As many of you probably know, I have done lots of analysis and experiments over the years concerning squirt, swerve, and throw. Many illustrations, explanations, and examples can be found in my 2006 through 2008 BD articles available online.
Below is a quick summary of some of the useful pieces of information presented in the articles. Hopefully, some might find this list useful to validate many things you know already and/or to check if there are some effects you don't know about.
If you think I've missed any important effects, please let me know. Also let me know if you think any of the items are misleading or counter to your knowledge and/or intuition.
FYI, here's a short glossary of some of the terms used.
Squirt, Swerve, and Throw Effects:
(everything you ever wanted to know about squirt, swerve, and throw)
Regards,
Dave
Below is a quick summary of some of the useful pieces of information presented in the articles. Hopefully, some might find this list useful to validate many things you know already and/or to check if there are some effects you don't know about.
If you think I've missed any important effects, please let me know. Also let me know if you think any of the items are misleading or counter to your knowledge and/or intuition.
FYI, here's a short glossary of some of the terms used.
CB: cue ball
CIT: cut-induced throw
gearing OE: the amount of outside English that results in no throw
IE: inside English
OB: object ball
OE: outside English
SIT: spin-induced throw
squerve: combination of squirt and swerve
See my online glossary and articles for more details.CIT: cut-induced throw
gearing OE: the amount of outside English that results in no throw
IE: inside English
OB: object ball
OE: outside English
SIT: spin-induced throw
squerve: combination of squirt and swerve
Squirt, Swerve, and Throw Effects:
(everything you ever wanted to know about squirt, swerve, and throw)
- Squirt increases with the amount of English.
- Squirt does not depend on shot speed.
- Squirt increases with the amount of shaft end-mass (e.g., a low-squirt cue has less end-mass and results in less squirt).
- Squirt is less with a heavier CB.
- Squerve can be zero with certain speeds and cue elevations for a given shot distance, amount of English, and cue.
- Squirt or squerve can be canceled using back-hand English (BHE) and/or front-hand English (FHE) aim-and-pivot methods (see my November '07 article).
- Swerve increases with cue elevation.
- Swerve occurs with practically all English shots because the cue must be elevated to clear the rails.
- Swerve is delayed with faster shot speed.
- Swerve occurs only while the CB is sliding; once rolling begins, the CB heads in a straight line.
- Swerve occurs earlier with sticky cloth and later on slick cloth.
- Swerve occurs earlier with a follow shot than with a draw shot.
- Swerve angle is larger with a draw shot than with a follow shot.
- Swerve angle can be predicted and visualized using the Coriolis masse-shot aiming method presented in my November '05 article.
- For small cut angle shots (i.e., fuller hits), the amount of CIT does not vary with shot speed, but increases with cut angle.
- For larger cut angle shots (i.e., thinner hits), the amount of CIT is significantly larger for slower speed shots as compared to faster speed shots.
- The amount of CIT decreases some with larger cut angles, but not by much (especially for slower speed shots).
- Maximum CIT occurs at close to a half-ball hit (30? cut angle).
- In general, throw is larger at slower speeds, and for stun shots.
- Both follow and draw reduce throw, and they do so by the same amount (see my October '06 article).
- The largest discrepancy between throw values for stun and follow/draw shots occurs close to a half-ball hit (30? cut angle).
- The difference between the throw of stun and follow/draw shots is not as great at larger cut angles.
- More English gives you more SIT only up to a point. Additional English beyond that point actually reduces the amount of SIT (i.e., more English doesn?t always give you more throw).
- SIT is largest for a slow stun shot with about 50% of maximum English.
- The amount of throw can increase significantly as a small amount of English is added, especially for a stun shot.
- SIT is independent of speed (i.e., the throw is the same at all speeds) for small amounts of English.
- "Gearing" OE results in absolutely no throw. The amount of English required for ?gearing? increases with cut angle. At a half-ball hit, the amount of English required is about 50%.
- At very small cut angles, IE and OE create similar amounts of throw (although, in opposite directions).
- For large cut angles, a small amount of OE can result in more throw than shots with no English.
- For large cut angles, IE results in less throw than shots with no English.
- IE increases throw at small cut angles, but actually reduces the amount of throw at larger cut angles.
- OE can cause throw in either direction depending on the amount of English and the cut angle.
- Even for large cut angle shots (thin hits), excess OE (more than the ?gearing? amount) can be applied to throw the OB in the SIT direction.
- The amount of throw with IE can be much more consistent than with OE if the amount of English varies a little. In other words, the amount of throw varies more with tip placement for OE vs. IE. This might explain why some people prefer using IE on cut shots ... because they can better anticipate and adjust for the amount of throw.
Regards,
Dave
