are people citing contact times beyond 3 sig figs (such as 0.0005) from cameras in the 1000-2000 fps range? What is the accuracy of the data you're using?

3) Any "superstroke" comments or observations? I can hit a CB as hard as the next guy. I can hit a CB as low as the next guy. But I don't think I could say without hesitation that I could step up to the table and produce the draw effect that Corey Deuel did in that video clip any and every time I wanted to. Why can't I? Can you?

I'm not going to be satisfied on the "superstroke" issue until a stroke machine is built to demonstrate that there's no "magic" in stroking. For example, that the same actual pool outcome (e.g., draw of a certain, preferably large, distance) can be achieved by a stroke machine that could produce a given velocity at tip impact BOTH at a point when it was ACcelerating the cue, and DEcelerating the cue around impact.

To Bob: Thanks for the mass variation info. I've wondered about that and wanted an example like that.

 

[JoeyA]

I don't think I can imagine playing one pocket without my OB2 LD shaft.

 

[snipershot]

No one in Kokomo can play anyway, so don't worry.

Ouch! Lol! I can prolly find a couple guys that will challenge you, hehehe.


Joe

 

[lfigueroa]

Lou,

I know exactly what you're saying about the feel of hitting. Sometimes you feel "the life" in your arm, and it transmits beautifully to CB action (usually in draw), and sometimes you know the hit is going to feel like lead--and all the life comes out of CB response.

But I'm not a believer in magic--and I don't think you are, either.

Maybe there's a special "sweet spot" in draw that's not well understood. I admit being surprised by reading on Dr. Dave's site that the difference in non-over-spinning topspin vs over-spinning topspin, amounts to a 0.05 inch difference in where the CB is hit. Maybe there's a similar extremely small area in draw, where 0.05 inches up or down results in vastly less efficient draw response.

I don't like to argue with physics--but I can't deny very strong perceptions, either.

The question can be settled with a super-precise jig that allows movement of the cue to hit the CB with precision down to 0.01", and a "cue-driver" that allows for the application of various precisely controlled velocities and accelerations. One could then discover if there is a "super draw spot" to be hit--and/or just see under what conditions "superstroke" occurs.

EDIT: You mention the sound of the OBs is different. For me it's the sound of the tip hitting the CB. When things are working "just right," IMO, my hit sound is different than when things are "just normal." Perhaps I should record the sounds and look at them on the oscilloscope...Certainly a difference in sound would be the one physical effect it would be possible for a human to detect, in terms of differences in tip contact time.

No, of course I'm not into the voodoo, GMT -- I leave all that to the tin foil hat crowd

I think it is contact time, cue tip speed (as a result of delivery) the path the cue tip takes through the ball AND, the height of the tip. At least in some of the high speed video I've seen the tip moves sideways a fair amount and I'm thinking maybe a thinner tip doesn't displace as much and that there may be something there. (Have I covered the water front?) There's something going on, that would adhere to the laws of physics, but which we just haven't figured out yet.

And oh yeah, if you've been around the game long enough, you hear the game differently that those who have not. It's like being able to distinguish the nuances of a fine wine or a good cigar.

Lou Figueroa