I've read several articles about deflection but still do not know if cue speed increases deflection. Any opinions?
Does speed effect deflection?
- Thread starter Tennesseejoe
- Start date
great video. In short, I use a regular non LD shaft and when hitting hard shots with a lot of english, I find that squirt is a much bigger factor than swerve (hitting the ball hard delays the distance from the cue ball at which the ball starts swerving). If you hit the ball at a medium or softer speed, the squirt/ swerve seem to act to cancel each other out more, resulting in an aim point closer to where you would aim if you didn't use side spin..
Fantastic video, thanks for linking!
Another great vid by Mike Page. I realy like how Mike explains the difference between Deflection (cue stick) and Squirt (cue ball).
This is what Instruction is all about.
randyg
The Mike Pages' video at 2:35 states the jury is still out on speed effecting squirt. While this video is great and I appreciate it--- the original question still exists: Does speed increase deflection?
Tennessee, you may want to read this article by Dr. Dave, specifically Diagram 2 and the associated text. As a practical matter, I think it answers your question.
http://billiards.colostate.edu/bd_articles/2008/feb08.pdf
Jim
Yes, the cue stick deflects more at a higher speed......randyg
I am refering to cue ball movement as deflection is defined by Dr. Dave (see below). But since you bought it up---where is that information available?
Thanks for your response.
This is the seventh article in my series dealing with “squirt.” So far, we have looked at basic terminology, the physics behind squirt, some experimental results, the effects of follow and draw on squirt and swerve, techniques for compensating one’s aim for squirt, low-squirt cues, and tip shape effects. To refresh your memory, squirt, also called deflection, refers to the angular change in the initial cue ball (CB) direction due to an off-center hit. In other words, when you use English, the CB doesn’t go where you are aiming because of squirt. For more background information, see my August ’07 article and refer to NV 4.13 and NV A.17. When using English, it is also important to be aware of the effects of swerve (see NV 4.14 and NV 7.12) and throw (see NV 4.15, NV 4.16, NV A.21, and my August ’06 through July ’07 articles). Sometimes, the phrase “effective squirt” or the term “squerve” is used to refer to the net effect of both squirt and swerve on the shift in the CB position at object ball (OB) impact (see my August ’07 article for more information). If you want to refer back to any of my past articles, they are all available on my website (billiards.colostate.edu)
Last edited:
vary the experiment?
So you disagree with Dr. Dave's data on this page? Can you be more specific, and why do you think so? To me, when I shoot harder it intuitively feels like there is going to be more squirt but his data suggest otherwise..... BUT, if you seperate his graph into two parts divided at the "dip" he mentions at medium speeds, you can still argue that from medium to high there is an increase, and from medium to low speeds there is also an increase. Perhaps at very low speeds the rock is just slipping off the tip to squirt sideways, and at high speeds the rock is just "getting out of the way" of a heavier object, but at medium speeds there is an effective transfer of energy that is more in the intended direction. Although subtle, his data plot looks like a reverse parabola that I always thought would be there. Would Dr. Dave be willing to re-do the experiment without chalk on the tip? If he does, it would be interesting... especially if he compared different degrees of offset, and/or comparing an ld performance shaft. I really love Dr. Dave's stuff, keep it up Dave! Let's learn some more.....
So you disagree with Dr. Dave's data on this page? Can you be more specific, and why do you think so? To me, when I shoot harder it intuitively feels like there is going to be more squirt but his data suggest otherwise..... BUT, if you seperate his graph into two parts divided at the "dip" he mentions at medium speeds, you can still argue that from medium to high there is an increase, and from medium to low speeds there is also an increase. Perhaps at very low speeds the rock is just slipping off the tip to squirt sideways, and at high speeds the rock is just "getting out of the way" of a heavier object, but at medium speeds there is an effective transfer of energy that is more in the intended direction. Although subtle, his data plot looks like a reverse parabola that I always thought would be there. Would Dr. Dave be willing to re-do the experiment without chalk on the tip? If he does, it would be interesting... especially if he compared different degrees of offset, and/or comparing an ld performance shaft. I really love Dr. Dave's stuff, keep it up Dave! Let's learn some more.....
Speed effects everything.......................
oops, there goes my attention span again....
yeah, I see where Dave tried a laminated shaft.... I will look through all his stuff before I shoot my big mough off again.... but I still think there is a subtle parabola in the data.....
yeah, I see where Dave tried a laminated shaft.... I will look through all his stuff before I shoot my big mough off again.... but I still think there is a subtle parabola in the data.....
Hunger Strike, if the measurements truly reflect something going on during the cue-cueball interactions, and not, as Dr. Dave suggests, a possible error introduced by the machine, then there is, as you indicated, a slight dependence on speed. The dependence is not what I would have guessed, and maybe there is something to your explanation. But, as a practical matter, we can all probably agree with his conclusion: "I think it is safe to say that squirt is very nearly constant with speed and doesn’t increase with speed as the “myth” curve suggests."
