physics-based draw shot advice

[dr_dave]

I just completed a very thorough analysis of draw shot physics. Don't get too excited, now. :grin:

The analysis has resulted in what I think are several useful conclusions, most of which agree with my intuition as a player. However, I think some of the conclusions might surprise some people, even experienced players. That's why I wanted to post them here. Please comment on the conclusions, especially the ones that might go against your judgment or intuition as a player. Are there special shots or situations where you would do something different from what is suggested?

Here's the list of conclusion, which can be found at the end of TP B.8 (all of the graphs referenced below are clearly labeled in the analysis if you want to check them out):

1. Generally, to get more draw, you must hit the cue ball harder and lower (see graphs A and G).
2. More tip offset does not produce more draw as you approach the miscue limit, so it is prudent to not hit too close to the miscue limit (see graphs A and G).
3. With larger drag distances and more power, max draw occurs at less than maximum tip offset (see Graphs G, Q, S, and U, and see the data on the previous page), so you get more draw by hitting the CB closer to center!
4. With a draw shot, for a desired draw distance, a slower cue speed with more tip offset will result in better CB position control than a faster cue speed with less offset (see the slopes of the curves in Graphs A and G at a given draw distance).
5. Stop shots (draw distance = 0) are much less sensitive to tip offset position than draw shots are (see Graphs G, H, I, N, and O). In other words, CB position is much easier to control with a stop shot, as compared to a draw shot.
6. For a short stop shot, slower speed offers slightly better control (see the overall slopes of the curves in Graph I). For longer stop shots, faster speed appears to offer slightly better control (see Graphs N and O).
7. For stun-through (small controlled follow) and stun-back (small controlled draw), a firmer hit closer to center offers better CB control (see Graphs L and M).
8. It is much easier to control draw distance on a new, slick cloth than it is on a "sticky" cloth, especially with lower-speed shots (see Graph T).

Thank you in advance for sharing your comments, thoughts, and experiences,
Dave

 

[TheBook]

A lot of good stuff and things to think about. Thanks for sharing.

Have you done any study about the effect of differences in chalk, tip diameters, tip radius, or tip hardness?

Does amount of follow thru have any affect?

 

[dr_dave]

A lot of good stuff and things to think about. Thanks for sharing.

Thank you ... and you're welcome.

Have you done any study about the effect of differences in chalk, tip diameters, tip radius, or tip hardness?

I have some info here:

- "tips" of English
- cue tip info

but I have not performed a rigorous physics-based study of this stuff.

Does amount of follow thru have any affect?

Follow through is a symptom of a good stroke, but it does not have a direct effect, IMO. For more info, see:

http://billiards.colostate.edu/threads/stroke.html#follow-through​

Regards,
Dave

 

[dr_dave]

I won't be online again until tomorrow, but I look forward to reading your comments.

Regards,
Dave

I just completed a very thorough analysis of draw shot physics. Don't get too excited, now. :grin:

The analysis has resulted in what I think are several useful conclusions, most of which agree with my intuition as a player. However, I think some of the conclusions might surprise some people, even experienced players. That's why I wanted to post them here. Please comment on the conclusions, especially the ones that might go against your judgment or intuition as a player. Are there special shots or situations where you would do something different from what is suggested?

Here's the list of conclusion, which can be found at the end of TP B.8 (all of the graphs referenced below are clearly labeled in the analysis if you want to check them out):

1. Generally, to get more draw, you must hit the cue ball harder and lower (see graphs A and G).
2. More tip offset does not produce more draw as you approach the miscue limit, so it is prudent to not hit too close to the miscue limit (see graphs A and G).
3. With larger drag distances and more power, max draw occurs at less than maximum tip offset (see Graphs G, Q, S, and U, and see the data on the previous page), so you get more draw by hitting the CB closer to center!
4. With a draw shot, for a desired draw distance, a slower cue speed with more tip offset will result in better CB position control than a faster cue speed with less offset (see the slopes of the curves in Graphs A and G at a given draw distance).
5. Stop shots (draw distance = 0) are much less sensitive to tip offset position than draw shots are (see Graphs G, H, I, N, and O). In other words, CB position is much easier to control with a stop shot, as compared to a draw shot.
6. For a short stop shot, slower speed offers slightly better control (see the overall slopes of the curves in Graph I). For longer stop shots, faster speed appears to offer slightly better control (see Graphs N and O).
7. For stun-through (small controlled follow) and stun-back (small controlled draw), a firmer hit closer to center offers better CB control (see Graphs L and M).
8. It is much easier to control draw distance on a new, slick cloth than it is on a "sticky" cloth, especially with lower-speed shots (see Graph T).

