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dr_dave
04-05-2005, 01:51 PM
In a previous posting (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&Board=ccb&Number=168250&page =0&view=collapsed&sb=5&o=&vc=1), I explained how you can use a relaxed but firm peace sign (V-sign) to visualize and apply the 30 degree rule (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&Board=ccb&Number=168248&page =0&view=collapsed&sb=5&o=&fpart=1). See NV 3.8 (http://www.engr.colostate.edu/~dga/pool/normal_videos/NV3-8.htm) for a demonstration.

FYI, I just posted a new instructional article (June '05 article (http://www.engr.colostate.edu/~dga/pool/bd_articles/june05.pdf)) that wraps up a series of 12 (a year's worth!) of articles dealing with the 90 and 30 degree rules. In Diagram 2 of this article, I show how you should move your hand to adjust for speed. I've included a copy of the diagram below. It is fairly self-explanatory, but you can see the article (http://www.engr.colostate.edu/~dga/pool/bd_articles/june05.pdf) for more details. I hope some people can find this useful in their games. I use my 30-degree-rule-peace-sign quite often when I want to know where the cue ball will be heading. As I show in my articles (http://www.engr.colostate.edu/~dga/pool/bd_articles/index.html), the 30 degree rule applies for a wide range of shots.

http://www.engr.colostate.edu/~dga/pool/bd_articles/june05_diagram2.gif

Regards,
Dr. Dave

One
04-05-2005, 03:15 PM
I can see now why humans think my advice is weird. I thought humans were way more advanced than this!!!!!!!!!!!!

I use ALL degrees for every shot, it is stupid not to, how can you accept limited aiming? The goal of pool is perfection, you need to know ALL shots, you can't do that with memory and experience alone, YOU NEED TO LEARN PHYSICS and play with logic and understanding!!!!!

Billy_Bob
04-05-2005, 04:00 PM
This really helps me to figure out where the cue ball will go on a 30 degree rule shot. I spread my fingers out over the ball and can tell where the cue ball will go.

For the first time ever, I played an entire tournament the other night without scratching once.

This is because of you Dr. Dave! Thank you very much for your 30 and 90 degree rules (and other tips). I *really* appreciate your advice.

GreenLion
04-05-2005, 05:15 PM
Thats a neat way to find where the cueballs going to go!Sometimes i help people with there game sharing with them the knowledge that I've learned from Scott Lee,Roy(PoolHall Owner) and other people.I believe ill use this illustration in teaching position play.Thx Dr.Dave!

dr_dave
04-06-2005, 08:21 AM
<blockquote><font class="small">Quote One:</font><hr>I use ALL degrees for every shot, it is stupid not to, how can you accept limited aiming? The goal of pool is perfection, you need to know ALL shots<hr /></blockquote>
Are you talking about cut angle or the post-impact cue ball angle? Obviously, people need to be comfortable shooting shots of any cut angle. The 30 degree rule deals with where the cue ball will head after hitting the object ball (see my articles (http://www.engr.colostate.edu/~dga/pool/bd_articles/index.html) for more information). It applies fairly closely for all shots between a 1/4-ball hit and a 3/4-ball hit, corresponding to a cut angle range of 14 to 49 degrees (see TP 3.3 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/TP_3-3.pdf) for more information). This a fairly wide range of shots.

<blockquote><font class="small">Quote One:</font><hr>YOU NEED TO LEARN PHYSICS and play with logic and understanding!!!!!<hr /></blockquote>
The 30 degree rule IS based on physics, logic, and understanding. If you want to see all of the gory math and physics details, see TP 3.3 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/TP_3-3.pdf). If you just want to know how and when to use it, see my articles (http://www.engr.colostate.edu/~dga/pool/bd_articles/index.html) and the discussion threads (http://www.engr.colostate.edu/~dga/pool/threads.html) linked on my website.

