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av84fun
02-15-2008, 01:25 AM
There is significant debate about the new World Standard Rules...and the old ones...and other rule sets for that matter...on the issue of what type of shot is legal/illegal when the CB and OB are frozen.

One camp states that even if you shoot straight through with a normal stroke...not an intentional "push shot"... the tip does not remain on the CB any longer than it would reamin there if there was no frozen OB.

Is anyone aware of any slow motion video or other scientific means of determining what actually happens on such shots?

Thanks!

Jim

catscradle
02-15-2008, 09:06 AM
<blockquote><font class="small">Quote av84fun:</font><hr> There is significant debate about the new World Standard Rules...and the old ones...and other rule sets for that matter...on the issue of what type of shot is legal/illegal when the CB and OB are frozen.

One camp states that even if you shoot straight through with a normal stroke...not an intentional "push shot"... the tip does not remain on the CB any longer than it would reamin there if there was no frozen OB.

Is anyone aware of any slow motion video or other scientific means of determining what actually happens on such shots?

Thanks!

Jim <hr /></blockquote>
I think "The Jacksonville Study" done by Bob Jewett et. al. showed that conclusively. You could get the video and supporting study from Bob, I don't know if you still can. I think the problem comes because a double hit occurs.
Steve.

mikepage
02-15-2008, 12:28 PM
Where is the "significant debate"? I suspect Dave A. has video of this as well.

Here is, at least approximately, the expectation. If we think of the tip-ball interaction as being harmonic (i.e., like a spring), then we can estimate the effect of the extra ball on the tip-ball contact time.

The actual collision will not obey Hooke's law but instead will obey something closer to Hertz's law. And in addition the collision is somewhat inelastic.

But these things aside the contact time will vary as the square root of the reduced mass,

(Mb * Ms)/(Mb + Ms)

When the mass of the ball gets doubled, the contact time should increase by 5% or so. This deviation is smaller than the change of contact time when you switch tips or go from centerball to a spinshot.

We have Jay H. on the other group who just doesn't like frozen-ball shots being allowed (kind of a nostalgia thing it seems). But other than that is there a controversy?


<blockquote><font class="small">Quote av84fun:</font><hr> There is significant debate about the new World Standard Rules...and the old ones...and other rule sets for that matter...on the issue of what type of shot is legal/illegal when the CB and OB are frozen.

One camp states that even if you shoot straight through with a normal stroke...not an intentional "push shot"... the tip does not remain on the CB any longer than it would reamin there if there was no frozen OB.

Is anyone aware of any slow motion video or other scientific means of determining what actually happens on such shots?

Thanks!

Jim <hr /></blockquote>

av84fun
02-15-2008, 12:31 PM
<blockquote><font class="small">Quote catscradle:</font><hr> <blockquote><font class="small">Quote av84fun:</font><hr> There is significant debate about the new World Standard Rules...and the old ones...and other rule sets for that matter...on the issue of what type of shot is legal/illegal when the CB and OB are frozen.

One camp states that even if you shoot straight through with a normal stroke...not an intentional "push shot"... the tip does not remain on the CB any longer than it would reamin there if there was no frozen OB.

Is anyone aware of any slow motion video or other scientific means of determining what actually happens on such shots?

Thanks!

Jim <hr /></blockquote>
I think "The Jacksonville Study" done by Bob Jewett et. al. showed that conclusively. You could get the video and supporting study from Bob, I don't know if you still can. I think the problem comes because a double hit occurs.
Steve. <hr /></blockquote>

I couldn't find any references in articles about the Jacksonville Experiment to issues related to FROZEN CB/OBs...only to shots where the CB/OB are very close together.

Bob is part of the discussion on AZ that prompted my post here. Unless I misunderstood his comments (very possible) it doesn't seem that frozen ball issues were tested.

Regards,
Jim

Fran Crimi
02-15-2008, 02:00 PM
<blockquote><font class="small">Quote av84fun:</font><hr> There is significant debate about the new World Standard Rules...and the old ones...and other rule sets for that matter...on the issue of what type of shot is legal/illegal when the CB and OB are frozen.

