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muddywaters
05-29-2006, 08:22 PM
Greetings
Perhaps someone would be kind enough to give me some guidance on the Tangent line rules?
I've recently began taking the game much more seriously and need to massively improve my position play aspect of the game.

I've spent a little time on http://www.engr.colostate.edu/~dga/pool/normal_videos/index.html

(Great site)

So in regards to the 90/ and the 30 degree rules -
The gentlemen says for the 30 degree one its "when the ball is moving?"

Could someone please take pity and explain to me when what rules should be taking place.

muddywaters
05-29-2006, 08:32 PM
hmmmmmmm searching the site and i might have found the answer to my questions...........sorry.
Im looking for some sort of idiots guide to pool!

pigbrain
05-29-2006, 09:54 PM
cut angle not too large not too small.
the cueball is natural rolling while aproaching the object ball.

Jal
05-29-2006, 10:17 PM
<blockquote><font class="small">Quote muddywaters:</font><hr>...Im looking for some sort of idiots guide to pool! <hr /></blockquote>http://www.amazon.com/gp/product/1592572871/102-2617756-8192166?v=glance&amp;n=283155

In my opinion, one of the better books on pool.

Jim

Scott Lee
05-29-2006, 10:26 PM
muddywaters...Here's the easy answer. Any sliding CB will bounce off of, or deflect off of, the OB at a right angle (90 degrees). Sidespin will have no appreciable effect on the tangent line, unless the CB has forward roll or backspin, in addition to the sidespin (english), at the point of contact with the OB. This is most easily demonstrated by placing an OB on the footspot, and shooting the ball into a corner pocket with any angle. If the CB slides into the OB, the CB should scratch in the side pocket. If it doesn't, you're either not sliding the CB into the OB (missing exact center on the CB), or the CB is rolling by the time it gets to the OB.

Scott Lee

dr_dave
05-30-2006, 06:24 AM
<blockquote><font class="small">Quote pigbrain:</font><hr> cut angle not too large not too small.
the cueball is natural rolling while aproaching the object ball. <hr /></blockquote>
Others have provided some good answers below. If you want more detail, illustrations, and lots of examples, see my collection of instructional articles (http://www.engr.colostate.edu/~dga/pool/bd_articles/index.html) and/or my book. I have 12 articles posted dedicated to this topic! My July '04 article (http://www.engr.colostate.edu/~dga/pool/bd_articles/july04.pdf) contains a good summary for both principles. There are also many useful links to pertinent postings and threads here (http://www.engr.colostate.edu/~dga/pool/threads.html).

Dave

Billy_Bob
05-30-2006, 11:03 AM
Many players do not realize it, but when hitting the cue ball with a center hit or slightly below center, the cue ball "slides"! The cue ball is not "rolling", but is "sliding!

This is *very* important!

Some "wiz bang rocket scientist type" figured out that a "rolling" cue ball will come off of the object ball at 30 degrees from the line of the shot to the object ball.

*and*

This person figured out that a "sliding" cue ball will come off the object ball 90 degrees to where the object ball is being shot to - 90 degrees to the pocket - or tangent.

So why is this so important?

Because you can shoot the cue ball one way or the other to avoid a scratch! You can deliberately change the direction the cue ball goes after hitting the object ball!

This is good stuff!

And with advanced playing, you can make the cue ball go where it will be most handy for the next shot by using one of the above.

What got all this to sink into my brain was seeing Dr. Dave's video where he demonstrates the 30 and 90 degree rule shots. Something went "ding!" in my brain. Reading about it did not make me realize how handy this information was. I didn't "get it".

(FYI - get his DVD here...)
http://www.engr.colostate.edu/~dga/pool/cd_dvd/dvd_description.html

For "seeing" a sliding ball, use a striped ball instead of the cue ball. Also you can get one of those "measles" balls if you have your own table. You can then see what the cue ball is doing. Rolling, sliding, or rolling backwards if using draw.

