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dr_dave
11-01-2007, 10:38 AM
FYI, my November '07 BD article (http://billiards.colostate.edu/bd_articles/2007/nov07.pdf) explains and illustrates back-hand English (BHE), front-hand English (FHE), a cue's natural pivot length, and advice for selecting a break cue and bridge distance. The article also presents a simple procedure for measuring the natural pivot length for a cue. None of this information is really new, but I don't think it is widely known and completely understood.

I used the procedure described in the article (http://billiards.colostate.edu/bd_articles/2007/nov07.pdf) to experimentally measure the natural pivot lengths for various cues, and here is what I got:

- Predator Z, 19 oz, 11.85 mm tip: 20.2 inches

- Players XIX, 21 oz, 12.75 mm tip: 12.7 inches

- Stinger break/jump cue, 13.5 mm tip: 9.2 inches

As you can see, the natural pivot length can vary quite a lot among different cues.

I also recently posted an analysis that uses physics and math to predict the natural pivot length for a cue. It can be found in TP B.1 (http://billiards.colostate.edu/technical_proofs/new/TP_B-1.pdf). The results agree quite closely with my experimental results.

Other conclusions supported by the analysis include:

- Squirt angle varies nearly linearly with tip offset, and tip offset varies nearly linearly with cue pivot angle. This is what makes the BHE and FHE methods effective, provided swerve and throw are also taken into consideration.

- A cue's natural pivot length does vary a little with both tip offset and tip shape (radius), so when comparing different cues with experimental measurements, it is important to use the same tip shape and the same amount of tip offset (English) for each cue.

- Cue pivot lengths reported by Platinum Billiards (https://www.platinumbilliards.com/rating_deflect.php) seem to be too low. They report a range from 8 inches (for a "high-squirt" cue) to 14 inches (for a "low-squirt" cue).

- Expected cue pivot lengths reported in Ron Shepard's 2001 paper "Everything you Always Wanted to Know About Cue Ball Squirt, but Were Afraid to Ask (http://billiards.colostate.edu/physics/Shepard_squirt.pdf)" appear to be too high. He reports a range from 10 inches (for a "high-squirt" cue) to 50 inches (for a "low-squirt" cue).

The last two bullets are the main reason for my posting. My experimental and theoretical values seem to agree quite closely, but values reported by others differ and I don't know why. I am hoping many of you out there will be willing to try the experiment in the article (http://billiards.colostate.edu/bd_articles/2007/nov07.pdf) to measure the natural pivot lengths for various cues. The experiment doesn't take very long, and you might even learn something in the process. If you do perform the experiment, please share your results here. I (and I hope others) would like to see what different people report for a wide range of cues.

Thank you in advance for your participation.

Regards,
Dave

Cornerman
11-01-2007, 12:06 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> My experimental and theoretical values seem to agree quite closely, but values reported by others differ and I don't know why. <hr /></blockquote>Does Spin-Induced Throw make the practical pivot point longer?

I think the center-of-the-cueball privot point only represents the ghost ball geometrical aiming, which would be a much shorter pivot point.

Fred

dr_dave
11-01-2007, 01:13 PM
<blockquote><font class="small">Quote Cornerman:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> My experimental and theoretical values seem to agree quite closely, but values reported by others differ and I don't know why. <hr /></blockquote>Does Spin-Induced Throw make the practical pivot point longer?<hr /></blockquote>Yes. Looking at Diagram 3 in the article (http://billiards.colostate.edu/bd_articles/2007/nov07.pdf), SIT would tend to send the OB more in the "A" direction (in the direction of the spin). This would required a lenghtening of the bridge distance to compensate back to the "B" (center-line) direction, where the squirt would now cancel the combination of the smaller pivot angle and the SIT. Platinum's reported lengths are shorter than mine; however, I'm pretty convinced throw was not much of a factor in my experiment, because I sprayed and wiped the balls with Silicone spray first. This practically eliminates all swerve and throw effects. I also used fast speed with a fairly large tip offset, which further reduces SIT effects.

Here's a quote from the article that people might want to keep in mind when they perform the experiment:

<blockquote><font class="small">Quote article:</font><hr>To get the best measurement, you need to make sure throw does not corrupt your results. With spin-induced throw (SIT), the OB would go off course a little when the CB heads straight up the centerline. To limit this effect, you can wet the contact area on the OB (e.g., with spit on your finger) to reduce friction. An even better solution is to spray and wipe the balls with silicone spray. This will dramatically reduce friction between the balls and between the CB and the cloth to mostly eliminate the effects of both throw and swerve. If you plan to use silicone spray, consider using spare balls (i.e., not balls from your normal playing set). You wouldn’t want one or two slicked-up balls in your set that will play differently from the rest. Faster speed also reduces the effects of both throw and swerve. Referring to case “B” in Diagram 3, using fast speed and silicone-sprayed balls with the bridge at the natural pivot distance, the CB should stop in place spinning and the OB should head perfectly straight up table and rebound straight back to the CB (assuming the table is level).<hr /></blockquote>

Silicone spray is available at local hardware stores if people want to try it out. Otherwise, just stick with the spit.

Regards,
Dave

PS: If you perform any tests, please share your results. I know you probably have a zillion cues.

dr_dave
11-01-2007, 01:21 PM
<blockquote><font class="small">Quote Cornerman:</font><hr>I think the center-of-the-cueball privot point only represents the ghost ball geometrical aiming, which would be a much shorter pivot point.<hr /></blockquote>Fred,

I'm not exactly sure what you mean here. As the diagrams in the article (http://billiards.colostate.edu/bd_articles/2007/nov07.pdf) show, I define the "pivot length" as the bridge distance. So when the bridge is at the natural pivot point of the cue, the distance from the bridge to the front of the CB is the natural pivot length. This is consistent with Shepard's definition. I'm not sure how Platinum defines it, but I can't imagine why they might define it differently.

I'm sorry if I misunderstood you comment. If I did, please try to explain it again (maybe referring to diagrams in the article).

Thanks,
Dave

cushioncrawler
11-01-2007, 07:23 PM
Dr Dave -- The difference in slipperyness of the bedcloth would of course be one reason for different figures by others. And any difference in the jacked-up angle.

I guess that most of us have a natural hoik to the left or right (ie we dont cue straight). Hencely we will have a different pivot length for left and right.

Perhaps, too, there might be 2 types of pivot-length. The common type (Type 1) iz where we want to put sidespin on the qball. Here i guess we aim for the correct contact on the OB while lining up centrally on the qball, then, we pivot the qtip over (uzing BHP or uzing FHP) to get the desired spin.

But, i am thinking of Type 2, where we are aiming centraly throo the qball, and stroking centraly throo the qball (or at least wanting to stroke centraly), with zero sidespin. I will look into Type 2 in 2008. madMac.

Jal
11-01-2007, 08:01 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> So when the bridge is at the natural pivot point of the cue, the distance from the bridge to the front of the CB is the natural pivot length. This is consistent with Shepard's definition. I'm not sure how Platinum defines it, but I can't imagine why they might define it differently.<hr /></blockquote>Dr. Dave, Platinum's definition is pretty close to yours, I believe. A line drawn along the cueball's squirt direction, while the tip is still in contact with it, intersects the center of the shaft at some point. This is their pivot point. At least, this is consistent with the formula:

PP = b/tan(s) - R

where PP is the pivot point distance from the tip, b is the apparent offset (center of shaft), s is the squirt angle, and R the ball's radius.

This yields the pivot point figures at Platinum's site using tan(s) = (sideways deflection)/50". They may use a correction for the curvature of the ball so that R becomes Sqrt(R^2 - b^2), but the above comes very close.

I assume that you used the trueness of the object ball's direction rather than the cueball spinning in place to indicate a full hit. Post impact masse should send the cueball well off to the side (several inches) after a dead-on collision, unless something funny goes on such as the cueball not being able to lift itself out of the dimple in the cloth.

Have you measured the reduction in ball/ball friction with the spray? I think the coefficient may be considerably larger for normal balls on a full hit than the surface speed calibrations (based on Marlow's tests) would indicate (due to greater normal pressure, this was discussed briefly some time ago). Perhaps the silicone just brings it back down to somthing like you would expect from the Marlow data (for a full hit).

However, I looked over your second article in the squirt series (where Dave Gross assisted) and you found about a 30% reduction in squirt for the Predator Z compared against a Players cue. On the face of it, this appears consistent with Platinum. But, after applying some corrections for the different tip offsets, it looks like they are not consistent after all. (You measured 1.8 degrees of squirt at a .5" offset whereas about 2.6 degrees would be the expected value when extrapolated from Platinum's smaller apparent offset of 9mm and corrected for dime curvature.)

I only bring this up because those results obviously can't be explained away (at least potentially) as per the above.

Perhaps your stroke machine, if it's still in the works, will eventually resolve all of this.

Jim

P.S. I finally obtained a copy of your book and didn't put it down until the wee hours last night. I didn't expect anything less, but it has to be one of the most thorough instructional books ever written on the game (apart from advanced and/or game specific strategy maybe...I'm only a third of the way through). Very much looking forward to the rest of it.

Cornerman
11-02-2007, 05:57 AM
<blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote Cornerman:</font><hr>I think the center-of-the-cueball privot point only represents the ghost ball geometrical aiming, which would be a much shorter pivot point.<hr /></blockquote>Fred,

I'm not exactly sure what you mean here. As the diagrams in the article (http://billiards.colostate.edu/bd_articles/2007/nov07.pdf) show, I define the "pivot length" as the bridge distance. So when the bridge is at the natural pivot point of the cue, the distance from the bridge to the front of the CB is the natural pivot length. This is consistent with Shepard's definition. I'm not sure how Platinum defines it, but I can't imagine why they might define it differently.

I'm sorry if I misunderstood you comment. If I did, please try to explain it again (maybe referring to diagrams in the article).

Thanks,
Dave <hr /></blockquote>It's tough for me to put down into words. At the table, it's obvious.

In your diagram, you have a line called "desired path." Depending on how a player defines "desired path," the squirt pivot point will be different. If the desired path is based solely on a centerball ghostball aim, then the pivot point ... the overall effective pivot point length will be longer than the theoretical pivot point if you want to make the object ball. That's because the cueball can't make the object ball if it actually goes the same path as the centerball aim path. Unless you have tremendously slick conditions (like silicon sprayed cueballs).

If the "desired path" is the true path (and subsequent collision point) that the cueball must take to make the object ball given its spin, then the pivot point will have to be a shorter length if your starting aim is at the true path. That should make obvious sense at the table.


In other words, if the desire is to hit the center of that recently introduced laser aiming target using firm english and only the cueball, then the pivot point is shorter. Those trying to hit that laser target with what they normally know as their pivot point will never hit the target. And now you know why.

If the desire is to pocket a 30 degree cut shot with firm inside english, then the pivot point (the effective pivot point) is longer than that of the laser target pivot point.

