confused about bridge lengths

[Snapshot9]

Back in them old days ...

when I was 14 (43 years ago) and read 3 Pool books,
it stated a normal bridge length as being 6-8 inches.
I think over time that has lengthened a little. Most of
the time when I lengthen my bridge it is because I have
to because balls are in the way, and I may have to use
a long bridge from a rail, not because I want to.

 

[mikepage]

Your turn to be an Instructor.

The yin and yang of my world is that we are all instructors and we are all students.

How can we do this zero acceleration thing consistently on any chosen shot?
There are many gauges for acceleration. Can't find one to gauge de-celeration. Name one good argument.

Mike. These are the things we can learn by. Waiting for your reponse....SPF-randyg

There is a very important core issue here, imo, one that rears its head many times when we're looking for some sort of optimum approach, and that is the issue of *sensitivity* to error or sensitivity to changes in a variable. Let me give a few examples and then explain how the idea applies here.

First imagine you are swinging a bat to hit a fastball. You can swing normally, i.e., horizontally, or you can swing vertically--like when you swing an axe chopping wood. You can hit the ball either way, but it's much harder to contact the ball using the vertical swing. There is a very different sensitivity of the result to the timing of the swing here. What is the result of swinging a little early or a little late for the normal swing? A little early might send the ball toward left field and a little late might send the ball toward right field. That same range of timing for the vertical swing would go from an early complete miss to a late complete miss. The outcome for the vertical swing is much more sensitive to the timing of the swing.

Another example comes from the importance of the natural roll half-ball hit carom angle in pool. Here the outcome is the cueball direction and the variable is the fullness of hit. If you hit a little fuller than half ball or a little thinner than half ball, the cueball caroms of in amazingly close to the same direction as for a half-ball hit. For other carom angles, the outcome (direction of the cueball) changes by a lot more for small changes in fullness of hit. It's really pretty striking. If you cut a ball with an angle anywhere from 26 degrees to 30 degrees, for example, the cueball will carom off at an angle of 33.6 degrees to within a tenth of a degree. This powerful information is used by 3C players all the time.

How does this relate to stroke timing? In a normal practice stroke, i.e., one that doesn't hit a ball, the player accelerates the cue with the forearm rear of vertical. Then with the forearm close to vertical, the cue reaches a maximum speed and has zero acceleration. Then with the forearm forward of vertical, i.e., during the followthrough part, the cue is slowing down (acceleration is negative). If you plotted the speed of the stick versus distance it would look like a hump. At any point along the hump, the slope is the acceleration. The outcome here is speed of the shot, and the issue is speed control. You want the speed of the stick and ultimately the speed of the cueball to be as insensitive as possible to the timing of the stroke. That is, if you strike the ball a wee bit earlier or a wee bit later in your stroke sequence, you want the result to be not very different. This happens when the acceleration is zero, when the stick is at its maximum speed.

mike page
fargo

 

[mikepage]

No one has mentioned the aspect of squirt v pivot length in this thread yet, but it is very very important.

The idea that hitting (let's say) left of the CB aim point, making the CB travel to the left of your original aim cannot be assumed. It will depend on whether your bridge is in front of, or behind your cue's squirt pivot point.

eg. If your cue's squirt pivot point is at 8 inches (which is pretty normal), then if you bridge at this distance from the CB, whether you hit left or right on the CB, the CB will travel down the original center ball aim line.

Bridging closer, a left hit will deflect the CB to the left.
Brdging further, a left hit will deflect the CB to the right.
[...]
[/B]

I don't agree that 8" is a normal pp. I've not seen one that short on any cue that was nor specially rigged for high squirt.

If you bridge nead the cue's pp, then the cueball will go in the same direction regardless of what your rear hand does. So if you line up right and keep your bridge fixed there is a "self correction" of stroke errors. Here is a post I made to RSB in 1998 about this self sorrection when the bridge length is not equal to the pivot point.

