Using Pivot Length to Estimate Squirt

[Patrick Johnson]

If you think knowing your cue's Pivot Length is vaguely interesting but not really useful, you might be overlooking a potentially helpful aiming aid. Knowing your cue's Pivot Length is the basis for a simple method of visualizing squirt correction that can reduce the guesswork.

Pivot Length is the distance from your cue's tip to its Pivot Point, the place to pivot your cue to apply squirt-correcting backhand english. This is because (here's the useful part ->) Pivot Length is the distance the CB travels to be off target by exactly the same distance as your Tip Offset from the CB's center.

That means you should aim your shot one Tip Offset to the side of your target for each Pivot Length between the CB and the OB (minus something for swerve).

Here's a drawing with some detail about how to do that. For illustration it assumes a Pivot Length of exactly 12.5 inches (1 diamond on a 9-foot table), which is probably not an uncommon "high squirt" Pivot Length. Of course, each cue's Pivot Length can be different.

pj
chgo

View attachment 195123

 

[The Renfro]

Good stuff right there PJ... Had not seen that visual :thumbup:

 

[Mikjary]

PJ,

Thanks for the graphic. It puts a perspective on what we do to aim with spin. I knew there was a point my subconscious mind used to estimate cue ball squirt, but I never thought to diagram it.

Have you found any personal shortcuts as you start aiming off of the object ball? Long shots could possibly have a fractional component using the the other edge of the cue ball.

What part does speed control play in this formula discounting swerve?

Best,
Mike

 

[Patrick Johnson]

PJ,

Thanks for the graphic. It puts a perspective on what we do to aim with spin. I knew there was a point my subconscious mind used to estimate cue ball squirt, but I never thought to diagram it.

I originally made this drawing (really a screen capture from VP3 with some lines and text added) just to illustrate the meaning of the Pivot Point. It was only after making the drawing that I thought it might be useful for estimating squirt while shooting. Even though I think this method is potentially useful, I probably won't use it myself. I correct for squirt/swerve entirely by feel, and I'm too invested in my old ways to tinker with new methods.

Have you found any personal shortcuts as you start aiming off of the object ball?

More like the opposite of a short cut, but I like to aim each shot with centerball first, then adjust for squirt/swerve. Keeps me "grounded".

What part does speed control play in this formula discounting swerve?

None that I know of.

pj
chgo

 

[SpiderWebComm]

Nice graph, although I'm failing to see the point. Assuming the pivot point of the cue is at 12" --- the graph is very cute. In reality, almost no cue would really be exactly 1 diamond in length and most shots aren't straight along the diamond line (to measure), so the result wouldn't correlate to your graph in a useful manner.

I'm guessing you're saying once one figures the exact pivot point, should they decide to measure, the results would equal (somewhat) your graph. In actual play, I can't imagine that'd be relevant.

Finding the bridge length that makes one MOST successful and incorporating adjustments learned over time makes the most sense. If someone's pivot point were 10.2", they'd be screwed trying to figure your graph. But like you said, you don't even use it-- it's just an FYI.

 

[Patrick Johnson]

Nice graph, although I'm failing to see the point. Assuming the pivot point of the cue is at 12" --- the graph is very cute. In reality, almost no cue would really be exactly 1 diamond in length and most shots aren't straight along the diamond line (to measure), so the result wouldn't correlate to your graph in a useful manner.

I'm guessing you're saying once one figures the exact pivot point, should they decide to measure, the results would equal (somewhat) your graph. In actual play, I can't imagine that'd be relevant.

Finding the bridge length that makes one MOST successful and incorporating adjustments learned over time makes the most sense. If someone's pivot point were 10.2", they'd be screwed trying to figure your graph. But like you said, you don't even use it-- it's just an FYI.

Even though I said in a couple of places that 12.5" is an example and each cue can be different, I didn't explicitly say you should use your own cue's actual pivot length because I figured that was pretty obvious. Guess I was right.

pj
chgo

 

[Deadon]

PJ

Thanks for a very thoughtful and interesting approach. I can't vouch for its accuracy, but it looks like a good baseline to start and make individual adjustments. Sort of like a combination of pivot and ghost ball stuff. Very interesting.