Fred &lt;~~~ knows that words cannot describe all the nuances

Cornerman
11-02-2007, 06:00 AM
<blockquote><font class="small">Quote dr_dave:</font><hr> To get the best measurement, you need to make sure throw does not corrupt your results. <hr /></blockquote>For your (Dr. Dave's) purposes, you're right. For practical purposes, you have to make sure that throw does "corrupt" the results. Overly slick cueballs will do more damage to learning about squirt compensation, IMO.

Fred

dr_dave
11-02-2007, 08:48 AM
<blockquote><font class="small">Quote Cornerman:</font><hr>In your diagram, you have a line called "desired path." Depending on how a player defines "desired path," the squirt pivot point will be different.<hr /></blockquote>In my diagrams, I use the label "desired CB direction." To be more clear, I should have used "desired initial CB direction."
<blockquote><font class="small">Quote Cornerman:</font><hr>If the desired path is based solely on a centerball ghostball aim, then the pivot point ... the overall effective pivot point length will be longer than the theoretical pivot point if you want to make the object ball.<hr /></blockquote>If the desire is to have the CB end up a "ghost-ball" target (e.g., the place you want the CB at OB impact to result in the desired OB path, accounting for throw), the desired direction needs to account for swerve. Obviously, the amount of swerve depends on cue elevation, shot speed, shot distance, and ball and cloth conditions. Are you suggesting defining a different pivot point (bridge distance) for every shot and conditions? My purpose here is to identify the single "natural pivot length" for a cue, so various cues can be compared. BHE and FHE with the bridge fixed at the natural pivot length for the cue account only for squirt.

<blockquote><font class="small">Quote Cornerman:</font><hr>That's because the cueball can't make the object ball if it actually goes the same path as the centerball aim path.<hr /></blockquote>Agreed ... the CB does swerve with English.<blockquote><font class="small">Quote Cornerman:</font><hr>Unless you have tremendously slick conditions (like silicon sprayed cueballs).<hr /></blockquote>... and/or fast speed and/or super slick cloth and/or short shot distance and/or near-level cue.

<blockquote><font class="small">Quote Cornerman:</font><hr>If the "desired path" is the true path (and subsequent collision point) that the cueball must take to make the object ball given its spin, then the pivot point will have to be a shorter length if your starting aim is at the true path. That should make obvious sense at the table.<hr /></blockquote>Agreed. Again, I am not indicating the entire path of the CB, only the initial desired direction. Again, the point is to characterize the "natural pivot length" for a cue, not the bridge distance required for using BHE and FHE with different shots based on cue elevation, shot speed, shot distance, and conditions.

<blockquote><font class="small">Quote Cornerman:</font><hr>In other words, if the desire is to hit the center of that recently introduced laser aiming target using firm english and only the cueball, then the pivot point is shorter. Those trying to hit that laser target with what they normally know as their pivot point will never hit the target.<hr /></blockquote>Agreed.<blockquote><font class="small">Quote Cornerman:</font><hr>And now you know why.<hr /></blockquote>Are you suggesting I didn't know this already? If so, I am insulted.

<blockquote><font class="small">Quote Cornerman:</font><hr>If the desire is to pocket a 30 degree cut shot with firm inside english, then the pivot point (the effective pivot point) is longer than that of the laser target pivot point.<hr /></blockquote>Agreed.

<blockquote><font class="small">Quote Cornerman:</font><hr>Fred &lt;~~~ knows that words cannot describe all the nuances<hr /></blockquote>I think you did a pretty good job with your words. I like pictures better (e.g., see Diagram 1 in my May '07 article (http://billiards.colostate.edu/bd_articles/2007/may07.pdf)).

Thank you for your comments,
Dave

PS: If you do any "natural pivot length" tests with your collection of cues, please share your results.

dr_dave
11-02-2007, 08:58 AM
<blockquote><font class="small">Quote Cornerman:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> To get the best measurement, you need to make sure throw does not corrupt your results.<hr /></blockquote>For your (Dr. Dave's) purposes, you're right.<hr /></blockquote>You are correct. My purpose in this article (http://billiards.colostate.edu/bd_articles/2007/nov07.pdf) is to define and identify the "natural pivot length" for a cue. This is a unique value for each cue that helps describe how low-squirt it is. I think this is useful information; and to get good measurements for this, one must be careful to eliminate swerve and throw as factors. The "natural pivot length" for a cue is a measure of a cue's squirt characteristics ... nothing more.

<blockquote><font class="small">Quote Cornerman:</font><hr>For practical purposes, you have to make sure that throw does "corrupt" the results. Overly slick cueballs will do more damage to learning about squirt compensation, IMO.<hr /></blockquote>Agreed. If a person wants to try to use BHE or FHE squirt-compensation techniques, he or she better also be aware of swerve and throw effects, and how these effects vary with the type of shot and the conditions of the balls and cloth. This is why I have dedicated and will continue to dedicate so many of my BD articles (http://billiards.colostate.edu/bd_articles/index.html) to these topics.

Regards,
Dave

dr_dave
11-02-2007, 09:16 AM
<blockquote><font class="small">Quote cushioncrawler:</font><hr>Dr Dave -- The difference in slipperyness of the bedcloth would of course be one reason for different figures by others. And any difference in the jacked-up angle.<hr /></blockquote>Good point. I think Platinum uses Predator's Iron Willey for their tests (but I'm not sure), and I think the cue is elevated. If so, their squirt measurements and pivot point calculations would be corrupted by swerve. Swerve can vary with shot speed, which can vary with the tip type and exact amount of tip offset. Swerve can also vary with ball and cloth conditions, which can vary with cleanliness, humidity, and wear. The best test set-up would be a horizontal cue. Then, swerve would not come into play.

<blockquote><font class="small">Quote cushioncrawler:</font><hr>I guess that most of us have a natural hoik to the left or right (ie we dont cue straight). Hencely we will have a different pivot length for left and right.<hr /></blockquote>Good point. If one wants to use the experiment in the article (http://billiards.colostate.edu/bd_articles/2007/nov07.pdf) to determine the "natural pivot length" for a cue, he or she should probably try the test multiple times with both right and left English to get the best average result.

Thank you for your comments,
Dave

PS: Please report your results if you perform the experiment with any of your cues. I'd be particularly interested in seeing your results for some Snooker cues (and your famous Steel cue!).

dr_dave
11-02-2007, 09:25 AM
<blockquote><font class="small">Quote Jal:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> So when the bridge is at the natural pivot point of the cue, the distance from the bridge to the front of the CB is the natural pivot length. This is consistent with Shepard's definition. I'm not sure how Platinum defines it, but I can't imagine why they might define it differently.<hr /></blockquote>Dr. Dave, Platinum's definition is pretty close to yours, I believe. A line drawn along the cueball's squirt direction, while the tip is still in contact with it, intersects the center of the shaft at some point. This is their pivot point. At least, this is consistent with the formula:

PP = b/tan(s) - R

where PP is the pivot point distance from the tip, b is the apparent offset (center of shaft), s is the squirt angle, and R the ball's radius.

This yields the pivot point figures at Platinum's site using tan(s) = (sideways deflection)/50". They may use a correction for the curvature of the ball so that R becomes Sqrt(R^2 - b^2), but the above comes very close.<hr /></blockquote>Thanks. So they do appear to define the "natural pivot length" the same way I do (or at least close enough). So our numbers should agree better (unless swerve is corrupting their squirt measurements?).

Regards,
Dave

dr_dave
11-02-2007, 09:32 AM
<blockquote><font class="small">Quote Jal:</font><hr>I assume that you used the trueness of the object ball's direction rather than the cueball spinning in place to indicate a full hit.<hr /></blockquote>In the article (http://billiards.colostate.edu/bd_articles/2007/nov07.pdf), I recommend using the OB path as the indicator (see path "B" in Diagram 3). But as I point out, this brings throw into the measurement. That's why I suggest the silicone spray, faster speed, and more English. These factors reduce the effects of spin-induced throw.

<blockquote><font class="small">Quote Jal:</font><hr>Post impact masse should send the cueball well off to the side (several inches) after a dead-on collision, unless something funny goes on such as the cueball not being able to lift itself out of the dimple in the cloth.<hr /></blockquote>I'm not sure what you mean by "post-impact masse;" but with the silicone spray, fast speed, and large tip offset, the CB didn't move very much for me with a straight OB path.

Regards,
Dave

dr_dave
11-02-2007, 09:41 AM
<blockquote><font class="small">Quote Jal:</font><hr>Have you measured the reduction in ball/ball friction with the spray? I think the coefficient may be considerably larger for normal balls on a full hit than the surface speed calibrations (based on Marlow's tests) would indicate (due to greater normal pressure, this was discussed briefly some time ago). Perhaps the silicone just brings it back down to somthing like you would expect from the Marlow data (for a full hit).<hr /></blockquote>I have not tested this. When I get some time, I'll try to repeat the experiments described in my September '06 article (http://billiards.colostate.edu/bd_articles/2006/sept06.pdf) with the balls sprayed and wiped with silicone. I'll be sure to share the results if I do the experiment.

One thing that is very noticeable with the silicone spray is how much it reduces the friction between the balls and the cloth. When I performed the squirt experiments reported in my September '07 article (http://billiards.colostate.edu/bd_articles/2007/sept07.pdf), the silicone spray pretty much totally eliminated swerve as a factor (over short distances). Also, masse shots and power draw shots are dramatically easier with the silicone spray. I wish I had known this when I was trying to film some of the video demos for my website many years ago.

Regards,
Dave

dr_dave
11-02-2007, 09:47 AM
<blockquote><font class="small">Quote Jal:</font><hr>... I looked over your second article in the squirt series (where Dave Gross assisted) and you found about a 30% reduction in squirt for the Predator Z compared against a Players cue. On the face of it, this appears consistent with Platinum. But, after applying some corrections for the different tip offsets, it looks like they are not consistent after all. (You measured 1.8 degrees of squirt at a .5" offset whereas about 2.6 degrees would be the expected value when extrapolated from Platinum's smaller apparent offset of 9mm and corrected for dime curvature.)

I only bring this up because those results obviously can't be explained away (at least potentially) as per the above.

Perhaps your stroke machine, if it's still in the works, will eventually resolve all of this.<hr /></blockquote>We actually hope to generate some useful data with our cue-testing machine over the next month. I will publish these results in an upcoming article. We keep the cue perfectly level and only look at CB motion, so swerve and throw will not be factors (i.e., the squirt measurements will not be "corrupted").

Regards,
Dave

Cornerman
11-02-2007, 10:13 AM
<blockquote><font class="small">Quote dr_dave:</font><hr>
<blockquote><font class="small">Quote Cornerman:</font><hr>If the desired path is based solely on a centerball ghostball aim, then the pivot point ... the overall effective pivot point length will be longer than the theoretical pivot point if you want to make the object ball.<hr /></blockquote>If the desire is to have the CB end up a "ghost-ball" target (e.g., the place you want the CB at OB impact to result in the desired OB path, accounting for throw), the desired direction needs to account for swerve. <hr /></blockquote>
I'm not even discussing swerve at this point. Normally, when we do aim-and-pivot testing, we shoot so that swerve isn't part of the equation. So, forget about swerve for a moment and pretend it isn't allowed to exist. The discussion of swerve for this purpose doesn't add value.