Regards,
Dr. Dave

dr_dave
04-06-2005, 08:24 AM
<blockquote><font class="small">Quote Billy_Bob:</font><hr> This really helps me to figure out where the cue ball will go on a 30 degree rule shot. I spread my fingers out over the ball and can tell where the cue ball will go.

For the first time ever, I played an entire tournament the other night without scratching once.

This is because of you Dr. Dave! Thank you very much for your 30 and 90 degree rules (and other tips). I *really* appreciate your advice.<hr /></blockquote>
You are very welcome, and thanks for the nice message.

I have seen the 30 degree rule (and the use of the hand) bring many people's games to a new level.

Regards,
Dr. Dave

dr_dave
04-06-2005, 08:25 AM
<blockquote><font class="small">Quote GreenLion:</font><hr> Thats a neat way to find where the cueballs going to go!Sometimes i help people with there game sharing with them the knowledge that I've learned from Scott Lee,Roy(PoolHall Owner) and other people.I believe ill use this illustration in teaching position play.Thx Dr.Dave!<hr /></blockquote>
You're welcome. Please let us know if it has an impact with your students.

Regards,
Dr. Dave

ceebee
04-06-2005, 11:33 AM
using this carom info &amp; applying the info with knowledge of the Diamond System, you can learn to shoot 2, 3 &amp; 4 railers for position.

Imagine the possibilities that KNOWLEDGE will give you.

One
04-06-2005, 12:19 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote One:</font><hr>I use ALL degrees for every shot, it is stupid not to, how can you accept limited aiming? The goal of pool is perfection, you need to know ALL shots<hr /></blockquote>
Are you talking about cut angle or the post-impact cue ball angle?<hr /></blockquote>

I am talking about cueball control post-impact. The 30 degree "rule" is only good for beginners who doesn't know anything about physics. It is not accurate if you are pointing fingers somewhere. The difference between a 1/4-ball hit and a 3/4-ball hit is HUGE even when shooting it with the correct speed that gives the best margin, but you almost never shoot all shots with the same speed and spin! You MUST shoot it with the optimal spin and speed for optimal position play. Shoot the shot the way that is required, even if it is harder! NO RULES! The only way to become good is to play with TRUTH.

dr_dave
04-06-2005, 01:14 PM
<blockquote><font class="small">Quote ceebee:</font><hr> using this carom info &amp; applying the info with knowledge of the Diamond System, you can learn to shoot 2, 3 &amp; 4 railers for position.

Imagine the possibilities that KNOWLEDGE will give you. <hr /></blockquote>
FYI (for those who are interested), The Diamond System is described and illustrated in TP 7.2 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/index.html).

Dr. Dave

dr_dave
04-06-2005, 01:18 PM
<blockquote><font class="small">Quote One:</font><hr>The 30 degree "rule" is only good for beginners who doesn't know anything about physics. It is not accurate if you are pointing fingers somewhere. The difference between a 1/4-ball hit and a 3/4-ball hit is HUGE even when shooting it with the correct speed that gives the best margin<hr /></blockquote>
I respect your opinion, but I disagree. I'll let others chime in if they would like.

Dr. Dave

SecaucusFats
04-06-2005, 04:17 PM
Dr. Dave,

I would like to extend to you my sincere thanks for your hard work and tireless efforts in furthering the knowledge of our sport. It is obvious to me that you love the game and that your efforts are a labor of that same love. In particular, I am glad for your explanation of the 30 degree rule and the simple hand method of judging the line of travel of the cueball after it contacts the object ball. IMO, no other instructor has provided a clearer explanation of the subject. Many times, when my instincts were off, the method you teach has saved the day for me, IMO it is worth it's weight in gold AND platinum.