Also if it is a long shot, to get the ball to "slide" when it hits the object ball, you need to shoot a draw shot. The cue ball initially rolls backwards, then slides, then begins a forward roll. Practice long draw shots with a striped ball (no object ball) and watch what the ball is doing.

Then set up a cut shot (cue ball about 12 inches from object ball) and mark the spots on the table so you can shoot the same exact shot over and over. Use a striped ball for the cue ball. Shoot the shot with a sliding ball (called stun) hit slightly below center. Then see where "striped" cue ball goes after the hit. Then shoot the same exact shot with a rolling cue ball. Hit the cue ball above center or high. See where the cue ball goes now...

Billy_Bob
05-30-2006, 11:16 AM
Here is a high speed video showing how a cue ball "slides"...
http://www.engr.colostate.edu/~dga/pool/high_speed_videos/new/HSVA-55.htm

A "forward rolling" cue ball by hitting high...
http://www.engr.colostate.edu/~dga/pool/high_speed_videos/new/HSVA-46.htm

A "backwards rolling" cue ball by hitting low...
http://www.engr.colostate.edu/~dga/pool/high_speed_videos/new/HSVA-38.htm

I don't see a normal video of a "draw drag" shot. This is where the cue ball initially has a backward spin, then begins to slide.

Bob_Jewett
05-30-2006, 12:07 PM
<blockquote><font class="small">Quote Billy_Bob:</font><hr> ... Some "wiz bang rocket scientist type" figured out that a "rolling" cue ball will come off of the object ball at 30 degrees from the line of the shot to the object ball.<hr /></blockquote>

It's important to realize that the angle is not 30 degrees and can in fact appear to be 45 degrees depending on speed and some other stuff. I think the theory behind the half-ball angle was discovered in the 1700's.

[ QUOTE ]

This person figured out that a "sliding" cue ball will come off the object ball 90 degrees to where the object ball is being shot to - 90 degrees to the pocket - or tangent.<hr /></blockquote>

I think the nod here goes to Newton, which would put it in the 1600's, probably. I don't think Newton worked out the half-ball angle.

I'm surprised you didn't mention the easy way you can get an accurate cue ball angle for all fullnesses of hit -- even 1/8- or 7/8-full hits where the half-ball rule is useless.

Billy_Bob
05-31-2006, 02:09 PM
<blockquote><font class="small">Quote Bob_Jewett:</font><hr> ...I'm surprised you didn't mention the easy way you can get an accurate cue ball angle for all fullnesses of hit -- even 1/8- or 7/8-full hits where the half-ball rule is useless. <hr /></blockquote>

What way is that? (I'm still working on the 30/90 stuff...)

dr_dave
05-31-2006, 02:47 PM
<blockquote><font class="small">Quote Billy_Bob:</font><hr>I don't see a normal video of a "draw drag" shot. This is where the cue ball initially has a backward spin, then begins to slide.<hr /></blockquote>
HSV 3.1 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/HSV3-1.htm) shows the effect quite clearly in super-slow-motion.

Regards,
Dave

Bob_Jewett
05-31-2006, 05:48 PM
<blockquote><font class="small">Quote Billy_Bob:</font><hr> <blockquote><font class="small">Quote Bob_Jewett:</font><hr> ...I'm surprised you didn't mention the easy way you can get an accurate cue ball angle for all fullnesses of hit -- even 1/8- or 7/8-full hits where the half-ball rule is useless. <hr /></blockquote>

What way is that? (I'm still working on the 30/90 stuff...)
<hr /></blockquote>
For any shot that you are playing with a rolling cue ball, place your stick along the tangent (kiss) line which is perpendicular to the path of the object ball and through the center of the ghost ball with your tip at the center of the ghost ball. Drop a perpendicular from the cue ball to your cue stick (in your imagination). Put your finger on that line 1/4th of the way from your stick to the cue ball. Pivot the stick about the center of the ghost ball (it's tip) so it meets your finger. The cue ball will follow the line your stick is pointing.