This has already gotten more complicated in describing it on the screen. Bottom line: two different pivot points: one to get the cueball to hit the laser target, and the other to pocket the ball due to spin throw (forgetting completely about swerve). Therefore, two different tests should be acknowledged.

The Aim-and-Pivot Method is test #2 (with object ball).


<blockquote><font class="small">Quote Dr. Dave:</font><hr>
<blockquote><font class="small">Quote Cornerman:</font><hr>In other words, if the desire is to hit the center of that recently introduced laser aiming target using firm english and only the cueball, then the pivot point is shorter. Those trying to hit that laser target with what they normally know as their pivot point will never hit the target.<hr /></blockquote>Agreed.<blockquote><font class="small">Quote Cornerman:</font><hr>And now you know why.<hr /></blockquote>Are you suggesting I didn't know this already? If so, I am insulted.<hr /></blockquote> I was obviously talking about those who are trying to use their effective pivot point to try and hit that laser target and miss.

And to that point, I have no idea if you know, Dave. I figured you didn't know since you were asking about why people are getting the vastly different measurements that people were getting for pivot points. And I was answering one of the distinct reasons.

This was a VERY important distinction I was making that hopefully you didn't effectively sweep under the rug.

I thought for sure it was you (see below) who was asking why there were different results for pivot point measurements. I have some answers. Surely you wanted answers and weren't asking rhetorically?


<blockquote><font class="small">Quote dr_dave:</font><hr>

My experimental and theoretical values seem to agree quite closely, but values reported by others differ and I don't know why. <hr /></blockquote>
Fred

dr_dave
11-02-2007, 10:43 AM
Fred,

I'm sorry I misinterpreted your statements. Thank you for clarifying.

Thank you also for suggesting possible sources of discrepancies with reported data.

I have done tests both with and without an OB. In TP B.1 (http://billiards.colostate.edu/technical_proofs/new/TP_B-1.pdf), I calculate pivot lengths based on direct squirt angle measurements (from data presented in my September '07 article (http://billiards.colostate.edu/bd_articles/2007/sept07.pdf)). In my November '07 article (http://billiards.colostate.edu/bd_articles/2007/nov07.pdf) I describe and illustrate a simple experiment for measuring the "natural pivot length" directly. As I point out in my original post, my direct experiment numbers match the calculated results fairly well. That is because I did what I could to reduce the effects of throw. Platinum Billiards does not use an OB, so throw is not part of their measurements either (although, their results might be "corrupted" by swerve).

It seems like you are suggesting defining a different "pivot length" that adjusts for the effects of both squirt and throw. Sorry I misunderstood before. But doesn't throw vary with cut angle, speed, amount and type of spin, ball conditions, etc? So this "pivot length" would not be a good measure for comparing different cues ... right?

Regards,
Dave

<blockquote><font class="small">Quote Cornerman:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr>
<blockquote><font class="small">Quote Cornerman:</font><hr>If the desired path is based solely on a centerball ghostball aim, then the pivot point ... the overall effective pivot point length will be longer than the theoretical pivot point if you want to make the object ball.<hr /></blockquote>If the desire is to have the CB end up a "ghost-ball" target (e.g., the place you want the CB at OB impact to result in the desired OB path, accounting for throw), the desired direction needs to account for swerve. <hr /></blockquote>
I'm not even discussing swerve at this point. Normally, when we do aim-and-pivot testing, we shoot so that swerve isn't part of the equation. So, forget about swerve for a moment and pretend it isn't allowed to exist. The discussion of swerve for this purpose doesn't add value.

This has already gotten more complicated in describing it on the screen. Bottom line: two different pivot points: one to get the cueball to hit the laser target, and the other to pocket the ball due to spin throw (forgetting completely about swerve). Therefore, two different tests should be acknowledged.

The Aim-and-Pivot Method is test #2 (with object ball).


<blockquote><font class="small">Quote Dr. Dave:</font><hr>
<blockquote><font class="small">Quote Cornerman:</font><hr>In other words, if the desire is to hit the center of that recently introduced laser aiming target using firm english and only the cueball, then the pivot point is shorter. Those trying to hit that laser target with what they normally know as their pivot point will never hit the target.<hr /></blockquote>Agreed.<blockquote><font class="small">Quote Cornerman:</font><hr>And now you know why.<hr /></blockquote>Are you suggesting I didn't know this already? If so, I am insulted.<hr /></blockquote> I was obviously talking about those who are trying to use their effective pivot point to try and hit that laser target and miss.

And to that point, I have no idea if you know, Dave. I figured you didn't know since you were asking about why people are getting the vastly different measurements that people were getting for pivot points. And I was answering one of the distinct reasons.

This was a VERY important distinction I was making that hopefully you didn't effectively sweep under the rug.

I thought for sure it was you (see below) who was asking why there were different results for pivot point measurements. I have some answers. Surely you wanted answers and weren't asking rhetorically?


<blockquote><font class="small">Quote dr_dave:</font><hr>

My experimental and theoretical values seem to agree quite closely, but values reported by others differ and I don't know why. <hr /></blockquote>
Fred<hr /></blockquote>

Jal
11-02-2007, 11:18 AM
<blockquote><font class="small">Quote dr_dave:</font><hr>....So they do appear to define the "natural pivot length" the same way I do (or at least close enough). So our numbers should agree better (unless swerve is corrupting their squirt measurements?).<hr /></blockquote>Dr. Dave, I know you know of course (and know this a thousand times over /ccboard/images/graemlins/smile.gif), but to the extent that swerve is corrupting their results, it should be reducing the apparent squirt, not increasing it.

<blockquote><font class="small">Quote dr_dave:</font><hr><blockquote><font class="small">Quote Jal:</font><hr>Post impact masse should send the cueball well off to the side (several inches) after a dead-on collision, unless something funny goes on such as the cueball not being able to lift itself out of the dimple in the cloth.<hr /></blockquote>I'm not sure what you mean by "post-impact masse;" but with the silicone spray, fast speed, and large tip offset, the CB didn't move very much for me with a straight OB path.<hr /></blockquote>It's been a while and I'd have to re-do the calculations, but with a cue elevation of something between 3 and 5 degrees and a very hard hit (say a cueball speed of 10 mph or so), and a large tip offset, the numbers indicate that the cueball should move over to the side as much as 6" after a perfectly square hit. This is with undoctored balls. Slicked up balls should move even more. In eliminating pre-impact swerve through shot speed and the close proximity of the balls, it should come out the other end as post-impact swerve. In other words, the tilted z-axis spin component is still there.

But perhaps the cueball's footprint (cloth dimple) suppresses this somewhat, along with the z-axis spin interaction with the cloth's normal rolling resistance, which acts at right angles to the ball's direction of travel. I haven't tried to account for these yet.

If post-impact swerve isn't suppressed very much by these, then it should corrupt the aim-and-pivot squirt test far more than throw if one judges a full hit simply by the "cueball spinning in place" criteria. That is, the pivot point adjustment to get it to more or less spin in place, rather than moving off to the side, will yield a much larger pivot point distance from the tip.

But even this doesn't explain the very lengthy pivot points measured by some.

Jim

dr_dave
11-02-2007, 12:04 PM
<blockquote><font class="small">Quote Jal:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr>....So they do appear to define the "natural pivot length" the same way I do (or at least close enough). So our numbers should agree better (unless swerve is corrupting their squirt measurements?).<hr /></blockquote>Dr. Dave, I know you know of course (and know this a thousand times over /ccboard/images/graemlins/smile.gif), but to the extent that swerve is corrupting their results, it should be reducing the apparent squirt, not increasing it.<hr /></blockquote>Actually, I was not thinking this all of the way through when I wrote my message. Thank you for pointing this out. You are right ... with squirt angles effectively reduced by swerve, Platinum Billiards' pivot lengths should be larger than mine, not smaller!

Does anybody out there know why Platinums pivot length values are so low?

Thanks,
Dave

dr_dave
11-02-2007, 12:14 PM
<blockquote><font class="small">Quote Jal:</font><hr>It's been a while and I'd have to re-do the calculations, but with a cue elevation of something between 3 and 5 degrees and a very hard hit (say a cueball speed of 10 mph or so), and a large tip offset, the numbers indicate that the cueball should move over to the side as much as 6" after a perfectly square hit. This is with undoctored balls. Slicked up balls should move even more. In eliminating pre-impact swerve through shot speed and the close proximity of the balls, it should come out the other end as post-impact swerve. In other words, the tilted z-axis spin component is still there.

But perhaps the cueball's footprint (cloth dimple) suppresses this somewhat, along with the z-axis spin interaction with the cloth's normal rolling resistance, which acts at right angles to the ball's direction of travel. I haven't tried to account for these yet.

If post-impact swerve isn't suppressed very much by these, then it should corrupt the aim-and-pivot squirt test far more than throw if one judges a full hit simply by the "cueball spinning in place" criteria. That is, the pivot point adjustment to get it to more or less spin in place, rather than moving off to the side, will yield a much larger pivot point distance from the tip.

But even this doesn't explain the very lengthy pivot points measured by some.<hr /></blockquote>Thank you for these observations.

Returning back to Platinum Billiards' data. In their tests, they aren't hitting an OB with the CB. They are measuring the CB deflection and calculating the squirt angle (corrupted by swerve) directly. There is no throw. Also, for my pivot lengths calculated directly from measured squirt angles, I was also not hitting an OB. I was using the high-speed camera to measure the CB squirt angle shortly after tip impact.

With a level-cue cue-testing machine, measuring CB deflection or squirt directly, neither swerve nor throw comes into the picture.

Regards,
Dave

Cornerman
11-02-2007, 01:07 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> It seems like you are suggesting defining a different "pivot length" that adjusts for the effects of both squirt and throw. <hr /></blockquote>

Yes, that's exactly what I'm suggesting. I look at it from the point of actually using the pivot point in every day shooting. So, if I know what my effective swerve-free pivot point is, I can make adjustement from there.

The "true pivot point" is only useful if there's no object ball in the equation. Like shooting to hit a spot (laser target), or shooting the cueball between a couple of other balls.



[ QUOTE ]
But doesn't throw vary with cut angle, speed, amount and type of spin, ball conditions, etc? So this "pivot length" would not be a good measure for comparing different cues ... right?<hr /></blockquote> Yes, but from the Aim-and-Pivot standpoint, you're just testing a straight in shot to begin with. How someone uses this valuable information is up to the user. Adjustments for cut angle and speed make more sense when a baseline is defined. And the straight in object ball with Aim-and-Pivot defines the baseline.

Fred

dr_dave
11-02-2007, 01:37 PM
<blockquote><font class="small">Quote Cornerman:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> It seems like you are suggesting defining a different "pivot length" that adjusts for the effects of both squirt and throw.<hr /></blockquote>
Yes, that's exactly what I'm suggesting. I look at it from the point of actually using the pivot point in every day shooting. So, if I know what my effective swerve-free pivot point is, I can make adjustement from there.