Again, Dr. Dave, I say thank you sir.

dr_dave
04-06-2005, 04:32 PM
<blockquote><font class="small">Quote SecaucusFats:</font><hr> Dr. Dave,

I would like to extend to you my sincere thanks for your hard work and tireless efforts in furthering the knowledge of our sport. It is obvious to me that you love the game and that your efforts are a labor of that same love. In particular, I am glad for your explanation of the 30 degree rule and the simple hand method of judging the line of travel of the cueball after it contacts the object ball. IMO, no other instructor has provided a clearer explanation of the subject. Many times, when my instincts were off, the method you teach has saved the day for me, IMO it is worth it's weight in gold AND platinum.

Again, Dr. Dave, I say thank you sir.<hr /></blockquote>
Wow! Thank you so much for this extremely flattering message. Like you, I also think the techniques and principles described in the 30 degree rule articles are very useful and easy to apply.

Regards,
Dr. Dave

One
04-06-2005, 05:58 PM
<blockquote><font class="small">Quote SecaucusFats:</font><hr> Dr. Dave,

I would like to extend to you my sincere thanks for your hard work and tireless efforts in furthering the knowledge of our sport. It is obvious to me that you love the game and that your efforts are a labor of that same love. In particular, I am glad for your explanation of the 30 degree rule and the simple hand method of judging the line of travel of the cueball after it contacts the object ball. IMO, no other instructor has provided a clearer explanation of the subject. Many times, when my instincts were off, the method you teach has saved the day for me, IMO it is worth it's weight in gold AND platinum.

Again, Dr. Dave, I say thank you sir.

<hr /></blockquote>
It is worse than I thought, unless it is some kind of a joke. I should stop posting on this forum because you won't understand anything I say.

Bob_Jewett
04-06-2005, 05:59 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote One:</font><hr>The 30 degree "rule" is only good for beginners who doesn't know anything about physics. ... <hr /></blockquote>
I respect your opinion, but I disagree. I'll let others chime in if they would like. <hr /></blockquote>
I'll chime in from a slightly different angle. While there's no reason to be impolite to "One," there's also little use in trying to have a conversation with him. Check out his other posts. He seems to operate sqrt(-1) from the rest of us.

The half-ball follow angle is in fact reasonably constant from 1/4 to 3/4 full, depending how you define "reasonably." It varies from about 28 degrees for either 1/4 or 3/4 full to 34 degrees at about a half-ball cut. Lots of people have been pointing this out in lots of books for almost 200 years, and maybe they knew something that "One" has not caught onto yet.

Of course the "1/4 the tangent" rule is more accurate to determine the follow angle over a wider range of shots, but it is slightly harder to visualize.

One
04-06-2005, 06:07 PM
<blockquote><font class="small">Quote Bob_Jewett:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote One:</font><hr>The 30 degree "rule" is only good for beginners who doesn't know anything about physics. ... <hr /></blockquote>
I respect your opinion, but I disagree. I'll let others chime in if they would like. <hr /></blockquote>
I'll chime in from a slightly different angle. While there's no reason to be impolite to "One," there's also little use in trying to have a conversation with him. Check out his other posts. He seems to operate sqrt(-1) from the rest of us.

The half-ball follow angle is in fact reasonably constant from 1/4 to 3/4 full, depending how you define "reasonably." It varies from about 28 degrees for either 1/4 or 3/4 full to 34 degrees at about a half-ball cut. Lots of people have been pointing this out in lots of books for almost 200 years, and maybe they knew something that "One" has not caught onto yet.

Of course the "1/4 the tangent" rule is more accurate to determine the follow angle over a wider range of shots, but it is slightly harder to visualize. <hr /></blockquote>

With the beginner level I mean up to pro level, but everyone seem to think the opposite that pros are "Gods".

