Re: Questions for science guys

On Dec 19, 1:00 pm, "bk42...@xxxxxxxxxxx" <bk42...@xxxxxxxxxxx> wrote:

Given the angle between CB path towards the OB and the OB's path to
the pocket, is it possible to calculate a return angle from the OB
based on some definition of "amount of outside and draw"? Or do table
conditions (cloth type and condition, ball cleanliness or dirtiness,
quality of tip, quality of stroke(?), etc.) have too large of an
effect on the shot?

There is a relatively simple method of determining the cueball's
direction once it reaches natural roll after the collision with the
object ball. It applies when using any amount of straight draw or
follow and can be constructed from the offset of the ball/ball contact
point, the tangent line direction, and the vertical tip offset. A
problem with it though is estimating how much spin the cueball will
retain after the collision. It loses (or gains) at least a little bit
of spin during each stage of the shot, so the effective vertical tip
offset is not exactly the same as where the cueball is actually
struck. And it doesn't give you the details of the path as it
traverses a parabolic curve, just the final roll direction.

That said, it predicts that if you strike the cueball at the miscue
limit of (1/2)R below center, the cueball's roll direction will be
twice the cut angle from straight back. Cloth condition is not a
factor. Because of vertical squirt and some spin loss on the way to
the OB, as well as during the collision, you would actually have to
hit a little below (1/2)R, but let's ignore this. Your original shot
diagram is a particularly good example of how to use this to get an
estimate, since the OB is going to travel at about a 45-degree angle
to the cushions. Extend the aim line to the short cushion. It looks
like it will intersect it at about 1.8 diamonds from the pocket. Now
draw a line starting at 1.8 diamonds on the other side of the pocket
(on the long cushion), and through the center of the ghostball. This
doubles the cut angle and will be the cueball's final roll direction.
Or, more accurately, it's the limit of what you can hope to achieve
with maximum draw. In reality, because of the spin losses mentioned,
its roll direction will be a little more than twice the cut angle from
straight back, i.e., not as sharp.

I don't think using outside english gets you much, for the reasons Ron
has thoroughly explained. And with a nearly level cue, I also don't
thing there's much to be gained with inside. However, if you're
actually getting the cueball to draw along the direction indicated in
the diagram, you're doing something right! I'll re-read your post
(s), but if you would like to include any more details....

Jim
.

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