Degrees Of Deflection

Tennesseejoe

Tennesseejoe

AzB Silver Member
Silver Member
I assume that deflection starts when the cue hits the cue ball anyplace other than the direct center of the cue ball horizontal line. It is my understanding that speed has almost untestable effect on the amount of deflection.

Now my question is: Does deflection increase based on how far off center the cue tip hits the cue ball? Is there a rule of thumb on the amount?
 
Depends on shaft and you will need to learn it based on what you have.

Speed, cue level and distance all contribute to how deflection affects the shot in addition.
 
Tennesseejoe said:
Now my question is: Does deflection increase based on how far off center the cue tip hits the cue ball?
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Yes.
The coefficient of deflection is dependent on the end-mass of the cue and the mass of the CB.
There are minor trigonometric effects (atan(CB angle from center)) which are minor because one can only get about 1/2 way from center to edge without miscuing.

Is there a rule of thumb on the amount?
Click to expand...

http://billiards.colostate.edu/technical_proofs/new/TP_A-31.pdf
http://billiards.colostate.edu/technical_proofs/new/TP_B-1.pdf
http://billiards.colostate.edu/technical_proofs/new/TP_B-7.pdf
 
Good question OP. I too have heard that deflection is not related to the speed that you strike the CB. My experience says otherwise on hard strokes, but there is definitely the chance that I'm not stroking as accurately on the hard strokes and hence the observed greater deflection.

EDIT: http://billiards.colostate.edu/technical_proofs/new/TP_A-31.pdf

Formula 13 above indicates that the deflection does not depend on F (impulse) applied to the CB so that says (in theory) that the speed you stroke the ball does not affect the degree of deflection holding all other variables constant.
 
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buckshotshoey said:
Add a little top or bottom to that right or left english and speed DEFINITELY has a huge effect.
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A technical detail for those who are interested in such things:

CB deflection (squirt) itself isn't affected by speed, but squirt is always accompanied by swerve, a mini-masse that curves the CB in the opposite direction from squirt - and swerve is affected by speed. More speed = less swerve and that looks like more squirt.

Using top or bottom with side spin increases the effect of swerve so it's easier to notice (looks like even less squirt), but it happens on almost every shot to a more or less degree.

pj
chgo
 
Never understood the fixation about deflection. Then again I shot with a 314 and runout like water.

I'd assume increased deflection occurs with more forceful shots as the object ball breaks traction with the cloth. Allowing wider deflection.
 
2strong4u said:
I'd assume increased deflection occurs with more forceful shots as the object ball breaks traction with the cloth. Allowing wider deflection.
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The CB has to "break traction with the cloth" no matter what direction it goes, and squirt acts just like aiming in a different direction. In other words, no difference.

pj
chgo
 
Patrick Johnson said:
The CB has to "break traction with the cloth" no matter what direction it goes, and squirt acts just like aiming in a different direction. In other words, no difference.

pj
chgo
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Physics is a discipline I never studied. I just make the ball and try to runout. The best pool is art, not science. A guy in dead stroke can't even tell you the time of day.
 
2strong4u said:
Physics is a discipline I never studied. I just make the ball and try to runout. The best pool is art, not science. A guy in dead stroke can't even tell you the time of day.
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It's true that knowing the physics of pool isn't necessary to play well. I corrected your statement to help readers who might be interested in that stuff, not to criticize you.

pj
chgo
 
Tennesseejoe said:
I assume that deflection starts when the cue hits the cue ball anyplace other than the direct center of the cue ball horizontal line.
Click to expand...
True.

Tennesseejoe said:
It is my understanding that speed has almost untestable effect on the amount of deflection.
Click to expand...
True again (as Patrick as been pointing out).

Tennesseejoe said:
Now my question is: Does deflection increase based on how far off center the cue tip hits the cue ball? Is there a rule of thumb on the amount?
Click to expand...
There is a rule of thumb if you know where your cue's intrinsic pivot point is located (varies from cue to cue, more or less). Imagine you have that location marked, say, with a blinking LED. When you line up for a shot, while holding the tip close to the cueball, picture a line going from that LED through the center of the cueball. That's the direction in which the cueball will initially take off. In other words, it will initially head in that direction instead of where the cue is pointed during your stroke (unlike a center ball hit) and the difference between those two directions (LED to CB center versus stroke direction) is the amount of squirt (aka CB deflection).

With that image in mind, it's clear that squirt increases with tip offset (from CB center) and the closer the LED is to the cue's tip, the greater the increase.

Jim
 
Tennesseejoe said:
Does deflection increase based on how far off center the cue tip hits the cue ball?
Click to expand...
Yes.

Is there a rule of thumb on the amount?
Click to expand...
As Jal said in different words:

Ignoring swerve*, the amount of CB deflection for each pivot length of CB travel = 1 tip offset. (This is one way of describing the definition of "pivot length".)

