Why is it that with some follow shots, the cue ball stays close to the rail?
NV 4.8 – Rail dribble follow shot, NV 4.9 – Normal follow shot into a rail, and HSV B.21 – follow-the-rail trick shot illustrate and explain the effects fairly well. The following video contains a good demonstration also:
With almost all follow shots (regardless of speed), the CB is “rolling” at object ball impact. This is certainly the case in the “rail dribble” videos. With more speed, there is correspondingly more topspin, but the CB is still rolling (provided you are hitting the CB high enough).
The amount of follow action depends on how little CB speed remains in relation to the amount of topspin retained. With a fast follow shot, the CB has lots of topspin (as the ball rolls at a higher speed). With a smaller cut angle, most of the CB’s speed is lost, but almost all of the topspin is retained after OB impact. That’s what produces the follow “action” … lot’s of spin, not much speed. That’s why both speed and cut angle are important in this type of shot.
If the cue ball has lots of topspin and very little speed when it hits a rail, “rail dribble” occurs (see HSV 4.3 – Rail dribble follow shot).