If it is more than 2-3 degree difference it is a HUGE difference for me, getting good (optimal) position play just isn't possible like that. I can control the cueball at an accuracy of less than 1 degree, it is a MUST. Try getting the same accuracy by pointing your finger, it just doesn't work. It only works in the beginner level but not any further!

dr_dave
04-07-2005, 05:48 AM
<blockquote><font class="small">Quote Bob_Jewett:</font><hr>The half-ball follow angle is in fact reasonably constant from 1/4 to 3/4 full, depending how you define "reasonably." It varies from about 28 degrees for either 1/4 or 3/4 full to 34 degrees at about a half-ball cut.<hr /></blockquote>
For people who want to see a plot, all the numbers, and a derivation, see: TP 3.3 and TP A.4 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/index.html). My April '04 instructional article (http://www.engr.colostate.edu/~dga/pool/bd_articles/april04.pdf) also contains several illustrations that help visualize when and how the rule applies.

Billy_Bob
04-07-2005, 06:09 AM
<blockquote><font class="small">Quote One:</font><hr> The 30 degree "rule" is only good for beginners who doesn't know anything about physics. <hr /></blockquote>

Well I am a beginner who does not know anything about physics! This is something I can easily understand. BTW, I know quite a few players who can't even understand the 30 degree rule.

dr_dave
04-07-2005, 06:26 AM
<blockquote><font class="small">Quote Billy_Bob:</font><hr> <blockquote><font class="small">Quote One:</font><hr> The 30 degree "rule" is only good for beginners who doesn't know anything about physics. <hr /></blockquote>

Well I am a beginner who does not know anything about physics! This is something I can easily understand. BTW, I know quite a few players who can't even understand the 30 degree rule.<hr /></blockquote>
But the little hand in the diagram is so cute, how could they not understand it?

Billy_Bob
04-07-2005, 06:46 AM
<blockquote><font class="small">Quote dr_dave:</font><hr> But the little hand in the diagram is so cute, how could they not understand it? <hr /></blockquote>

Well because it is a diagram with lines and degrees. I think it is the "degrees" part. We're talking perhaps an 80/90 IQ here. Maybe like a 6 year old.

Perhaps a rhyming word phrase for the rule would be more understandable than a picture diagram?

dr_dave
04-07-2005, 07:45 AM
<blockquote><font class="small">Quote Billy_Bob:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> But the little hand in the diagram is so cute, how could they not understand it? <hr /></blockquote>

Well because it is a diagram with lines and degrees. I think it is the "degrees" part. We're talking perhaps an 80/90 IQ here. Maybe like a 6 year old.

Perhaps a rhyming word phrase for the rule would be more understandable than a picture diagram?<hr /></blockquote>
How about this:

Point one finger before you start.
The other finger shows the way.
Peace, man!

/ccboard/images/graemlins/smile.gif

BigRigTom
04-07-2005, 08:00 AM
Well guys, I have been a beginner pool player for some 42 years now and I had never heard of the 30 degree rule until I read Dr. Dave's book. So far I have not found any of my beginner friends on the APA league that have even heard of it much less understand it.
A few know about the 90 degree rule and seems like every one thinks he knows about deflection, english, draw and follow but...heres the real joke....
When you try to have an intelligent discussion about any of these terms you start to realize why most people never get to be really good at pool. They simply don't have good information and they don't even know it.
I can imagine the arguments that could be had with these same people about the difference in the understanding of a "pause" that I have been reading on another thread. It would be like listening to Ralph and Norton practice their pool game on "The Honey Mooners". /ccboard/images/graemlins/cool.gif

Wally_in_Cincy
04-07-2005, 08:17 AM
<blockquote><font class="small">Quote BigRigTom:</font><hr>

When you try to have an intelligent discussion about any of these terms you start to realize why most people never get to be really good at pool. They simply don't have good information and they don't even know it.
<hr /></blockquote>

I play with some guys on an APA team who shoot really well (better than me anyway) but when I try to show them something like using english to change the angle of a bank or how to throw a frozen combo they say "oh no man I can't understand that stuff"

go figure

bluey2king
04-07-2005, 08:24 AM
Hello Dr. Dave
I want to concur with Billy Bob! Your peace sign has helped during leauge play! Thank You
I also use my finger and thumb for the 90 degree rule. This helps on Safty Play when I want to seprate the cueball from the OB off the rail and down the table.
Your Buddy
Bluey2King

dr_dave
04-07-2005, 08:31 AM
<blockquote><font class="small">Quote bluey2king:</font><hr> Hello Dr. Dave
I want to concur with Billy Bob! Your peace sign has helped during leauge play! Thank You<hr /></blockquote>
You're very welcome. It feels good to know that people are using my hand technique.

