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View Full Version : Cue ball spin reacting on rails

07-15-2003, 01:21 PM
Man, am I confused. Say you hit the cue ball into the rail with a center ball hit (A). You do the same shot with draw and it closes the angle (B), follow opens it (C). wei (http://endeavor.med.nyu.edu/~wei/pool/pooltable2.html)
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Why then, if you add running english, draw at 4:30 on the CB (B) now opens up the angle the most, center english at 3 o'clock (A) opens it the second most and follow with english (C) opens it the least? Shouldn't it be in reverse order like the first shot?
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Am I making any sense here?

bluewolf
07-15-2003, 02:02 PM
How much draw did you put on the first shot vs the second? And how much running eng? Just curious.

Laura

Fran Crimi
07-15-2003, 02:44 PM
<blockquote><font class="small">Quote UTAddb:</font><hr> Man, am I confused. Say you hit the cue ball into the rail with a center ball hit (A). You do the same shot with draw and it closes the angle (B), follow opens it (C). wei (http://endeavor.med.nyu.edu/~wei/pool/pooltable2.html)
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Why then, if you add running english, draw at 4:30 on the CB (B) now opens up the angle the most, center english at 3 o'clock (A) opens it the second most and follow with english (C) opens it the least? Shouldn't it be in reverse order like the first shot?
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Am I making any sense here?

<hr /></blockquote>

Yes you are, and I can understand your confusion. I think I can answer it but we'll have to double check with Fred, our resident physics guru here.

I believe the answer lies in how much the cb is sliding off the rail. In your first example: When you apply draw, the cb will continue to slide until the backspin wears off, thus giving you your straightest line off the rail. With center ball, the cb will slide slightly off the rail, then pick up normal roll as it interacts with the cloth, which will begin to shorten the angle. With topspin, the cb slides the least, and picks up normal roll quicker, reacting the most to the angle into the shot.

In your second example, when you apply draw with sidespin, the cb is sliding off the rail and the reaction off the rail is all side, which gives you a strong reaction to the side. With center ball, you have initial cb slide reaction off the rail, initially sending it to the side, but it quickly picks up normal roll as it interacts with the cloth, causing the cb to straighten out a little. With topspin plus side, there is the least amount of cb slide, which gives you an immediate combination of side and normal roll off the rail, which lengthens the shot the most out of the three.

I think.

Fran

SpiderMan
07-15-2003, 04:24 PM
I'll add another dimension as well. When kicking with follow or draw, the cueball does not remain on the path dictated by it's angle off the rail. In many cases you use this instead of, or in addition to, side in order to modify the angle AND avoid an interfering ball:

Example #1, shot with follow only:

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Example #2, shot with draw only:

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I've heard that Grady Mathews can hit shot #2 from some unbelievable angles.

Rod Elliott showed me an interesting variation of shot #1 a couple of years ago. He made it on the second try, stroked hard with extreme follow:

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SpiderMan

Alfie
07-15-2003, 11:18 PM
<blockquote><font class="small">Quote UTAddb:</font><hr> [How different spins affect the rebound angle]<hr /></blockquote>I did a few quick and dirty runs.
9' table (http://endeavor.med.nyu.edu/~wei/pool/9egg/)
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The CB position for all shots was as shown. I hit the center of the short rail between two OBs that had 3.5" between them (paper donutted). The approximate rail hits are represented by OBs 1-6.
1 ball - 3:00 hit
2 - 1:30 and 4:30
3 - 12:00
4 - 6:00
5 - 7:30 and 10:30
6 - 9:00
The cue was hit at about 3.5 table length speed in an effort to lessen swerve. The hit offsets were just a bit inside of the miscue limit. The rail cloth is a year old (pool room). Maybe newer, cleaner cloth would have a different affect.

The purely side spins at 3:00 and 9:00 had a much greater affect than the purely high and low spins at 12:00 and 6:00. The in between offset pairs showed little difference when it came to high and low spin. When there are equal amounts of verticle and horizontal offset it's the side spin that dominates.

I'll leave it to someone else to do the quick and dirty at each half hour. :-)

Rod
07-16-2003, 12:56 AM
Follow makes the ball go long, it lengthens it by the effect of overspin, and climbs up the nose of the cushion. Center is a flat line, it doesn't want to go up or down the cushion. Low pulls the c/b under the nose and will make the ball go short.

For the same reason low right bites under the nose better and makes a wider angle. As shown in your diagram. Real technical terms here. LOL

If you look at this diagram you'll see low side has the largest effect on the c/b. Shoot from that starting point and bring the c/b back to the corner pocket, Line A, it goes way short of a natural roll, Line B. It seems to defy the rules. In fact it does bend a little on the way back. Line C, which is top right has little effect to the first rail because of the short distance. It's just something to know when you need to create an angle, where ever your shooting from. Of course these shots need to be shot at the same speed and english to see how much variance there is. wei (http://endeavor.med.nyu.edu/~wei/pool/9egg/)

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Fred Agnir
07-16-2003, 06:34 AM
<blockquote><font class="small">Quote UTAddb:</font><hr> Man, am I confused. Say you hit the cue ball into the rail with a center ball hit (A). You do the same shot with draw and it closes the angle (B), follow opens it (C).

wei (http://endeavor.med.nyu.edu/~wei/pool/pooltable2.html)
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Why then, if you add running english, draw at 4:30 on the CB (B) now opens up the angle the most, center english at 3 o'clock (A) opens it the second most and follow with english (C) opens it the least? Shouldn't it be in reverse order like the first shot?<hr /></blockquote>I would say that english on a cueball would have more affect than follow or draw, as far as the cueball's first motion off the cushion.

It would seem to me that straight sidespin (3:00) would have the most spin and therefore the most widening, if spin was the only thing happening. I would also further think that low and high english would have roughly the same amount of widening.

That being said, if you hit low with english from the rail like your diagram, are you putting a slight masse' on the cueball such that its initial path is altered by the time it hits the cushion? That could give you a false sense of "widening." You may actually be widening the incoming angle which results in a widened outgoing angle. It would take much difference in the path, given your diagram.

Try the same test the long way down the table at fast speeds. See what happens.

Fred

Fred Agnir
07-16-2003, 06:40 AM
<blockquote><font class="small">Quote Alfie:</font><hr> The cue was hit at about 3.5 table length speed in an effort to lessen swerve. <hr /></blockquote>And therein lies the difference, I believe. In his non-controlled experiment, swerve has tainted the observation making it seem like drawing with english creates the widest angle.

Fred

Fran Crimi
07-16-2003, 07:12 AM
<blockquote><font class="small">Quote Fred Agnir:</font><hr> <blockquote><font class="small">Quote Alfie:</font><hr> The cue was hit at about 3.5 table length speed in an effort to lessen swerve. <hr /></blockquote>And therein lies the difference, I believe. In his non-controlled experiment, swerve has tainted the observation making it seem like drawing with english creates the widest angle.

Fred <hr /></blockquote>

I take back what I wrote. You're right. I got the same result as UT, but I was definietly swerving the cb to the rail when I applied backspin.

Well, that dispells my whole theory on slide off the rail. Sounded good when I wrote it. /ccboard/images/graemlins/grin.gif

Fran