The "true pivot point" is only useful if there's no object ball in the equation. Like shooting to hit a spot (laser target), or shooting the cueball between a couple of other balls.<hr /></blockquote>Other shots where a squirt-only pivot point might be appropriate include the break shot and rail shots.

<blockquote><font class="small">Quote Cornerman:</font><hr><blockquote><font class="small">Quote dr_dave:</font><hr>But doesn't throw vary with cut angle, speed, amount and type of spin, ball conditions, etc? So this "pivot length" would not be a good measure for comparing different cues ... right?<hr /></blockquote> Yes, but from the Aim-and-Pivot standpoint, you're just testing a straight in shot to begin with. How someone uses this valuable information is up to the user. Adjustments for cut angle and speed make more sense when a baseline is defined. And the straight in object ball with Aim-and-Pivot defines the baseline.<hr /></blockquote>Good description. I still think I prefer the squirt-only baseline since swerve and throw are so shot-specific. Squirt is a function of the cue stick only. It doesn't depend on ball or cloth conditions. Also, squirt varies nearly linearly with the amount of cue pivot angle, and squirt angle is independent of shot speed. This is why BHE and FHE are effective tools for squirt compensation. Swerve and throw are not as well behaved or consistent with shot type and equipment conditions. But you've convinced me to try out the squirt/throw pivot point test for various types of shots to see how well it works.

Thanks,
Dave

SpiderMan
11-02-2007, 01:49 PM
I've always questioned the Platinum results, which indicate very little difference between cues. I imagine their test methodology may be flawed.

SpiderMan

Jal
11-02-2007, 02:01 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote Jal:</font><hr>It's been a while and I'd have to re-do the calculations, but with a cue elevation of something between 3 and 5 degrees and a very hard hit (say a cueball speed of 10 mph or so), and a large tip offset, the numbers indicate that the cueball should move over to the side as much as 6" after a perfectly square hit. This is with undoctored balls. Slicked up balls should move even more. In eliminating pre-impact swerve through shot speed and the close proximity of the balls, it should come out the other end as post-impact swerve. In other words, the tilted z-axis spin component is still there.

But perhaps the cueball's footprint (cloth dimple) suppresses this somewhat, along with the z-axis spin interaction with the cloth's normal rolling resistance, which acts at right angles to the ball's direction of travel. I haven't tried to account for these yet.

If post-impact swerve isn't suppressed very much by these, then it should corrupt the aim-and-pivot squirt test far more than throw if one judges a full hit simply by the "cueball spinning in place" criteria. That is, the pivot point adjustment to get it to more or less spin in place, rather than moving off to the side, will yield a much larger pivot point distance from the tip.

But even this doesn't explain the very lengthy pivot points measured by some.<hr /></blockquote>Thank you for these observations.

Returning back to Platinum Billiards' data. In their tests, they aren't hitting an OB with the CB. They are measuring the CB deflection and calculating the squirt angle (corrupted by swerve) directly. There is no throw. Also, for my pivot lengths calculated directly from measured squirt angles, I was also not hitting an OB. I was using the high-speed camera to measure the CB squirt angle shortly after tip impact.<hr /></blockquote>Yes, the post-impact swerve thing is irrelevant for Platinum's tests and your earlier ones with Dave Gross. It's also irrelevant for aim-and-pivot if one ignores the cueball and only judges a full hit according to the direction of the object ball.

My tendency is to believe in Platinum's results. I also know of at least one other who obtained similar numbers for a Predator shaft, and seemed to know what he was doing. But I also believe in yours as well and thought that they were in line with Platinum's until that recent unpleasentness with the offset correction mentioned earlier. What to do?

(I've measured my own cue's pivot point at about 18", with two different methods. Although a Sportmart special, this makes it less squirty than the Predators, if Platinum is right. But I was using "cueball spinning in place" for the aim-and-pivot version. I need to try it again in light of what's been said.)

Jim

SpiderMan
11-02-2007, 02:02 PM
Dave,

I like that article, and the illustrations are also very clear, but I'd like to make a suggestion. In order to be more practical, I think you should mention the impact of different cueballs on the pivot point.

The pivot point is not an intrinsic characteristic of the cue, it is more a characteristic of the cue/cueball interaction. Using the same cue, a red-circle cueball will indicate a pivot point that is shorter than for a mudball. This is one way bar players (using BHE) get stung on regular tables.

In order to effectively use pivot compensation, you have to be aware of this and use the pivot point that corresponds to the combination of cue and cueball being used.

SpiderMan

SpiderMan
11-02-2007, 02:13 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> Squirt is a function of the cue stick only. It doesn't depend on ball or cloth conditions. Thanks,
Dave <hr /></blockquote>

Dave,

I don't want to hijact your ongoing discussion with Fred, but I think the above is over-simplified - at least if you allow "ball conditions" to include "type of ball".

I made some "ball effect" comments beneath your original post.

SpiderMan

dr_dave
11-02-2007, 02:13 PM
<blockquote><font class="small">Quote Jal:</font><hr>My tendency is to believe in Platinum's results.<hr /></blockquote>Why? Dont' you trust me anymore? /ccboard/images/graemlins/mad.gif

(just kidding /ccboard/images/graemlins/wink.gif )

<blockquote><font class="small">Quote Jal:</font><hr>I also know of at least one other who obtained similar numbers for a Predator shaft, and seemed to know what he was doing.<hr /></blockquote>Similar to my numbers or similar to Platinum Billiards' numbers? They are quite different.

<blockquote><font class="small">Quote Jal:</font><hr>... until that recent unpleasentness with the offset correction mentioned earlier. What to do?<hr /></blockquote>
See TP B.1 (http://billiards.colostate.edu/technical_proofs/new/TP_B-1.pdf). I define the pivot length in the center-ball aim position, and then I do the trig and geometry to relate measured squirt angles and offsets to this definition. No approximations are made.

<blockquote><font class="small">Quote Jal:</font><hr>(I've measured my own cue's pivot point at about 18", with two different methods. Although a Sportmart special, this makes it less squirty than the Predators, if Platinum is right. But I was using "cueball spinning in place" for the aim-and-pivot version. I need to try it again in light of what's been said.)<hr /></blockquote>Thank you, and congratulations. You are the first person to share results here. I was hoping lot's of people would be interested in doing the simple experiment. I still hope they do, so they can share their results and observations.

Regards,
Dave

dr_dave
11-02-2007, 02:41 PM
<blockquote><font class="small">Quote SpiderMan:</font><hr> Dave,

I like that article, and the illustrations are also very clear, but I'd like to make a suggestion. In order to be more practical, I think you should mention the impact of different cueballs on the pivot point.

The pivot point is not an intrinsic characteristic of the cue, it is more a characteristic of the cue/cueball interaction. Using the same cue, a red-circle cueball will indicate a pivot point that is shorter than for a mudball. This is one way bar players (using BHE) get stung on regular tables.

In order to effectively use pivot compensation, you have to be aware of this and use the pivot point that corresponds to the combination of cue and cueball being used.<hr /></blockquote>Excellent suggestion. Thank you.

FYI, I just added some example calculations at the end of TP B.1 (http://billiards.colostate.edu/technical_proofs/new/TP_B-1.pdf) (see page 7) to show the affects of a heavier or lighter cue ball. Check it out.

Obviously, if you want to compare different cues, it would be important to use the same cue ball for each cue. This could be a factor with data discrepancies, but I don't think it could totally explain why Platinum Billiards' range is so low and so small (unless they use a hollow cue ball /ccboard/images/graemlins/wink.gif ).

Thank you for you insightful post.

Regards,
Dave

dr_dave
11-02-2007, 02:46 PM
<blockquote><font class="small">Quote SpiderMan:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr>Squirt is a function of the cue stick only. It doesn't depend on ball or cloth conditions.<hr /></blockquote>I don't want to hijact your ongoing discussion with Fred, but I think the above is over-simplified - at least if you allow "ball conditions" to include "type of ball".

I made some "ball effect" comments beneath your original post.<hr /></blockquote>Thanks again for pointing this out. See page 7 of TP B.1 (http://billiards.colostate.edu/technical_proofs/new/TP_B-1.pdf). I will try to be more inclusive of people with different weight balls in the future. I don't want to be accused of ball-weight discrimination. /ccboard/images/graemlins/wink.gif

Regards,
Dave

Jal
11-02-2007, 04:39 PM
<blockquote><font class="small">Quote dr_dave:</font><hr><blockquote><font class="small">Quote Jal:</font><hr>I also know of at least one other who obtained similar numbers for a Predator shaft, and seemed to know what he was doing.<hr /></blockquote>Similar to my numbers or similar to Platinum Billiards' numbers? They are quite different.<hr /></blockquote>Similar to Platinum's. I've also read of several people that seem to be able to use backhand english with their "low" squirt cues? I think Colin Colenso might be one of them, but don't quote me. /ccboard/images/graemlins/smile.gif

<blockquote><font class="small">Quote dr_dave:</font><hr><blockquote><font class="small">Quote Jal:</font><hr>... until that recent unpleasentness with the offset correction mentioned earlier. What to do?<hr /></blockquote>
See TP B.1 (http://billiards.colostate.edu/technical_proofs/new/TP_B-1.pdf). I define the pivot length in the center-ball aim position, and then I do the trig and geometry to relate measured squirt angles and offsets to this definition. No approximations are made.<hr /></blockquote>Yes, I meant a correction I made to my figuring. I had remembered a Predator Z squirts about 1.8 degrees at the offset used by either Platinum or Predator. When you mentioned 1.8 degrees in your earlier article (with Dave Gross as the shooter), I just took it as confirmation, ignoring the larger offset used by you.

Jim

Cornerman
11-02-2007, 04:43 PM
<blockquote><font class="small">Quote SpiderMan:</font><hr> In order to effectively use pivot compensation, you have to be aware of this and use the pivot point that corresponds to the combination of cue and cueball being used.

SpiderMan <hr /></blockquote>Exactly! The first time I really realized how different the combination could change the effective squirt, I thought that maybe my stick somehow changed. But, the conditions simply changed.

It's not undreasonable to do a check at every match. It only takes a few seconds.


Fred

cushioncrawler
11-02-2007, 05:47 PM
<blockquote><font class="small">Quote dr_dave:</font><hr>...PS: Please report your results if you perform the experiment with any of your cues. I'd be particularly interested in seeing your results for some Snooker cues (and your famous Steel cue!)...<hr /></blockquote>For sure. I think that Type 2 Pivot iz in effekt Fred's "straight-in-shot". The little that i have dunn to date on this showz that tip-shape iz super-critical to the rezults (for me). A dead-flat tip magnifys my error. A "sharp" radius magnifys my error. A radius of about ball size seems to be best (for me), but i havnt tested this stuff by varying my pivot length (nor varying the cue), will do in 2008. madMac. Oh, and of course i still maintain that grip-wt and bridge-wt affekt squirt, due to the compression wave throwing its wt around, but this iz an old arguement.

mikepage
11-03-2007, 07:52 AM
<blockquote><font class="small">Quote Cornerman:</font><hr> <blockquote><font class="small">Quote SpiderMan:</font><hr> In order to effectively use pivot compensation, you have to be aware of this and use the pivot point that corresponds to the combination of cue and cueball being used.