**************************

FROM 7-24-98 RSB POST: *bl=bridge length, pp=pivot point

*Also it's not just the bl=pp stick that tends to cancel stroke errors.
Suppose you're hitting a shot with english that has a two degree "V of
acceptance." That is, suppose the shot will fail if the cueball deviates by
more than one degree in either direction from the ideal path. *Starting from
a perfectly lined up position and shooting with bridge length L using *a
stick of pivot point P, I get (assuming squirt is proportional to
displacement) that the following expression must be within the one degree
threshold:

* * * * theta = B(1 - L/P)

B here is the angular displacement of the stick from the initial allignment
(pivoting about the bridge). Theta is the deviation of the cueball path from
the desired path. *So for the squirtless stick, with P = infinity, *theta = B
and therefore the stick has to remain within one degree of allignment for
success. For the bl=pp (L=P) stick, the stick can pivot anywhere without a
deviation of the cue ball path. *How about for real sticks? *Suppose the
bridge length is 8 inches. *Then the above equation yields the following
table for maximum acceptable angular deviation of the stick (due to stroke
problems).

stick pivot point * maximum angular displacement
_________________ * ____________________________

* 4 inches * * * * * * * 1.0 *degrees
* 6 inches * * * * * * * 3.0 *degrees
* 8 inches * * * * * * * many degrees
*12 inches * * * * * * * 3.0 *degrees
*16 inches * * * * * * * 2.0 *degrees
*24 inches * * * * * * * 1.5 *degrees
*48 inches * * * * * * * 1.2 *degrees
*squirtless * * * * * * *1.0 *degrees

So even for the common 16 inch pivot point stick, the "self correction" of
squirt allows twice the deviation from the ideal as does the squirtless stick.

Or, turning this around, if you have a stick with a 16 inch pivot point, then
the following bridge lengths give you the following maximum angular
displacements:

*bridge length * * *maximum angular displacement
_________________ * ____________________________

* 4 inches * * * * * * * 1.3 *degrees
* 6 inches * * * * * * * 1.6 *degrees
* 8 inches * * * * * * * 2.0 *degrees
*12 inches * * * * * * *4.0 *degrees
*16 inches * * * * * * *many degrees

A squirtless stick has a maximum angular displacement of 1.0 degrees for any
bridge length.

> I guess my point is that there are no magical cures.

damn!

I'm not trying to overemphasize the importance of this "stroke" error
relative to the aiming errors. *They may well for all practical purposes wash
out this effect, but they may not too. *And it may be this is a useful
consideration for those whose "stroke" is not so good compared to their
ability to determine the right aim and their ability to lay down the stick
correctly.

 

[Cornerman]

i have a follow-up question. how does bridge length equate to the power of your stroke? i asked several advanced players and top pros here in manila who mostly plays on slow cloth. they say that they use long bridges (about 12 - 15 inches) because it adds more power to their stroke. they criticized me for having a short bridge, cause as they said, "you'll only choke your stroke and will not put enough spin on it as much as a long bridge does". what do you all think about this?

The longer stroke length allows a player to get to whatever desired speed/velocity without putting as much effort (force) into the stroke. And with less effort, you might get better accuracy by being under more control.

If you have to hit a cueball at 12 mph, and you only have say a 1" stroke, you have to ramp up your stroke to go from 0-12 mph over 1". That's quite a lot of effort. If you had a 6" stroke, you can ramp up your speed to that same12 mph from 0-6", or 6 times less force.

If you get to some of these super long strokes, say, 12", you can get up to that 12mph speed with 1/2 the force compared to 6" stroke. However, you still have to make sure your cue is going straight. That's another issue altogether.

But anyway, that's the reason why some people can get good action (e.g., draw) with what it seemingly less effort: because they are indeed using less effort (force).

Fred

 

[Colin Colenso]

I don't agree that 8" is a normal pp. I've not seen one that short on any cue that was nor specially rigged for high squirt.

If you bridge nead the cue's pp, then the cueball will go in the same direction regardless of what your rear hand does. So if you line up right and keep your bridge fixed there is a "self correction" of stroke errors. Here is a post I made to RSB in 1998 about this self sorrection when the bridge length is not equal to the pivot point.

Mike,
I got myself an Accueshot device www.accueshot.com that can accurately determine where the CB strikes the rail. I'm also installing a table in a new apartment in 9 days and I'll do some more testing using a mechanical bridge in set position with a CB in set position, using some different cues. Hopefully this will produce some clearer data.

I don't feel my 8-9" pivot point is far off, and the system of adjustments that I listed above are working tremendously in pratice. I will go through all the variable methodically once I have my table in and try to identify accurate adjustment parameters for bridge lengths for various cue pivot points.

