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Bambu
12-27-2007, 07:55 PM
Recently I was lucky enough to get a speedy email reply from Dr. Dave about object ball curve. He directed me to this forum, where I am eager to hear his answers regarding the path of an object ball.
My question: Dear Dr. Dave, I have read your book, and examined as many videos as I can, but would like your opinion on the path of an object ball. It is my contention that if you can transfer enough left or right english to an object ball, it can be made to curve,just a hair.
Dr. Dave's reply: Draw and follow on the cue ball can create a very small amount of object ball swerve, but the amount is so small, I don't think it could even be noticeable.
See the last page of TP A.24 for example numbers and summary statements:
http://billiards.colostate.edu/technical_proofs/new/TP_A-24.pdf
For all pratical purposes, the object ball takes a straight path in the thrown direction.

My reply to Dr. Dave: Thanks so much Dr. Dave. That answer and reference is helpful, but I still have more questions. I really do appreciate your valuable time on this. I did refer to the site you suggested, and was pleased to find what I think I was looking for. Sadly, I dont understand the math involved, but I did find this statement, followed by a physics formula: "This induced spin curves the trajectory of the OB slightly with a masse type action."
My questions are as follows: I understood your initial reply, which was "For all pratical purposes, the object ball takes a straight path in the thrown direction."
I understand object ball paths are straight for practical purposes, but if there is enough spin transferred, can you tell me if this formula I am referring to, represents the impractical? That is to say, a very minor object ball curve which usually cannot be seen?
As the paper you were kind enough to refer me to was more about follow and draw, I am also interested in what left and right spin transfer can do to an object balls path. I understand that my question is about splitting hairs, that I am fussing about an extremely minor effect, but sometimes I find it helpful to use spin transfer to sink balls. Would you agree that a tiny amount of curve can also result from an extreme left or right spin transfer, or throw shot? I have been experimenting furiously with these shots, and want to be sure I havent lost my mind when I say I can curve an object ball....no matter how small a curve it may be. Thanks again Dr. Dave!

Bob_Jewett
12-27-2007, 08:25 PM
<blockquote><font class="small">Quote Bambu:</font><hr> ... I have been experimenting furiously with these shots, and want to be sure I haven't lost my mind when I say I can curve an object ball....no matter how small a curve it may be. Thanks again Dr. Dave! <hr /></blockquote>
Here is a related article from a while ago:

http://www.sfbilliards.com/articles/1992-06.pdf

If you can figure out how to make the combination illustrated (3-9), and are willing to show me how to do it, I'll give you $200. More generally, the setup shown will show you how much curve you are really getting on the object ball. I suspect you are getting less than a quarter-inch in the length of the table.

If the object ball can be made to curve over a thousandth of an inch in the length of the table, is that useful? How about a quarter of an inch? If the best you can do is only a quarter of an inch with a lot of side spin on the cue ball, you would be better off playing for the jump shot due to the difficulty of aiming so precisely with a lot of spin.

av84fun
12-27-2007, 09:53 PM
I agree that of all the variables that can make or break a shot...ob curve is not worth spending any time on.

Regards,
jim

Bambu
12-27-2007, 11:10 PM
Thanks Bob. I agree, that shot is not makeable. I have seen this shot and tried it. If I do manage to transfer enough right spin to the 3 ball, it will be thrown into the 4. This shot almost calls for masse-ing around the 4 ball. Even if you do somehow manage to get the 3 ball to break toward the 9 slightly, at just the right time....the 3 ball wont have enough energy left to make the 9.
But if you were allow me to re-position the 3 and cueball, I would move the 3 ball up, right behind the 4...only about a balls distance between the 3 and 4. With only a tiny edge of a blocking ball to get by, and by being very close to that ball, I am now in a better position to be able to realistically curve my object ball. Now instead of hitting the blocking edge, I can slide straight past it, before the minute curve takes effect.
I cant say I have made the 9 ball in this way on that particular shot, but I have another shot set up which demonstrates the same effect in terms of curving an object ball.
I am glad you brought up that thousandth or quarter of an inch, because this is the measurement I cannot come up with. And I certainly agree, the curve is tiny, and I would not attempt to win that game with any type of spin transfer shot. The thing is, every now and then, that quarter inch can get you out of a jam, just in other ways. I agree that this curve is so minor, it is almost negligible. I only wish to acknowledge its existence at times, and measure it...if thats at all possible. Thanks so much Bob. I do appreciate your time.

dr_dave
12-28-2007, 09:58 AM
<blockquote><font class="small">Quote Bambu:</font><hr>Recently I was lucky enough to get a speedy email reply from Dr. Dave about object ball curve. He directed me to this forum, where I am eager to hear his answers regarding the path of an object ball.<hr /></blockquote>Welcome to the CCB! I hope you find it useful. It looks like you got some good responses already.