Some comments: The cue ball has to be rolling smoothly, just like for the half-ball rule. I find this system more useful for relatively thin hits. The factor of 1/4 is actually 2/7 in theory, but 1/4 is close enough, it's easier to estimate and it compensates for friction and some other things.

Two other ways of figuring out the path are in the article:

http://www.sfbilliards.com/articles/1998-12.pdf

Billy_Bob
06-01-2006, 08:30 AM
Thanks Bob!

Sometimes I need to know exactly where the cue ball will go after the hit. Will it hit that other ball over there or miss it and hit the rail? Will I need more speed if it is going to hit that ball or less speed it it is going to hit the rail? Etc.

So I will try this as well as the finger calibration thing. See if I can get to be more accurate on my "predicting"...

Stretch
06-01-2006, 08:53 AM
<blockquote><font class="small">Quote Billy_Bob:</font><hr> Thanks Bob!

Sometimes I need to know exactly where the cue ball will go after the hit. Will it hit that other ball over there or miss it and hit the rail? Will I need more speed if it is going to hit that ball or less speed it it is going to hit the rail? Etc.

So I will try this as well as the finger calibration thing. See if I can get to be more accurate on my "predicting"...
<hr /></blockquote>

Billy Bob, yes the applications are endless. Caroms, breakouts, safe lane travel, avoiding scratches, all become very doable. I can't think of any other piece of " advice" that has such an immediate impact to ones game as the 90% rule, and the half ball hit. For learning to control the stun shots down the line all you need to do is master the stop shot at different speeds and distances. I play a stunshot the same way as i would play the stop shot. It's the angle that moves the cue ball. Soft stopshot=short travel down line, Hard stopshot=long distance down the line. St.

muddywaters
06-05-2006, 08:53 PM
Well gentlemen i thank you for all the great advice -
I've so far discovered two items since my original post and was able to venture out to test the tangent line rules -

- I think i have an understanding of the rolling ball.......IF the ball is rolling then it would be a 30 degree........non rolling ball 90 degree angle.

This has actually helped me alot, i began to realize the natural paths and as a result i haven't scratched since.....
However
Perhaps it is my stroke - but i have yet to be able to get a precise feel for where the ball will end up. ( i am generally a feel type o player, don't use aiming systems &amp; whatnot....so precise being the desired effect)

What i did was to set up a shot, and place another object ball up against the rail on where the QB would end up.........i always seemed to be a ball or two in front or behind.....any ideas?

While im here.........this might be used for a separate thread but i will ask anyways.

Moving the ball shape wise form one end of the table to the other i am quiet confident with. Where i find a problem is when there are say four five balls to clear on one side of the table.
I keep reading about recognizing paths on the table that keep reoccurring &amp; repeating.
Does anyone know of a drill to help? or perhaps a different outlook on how to attack the shape?. I tend to send the ball to the other end of the table and have to make a harder shot then necessary.

Jal
06-05-2006, 11:16 PM
<blockquote><font class="small">Quote muddywaters:</font><hr> Well gentlemen i thank you for all the great advice -
I've so far discovered two items since my original post and was able to venture out to test the tangent line rules -

- I think i have an understanding of the rolling ball.......IF the ball is rolling then it would be a 30 degree........non rolling ball 90 degree angle.

This has actually helped me alot, i began to realize the natural paths and as a result i haven't scratched since.....
However
Perhaps it is my stroke - but i have yet to be able to get a precise feel for where the ball will end up. ( i am generally a feel type o player, don't use aiming systems &amp; whatnot....so precise being the desired effect)

What i did was to set up a shot, and place another object ball up against the rail on where the QB would end up.........i always seemed to be a ball or two in front or behind.....any ideas?<hr /></blockquote>If there were a simple answer to this, about half the challenge of playing pool would be removed. There are many possible paths the cueball can take, depending mainly on cut angle, speed, and how much topspin or draw the cueball has on it as it reaches the object ball. Knowing how to control the amount of spin for any given cut angle and shot speed is where experience comes in. It is possible to determine, with a little geometry, what the final direction of the cueball will be for other than stun or natural roll shots which follow the 90 and 30 degree rules. But you still have to know just how much spin the cueball will have at impact to apply it, which more or less negates its usefulness. That requires table time to acquire a feel.