One camp states that even if you shoot straight through with a normal stroke...not an intentional "push shot"... the tip does not remain on the CB any longer than it would reamin there if there was no frozen OB.

Is anyone aware of any slow motion video or other scientific means of determining what actually happens on such shots?

Thanks!

Jim <hr /></blockquote>


I think that the most important thing to be considered when writing rules is the practicality factor. Can the rule be enforced with the naked eye?

If it were determined that yes, in fact it is a double hit if a push occured when the cue and object ball were frozen, then the question that needs to be answered is---Can a referee or player determine with his naked eye at what point it is no longer a double hit?

I was around back when they changed that rule. I don't know exactly when but I know it was when everyone was still playing 14.1 as the main competitive game. I don't think that anyone was disputing whether or not it was a double hit. I think most if not all, thought it was. It was determined that it was too difficult to try to determine with the naked eye at what point it wasn't a double hit or a foul. You can't say things like: shooting at a 30 degree angle, for example, is no longer a double hit, (just an arbitrary statement) when a game is in progress. It's meaningless to the players and ref as the action is taking place.

Sometimes, you have to sacrifice total accuracy for practicality.

Fran

Jal
02-15-2008, 02:11 PM
<blockquote><font class="small">Quote av84fun:</font><hr> ...Is anyone aware of any slow motion video or other scientific means of determining what actually happens on such shots?<hr /></blockquote>Dr. Dave has some here (see HSV A.97):

http://billiards.colostate.edu/high_speed_videos/index.html

To my eyes, the upper limit for the contact time is about 3 milliseconds. It could be, and probably is, significantly less (see Mike Page's post).

If you were to determine the pre-impact speed of the cue off these videos, a more restricted upper-limit might be deduced from the contacted ball's speed component perpendicular to the line of centers of the two balls.

Jim

Bob_Jewett
02-15-2008, 02:53 PM
<blockquote><font class="small">Quote av84fun:</font><hr> ... Is anyone aware of any slow motion video or other scientific means of determining what actually happens on such shots? ... <hr /></blockquote>
Besides Dr. Dave's videos, all of the Jacksonville Project tape is now up on the AZBTV site under "technical" material.

Some seem to be worried about the clause mentioning deliberately increased contact time. I find, in general, that such people have only a murky or non-existent understanding of push shots and why this clause applies to them. They also have no understanding of how contact time increases for shot speed, tip hardness, elevation of the stick and eccentricity of hit.

(Warning: here "push shot" is used in the sense of the current rules and not in the way your Uncle Joe told you. If you have a question about that, please begin by reading the current rules. It will take most people a couple of readings to get familiar with them, since rules refer to others.)

Normal shots have contact times maybe in the 0.5 to 3ms range for normal types of tips, speeds, and spins. This includes shooting towards a frozen ball.

Bob_Jewett
02-15-2008, 03:13 PM
<blockquote><font class="small">Quote Fran Crimi:</font><hr> ... if a push occured ... <hr /></blockquote>
For those trying to make sense of all of this, Fran is not using the word "push" as it is used in the current rules.

av84fun
02-15-2008, 04:50 PM
Bob made it all clear over on AZ. Shooting straight into frozen CB/OBs is both legal in the WSRs and does not cause a double hit according to the Jacksonville Experiments.

It's on the Jacksonville Tape, somewhere. The Jacksonville Tape is now up on the AZBTV www.azbtv.com (http://www.azbtv.com) under the "technical" section. I'm not sure at what time the frozen ball shots occur. I'll briefly summarize the conclusions from the tape and simple analysis:

When shooting towards a frozen ball, there is only one tip-to-ball contact.

The balls leave together and leave the tip behind.

The stick slows at contact more than for a normal shot, but does not stop dead.

(The contact time is slightly longer, but I think there was no Jacksonville sequence that shows this directly. See mikepage's note for an explanation.)

(A consequence of the equal "forward" speeds of the two balls is the "two times fuller" system for shooting towards frozen balls.)

av84fun
02-15-2008, 04:52 PM
Mike..."We have Jay H. on the other group who just doesn't like frozen-ball shots being allowed (kind of a nostalgia thing it seems). But other than that is there a controversy?"