I'm hoping it works as well as I think it will.

 

[Cornerman]

Rule 1: When playing with OE aim thicker or lengthen bridge a few inches.

Rule 2: When playing with IE, aim thinner or shorten bridge a few inches.

Rule 3: When playing at speed, aim thinner or shorten bridge a few inches..

I think these are important statements. There isn't one pivot point. There is a range of pivot points, when considering spin induced throw. The shortest would be for extreme Inside English, while the longest would be for extreme Outside English. That's because of the difference in spin-induced throw (direction and magnitude).

I use the same pivot point that I calculated with the straight-in aim&pivot test method. This is specifically an Inside English Pivot Point. So, I use that pivot point and start my centerball aim point thicker for Outside English compared to inside english.


Fred <~~~ thinks most normal cues are at 10-12" for inside english

 

[Cornerman]

Your turn to be an Instructor. How can we do this zero acceleration thing consistently on any chosen shot?
There are many gauges for acceleration. Can't find one to gauge de-celeration. Name one good argument.

If you teach to be at impact at the bottom of the pendulum stroke, that point is zero acceleration and constant velocity. Any small deviation from that position will still be very close to zero acceleration. So, it's the most repeatable impact position to strive for.

BTW, any gauge that can monitor acceleration should be able to monitor deceleration.

Also, IMO the most important number is velocity, not acceleration. The Jacksonville Experiment showed that most players will in fact hit the cueball while slightly decelerating. This makes complete sense for SET PAUSE FINISH practitioners as the SET position is at the bottom of the pendulum (perpendicular forearm). That would mean that the impact is very slightly forward of that position. Forward of the perpendicular forearm/bottom of the pendulum would constitute deceleration (in the X linear direction), unless an increase in muscle use is applied.

Fred

 

[pete lafond]

Randy. Maybe I misunderstood, but I thought you said the "sweet spot" had the cue accelerating at impact. If so then it's a fact that if the cueball was slightly further away the stick would go faster at impact.

By the away, I do not agree that it is desirable to have the cue accelerating at impact. There are, I think, good arguments for having zero acceleration at impact.

mike page
fargo

Just throwing this in.

The stroke is pure acceleration that is constant, otherwise it's a poor stroke. Maybe I'm off here but at impact deceleration begins as a result striking the CB (the stoke begins to slow down as a result of an object being hit). Therefore maximum acceleration is always at the moment before impact.

 

[jsp]

Just throwing this in.

The stroke is pure acceleration that is constant, otherwise it's a poor stroke. Maybe I'm off here but at impact deceleration begins as a result striking the CB (the stoke begins to slow down as a result of an object being hit). Therefore maximum acceleration is always at the moment before impact.

Hi Pete. Don't want to be a nitpicker, but I think you're confusing the definition between velocity and acceleration. Velocity is the rate of distance over time and acceleration is the rate of velocity over time. Maximum acceleration is the point at where the velocity is changing the most. From this definition, the maximum acceleration point in your stroke is the absolute beginning of the stroke.

The moment before impact should be where there is maximum velocity, not acceleration. At this peak velocity point, the cue then slows down it's velocity over time. So I would agree with others that you can think of this point as having "zero acceleration".

 

[pete lafond]

Hi Pete. Don't want to be a nitpicker, but I think you're confusing the definition between velocity and acceleration. Velocity is the rate of distance over time and acceleration is the rate of velocity over time. Maximum acceleration is the point at where the velocity is changing the most. From this definition, the maximum acceleration point in your stroke is the absolute beginning of the stroke.

The moment before impact should be where there is maximum velocity, not acceleration. At this peak velocity point, the cue then slows down it's velocity over time. So I would agree with others that you can think of this point as having "zero acceleration".

Yes. I was running late for an appointment when I wrote this.

What I meant is that a proper stroke is changing its velocity from the very beginning, or accelerating. This is not constant and shouldn't be otherwise we have a jerky motion in our stroke (cause for missed shots). Each stroke starts slow and then continues to pick up speed to what is ideal for the shot.

Friction and mechanics cause the speed to begin slowing down as we make contact with the CB and we have reached the midpoint of our pendulum.

