Science Schmience: CB Follow/Draw for Banks

LSJohn

Verified Member
Joined
Aug 15, 2013
Messages
7,626
That is a good question - I expected to see it. :)

Yes, some follow is transferred to the OB for that shot. And since the first OB is momentarily trapped between the CB and the second OB (like a bank with the OB frozen to the rail), more than the usual amount of follow is transferred - but still not more than "natural rolling" follow. I don't believe that draw on the CB, even in the most advantageous cases like this, can ever transfer enough follow to the OB to equal rolling follow.

Also, it's not commonly known, but the OB is forced forward quite a bit in that shot even without draw on the CB - I'm told (by people who should know, like Bob Jewett, Ron Shepard and Dr. Dave) that it can theoretically be made without any transferred follow if it's hit at just the right angle (aimed at a point 1/10 of the way from the end rail center diamond to the corner pocket). I've never been able to make it that way, but I believe these guys, especially when they all agree.

pj
chgo
I find I usually agree with you and appreciate the way you try to analyze this stuff even when I don't (or, more often, can't decide.) I also get some guilty pleasure at your expense for some of the cracks sent your way by the weisenheimers. :lol
 

Patrick Johnson

Verified Member
Joined
Jul 31, 2008
Messages
1,440
I find I usually agree with you and appreciate the way you try to analyze this stuff even when I don't (or, more often, can't decide.) I also get some guilty pleasure at your expense for some of the cracks sent your way by the weisenheimers. :lol
I enjoy a good weisenheimer crack too, even at my expense. :D

pj
chgo
 

straightback

Verified Member
Joined
Feb 16, 2014
Messages
1,851
Back to original query about banks with draw running long. My take is this - when we bankers crank these banks, the cushion compresses quite a bit. When it does, the ball comes barreling out of there at angle that typically produces SLIDE. What this means is that the cue ball arcs a bit. The transferred high English affects this arc and can make banks run long, particularly long rail banks that have have the opportunity to slide and arc the entire nine feet.

John Brumbeck is a proponent of this observation.

I am sort of in your camp, Patrick - a lot of great bankers insist this phenomenon exists, but it seems like it may not be as pronounced as some claim. I would be surprised if we could get video evidence of it on a short rail bank. On a long rail bank, there is much more room to see the effect as the ball slips and slides against 9' of cloth.

And responsive to an earlier question you had, yes, it matters how far away the object ball is from the cushion because transferred English dissipates as it fights against the cloth. In reading Beard's book, you will notice he tells you how to make certain banks "if they are within 4" of the rail.". This is why.
 

Dudley

Verified Member
Joined
Apr 14, 2009
Messages
748
The more I learn about banking the more I believe that there is only one proper way to play each bank.

You can shoot them other ways but they don't go in as often.

I'm only talking about making them --> Not when playing moves/safe shots.


Dudley
 

lll

Verified Member
Joined
Mar 19, 2007
Messages
14,680
The more I learn about banking the more I believe that there is only one proper way to play each bank.

You can shoot them other ways but they don't go in as often.

I'm only talking about making them --> Not when playing moves/safe shots.


Dudley
care to share you revelation
 

Dudley

Verified Member
Joined
Apr 14, 2009
Messages
748
care to share you revelation
I don't really have any revelations. .

I would try to explain than showcase how little I actually know.

I'll leave explanations to the experts.

Dud
 

gulfportdoc

Verified Member
Joined
Jun 25, 2004
Messages
9,405
... P.S. To be clear: my point is not that transferred follow (or draw) never affects the bank path - it's that it only affects the bank path in certain limited circumstances, and only to a small degree even then.
Fascinating stuff, Patrick. One can't argue with practical physics. The distance from OB to rail is the key, then; and of course how much reverse spin on the CB when it contacts the OB. The question is to arrive at a rule of thumb. It would be easy for practical knowledge to measure, say, for a common 2 to 1 bank, e.g. side pocket to middle diamond to corner pocket, and different OB & CB lengths with different speeds.

I'd like to see Mike Page's excellent video replicated, only with underspin. And how long different rotations of underspin affect the OB. Perhaps he's already done this.

BTW, John B. is right. This thread should be in the bank pool section. But Steve would have to move the entire thread.