You'll never be perfect, though. Watch just about any tournament match and you're likely to see a pro misjudge this enough to end up in a difficult situation.

<blockquote><font class="small">Quote muddywaters:</font><hr>While im here.........this might be used for a separate thread but i will ask anyways.

Moving the ball shape wise form one end of the table to the other i am quiet confident with. Where i find a problem is when there are say four five balls to clear on one side of the table.
I keep reading about recognizing paths on the table that keep reoccurring &amp; repeating.
Does anyone know of a drill to help? or perhaps a different outlook on how to attack the shape?. I tend to send the ball to the other end of the table and have to make a harder shot then necessary. <hr /></blockquote>It's not completely clear what the problem is, but it sounds like shooting softer might be the solution. The only time you really can't avoid sending the ball down table (and hopefully back again if needed) is when you have a fairly severe cut angle which has the cueball rebounding off the end cushion. Otherwise, reigning in your shot speed should pretty much remedy this. Avoiding other balls as much as possible so that you don't carom off of one also helps.

Jim

Cornerman
06-06-2006, 05:46 AM
<blockquote><font class="small">Quote muddywaters:</font><hr> Moving the ball shape wise form one end of the table to the other i am quiet confident with. Where i find a problem is when there are say four five balls to clear on one side of the table.
I keep reading about recognizing paths on the table that keep reoccurring &amp; repeating.
Does anyone know of a drill to help? or perhaps a different outlook on how to attack the shape?. I tend to send the ball to the other end of the table and have to make a harder shot then necessary. <hr /></blockquote>What game are you talking about?

Fred

TennesseeJoe
06-06-2006, 07:03 AM
The 30/90 degree rule is Newton's 4th law. Up till now this has been highly confidential but will soon be revealed to the general public in "The Da Vinci Code II"

Billy_Bob
06-06-2006, 08:40 AM
What my experience has been was to first learn the 30/90 degree rules. Then I almost instantly stopped scratching as you have done.

Then over the next year and a half, I have just been "thinking" about where the CB will go after my shot. Trying to predict and see what happens. I am slowly getting better at being able to leave the CB where I want.

I can also learn this by watching very good players play. Watch where they are hitting the CB, then see where the CB goes after the shot.

What might help to understand what is possible is to get the Jim Rempe training ball. There are little lines on this ball. Set up a slight cut shot into a side pocket, CB about 12 inches back from the object ball. Mark the exact placement of the balls. Then keep shooting the object ball into the side pocket. Start with dead center, then move up one line on the training ball (follow), then next line, then next. Also go down (draw), down a line, down to next line, etc.

Basically the cue ball will wind up going to different locations on the surrounding rails sort of like spokes on a wagon wheel. Actually the person who showed me this drill called it the "wagon wheel".

So far as knowing *exactly* where the cue ball will go, I am still having trouble with this, but every once in a great while (with more and more experience), I can tell with some shots exactly where it will go. But then I still have trouble! Last night I knew exactly the line the CB would go in, but I shot slightly too hard. The CB went the exact direction I predicted, but went 2 inches too far because of too much speed. But that is what makes all of this so much fun. Trying to do these things.

So far as a lot of balls at one end of the table (all my balls to shoot in). I think I use everything in my "arsenal" to shoot all the balls in and get position for my next shots. Tons of experience messing it up helps! Follow, draw, speed control, english, 30/90 degree rules, and knowing *which* ball to shoot first. This is the key, which ball to start with. Where will CB go after that? And where do you want to leave the CB to get on the shot after that? Got to think several balls ahead.

I think I will have years and years of fun trying to leave the cue ball where I am trying to leave it. Endless amounts of challenge...