<blockquote><font class="small">Quote bluey2king:</font><hr>I also use my finger and thumb for the 90 degree rule. This helps on Safty Play when I want to seprate the cueball from the OB off the rail and down the table.<hr /></blockquote>
For people who want more info on this technique, see my January '04 instructional article (http://www.engr.colostate.edu/~dga/pool/bd_articles/index.html). This was my very first article in BD.

Regards,
Dr. Dave

SPetty
04-07-2005, 09:22 AM
<blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote Billy_Bob:</font><hr> Perhaps a rhyming word phrase for the rule would be more understandable than a picture diagram?<hr /></blockquote>How about this:

Point one finger before you start.
The other finger shows the way.
Peace, man!<hr /></blockquote>Um, yeah, rhymes real good! /ccboard/images/graemlins/confused.gif

dr_dave
04-07-2005, 09:33 AM
<blockquote><font class="small">Quote SPetty:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote Billy_Bob:</font><hr> Perhaps a rhyming word phrase for the rule would be more understandable than a picture diagram?<hr /></blockquote>How about this:

Point one finger before you start.
The other finger shows the way.
Peace, man!<hr /></blockquote>Um, yeah, rhymes real good! /ccboard/images/graemlins/confused.gif <hr /></blockquote>
It takes too much time to rhyme.

There is no requirement that modern poetry rhyme anyway. ("I am an artist! I put my nose up at you.") ... just kidding /ccboard/images/graemlins/smile.gif

Dr. Dave

dr_dave
04-07-2005, 12:47 PM
<blockquote><font class="small">Quote SPetty:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote Billy_Bob:</font><hr> Perhaps a rhyming word phrase for the rule would be more understandable than a picture diagram?<hr /></blockquote>How about this:

Point one finger before you start.
The other finger shows the way.
Peace, man!<hr /></blockquote>Um, yeah, rhymes real good! /ccboard/images/graemlins/confused.gif <hr /></blockquote>
If you insist on something that rhymes, how about this:

If you let one finger stay,
The other finger points the way.
Peace.

Billy_Bob
04-08-2005, 07:13 AM
<blockquote><font class="small">Quote dr_dave:</font><hr> If you let one finger stay,
The other finger points the way.
Peace. <hr /></blockquote>

Now just need to incorporate a rolling ball instead of a stun shot.

I'm no good at this stuff, but how about...

When a rolling ball is on the way,
and you let one finger stay,
The other finger points the way.

(I think my neighbors 6 year old would understand that!)

90 degree rule and thumb anyone?

dr_dave
04-08-2005, 08:28 AM
<blockquote><font class="small">Quote Billy_Bob:</font><hr><blockquote><font class="small">Quote dr_dave:</font><hr>If you let one finger stay,
The other finger points the way.
Peace.<hr /></blockquote>
Now just need to incorporate a rolling ball instead of a stun shot.

I'm no good at this stuff, but how about...

When a rolling ball is on the way,
and you let one finger stay,
The other finger points the way.<hr /></blockquote>
I like it!
<blockquote><font class="small">Quote Billy_Bob:</font><hr>90 degree rule and thumb anyone?<hr /></blockquote>
How about ...

When the ball has stun,
this is something you should not shun:
Point your finger, and the cue ball will follow the thumb.
If you do this, nobody will think you are dumb.

