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Panhdlce
04-29-2008, 01:51 PM
Sometimes when I hit a draw shot the cueball stops dead then reverses direcrion, other times the instant it strikes the object ball it draws?

Andrew Manning
04-29-2008, 02:00 PM
Sometimes when I hit a draw shot the cueball stops dead then reverses direcrion, other times the instant it strikes the object ball it draws?

The delay before the CB comes back depends on the speed of the cloth. On faster cloth, the spin will bring the CB back more gradually, due to the spin being converted (by friction) to translational speed more slowly (because there's less friction). On a slower cloth, the CB's spin will very quickly become translational speed due to the high friction, and will seem to come back with less delay.

It's worth noting that the CB starts coming backwards immediately in both cases, it just picks up speed more quickly in the one case than the other.

The other relevant factor is CB bounce. If you elevate, and the CB is actually slightly above the cloth when it hits the OB, then it will bounce upward and slightly forward after contact. In that case, the CB is actually still moving forward, and so there is a real delay before the spins starts moving it backward. This delay will be longer or shorter depending on cloth speed.

-Andrew

BRKNRUN
04-29-2008, 02:10 PM
Weight of the CB will play some part.
Forward momentum vs draw spin applied will play some part.
Angle will play some part.
How clean or dirty the balls are will play some part.
Newness of cloth will play some part.
Weather will play some part. (Wet or Dry table)


I guessing in most cases it can vary from shot to shot on the same table on the same day based on the second and third variables.

The other variables should all remain farily static throuought a session...(but they can change also)

av84fun
04-29-2008, 02:15 PM
The delay before the CB comes back depends on the speed of the cloth. On faster cloth, the spin will bring the CB back more gradually, due to the spin being converted (by friction) to translational speed more slowly (because there's less friction). On a slower cloth, the CB's spin will very quickly become translational speed due to the high friction, and will seem to come back with less delay.

It's worth noting that the CB starts coming backwards immediately in both cases, it just picks up speed more quickly in the one case than the other.

The other relevant factor is CB bounce. If you elevate, and the CB is actually slightly above the cloth when it hits the OB, then it will bounce upward and slightly forward after contact. In that case, the CB is actually still moving forward, and so there is a real delay before the spins starts moving it backward. This delay will be longer or shorter depending on cloth speed.

-Andrew


Andrew, I'm sticking my neck out here but I am almost certain that I have seen slow mo video showing that the cb can skid forward after impact...I think due to the power of forward momentum briefly overcoming the reverse spin.

I'm sure Bob or Dr_Dave will be able to confirm or deny that.

Regards,
Jim

WesleyW
04-29-2008, 02:22 PM
Sometimes when I hit a draw shot the cueball stops dead then reverses direcrionother times the instant it strikes the object ball it draws?

You did not hit a draw shot, you hit center.

av84fun
04-29-2008, 03:15 PM
You did not hit a draw shot, you hit center.

Other than a break shot where the cb hits a mass 9x its own weight, how does a cb reverse direction when struck with center ball??

If it is skidding at OB contact, it will stop dead and stay there...and if the cb has finished skidding and begins its forward roll, I don't think it will either stop dead (except momentarily) or reverse direction.

If hit with true center, I don't think there is any reverse spin.

What am I missing?

Thanks,

Jim

Drawman623
04-29-2008, 03:22 PM
I've seen a few pros use this to their advantage. Rempe in particular can make his cue ball pull back instantly or skid forward to influence the position.

One member mentioned cue ball weight. I think that is a big factor here. Go to a bar table where the cue is different than the object balls and your draw will not take in the same way. I've seen guys playing with miesel cue balls from Aramith that they brought into the poolroom. That is fine but if they don't match the house set of object balls, the player will need to adjust.

Hats off to Diamond for offering us the optical ball reader. Now their pay tables have uniform balls with a cue that has exact size and weight of the object balls yet the system is still smart enough to send the cue ball to the other end. Those guys at Diamond have brought equipment to a new level.

sydbarret
04-29-2008, 03:24 PM
stay down and follow thruuuuu.

dr_dave
04-29-2008, 03:26 PM
Andrew, I'm sticking my neck out here but I am almost certain that I have seen slow mo video showing that the cb can skid forward after impact...I think due to the power of forward momentum briefly overcoming the reverse spin.