<blockquote><font class="small">Quote Bambu:</font><hr>My question: Dear Dr. Dave, I have read your book, and examined as many videos as I can, but would like your opinion on the path of an object ball. It is my contention that if you can transfer enough left or right english to an object ball, it can be made to curve,just a hair.
Dr. Dave's reply: Draw and follow on the cue ball can create a very small amount of object ball swerve, but the amount is so small, I don't think it could even be noticeable.
See the last page of TP A.24 for example numbers and summary statements:
http://billiards.colostate.edu/technical_proofs/new/TP_A-24.pdf
For all pratical purposes, the object ball takes a straight path in the thrown direction.

My reply to Dr. Dave: Thanks so much Dr. Dave. That answer and reference is helpful, but I still have more questions. I really do appreciate your valuable time on this. I did refer to the site you suggested, and was pleased to find what I think I was looking for. Sadly, I dont understand the math involved, but I did find this statement, followed by a physics formula: "This induced spin curves the trajectory of the OB slightly with a masse type action."
My questions are as follows: I understood your initial reply, which was "For all pratical purposes, the object ball takes a straight path in the thrown direction."
I understand object ball paths are straight for practical purposes, but if there is enough spin transferred, can you tell me if this formula I am referring to, represents the impractical? That is to say, a very minor object ball curve which usually cannot be seen?<hr /></blockquote>That is correct. The amount of object ball curve predicted by the physics is too small to make a practical difference. The angle change reported (0.07 degrees) would result in about a 1/10 of an inch deflection over a full table length. To me, this is "practically" no effect at all.

<blockquote><font class="small">Quote Bambu:</font><hr>As the paper you were kind enough to refer me to was more about follow and draw, I am also interested in what left and right spin transfer can do to an object balls path. I understand that my question is about splitting hairs, that I am fussing about an extremely minor effect, but sometimes I find it helpful to use spin transfer to sink balls. Would you agree that a tiny amount of curve can also result from an extreme left or right spin transfer, or throw shot? I have been experimenting furiously with these shots, and want to be sure I havent lost my mind when I say I can curve an object ball....no matter how small a curve it may be. Thanks again Dr. Dave!<hr /></blockquote>Throw and spin-transfer can definitely be useful and effective. For more info, see my August '06 through July '07 articles (http://billiards.colostate.edu/bd_articles/index.html).

Concerning object ball swerve, the physics predicts that only follow and draw can create only a tiny amount OB swerve, and only if there is a cut angle. Sidespin creates throw and spin transfer, but absolutely no OB swerve. For a straight-on shot, an extremely tiny amount of OB swerve might be possible with a difficult masse shot, but this would never stand a chance of being effective (see Bob's article (http://www.sfbilliards.com/articles/1992-06.pdf) for more info).

Regards,
Dave

Bambu
12-28-2007, 02:04 PM
Thanks so much Dr. Dave. And thank you for welcoming me to the group. Your answer means so much to me. You have really made my day. It must be that what I think I am accomplishing with left or right spin, is truly the result of whatever draw or follow was also incorporated into the same shot. Very interesting. Thanks again and have a great new year, everyone!

dr_dave
12-28-2007, 02:43 PM
<blockquote><font class="small">Quote Bambu:</font><hr> Thanks so much Dr. Dave. And thank you for welcoming me to the group. Your answer means so much to me. You have really made my day. It must be that what I think I am accomplishing with left or right spin, is truly the result of whatever draw or follow was also incorporated into the same shot. Very interesting. Thanks again and have a great new year, everyone!<hr /></blockquote>You're very welcome.

Are you sure what you are seeing is OB swerve, and not just OB throw? Have you tried Bob's shot?

Regards,
Dave

Bambu
12-28-2007, 06:56 PM
Because it is so minor, its hard for me to call this effect swerve. I consider it throw when there is a cut involved, or spin transfer if the hit is full.
I did try Bob's shot, but I cannot control the point where the 3 ball breaks toward the 9. To get that to work, the 3 needs to go straight for a whole diamonds distance before getting thrown towards the 9. The best I could do was hit the 4. Masse-ing the 3 around the 4 alone would be tough enough! I really did not mean to challenge Bob or his shot, and I admire his work as I do yours.