Regards,
Dr. Dave

BigRigTom
04-08-2005, 09:11 AM
Now that you have rhymes you'll need to set them to music.
Hope you guys have a day job because so far I don't see this beening profitable /ccboard/images/graemlins/wink.gif
<blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote Billy_Bob:</font><hr><blockquote><font class="small">Quote dr_dave:</font><hr>If you let one finger stay,
The other finger points the way.
Peace.<hr /></blockquote>
Now just need to incorporate a rolling ball instead of a stun shot.

I'm no good at this stuff, but how about...

When a rolling ball is on the way,
and you let one finger stay,
The other finger points the way.<hr /></blockquote>
I like it!
<blockquote><font class="small">Quote Billy_Bob:</font><hr>90 degree rule and thumb anyone?<hr /></blockquote>
How about ...

When the ball has stun,
this is something you should not shun:
Point your finger, and the cue ball will follow the thumb.
If you do this, nobody will think you are dumb.

Regards,
Dr. Dave <hr /></blockquote>

BoroNut
04-09-2005, 11:16 AM
<blockquote><font class="small">Quote One:</font><hr>I am talking about cueball control post-impact. The difference between a 1/4-ball hit and a 3/4-ball hit is HUGE even when shooting it with the correct speed that gives the best margin<hr /></blockquote>

That will come as a bit of a shock to us English Billiards players who have been happilly playing full length hazards and canons on our tiny 12 foot tables under the delusion that the natural (free rolling) cue ball angles of both 1/4 ball and 3/4 ball impacts are, for all intents and purposes, identical. The only difference being where you intend to place the object ball for the next shot.

I can only assume the Aramith balls currently in use are in some way defective. I think someone should be told. It makes me sad to think that the nation largely responsible for popularising the game worldwide should be incapable of adaptation, and not also benefit from using equipment which is unfettered by the stuffy strictures of outdated ideas, such as the laws of physics and so forth.

One
04-09-2005, 01:47 PM
<blockquote><font class="small">Quote BoroNut:</font><hr> <blockquote><font class="small">Quote One:</font><hr>I am talking about cueball control post-impact. The difference between a 1/4-ball hit and a 3/4-ball hit is HUGE even when shooting it with the correct speed that gives the best margin<hr /></blockquote>

That will come as a bit of a shock to us English Billiards players who have been happilly playing full length hazards and canons on our tiny 12 foot tables under the delusion that the natural (free rolling) cue ball angles of both 1/4 ball and 3/4 ball impacts are, for all intents and purposes, identical. The only difference being where you intend to place the object ball for the next shot.

I can only assume the Aramith balls currently in use are in some way defective. I think someone should be told. It makes me sad to think that the nation largely responsible for popularising the game worldwide should be incapable of adaptation, and not also benefit from using equipment which is unfettered by the stuffy strictures of outdated ideas, such as the laws of physics and so forth. <hr /></blockquote>

If they appear identical to you, then you are using too short distance position play to see it, which is obvious because you need to shoot soft to get the biggest margin where the cueball is rolling naturally. If you don't hit a rail of course the cueball path is identical between those 2 hits, but not the degrees in between them, for a 1/2 ball hit there is about a 15 cm difference (on half table length) between 1/4 or 3/4 ball hits, which is HUGE.

And YES the path the cueball takes in a 1/4 and 3/4 ball hit is identical when the cueball is rolling naturally.


And YES I was wrong in my sentence:

"The difference between a 1/4-ball hit and a 3/4-ball hit is HUGE even when shooting it with the correct speed that gives the best margin."

It should have read (3 more letters):

"The differences in between a 1/4-ball hit and a 3/4-ball hit is HUGE even when shooting it with the correct speed that gives the best margin."