SpiderMan <hr /></blockquote>Exactly! [...]

Fred <hr /></blockquote>

But Fred, spiderman is using "pivot point" to mean where he pivots when he uses a particular algorithm for aim compensation on shots, which makes it a very different thing from the Squirt Pivot Point.

The Squirt Pivot Point, or the pivot point for short, has nothing to do with object balls and nothing to do with particular plans for aim compensation.

It is a number characteristic of each cue that should probably be stamped on each house cue rather than the weight.

Sure it depends on the cueball mass, but unless I'm wrong about this, there is an official international standard red-circle cueball kept sealed and under constant guard in Paris somewhere. So forget about that.

If you're really keen on using aim&amp;pivot or backhand english or whatever you want to call it, and you want to make balls, then of course where you pivot about changes all over the map. There's no sense in putting swerve or throw into the mix to redefine a "pivot point." The pivot point is the pivot point. It just involves squirt, not throw or swerve.

dr_dave
11-03-2007, 08:18 AM
<blockquote><font class="small">Quote mikepage:</font><hr>The Squirt Pivot Point, or the pivot point for short, has nothing to do with object balls and nothing to do with particular plans for aim compensation.

It is a number characteristic of each cue that should probably be stamped on each house cue rather than the weight.<hr /></blockquote>Even better, I think the natural pivot point location should be visibly indicated on the shaft so it can be easily located. This would be particularly useful on break cues (see Diagram 4 and the explanation in the article (http://billiards.colostate.edu/bd_articles/2007/nov07.pdf)).

Regards,
Dave

Cornerman
11-03-2007, 09:53 PM
<blockquote><font class="small">Quote mikepage:</font><hr> <blockquote><font class="small">Quote Cornerman:</font><hr> <blockquote><font class="small">Quote SpiderMan:</font><hr> In order to effectively use pivot compensation, you have to be aware of this and use the pivot point that corresponds to the combination of cue and cueball being used.

SpiderMan <hr /></blockquote>Exactly! [...]

Fred <hr /></blockquote>

But Fred, spiderman is using "pivot point" to mean where he pivots when he uses a particular algorithm for aim compensation on shots, which makes it a very different thing from the Squirt Pivot Point.
<hr /></blockquote>Maybe you need to absorb the rest of the thread, Mike. I think Spiderman and I are on the same page (horrible pun). I separate true squirt pivot point from effective pivot point (sans swerve). I also have a different pivot point for various shots. But, it's important that I understand the baseline pivot point.

In practical use during game situation, there's little reason to have any idea what the true pivot point is. In comparison from stick to stick, of course its knowledge has its place.

Fred

mikepage
11-04-2007, 07:38 AM
<blockquote><font class="small">Quote Cornerman:</font><hr>
Maybe you need to absorb the rest of the thread, Mike. I think Spiderman and I are on the same page (horrible pun). I separate true squirt pivot point from effective pivot point (sans swerve). I also have a different pivot point for various shots. But, it's important that I understand the baseline pivot point.

In practical use during game situation, there's little reason to have any idea what the true pivot point is. In comparison from stick to stick, of course its knowledge has its place.

Fred <hr /></blockquote>

Fred, you and I have passed a lot of beer through our bodies talking about this--at that really old room in Springfield MA, with Royce in Vegas, at Action in CT, and at that room we shared (the details of which I'll leave between us ;-)).

If you want to suggest people use aim &amp; pivot, then I'm sure you agree they have to bridge at a different point relative to the cue's pivot point
for thin cuts
for a half-ball cut with inside english
for a half ball cut with outside english
for either of these hit hard or soft
for either of these for a different distance to the object ball


..and so forth.

The only request I have is that you don't refer the the aim&amp;pivot bridging length or pivoting length as a "pivot point."

I simply request that to avoid confusion you agree to reserve the phrase "pivot point" to mean the thing that can be stamped on the stick and compares the squirt of one stick to another.

dr_dave
11-04-2007, 10:57 AM
<blockquote><font class="small">Quote Cornerman:</font><hr>In practical use during game situation, there's little reason to have any idea what the true pivot point is.<hr /></blockquote>What about the break shot (see Diagram 4 and the last paragraph on page of my Novemebr '07 article (http://billiards.colostate.edu/bd_articles/2007/nov07.pdf))? What about rail cut shots?

<blockquote><font class="small">Quote Cornerman:</font><hr>In comparison from stick to stick, of course its knowledge has its place.<hr /></blockquote>I think this is something we can all agree on. Every cue has a "natural pivot length" and "natural pivot point" which results in squirt cancellation for a standard-weight cue ball.

Regards,
Dave

dr_dave
11-04-2007, 11:03 AM
<blockquote><font class="small">Quote mikepage:</font><hr> <blockquote><font class="small">Quote Cornerman:</font><hr>Maybe you need to absorb the rest of the thread, Mike. I think Spiderman and I are on the same page (horrible pun). I separate true squirt pivot point from effective pivot point (sans swerve). I also have a different pivot point for various shots. But, it's important that I understand the baseline pivot point.

In practical use during game situation, there's little reason to have any idea what the true pivot point is. In comparison from stick to stick, of course its knowledge has its place.<hr /></blockquote>Fred, you and I have passed a lot of beer through our bodies talking about this--at that really old room in Springfield MA, with Royce in Vegas, at Action in CT, and at that room we shared (the details of which I'll leave between us ;-)).

If you want to suggest people use aim &amp; pivot, then I'm sure you agree they have to bridge at a different point relative to the cue's pivot point
for thin cuts
for a half-ball cut with inside english
for a half ball cut with outside english
for either of these hit hard or soft
for either of these for a different distance to the object ball

..and so forth.

The only request I have is that you don't refer the the aim&amp;pivot bridging length or pivoting length as a "pivot point."

I simply request that to avoid confusion you agree to reserve the phrase "pivot point" to mean the thing that can be stamped on the stick and compares the squirt of one stick to another.<hr /></blockquote>Mike,

I prefer the phrase "natural pivot length" or "natural pivot point." This makes it clear we are discussion the natural property of the cue related to squirt, and not some variable and adjustable bridge length based on aim compensation for throw and/or swerve in combination with squirt.

Regards,
Dave

PS: Excellent post on this and other threads. I hope you are on the BD CCB to stay.

Jal
11-04-2007, 05:15 PM
<blockquote><font class="small">Quote dr_dave:</font><hr>... If you do perform the experiment, please share your results here. I (and I hope others) would like to see what different people report for a wide range of cues.<hr /></blockquote>Here are some pivot point measurements as reported by Patrick Johnson of RSB/AZB. (From his descriptions of other tests, he typically performs them very carefully.)

He says:

"My low-squirt shaft (10mm hollow tip with straight taper) has a pivot point of 24.0 inches, measured as carefully as I can with swerve minimized but probably not eliminated. Performing the same tests on an off-the-shelf Joss (13mm normal tip with pro taper) produces a pivot point of 8.8 inches.

I measured these pivot points two different ways with identical results:

1. The aim-and-pivot test described in the RSB FAQ.

2. Measuring tip offset and total squirt over a measured distance."



The RSB FAQ describes the aim-and-pivot test as follows:

"For each cue stick, there is a particular length of bridge for
which you can aim straight at a close object ball and then pivot
about your bridge hand and shoot straight through the new line and
hit the object ball full. (You can also use this (very old) method
for non-full shots too, but a full shot is best for finding the
right bridge length.) For a stick you want to measure, just find
the needed bridge length. A hint: if you shoot softly at a ball
far away, the cue ball will curve on its way to the object ball,
and your measurement will be useless. Do not give the cue ball the
time or distance to curve. Shoot firmly. Use as much side spin
as you can without miscuing. The shorter the bridge, the more
squirt the stick has. ("Close object ball" means about a diamond
away.) The cue ball should sit in place spinning like a top when
it hits the object ball full."

"For a long pivot length, the bridge is too long to be a comfortable
pivot. Arrange to have the pivot over the rail, and use your back
hand to hold the stick at the pivot while the bridge hand moves.
An alternative is to slide the bridge hand forward after the pivot
to a more comfortable bridge length. Take care to keep the stick
aligned in the new direction."

Jim

dr_dave
11-04-2007, 06:43 PM
Jim,

Thanks a bunch for the info.

I'm surprised more people haven't tried the experiment. It doesn't take very long, and it is useful knowing your cue's natural pivot length (especially for the break shot).

Regards,
Dave

<blockquote><font class="small">Quote Jal:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr>... If you do perform the experiment, please share your results here. I (and I hope others) would like to see what different people report for a wide range of cues.<hr /></blockquote>Here are some pivot point measurements as reported by Patrick Johnson of RSB/AZB. (From his descriptions of other tests, he typically performs them very carefully.)

He says:

"My low-squirt shaft (10mm hollow tip with straight taper) has a pivot point of 24.0 inches, measured as carefully as I can with swerve minimized but probably not eliminated. Performing the same tests on an off-the-shelf Joss (13mm normal tip with pro taper) produces a pivot point of 8.8 inches.

I measured these pivot points two different ways with identical results:

1. The aim-and-pivot test described in the RSB FAQ.

2. Measuring tip offset and total squirt over a measured distance."



The RSB FAQ describes the aim-and-pivot test as follows:

"For each cue stick, there is a particular length of bridge for
which you can aim straight at a close object ball and then pivot
about your bridge hand and shoot straight through the new line and
hit the object ball full. (You can also use this (very old) method
for non-full shots too, but a full shot is best for finding the
right bridge length.) For a stick you want to measure, just find
the needed bridge length. A hint: if you shoot softly at a ball
far away, the cue ball will curve on its way to the object ball,
and your measurement will be useless. Do not give the cue ball the
time or distance to curve. Shoot firmly. Use as much side spin
as you can without miscuing. The shorter the bridge, the more
squirt the stick has. ("Close object ball" means about a diamond
away.) The cue ball should sit in place spinning like a top when
it hits the object ball full."

"For a long pivot length, the bridge is too long to be a comfortable
pivot. Arrange to have the pivot over the rail, and use your back
hand to hold the stick at the pivot while the bridge hand moves.
An alternative is to slide the bridge hand forward after the pivot
to a more comfortable bridge length. Take care to keep the stick
aligned in the new direction."

Jim

<hr /></blockquote>

Cornerman
11-05-2007, 06:18 AM
<blockquote><font class="small">Quote mikepage:</font><hr>
If you want to suggest people use aim &amp; pivot, then I'm sure you agree they have to bridge at a different point relative to the cue's pivot point
for thin cuts
for a half-ball cut with inside english
for a half ball cut with outside english
for either of these hit hard or soft
for either of these for a different distance to the object ball


..and so forth.

The only request I have is that you don't refer the the aim&amp;pivot bridging length or pivoting length as a "pivot point."

I simply request that to avoid confusion you agree to reserve the phrase "pivot point" to mean the thing that can be stamped on the stick and compares the squirt of one stick to another. <hr /></blockquote>I think this is fair.