Bob_Jewett
12-28-2007, 07:02 PM
<blockquote><font class="small">Quote Bambu:</font><hr> ... I did try Bob's shot, but I cannot control the point where the 3 ball breaks toward the 9. To get that to work, the 3 needs to go straight for a whole diamonds distance before getting thrown towards the 9. The best I could do was hit the 4. ... <hr /></blockquote>
I approached the shot very differently than you seem to be doing. I just shot the 3 as close as possible to the 4 without hitting it. If you do this, and the path of the 3 curves towards the 4 at all, you can hit at least a little of the 9. I think that if you draw out any curved path for the 3 on a skinny piece of paper and then rotate the paper so the path just misses the 4, it will be clear that you can hit the 9.

wolfdancer
12-28-2007, 07:19 PM
You play pool???????
I thought you was jes teaching physics here to an elite class... /ccboard/images/graemlins/grin.gif /ccboard/images/graemlins/grin.gif
Now I might have to go check out your site.
Hope that you have a "Happy New Year"...and that 2008 is both healthy and prosperous for you!!!
I'm starting my own pool school next year, and guarantee to make anyone a "B" player, at least....'course you have to be an "A" player, prior to enrollment.

dr_dave
12-28-2007, 08:48 PM
<blockquote><font class="small">Quote wolfdancer:</font><hr>Hope that you have a "Happy New Year"...and that 2008 is both healthy and prosperous for you!!!<hr /></blockquote>Same to you and everybody else!

<blockquote><font class="small">Quote wolfdancer:</font><hr>I'm starting my own pool school next year, and guarantee to make anyone a "B" player, at least....'course you have to be an "A" player, prior to enrollment.<hr /></blockquote>I bet you will be very successful. /ccboard/images/graemlins/tongue.gif Will you also offer snake oil for sale?

Catch you later,
Dave

Jal
12-29-2007, 01:01 PM
<blockquote><font class="small">Quote dr_dave:</font><hr>...
Concerning object ball swerve, the physics predicts that only follow and draw can create only a tiny amount OB swerve, and only if there is a cut angle. Sidespin creates throw and spin transfer, but absolutely no OB swerve. ...<hr /></blockquote>Dr. Dave,

I'll have to register a little bit of a dissenting vote, mainly because after these effects were pointed out by Mac (Cushioncrawler), I endured numerous headaches trying to put numbers on them. As you point out, for practical purposes, they are essentially nil, though Mac might disagree.

Curve produced by draw or follow should take place even on a straight shot if sidespin is also present; it's a function of friction direction. Pure sidespin should also cause a curve because of the cloth's rolling resistance. The net force acting normal to the surface of a rolling ball, on 100 speed cloth for instance, is inclined from the vertical by about 0.8 degrees. Assuming this holds for a sliding ball, which is likely true since it is caused mostly, if not completely, by the ball's weight and the response of the cloth fibers to it, a curve will result. A very small curve, to be sure.

For cut shots with draw or follow, Bob J. has described yet another effect: the component of spin normal to the surfaces will cause the balls to act like clutch plates. This reinforces the other draw/follow masse effect, but by how much is unknown (to me).

Jim

dr_dave
12-29-2007, 03:01 PM
<blockquote><font class="small">Quote Jal:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr>...Concerning object ball swerve, the physics predicts that only follow and draw can create only a tiny amount OB swerve, and only if there is a cut angle. Sidespin creates throw and spin transfer, but absolutely no OB swerve. ...<hr /></blockquote>Dr. Dave,

I'll have to register a little bit of a dissenting vote, mainly because after these effects were pointed out by Mac (Cushioncrawler), I endured numerous headaches trying to put numbers on them. As you point out, for practical purposes, they are essentially nil, though Mac might disagree.

Curve produced by draw or follow should take place even on a straight shot if sidespin is also present; it's a function of friction direction. Pure sidespin should also cause a curve because of the cloth's rolling resistance. The net force acting normal to the surface of a rolling ball, on 100 speed cloth for instance, is inclined from the vertical by about 0.8 degrees. Assuming this holds for a sliding ball, which is likely true since it is caused mostly, if not completely, by the ball's weight and the response of the cloth fibers to it, a curve will result. A very small curve, to be sure.