BoroNut
04-09-2005, 03:15 PM
<blockquote><font class="small">Quote One:</font><hr>If they appear identical to you, then you are using too short distance position play to see it, which is obvious because you need to shoot soft to get the biggest margin where the cueball is rolling naturally. If you don't hit a rail of course the cueball path is identical between those 2 hits, but not the degrees in between them, for a 1/2 ball hit there is about a 15 cm difference between 1/4 and 3/4 ball hits, which is HUGE.
<hr /></blockquote>

You didn't say half ball. Half ball is a completely different angle. I'm saying that 1/4 ball and 3/4 ball cue ball deflection lines are identical (within negligible tolerance) even on a full size English Billiards table with 3-5/16" pockets using standard 2-1/16" balls. It's one of the standard shots in English Billiards. If you set up a 1/4 ball angle on the object ball playing from the 'D' you can play either 1/4 or 3/4 ball natural with exactly the same result as far as the cue ball is concerned, the only difference being the path of the object ball and the relative pace on both.

Boro Nut

Edited following your edit to agree we agree.

BoroNut
04-09-2005, 06:07 PM
Dr. Dave
Iíve just followed the link to your paper TP3.3 and can say you have nicely summarised the basic principles of classic English Billiards in two graphs, though as an engineer too, maybe I just find them easy to interpret. I hope you donít mind me printing it out for instructional purposes.

Half ball and ľ ball angles are datums engraved on billiards players brains, which are used to estimate scoring shots or any corrections to be applied to your cue ball to make them. The relatively flat top of the graph shows the latitude for the beloved half ball stroke, which must account for 80% or more of my scores. A moderately proficient billiards player will play from hand (the ĎDí) in-off a ball on the centre spot into a top pocket on a standard 12 footer all day long. You can be slightly out in your cueing, thick or thin, and you will still pocket your cue ball. By contrast, playing the half ball pot ( cue ball 45mm or 1.75Ē from the centre spot in the ĎDí) is still a test of cueing, even though you have a specific point to sight at - ie no judgement of the angle is required. Itís probably even easier to play half ball in-off a ball on the pyramid (pink) spot, but potting it is quite another matter.

They also nicely indicate that slightly beyond ľ ball contact the cue ball deflection relationship to cut angle becomes increasingly linear, so for all intents and purposes the cue ball will follow the tangent line of the cut on fine ball contacts, and that margin of error drops rapidly to zero as you approach the edge of the ball.

Another thing they demonstrate is the difficulty in judging the follow angle to make the canon or in-off on a distant and slightly off centre target. The margin of error is much smaller because the contact area between full ball and ĺ ball is only 25% of the target area but accounts for the first 82% of available natural follow angles. It also varies in a non linear manner across this area. In practice itís invariably further complicated by the usual need to play either strong follow (top) when the object ball is close to the cue ball or by reduced margin of error when it is distant. When missed it is invariably on the wide side, but we do have a few tricks up our sleeve to make the shot easier.

Itís also nice to have a number to put to the ľ ball angle at last. I wonder how many of my local billiards players know what it is. Not many I bet. We all know where it is, not necessarily what it is. Perhaps next time someone is instructing a youngster that the ľ ball and ĺ ball in-off angles are the same I can impress them by saying ď Yes, within 0.3 degrees obviouslyĒ.

Boro Nut

Qtec
04-09-2005, 10:45 PM
"We all know where it is, not necessarily what it is."

So basically, you dont have to know "what" it is, to make the shot.

Q

BoroNut
04-10-2005, 04:15 AM
<blockquote><font class="small">Quote Qtec:</font><hr>So basically, you dont have to know "what" it is, to make the shot.<hr /></blockquote>

That's right. I could point the exact line on the table that the cue ball will follow without knowing how many degrees it was. You only need to be able to recognise the angle to play it. It never varies. Billiards players only ever refer to these angles as half ball, 1/4 ball, full ball, fine etc.