If, for example, the tip offset (distance from center) is 1/2" (about maximum sidespin) and your shaft's pivot length is 12", then the CB will "squirt" offline 1/2" for each 12" of travel.

The illustration below might help explain that.

pj
chgo

*The amount of aim correction needed is usually less because of swerve.

For definitions, search for "pivot length" and "swerve".

View attachment 3204
 

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  • Using Pivot Length to Estimate Squirt.jpg
    Using Pivot Length to Estimate Squirt.jpg
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littlewing1208 said:
Good question OP. I too have heard that deflection is not related to the speed that you strike the CB. My experience says otherwise on hard strokes, but there is definitely the chance that I'm not stroking as accurately on the hard strokes and hence the observed greater deflection.

EDIT: http://billiards.colostate.edu/technical_proofs/new/TP_A-31.pdf

Formula 13 above indicates that the deflection does not depend on F (impulse) applied to the CB so that says (in theory) that the speed you stroke the ball does not affect the degree of deflection holding all other variables constant.
Click to expand...

Formula (4) says that squirt of the cueball is directly related to the velocity of the cuestick at contact and he further explains that the squirt is offset by the deflection of the cue.

Formula 13 neglects the velocity of the cue because the equation is only used to show the angle of squirt, not the amount of squirt...i.e. the harder you hit, the further along that angle the cueball will squirt.
 
In terms of a Rule of Thumb, try this:

(For firm shots, hence little swerve, using standard equipment).

For each 1/2 tip offset, where 1.5 tip offset is maximum squirt, the deflection is approx 1 degree.

To put this in more realistic terms, for 0.5 tip offset, the deflection will be about 1 tip width (1/2") over 4 diamonds. For 1 tip offset, 2 tips (1 inch) over 4 diamonds, for max offset 1.5 tips, 3 tip widths (1.5") deflection over 4 diamonds.

So, hitting from the baulk line to the end rail, approx 6 diamonds, with maximum 1.5 tip offset, the deflection for an average cue will be around 4.5 tip widths, or 2.25 inches (a ball width).

The low deflection cues will be about 50-70% of these estimates.

FWIW: High english will swerve much earlier and can create the impression that little deflection has occurred. It can catch you out as it's very hard to predict.... hence I tend to hit these shots no higher than 1/2 tip above CCB.

Colin
 
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ElCorazonFrio said:
Formula (4) says that squirt of the cueball is directly related to the velocity of the cuestick at contact and he further explains that the squirt is offset by the deflection of the cue.

Formula 13 neglects the velocity of the cue because the equation is only used to show the angle of squirt, not the amount of squirt...i.e. the harder you hit, the further along that angle the cueball will squirt.
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I think you're misreading... squirt isn't "offset" by the cue's sideways motion; it's caused by it.

Also, it's commonly accepted that stroke speed doesn't affect squirt (but it does affect swerve, which looks like it's affecting squirt).

pj
chgo
 
Patrick Johnson said:
I think you're misreading... squirt isn't "offset" by the cue's sideways motion; it's caused by it.

Also, it's commonly accepted that stroke speed doesn't affect squirt (but it does affect swerve, which looks like it's affecting squirt).

pj
chgo
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No, I guarantee that I am not misunderstanding. The momentum of the shaft causes squirt. In order for the cueball to squirt one way, there has to be a force reacted in the opposite direction, this force is resolved by the shaft and the result is the deflection of the shaft. The deflection of the shaft is, most definitely, increased with the velocity of the cue.

Reread my post. The angle of the squirt is not affected by speed. Think of it this way, squirt is the distance from the line of stroke that the cueball moves. Your image shows this. Imagine hitting the cueball with right english so it only rolls two feet. The distance to the left of the aim line is the squirt distance. Now hit the ball in the same spot so it rolls four feet...what is the squirt distance now? It is double that of the first shot because it has twice as much speed, but the angle of squirt is the same for both.
 
degrees of squirt, elevation and speed

For what its worth.

If I have a shot that I know to play at a High Right or High Left Standard at 10 or 2 oclock. That same shot played with Middle Ball or Below Center English I allow just a bit more for effective squirt distance. If that means that the amount of swerve is less than the former shot played at High Right or Left, I am happy knowing that just a bit more allowance needs to be made. The amount of allowance of course depends on the cue type, the base allowance amount for that type, the distance and as we are discussing the angle of the application of the cue. The same shot at a similar distance played with a elevated cue would be different and that allowance amount would be affected. More cue elevation the more the more swerve unless minimized by increase speed. At least this is the way I understand it.
 
Take a broomstick with a radius tip an hit the CB off center and you get squirt with no bending of the shaft during contact.

Will a soft cue tip (Elk Master) may have a different squirt angle than a hard tip (broom stick) due to compression of the tip or lack there of?
 
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