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Fred Agnir
04-04-2005, 06:48 AM
Is there a graph of spin-induced throw based on cut angle somewhere?

Better yet, what cut angle has the most SIT? What has the least? How does a half-ball cut compare based on spin alone?

I'm trying to figure a few things out about aim-and-pivot. I use aim-and-pivot based on a full-ball hit. But, since I don't take SIT into consideration (because I believe it to be too small for me to give a crap on clean equipment), I use the same pivot point across the range of cut angles. I am rethinking that. I think that since there's virtually no SIT on a very thin cut, then the pivot point must be longer for those shots. That is, the pivot point should be a pivot range.

For all intents and purposes, I think I can treat the range as linear (pp vs. cut angle). just want to be sure nothing funky happens at half-ball (since there is CIT).

Fred

larrynj1
04-04-2005, 07:45 AM
fred, you can probably find what you're looking for in koehler's science of pocket billiards.

SpiderMan
04-04-2005, 08:20 AM
Fred,

I think there are a number of variables complicating "aim-and-pivot", AKA "back-hand english". For example, you could also add the dimension of amount of tip offset. I seem to notice a shift in pivot point as a function of the amount of english.

Have you seen an analytic model that would predict this?

SpiderMan

dr_dave
04-04-2005, 08:30 AM
<blockquote><font class="small">Quote larrynj1:</font><hr> fred, you can probably find what you're looking for in koehler's science of pocket billiards. <hr /></blockquote>
Fred,

Koeheler has a plot on page 74. However, I'm not sure his curves are based on experiments, because the "No English" curve seems to disagree with Bob's plot (http://www.sfbilliards.com/throw.gif). Also, Koehler doesn't show the effect of speed in his graph. However, Koehler's curves do illustrate what one would expect to see:

- Spin-induced throw (SIT) is maximum for a straight-on shot (i.e., 0 degree cut angle).

- Collision-induced throw (CIT) increases with cut angle (but as Bob has showed, only up to a certain point).

- Outside English can reduce, eliminate, or even reverse the effects of CIT.

Also, since friction decreases at higher speed, all throw (SIT and CIT) is larger at slower speeds.

For more information, see my previous message (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&amp;Board=ccb&amp;Number=172771&amp;page =&amp;view=&amp;sb=&amp;o=&amp;vc=1) dealing with the types of and causes for throw.

Regards,
Dr. Dave

Fred Agnir
04-04-2005, 08:58 AM
<blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote larrynj1:</font><hr> fred, you can probably find what you're looking for in koehler's science of pocket billiards. <hr /></blockquote>
Fred,

Koeheler has a plot on page 74. However, I'm not sure his curves are based on experiments, because the "No English" curve seems to disagree with Bob's plot (http://www.sfbilliards.com/throw.gif). Also, Koehler doesn't show the effect of speed in his graph. However, Koehler's curves do illustrate what one would expect to see:

- Spin-induced throw (SIT) is maximum for a straight-on shot (i.e., 0 degree cut angle).
<hr /></blockquote>Okay, thanks Dave. Maybe one of these days I'll actually look at Koehler's book. Is the graph for SIT linear?

Fred

dr_dave
04-04-2005, 09:18 AM
<blockquote><font class="small">Quote Fred Agnir:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote larrynj1:</font><hr> fred, you can probably find what you're looking for in koehler's science of pocket billiards. <hr /></blockquote>
Fred,

Koeheler has a plot on page 74. However, I'm not sure his curves are based on experiments, because the "No English" curve seems to disagree with Bob's plot (http://www.sfbilliards.com/throw.gif). Also, Koehler doesn't show the effect of speed in his graph. However, Koehler's curves do illustrate what one would expect to see:

- Spin-induced throw (SIT) is maximum for a straight-on shot (i.e., 0 degree cut angle).
<hr /></blockquote>Okay, thanks Dave. Maybe one of these days I'll actually look at Koehler's book. Is the graph for SIT linear?<hr /></blockquote>
You're welcome. None of the curves are linear over the whole range. However, the SIT curves are shown falling off fairly quickly and close to linearly as cut angles increase from 0 to 30 degrees. Beyond 30 degrees, the inside English SIT effect is shown to not add to the CIT effect, and the outside English effect is shown to become less strong. This is tough to describe with words, but easy to see with a picture. If you don't have his book already, you should get a copy. It is very good.

Regards,
Dave

BlindPlayer
04-04-2005, 11:17 AM
I know this is off the subject of "this" thread but I'm new to this site and how do I post and originate a new thread?

And what does LOL, and BTW mean? Help....

Fred Agnir
04-04-2005, 11:42 AM
<blockquote><font class="small">Quote BlindPlayer:</font><hr> I know this is off the subject of "this" thread but I'm new to this site and how do I post and originate a new thread?

And what does LOL, and BTW mean? Help.... <hr /></blockquote>On the discussion page (the one that shows all the subject threads in the forum) there is a <font color="blue">blue POST </font color> link that you click.