That was the controversy I was referring to. I referred to it as "significant" due to the number of posts on AZ and because Jay is a respected person in the pool world.

Regards,
Jim

Fran Crimi
02-15-2008, 05:00 PM
<blockquote><font class="small">Quote Bob_Jewett:</font><hr> <blockquote><font class="small">Quote Fran Crimi:</font><hr> ... if a push occured ... <hr /></blockquote>
For those trying to make sense of all of this, Fran is not using the word "push" as it is used in the current rules. <hr /></blockquote>

Correct. I was using it the way my Uncle Joe taught me before somebody decided to change the meaning.

Fran

dr_dave
02-15-2008, 05:08 PM
FYI,

Here are some clips that illustrates the conclusion summary quite well:

HSV A.96 - straight-on frozen cue ball shots with various English (http://billiards.colostate.edu/high_speed_videos/new/HSVA-96.htm)

HSV A.97 - frozen cue ball shots with various approach angles (http://billiards.colostate.edu/high_speed_videos/new/HSVA-97.htm)

I also have an analysis of Bob's and my systems for aiming these shots, along with a comparison to experimental data from the high-speed video shots. Here it is:

TP A.15 - Controlling the cue ball direction in a frozen push shot (http://billiards.colostate.edu/technical_proofs/new/TP_A-15.pdf)

Regards,
Dave

PS: Thank you for sharing the AZBilliards discussion results here. Not all of us visit that "other" forum.

<blockquote><font class="small">Quote av84fun:</font><hr>It's on the Jacksonville Tape, somewhere. The Jacksonville Tape is now up on the AZBTV www.azbtv.com (http://www.azbtv.com) under the "technical" section. I'm not sure at what time the frozen ball shots occur. I'll briefly summarize the conclusions from the tape and simple analysis:

When shooting towards a frozen ball, there is only one tip-to-ball contact.

The balls leave together and leave the tip behind.

The stick slows at contact more than for a normal shot, but does not stop dead.

(The contact time is slightly longer, but I think there was no Jacksonville sequence that shows this directly. See mikepage's note for an explanation.)

(A consequence of the equal "forward" speeds of the two balls is the "two times fuller" system for shooting towards frozen balls.)<hr /></blockquote>

Fran Crimi
02-15-2008, 05:13 PM
[ QUOTE ]
also have an analysis of Bob's and my systems for aiming these shots, along with a comparison to experimental data from the high-speed video shots. Here it is:

TP A.15 - Controlling the cue ball direction in a frozen push shot

Regards,
Dave
<hr /></blockquote>

Dave, were you using the words "push shot" in accordance with the new rules or are you using Uncle Joe's definition?
/ccboard/images/graemlins/grin.gif

Fran

dr_dave
02-15-2008, 05:26 PM
<blockquote><font class="small">Quote Fran Crimi:</font><hr><blockquote><font class="small">Quote dr_dave:</font><hr>also have an analysis of Bob's and my systems for aiming these shots, along with a comparison to experimental data from the high-speed video shots. Here it is:

TP A.15 - Controlling the cue ball direction in a frozen push shot<hr /></blockquote> Dave, were you using the words "push shot" in accordance with the new rules or are you using Uncle Joe's definition?
/ccboard/images/graemlins/grin.gif<hr /></blockquote>Fran,

I thought you might pick up on that, given your recent "interaction" with Bob.

I think I'm using "Uncle Joe's" definition, but I haven't read the new rules in detail yet.

I still like to refer to this as a "legal push shot," but I can see Bob's point that it really isn't a "push" (in the illegal sense of the term).

Regards,
Dave

Bob_Jewett
02-15-2008, 05:58 PM
<blockquote><font class="small">Quote av84fun:</font><hr> ... I referred to it as "significant" due to the number of posts on AZ and because Jay is a respected person in the pool world. ... <hr /></blockquote>
I wish he understood more about the rules.

av84fun
02-15-2008, 10:46 PM
<blockquote><font class="small">Quote Bob_Jewett:</font><hr> <blockquote><font class="small">Quote av84fun:</font><hr> ... I referred to it as "significant" due to the number of posts on AZ and because Jay is a respected person in the pool world. ... <hr /></blockquote>
I wish he understood more about the rules. <hr /></blockquote>

He understands the rules...he just doesn't agree with this one based on his experience which leads him to believe that "unfair" manipulations can be imposed by that shot.

