swerve

• contributing factors
• OB "swerve" and "turn"
• reducing swerve
• squerve

for more information, see Section 4.04 in The Illustrated Principles of Pool and Billiards
and Disc II of the Video Encyclopedia of Pool Shots

contributing factors

What factors affect how much the cue ball swerves?

See my March '08 instructional article. It summarizes and illustrates all of the important factors and effects. A complete summary of all squirt, swerve, and throw effects can be found here. See also: squirt, swerve, and throw confusion.

OB "swerve" and "turn"

Can an object ball swerve or turn due to English?

Here are some videos that demonstrate the lack of significant turn:

NV B.7 - Ball "turn" caused by sidespin

NV B.8 - Straight throw of a second object ball

A slight amount of "OB swerve" is possible with masse spin transferred to the OB from follow or draw on the CB (see the end of TP A.24), but the effect is much too small to be of practical importance. With the videos above, I am just looking at the effect of pure sidespin as a ball is rolling. I call this effect "OB turn."

TP B.2 provides a physics and math-based approach to the question of whether or not a ball rolling with sidespin can turn. Here are my conclusions: A ball rolling with sidespin goes straight for all practical purposes, and cloth irregularities can create a much bigger effect, especially at slow speeds. Sometimes the ball will go straight as it slows with right spin, sometimes it will curve right as it slows with right spin, and sometimes it will curve left as it slows with right spin. Having said that, the physics does seem to suggest that there might be a small tendency for the ball to curve in the spin direction (e.g., right curve for right spin), but due to the assumptions in the analysis and the results of the video demonstrations, the value of this information is questionable.

reducing swerve

Can swerve be eleiminated with an above-center hit?

The closer the cue is to level, the less a shot with English will swerve. Unfortunately, because of the height of the rails, the diameter of the cue (above the rail), and clearance between the cue and rail, the cue will not be level on most pool shots. Also, if you hit above center with English, the squirt direction is down a little; so even with a level cue, an above-center hit still results in slight swerve action (because the effective impact direction is still down a little).

Having said all of this, an above center hit can reduce cue elevation and reduce the effects of shot speed and ball/cloth conditions (i.e., there will be less swerve).

squerve

What is squerve?

Squerve, sometimes called "effective squirt," is the combination of squirt and swerve. For more information, see my March '08 and April '08 BD articles. For a summary of all of the factors affecting squerve, see: squirt, swerve, and throw effects.