LOL: Laugh Out Loud
BTW: By the way
FL: Fast Larry

Internet Abbreviation Search (http://www.google.com/search?sourceid=navclient&amp;ie=UTF-8&amp;rls=DVXA,DVXA:2005-10,DVXA:en&amp;q=internet+abbreviations)

Fred

BlindPlayer
04-04-2005, 11:55 AM
FL? Fast Larry? You meand "Fast Larry" Guninger? He and I have been cooresponding and after the BCA gig in Las Vegas (7th-12th) he's coming to Sacramento for our first face to face meeting.

Can't wait - we'll do lunch and maybe shoot some, wow.

Rod
04-04-2005, 08:47 PM
It "all" matters including tip offset. Haven't a clue about a graph though. Tommorrow I'll be giving a clinic, the very basics of BIH will be discussed. Myself I don't use aim and pivot, I use it on the fly. However to keep it easier, aim and pivot will be used without going into great detail. I'll obviously spend more time on stroke because without that none of the above matters anyway.

You know when anyone talks about this stuff were assuming a great deal. You hit the c/b and the o/b where intended.

Rod

Fred Agnir
04-05-2005, 06:41 AM
<blockquote><font class="small">Quote Rod:</font><hr> It "all" matters including tip offset. Haven't a clue about a graph though. Tommorrow I'll be giving a clinic, the very basics of BIH will be discussed. <hr /></blockquote>I assume you meant BHE.

Fred

Rod
04-05-2005, 08:18 AM
Thanks Fred, yes I did.

Rod

dr_dave
04-05-2005, 08:38 AM
<blockquote><font class="small">Quote Fred Agnir:</font><hr> <blockquote><font class="small">Quote Rod:</font><hr> It "all" matters including tip offset. Haven't a clue about a graph though. Tommorrow I'll be giving a clinic, the very basics of BIH will be discussed. <hr /></blockquote>I assume you meant BHE.<hr /></blockquote>
For the newcomers out there that don't know what all these letters mean,

BIH: ball in hand
BHE: back hand English

Other acronym info can be found in another thread (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&amp;Board=ccb&amp;Number=172855&amp;page =&amp;view=&amp;sb=&amp;o=). I am not encouraging acronym use, because I think it can get Out Of Hand (OOH); but if you see some letters you don't understand, now you know where to go.

Regards,
Dr. Dave

cushioncrawler
10-23-2005, 05:22 PM
I woz reading Dr Dave'z comment that SIT iz at a max for a full ball contact, &amp; it suddenly occurred to me that actually SIT iz nearnuff constant for all contacts, at least it iz in MathLand.
MathLand must giv way to RealLand, but at the moment i am in the bush &amp; surrounded by kangarooz &amp; am 3 hourz away from my copy of Koehler. Anyhow, az Dr Dave sez, Koehler iz possibly in MathLand in relation to this matter.
Anyhow, i reckon that u can get a throw angle of say 1 in 20 for any &amp; all contacts.
Re throw, Arithmetik tellz me that throw iz maximized when all ball-to-ball slippage fallz to zero at the same time az when the ballz part company. This meanz that too much sidespin actually reducez the throw.
Hence, for a Qball with pure stun, i reckon that the throw iz at a max when the contact iz a little thicker than 3/4 ball (ie 12.5 sixteenths). Thicker than this &amp; the ball-to-ball slippage stops before the ballz part. Thinner than this, &amp; there iz slippage remaining when the ballz part.
For a Qball with pure rolling, the throw iz of course in some instancez only about a half of what can be achieved uzing stun. But what i wanted to say iz that, i reckon that, for pure rolling throw iz at a max when the contact iz a little thicker than 1/4 ball (ie 5.7 sixteenths).
When i/we say Throw, of course i/we all mean the horizontal component of throw, the vertical component being wasted in this sort of context -- which iz why we get such a large difference between stun &amp; rolling.
Re friktion, i reckon that friktion iz nearnuff constant at all impakt speedz. Here i am talking about True Friktion. However, the greater the impakt speed the larger the temporary impakt flatspot, the larger the flatspot the greater the Flatspot Sqeez. Flatspot Sqeez allwayz diminishez the cut angle, it givz u the impression that friktion iz less.
I wonder if any of this stuff iz usefull??? No!!!! Duzzenmadder.

dr_dave
10-24-2005, 07:37 AM
<blockquote><font class="small">Quote Fred Agnir:</font><hr> Is there a graph of spin-induced throw based on cut angle somewhere?

Better yet, what cut angle has the most SIT? What has the least? How does a half-ball cut compare based on spin alone?
<hr /></blockquote>
All graphs and answers to your questions can now be found in TP A.17 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/new/TP_A-17.pdf). For a list of conclusions and discussion, see the links under the first bullet under "throw" in the threads summary area of my website (http://www.engr.colostate.edu/~dga/pool/threads.html).

Regards,
Dave