I am fine with the rule but not on scientific grounds. Rather, it comes up so infrequently that I think any reasonable rule is fine.

As an contributing author of the WSRs you know better than most that rulemaking can easily descend into legislative overkill which should be avoided even at the risk of permitting shots that might be shown to be problematic at 12,000 frames per second.

Regards,
Jim

Alfie
02-16-2008, 01:21 AM
<blockquote><font class="small">Quote dr_dave:</font><hr> a "legal push shot," <hr /></blockquote>a legal illegal shot??
much too ambiguous, imo
/ccboard/images/graemlins/grin.gif

dr_dave
02-16-2008, 09:18 AM
<blockquote><font class="small">Quote Alfie:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> a "legal push shot," <hr /></blockquote>a legal illegal shot??
much too ambiguous, imo
/ccboard/images/graemlins/grin.gif <hr /></blockquote>Agreed. However, I still think a frozen cue ball shot is a "push" shot. It certainly has the "feel" and "look" of a "push." Maybe the rules should distinguish between a "legal frozen-CB push" and an "illegal intentional push."

I personally think this shot should not be allowed. I think the CB should be required to come off the OB in the tangent-line direction, like the pool physics gods intended. In other words, I don't think you should be allowed to shoot "into" a frozen CB shot. If your opponent put you there, you should be required to shoot away into a kick. If you put yourself there, you shouldn't be allowed an easy way out. Maybe the rules committee can consider this next time around.

One problem with a frozen CB "push" is it is difficult (impossible) to tell (through observation) how much the CB is actually being "pushed."

Regards,
Dave

av84fun
02-21-2008, 11:12 PM
mikepage...I guess Mike isn't around anymore but yet another poster on another forum chimed in on Jay's side of the debate.

He wrote:

"This illustration is a perfect example/reason why the frozen ball push shot should not be allowed. I have always played with the rules Jay described in reference to the frozen and almost frozen ball method of shooting. As long as you elevate executing back spin on the cue ball,resulting in the cue ball showing character,than in my opinion it's a legal shot,and it's also a shot representing dignity."

The poster's name is Bill Incardona whose views ought not to be dismissed as "nostalgic" any more than Jay's should be.

In fact, given the large number of threads across the forums and the heat that this subject seems to generate, I'm quite surprised that Mike wasn't aware of the controversy.

Regards,
Jim

randyg
02-22-2008, 06:46 AM
<blockquote><font class="small">Quote Fran Crimi:</font><hr> <blockquote><font class="small">Quote av84fun:</font><hr> There is significant debate about the new World Standard Rules...and the old ones...and other rule sets for that matter...on the issue of what type of shot is legal/illegal when the CB and OB are frozen.

One camp states that even if you shoot straight through with a normal stroke...not an intentional "push shot"... the tip does not remain on the CB any longer than it would reamin there if there was no frozen OB.

Is anyone aware of any slow motion video or other scientific means of determining what actually happens on such shots?

Thanks!

Jim <hr /></blockquote>


I think that the most important thing to be considered when writing rules is the practicality factor. Can the rule be enforced with the naked eye?

If it were determined that yes, in fact it is a double hit if a push occured when the cue and object ball were frozen, then the question that needs to be answered is---Can a referee or player determine with his naked eye at what point it is no longer a double hit?

I was around back when they changed that rule. I don't know exactly when but I know it was when everyone was still playing 14.1 as the main competitive game. I don't think that anyone was disputing whether or not it was a double hit. I think most if not all, thought it was. It was determined that it was too difficult to try to determine with the naked eye at what point it wasn't a double hit or a foul. You can't say things like: shooting at a 30 degree angle, for example, is no longer a double hit, (just an arbitrary statement) when a game is in progress. It's meaningless to the players and ref as the action is taking place.

Sometimes, you have to sacrifice total accuracy for practicality.

Fran <hr /></blockquote>

Absolutely the truth. The Rule was addressed and changed about 1985 by the BCA Rules Committee. Fran, I think you were part of that.......SPF=randyg