Why are stop shots easier than going forward or back a little?

BRussell

BRussell

AzB Silver Member
Silver Member
In theory it should be no harder to stop than to go forward or backward an inch. Is it just that stop shots are practiced more often, or is there a larger margin of error for a stop shot? Or is there really no difference in difficulty and it just seems like it?
 
it's not easier in theory
the margin of error is much easier when gauging a sliding cue ball

one inch either way on a straight long shot is very tough
 
If I understand you correctly, larger margin for error on a stop shot. Cueball could be in skid for a whole 1-2 feet, while slightly back or slightly forward requires only a smidge of revolution on the cueball, which occurs in a smaller window linearly.
 
BRussell said:
In theory it should be no harder to stop than to go forward or backward an inch. Is it just that stop shots are practiced more often, or is there a larger margin of error for a stop shot? Or is there really no difference in difficulty and it just seems like it?
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The biggest difference is the zone of what one calls a good {stop, roll, draw}.
Much of the time a stop shot has a whole diamond of "good next shot".
Many times a follow or draw has to navigate through interfering balls much closer together than the same diamond mentioned above.
 
DJ14.1 said:
If I understand you correctly, larger margin for error on a stop shot. Cueball could be in skid for a whole 1-2 feet, while slightly back or slightly forward requires only a smidge of revolution on the cueball, which occurs in a smaller window linearly.
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I think perfect sliding (no forward or backward rotation at all) only lasts a moment. But there's probably a short span before and after the perfect sliding state where the amount of rotation is little enough to be "killed" by contact with the OB.

pj
chgo
 
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smashmouth said:
it's not easier in theory
the margin of error is much easier when gauging a sliding cue ball

one inch either way on a straight long shot is very tough
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That's what it seems like to me; I'm wondering why. I really don't understand why a cue ball should be sliding longer than it's spinning backward or rolling forward a particular amount.
 
DJ14.1 said:
If I understand you correctly, larger margin for error on a stop shot. Cueball could be in skid for a whole 1-2 feet, while slightly back or slightly forward requires only a smidge of revolution on the cueball, which occurs in a smaller window linearly.
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So you're saying the cue ball is spinning backward, then a little less, then slides for 1-2 feet, then rolls, and rolls a little more, etc. I'm not sure about that. It looks to me like the cue ball only slides for an instant before turning into roll.
 
because we practice stop shots more.....:eek:
a half tip up or down will achieve the forward and back
 
BRussell said:
So you're saying the cue ball is spinning backward, then a little less, then slides for 1-2 feet, then rolls, and rolls a little more, etc. I'm not sure about that. It looks to me like the cue ball only slides for an instant before turning into roll.
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Practice stop shots with a stripe as the cb. Set the stripe horizontally, then you can easily watch the spin, when it decays into slide, and when it rolls forward etc.

The slight draw, and slight follow are touch shots that require very precise tip placement on the cb, as much as the speed of the stroke IMO because the 2 have to work together. You can get the same results out of a firmer hit closer to ccb, as you can going further off center and using a kill stroke on the cb.
 
The distance a cue ball will go forward or back after an attempted stop shot is proportional to the square of how much follow/draw it has at impact (how many RPMs). The amount of follow/draw is changing more or less at a constant rate as the drawn cue ball goes towards the object ball.

The result of that is that the distance traveled by the cue ball after contact is proportional to a parabola where the bottom of the parabola is when there is no spin at contact and the x-axis is roughly the distance error in when pure slide occurs. In simple terms, if you have an error in the amount of draw that sends the cue ball forward a ball diameter, twice as much error will cause the cue ball to roll forward not two ball diameters but rather four.

Bottom line: stop shots are much easier to make precisely than "stun forward six inches" shots.

This was covered in my column in Billiards Digest a few years ago.
 
I have given lots of lessons to C players and below and I found the exact opposite.
They can usually make balls pretty well with draw or follow, as soon as I ask them to shoot a stop shot , their make percentage, almost always goes down quite a bit.
 
Thanks Bob - I'm trying to find the article but no luck so far.


book collector said:
I have given lots of lessons to C players and below and I found the exact opposite.
They can usually make balls pretty well with draw or follow, as soon as I ask them to shoot a stop shot , their make percentage, almost always goes down quite a bit.
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I'm talking about cue ball control, not making the shot, but I can see that it wasn't clear in my post.
 
Bob Jewett said:
The distance a cue ball will go forward or back after an attempted stop shot is proportional to the square of how much follow/draw it has at impact (how many RPMs). The amount of follow/draw is changing more or less at a constant rate as the drawn cue ball goes towards the object ball.

The result of that is that the distance traveled by the cue ball after contact is proportional to a parabola where the bottom of the parabola is when there is no spin at contact and the x-axis is roughly the distance error in when pure slide occurs. In simple terms, if you have an error in the amount of draw that sends the cue ball forward a ball diameter, twice as much error will cause the cue ball to roll forward not two ball diameters but rather four.