 

[mikepage]

I think these are important statements. There isn't one pivot point. There is a range of pivot points, when considering spin induced throw. The shortest would be for extreme Inside English, while the longest would be for extreme Outside English. That's because of the difference in spin-induced throw (direction and magnitude).

I use the same pivot point that I calculated with the straight-in aim&pivot test method. This is specifically an Inside English Pivot Point. So, I use that pivot point and start my centerball aim point thicker for Outside English compared to inside english.


Fred <~~~ thinks most normal cues are at 10-12" for inside english

Fred - I think you have an unconventional use of the phrase "pivot point." Here's my understanding. The "squirt pivot point" or "pivot point" is a fundamental property of the cue. It has nothing to do with the cloth and nothing to do with friction between the balls. If you hit a cueball with a tip offset of b and the initial direction of the cueball deviated from the stick direction by an angle theta, then the stick pivot point, pp, is given by

pp = b/sin(theta)

This has nothing to do with an object ball or a player's bridge length. If a player wants to do "aim & pivot," i.e., aim a shot centerball and then apply english by pivoting about the bridge hand, then he must consider swerve as well as object ball throw. If you could ignore these, then a player could just apply english by doing aim&pivot about the stick's pp. But you generally can't ignore these. If you insist on aiming and pivoting to apply english, then as you guys say object ball throw makes the aim&pivot bridge length depend on how clean the balls are and whether you're applying inside or outside english. And because of swerve, the aim&pivot bridge length depends upon speed as well.

mike page
fargo

 

[TheConArtist]

Colin there he is, i was waiting for your advice in this thread. Thanks to you and Fred.

 

[Cornerman]

Fred - I think you have an unconventional use of the phrase "pivot point." Here's my understanding. The "squirt pivot point" or "pivot point" is a fundamental property of the cue. It has nothing to do with the cloth and nothing to do with friction between the balls.

This is all true, Mike. The squirt line has nothing to do with anything other than ball and cue. It's not a fundamental property of the cue itself, because the cue ball mass plays an important part of the definition.

But without the consideration of ball to ball friction, you cannot use the squirt pivot point as an aiming tool. So, I've used the Inside English pivot pool as a very repeatable pivot point. It all makes sense as to why some people can simply use BHE without thinking too much; the inside english pivot point on normal cues resides somewhere within an acceptable range of a normal bridge length.

So, if you say your pivot point is some >22", I think it's misleading to anyone if you're not considering actually making a ball. You might be saying that your pivot point is >20" to make the cueball go straight, but it won't make the ball. If you aren't considering ball interactions, I can safely assume that you are not using Aim & Pivot as an aiming technique in real play. I do, and I can do this by using my previous definition (using the Inside English, full-ball, straight in Aim&Pivot Test).

Fred

 

[mikepage]

This is all true, Mike. The squirt line has nothing to do with anything other than ball and cue. It's not a fundamental property of the cue itself, because the cue ball mass plays an important part of the definition.

Well I suppose if you took a cue and played 3C billiards or snooker with it, it would have a different pivot point. By the same token a 19 oz cue would be 3 oz on the moon. But if we're willing to stipulate we're hitting pool balls near the surface of the earth, then the weight and the pivot point are numbers that could be stamped on a cue.

But without the consideration of ball to ball friction, you cannot use the squirt pivot point as an aiming tool. So, I've used the Inside English pivot pool as a very repeatable pivot point. It all makes sense as to why some people can simply use BHE without thinking too much; the inside english pivot point on normal cues resides somewhere within an acceptable range of a normal bridge length.

So, if you say your pivot point is some >22", I think it's misleading to anyone if you're not considering actually making a ball. You might be saying that your pivot point is >20" to make the cueball go straight, but it won't make the ball. If you aren't considering ball interactions, I can safely assume that you are not using Aim & Pivot as an aiming technique in real play. I do, and I can do this by using my previous definition (using the Inside English, full-ball, straight in Aim&Pivot Test).

Fred

I sometimes use aim&pivot to help me out. Say a 12" bridge is comfortable and I'm playing with an 18" pp stick. If I'm not considering throw, I'll move parallel a third of my intended offset and then I'll pivot about my bridge hand to get the remaining two thirds. For an inside english shot I might simply pivot about my 12" bridge hand (to compensate for both squirt and throw). For an outside english shot with this cue I might move parallel half the offset and then pivot the rest. This is all for shots with no significant swerve.

