Aim system for rail shots from every position?

phcore said:

1. Is there aim system for rail shots to hit OB through rail from any of her position?

2. Can someone explain me physics of rail shots? Everywhere i read there are some compensations with this type of shot. I mean when i hit ball from pocket to 1/2 of 1/2 pool table it never goes to middle pocket only a little closer. Shouldnt it be the angle of incidence equals the angle of reflection?

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Assuming you mean banks or kicks...

"Equal angle" rebound only happens with mirrors and light. Friction between the ball and the cushion cloth changes that. The largest changes happen because of the ball's rotation, but some change happens even without any ball rotation.

A full list of all the possible friction effects would probably only confuse things for you here - but they're pretty logical.

There are lots of systems and discussions of them. Do a search.

pj
chgo

phcore said:

1. Is there aim system for rail shots to hit OB through rail from any of her position?

2. Can someone explain me physics of rail shots? Everywhere i read there are some compensations with this type of shot. I mean when i hit ball from pocket to 1/2 of 1/2 pool table it never goes to middle pocket only a little closer. Shouldnt it be the angle of incidence equals the angle of reflection?

Click to expand...

The cue ball sinks into the rail (cushion), which makes the angle of reflection smaller than the angle of incidence. A harder hit equals shorter reflection angle.

Plus, if you are using the center diamond to aim the cue ball, it hits the rail short of that diamond because the diamond is a few inches back. So you either have to aim a little past the diamond or use a tiny bit of english toward the direction you want the cue ball to go after it contacts the cushion.

BC21 said:

The cue ball sinks into the rail (cushion), which makes the angle of reflection smaller than the angle of incidence. A harder hit equals shorter reflection angle.

Plus, if you are using the center diamond to aim the cue ball, it hits the rail short of that diamond because the diamond is a few inches back. So you either have to aim a little past the diamond or use a tiny bit of english toward the direction you want the cue ball to go after it contacts the cushion.

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Sorry, I gotta disagree with both of these...

1. It isn't the CB sinking into the cushion that shortens the rebound angle; it's rail/cloth friction holding its "parallel-to-the-rail" motion back.

2. That shortening friction only holds true if the CB is sliding (no forward or back spin) when it hits the rail. Otherwise its forward roll makes it masse "forward" after rebound, going longer/wider than the equal angle. Aiming at the diamond hits the rail a little short, as you say, but is the (approximate) correct aim for a normally rolling ball.

pj
chgo

Patrick Johnson said:

Sorry, I gotta disagree with both of these...

1. It isn't the CB sinking into the cushion that shortens the rebound angle; it's rail/cloth friction holding its "parallel-to-the-rail" motion back.

2. That shortening friction only holds true if the CB is sliding (no forward or back spin) when it hits the rail. Otherwise its forward roll makes it masse "forward" after rebound, going longer/wider than the equal angle. Aiming at the diamond hits the rail a little short, as you say, but is the (approximate) correct aim for a normally rolling ball.

pj
chgo

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It doesn't surprise me that you disagree. Lol.

I'm speaking in the simplest terms possible when I say the cb sinks into the cushion and then departs at a smaller/tighter angle than its approach angle. That's what happens. No need to go into the frictional details to explain why this happens. Basically, the harder you hit it the shorter the rebound angle.

Shoot the cb with a medium or soft rolling speed from a corner pocket to the 2nd diamond on the long rail. On most tables the cb will scratch perfectly in the opposite side pocket. Shoot it a little firmer, still with a normal forward roll, and it'll come out short, might still hit the pocket, but more than likely hit the point of the side pocket facing. Now shoot the same kick again but hit it very firm with no spin. It will land very short of the side pocket. Now of course you could load it up with top, draw, inside or outside english, and manipulate this rebound angle all you want in accordance with what you need. At wider angles, even the example I used above, top spin doesn't immediately kick in. The cb comes off shorter first because it drives deeper into the cushion, then as it starts across the table it begins to bend forward. Hit it too hard and it might not bend forward enough before it hits the opposite rail. A lot of factors to consider.

Basically, PJ, I was simply describing (without any unnecessary details or going into all the factors) what generally happens to the outbound angle when the cb hits the cushion. :smile:

BC21 said:

The cb comes off shorter first because it drives deeper into the cushion

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This is the part that's a common misbelief - the CB doesn't rebound shorter because it drives deeper into the cushion. It shortens up because the CB hits the rail with less forward spin-to-speed, and/or slides farther after rebound before bending forward.

In fact, driving deeper into the cushion works against the shortening effects, actually widening the rebound a little as the ball rolls farther along the cushion before rebounding.

Not real important to know, but since we're talking about the details.

Here's a pic showing the relative paths of the ball's center with softer/harder hits.

pj
chgo

Patrick Johnson said:

This is the part that's a common misbelief - the CB doesn't rebound shorter because it drives deeper into the cushion. It shortens up because the CB hits the rail with less forward spin-to-speed, and/or slides farther after rebound before bending forward.

In fact, driving deeper into the cushion works against the shortening effects, actually widening the rebound a little as the ball rolls farther along the cushion before rebounding.

Not real important to know, but since we're talking about the details.

Here's a pic showing the relative paths of the ball's center with softer/harder hits.

pj
chgo

View attachment 515810

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In bold..... This is only true at wider kick angles, wider than the shot I used as an example. That shot, from corner to 2nd diamond on long rail comes off shorter with more speed as does every kick angle sharper than this, including your drawing. Shooting it a few times proves it. Players that can bank and kick well know it.

BC21 said:

In bold..... This is only true at wider kick angles, wider than the shot I used as an example.

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It's a small effect at any angle - not as visible on steeper banks.

That shot, from corner to 2nd diamond on long rail comes off shorter with more speed as does every kick angle sharper than this, including your drawing. Shooting it a few times proves it. Players that can bank and kick well know it.

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You misread me - I didn't say harder hit banks don't bank shorter; I questioned a reason for it (cushion compression)...

Patrick Johnson said:

This is the part that's a common misbelief - the CB doesn't rebound shorter because it drives deeper into the cushion. It shortens up because the CB hits the rail with less forward spin-to-speed, and/or slides farther after rebound before bending forward

Click to expand...

By the way, another reason we haven't mentioned for harder banks going shorter is "reverse masse" produced by the higher-than-center cushion nose. Another small effect, but they add up.

pj
chgo

..........

Patrick Johnson said:

It's a small effect at any angle - not as visible on steeper banks.


You misread me - I didn't say harder hit banks don't bank shorter; I questioned a reason for it (cushion compression)...


By the way, another reason we haven't mentioned for harder banks going shorter is "reverse masse" produced by the higher-than-center cushion nose. Another small effect, but they add up.

pj
chgo

Click to expand...

Very true. Nose height and cushion compression makes a difference. That's why different tables don't bank or take kick shots equally.