Thank you in advance for sharing your comments, thoughts, and experiences,
Dave

 

[pool_rob9]

Note that pacing of stroke also makes a huge difference in draw, as well as completing the stroke to a finish. It comes down to duration of contact as well as friction created between the tip and cue ball. My basic theory is a smooth, decelerating stroke that finishes down to the table(not digging down but simply staying down and fishing off the stroke without lifting the cue) will maintain a contact that allows the cue ball to rotate. This also lends itself to point #3 above in that a longer duration of tip contact will produce more spin. An accelerating stroke (punch) almost puts a braking effect between the tip and cue ball that prevents rotation and results in a stun or stop shot. The deceleration isn't exagerated but can be thought of as a pendilum's motion in relation to your arm. Just my theory. I could be wrong.

 

[pooltchr]

I[*]It is much easier to control draw distance on a new, slick cloth than it is on a "sticky" cloth, especially with lower-speed shots (see Graph T).[/LIST]

Thank you in advance for sharing your comments, thoughts, and experiences,
Dave

I'm not sure I buy into this one, Dave. While equipment conditions will change the way the balls react, one surface is not necessarily harder or easier to control draw distance. The player will still control draw distance by changing the amount of speed and spin applied to the cue ball. So while some players may adjust quickly to new cloth, others may not. But it's like everything in pool...the player who adjusts to the equipment quickest, usually has an advantage.

Steve

 

[pooltchr]

Note that pacing of stroke also makes a huge difference in draw, as well as completing the stroke to a finish. Not necessarily. I can accomplish draw without finishing my stroke. I wouldn't want to...but I could. It comes down to duration of contact The duration of contact is fairly constant at between one and two one-thousands of a secondas well as friction created between the tip and cue ball. My basic theory is a smooth, decelerating stroke that finishes down to the table(not digging down but simply staying down and fishing off the stroke without lifting the cue) will maintain a contact that allows the cue ball to rotate. With the exception of the "decelerating" part,you have described the kind of stroke we encourage out students to develop in pool school, but again, it's almost impossible to maintain contact longer than 1-2/1000 sec. This also lends itself to point #3 above in that a longer duration of tip contact will produce more spin. You can't control duration of contact. You have control over tip placement on the cue, and the speed the cue is moving at contact. Those are the two variables involved with draw. Speed and Spin. An accelerating stroke (punch) almost puts a braking effect between the tip and cue ball that prevents rotation and results in a stun or stop shot. The deceleration isn't exagerated but can be thought of as a pendilum's motion in relation to your arm. Just my theory. I could be wrong.

We want acceleration at contact as it gives us a consistent reaction. An accelerating stroke is not what most people call a punch stroke, but rather a result of a well delivered stroke.

Steve

 

[pool_rob9]

Acceleration up to contact then deceleration through. http://billiards.colostate.edu/technical_proofs/new/TP_A-9.pdf
subcribing to this theory given to me by a grumpy old man(lol thanks tom) made a night and day difference for me if only a mental trick and not physics. Different strokes for different folks (bad pun lol.) The hit it better not harder school of thought. Works for follow too.

 

[PetToilet]

i always enjoy your articles as an engineer, dr_dave, if it wasn't for your physics based site i wouldn't have gotten into pool. i have yet to find a more useful read than your summary of throw.

have you made any conclusions as elevation? of course some elevation is necessary, more elevation results in a higher percentage of rotational speed versus motion in the horizontal plane, while the vertical motion seems to eat rotational spin more than sliding across the cloth.

The hit it better not harder school of thought. Works for follow too.

accelerating while hitting the cue ball has nothing do with hitting it harder. I apply to the accelerating while hitting simply because slowing down requires the use of other muscles, and i want my stroke to comprise of the least amount of muscles as possible until after contact.

 

[dr_dave]

Note that pacing of stroke also makes a huge difference in draw, as well as completing the stroke to a finish. It comes down to duration of contact as well as friction created between the tip and cue ball. My basic theory is a smooth, decelerating stroke that finishes down to the table(not digging down but simply staying down and fishing off the stroke without lifting the cue) will maintain a contact that allows the cue ball to rotate.

The only thing the CB "cares" about is speed, offset, and elevation of the cue at impact. The grip hand cannot have much effect during impact. Now, a long, smooth, and non-jerky stroke might help you achieve good cue speed, and it will result in a natural and complete follow through. You don't have any control over "duration of contact."

This also lends itself to point #3 above in that a longer duration of tip contact will produce more spin. An accelerating stroke (punch) almost puts a braking effect between the tip and cue ball that prevents rotation and results in a stun or stop shot. The deceleration isn't exagerated but can be thought of as a pendilum's motion in relation to your arm. Just my theory. I could be wrong.

Check out the video and other links here:

http://billiards.colostate.edu/threads/stroke.html#acceleration​

I think your understanding of the physics and terminology of acceleration is a little off.

