Mark Wilson on sidespin to pocket balls

[Paul_#_]

An object ball has side spin from the cue ball if and only if there has been throw. The two always go together. If you throw the object ball you also "twist" it.

Figure 6-15 would contradict that or, at least, show minimal throw from inside english at cuts greater than about 32 degrees.

It finds no more or less throw on object ball from cue ball hit with inside english compared to no english at cuts greater than about 32 degrees. The only throw at >32 degrees is that from cut-induced throw (labeled No english in figure). At 32 degrees, outside spin throws the object ball in the opposite direction from that of no-english cut-induced throw.

Figure 6-16 shows that for a 55 degree cut, there is no additional throw from inside english compared to the same shot no-english. There is no difference in pocketing ball with inside english than no english. Using outside instead of inside english, however, causes a three degree error (0.8 inches) on a shot 15 inches from the pocket.

From The Science of Pocket Billiards, Jack H. Koehler, 1989.

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[Patrick Johnson]

An object ball has side spin from the cue ball if and only if there has been throw. The two always go together. If you throw the object ball you also "twist" it.

Figure 6-15 would contradict that or, at least, show minimal throw from inside english at cuts greater than about 32 degrees.

And also minimum “twist” (transferred spin), supporting Bob’s statement: no throw = no “twist”. They’re both produced by the same force.

pj
chgo

 

[Bob Jewett]

Figure 6-15 would contradict that or, at least, show minimal throw from inside english at cuts greater than about 32 degrees. .

Jack doesn't show how much sidespin the object ball has, so the figure is unrelated to what I wrote.

As Pat said, the two results are caused by the same force, so they have to be together.

 

[3kushn]

Jack doesn't show how much sidespin the object ball has, so the figure is unrelated to what I wrote.

As Pat said, the two results are caused by the same force, so they have to be together.

Has anybody studied cut induced influences on the CB?

I know there is such a thing, but nobody talks about it here or anywhere.

How do you calculate CB paths without knowing what spin is added or subtracted, given the hit.

 

[straightline]

Has anybody studied cut induced influences on the CB?

I know there is such a thing, but nobody talks about it here or anywhere.

How do you calculate CB paths without knowing what spin is added or subtracted, given the hit.

I imagine the mathmeticulans can quantify that stuff but inside those numbers it still's gotta be feel. Build or fly the helicopter.

 

[Bob Jewett]

Has anybody studied cut induced influences on the CB?...

The sideways rub on the cue ball slows it or speeds it up just a little but doesn't change it's direction. That means that the angle between the path of the object ball and the cueball will be slightly different from 90 degrees in the first instant after ball-ball contact.

The effect is usually negligible with all the other imperfections in the typical shot. It does mean that if you hit an OB perfectly full with side, the cue ball will move slightly to the side, but this could easily be mistaken for an aiming error.

 

[SSP]

My understanding of cut induced throw happens when shooting a long cut shot that you have to shot slow for position, the friction of the cloth causes the angle of the object ball to change(lessen) and needs to be accounted for when aiming, that is my understanding.....

 

[Bob Jewett]

My understanding of cut induced throw happens when shooting a long cut shot that you have to shot slow for position, the friction of the cloth causes the angle of the object ball to change(lessen) and needs to be accounted for when aiming, that is my understanding.....

No, that's not it at all.

Let's say you simply cut an object ball without any side spin on the cue ball. When the cue ball contacts the object ball, it's surface it moving somewhat sideways on the object ball. There is friction at the contact point, and the object ball is dragged a little off line by that friction. If you cut a ball to the left, the cue ball will move to the right off the object ball, and the object ball will be dragged a little in that direction.

There are lots of details but that is the gist of cut induced throw. It has nothing to do with the cloth and is only somewhat affected by speed.