As I said in a previous post, how one uses the knowledge of the pivot point is up to the user.

Let's remember Mike that what you know as the pivot point is clearly different as what, say, Dr. Dave might know as the pivot point. And, as I said in a previous post, there are two distinct pivot points: the one that sends the cueball down the original cueball aim line and the one that sends the object ball down the original intended path (Spin Induced Throw, no swerve). By simple analysis, the pivot point from the Aim &amp; Pivot test(type 2) is clearly longer than the type 1 pivot point.

So, do you have a suggestion as to what to call the two types? I call the Aim &amp; Pivot pivot point "effective pivot point."

THe understanding of the pivot point is evolving. New words are fine, but at the root, we're pivoting about a point. I could simply say that I'm using variable backhand english and be done with it.

Fred

Cornerman
11-05-2007, 06:27 AM
<blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote Cornerman:</font><hr>In practical use during game situation, there's little reason to have any idea what the true pivot point is.<hr /></blockquote>What about the break shot (see Diagram 4 and the last paragraph on page of my Novemebr '07 article (http://billiards.colostate.edu/bd_articles/2007/nov07.pdf))? What about rail cut shots <hr /></blockquote>For the break shot, this is probably one of the few exceptions. Personally, I don't have success with bridging at the natural pivot point. It's entirely too short of a bridge for me. I think that would be true for anyone, but that's just a guess.

For the rail cut shot... it's not clear to me why the knowledge of the natural pivot point would be beneficial vs. the effective pivot point. But, maybe your method of initial aim for the cut is different than mine. I'll need to ponder this, because now that I'm thinking about it a few more minutes, I can start seeing benefit.

Fred

dr_dave
11-05-2007, 09:00 AM
<blockquote><font class="small">Quote Cornerman:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote Cornerman:</font><hr>In practical use during game situation, there's little reason to have any idea what the true pivot point is.<hr /></blockquote>What about the break shot (see Diagram 4 and the last paragraph on page of my Novemebr '07 article (http://billiards.colostate.edu/bd_articles/2007/nov07.pdf))?<hr /></blockquote>For the break shot, this is probably one of the few exceptions. Personally, I don't have success with bridging at the natural pivot point. It's entirely too short of a bridge for me. I think that would be true for anyone, but that's just a guess.<hr /></blockquote>This is also true for me. The natural pivot length of my break cue is shorter than my preferred bridge. But lately, I've been thinking about using a different cue to break (e.g., a regular cue with a phenolic tip). The automatic squirt cancellation is too appealing to ignore.

Regards,
Dave

dr_dave
11-05-2007, 09:11 AM
Fred,

Now that we have discussed "pivot points" for squirt and throw aim compensation, what about swerve? How do you adjust your aim to account for swerve? Do you set your initial aim line in a direction to account for swerve (based on intuition), and then pivot about your "effective pivot point" (which varies based on speed, type of English, and amount of spin) to adjust for squirt and throw? Or do you (and others) just aim intuitively (without any aim-and-pivot technique) and just judge the combined effects of squirt, swerve, and throw for each shot?

I am curious to hear how you and others deal with all English effects (squirt, swerve, and throw) when aiming.

Thanks,
Dave

Cornerman
11-05-2007, 11:12 AM
<blockquote><font class="small">Quote dr_dave:</font><hr> Fred,

Now that we have discussed "pivot points" for squirt and throw aim compensation, what about swerve? How do you adjust your aim to account for swerve? Do you set your initial aim line in a direction to account for swerve (based on intuition), and then pivot about your "effective pivot point" (which varies based on speed, type of English, and amount of spin) to adjust for squirt and throw? Or do you (and others) just aim intuitively (without any aim-and-pivot technique) and just judge the combined effects of squirt, swerve, and throw for each shot?

<hr /></blockquote>I do both depending on the shot. But, for anything that I would have to go through steps that swerve is going to be in play, I start at an "aim point," with swerve in mind (by semi-intuitive dialing), and then I do the aim and pivot using the effective pivot point.

Fred

Jal
11-05-2007, 12:15 PM
<blockquote><font class="small">Quote dr_dave:</font><hr>...I am curious to hear how you and others deal with all English effects (squirt, swerve, and throw) when aiming.<hr /></blockquote>Intuition.

dr_dave
11-05-2007, 01:04 PM
<blockquote><font class="small">Quote Jal:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr>...I am curious to hear how you and others deal with all English effects (squirt, swerve, and throw) when aiming.<hr /></blockquote>Intuition.<hr /></blockquote>Good answer. Here's my answer:

... intuition backed up by knowledge of and experience with all of the effects concerning squirt, swerve, and throw. These effects include speed, cut angle, distance, cue elevation, type of English, amount of English, amount of draw/follow, table conditions, ball conditions, etc.

I do all of this consciously; although, I suspect some top players might do some of the compensation subconsciously. For example, Mike Sigel refused to admit throw and spin transfer exist, yet he was able to make shots where these effects were factors.

Regards,
Dave

dr_dave
11-06-2007, 12:41 PM
Has anybody tried the experiment to measure your cue's "natural pivot length" yet? The experiment is described starting at the bottom of page two of the article (http://billiards.colostate.edu/bd_articles/2007/nov07.pdf).

Please give it a try and share your results for the cues you use. It will be interesting to see how much the length varies for different cues and how well people's results agree for the same cue.

As pointed out throughout the article, this information might be useful to you, especially for your break cue (see Diagram 4 in the article (http://billiards.colostate.edu/bd_articles/2007/nov07.pdf)).

Regards,
Dave

jingle
11-09-2007, 08:56 AM
OK, I had the day off yesterday so I tested the pivot point of all my different shafts. One note, my table has a thicker, slower cloth that seems to somewhat mute the squirt compared with Simonis. My results:

Valley Supreme bar cue : 12"
J&amp;J Break cue, phenolic tip: 10.5"
16 year old McDermott, 13mm LePro tip: 12"
Josey 12.85 mm, Tiger Hard with nickel tip shape: 13.5"
Josey 12.75mm, Sniper with nickel tip shape: 15"
OB-1 12.75mm, Triangle tip with dime shaped tip: 16"

I don't know how accurate these are, but they are the results I came up with after testing as insructed. -Jason

dr_dave
11-09-2007, 10:06 AM
Jason,

Thank you so much for sharing your results. I hope others will do the same.

For such a short shot with fast speed, I wouldn't expect the cloth type to make much difference. Your numbers seem reasonable to me.

Thanks again,
Dave

<blockquote><font class="small">Quote jingle:</font><hr> OK, I had the day off yesterday so I tested the pivot point of all my different shafts. One note, my table has a thicker, slower cloth that seems to somewhat mute the squirt compared with Simonis. My results:

Valley Supreme bar cue : 12"
J&amp;J Break cue, phenolic tip: 10.5"
16 year old McDermott, 13mm LePro tip: 12"
Josey 12.85 mm, Tiger Hard with nickel tip shape: 13.5"
Josey 12.75mm, Sniper with nickel tip shape: 15"
OB-1 12.75mm, Triangle tip with dime shaped tip: 16"

I don't know how accurate these are, but they are the results I came up with after testing as insructed. -Jason<hr /></blockquote>

jingle
11-09-2007, 10:48 AM
The one result that surprised me was the difference in my two Josey shafts. I noted the difference in tips and diameter in my results thread, but I forgot to note that the 12.85mm/Tiger Hard tipped shaft has a stiffer taper (standard Josey taper) than the 12.75 mm/Sniper tipped shaft (which I requested Josey "soften" the taper on).
-Jason

dr_dave
11-09-2007, 11:10 AM
<blockquote><font class="small">Quote jingle:</font><hr> The one result that surprised me was the difference in my two Josey shafts. I noted the difference in tips and diameter in my results thread, but I forgot to note that the 12.85mm/Tiger Hard tipped shaft has a stiffer taper (standard Josey taper) than the 12.75 mm/Sniper tipped shaft (which I requested Josey "soften" the taper on).
-Jason<hr /></blockquote>I think the results make sense. A larger tip size and "stiffer" taper adds more mass to the end of the shaft. Endmass is what creates squirt (see my August '07 article (http://billiards.colostate.edu/bd_articles/2007/aug07.pdf)).

Thanks again for sharing,
Dave

TennesseeJoe
11-16-2007, 04:42 PM
Dr. Dave, Sorry I haven't been able to try your experiment sooner, but here are my results.

Fury Jump Break 20 inches---a suprise to me
Dufferin house cue 12 inches
Predator 314 18.5 inches

My Fury does seem light in the front end but with the long pivot point and my much shorter bridge length, I may have to reevaluate my choice of break cues.

dr_dave
11-16-2007, 05:21 PM
<blockquote><font class="small">Quote TennesseeJoe:</font><hr> Dr. Dave, Sorry I haven't been able to try your experiment sooner, but here are my results.

Fury Jump Break 20 inches---a suprise to me
Dufferin house cue 12 inches
Predator 314 18.5 inches

My Fury does seem light in the front end but with the long pivot point and my much shorter bridge length, I may have to reevaluate my choice of break cues.<hr /></blockquote>Thank you for responding. It is disappointing to me how few people have responded. I thought there would be more interest.

It is difficult to believe your Fury break cue would have a longer pivot (less squirt) than the Predator 314. I can't imagine how the Fury could have less endmass than the Predator.

My Predator Z result was 20.2 inches, which is better than the 314, as expected.

Regards,
Dave

Qtec
11-17-2007, 09:57 PM
[ QUOTE ]
I had remembered a Predator Z squirts about 1.8 degrees at the offset used by either Platinum or Predator. <hr /></blockquote>

1.8 degrees!

Dave "Predator Z, 19 oz, 11.85 mm tip: 20.2 inches"

Can a person see the difference between 0.1 and 0.2 of a degree?

AIUI, the theory of BHE is that you can't miss! Even if you want to give extreme E and you actually give it less, BHE predicts you will still make the ball because you are pivoting on the right point.
Its a fairy tale. You can't play pool by numbers.
Its totally the wrong way to go.

eg,
what do you do if you have checked the table with your spirit level for rolls, checked the humidity of the room, the moisture content of the cloth, the weight of the balls, and you shoot with E at the correct PP etc etc and you still miss?
What then?
What do you do?
Change the pivot point?
"Did I acount for swerve ?" LMAO

I think with a good player you would see a change in the pivot angle but the player himself would not be aware of it. He just compensates.
How many top players know the pivot point of their cue?
How many care?
How many want to know the PP of their cue?
Not many of the top players I should think.



Q............not picking on you Jal but this thread is all theory, its not a way to play the game.

I,m not saying that these threads are not useful and a great source of pool knowledege but it should be seen in context, for what it is.
Some people could get the wrong idea.

ie, just because you guys are smart, doesn't mean that you are right. LOL

JMO

Q..........what are you aiming at when playing with BHE?

Jal
11-18-2007, 03:41 AM
Qtec,

Probably most of us agree that:

- Calculations won't make you a great player or even a very good one.

- If they could, the game would lose much of its appeal.

- Players mostly learn through playing and practice.

