Draw shot cue elevation effects

I saw an old video once ,maybe 20 years, ago by an instructor named Don Feeney. In that video he demonstrated (how in his determination) that a slightly elevated cue really helped reduce collision induced throw. Even with various side CB hits, but especially when hitting straight low with that old 'drag stroke' and letting the CB roll pure.
I'm not so sure about ALL of that, but I do know that it is helpful to me on those long cuts where the guy has you wedged up in a corner pocket and you can't stroke clean.
What is your opinion of his analysis?
TY.
I haven't come across Don's work before, but from what you've expressed, it seems he's in error.

An elevated cue would reduce CIT if it bounced onto the OB and hit it above normal levels, but attempting to do such is troublesome.

Being elevated often leads to firmer shots... I suspect that's where he is getting a feeling that elevation reduced throw.

Colin
 
I wonder if those who believe they get better draw by elevating their cue, sometimes get better draw because the cue ball is sometimes colliding with the object ball above the horizontal axis of the object ball?

I do believe that you can draw the cue ball back straighter if there is a cut angle to the shot, using an elevated cue. Is that better draw? :D
JoeyA
 
I wonder if those who believe they get better draw by elevating their cue, sometimes get better draw because the cue ball is sometimes colliding with the object ball above the horizontal axis of the object ball?

Seems to me this would result in less draw because the CB's forward momentum isn't fully transferred to the OB (a "vertical cut shot").

I do believe that you can draw the cue ball back straighter if there is a cut angle to the shot, using an elevated cue. Is that better draw?
Yes, elevating the cue produces a higher spin-to-speed ratio and a "steeper" draw angle than a level cue can. It's better if that's what you want, but of course it comes at the cost of harder aiming, more swerve, etc.

pj
chgo
 
As I promised in my previous threads dealing with draw shot physics, I finally got around to studying the effects of cue elevation. For people who like the math and physics, it can be found here:

For people who don't like the math and physics, here are the bottom-line conclusions:

  1. Elevating the cue reduces the amount of CB spin at OB contact, resulting in less draw distance (see TP B.8 for more info). The loss in spin is small for small cue elevations, but increases with more elevation (for a given cue speed and tip offset).
  2. Modest cue elevations (about 0-15 degrees) reduce the spin-to-speed ratio of the CB at OB contact, resulting in "slower" draw (see TP B.9 for more info).
  3. As you increase cue elevation above about 20 degrees, the spin-to-forward-speed ratio increases, allowing for "quicker" draw (see TP B.9 for more info). An extreme example is a highly elevated masse draw (pique) shot, where you create lots of backspin with very little forward speed.
Sometimes cue elevation is required to clear over an obstacle ball, or to prevent a double hit when there is a small gap between the CB and OB. And as noted above, with larger cue elevations, better "quick draw" action can result. However, for maximum draw distance, a level cue (or as close to level is possible) appears to be best.

The math and physics is fairly involved, but here's the basic concept:
With an elevated cue, the CB doesn't lose any speed or spin while it is airborne (between the bounces); however, more speed and spin is lost during the bounces (including the first bounce off the tip, based on HSV B.44) than with a near-level-cue drag shot.​

I look forward to any comments, suggestions, disagreements, or questions you might have.

Regards,
Dave

PS: FYI, the conclusions from all of my draw analyses can be found here:
Sorry I've taken so long to reply. I was on a week-long bicycle ride called the Ride The Rockies this past week. It looks like PJ, Colin, and others have answered most of the questions that have come up, but I'll put in my two-cents worth also.

Dr Dave, have you considered squirt in the vertical plane?
The small amount of squirt just changes the effective cue elevation slightly. For a draw shot, squirt reduces the effective cue elevation slightly (but not near enough to reduce it to or below level for a typical shot with the cue clearing the rails and the bridge hand clearing the table and rails).


When I was a beginning player, I heard and read to keep the cue as level as possible.
That is good advice.

So I figured that setting up a shot where the cue would clear the rails (I'm talkin' a really level cue here!) would yield the maximum amount of draw. This mostly resulted in scooping up the cue ball and miscues.
If you are scooping the ball, you are hitting the CB too low, probably due to a stroke issue (e.g., tightening the grip or raising the elbow during the stroke). For help, advice, and demonstrations of good technique, see the draw-shot technique-advice resource page.

I contend that some elevation is required so that the initial velocity of the cue ball is absolutely horizontal (Vy0 = 0). Less elevation for an LD shaft, a bit more elevation for regular shafts. Past this point, we actually perform a jump shot, with Vy0 < 0.
Not true. For most draw shots with a "near level" cue, the cue is elevated at an angle much large than a typical range of squirt values.

