Lag practice

seanandnik

AzB Silver Member
Silver Member
I always say I’m going to practice my lagging but I never do. Any tips,techniques, advice on lagging on a carom table ?
 

hang-the-9

AzB Silver Member
Silver Member
I always say I’m going to practice my lagging but I never do. Any tips,techniques, advice on lagging on a carom table ?

Ah, aside from going and practicing? Nope, just do it.

There is a quote I like to use from Better Off Dead. OK, so any advice on how to do this ski run? Yes, go really fast downhill. If something gets in your way, turn.

Same thing with half of "tips on how to make shots" advice, go shoot the shot a few 100 times on various equipment, no magic sauce.

My son does have a thing he does, he hits the lag with follow. But he also goes on the match table before it starts and spend as much time on it as he can learning the speed and how the rails play. At the USAPL/BCA nationals in Vegas this year he was on the tables 10-20 minutes before the opponent practicing, I don't think he lost a single lag and he made at least one ball on most breaks, must have run out 2-3 games from the break each set. Just do it.

From your equipment, you don't seem like a noob at the game, just shoot the shot and see how you need to shoot it. It's all speed control and you can't learn that with advice unless you want to hear "hit it softer" or "hit it harder" which I'm sure you can figure out on your own LOL
 
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o.g. (old guy)

mark
Silver Member
A lag shot is different than just about all other shots, except maybe a push out. No object ball no pocket, just a rail to aim at. One little trick I use is to shoot the shot like I was thin cutting a ball on the foot rail and trying to get position to the head rail.
 

pab

Center ball can do it all
Silver Member
For practice, focus on being consistent in your cueing. Sounds obvious, but pick a spot on the vertical axis of the CB and try to hit that spot every time you lag. I believe a little above center is a pretty decent place to start. You want the CB starting off with roll - that will help with consistency as you play on different tables. For a match, you definitely want to hit a few lags before the official lag so you can get a feel for how the cushions play.

One more thing: I sometimes practice the lag for 1/2 hour or more. I couple that with another drill that Dr. Dave calls MOFUDAT - sending the CB up and down the center line of the table. Kind of kills two birds with one stone - you practice the lag speed and hitting dead center on the CB.

Hope that helps.
 

pt109

WO double hemlock
Gold Member
Silver Member
Do not hit the ball below center on the lag....
...sometimes a little back spin grabs.

I like quarter tip above center.
 

bbb

AzB Gold Member
Gold Member
Silver Member
shorten your bridge length
learn what bridge length and speed gives you a perfect lag
 

Bob Jewett

AZB Osmium Member
Staff member
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Do not hit the ball below center on the lag....
...sometimes a little back spin grabs.

I like quarter tip above center.
There's actually an optimum height to hit the ball. It depends a little on the weight of the cue stick and tip, but it is around 60% of the height of the cue ball. That's 6mm or half a tip above center. Your cue stick will have to be raised a little higher than that because you will be hitting with the bottom half of the cue tip. That height is insensitive to small errors in height.

About the worst place to hit the ball is for lots of draw. A little lower and you not only start the cue ball off slower but it will slow down more due to more backspin.

At 60% nominal, a little higher will give a little more top spin to help the ball go forward to make up for the more off-center hit which starts the ball at a lower speed, so there is net little change in how far the cue ball will go. Then all you have to control is your stick speed.
 

Patrick Johnson

Fish of the Day
Silver Member
There's actually an optimum height to hit the ball. It depends a little on the weight of the cue stick and tip, but it is around 60% of the height of the cue ball.
I've always heard that "instant natural roll" is produced by hitting about 70% of the height of the CB (2/5 of the distance from center to edge). Can you expand a little on why 60% is better for lagging?

Thanks,

pj
chgo
 

Bob Jewett

AZB Osmium Member
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I've always heard that "instant natural roll" is produced by hitting about 70% of the height of the CB (2/5 of the distance from center to edge). Can you expand a little on why 60% is better for lagging?

Thanks,

pj
chgo
While hitting at 70% does get the ball rolling smoothly immediately, hitting the ball that far from center gets less immediate forward motion into the ball. If you hit lower (at the same stick speed) the immediate forward motion is faster and then the ball slows a little as the speed is turned into roll. There is a balance between starting the ball with some spin and starting it with more speed.