Some statements that you may not agree with are:

- The numbers do reveal things that can take considerably more time to learn at the table, especially if they're subtle.

- They are worth discussing even if it's not guaranteed that anything practical will follow.

<blockquote><font class="small">Quote Qtec:</font><hr>1.8 degrees!

Dave "Predator Z, 19 oz, 11.85 mm tip: 20.2 inches"

Can a person see the difference between 0.1 and 0.2 of a degree?<hr /></blockquote>Maybe not, but the reported squirt angles for the same type of cue vary over a much greater range.

<blockquote><font class="small">Quote Qtec:</font><hr>AIUI, the theory of BHE is that you can't miss! Even if you want to give extreme E and you actually give it less, BHE predicts you will still make the ball because you are pivoting on the right point.
Its a fairy tale.<hr /></blockquote>It only predicts that the cueball will start off in the same direction. As you point out, it cannot guarantee that the shot will still be made (because of differing amounts of swerve and throw).

<blockquote><font class="small">Quote Qtec:</font><hr>You can't play pool by numbers.
Its totally the wrong way to go.<hr /></blockquote>The brain of a player must have the patterns (of ball behavior, for instance) stored away in some fashion. And these are the equivalent of mathematical functions, sans the explicit symbols and numbers. Numbers, or better yet, graphs or diagrams, are a precise way to describe them. If I were learning to fly, I'd kind of like somebody to explain the controls.

<blockquote><font class="small">Quote Qtec:</font><hr>eg,
what do you do if you have checked the table with your spirit level for rolls, checked the humidity of the room, the moisture content of the cloth, the weight of the balls, and you shoot with E at the correct PP etc etc and you still miss?
What then?
What do you do?
Change the pivot point?
"Did I acount for swerve ?" LMAO<hr /></blockquote>CMAO.

<blockquote><font class="small">Quote Qtec:</font><hr>I think with a good player you would see a change in the pivot angle but the player himself would not be aware of it. He just compensates.
How many top players know the pivot point of their cue?
How many care?
How many want to know the PP of their cue?
Not many of the top players I should think.<hr /></blockquote>Having a consistent amount of squirt from cue to cue, for example, should be an advantage. True, pros can adjust, we can adjust, but why bother? And if you do want to use backhand english (BHE), then the location of the pivot point is critical.

<blockquote><font class="small">Quote Qtec:</font><hr>Q............not picking on you Jal but this thread is all theory, its not a way to play the game.<hr /></blockquote>Yes you are, and this despite the fact that I think I agree with your general point. /ccboard/images/graemlins/smile.gif It's the skill part that provides the motivation and enjoyment while at the table. But the theory has a certain appeal of its own, although there is the danger of allowing it to inhibit the development of intuition.

<blockquote><font class="small">Quote Qtec:</font><hr>I,m not saying that these threads are not useful and a great source of pool knowledege but it should be seen in context, for what it is.
Some people could get the wrong idea.<hr /></blockquote>Imho, very well said. No one who can't abide the technical discussions should feel that they are missing out on something essential that can't be learned in other ways. But getting spoon fed some general principles can surely speed things up.

<blockquote><font class="small">Quote Qtec:</font><hr>ie, just because you guys are smart, doesn't mean that you are right. LOL<hr /></blockquote>So true. But I don't think you've seen too much in the way of arrogance here. Or have you?

<blockquote><font class="small">Quote Qtec:</font><hr>Q..........what are you aiming at when playing with BHE? <hr /></blockquote>I don't use BHE so I don't know. But it's probably safe to say that where swerve will be essentially nil (ie, high shot speed and/or close proximity of the balls), they would aim the same as a centerball hit, but adjusted for the change in throw from the english.

Jim

dr_dave
11-19-2007, 11:14 AM
<blockquote><font class="small">Quote Qtec:</font><hr>Dave "Predator Z, 19 oz, 11.85 mm tip: 20.2 inches"

Can a person see the difference between 0.1 and 0.2 of a degree?<hr /></blockquote>Absolutely not. However, I was able to notice a change in 1/4 inch in pivot location with the experiment. The experiment does not measure squirt angle (in degrees) directly. It measures the pivot point location as a distance (in inches, not degrees). When I ran the experiment described in my November '07 article (http://billiards.colostate.edu/bd_articles/2007/nov07.pdf), I measured the final pivot point location to the nearest tenth of an inch. It is probably not that accurate, but it is probably accurate to 1/4 inch, or at least 1/2 inch.

<blockquote><font class="small">Quote Qtec:</font><hr>AIUI, the theory of BHE is that you can't miss!<hr /></blockquote>Where did you read that? BHE and FHE aim-and-pivot methods are crude aim-compensation techniques that account only for squirt. Without good intuition of swerve and throw effects (and the effects of cue elevation, shot speed, shot distance, ball and cloth conditions, etc), the methods are of little value. Now, as I communicated to Fred, there are some shots where knowledge of the "natural pivot length" can be important. The best examples are the break shot and fast rail-cut-shots (see my artilce (http://billiards.colostate.edu/bd_articles/2007/nov07.pdf) and the previous messages in this thread).

To me, the main value of the "natural pivot length" experiment is to provide an easy way to compare the amount of squirt for various cues with a single distance measurement (see the article (http://billiards.colostate.edu/bd_articles/2007/nov07.pdf) for details).

<blockquote><font class="small">Quote Qtec:</font><hr>Even if you want to give extreme E and you actually give it less, BHE predicts you will still make the ball because you are pivoting on the right point.<hr /></blockquote>Where did you read that?<blockquote><font class="small">Quote Qtec:</font><hr>Its a fairy tale.<hr /></blockquote>Agreed.<blockquote><font class="small">Quote Qtec:</font><hr>You can't play pool by numbers.<hr /></blockquote>Agreed.<blockquote><font class="small">Quote Qtec:</font><hr>Its totally the wrong way to go.<hr /></blockquote>Agreed; although, I think knowledge of effects can be a useful thing. (I won't start this debate again. It has already been beaten to death under "mental aspects" here (http://billiards.colostate.edu/threads.html).)

<blockquote><font class="small">Quote Qtec:</font><hr>eg, what do you do if you have checked the table with your spirit level for rolls, checked the humidity of the room, the moisture content of the cloth, the weight of the balls, and you shoot with E at the correct PP etc etc and you still miss?
What then?
What do you do?
Change the pivot point?<hr /></blockquote>I don't know, because I don't do those things.
<blockquote><font class="small">Quote Qtec:</font><hr>"Did I acount for swerve?"<hr /></blockquote>If I was using English, I sure hope I did (either consciously or subconsciously). I also hope I had good intuition of and adjustment for squirt and throw (either consciously or subconsciously).

<blockquote><font class="small">Quote Qtec:</font><hr>I think with a good player you would see a change in the pivot angle but the player himself would not be aware of it. He just compensates.<hr /></blockquote>Agreed.
<blockquote><font class="small">Quote Qtec:</font><hr>How many top players know the pivot point of their cue?<hr /></blockquote>I personally don't know of any.
<blockquote><font class="small">Quote Qtec:</font><hr>How many care?
How many want to know the PP of their cue?<hr /></blockquote>Probably very few.
<blockquote><font class="small">Quote Qtec:</font><hr>Not many of the top players I should think.<hr /></blockquote>Agreed.

<blockquote><font class="small">Quote Qtec:</font><hr>Q............not picking on you Jal but this thread is all theory, its not a way to play the game.<hr /></blockquote>Agreed, but the information and understanding can still be useful (e.g., for helping one build intuition faster and more efficiently).

<blockquote><font class="small">Quote Qtec:</font><hr>I,m not saying that these threads are not useful and a great source of pool knowledege but it should be seen in context, for what it is.<hr /></blockquote>Agreed.
<blockquote><font class="small">Quote Qtec:</font><hr>Some people could get the wrong idea.<hr /></blockquote>If you think there are specific things in my artilce (http://billiards.colostate.edu/bd_articles/2007/nov07.pdf) that might make people "get the wrong idea," please let me know.

<blockquote><font class="small">Quote Qtec:</font><hr>ie, just because you guys are smart, doesn't mean that you are right. LOL<hr /></blockquote>I didn't say we were smart, but I agree with your statement. I do think you are smart, and I usually agree with most of what you write.

<blockquote><font class="small">Quote Qtec:</font><hr>Q..........what are you aiming at when playing with BHE?<hr /></blockquote>I don't know because I don't use BHE. The "natural pivot length" for my Predator Z shaft is too long for BHE.

Regards,
Dave

TennesseeJoe
11-21-2007, 03:16 PM
A correction. My Fury Break Cue has a pivot point of 8 inches. I don't know what I did wrong the first time, but then again it was the first test.

dr_dave
11-21-2007, 05:41 PM
<blockquote><font class="small">Quote TennesseeJoe:</font><hr> A correction. My Fury Break Cue has a pivot point of 8 inches. I don't know what I did wrong the first time, but then again it was the first test. <hr /></blockquote>Thank you for posting the correction. That sounds much more reasonable and in line with my numbers.

Regards,
Dave

Qtec
11-23-2007, 07:42 AM
[ QUOTE ]
Where did you read that? BHE and FHE aim-and-pivot methods are crude aim-compensation techniques that account only for squirt. Without good intuition of swerve and throw effects (and the effects of cue elevation, shot speed, shot distance, ball and cloth conditions, etc), the methods are of little value. <hr /></blockquote>

I thought the whole point of BHE [ and various aiming systems] were to eliminate intuition?

[ QUOTE ]
Quote Qtec:Even if you want to give extreme E and you actually give it less, BHE predicts you will still make the ball because you are pivoting on the right point.

Dave: Where did you read that? <hr /></blockquote>

In your break situation you say [ QUOTE ]
cue unintentionally pivoted during the stroke, still resulting in a direct hit <hr /></blockquote>

Its pretty clear, even if you hit the QB with more or less E than intended, you will still hit the 1B head on.

You keep going on about swerve, something few players will take into account unless they are playing a slow E shot from distance.[ something to be avoided!]




The day I mark the pivot point of my cue is the day I quit playing. When I get down on the shot I should be concentrating on my target, not where my pivot point is and not if my bridge is to one tenth of a cm of that 'magic' spot to make the shot.
What you call 'intuition', I call it the result of 1,000s of hours of practice.
When people moan "I can't play with E" is there a magic cure for them? All [ I,m guessing] of these people couldn't a target 5 times out of 10 from 3 ft........and they wonder why they can't play with E?

I digress.
Take a guy who has played for years but only once a week. If he plays 3 months 3 times a week you will see an improvement. The two main reasons are that he gets used to the table and he is learning the properties of his cue.


Q

DSAPOLIS
11-23-2007, 08:13 AM
I just want to know something ... all of you that discuss this stuff go to great length to collect this minutia - what I want to know is this - how has it improved your game? Are you consistently running out, and is it because of having all of this information? Probably not.

Prior to reading internet billiard forums, I had never heard of any of this stuff. All I did was get down in my stance and I shot the balls into the holes. You can hand me any cue off the wall, any custom cue - shaft cmbination and like Qtec said, I would compensate for it with out really thinking about it.