Mike

 

[scottjen26]

Thanks for reposting that. I think I saw it, along with another diagram/test you did, on Dr. Dave's site, probably taken from an older thread here.

I found your approach to determining the pivot point to be somewhat easier and quicker to perform than the standard test that requires the pivot point to be changed, I've taught that to several people when trying to help them understand their own cues especially regarding using BHE as a guide.

Thanks!
Scott

 

[Patrick Johnson]

PJ

Thanks for a very thoughtful and interesting approach. I can't vouch for its accuracy

It's theoretically perfectly accurate to measure squirt alone, but there are some factors that decrease its accuracy in practice:

1. It doesn't adjust for swerve.
2. You might misjudge the number of pivot lengths between CB/OB.
3. You might misjudge the total number or amount of Tip Offsets to adjust by.
4. You might mismeasure the Pivot Length for your cue.

...but it looks like a good baseline to start and make individual adjustments.

That's how I think it's useful - as a reference measurement that gets you closer to the actual adjustment, but is still an estimate that needs "by feel" refinement, or as a "second opinion" that aids the method you already use.

pj
chgo

 

[Patrick Johnson]

Thanks for reposting that. I think I saw it, along with another diagram/test you did, on Dr. Dave's site, probably taken from an older thread here.

I don't remember if it's on Dave's site or not. I think I did post the drawing here before, but have tinkered with it since and thought it might stand reposting with a little better explanation.

I found your approach to determining the pivot point to be somewhat easier and quicker to perform than the standard test that requires the pivot point to be changed, I've taught that to several people when trying to help them understand their own cues especially regarding using BHE as a guide.

You're probably thinking of the "Simple Squirt Test" I posted a couple of times, once in December 2007 and again (with some refinements) in November 2010. I'm glad you like it - I don't know if it's better than the "traditional" aim-and-pivot way that Dave also describes on his website, but I think it's a little simpler and makes the underlying meaning of the Pivot Point a little more clear.

pj
chgo

 

[dr_dave]

I don't remember if it's on Dave's site or not. I think I did post the drawing here before, but have tinkered with it since and thought it might stand reposting with a little better explanation.

Pat,

I had your older explanation and illustrations here:

cue natural pivot length resource page​

FYI, I've replaced it by your latest version.

Good job,
Dave

 

[Patrick Johnson]

Pat,

I had your older explanation and illustrations here:

cue natural pivot length resource page​

FYI, I've replaced it by your latest version.

Good job,
Dave

Thanks for updating, Dave.

pj
chgo

 

[KMRUNOUT]

Pat,

I could certainly be wrong, but I thought that cueball squirt was affected by firmness of stroke. Are you implying that slow rolling the ball yields the exact same (or effectively nearly the same) squirt as rifling it at break speed? I find that hard to believe. However, I have no evidence to support my notion...I'd like to hear what you think.

Thanks,

KMRUNOUT

 

[dr_dave]

... I thought that cueball squirt was affected by firmness of stroke. Are you implying that slow rolling the ball yields the exact same (or effectively nearly the same) squirt as rifling it at break speed?

The answer is yes. Squirt does not depend on shot speed. For proof, see my February '08 and September '07 Billiards Digest articles.

Now, swerve changes quite a bit with shot speed, cue elevation, and ball/cloth conditions. For more information, and video demonstrations, see:

squerve resource page​

FYI, for a summary of all squirt, swerve, and throw effects, with video demonstrations and additional resources, see:

squirt, swerve, and throw effects summary​

Enjoy,
Dave

 

[Patrick Johnson]

Pat,

I could certainly be wrong, but I thought that cueball squirt was affected by firmness of stroke. Are you implying that slow rolling the ball yields the exact same (or effectively nearly the same) squirt as rifling it at break speed? I find that hard to believe. However, I have no evidence to support my notion...I'd like to hear what you think.