For cut shots with draw or follow, Bob J. has described yet another effect: the component of spin normal to the surfaces will cause the balls to act like clutch plates. This reinforces the other draw/follow masse effect, but by how much is unknown (to me).<hr /></blockquote>Jim,

Thank you for pointing this out. You are correct ... in my analysis, I have assumed the nappy-cloth-turn-effect is negligible. I would guess this effect is even smaller than the object-ball-swerve effect on typical pool-table cloth. Have you run numbers or done tests to see if the turn effect is realistically observable or not on a pool table?

Regards,
Dave

dr_dave
12-30-2007, 11:16 AM
<blockquote><font class="small">Quote Bob_Jewett:</font><hr> <blockquote><font class="small">Quote Bambu:</font><hr> ... I have been experimenting furiously with these shots, and want to be sure I haven't lost my mind when I say I can curve an object ball....no matter how small a curve it may be. Thanks again Dr. Dave! <hr /></blockquote>
Here is a related article from a while ago:

http://www.sfbilliards.com/articles/1992-06.pdf<hr /></blockquote>Bob,

Did you ever do a follow-up article on this? I didn't see it on your website.

Also, do you think obect ball swerve and/or nap turn can ever be important factors with typical pool table conditons, even with ball cling (e.g., with chalk on the contact point between the balls)?

Thanks,
Dave

Bob_Jewett
12-30-2007, 11:58 AM
<blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote Bob_Jewett:</font><hr> ...
Here is a related article from a while ago:
http://www.sfbilliards.com/articles/1992-06.pdf ... <hr /></blockquote>
Bob,

Did you ever do a follow-up article on this? I didn't see it on your website.

Also, do you think obect ball swerve and/or nap turn can ever be important factors with typical pool table conditons, even with ball cling (e.g., with chalk on the contact point between the balls)?

Thanks,
Dave <hr /></blockquote>
I did do a follow up in which I made a $100 offer for how to do the shot (make the object ball curve significantly). I have since raised that to $200. There have been no takers. One top player says on an instructional tape that it is possible to make the object ball curve. I happened to see him in an exhibition and set up the shot in the article. I asked him to curve the ball and hit the far ball. He saw immediately that he couldn't and didn't even try. On the tape, I suspect he made the "blocked" ball by cheating the pocket. Of course on a video tape it's impossible to see whether a ball is blocked or not except with very precise camera work, and the "handi-cam on a tripod" production of that particular tape was not up to the task.

I think that if skid occurs for the right shot, the object ball might visibly curve. I have never seen convincing nap turn even though I've played on napped cloths. I've seen diagrams of balls goingmoving

Jal
12-30-2007, 02:49 PM
<blockquote><font class="small">Quote dr_dave:</font><hr>...I have assumed the nappy-cloth-turn-effect is negligible. I would guess this effect is even smaller than the object-ball-swerve effect on typical pool-table cloth. Have you run numbers or done tests to see if the turn effect is realistically observable or not on a pool table?

Regards,
Dave <hr /></blockquote>Dr. Dave,

Sorry for the delay, but I was hoping to put the following to a test before replying. I'll do the test later.

The draw/follow and sidespin masse effects are compared to the corresponding throw angles here:

http://ww2.netnitco.net/users/gtech/OB_Masse2.jpg

Note that the masse angles are multiplied by four. I used a value for the ball/ball coefficient of friction of 0.06 to get the throw angles and the induced spin on the object ball. The draw/follow curve should be the same as your equation predicts in TP A.24, except there's an ever so slight modification in my equation to account for the cloth's rolling resistance.

So the largest OB curve should be seen, in the case of a full hit, with a friction direction pointing downward at about a 45 degree angle. This corresponds to a tip offset at the 10:30 or 1:30 positions, about halfway toward maximum offset (to maximize friction), when the cueball and object balls are close to each other so that the cueball doesn't pick up much more topspin. You should see something like a quarter inch difference after a cue length's worth of travel between the two cases (10:30 vs. 1:30) for moderately to softly hit balls. Of course, throw has to be supressed by pinning the OB between two other balls. We shall see...

