Can anyone make this shot?
- Thread starter BRussell
- Start date
Those explanations are how I had understood it. What’s surprising to me is that it still works despite the fact that on this shot 1. There’s no English on the cue ball, and 2. You’re cutting it the wrong way.
I’ve been trying to replicate it with the side pocket and I can’t do that either. I can easily do it with English or by cutting it the correct way, but not cutting it the wrong way.
Yes, I guess my precise question is "why" does the angle the ball go into the cushion cause the cushion to impart reverse spin on the ball. In contrast, when kicking the CB around the table contacting each rail in succession, each rail rubs on the CB, and increases the spin (I think). That makes sense, and one can visualize each rail spinning the CB as the CB touches it.
Back to the reversal:
I went to my table after your post, and pushed the CB with my hand very hard into the cushion, and watched how the cushion compressed. It must be "grabbing and releasing" the ball in such a way that causes the spin to "reverse" on certain angles. I know that is happening, these triple bank shots prove it. I just don't see with my eyes "how" these cushion compression effects accomplish this.
Ha ha, I've never tried it with juice. I think the first person who showed it to me 20 years ago said no spin. And I've hit it dead ball ever since.
The reason balls can reverse sharply off rails like this is rail compression.
The compression changes the direction of the ball, and also imparts some spin.
(spin will be imparted from contact with the rail regardless of compression,
but I think on a fast shot, compression imparts a lot of spin).
So on the right is what would happen if the cushion didn't compress/deform.
The ball would bounce off a perfectly flat, ruler-straight surface and rebound along a mirror angle.
On the left is what actually happens, the rubber compresses, and "cups" the ball.
So now it's bouncing off a curved surface.
The direction it rebounds, is determined by the part of the curve that is the most heavily compressed,
which is sort of perpendicular to the direction the ball is moving.
So in the above example, imagine the curved area of the cushion divided into 2 parts.
The part to the left of the cue ball's black arrow, and the part to the right.
The part to the right (marked with the red bar) is what gets compressed heavily,
and that has the most influence on the rebound angle.
It gets crushed, then decompresses and spits the ball back.
Meanwhile, the part of the rail to the left also compresses, but I think it has less influence on the direction of the ball
because it doesn't compress as heavily, so it doesn't snap back as forcefully.
The next part is just a guess/theory but I think that area on the left DOES impart a lot of spin, because for a split second,
a lot of the cue ball's surface is rubbing against the rail which is partially cupping it.
It's sort of like the ball is "scraping" that left portion of the rail as it attempts to "pass it by".
But of course it can't pass it, it hits the hard wall of rubber marked in red on the right.
This pic might help explain what I mean by the left part of the compressed area imparting lots of spin:
The compression changes the direction of the ball, and also imparts some spin.
(spin will be imparted from contact with the rail regardless of compression,
but I think on a fast shot, compression imparts a lot of spin).
So on the right is what would happen if the cushion didn't compress/deform.
The ball would bounce off a perfectly flat, ruler-straight surface and rebound along a mirror angle.
On the left is what actually happens, the rubber compresses, and "cups" the ball.
So now it's bouncing off a curved surface.
The direction it rebounds, is determined by the part of the curve that is the most heavily compressed,
which is sort of perpendicular to the direction the ball is moving.
So in the above example, imagine the curved area of the cushion divided into 2 parts.
The part to the left of the cue ball's black arrow, and the part to the right.
The part to the right (marked with the red bar) is what gets compressed heavily,
and that has the most influence on the rebound angle.
It gets crushed, then decompresses and spits the ball back.
Meanwhile, the part of the rail to the left also compresses, but I think it has less influence on the direction of the ball
because it doesn't compress as heavily, so it doesn't snap back as forcefully.
The next part is just a guess/theory but I think that area on the left DOES impart a lot of spin, because for a split second,
a lot of the cue ball's surface is rubbing against the rail which is partially cupping it.
It's sort of like the ball is "scraping" that left portion of the rail as it attempts to "pass it by".
But of course it can't pass it, it hits the hard wall of rubber marked in red on the right.
This pic might help explain what I mean by the left part of the compressed area imparting lots of spin:
The reason balls can reverse sharply off rails like this is rail compression.
The compression changes the direction of the ball, and also imparts some spin.
(spin will be imparted from contact with the rail regardless of compression,
but I think on a fast shot, compression imparts a lot of spin).
So on the right is what would happen if the cushion didn't compress/deform.
The ball would bounce off a perfectly flat, ruler-straight surface and rebound along a mirror angle.
On the left is what actually happens, the rubber compresses, and "cups" the ball.
So now it's bouncing off a curved surface.
The direction it rebounds, is determined by the part of the curve that is the most heavily compressed,
which is sort of perpendicular to the direction the ball is moving.
So in the above example, imagine the curved area of the cushion divided into 2 parts.
The part to the left of the cue ball's black arrow, and the part to the right.
The part to the right (marked with the red bar) is what gets compressed heavily,
and that has the most influence on the rebound angle.
It gets crushed, then decompresses and spits the ball back.
