Swerve or Throw?

[Colin Colenso]

Colin,
Sorry but I hate to ask but I just have to..... How does the Pivot Length affect swerve? Shorter pivot length vs. longer pivot length. Which one reduces and why?

Some brand new 760 Simonis cloth helps out on the swerve too. :smile:
Thanks,
JoeyA

Joey,

Most people know that pivoting can basically cancel out squirt, but we have a term called Effective Squirt, which is the result of the combination of squirt and swerve (Squerve).

When shots are played firm over short distances (hence no swerve) my Pure Pivot Point is about 10 inches, as the length of CB travel increases and the speed of shot decreases the Effective Pivot Point can move out to as far as 20 inches. For most shots, such as 3 feet medium speed it is around 14 inches.

By knowing where to set my pivot point for various speeds and distances, I can still hit close to my aim contact point for any shot with English.

However, I have to adjust my intended aim contact point depending on the throw that will affect each shot. On some shots with English, this aim adjustment is crucial.

Attached is a plot of changes in throw angle for various spins on a soft speed 3/4 ball shot. Cutting to the left, hence Outside English is on the right. Each color band represents 1 inch per yard of throw deviation from the expected line. The difference between heavy OE and medium IE is about 9 inches per yard, or 3 inches per foot travelled.

It's little wonder that players who don't know how much to compensate for these shots avoid them.

Colin

 

[Patrick Johnson]

Originally Posted by JoeyA
I thought you got less swerve when hitting low because the cue ball was skidding more and less natural roll. (something to do with friction maybe)?
JoeyA

Swerve is basically a masse effect. It's impossible to actually shoot with a flat cue, however the cue can be flatter when hitting above center compared to hitting below center.

If you can imagine where your tip is pointing to the cloth, when striking the CB, the CB will swerve toward that point. The flatter the cue, the further away that point is, which means less angle of swerve.

The skid won't have any significant effect in reducing the swerve. A rolling CB with some component of English skids in a sense also, the english aspect slides.

If I understand Joey, he's saying that hitting below center lifts the CB some, reducing immediate ball/cloth friction and causing the CB's curve to stretch out (as if the cloth is slicker) compared with hitting above center. I think this is a plausible idea.

I also think that the opposite effect occurs: hitting above center forces the CB down into the cloth during tip contact, increasing immediate ball/cloth friction and causing the CB's curve to shorten (as if the cloth is stickier) compared with hitting below center. This is very noticable when hitting even more downward, such as when the CB is frozen to the rail.

I think these differences together can account for a noticable increase in swerve effect when hitting above center compared with hitting below center.

But there may be an argumant from a static friction standoint that rolling english is likely to take grip earlier than backward spinning english.

We get the same effect with spin induced throw on extreme cut shots where a touch of outside english causes more throw (more friction) than either, sliding ball, Inside english or Heavy Outside english. The similar direction of movements of the surfaces allows greater grip.

So this could provide a mechanism for rolling english to curve earlier than draw english.

I can't visualize exactly what you're saying here.

pj
chgo

 

[Colin Colenso]

I can't visualize exactly what you're saying here.

pj
chgo

It's based on the idea that friction is zero when the surfaces are not moving relative to each other, then they increase as the relative speeds increase up to a point where the friction begins to decline as the relative speeds of the surfaces increases further.

This is apparent in the chart I attached above, where friction (resulting in throw) decreases as the amount of IE moves past 50% and also where topspin or backspin exist in addition to english (toward the top and bottom of the throw chart).

Colin

 

[okinawa77]

When you shoot a shot with english, what do you feel has the greater effect? Swerve or Throw?

EDIT: ...for a shot that is about 3' between the OB and CB.

IMO:
For short shots, like you stated in your EDIT, throw.
For long shots, like full table, swerve.

 

[perspicaz]

I would say you get more swerve with low english than high because the cueball tends to "grab" more on the cloth when transitioning from backwards to forward rotation. On high hits there is little swerve because the cueball does no transition and is rolling forward from the beginning. Actually, I use this concept to time the moment the cueball will swerve towards the side in those "I can almost see the ball" shots.

If you want the minimum effect from swerve hit high, to avoid spin throw hit harder (balls "cling" more with slow shots). Collision induced throw is a different animal. IMHO.

 

[dr_dave]

not enough options

There is no good answer to this question. Squirt, swerve, and throw can all be important in different situations. FYI, a good summary of all of the relevant effects can be found here:

http://billiards.colostate.edu/threads/aiming.html#compensation​

Regards,
Dave

 

[RBC]

Actually, the shots I am talking about are relatively soft shots where the cue ball will end up rolling with sidespin. The transition from back spin with sidespin to a rolling ball with sidespin will cause severe swerve. When hit with topspin and sidespin, there is no transition. The cue ball leaves the tip with natural roll and sidespin. Basically it is spinning on an axis that is tilted to one side or the other. When hitting inside english, too much swerve makes you hit the ball to full. Most players who are missing it full are shooting the cue ball with low. When I ask them to hit the same shot with high, they don't get the transition swerve and they either make the shot, or come closer. Hitting high does not eliminate swerve, but at least from my observations, it does drastically reduce it.

As far as the level cue goes, the cue is more level hitting high than hitting low. Also, when you hit the cue ball low you hit it down into the cloth even harder than when you hit it with high. The concept that the cue ball is lifted when hit low is a misconception. Basically, you are talking about squirting the cue ball up instead of to the side. Even with very high squirt shafts, the squirt angle is still much less than the angle of your cue when hitting down into the cue ball. Therfore the cue ball must be driven down into the cloth. That is the only place it can go.

