Quick quiz by Sharivari

ChrisinNC said:
That’s pretty much what I’m claiming when referring to break shots where the margin is very thin as to whether you’ll hit that bottom ball (with the cue ball) on the break shot, or miss it.

I did try some shots doing this yesterday, and there seemed to be an extremely slight variance in the direction that cue ball initially takes off the object ball, on about a 30° angle cut break shot, using firm stroke draw vs firm stroke follo
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I would perform that experiment using just two balls. I would put stickies on the table for both the break ball and the corner ball in the rack. Then I would make sure that the tangent line for the break ball misses the corner ball. With the break ball on the left side of the rack, the tangent line into the right side of the corner pocket would have to miss the corner ball. The tangent line into the right side of the pocket is the tangent line that will come closest to the corner ball in the rack. I would confirm that the tangent line into the right side of the corner pocket missed the corner ball by placing the CB just a few inches from the break ball, then I would aim at the right side of the corner pocket, and I would hit center ball on the CB so that the CB is sliding when it hits the break ball, and I would make sure that the CB just misses the corner ball. If the break ball went into the middle of the pocket, the shot wouldn't count as missing the corner ball. Only when the break ball went into the right side of the corner pocket and the CB missed the corner ball would I know that the shot was setup correctly.

Once I got that all setup, I would then hit follow on the CB and after the CB struck the the break ball I would observe whether the CB ever hit the corner ball.
 
7stud said:
I would perform that experiment using just two balls. I would put stickies on the table for both the break ball and the corner ball in the rack. Then I would make sure that the tangent line for the break ball misses the corner ball. With the break ball on the left side of the rack, the tangent line into the right side of the corner pocket would have to miss the corner ball. The tangent line into the right side of the pocket is the tangent line that will come closest to the corner ball in the rack. I would confirm that the tangent line into the right side of the corner pocket missed the corner ball by placing the CB just a few inches from the break ball, then I would aim at the right side of the corner pocket, and I would hit center ball on the CB so that the CB is sliding when it hits the break ball, and I would make sure that the CB just misses the corner ball. If the break ball went into the middle of the pocket, the shot wouldn't count as missing the corner ball. Only when the break ball went into the right side of the corner pocket and the CB missed the corner ball would I know that the shot was setup correctly.

Once I got that all setup, I would then hit follow on the CB and after the CB struck the the break ball I would observe whether the CB ever hit the corner ball.
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Your experiment is too complicated for me to undertake. Besides, I’m not precise enough to know for sure what side of the pocket the ball enters. I stay focused with my head still throughout the follow through, so looking to see what side of the pocket the ball is entering is a bad habit for me.
 
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ChrisinNC said:
Your experiment is too complicated for me to undertake. Besides, I’m not precise enough to know for sure what side of the pocket the ball enters. I stay focused with my head still throughout the follow through , so looking to see what side of the pocket the ball is entering is a bad habit for me.
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I think a possible problem with your experiment is: sinking the break ball into different parts of the pocket will cause the CB to hit the corner ball or miss based on that alone. You would need a helper to assist you when setting up the balls so that the tangent line into the right side of the corner pocket misses the corner ball. You would aim at the right side of the corner pocket with a stun shot, and your helper would tell you if the ball went into the right side of the pocket. If the break ball went into the right side of the pocket, and the CB just missed the corner ball, then you would have the stickies in the right place to perform your experiment.
 
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Bob Jewett said:
The straight portions of the paths are parallel. This is explained well by both Byrne and Alciatore. It is essential knowledge at English Billiards.
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The Alciatore graphs I posted don't show that. Do you have a link for an article?

So the paths should look more like this?

curves_changes2.jpg
 
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7stud said:
The Alciatore graph I posted doesn't show that. Link?

So the paths should look like this?
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The first diagram you showed above with the table in it is correct. As long as the quality of the draw or follow is kept constant, speed does not affect the final direction. Speed just makes the curved portion wider.

By "quality" I mean the spin/speed ratio. A ball that is rolling smoothly on the cloth I call 100% or unity quality follow. You can get the same quality of draw, but only with a near-the-limit low hit on the cue ball. Of course the quality of the draw decreases on the way to the object ball as the cloth rubs the draw off.

It was shown a long time ago (by Coriolis, no less) that for a given fullness of hit and quality of draw or follow, the final direction of the cue ball does not depend on the speed. What does change is how far over the cue ball slides during its curved path. It is easy to get the actual direction wrong if you think that direction is a straight line from the ghost ball to where the cue ball finally hits something else. Direction is the direction of the straight part of the cue ball's path after it has finished curving.