This problem was first explained in detail by Coriolis in 1835 in his book on billiard physics. Here is the (very clever) diagram that goes with his discussion of the final speed of the cue ball when struck with follow or draw. The solid curve that bulges out to the right shows the final smoothly rolling speed of the cue ball when it is struck at various heights which are suggested by the incoming arrows. As you can see, hitting at the "instant rolling" point D will result in close to the same final speed as hitting the ball in the middle M''.
Coriolis 001.jpg
This best height to play a lag problem was also explained in Ron Shepard's paper about billiard physics (around page 32) which is available here: http://www.sfbilliards.com/Misc/Shepard_apapp.pdf Shepard's paper is very readable for non-scientists who have a little technical background.

Coriolis' book has been translated into English by David Nadler and that is available from the site http://www.coriolisbilliards.com/ In his description of the book Nadler shows an example page to scare you off from buying the book in case you are allergic to equations. Actually, while it has lots of equations Coriolis is careful to explain the results in fairly non-technical wording. For those who can read a little French, a reprint of the original is also available for about $60. The French used has a very restricted technical vocabulary, so it is fairly easy to read as French writing goes.

Here's the cover of Nadler's translation:

cover.gif
 

Poolmanis

AzB Silver Member
Silver Member
"You must spread some Reputation around before giving it to Bob Jewett again."

I really like you posting more nowadays Bob.
Always polite and knowledgeable.
 

Patrick Johnson

Fish of the Day
Silver Member
While hitting at 70% does get the ball rolling smoothly immediately, hitting the ball that far from center gets less immediate forward motion into the ball. If you hit lower (at the same stick speed) the immediate forward motion is faster and then the ball slows a little as the speed is turned into roll. There is a balance between starting the ball with some spin and starting it with more speed.in close to the same final speed as hitting the ball in the middle M''.
So the benefit is getting the same CB speed with less cue speed?

I assume there's some consideration given to the effect sliding might have on accuracy?

pj
chgo
 

Bob Jewett

AZB Osmium Member
Staff member
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So the benefit is getting the same CB speed with less cue speed?

I assume there's some consideration given to the effect sliding might have on accuracy?

pj
chgo
The benefit is similar to a half-ball angle shot: small errors in height (fullness) have negligible effect on the distance traveled (exit angle). It turns out that for the lag shot, it is also the most efficient (least effort) place to hit the cue ball. I can't think of a parallel advantage for the half-ball (30-degree rule) shot.

This kind of situation -- where the process (shot) is insensitive to a major input parameter (height of hit) -- is pretty common. Perhaps the most common at billiards is where the correct selection of bridge length can make the path of the cue ball insensitive to left-right errors in cueing. (pivot-point, backhand english, squirt compensation)

I'm not sure what you mean by the sliding comment.
 

dr_dave

Instructional Author
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Silver Member
The benefit is similar to a half-ball angle shot: small errors in height (fullness) have negligible effect on the distance traveled (exit angle). It turns out that for the lag shot, it is also the most efficient (least effort) place to hit the cue ball.
Pat and others, if you want to see the math and physics (that also accounts for real-life conditions), see:

TP B.12 - Optimal tip height for speed/distance control

And for less mathy explanations and illustrations, see:

"The Lag Shot" (BD, October, 2011)

And for more lag shot advice, see the lag shot resource page.

Regards,
Dave
 

dr_dave

Instructional Author
Gold Member
Silver Member
So the benefit is getting the same CB speed with less cue speed?
See Diagram 2 and the surrounding discussion here:

"The Lag Shot" (BD, October, 2011)

I assume there's some consideration given to the effect sliding might have on accuracy?
Shepard's analysis neglected cue tip inefficiency and drag distance, but the results aren't much different when all non-ideal effects are considered, as shown in:

TP B.12 - Optimal tip height for speed/distance control

Catch you later,
Dave
 

Patrick Johnson

Fish of the Day
Silver Member
The benefit is similar to a half-ball angle shot: small errors in height (fullness) have negligible effect on the distance traveled (exit angle). It turns out that for the lag shot, it is also the most efficient (least effort) place to hit the cue ball. I can't think of a parallel advantage for the half-ball (30-degree rule) shot.

This kind of situation -- where the process (shot) is insensitive to a major input parameter (height of hit) -- is pretty common. Perhaps the most common at billiards is where the correct selection of bridge length can make the path of the cue ball insensitive to left-right errors in cueing. (pivot-point, backhand english, squirt compensation)

I'm not sure what you mean by the sliding comment.
Thanks, very interesting.

About sliding: I'm thinking a slightly off center hit would be more likely to masse offline with a sliding ball than a rolling one (and the 60% hit slides it a little way)...?

pj
chgo
 
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