Regards,
Dave

 

[dr_dave]

8. It is much easier to control draw distance on a new, slick cloth than it is on a "sticky" cloth, especially with lower-speed shots (see Graph T).

I'm not sure I buy into this one, Dave. While equipment conditions will change the way the balls react, one surface is not necessarily harder or easier to control draw distance. The player will still control draw distance by changing the amount of speed and spin applied to the cue ball. So while some players may adjust quickly to new cloth, others may not. But it's like everything in pool...the player who adjusts to the equipment quickest, usually has an advantage.

Steve,

I wasn't implying that a player can adjust faster to slick cloth vs. sticky cloth. Any player will need to adjust when playing under different cloth conditions. My statement assumes the player is equally well "adjusted" to each cloth condition.

The physics suggests draw distance control is easier on a slick cloth, as compared to a sticky cloth, assuming the player is equally well adjusted to both conditions.

It is also easier to draw on slick cloth, but this is a separate issue.

Regards,
Dave

 

[dr_dave]

We want acceleration at contact as it gives us a consistent reaction. An accelerating stroke is not what most people call a punch stroke, but rather a result of a well delivered stroke.

Steve,

I think I know what you mean; but with a typical pendulum stroke, the cue is not accelerating at all during tip contact. The speed increases smoothly, but it levels off close to ball contact (i.e., the cue "coasts" into the ball with nearly constant speed at contact). Acceleration is the rate of change of speed, so there is no acceleration at tip contact. For more info, see:

HSV B.40 - stroke speed and acceleration analysis, with Bob Jewett​

and

http://billiards.colostate.edu/threads/stroke.html#acceleration​

Regards,
Dave

 

[dr_dave]

i always enjoy your articles as an engineer, dr_dave, if it wasn't for your physics based site i wouldn't have gotten into pool. i have yet to find a more useful read than your summary of throw.

Thank you for you kind words. And I'm glad my site has helped inspire you to play.

have you made any conclusions as elevation?

That's to come in "Part II" of my analysis.

accelerating while hitting the cue ball has nothing do with hitting it harder.

Agreed.

I apply to the accelerating while hitting simply because slowing down requires the use of other muscles, and i want my stroke to comprise of the least amount of muscles as possible until after contact.

See message 12 (my reply to Steve). If the speed levels off at contact, this does not mean there is deceleration. The acceleration drops and the speed levels off, but this doesn't represent deceleration. Deceleration would imply a decrease in speed. The accelerating muscles relax toward tip contact, but the decelerating muscles don't activate until after tip contact.

Regards,
Dave

 

[dr_dave]

3. With larger drag distances and more power, max draw occurs at less than maximum tip offset , so you get more draw by hitting the CB closer to center!

Was anybody else surprised by this conclusion? When I was working on the analysis, I had spoken to Bob Jewett on the phone to get his sense on this, and he told me this was consistent with his experiences. Therefore, I am glad the results show it.

Is this consistent with the experience of others? I've tried to test this myself on my table, and I think I believe it, but it still seems counter intuitive to me (even though I know and believe the physics).

Regards,
Dave

 

[Jal]

Was anybody else surprised by this conclusion? When I was working on the analysis, I had spoken to Bob Jewett on the phone to get his sense on this, and he told me this was consistent with his experiences. Therefore, I am glad the results show it.

Is this consistent with the experience of others? I've tried to test this myself on my table, and I think I believe it, but it still seems counter intuitive to me (even though I know and believe the physics).

Regards,
Dave

Dr. Dave,

Referring to the above, you said: "3. With larger drag distances and more power, max draw occurs at less than maximum tip offset (see Graphs G, Q, S, and U, and see the data on the previous page), so you get more draw by hitting the CB closer to center!"

Haven't had the time to take in your work on this yet, but I completely agree with this particular conclusion. According to the math I've done, if you can generate enough cue speed, hitting lower all the way down to the miscue limit will get you more draw. But the big IF is "generate enough cue speed." For a given distance (largish) between the balls, and a limited maximum cue speed one can accurately produce, hitting higher than the miscue limit does in fact produce more draw. It all depends on the ball separation distance and just how much cue speed you can or are willing to generate.

Conclusion #7: "For stun-through (small controlled follow) and stun-back (small controlled draw), a firmer hit closer to center offers better CB control (see Graphs L and M)." is in accord with my experience.

Conclusions #4 & #6 are particularly intriguing, and on the face of it seem to contradict #7 a little (not that I'm challenging them!).

I hope to get into it soon as it looks like you've provided another extremely useful analysis for the rest of us. Thank you once again.

Jim

 

[dr_dave]

Referring to the above, you said: "3. With larger drag distances and more power, max draw occurs at less than maximum tip offset (see Graphs G, Q, S, and U, and see the data on the previous page), so you get more draw by hitting the CB closer to center!"