When I teach my students, one of the first things I do is pull a house cue off the wall and I shoot the same shots that I demonstrated with my personal playing cue. Most of the time, I have them pull the cue off the wall. I can do that because I trust my stroke. I don't have anything against these topics, I just I believe that new players should concentrate their mental energy in other directions.

When I wanted to get better at this game, all I did was watch Buddy Hall, Jim Rempe, and Mike Sigel. I asked a lot of questions to players that were at the level I wanted to get to - none of them mentioned this stuff - and I am glad.

Ralph_Kramden
11-23-2007, 09:28 AM
<blockquote><font class="small">Quote DSAPOLIS:</font><hr> I just want to know something ... all of you that discuss this stuff go to great length to collect this minutia - what I want to know is this - how has it improved your game? Are you consistently running out, and is it because of having all of this information? Probably not.

Prior to reading internet billiard forums, I had never heard of any of this stuff. All I did was get down in my stance and I shot the balls into the holes. You can hand me any cue off the wall, any custom cue - shaft cmbination and like Qtec said, I would compensate for it with out really thinking about it.

When I teach my students, one of the first things I do is pull a house cue off the wall and I shoot the same shots that I demonstrated with my personal playing cue. Most of the time, I have them pull the cue off the wall. I can do that because I trust my stroke. I don't have anything against these topics, I just I believe that new players should concentrate their mental energy in other directions.

When I wanted to get better at this game, all I did was watch Buddy Hall, Jim Rempe, and Mike Sigel. I asked a lot of questions to players that were at the level I wanted to get to - none of them mentioned this stuff - and I am glad. <hr /></blockquote>

I think the information provided is good to know... but is it really required reading to play excellent pool? I think not.

I know very good players that have the limited ability in math to only add $100+$100=$200 but they know what they can do with their cue. They can pocket balls even when the cueball 'squirts' to the side, and they play for it.

Check out the shot at 2:54 in this video. It's almost a sraight in shot, but look at the action on the cueball. I don't think anyone heard the term 'squirt' when this was filmed.

www.youtube.com/watch?v=ekyLXFehvvk (http://www.youtube.com/watch?v=ekyLXFehvvk)

I enjoy reading about squirt, BHE, FHE and find the posts about these things very interesting, but as DSAPOLIS points out.. how has it improved your game? I think a smooth stroke, correct speed and knowing where to contact the cueball is what keeps you at the top level. There is nothing like practice.

dr_dave
11-23-2007, 11:24 AM
<blockquote><font class="small">Quote Qtec:</font><hr><blockquote><font class="small">Quote dr_dave:</font><hr>Where did you read that? BHE and FHE aim-and-pivot methods are crude aim-compensation techniques that account only for squirt. Without good intuition of swerve and throw effects (and the effects of cue elevation, shot speed, shot distance, ball and cloth conditions, etc), the methods are of little value. <hr /></blockquote>
I thought the whole point of BHE [and various aiming systems] were to eliminate intuition?<hr /></blockquote>BHE is a method that can be used to automatically compensate one's aim for squirt. However, squirt is not the only factor that comes into play with all shots where English is used, so BHE is not a magical "silver bullet" that eliminates the need for "intuition" for all English effects. As Fred has pointed out, BHE can also be used to help compensate for both squirt and throw (with an alternative "pivot point" definition); but as pointed out elsewhere in this thread, the value of this modified method is also questionable.

<blockquote><font class="small">Quote Qtec:</font><hr>Even if you want to give extreme E and you actually give it less, BHE predicts you will still make the ball because you are pivoting on the right point.

Dave: Where did you read that? <hr /></blockquote>Sorry, but I don't remember reading that. Obviously, the statement is true only if changes in swerve and throw are not significant factors in the shot. I think my May '07 article (http://billiards.colostate.edu/bd_articles/2007/may07.pdf) does a pretty good job explaining most of the limitations of the BHE method. Check it out.

<blockquote><font class="small">Quote Qtec:</font><hr>In your break situation you say<blockquote><font class="small">Quote dr_dave:</font><hr>cue unintentionally pivoted during the stroke, still resulting in a direct hit<hr /></blockquote> Its pretty clear, even if you hit the QB with more or less E than intended, you will still hit the 1B head on.<hr /></blockquote>I think this is true only if the initial center-ball aim is accurate, the bridge is close to the "natural pivot length" for the cue, and the break speed is fast enough to limit swerve as a factor. Do you agree?

<blockquote><font class="small">Quote Qtec:</font><hr>You keep going on about swerve, something few players will take into account unless they are playing a slow E shot from distance.[ something to be avoided!]<hr /></blockquote>Are you implying swerve is not a factor when most players use English? Whether people think they take into account squirt, swerve, and throw or not, sometimes they might do so without necessarily being aware (e.g., they might compensate subconsciously or they might use a stroke speed where the swerve and/or throw effects mostly cancel the squirt effect).

<blockquote><font class="small">Quote Qtec:</font><hr>The day I mark the pivot point of my cue is the day I quit playing. When I get down on the shot I should be concentrating on my target, not where my pivot point is and not if my bridge is to one tenth of a cm of that 'magic' spot to make the shot.<hr /></blockquote>No disagreements here. Although, if I were selecting a break cue, and a range of natural pivot lengths were available, I would prefer to select the cue with the pivot length that most closely matches my most comfortable break bridge length (per my Novemeber '07 article (http://billiards.colostate.edu/bd_articles/2007/nov07.pdf)).

<blockquote><font class="small">Quote Qtec:</font><hr>What you call 'intuition', I call it the result of 1,000s of hours of practice.<hr /></blockquote>I agree. Solid intuition can come only from lots of practice and experience. Although, I still think knowledge and understanding can help speed up the intuition-building process (for some people anyway).

Thank you for your comments,
Dave

dr_dave
11-23-2007, 11:53 AM
<blockquote><font class="small">Quote DSAPOLIS:</font><hr>I just want to know something ... all of you that discuss this stuff go to great length to collect this minutia - what I want to know is this - how has it improved your game? Are you consistently running out, and is it because of having all of this information? Probably not.<hr /></blockquote>I remember when I first started using English many many years ago, every once in a while I would miss a shot even though I was sure I hit where I was aiming, and I would be shocked that I missed the shot. In hindsight, I think I missed many of those shots because I didn't fully understanding or have good intuition of the effects of squirt, swerve, and throw (especially throw, when playing on bar tables where the ball conditions were less than ideal), or I wasn't experienced enough to make better decisions concerning when and how English should be used. I appreciate your point of view, but I still think many intermediate players can benefit from improving their knowledge and understanding of the game.

Now, I also agree with you that to get to the point where you can consistently run racks, you need to have lots of skills that can come only with lots of practice and play. To consistently run racks, one needs a repeatable stroke, great visualization and aiming, great speed control, good planning, good judgment, good mental focus, determination, etc! "Knowledge" and "understanding" alone do not provide these things.

<blockquote><font class="small">Quote DSAPOLIS:</font><hr>Prior to reading internet billiard forums, I had never heard of any of this stuff. All I did was get down in my stance and I shot the balls into the holes. You can hand me any cue off the wall, any custom cue - shaft cmbination and like Qtec said, I would compensate for it with out really thinking about it.

When I teach my students, one of the first things I do is pull a house cue off the wall and I shoot the same shots that I demonstrated with my personal playing cue. Most of the time, I have them pull the cue off the wall. I can do that because I trust my stroke.<hr /></blockquote>I would not be as confident with you unless all of the cues on the wall had good tips and none of them had a lot more squirt than the others (assuming I was shooting a shot requiring significant English).

<blockquote><font class="small">Quote DSAPOLIS:</font><hr>I don't have anything against these topics, I just I believe that new players should concentrate their mental energy in other directions.<hr /></blockquote>I don't think many people would disagree here. Most energy should be put towards strengthening aim and stroke fundamentals. If a player cannot aim well or stroke consistently, English is probably not going to help them very much.

Regards,
Dave

DSAPOLIS
11-23-2007, 12:13 PM
Dave

If we ever meet - I challenge you to hand me any cue - house cue - custom cue - I don't care what it is. I will perform 3 shots with any cue of your choosing using varying degrees of speed and english ...

I will also play a set against the 9 ball ghost and you can bet what you'd like - I guarantee you or anybody else that I won't have much of a problem adjusting to any shaft or any cue- and I could care less about pivot points, squirt, swerve, defelection, or dominant eye.

Years ago I would listen to these arguments and take notes, but then I started to watch the mechanics of some of the people that were discussing these topics at length. A large majority of them (some not all) couldn't run out the easiest of layouts.

I tell my students all the time - its not he tip, its not the cue - it's YOU. When you accept that, then what you're shooting with won't matter half as much as much as devisng a plan to overcome your deficiencies.

dr_dave
11-23-2007, 12:27 PM
<blockquote><font class="small">Quote DSAPOLIS:</font><hr> Dave

If we ever meet - I challenge you to hand me any cue - house cue - custom cue - I don't care what it is. I will perform 3 shots with any cue of your choosing using varying degrees of speed and english ...

I will also play a set against the 9 ball ghost and you can bet what you'd like - I guarantee you or anybody else that I won't have much of a problem adjusting to any shaft or any cue- and I could care less about pivot points, squirt, swerve, defelection, or dominant eye.<hr /></blockquote>I don't doubt your claim one bit. I know you are a great player, and I know you could easily "adjust" to any cue. My point before was that you would need to adjust if you change from a low-squirt cue to a high-squirt cue! And it seems like you agree.

<blockquote><font class="small">Quote DSAPOLIS:</font><hr>I tell my students all the time - its not he tip, its not the cue - it's YOU. When you accept that, then what you're shooting with won't matter half as much as much as devisng a plan to overcome your deficiencies.<hr /></blockquote>That sounds like great advice, and I bet you are a good teacher.

Regards,
Dave

BigRigTom
11-23-2007, 12:31 PM
I think both Blackjack and Dr. Dave are correct and sounds like you are both agreeing to an extent.
I remember my mentor telling me something similar to what Blackjack is saying...it was related to the cue ball (big, small, magnetic, red circle, clean, dirty etc, etc, etc) the trick was to adjust to what ever it was. It was me, not the ball.

I would like to point out that I personally agonize over the details sometimes to the point it becomes ridiculous but I am not satisfied until I understand "WHY" that happened and why it seems to ALWAYS happen that way.
These kinds of threads help us low talented but detail minded people to understand the points that may be unimportant to people like Blackjack (those who obviously have amazing talent to begin with).

Jal
11-23-2007, 01:14 PM
<blockquote><font class="small">Quote DSAPOLIS:</font><hr>...I guarantee you or anybody else that I won't have much of a problem adjusting to any shaft or any cue...<hr /></blockquote>But I'm guessing that you probably play with one cue, or a limited set, most of the time so that you don't have to constantly make adjustments. It's when you're making adjustments that your "feel" is not as reliable and those dreaded conscious processes come into play. I'd rather not be mystified as to what has changed. I'd like to at least know what variable is different and therefore have some idea what to do about it. Confusion is not intuition.

Jim