~Doc
 

mr3cushion

Suspended
Joined
Sep 17, 2008
Messages
6,062
I'm just sitting here wondering, what "Bugs" and "Taylor" would have to say about ALL this! ;)

Who were concidered the two GREATEST bankers of ALL time! :)
 

Patrick Johnson

Verified Member
Joined
Jul 31, 2008
Messages
1,440
I'm just sitting here wondering, what "Bugs" and "Taylor" would have to say about ALL this! ;)

Who were concidered the two GREATEST bankers of ALL time! :)
They'd probably say, "when I do this, that happens, and here's why". Of course they'd be right about what happens, but even money they'd be wrong about why. A good example of this is the common wisdom that hitting banks harder makes them go shorter. That's true, but the common explanation that they bank shorter because of more rail compression is wrong. In fact, absent other effects, more rail compression makes the OB bank a little longer, as shown by Bob Jewett:

Video: Bank Speed Effects, with Bob Jewett

The more likely explanation is that at slower speeds the OB gets rolling before hitting the rail, which makes it curve longer than equal-angle after rebounding. And at faster speeds the OB slides into the rail (with less or no forward rotation), which makes it bank closer to equal-angle.

So the real explanation is not that banking harder shortens banks, but that banking softer lengthens them. That might sound like nitpicking, but knowing what's really happening can matter - for instance, it tells you that you probably won't shorten a bank by hitting it harder if the OB is too close to the rail to get rolling anyway.

pj
chgo
 

mr3cushion

Suspended
Joined
Sep 17, 2008
Messages
6,062
They'd probably say, "when I do this, that happens, and here's why". Of course they'd be right about what happens, but even money they'd be wrong about why. A good example of this is the common wisdom that hitting banks harder makes them go shorter. That's true, but the common explanation that they bank shorter because of more rail compression is wrong. In fact, absent other effects, more rail compression makes the OB bank a little longer, as shown by Bob Jewett:

Video: Bank Speed Effects, with Bob Jewett

The more likely explanation is that at slower speeds the OB gets rolling before hitting the rail, which makes it curve longer than equal-angle after rebounding. And at faster speeds the OB slides into the rail (with less or no forward rotation), which makes it bank closer to equal-angle.

So the real explanation is not that banking harder shortens banks, but that banking softer lengthens them. That might sound like nitpicking, but knowing what's really happening can matter - for instance, it tells you that you probably won't shorten a bank by hitting it harder if the OB is too close to the rail to get rolling anyway.

pj
chgo
I only have one question. Why is Bob demonstrating this by playing a, "combination" bank, instead of the CB to OB directly?
 

Patrick Johnson

Verified Member
Joined
Jul 31, 2008
Messages
1,440
I only have one question. Why is Bob demonstrating this by playing a, "combination" bank, instead of the CB to OB directly?
To avoid small aiming and sidespin errors, which would make the results impossible to interpret accurately. Anticipating and controlling variables like that is one of the reasons we can trust the results of tests done by "scientists" like Jewett, Page, etc. over the "personal experience" of (even very good) players.

pj
chgo

P.S. To be clear about this aside: CB/OB spin transfer (the topic of this thread) is not what Bob was testing - he was testing the effect of speed alone, so he wanted to avoid any CB spin transfer.
 
Last edited:

mr3cushion

Suspended
Joined
Sep 17, 2008
Messages
6,062
To avoid small aiming and sidespin errors, which would make the results impossible to interpret accurately. Anticipating and controlling variables like that is one of the reasons we can trust the results of tests done by "scientists" like Jewett, Page, etc. over the "personal experience" of (even very good) players.

pj
chgo
I have MANY more Q's, but this would turn into another debacle! :rolleyes:

I'll leave it alone! ;)
 

John Brumback

Verified Member
Joined
Dec 6, 2010
Messages
1,747
They'd probably say, "when I do this, that happens, and here's why". Of course they'd be right about what happens, but even money they'd be wrong about why. A good example of this is the common wisdom that hitting banks harder makes them go shorter. That's true, but the common explanation that they bank shorter because of more rail compression is wrong. In fact, absent other effects, more rail compression makes the OB bank a little longer, as shown by Bob Jewett:

Video: Bank Speed Effects, with Bob Jewett

The more likely explanation is that at slower speeds the OB gets rolling before hitting the rail, which makes it curve longer than equal-angle after rebounding. And at faster speeds the OB slides into the rail (with less or no forward rotation), which makes it bank closer to equal-angle.

So the real explanation is not that banking harder shortens banks, but that banking softer lengthens them. That might sound like nitpicking, but knowing what's really happening can matter - for instance, it tells you that you probably won't shorten a bank by hitting it harder if the OB is too close to the rail to get rolling anyway.

pj
chgo
I agree with all of this also. I try to be very careful about what I tell people about pool and banking. You would never hear me say that you have to shoot hard to shorten or hold a bank shot. That's just another old myth:lol On top of that...if you shoot too hard ( with low) the oball will bounce and go even longer:eek: I try not to get into the science part of a pool shot but I do feel that I know what works good and what doesn't. I can show better than I can tell is what I'm saying:p John B.
 

gulfportdoc

Verified Member
Joined
Jun 25, 2004
Messages
9,405
... A good example of this is the common wisdom that hitting banks harder makes them go shorter. That's true, but the common explanation that they bank shorter because of more rail compression is wrong. In fact, absent other effects, more rail compression makes the OB bank a little longer, as shown by Bob Jewett:
Video: Bank Speed Effects, with Bob Jewett ...
pj
chgo
My guess is that the "shortness" varies depending upon the angle coming into the rail. Obviously a wide angle bank is not going to come "short", whereas a medium angle bank would appear to. It would be interesting to know at what angle there is no effect.