Haven't had the time to take in your work on this yet, but I completely agree with this particular conclusion. According to the math I've done, if you can generate enough cue speed, hitting lower all the way down to the miscue limit will get you more draw. But the big IF is "generate enough cue speed." For a given distance (largish) between the balls, and a limited maximum cue speed one can accurately produce, hitting higher than the miscue limit does in fact produce more draw. It all depends on the ball separation distance and just how much cue speed you can or are willing to generate.

Jim,

Thanks for the reply. It is helpful to have somebody else support and discuss the conclusions. I'm still hoping some of the veteran non-physics "players" on the board can also contribute their comments and experience.

Conclusion #7: "For stun-through (small controlled follow) and stun-back (small controlled draw), a firmer hit closer to center offers better CB control (see Graphs L and M)." is in accord with my experience.

Good. More validation.

Conclusions #4 & #6 are particularly intriguing, and on the face of it seem to contradict #7 a little (not that I'm challenging them!).

4. With a draw shot, for a desired draw distance, a slower cue speed with more tip offset will result in better CB position control than a faster cue speed with less offset (see the slopes of the curves in Graphs A and G at a given draw distance).

6. For a short stop shot, slower speed offers slightly better control (see the overall slopes of the curves in Graph I). For longer stop shots, faster speed appears to offer slightly better control (see Graphs N and O).

7. For stun-through (small controlled follow) and stun-back (small controlled draw), a firmer hit closer to center offers better CB control (see Graphs L and M).

Good point about the apparent contradiction. I guess the key is the amount of draw. For a small amount of draw or follow, the results seem to suggest a firmer hit, closer to center, is better for CB draw/follow distance control. I need to think about this more also. Please let me know if you get any additional insight on this. It would also be helpful to hear from some of the veteran "players" out there on this topic.

I hope to get into it soon as it looks like you've provided another extremely useful analysis for the rest of us. Thank you once again.

Thanks Jim. I look forward to your critical (and helpful) review. I appreciate all of the help you have provided over the years in "keeping me honest."

Regards,
Dave

 

[Andrew Manning]

Was anybody else surprised by this conclusion? When I was working on the analysis, I had spoken to Bob Jewett on the phone to get his sense on this, and he told me this was consistent with his experiences. Therefore, I am glad the results show it.

Is this consistent with the experience of others? I've tried to test this myself on my table, and I think I believe it, but it still seems counter intuitive to me (even though I know and believe the physics).

Regards,
Dave

Dave, I'd be very interested to know why this occurs. Is it that hitting too low doesn't impart enough translational speed, and that the decreased speed means increased time before contacting the OB, and that in this increased time you lose too much spin to friction? I've sometimes felt that when I hit a long draw shot really low, it feels like I don't get sufficient speed even with my hardest controlled stroke. I feel this is one instance where elevation might help, since the airborne ball would not be exposed to the friction of the cloth for some significant part of its travel time.

-Andrew

 

[dr_dave]

With larger drag distances and more power, max draw occurs at less than maximum tip offset (see Graphs G, Q, S, and U, and see the data on the previous page), so you get more draw by hitting the CB closer to center!

Dave, I'd be very interested to know why this occurs. Is it that hitting too low doesn't impart enough translational speed, and that the decreased speed means increased time before contacting the OB, and that in this increased time you lose too much spin to friction? I've sometimes felt that when I hit a long draw shot really low, it feels like I don't get sufficient speed even with my hardest controlled stroke.

You hit the nail on the head. Good job.

I feel this is one instance where elevation might help, since the airborne ball would not be exposed to the friction of the cloth for some significant part of its travel time.

I will be looking at this closer. The downside of elevation is: driving the CB into the table can make it lose significant spin right off the tip. The amount of spin at the OB will also depend on where the CB bounces relative to the OB. I will be looking at this stuff much closer in "Part II" of the analysis.

Regards,
Dave

 

[woody_968]

Was anybody else surprised by this conclusion?

I was surprised, Ill be watching this thread and mess with this next time I get to the poolroom.

Woody

 

[rackmsuckr]

I have always struggled with a long or power draw, but I was watching Michell Monk this weekend and noticed how flat her hand was when drawing and she gets exceptional, smooth draw, which I commented on. She also cues so low, it looks like the underside of her cue is laying on the table. I had been using a closed bridge as well, except that my fingers were tented a bit and then I was accelerating through the cueball at a slight angle.

Improving my hand position to basically flat on the table has helped enormously. Thanks Michell. :thumbup:

I also turn my front foot in to almost parallel to the table. It swings my hips sideways so I can follow through to my chest easier and straighter. Not everyone has to go through this step, but for me, it has helped a lot.