I'm sure Bob or Dr_Dave will be able to confirm or deny that.Here's a good super-slow-motion example:
http://billiards.colostate.edu/high_speed_videos/HSV4-1.htm
Here, the CB is slightly heavier than the OB ... that's why it moves forward slightly after impact, before drawing back.

Regards,
Dave

av84fun
04-29-2008, 03:40 PM
Here's a good super-slow-motion example:
http://billiards.colostate.edu/high_speed_videos/HSV4-1.htm
Here, the CB is slightly heavier than the OB ... that's why it moves forward slightly after impact, before drawing back.

Regards,
Dave

Thanks! I've seen other such examples as well. While in this video, the cb is slightly heavier than the OB, I would GUESS that momentum (mv) is a factor as well.

Even if cb/ob are of identical weight, if the cb strikes the ob at 50mph (assuming for sake of argument that the balls could withstand that impact without shattering) then I would guess that the CB is going to move forward...even if it was spinning in reverse at a substantial rpm value.

Ya think???

(-:

Jim

dr_dave
04-29-2008, 04:10 PM
Even if cb/ob are of identical weight, if the cb strikes the ob at 50mph (assuming for sake of argument that the balls could withstand that impact without shattering) then I would guess that the CB is going to move forward...even if it was spinning in reverse at a substantial rpm value.Regardless of the speed, if the CB and OB are the same weight and the CB hits the OB squarely, the CB will theoretically deliver all of its momentum to the OB, and the CB will momentarily stop in place before drawing back due to the bottom spin. I wrote "theoretically," because this assumes the balls are perfectly elastic (i.e., no energy loss during impact). In actuality, the CB does retain a very small portion of its forward speed in a non perfect collision (per the math and physics in TP A.5 (http://billiards.colostate.edu/technical_proofs/new/TP_A-5.pdf)).

Now, at 50 mph, it would be very likely the CB would be slightly airborne when it hits the OB (due to hop caused by cue elevation). In that case, it will advance forward some because it is not hitting the OB squarely. For an exaggerated example, see the last shot in HSV B.6 (http://billiards.colostate.edu/high_speed_videos/new/HSVB-6.htm)

Regards,
Dave

av84fun
04-29-2008, 04:15 PM
Regardless of the speed, if the CB and OB are the same weight and the CB hits the OB squarely, the CB will theoretically deliver all of its momentum to the OB, and the CB will momentarily stop in place before drawing back due to the bottom spin. I wrote "theoretically," because this assumes the balls are perfectly elastic (i.e., no energy loss during impact). In actuality, the CB does retain a very small portion of its forward speed in a non perfect collision (per the math and physics in TP A.5 (http://billiards.colostate.edu/technical_proofs/new/TP_A-5.pdf)).

Now, at 50 mph, it would be very likely the CB would be slightly airborne when it hits the OB (due to hop caused by cue elevation). In that case, it will advance forward some because it is not hitting the OB squarely. For an exaggerated example, see the last shot in HSV B.6 (http://billiards.colostate.edu/high_speed_videos/new/HSVB-6.htm)

Regards,
Dave

THANKS! Your posts never fail to teach. Whether I learn anything is another matter altogether!!!

(-:

Jim

dr_dave
04-29-2008, 04:18 PM
THANKS! Your posts never fail to teach. Whether I learn anything is another matter altogether!!!

(-:

JimYou're very welcome.

I aim to swerve. :cool:

Dave

pooltchr
04-29-2008, 05:22 PM
I aim to swerve. :cool:

Dave
Learning to use squirt to your advantage, huh?? ;)
Steve

dr_dave
04-29-2008, 06:20 PM
Learning to use squirt to your advantage, huh?? ;)
SteveYou bet. I don't like to throw games.

Are you watching the IPT match? It's on right now. I'm watching it as I type this message.

Regards,
Dave

WesleyW
04-30-2008, 02:56 AM
Other than a break shot where the cb hits a mass 9x its own weight, how does a cb reverse direction when struck with center ball??