One
04-10-2005, 05:39 AM
<blockquote><font class="small">Quote BoroNut:</font><hr> <blockquote><font class="small">Quote Qtec:</font><hr>So basically, you dont have to know "what" it is, to make the shot.<hr /></blockquote>

That's right. I could point the exact line on the table that the cue ball will follow without knowing how many degrees it was. You only need to be able to recognise the angle to play it. It never varies. Billiards players only ever refer to these angles as half ball, 1/4 ball, full ball, fine etc. <hr /></blockquote>

I never think of any shot as half ball, 1/4 or 3/4 ball, because I almost never use exactly that angle because I play pool and not billiards. I fine tune the hit angle by less than 0.05 degrees to hit the pocket as accurately as possible and I can predict the path the cueball takes within 1 degree.

BoroNut
04-10-2005, 11:34 AM
<blockquote><font class="small">Quote One:</font><hr>I never think of any shot as half ball, 1/4 or 3/4 ball, because I almost never use exactly that angle because I play pool and not billiards.<hr /></blockquote>

Ah but that's potting. Taking on a pot involves a completely different sighting method, and you need to drop back into snooker mode to make it. Picking a point to hit on the object ball just isn't accurate enough over distance on a snooker table. On many shots your only two options are to get it exactly right, or miss. I haven't played on that many pool tables (whilst working abroad), but to put it politely, my experience was you could get away with being relatively vague with your potting.

It was fun though. Knocking balls about in any format always is, and it was good for my ego as a run-of-the-mill club player like me to be complimented on my potting ability. Quite a refreshing change to being stuffed out of sight by the prepubescent potting machines who seem to abound here nowadays. Don't get me wrong, it's not them beating me that I mind. It's them calling me mister that does it. Or asking how old they are and they hold their fingers up and say 'This many'.

Boro Nut

dr_dave
04-11-2005, 01:27 PM
<blockquote><font class="small">Quote BoroNut:</font><hr> Dr. Dave
Iíve just followed the link to your paper TP3.3 and can say you have nicely summarised the basic principles of classic English Billiards in two graphs, though as an engineer too, maybe I just find them easy to interpret. I hope you donít mind me printing it out for instructional purposes.<hr /></blockquote>
You and others are most welcome to use any of my materials for instructional purposes.

By the way, thanks for sharing your perspectives concerning the English billiards world. That was interesting to read.

<blockquote><font class="small">Quote BoroNut:</font><hr>
Itís also nice to have a number to put to the ľ ball angle at last. I wonder how many of my local billiards players know what it is. Not many I bet. We all know where it is, not necessarily what it is. Perhaps next time someone is instructing a youngster that the ľ ball and ĺ ball in-off angles are the same I can impress them by saying ď Yes, within 0.3 degrees obviouslyĒ.<hr /></blockquote>
If you like the nitty-gritty details, see the thread message (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&amp;Board=ccb&amp;Number=178482&amp;page =0&amp;view=collapsed&amp;sb=5&amp;o=&amp;fpart=&amp;vc=&amp;PHPSESSID=) summarizing some of the more interesting results concerning the 30 degree rule.

Regards,
Dr. Dave

dr_dave
06-12-2005, 08:22 PM
<blockquote><font class="small">Quote PM rec'd by Dr. Dave:</font><hr>
I just watched all your videos on your website, enjoyed them a lot! I'm confused about the 90 degree versus 30 degree thing... if you hit the ball with slight backspin, it slides into the object ball and goes on the 90 degree tangent line... sort of understand that... but you say the ball goes 30 degrees if it is rolling at impact... does this mean you have to hit a follow shot to get the 30 degrees? What if you hit the cue ball with a center hit, is it 30 degrees or 90 degrees at impact? Is the 30 degree thing just something you observed or is it a well known fact? Most of my shots I use a center hit and I usually dont get 90 or 30 degrees!!<hr /></blockquote>
I think my July '04 and June '05 Billiards Digest instructional articles answer all of your questions. There are lots of good diagrams in the articles to illustrate everything. You can view and print the articles from my website (http://www.engr.colostate.edu/~dga/pool/).

Regards,
Dr. Dave