The sidespin effect should occur on napless cloth since it has rolling resistance, ie, a ball is seated in a depression or dimple as it moves along. For a 100 speed cloth, a rolling ball decelerates at 0.01g. We can get the inclination of the net normal force from this with a high degree of certainty; any halfway reasonable guess at the orientation of the net tangential (circumferential) force yields essentially the same figure. Here is a derivation of that 0.8 degree figure mentioned earlier, and which I used in the above graph:

http://ww2.netnitco.net/users/gtech/Rolling_Resistance.jpg

Several centuries of physics may need to be revised if these calculations aren't confirmed. /ccboard/images/graemlins/smile.gif

Jim

dr_dave
12-30-2007, 03:26 PM
<blockquote><font class="small">Quote Jal:</font><hr>The sidespin effect should occur on napless cloth since it has rolling resistance, ie, a ball is seated in a depression or dimple as it moves along. For a 100 speed cloth, a rolling ball decelerates at 0.01g. We can get the inclination of the net normal force from this with a high degree of certainty<hr /></blockquote>My question still remains about how much the rolling resistance dimple effect causes the object ball to turn while it is rolling or sliding with sidespin (and no masse spin). I still think this effect might be too small to measure reliably.

Regards,
Dave

Jal
12-30-2007, 04:21 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote Jal:</font><hr>The sidespin effect should occur on napless cloth since it has rolling resistance, ie, a ball is seated in a depression or dimple as it moves along. For a 100 speed cloth, a rolling ball decelerates at 0.01g. We can get the inclination of the net normal force from this with a high degree of certainty<hr /></blockquote>My question still remains about how much the rolling resistance dimple effect causes the object ball to turn while it is rolling or sliding with sidespin (and no masse spin). I still think this effect might be too small to measure reliably.

Regards,
Dave <hr /></blockquote>Dr. Dave, in the graph, the calculated angles for the sidespin effect are for a spin component perfectly vertical to the slate (no masse component). At a friction direction of 0 or 180 degrees, no draw or follow is present and pure sidespin is the only component. I used the term "masse" to mean curve, no matter what the cause.

An assumption is that the net normal force acts at about an inclination of 0.8 degrees for a sliding ball (it surely does for a rolling ball with a deceleration rate of .01g). If this is true, the ball has to curve. But as you say, it wouldn't be easy to verify, given that the effect, by itself, is tiny.

The calculation does not take into account the fact that the ball faces the same "uphill" climb no matter how much it has previously curved; the force component always acts at right angles to the ball's current direction. However, since the overall effect is so small, the direction of the sideways force hardly changes at all and thus shouldn't affect the calculation much. A very slow moving ball is different, ie, it should follow more of a spiral path, like a charged particle in a magnetic field.

Jim

Bambu
12-31-2007, 05:59 AM
Whoa. Thanks for explaining that better than I ever could, Jim.

dr_dave
12-31-2007, 11:18 AM
<blockquote><font class="small">Quote Jal:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote Jal:</font><hr>The sidespin effect should occur on napless cloth since it has rolling resistance, ie, a ball is seated in a depression or dimple as it moves along. For a 100 speed cloth, a rolling ball decelerates at 0.01g. We can get the inclination of the net normal force from this with a high degree of certainty<hr /></blockquote>My question still remains about how much the rolling resistance dimple effect causes the object ball to turn while it is rolling or sliding with sidespin (and no masse spin). I still think this effect might be too small to measure reliably.

Regards,
Dave <hr /></blockquote>Dr. Dave, in the graph, the calculated angles for the sidespin effect are for a spin component perfectly vertical to the slate (no masse component). At a friction direction of 0 or 180 degrees, no draw or follow is present and pure sidespin is the only component. I used the term "masse" to mean curve, no matter what the cause.

An assumption is that the net normal force acts at about an inclination of 0.8 degrees for a sliding ball (it surely does for a rolling ball with a deceleration rate of .01g). If this is true, the ball has to curve. But as you say, it wouldn't be easy to verify, given that the effect, by itself, is tiny.

The calculation does not take into account the fact that the ball faces the same "uphill" climb no matter how much it has previously curved; the force component always acts at right angles to the ball's current direction. However, since the overall effect is so small, the direction of the sideways force hardly changes at all and thus shouldn't affect the calculation much. A very slow moving ball is different, ie, it should follow more of a spiral path, like a charged particle in a magnetic field.<hr /></blockquote>Jim,

Thanks for the clarification and further explanation. I'm sorry I didn't look at and try to better understand your graph results earlier. The results seem to back up the claim that this effect is probably too small to measure reliably on a real table, and the effect is probably not useful in any realistic game or trick-shot situation. Do you agree?