Meanwhile, the part of the rail to the left also compresses, but I think it has less influence on the direction of the ball
because it doesn't compress as heavily, so it doesn't snap back as forcefully.
The next part is just a guess/theory but I think that area on the left DOES impart a lot of spin, because for a split second,
a lot of the cue ball's surface is rubbing against the rail which is partially cupping it.
It's sort of like the ball is "scraping" that left portion of the rail as it attempts to "pass it by".
But of course it can't pass it, it hits the hard wall of rubber marked in red on the right.
This pic might help explain what I mean by the left part of the compressed area imparting lots of spin:
Good work. I understand what you are saying completely. It makes a lot of sense to me! Thanks.
However, maybe you missed it, but I will add to what you said to complete the picture....
(All of the below is from a birdseye view over the shot)
The second part of your explanation combined with your second and third pictures imply to me you are saying "on the way INTO the cushion, the left side of the cushion rubs against the ball, imparting counterclockwise spin". I do believe this is correct. However, this would not "reverse" the ball, but rather add running english to it.
If we apply what you said to the rebound portion of the path of the ball, then the left side of the cushion is now causing the ball to spin in the clockwise direction on the way OUT OF the cushion. This would now reverse the spin on the ball, and explain what is happening.
Good work, I think we got to the bottom of this
The running english is reverse english on the opposite cushion.Good work. I understand what you are saying completely. It makes a lot of sense to me! Thanks.
However, maybe you missed it, but I will add to what you said to complete the picture....
(All of the below is from a birdseye view over the shot)
The second part of your explanation combined with your second and third pictures imply to me you are saying "on the way INTO the cushion, the left side of the cushion rubs against the ball, imparting counterclockwise spin". I do believe this is correct. However, this would not "reverse" the ball, but rather add running english to it.
If we apply what you said to the rebound portion of the path of the ball, then the left side of the cushion is now causing the ball to spin in the clockwise direction on the way OUT OF the cushion. This would now reverse the spin on the ball, and explain what is happening.
Good work, I think we got to the bottom of this
Rail compression is not required to explain the shot. It is enough to have friction between the ball and the cushion as the ball moves somewhat sideways across the cushion.
Can you think of an experiment that would distinguish between rail compression (which seems to be something like the bunching up of the cushion material forward of the cue ball) and simple rail-ball friction?
Yes, true. But what we were getting to the bottom of is, within the "same cushion" the ball will go into it with clockwise spin, and rebound off of it with counter-clockwise spin.
https://youtu.be/sd_vA0ZPmgk
The shot also goes with outside spin. See above video. It seems like the cushion effect on the spin of the OB is much more significant than the initial spin on the CB.
Note, with outside spin I could 100% not make the shot when I had the OB on the center diamond (which is where it was on my prior high-speed video). I tried a good 20 minutes, and the closest I could get was just outside of the point. However, when I moved the OB one half diamond closer to the first rail, the outside spin shot became a hanger, and I could actually make it miss to the right side (from the shooter's perspective) of the target pocket. All three CB spins reacted this same way when moving the OB 1/2 diamond closer to the first rail. They all reversed significantly more than when the OB was in the center diamond.
The shot also goes with outside spin. See above video. It seems like the cushion effect on the spin of the OB is much more significant than the initial spin on the CB.
Note, with outside spin I could 100% not make the shot when I had the OB on the center diamond (which is where it was on my prior high-speed video). I tried a good 20 minutes, and the closest I could get was just outside of the point. However, when I moved the OB one half diamond closer to the first rail, the outside spin shot became a hanger, and I could actually make it miss to the right side (from the shooter's perspective) of the target pocket. All three CB spins reacted this same way when moving the OB 1/2 diamond closer to the first rail. They all reversed significantly more than when the OB was in the center diamond.
Very nice to see, thanks. Spin transfer seems irrelevant on these shots, it's all about the spin the ball gets from the first rail. From your videos it doesn't seem to spin after the first rail at all.
Apple's iphone X has a slow motion feature; I wonder if the video would have turned out better if used?
I used iPhone 7 which is 240 frames per second. I don't have iPhone X, but checked Apple's site, and it too is 240 frames per second.
What type of table are you on? What cloth and cloth condition? I'm on a GC4 with 6 year old Simonis 860.
I had the OB on the center spot, and the CB one diamond away. Both were exactly straight to the pocket, and on doughnuts for easy repeatability.
Maybe also try moving the OB half a diamond closer to the first rail. I was able to reverse it more from this position, surprisingly. Also slightly different speeds seemed to affect the outcome also, and change the shot from going in 2 rails vs 3 rails.
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I have about 5-year-old Simonis on my Olhausen. I can do the side pocket shot the way it's normally set up, but not with the balls set up to replicate their positions in Efren's shot, like this:
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I have about 5-year-old Simonis on my Olhausen. I can do the side pocket shot the way it's normally set up, but not with the balls set up to replicate their positions in Efren's shot, like this:
Ah, I see. I will try that on my table later, with Efren's angle, but going in the side.