Another place a lot of people go wrong in this kind of situation is that as they crank up the speed for follow shots they fail to keep the quality of the follow constant. If you hit at 50% follow and softly, the cue ball will arrive with 100% follow if there enough time for the cue ball to start rolling smoothly before it gets to the object ball. If you hit at 50% follow and medium-hard, it may be that the cue ball arrives with only 60% follow having had only time enough to get 10% towards smooth rolling. The shooter might think that the angle changed but what really changed was the percentage of full follow at contact.
 
dr_dave said:
Illustrations and demonstrations can be found here:

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That diagram is valuable to try to prove to newer players that when the object ball is near the head or foot spot and the cue ball is near the center of the table, even though the tangent line for the cue ball heads directly towards the pocket, it’s not a scratch shot to cut the ball in the corner. As long as you hit it with a softer stroke and just roll the cue ball, the cue ball will strike the end cushion.
 
Bob Jewett said:
Another place a lot of people go wrong in this kind of situation is that as they crank up the speed for follow shots they fail to keep the quality of the follow constant. If you hit at 50% follow and softly, the cue ball will arrive with 100% follow if there enough time for the cue ball to start rolling smoothly before it gets to the object ball. If you hit at 50% follow and medium-hard, it may be that the cue ball arrives with only 60% follow having had only time enough to get 10% towards smooth rolling. The shooter might think that the angle changed but what really changed was the percentage of full follow at contact.
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So practically, do you have to hit with more follow as you crank up the speed to keep the actual follow at impact constant? If you hit with more follow does the CB start rolling sooner?
 
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7stud said:
So practically, do you have to hit with more follow as you crank up the speed to keep the actual follow at impact constant? If you hit with more follow does the CB start rolling sooner?
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A good solution is to play with the tip contacting the cue ball at 70% of its height. That will cause it to start rolling smoothly immediately. And if you are a little off from 70% the smooth rolling can set in quickly.

In my experience very few beginners and intermediates ever hit the cue ball at 70% of its height. They hit lower to avoid miscues. The problem shows up when they try to get good follow on a close object ball. They hit hard and the cue ball barely follows a couple of diamonds. From back farther they get good follow because the table gives it to them.
 
If the cue ball is 2.25 inches in diameter,

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0.70 * 2.25 inches = 1.575 inches above the surface of the table.

The center of the cue ball is 1 1/8" above the table or 1.125 inches. Subtracting the center height from the 70% height above the table gives:

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1.575 inches - 1.125 inches = 0.45 inches above the center of the cue ball.

Converting to millimeters:

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0.45 inch * 25.4mm/inch = 11.4mm above the center of the cue ball.

The miscue limit is 14.3mm above center ball.
 
7stud said:
... The miscue limit is 14.3mm above center ball.
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I didn't follow all of your calculations....

If you place a stripe with the stripe horizontal and your tip strikes the ball (as evidenced by the chalk spot) just below the white cap -- chalk spot all on the color -- that is 70% on most ball designs.
 
I think I may have also gleaned my misconception about the CB initially traveling along the tangent line from this Dr. Dave article:

David Alciatore (“Dr. Dave”) ILLUSTRATED PRINCIPLES “Draw Shot Primer – Part I: physics”
Note: Supporting narrated video (NV) demonstrations, high-speed video (HSV) clips, and technical proofs (TP) can be accessed and viewed online at billiards.colostate.edu. The reference numbers used in the article (e.g., NV 3.8) help you locate the resources on the website. If you have a slow or inconvenient Internet connection, you might want to view the resources offline using a CD-ROM. See the website for details.
Over the next few months, I will be presenting a series of articles dealing with draw shot principles. The goal is for the reader to come away with some useful information and systems for becoming more effective at planning and executing draw shots. In my January-July, 2004 articles (available on my website), I showed how the 90° and 30° rules are extremely useful tools in planning stun and follow shots. Therefore, the natural question is: “Well, what about draw shots ... is there a similar rule for them?” Well, let’s start by exploring some basic physics so we can try to come away with some useful tools.
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wherein it states:

Screen Shot 2023-02-12 at 10.03.17 AM.png


Principle 28 should probably read:

Screen-Shot-2023-02-12-at-10.03.17-AM.jpg
 
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Practically speaking, what I wrote is true. Technically speaking, the CB starts coming back from the tangent line immediately (but just barely at first with faster speeds).
 
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