Just my thoughts anyway!

Royce Bunnell
www.obcues.com

 

[mullyman]

To be totally honest I don't really think about those things. I can't understand how anyone shoots pool if their mind is cluttered up with all that stuff. I remember the day I was taught to use english on a shot. I was shooting and made a pretty good shot but didn't get position on the next ball. One of the room owners came over to me and said "If you use low right on that shot you'll get that position." so he set it up again, I used low right and missed the ball. I even saw the swerve. I said to him "How the hell am I supposed to make that?" and he replied "Keep shooting it until you get it." and that's all there was to it. There wasn't any "This cue deflects by 1/2 an inch and the throw on the ball will be yada yada yada". Nope, it was a simple, "Shoot it until you can make it."

I'm pretty sure you get to a point in your game where your muscle memory takes over and makes those adjustments for you.
MULLY

 

[Patrick Johnson]

I can't understand how anyone shoots pool if their mind is cluttered up with all that stuff.

Some people can learn things without cluttering up their minds.

I'm pretty sure you get to a point in your game where your muscle memory takes over and makes those adjustments for you.

I don't think there will ever be a point in my game where learning doesn't improve my muscle memory.

pj
chgo

 

[av84fun]

Swerve is basically a masse effect. It's impossible to actually shoot with a flat cue, however the cue can be flatter when hitting above center compared to hitting below center.
If you can imagine where your tip is pointing to the cloth, when striking the CB, the CB will swerve toward that point. The flatter the cue, the further away that point is, which means less angle of swerve.

The skid won't have any significant effect in reducing the swerve. A rolling CB with some component of English skids in a sense also, the english aspect slides.

But there may be an argumant from a static friction standoint that rolling english is likely to take grip earlier than backward spinning english.

We get the same effect with spin induced throw on extreme cut shots where a touch of outside english causes more throw (more friction) than either, sliding ball, Inside english or Heavy Outside english. The similar direction of movements of the surfaces allows greater grip.

So this could provide a mechanism for rolling english to curve earlier than draw english.

Colin

A slight edit is necessary. Actually it is possible to shoot level...even UPWARD if the CB is past the centerline...especially on diagonal shots where the butt can actually go into the pocket opening. You can actually drag your grip hand knuckles on the cloth and use maximum top so the cue is clearly angled upward.

I know you meant on most shots. The above is just for the sake of complete accuracy.

Regards,

Jim

 

[Colin Colenso]

A slight edit is necessary. Actually it is possible to shoot level...even UPWARD if the CB is past the centerline...especially on diagonal shots where the butt can actually go into the pocket opening. You can actually drag your grip hand knuckles on the cloth and use maximum top so the cue is clearly angled upward.

I know you meant on most shots. The above is just for the sake of complete accuracy.

Regards,

Jim

True Jim

But I don't think I've ever used that shot in all my years. Impossible should not be the adjective employed here. Perhaps 'almost without exception'.
Colin

 

[Jimmy M.]

I chose swerve because I like to get my swerve on. :thumbup:

 

[Jal]

If I understand Joey, he's saying that hitting below center lifts the CB some, reducing immediate ball/cloth friction and causing the CB's curve to stretch out (as if the cloth is slicker) compared with hitting above center. I think this is a plausible idea.

I also think that the opposite effect occurs: hitting above center forces the CB down into the cloth during tip contact, increasing immediate ball/cloth friction and causing the CB's curve to shorten (as if the cloth is stickier) compared with hitting below center. This is very noticable when hitting even more downward, such as when the CB is frozen to the rail.

I think these differences together can account for a noticable increase in swerve effect when hitting above center compared with hitting below center.

Patrick, I think most of the effect is due to the amount of relative surface speed available, in a manner of speaking, and the direction of that surface speed.

With a sphere sliding on a fixed surface (cloth/bed), 2/7'ths of the initial relative surface velocity, which has both magnitude and direction (ie, it's a vector quantity) is subtracted vectorally from the sphere's initial translational velocity, which also has magnitude and direction, during the process of reaching natural roll.

In the case of a high hit with english, there is relatively little surface speed in magnitude, but its direction is more sideways. Thus, you get a more immediate swerve effect because of the direction, but the final swerve angle is less because of the smaller magnitude.

In the case of a low hit with english, the magnitude of the relative surface speed is larger, but its direction is less sideways and more in line with the sphere's initial direction. Here you end up with a greater overall swerve angle if the ball is allowed to reach natural roll before colliding, but the effect is not as immediate because of the direction of the surface speed. So with many draw shots you don't see that much swerve because natural roll isn't achieved before the collision, and the swerve takes place at a more leisurely pace.

The bouncing you described no doubt adds to this, but I think the major difference is due to the surface speed stuff described above. A ball that is just slightly bouncing acts pretty much like a ball that is sliding uniformly on the cloth. (But I can't say that I've done a quantitative comparison for specific cases.)

In the case of a ball/ball collision (ie, no fixed surface), and where the balls reach "natural roll" across each other during the collision, 1/7'th, as opposed to 2/7'ths, of this initial relative surface velocity adds vectorally to the object ball's velocity (initially zero of course), and is likewise subtracted from the cueball's post-impact velocity. The horizontal component of this is the OB's throw velocity. It's reduced to 1/2 here because the object ball can both move and spin and is physically identical to the cueball (ideally), and thus kindly (or maybe unkindly) takes up half of that 2/7'ths.

(Hope this adds to any confusion - it sure has helped mine. Dr. Dave illustrates these swerve effects in at least one of his articles.)

Jim