Jim
scientists frequently disagree....
When I took college statistics, the professor passed around a small but info packed book called "how to lie with statistics." Once you read it you will be very skeptical of graphs, even very well designed ones such as Dr. Dave has posted. Since the graph is parabolic and is trending upward in squirt angle at both ends of the velocity plot, why use just a range of 3 to 8 mph? I need something to guage the speed of MY typical shot speeds in order to speak further, but do you see my point? parabolas can be logarithmic... so could the upward trend seen at 7-8 mph spike at a slightly higher velocity? 0.3 degrees of angle difference seems small, but on big tables with small pockets, the right contact point could be fractions of millimeters and that angle difference might mean something over the length of a table. I like to pinch balls at a distance, but I like to use as much speed as possible to cinch the shot, so for a player who shoots my style could really use more info here...... Does Dr. Dave have a table of angles overlaying points on a 9' table? I think I will get some measuring equipment, like a big protractor, to check out the difference in contact point on an average shot for me, say 3', when the angle difference is .3 degrees.....
When I took college statistics, the professor passed around a small but info packed book called "how to lie with statistics." Once you read it you will be very skeptical of graphs, even very well designed ones such as Dr. Dave has posted. Since the graph is parabolic and is trending upward in squirt angle at both ends of the velocity plot, why use just a range of 3 to 8 mph? I need something to guage the speed of MY typical shot speeds in order to speak further, but do you see my point? parabolas can be logarithmic... so could the upward trend seen at 7-8 mph spike at a slightly higher velocity? 0.3 degrees of angle difference seems small, but on big tables with small pockets, the right contact point could be fractions of millimeters and that angle difference might mean something over the length of a table. I like to pinch balls at a distance, but I like to use as much speed as possible to cinch the shot, so for a player who shoots my style could really use more info here...... Does Dr. Dave have a table of angles overlaying points on a 9' table? I think I will get some measuring equipment, like a big protractor, to check out the difference in contact point on an average shot for me, say 3', when the angle difference is .3 degrees.....
I'll have to back-pedal some since you're certainly right about a 0.3 degree difference being very significant (even 0.2 or 0.1). Nice catch.
I don't know about the table of angles corresponding to ball positions, but I might be able to save you some trouble, depending on how much work you've done thus far. It's easy enough to calculate the difference in the object ball's direction as the result of a difference in cueball direction of x-degrees (ignoring throw and other more minor effects).
So, if the balls are 3' (36") between centers, the following errors in OB direction (in degrees) occur at the intended cut angles from a 0.3 degree error in CB direction. The first number is for a +0.3 deg. error, the second for a -0.3 deg. error.
Three-quarter ball hit (14.48 deg. cut) : 4.72, -4.60
Half-ball hit (30 deg. cut) : 5.41, -5.09
Quarter-ball hit (48.59 deg. cut) : 7.59, -6.50
Obviously, a lot of shots (most) will be missed if you're off by that much.
The figures for +0.2/-0.2 errors in CB direction are:
Three-quarter ball hit: 3.14, -3.08
Half-ball hit: 3.57, -3.43
Quarter-ball hit: 4.90, -4.42
I think you can say nearly the same thing about those numbers as well; you're going to miss an awful lot of shots.
Although Dr. Dave's tests dispel the "big myth" illustrated by his diagram, if the results are indicative of some true variation in squirt, it seems it could only be ignored at one's peril.
Again, excellent point. Now, is that a real variation in squirt???
Jim
Last edited:
What are the units?
Jim, I appreciate very much the offort you have put in your post. But to use it and understand it fully I need to know what units your numbers refer to. What I am looking for is variance in millimeter (distance) measurement of contact points for given distances. For example, if the cueball squirts .2 degrees, and you are aiming at the rail from 3 feet away, how many millimeters of error do you hit on the rail from your intented target? This information might verify what I have taught people all these years, that for each cue you play with, it is nice to find a speed that gives you a predictable amount of squirt so that aiming can be trusted with english. And if your speed is too low the tip won't grab the ball whereas if your speed is too fast the cueball may be pushed out of the way enough to cause a squirted, missed ball.
What are the units of the numbers you are giving me? Thanks so far....
Jim, I appreciate very much the offort you have put in your post. But to use it and understand it fully I need to know what units your numbers refer to. What I am looking for is variance in millimeter (distance) measurement of contact points for given distances. For example, if the cueball squirts .2 degrees, and you are aiming at the rail from 3 feet away, how many millimeters of error do you hit on the rail from your intented target? This information might verify what I have taught people all these years, that for each cue you play with, it is nice to find a speed that gives you a predictable amount of squirt so that aiming can be trusted with english. And if your speed is too low the tip won't grab the ball whereas if your speed is too fast the cueball may be pushed out of the way enough to cause a squirted, missed ball.
What are the units of the numbers you are giving me? Thanks so far....