Thanks again,
Dave

dr_dave
12-31-2007, 11:37 AM
<blockquote><font class="small">Quote Jal:</font><hr>An assumption is that the net normal force acts at about an inclination of 0.8 degrees for a sliding ball (it surely does for a rolling ball with a deceleration rate of .01g). If this is true, the ball has to curve.<hr /></blockquote>Jim, I'm sorry if I'm being more dense than normal, but it's still not clear to me how you are calculating the "turning" force acting perpendicular to the ball's velocity.

Are you assuming the dimple friction torque that slows the sidespin is created by force only at the leading edge of the dimple? And are you calculating the friction torque and force based on measured spin decelerations? If so, what are you assuming about the effective dimple radius of the leading-edge force?

Thanks,
Dave

Bambu
12-31-2007, 11:45 AM
Please forgive my butting in Dr. Dave, but if you would allow me to post a cuetable diagram, I have come up with a shot which can indeed be used to win a game, using what seems like sidespin alone to curve an object ball. This a variation of Bob's shot, but the distance between the object ball and blocking ball is far less.

dr_dave
12-31-2007, 11:55 AM
<blockquote><font class="small">Quote Bambu:</font><hr> Please forgive my butting in Dr. Dave, but if you would allow me to post a cuetable diagram, I have come up with a shot which can indeed be used to win a game, using what seems like sidespin alone to curve an object ball. This a variation of Bob's shot, but the distance between the object ball and blocking ball is far less. <hr /></blockquote>I would like to see it. Please share it.

It would also be good if you can justify that object ball turn is the only or best alternative in the given situation.

Thanks,
Dave

Bambu
12-31-2007, 12:57 PM
http://CueTable.com/P/?@2CXVo2DbHU2EbHn2FbIH2GbIa3Ibbh2PXWa2qQtF&amp;ZZ2vXWa hoa@

After setting this up, remove the 5,6 and 7 balls. Feel free to try making the 9 first using no English, and to also check for table roll. Then try using extreme 9:00 left English to impart right spin to the 3 ball. the spin transfers initially opposite, but then the object ball takes on more of a forward roll, combined with the right spin. When done at just the right speed and with enough english, you can transfer enough spin to that 3 ball to make it curve towards the pocket. Not super slow, maybe a 2-3 out of 10. Line of aim is to just barely not hit the 4. The 3 will go straight for 1-2 balls lengths before curving towards the pocket, if you get it right. The curve is nowhere near enough to sink the 9 ball in Bobs shot, but in this case, if you can manage to get it, that quarter inch helps.
This is a tough shot, but certainly make able. Part of what makes these types of shots so tough, is that you need cue speed to get the spin, but at the same time a soft hit is required to curve the object ball towards the pocket. It is the right combination of the 2 which will sink the ball. You want as much spin as you can get, while still keeping the speed at maybe 2+ out of 10 AND getting the line of aim perfect. Too hard and you will not allow the spin to grab the cloth and take the slight turn.
If this were a game of say, ring game 9 ball, where a safety doesnt do you much good, this would be the choice for me. Even in regular 9 ball, you could lose to a good kick(depending on how good a safety you can pull off). Even if you manage to freeze your cueball perfectly on the 4, the short rail could be used to kick at the 3.

dr_dave
12-31-2007, 01:34 PM
Thank you. Excellent example.

Because there is throw to the right (with the left Engish), the CB must hit the 3-ball a little on the right side (i.e., the CB would hit the 6-ball if it weren't removed). So there is a slight cut angle, and the follow masse-effect could come into play (unless the CB has perfect stun with left spin only at impact).

I'll be sure to try out the shot when I get some time. What do you figure your percentage is to make this shot on your "home" table vs. less familiar conditions?

I don't think this type of shot is likely to come during normal play, but it might be a good "proposition" shot.