As a corollary, I submit that your demonstration of a follow-shot jumping over dimes is caused by a similar vertical squirt phenomenon, only, in the downward direction.
CB hop on follow shots (as with draw shots) is caused by cue elevation. And you are right that with follow shots, squirt adds slightly to the effective cue elevation. For more info and demonstrations, see the follow-shot ball-hop resource page.


I know the thread is 6-years old, but I'm right on topic... I think ;-)
FYI, I have much newer and better stuff on my website dealing with this topic. A lot of the stuff was added well after this thread came out. Here are some pertinent links:

draw shot cue elevation effects
draw shot physics-based advice
quick draw resource page

Also, here's a series of well-illustrated articles I wrote for BD in 2009:
"Draw Shot Physics - Part I: basics" (BD, April, 2009).
"Draw Shot Physics - Part II: examples" (BD, May, 2009).
"Draw Shot Physics - Part III: spin ratio" (BD, June, 2009).
"Draw Shot Physics - Part IV: cue elevation effects" (BD, July, 2009).

Enjoy,
Dave
 
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Let's face it, the cue butt is elevated on all draw shots in relation to the tip. I supposed what we are discussing is how much the cue is angled in relation to the table surface.

I have changed my draw stroke in the last few years. I used to draw by dropping the tip as low as possible in the final stroke. That does provide a lot of draw but also occasional miscues. Now what I do is avoid dipping the tip too low. I set the tip higher than bottom and try to stroke right through that spot keeping the cue level to it's angled plane. That technique has eliminated most miscues and also gives better distance control.
 
Its hard to explain why, but if I am up close to an object ball(2-3 balls distance) I feel I can draw more accurately if I am jacked up a bit.
When the OB is close, the risk of a double hit might be limiting your stroke acceleration with a level cue. Cue elevation definitely helps you avoid a double hit, allowing you to stroke with more speed.

Regards,
Dave
 
They came up playing on slow cloth, where you couldnt easily keep backspin on the ball over a distance. Jacking up slightly, jumps the ball off the surface a bit reducing some of the loss of spin due to the friction of the cloth. It used to be referred to as "skipping" the ball across the cloth where I grew up.
Onto Simonis, its not needed as often, but is still a useful shot depending on your ability and the distance between the balls. Jacking up makes the shot harder in several ways, and that is why its usually discouraged, especially for newer players.
Even on slow, sticky cloth, elevating the cue offers no advantage with a straight draw shot. The amount of spin lost on the CB bounces (including the first bounce off the tip) is larger than the spin saved by being airborne. This is clear both in practice and it is proved by the physics analysis. For more info, see draw-shot physics-based advice.

Regards,
Dave
 
Dr. Dave,

I would fall into a category of people that would prefer to "SLIGHTLY" raise the butt of the cue when executing a power draw shot. I think bridge height is related to this. For me, where I form a very solid bridge that will give me confidence to stroke through the bottom of the cue ball without a miscue--this bridge is slightly elevated...the elevated bridge forces a slightly elevated butt, so the tip can contact the bottom of the cue ball.
Excellent point. This could be a factor for some people, especially with shorter bridge lengths.

This also helps in freeing the butt of the cue from the chance of an impact with the table as I follow through, so I think the very slightly elevated bridge and butt help me perform a smooth powerful stroke that accelerates through the bottom of the cue ball.
Another good point. For people who drop their elbow during or after the hit on the CB, the extra elevation could help avoid a collision of the grip hand with a rail or the table surface.

Regards,
Dave
 
I suspect the main reason some players get more draw when jacking up is that they struggle to hit the CB low enough with their standard bridge and the jacking up tends to allow them to hit closer to the miscue limit, without the feel that they are going to miscue.
I agree. Here's an illustration from "Draw Shot Physics - Part IV: cue elevation effects" (BD, July, 2009) that illustrates this effect:

tip_offset.jpg

Regards,
Dave
 
I saw an old video once ,maybe 20 years, ago by an instructor named Don Feeney. In that video he demonstrated (how in his determination) that a slightly elevated cue really helped reduce collision induced throw. Even with various side CB hits, but especially when hitting straight low with that old 'drag stroke' and letting the CB roll pure.
I'm not so sure about ALL of that, but I do know that it is helpful to me on those long cuts where the guy has you wedged up in a corner pocket and you can't stroke clean.
What is your opinion of his analysis?
TY.
Honestly, I don't think it is good advice to add cue elevation (even a slight amount) to attempt to reduce cut-induced throw (CIT). As others have pointed out, adding cue elevation can make aiming and visual alignment more difficult and if the CB isn't struck perfectly on the vertical centerline, the added unintentional swerve will hurt accuracy and consistency.