Whenever I pick up a strange cue I do a quick test of the squirt pivot point. Then I'm able to do this "parallel plus pivot" adjustment with a comfortable bridge for any shot with no significant swerve. When there's swerve I pretty much just aim by feel.

I think most people's bridge is longer than they think it is.

mike page
fargo

 

[Cornerman]

I sometimes use aim&pivot to help me out. Say a 12" bridge is comfortable and I'm playing with an 18" pp stick. If I'm not considering throw, I'll move parallel a third of my intended offset and then I'll pivot about my bridge hand to get the remaining two thirds. For an inside english shot I might simply pivot about my 12" bridge hand (to compensate for both squirt and throw). For an outside english shot with this cue I might move parallel half the offset and then pivot the rest. This is all for shots with no significant swerve.

This seems a bit complex. No wonder you (or others) haven't exactly embraced the "just pivot about your bridge" idea.

There are a few things that I've now read in your post coupled with what you and I have discussed in the past that has now made things come together on what you're saying.. Your pivot point test must be different than the Aim & Pivot test. I recall you telling me that you "didn't understand the Aim & Pivot Test." I now take that to mean that the results you get with the Aim & Pivot Test are vastly different than the results you get with your current "true pivot test" method. Is that fair? I think that the Aim & Pivot Test as outlined in the FAQ is specifically an Inside English Pivot Point.

I came to that realization on that AccuShot device, a laser measurement device that will light up when you hit the cueball to the desired point within 0.020". I kept incorrectly compensating. I could never hit the spot with English, but had no problems hitting this shot, without hitting the cushion. (that was the stipulation) just to show that accuracy in pocketing the ball with English is different than hitting a laser point with a spinning cueball only.

START(
%FC9R8%Ph0G9%UD1Q2%VD4Q2%WE3Q3%Xf7H3%Y]5Y8%ZC4Q1%[q3Q1%\^4Z3
%]c8E8%^q9P4%eA7a4%_R3L9%`]3H0%ac0E2%bD0Z2%cC8V5%dC9S8
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I won't attempt to argue against your "18 in. 2/3rds parallel offset." But, I'd like to see you attempt the Aim & Pivot Test as outlined in the FAQ, and try that number on all squirt-heavy inside english shots. That has always been the starting point for me. All aim adjustments from there (need for a thicker aim for outside english, thinner aim for longer swerve affected shots), I'll still use the same Aim & Pivot Test Pivot Point (or the Inside English Pivot Point). Since my IEPP is at around 11-12", I can easily pivot about my bridge.

This idea goes hand-in-hand with much of the Backhand English discussion.

That being said, the "True Pivot Point" has me thinking about kick shots and how I compensate for them. Thanks Mike.

Fred

 

[Gerry]

Do you guys think about this stuff when your playing?~......

My ignorance is truly bliss!.......

Another thought on bridge length, since we're in maybe the 2nd generation of pool players since the 50's, maybe the old school straight pool style is phasing out. Those guys used to use what today we would call "short" bridges because they did'nt need to move the cueball far for position, and it was more accurate. I feel to play 9ball, and move the ball all over the table, you need to stretch out the bridge length a few inches, or whatever is comfortable.

I think mostly closed, short bridges = old school
Longer, flowing, open bridges = newer school

Gerry

 

[Cornerman]

Do you guys think about this stuff when your playing?~......

Yes. At least aiming and pivot points, yes I do. Without thinking about them, I'd miss. That's like asking if someone thinks about how hard to hit a ball, or if he has a pre-shot routine. It's a method, a system. We all use a system, or we all fall into the trap of failing to repeat success only to have to find that feeling again.

Did you look at my shot illustrated? What's your make percentage? What's the average player's make percentage? I"d say pretty damned low for the second question. Would you rather that someone goes happily with their blissful ignorance never being able to comfortably make that shot?

Are these posts too "scientific" for people? Methodical for sure, but so is standard BCA Instruction. . And all of you aren't going to fart too loud at those posts. And you shouldn't.They're supposed to be methodical and wordy. That's why this is a BILLIARDS DISCUSSION FORUM, and not CHAT ROOM. I'm sure if you watched Mike Page or Colin Colenso shoot (or me for that matter), you wouldn't ask the question. Regardless of what is typed here, we're players first and foremost.