Bottom line: stop shots are much easier to make precisely than "stun forward six inches" shots.

This was covered in my column in Billiards Digest a few years ago.
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Thanks for the insight. But I think the square relationship between CB roll and distance is only half the reason why stun shots are much easier than "stun-forward" shots. Even if the relationship were linear, stun shots would still be considerably harder.

It seems the more dominant reason (why it's harder to precisely control stun-forward shots compared to stop shots) has to do with the relatively small amount of time the CB experiences the desired roll rate (to move forward a few inches), compared to the much larger amount of time the CB experiences very little or no forward roll (before impact with the CB).

Looking at it another way, even with a linear relationship between CB roll and CB distance, for a given CB roll margin of error window in RPMs (e.g. +/- 50 RPMs), the distance the CB travels in that MOE window is much greater for a stun shot compared to the stun-forward shot. The issue then gets compounded by the actual square relationship you mentioned before.
 
I have a decent handle on drawing back slighty/some/a lot and stop shots. Stun follow or force follow shots are a totally different ball game for me and most people, from what I have seen. Shooting center or below will always create a sliding cue ball at some point for varying distances/periods of time. In order its tough to time the cueballs transition from draw to sliding to follow to move the cueball 3-6 inches forward. Shooting slightly above with a somewhat firm stroke is also really difficult because the cue-ball stays on the tangent line longer unless the shot is near perfectly straight. Mind you this method creates plenty of options that are fun to experiment with.
 
Bob Jewett said:
It's the first article in this file: http://www.sfbilliards.com/articles/1997.pdf
It seems that "a few years ago" is about 19.
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Pretty funny.

That makes sense that it's easier to stop within, say, a few inches of the object ball than it is to draw to within a few inches of two feet behind the object ball.

But if I'm understanding it correctly it doesn't explain how - if it's even true - it's so much easier to dead stop than drift an inch.
 
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jsp said:
Thanks for the insight. But I think the square relationship between CB roll and distance is only half the reason why stun shots are much easier than "stun-forward" shots. Even if the relationship were linear, stun shots would still be considerably harder.

It seems the more dominant reason (why it's harder to precisely control stun-forward shots compared to stop shots) has to do with the relatively small amount of time the CB experiences the desired roll rate (to move forward a few inches), compared to the much larger amount of time the CB experiences very little or no forward roll (before impact with the CB).

Looking at it another way, even with a linear relationship between CB roll and CB distance, for a given CB roll margin of error window in RPMs (e.g. +/- 50 RPMs), the distance the CB travels in that MOE window is much greater for a stun shot compared to the stun-forward shot. The issue then gets compounded by the actual square relationship you mentioned before.
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Hmmm...looking at one of Dr. Dave's technical proofs (TP_4-1), the relationship between CB roll and CB distance for stun/draw shots (before impact with the CB) is much more linear than I expected (see graph on last page). I was expecting a much more exaggerated parabola or even an exponential. Assuming the curves are correct, then the error is dominated by what Bob has mentioned.
 
Patrick Johnson said:
I think perfect sliding (no forward or backward rotation at all) only lasts a moment. But there's probably a short span before and after the perfect sliding state where the amount of rotation is little enough to be "killed" by contact with the OB.
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I think this is the main reason a stop shot is relatively easy at all distances (in addition to the fact that we practice and play them often).

The CB has a small amount of top/bottom spin over a fairly large distance, especially with faster-speed shots, and the CB stops within a very short distance (or no distance at all) with a small amount of spin (or no spin).

For a more-technical proof, see:

TP B.8 - Draw shot physics

Specifically, see graphs "N" and "O" on page 17. These graphs show how much the CB draws back (d_draw) for draw/drag shots at different speeds and distances to the OB (d_drag). With the CB close to the OB (small d_drag), the CB draws back (d_draw>0). With the CB far from the OB (larger d_drag), and the same hit, the CB follows forward (d_draw<0). The graphs are very level near the stop-shot distance, especially for faster-speed shots (v3 > v1). That's the technical reason why stop shots are easier to control than precision draw or follow.

Regards,
Dave
 
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I am most accurate in follow shots in that I can do cross corner equal distance shots and have the cue ball follow the object ball into the corner more often then I can get a perfect stop shot or a backup shot.

I believe in my case it is because I am less accurate when hitting below center than I am hitting above center and when I try to backup the cue ball with a hard shot that adds to even less accuracy.

I was actually practicing this yesterday and hit 100 "stop" in a row, with maybe 20 perfectly stopped and the rest either going slightly left or right with some spin. I only missed making the OB 3 times.

I then did 60 follow shoots and followed it in over the marked spot behind the object ball 19 times and just missed on every other shoot. I never missed the object ball.

Draw shots I did 60 and had 2 actually come back into the corner and maybe 10 others come between the chalk spots I had 18"s behind the object ball I was drawing from. With that, I probably also missed 15-20 of the shots regardless of the accuracy of the draw back.
 
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