And, conversely, at what angle the "long" effect dissipates.

~Doc
 

Patrick Johnson

Verified Member
Joined
Jul 31, 2008
Messages
1,440
My guess is that the "shortness" varies depending upon the angle coming into the rail. Obviously a wide angle bank is not going to come "short", whereas a medium angle bank would appear to. It would be interesting to know at what angle there is no effect.

And, conversely, at what angle the "long" effect dissipates.

~Doc
I "measure" my banks and kicks using the diamonds. The equal-angle rail contact point is always at the "gutter" in front of the rail, but most banks/kicks (at moderate speed with no spin) must be aimed shorter than that because they tend to go long (because of forward rotation and because the rail doesn't "give back" all the speed it absorbs).

Aiming at the diamonds on the rail rather than at the equal-angle spot at the gutter does a fair job of adjusting for this, even automatically "adjusting the adjustment" - shortening the angle more for wider angles and less for steeper ones. I find that when the angle gets very wide or very steep I need to add some manual adjustment too - aiming behind the diamond on the rail for wider angles and in front of it (but still on the rail) for steeper ones.

I think no adjustment (aiming right at the equal-angle gutter spot) isn't possible except for very steep angles, probably less than 10 degrees (like kicking cross corner from 1 diamond up the long rail).

pj
chgo

P.S. Here's a checklist of some things that affect rebound angles. Some of these work against each other, sometimes cancelling both effects.

- rail "rebound efficiency" (coefficient of restitution) is less than 100%, causing balls to rebound long - most effect at 45 degrees(?)
- rail friction (between cloth and ball) causes balls to rebound short - most effect at 45 degrees(?); effect increased by sticky cloth balls
- "rolling follow" masse causes balls to curve long after rebounding - most effect at 45 degrees; effect increased by sticky cloth balls
- shot speed causes balls to rebound longer at lower speeds and shorter at higher speeds, because of the presence or absence of rolling follow
- draw masse causes balls to curve short after rebounding - most effect at 45 degrees; effect increased by sticky cloth balls
- rail-induced masse causes balls to curve short after rebounding - most effect at 45 degrees(?); effect increased by sticky cloth balls
- left/right sidespin causes balls to rebound longer (if "running" spin) or shorter (if "braking" spin) - most effect at steep angles; effect increased by sticky cloth balls
 
Last edited:

gulfportdoc

Verified Member
Joined
Jun 25, 2004
Messages
9,405
I "measure" my banks and kicks using the diamonds. The equal-angle rail contact point is always at the "gutter" in front of the rail, but most banks/kicks (at moderate speed with no spin) must be aimed shorter than that because they tend to go long (because of forward rotation and because the rail doesn't "give back" all the speed it absorbs).

Aiming at the diamonds on the rail rather than at the equal-angle spot at the gutter does a fair job of adjusting for this, even automatically "adjusting the adjustment" - shortening the angle more for wider angles and less for steeper ones. I find that when the angle gets very wide or very steep I need to add some manual adjustment too - aiming behind the diamond on the rail for wider angles and in front of it (but still on the rail) for steeper ones.

I think no adjustment (aiming right at the equal-angle gutter spot) isn't possible except for very steep angles, probably less than 10 degrees (like kicking cross corner from 1 diamond up the long rail). ...
I too have always used the diamonds as aiming points, probably because I played 3C years ago. I've noticed that purely aiming at the diamonds doesn't allow for equal angle systems for banks-- not lending itself to such a neat system as does the "diamond system" in 3C. But that's another subject. Although, maybe not, due to the rebound angle from wider/shorter approaches.

When you aim at the gutter in front of the rail, are you referring to where the rail meets the table bed? I noticed that Fred in his banking book uses the point on the rail exactly opposite the diamond (at least for many shots), which is a half inch or so ahead of the juncture, depending upon the angle of approach. Actually if you played on a Diamond table rather than a GC, you might find that your aim point is right on, rather than having to move back a little, since Diamond tables tend to rebound shorter than do GC's. At least the red label tables did.

~Doc
 
Top