Thanks,

KMRUNOUT

As Dave says, squirt itself is the same at all speeds, but swerve is greater at lower speeds, and since swerve works in the opposite direction it seems like squirt is less at lower speeds. It's probably most accurate to say that the combination of squirt and swerve (sometimes called "squerve") changes the required aim less than squirt alone would.

I think the swerve part of the overall effect is the biggest reason that sidespin shots are missed, because swerve is less predictable than squirt.

pj
chgo

 

[KMRUNOUT]

As Dave says, squirt itself is the same at all speeds, but swerve is greater at lower speeds, and since swerve works in the opposite direction it seems like squirt is less at lower speeds. It's probably most accurate to say that the combination of squirt and swerve (sometimes called "squerve") changes the required aim less than squirt alone would.

I think the swerve part of the overall effect is the biggest reason that sidespin shots are missed, because swerve is less predictable than squirt.

pj
chgo

Thank you. I was thinking this as I typed my message. Makes perfect sense.

So the NET effect is that shots at higher speed DO require more correction than shots at a lower speed (to a point...I suppose maybe at super low speeds swerve might MORE than compensate. Likewise, elevation will likely effect swerve significantly more than squirt).

Thanks for the reply.

KMRUNOUT

 

[lfigueroa]

Nice graph, although I'm failing to see the point. Assuming the pivot point of the cue is at 12" --- the graph is very cute. In reality, almost no cue would really be exactly 1 diamond in length and most shots aren't straight along the diamond line (to measure), so the result wouldn't correlate to your graph in a useful manner.

I'm guessing you're saying once one figures the exact pivot point, should they decide to measure, the results would equal (somewhat) your graph. In actual play, I can't imagine that'd be relevant.

Finding the bridge length that makes one MOST successful and incorporating adjustments learned over time makes the most sense. If someone's pivot point were 10.2", they'd be screwed trying to figure your graph. But like you said, you don't even use it-- it's just an FYI.

lol. "Bring out your dead! Bring out your dead!"

Lou Figueroa

 

[Jaden]

If using BHE...

Nice graph, although I'm failing to see the point. Assuming the pivot point of the cue is at 12" --- the graph is very cute. In reality, almost no cue would really be exactly 1 diamond in length and most shots aren't straight along the diamond line (to measure), so the result wouldn't correlate to your graph in a useful manner.

I'm guessing you're saying once one figures the exact pivot point, should they decide to measure, the results would equal (somewhat) your graph. In actual play, I can't imagine that'd be relevant.

Finding the bridge length that makes one MOST successful and incorporating adjustments learned over time makes the most sense. If someone's pivot point were 10.2", they'd be screwed trying to figure your graph. But like you said, you don't even use it-- it's just an FYI.

When I was using BHE, I used a sharpie to mark off the pivot point on my cue. I drew a circle around my shaft. If a certain shot required me to use a different bridge point I could line up and pivot from the pivot point and then slide my bridge hand up the shaft to Put it in place with the aim line already established...

What's really funny about this thread is that I remember having six shit tons of arguments with PJ where he denied BHE even WORKED....

I have to laugh my ass off at him posting a thread supporting BHE...

JAden

 

[lfigueroa]

It's theoretically perfectly accurate to measure squirt alone, but there are some factors that decrease its accuracy in practice:

1. It doesn't adjust for swerve.
2. You might misjudge the number of pivot lengths between CB/OB.
3. You might misjudge the total number or amount of Tip Offsets to adjust by.
4. You might mismeasure the Pivot Length for your cue.


That's how I think it's useful - as a reference measurement that gets you closer to the actual adjustment, but is still an estimate that needs "by feel" refinement, or as a "second opinion" that aids the method you already use.

pj
chgo

PJ ,while I do think this is interesting, I do have to say that while I understand it (sorta of) from the RSB discussions (I think Ron had a lot to say about this?) I cannot imagine how anyone would be thinking/using this in competitive play.

Lou Figueroa

 

[Patrick Johnson]

What's really funny about this thread is that I remember having six shit tons of arguments with PJ where he denied BHE even WORKED....

That's your Alzheimers again - at least you're enjoying it.

I've said before that BHE doesn't work without adjustments by feel.

pj
chgo