As fPieces Of Eight -
Tip Of The Week
Number:
90 Jim Tellier July 2013 Summer
2013 Session
TOPIC: The
Rolling Cue Ball
CATEGORY: Intermediate/Advanced
INTRODUCTION:
Do
you know how far the cue ball will roll, after you hit the object ball?
TECHNIQUE:
This
isnt something that can be fully explained in a paragraph or two, so we need
to rely on some expertise (in this case Dr. Dave, once again!) to come to the
rescue!
Fact #1:
If a rolling cue ball
hits an object ball squarely, the object ball will ideally travel a little
more than 6 times farther than the cue ball after impact.
Fact #2:
When a ball is hit off-center, less energy is imparted to
that (object) ball, therefore it will not travel as far.
Some approximate travel distances for common hits are shown
below:
Fullness OB:CB
Distance Ratio
----------------- -------------------------------------
Full-Ball Hit 6.5 : 1
-Ball Hit 3.5 : 1
-Ball Hit (30) 1.25 : 1
33.5 Hit 1 : 1
-Ball Hit 1 : 2
3/16-Ball Hit 1 : 4
1/8-Ball Hit 6.5 : 1
So whats all this mean? Start with the Full Ball hit.
The chart says that, the Object Ball (OB) will roll 6.5 times farther than the
Cue Ball (CB) after the CB contacts the OB.
This is true IF the cue ball is rolling
when it contacts the OB. So recall previous articles where we described that
the CB will immediately start rolling if it is hit approximately tip
above center ball, at a medium speed. (Thats one case; there are
others, of course). But its a common scenario, where you want to roll the
cue ball forward a specific distance, to get shape on the next ball, etc.
So, lets take an example. Put a ball exactly in the
center of the table (a 7 bar table). Put the cue ball just inside the corner
pocket, setting up a full diagonal table length shot. The OB will need to
travel approximately 4 ft. to get to the pocket, after being hit Full by the
cue ball. If you hit the OB just barely hard enough to pocket the ball,
the OB will travel about 6.5 times farther than the cue ball will travel after
contact. So, about 4 ft / 6.5 = about 7-1/2 inches. (Im not using exact
table measurements here, but the idea is that the cue ball travel will be
almost 1/7th the travel of the OB, on the Full Ball Hit.
Now, look at the chart. Everything that is less than a
full-ball hit will impart less energy to the OB, meaning that there is more
energy left for the cue ball to travel. At the extreme, the CB will travel
6-1/2 times farther than the OB, if it is hit really thin (1/8-ball). If you
barely skim the OB with the CB, it might only roll of a turn, while the cue
ball will retain nearly all of its initial speed.
Its a very useful exercise to place a ball somewhere on the
table, and experiment with how far the cue ball will roll after hitting the
OB. Getting a good feel for this is very important.
Once you have a good basic sense of what to expect, you will
then be able to adjust to the variations in how individual tables (and balls)
affect the speeds of the balls.
And remember, this is all just talking about the two balls,
the cloth, and the speed/distance of the hit.
The physics
& math of all this can be found in the Technical Proof article at
http://billiards.colostate.edu/technical_proofs/new/TP_A-16.pdf
but, the
pool-player doesnt need to understand that at all! Only the results,
as shown
above!
A
couple of very useful links to instructional materials are:
http://www.azbilliards.com/2000instruction.php
http://www.billiards.colostate.edu
Shoot well, and keep your opponent in
his chair!
Capn
Carom
ARRRR!!!! J