Thanks again,
Dave

<blockquote><font class="small">Quote Bambu:</font><hr> http://CueTable.com/P/?@2CXVo2DbHU2EbHn2FbIH2GbIa3Ibbh2PXWa2qQtF&amp;ZZ2vXWa hoa@

After setting this up, remove the 5,6 and 7 balls. Feel free to try making the 9 first using no English, and to also check for table roll. Then try using extreme 9:00 left English to impart right spin to the 3 ball. the spin transfers initially opposite, but then the object ball takes on more of a forward roll, combined with the right spin. When done at just the right speed and with enough english, you can transfer enough spin to that 3 ball to make it curve towards the pocket. Not super slow, maybe a 2-3 out of 10. Line of aim is to just barely not hit the 4. The 3 will go straight for 1-2 balls lengths before curving towards the pocket, if you get it right. The curve is nowhere near enough to sink the 9 ball in Bobs shot, but in this case, if you can manage to get it, that quarter inch helps.
This is a tough shot, but certainly make able. Part of what makes these types of shots so tough, is that you need cue speed to get the spin, but at the same time a soft hit is required to curve the object ball towards the pocket. It is the right combination of the 2 which will sink the ball. You want as much spin as you can get, while still keeping the speed at maybe 2+ out of 10 AND getting the line of aim perfect. Too hard and you will not allow the spin to grab the cloth and take the slight turn.
If this were a game of say, ring game 9 ball, where a safety doesnt do you much good, this would be the choice for me. Even in regular 9 ball, you could lose to a good kick(depending on how good a safety you can pull off). Even if you manage to freeze your cueball perfectly on the 4, the short rail could be used to kick at the 3. <hr /></blockquote>

BigRigTom
12-31-2007, 02:29 PM
Dr. Dave,
Once you remove the 5, 6 &amp; 7 this shot or a slight variation of it does come up in both 8 ball and 9 ball.

Great example of OB throw.
I plan to try this right away.
What better way to end a year than to learn a new shot on the pool table.

Thanks all and have a very Happy New Year!

dr_dave
12-31-2007, 02:51 PM
<blockquote><font class="small">Quote BigRigTom:</font><hr>Great example of OB throw.
I plan to try this right away.
What better way to end a year than to learn a new shot on the pool table.<hr /></blockquote>The claim is the 3-ball is curving after it clears the 4-ball. This really isn't a throw shot. Although, you do need to account for throw; otherwise, the 3-ball will hit the 4-ball. You can't just throw the 3-ball towards the 9-ball; otherwise, it would hit the 4-ball.

Here's the shot for easy reference:
http://CueTable.com/P/?@2CXVo2DbHU2EbHn2FbIH2GbIa3Ibbh2PXWa2qQtF&amp;ZZ2vXWa hoa@

Regards,
Dave

Jal
12-31-2007, 03:09 PM
<blockquote><font class="small">Quote dr_dave:</font><hr>Thanks for the clarification and further explanation. I'm sorry I didn't look at and try to better understand your graph results earlier. The results seem to back up the claim that this effect is probably too small to measure reliably on a real table, and the effect is probably not useful in any realistic game or trick-shot situation. Do you agree?

Thanks again,
Dave <hr /></blockquote>Dr. Dave,

You're welcome and thanks for taking another look at it. I agree with your overall assessment, but Bambu does show a setup where it can be conceivably be demonstrated. If he's seeing something like a quarter inch sideways movement with just pure sidespin, I'm not sure what to make of that. My calculations indicate a much smaller effect, one that should probably be partly masked by random buffeting by the cloth.

Jim

dr_dave
12-31-2007, 03:25 PM
<blockquote><font class="small">Quote Jal:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr>Thanks for the clarification and further explanation. I'm sorry I didn't look at and try to better understand your graph results earlier. The results seem to back up the claim that this effect is probably too small to measure reliably on a real table, and the effect is probably not useful in any realistic game or trick-shot situation. Do you agree?

Thanks again,
Dave <hr /></blockquote>Dr. Dave,

You're welcome and thanks for taking another look at it. I agree with your overall assessment, but Bambu does show a setup where it can be conceivably be demonstrated. If he's seeing something like a quarter inch sideways movement with just pure sidespin, I'm not sure what to make of that. My calculations indicate a much smaller effect, one that should probably be partly masked by random buffeting by the cloth.<hr /></blockquote>I look forward to trying Bambu's shot. Have you tried it yet? I still doubt the value of this effect for normal play; but if it works reliably and repeatably with a little practice, it might be a good "proposition" shot.

Thanks again for helping to keep me honest.

Regards,
Dave

Jal
12-31-2007, 05:36 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote Jal:</font><hr>An assumption is that the net normal force acts at about an inclination of 0.8 degrees for a sliding ball (it surely does for a rolling ball with a deceleration rate of .01g). If this is true, the ball has to curve.<hr /></blockquote>Jim, I'm sorry if I'm being more dense than normal, but it's still not clear to me how you are calculating the "turning" force acting perpendicular to the ball's velocity.