I think mostly closed, short bridges = old school
Longer, flowing, open bridges = newer school

If I'm allowed to be so wordy, I'll expand on this thought. The power shots in today's 9-ball game have manifested itself (or vice versa) in longer bridges. As a related note, the shot accuracy needed in 9-ball has gotten modern players to get lower on the shot. The tight control games of yesterday like 14.1 required a more standup style, presumably to see the angles better, while less power but more hit accuracy (speed and position) manifested itself in shorter bridges (compared to today.)

The few times I play 14.1 or one-pocket, my bridge length automatically gets shorter and my body stands straighter. I suspect every player is like this to a degree.

Fred

 

[Colin Colenso]

Yes. At least aiming and pivot points, yes I do. Without thinking about them, I'd miss. That's like asking if someone thinks about how hard to hit a ball, or if he has a pre-shot routine. It's a method, a system. We all use a system, or we all fall into the trap of failing to repeat success only to have to find that feeling again.

Did you look at my shot illustrated? What's your make percentage? What's the average player's make percentage? I"d say pretty damned low for the second question. Would you rather that someone goes happily with their blissful ignorance never being able to comfortably make that shot?

Are these posts too "scientific" for people? Methodical for sure, but so is standard BCA Instruction. . And all of you aren't going to fart too loud at those posts. And you shouldn't.They're supposed to be methodical and wordy. That's why this is a BILLIARDS DISCUSSION FORUM, and not CHAT ROOM. I'm sure if you watched Mike Page or Colin Colenso shoot (or me for that matter), you wouldn't ask the question. Regardless of what is typed here, we're players first and foremost.

If I'm allowed to be so wordy, I'll expand on this thought. The power shots in today's 9-ball game have manifested itself (or vice versa) in longer bridges. As a related note, the shot accuracy needed in 9-ball has gotten modern players to get lower on the shot. The tight control games of yesterday like 14.1 required a more standup style, presumably to see the angles better, while less power but more hit accuracy (speed and position) manifested itself in shorter bridges (compared to today.)

The few times I play 14.1 or one-pocket, my bridge length automatically gets shorter and my body stands straighter. I suspect every player is like this to a degree.

Fred

Well put Fred!

I think the point of these systems is eventually to simplify the trial and error system of trying to memorize the Intuitive Judgement (IJ) of thousands of different shots.

One example I found was practising with inside english. I'd hit a few shots until I got the alignment right, and then when I had to play the same shot center ball, I'd find my IJ often changed such that I'd overcut.

Without really knowing what is going on it is very hard to make the correct systematic adjustments. Hence most players stick only to the type of shots they are confident in executing. This limits the shot options.

 

[jnav447]

I can only think of one top player who had a very short bridge (Allen Hopkins). I watched him play 1 pocket about a week ago and , trust me, he made whitey do whatever he wanted, but he is the exception. A few years ago, Roger Griffis was really struggling, and Efren worked with him, lengthening his bridge length, and in short order Roger's game started picking up. I've always found that I can pocket certain shots better with a shorter stroke, but can't control whitey as well. It seemed that I had to play more to stay in stroke with a longer bridge, for some reason, but I always played my best pool with a pretty long bridge length. Plus, chicks dig the long stroke!

 

[SmoothStroke]

Baseball

how does the length of your bridge equate to accuracy? or does it really matter if you use a long or a short bridge?

i've read in some books and several instructional articles that short bridge lengths (around 7 -9 inches) makes your game more accurate. yet i've rarely seen a top pro with such short bridge length. in snooker, where accuracy is a priority, top pro's i've seen uses long bridge lengths. so, what is the truth about bridge lengths?

The single hardest thing to do in any sport is to hit a baseball. From little league to major league they are taught to ...CHOKE UP ON THE BAT..you can learn to play with any bridge.Allen Hopkins has a choked bridge and Efren Reyes has a bridge you can charge a toll to get across. Both great players. With a 7 -9 inch bridge you can do anything with the cueball ..yes its more accurate....choke up on the bat and you might hit that 95 mph fastball with that round bat and round ball...dead square