If it is skidding at OB contact, it will stop dead and stay there...and if the cb has finished skidding and begins its forward roll, I don't think it will either stop dead (except momentarily) or reverse direction.

If hit with true center, I don't think there is any reverse spin.

What am I missing?

Thanks,

Jim

Topic starter didn't mention that the CB got reverse spin. He just said he apply a draw shot, but the CB didn't draw. He might think that he did a draw shot, but he didn't. If the CB really draw after the stroke, than he didn't apply enought draw spin on the CB. Before the CB hit the OB, the CB stops spinning (draw) and start to follow. Because it's not a stun ball, it will move a little more forward, because of the running spin.

mikepage
04-30-2008, 05:40 AM
The delay before the CB comes back depends on the speed of the cloth. On faster cloth, the spin will bring the CB back more gradually, due to the spin being converted (by friction) to translational speed more slowly (because there's less friction). On a slower cloth, the CB's spin will very quickly become translational speed due to the high friction, and will seem to come back with less delay.

It's worth noting that the CB starts coming backwards immediately in both cases, it just picks up speed more quickly in the one case than the other.

[...] This delay will be longer or shorter depending on cloth speed.

-Andrew

The ball-cloth sliding friction you're taking about is actually a separate property from the speed of the cloth.

New Simonis, for example, is like ice-- both fast and slick. It will have a longer delay for a straight-on draw shot and a longer sideways arc for an almost straight on draw shot.

Old Simonis that's stretched tightly can be just as fast, but it's not so slick. Imagine a steel surface painted with skid-resistant paint. It might be very fast (low rolling resistance) but it's also sticky (high sliding resistance).

Patrick Johnson
04-30-2008, 06:10 AM
Correct way to stroke a draw shot?
Sometimes when I hit a draw shot the cueball stops dead then reverses direcrion, other times the instant it strikes the object ball it draws?

As others have told you, this is a result of the stickiness of the cloth or the weight of the cue ball. To answer your first question, it has nothing to do with your stroke.

pj
chgo

Andrew Manning
04-30-2008, 06:16 AM
Andrew, I'm sticking my neck out here but I am almost certain that I have seen slow mo video showing that the cb can skid forward after impact...I think due to the power of forward momentum briefly overcoming the reverse spin.

I'm sure Bob or Dr_Dave will be able to confirm or deny that.

Regards,
Jim

I'd answer this, but Dr. Dave already said it. If the CB is slightly heavier, larger, or airborne it will go forward. If the CB is the same weight as the OB and hits dead center (meaning it can't be airborne or a different size), then it will stop dead, at which point whatever spin is on the ball will immediately begin to accelerate it back for draw or forward for follow.

-Andrew

Andrew Manning
04-30-2008, 06:17 AM
The ball-cloth sliding friction you're taking about is actually a separate property from the speed of the cloth.

New Simonis, for example, is like ice-- both fast and slick. It will have a longer delay for a straight-on draw shot and a longer sideways arc for an almost straight on draw shot.

Old Simonis that's stretched tightly can be just as fast, but it's not so slick. Imagine a steel surface painted with skid-resistant paint. It might be very fast (low rolling resistance) but it's also sticky (high sliding resistance).

True, "speed" is a bit of an ambiguous term when it comes to billiards cloth; what I meant was "slickness".

-Andrew

Jal
04-30-2008, 11:19 AM
.... If the CB is the same weight as the OB and hits dead center (meaning it can't be airborne or a different size), then it will stop dead, at which point whatever spin is on the ball will immediately begin to accelerate it back for draw or forward for follow.Not so. In his first paragraph, he explained why it will continue to move forward (slightly) even under the conditions you describe. It's due to the less than perfect elasticity of the collision.

Another reason for seeing various responses is the amount of vertical "throw" that occurs. On a draw shot, the cueball gets pushed downward onto the cloth at different speeds depending on the amount of throw (and cueball speed), which in turn depends on several factors. If a freshly laid chalkmark (or an old one) happens to be at the contact area between the balls, then the cueball really gets "slammed" onto the surface. This will cause it to begin its reverse motion considerably quicker because of the larger friction force between the ball and the cloth. However, the draw distance will not be as great as it would be if this didn't occur.

Jim