Now it is true that added cue elevation will make the CB hop higher and longer, which could cause the CB to hit the OB while airborne. This will cause a slight over cut (see the jump shot over-cut resource page for more info) which will create the illusion that there is less CIT, but this effect is difficult to control and predict at various shot distances and speeds (especially under different conditions).

Now with a draw shot, there will be less CIT than with a stun shot (see the draw and follow throw effects resource page), so if the elevation causes a person to put more backspin on the CB, that could also reduce CIT, especially if more speed is used (which also reduces CIT in many cases, per the throw effects resource page).

Regards,
Dave
 
I do believe that you can draw the cue ball back straighter if there is a cut angle to the shot, using an elevated cue. Is that better draw? :D
[/B]JoeyA
No question about this effect. If there is a cut angle, and you need to draw the CB back at a tighter angle, cue elevation most certainly helps. For more info and demonstrations, see the quick draw resource page.

Regards,
Dave
 
Seems to me this would result in less draw because the CB's forward momentum isn't fully transferred to the OB (a "vertical cut shot").


Yes, elevating the cue produces a higher spin-to-speed ratio and a "steeper" draw angle than a level cue can. It's better if that's what you want, but of course it comes at the cost of harder aiming, more swerve, etc.

pj
chgo

I guess I didn't specify in the first example, I meant to say on a straight in shot (not a cut shot), where you are attempting to apply draw, I think that if the cue ball hits above the horizontal axis of the object ball, that might make it seem easier to draw the cue ball. I won't be practicing this method of draw but if you have more thoughts on this, I would like to hear them.

JoeyA
 
Let's face it, the cue butt is elevated on all draw shots in relation to the tip. I supposed what we are discussing is how much the cue is angled in relation to the table surface.
Maybe I misunderstand you, but I don't think there's a difference.

pj
chgo
 
Seems to me [CB hitting OB while airborne] would result in less draw because the CB's forward momentum isn't fully transferred to the OB (a "vertical cut shot").

pj
chgo
...I meant to say on a straight in shot (not a cut shot), where you are attempting to apply draw, I think that if the cue ball hits above the horizontal axis of the object ball, that might make it seem easier to draw the cue ball.

JoeyA
That's what I meant too - I meant "vertical cut shot" like we sometimes say "vertical squirt": a straight shot hit above center. Just like a normal (horizontal) cut shot, the CB would retain some forward momentum (caroming upward and forward rather than sideways and forward), making it harder, not easier, to draw.

Seems to me the only way it could make draw easier is if the CB landed on the OB at a much more vertical angle, caroming backwards rather than forward.

pj
chgo
 
That's what I meant too - I meant "vertical cut shot" like we sometimes say "vertical squirt": a straight shot hit above center. Just like a normal (horizontal) cut shot, the CB would retain some forward momentum (caroming upward and forward rather than sideways and forward), making it harder, not easier, to draw.

Seems to me the only way it could make draw easier is if the CB landed on the OB at a much more vertical angle, caroming backwards rather than forward.

pj
chgo
Agreed. The only case I can think of where attempting to hit the OB above the equator can yield better draw is a jump shot where you hit the OB on the fly. If you can do this reliably, jump draw is a "piece of cake."

Regards,
Dave
 
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:p:D:D
That's what I meant too - I meant "vertical cut shot" like we sometimes say "vertical squirt": a straight shot hit above center. Just like a normal (horizontal) cut shot, the CB would retain some forward momentum (caroming upward and forward rather than sideways and forward), making it harder, not easier, to draw.

Seems to me the only way it could make draw easier is if the CB landed on the OB at a much more vertical angle, caroming backwards rather than forward.

pj
chgo

Agreed. The only case I can think of where attempting to hit the OB above the equator for better draw is a jump shot where you hit the OB on the fly to make jump draw easy.

Regards,
Dave

Ok, that's it. :grin::p:grin::grin:
JoeyA
 
That's what I meant too - I meant "vertical cut shot" like we sometimes say "vertical squirt": a straight shot hit above center. Just like a normal (horizontal) cut shot, the CB would retain some forward momentum (caroming upward and forward rather than sideways and forward), making it harder, not easier, to draw.
FYI to those interested, good examples of this effect can be found in the 2nd half of the following video:

HSV B.6 - Double hit detection and avoidance

And the following video shows how things change with cue elevation and shot distance:

NV F.3 - Pool stun/draw/follow jump shots at various cue elevations, with smartphone slo-mo

Enjoy,
Dave
 
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