Are you assuming the dimple friction torque that slows the sidespin is created by force only at the leading edge of the dimple? And are you calculating the friction torque and force based on measured spin decelerations? If so, what are you assuming about the effective dimple radius of the leading-edge force?

Thanks,
Dave <hr /></blockquote>Dr. Dave, if I were ever foolish enough to wander into one of your engineering classes, I would show you the true meaning of "dense". /ccboard/images/graemlins/smile.gif

For better or worse, I calculated it using (essentially) the familiar expression that applies to an idealized point contact with the cloth:

V' = (5/7)[V - (2/5)W X R]

V is composed of the line of impact velocity, Vi, along with the throw velocity, Vt. From transfered draw/follow spin, the term W X R contributes something in the Vi direction, which has components parallel and perpendicular to V. So far, this is exactly the same as your analysis in TP A.24. The only change I made was to multiply that something contributed by W X R in the Vi direction by cos(0.8 deg). In other words, the effective table surface is slightly inclined to the real surface and the horizontal velocity of a ball. This is somewhat questionable perhaps, but it only makes for a very slight change.

For the sidespin, W X R contributes RWsin(0.8) perpendicular to V, where R is taken to be inclined from the vertical by 0.8 degree. While this surely isn't exact since the force component generated by the vertical spin is always perpendicular to a ball's motion, I think it's probably a decent approximation. The justification is that the ball should curve until the "vertical" component of its spin becomes aligned with R, ie, the Wsin(0.8) component is removed. And of course, it involves the assumption that the net normal force is inclined by 0.8 deg while a ball is sliding, as well as rolling.

No doubt you could do better if motivated to analyze this in detail. I will probably look at it further, mainly in regard to that ever perpendicular force. If you see any fatal flaws or improvements that can be made, please let me know.

I haven't tried Bambu's or Bob J's shots yet, but plan on it shortly. I'm preparing the crow as we speak.

Jim

BigRigTom
12-31-2007, 05:37 PM
I just tried it and made the shot 3 times in row using extreme left (9 oclock) on the cue ball with a little less than lag speed.

Dr. Dave, you say this is not a throw shot?
I am confused. I thought it was a throw because you use left on the cue ball and hit the right side of the object ball causing the object ball to travel to the right after it clears the 4.


Straighten me out if I am wrong here.. /ccboard/images/graemlins/confused.gif

By the way I can see this example being more meaningful if you were shooting the 7 past the 8 to make the 9. That would be a much higher incentive to make that shot and NOT attempt a safe.

Bambu
12-31-2007, 05:58 PM
Thanks Dr. Dave. I have been working hard at this, and am happy to have others try the shot. As far as percentages go, I am maybe 50/50 on this shot, with room for maybe 25% improvement with practice. This shot is very difficult(in my opinion of course)but like any shot, percentages will vary with skill level and practice. I cant really compare that number to what would happen on another table, because I havent been playing anywhere else but home for quite awhile. But I can speculate, based on my equipment and knowing what a typical pool room has.
I have a gold crown 4 with simonis 860, about a year old and maybe 500 hours of play. My ball set is aramith super pro cup, only about 3-4 months old and recently cleaned. Because my equipment is fairly new, I dont expect other tables to pose more of a problem unless they have new cloth.

Bambu
12-31-2007, 06:07 PM
With only those balls left, its all the same anyway.

dr_dave
12-31-2007, 06:20 PM
Jal,

I'll need to think this over some. I also want to spend some time with Bambu's shot under different conditions and convince myself the effect is significant. If I feel motivated and find some time, I'll try to modify and extend the analysis in TP A.4 and TP A.24, taking into account rolling resistance and dimple-spin friction torque (but I don't think the equations will be solvable analytically anymore).

Thanks,
Dave

<blockquote><font class="small">Quote Jal:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote Jal:</font><hr>An assumption is that the net normal force acts at about an inclination of 0.8 degrees for a sliding ball (it surely does for a rolling ball with a deceleration rate of .01g). If this is true, the ball has to curve.<hr /></blockquote>Jim, I'm sorry if I'm being more dense than normal, but it's still not clear to me how you are calculating the "turning" force acting perpendicular to the ball's velocity.

Are you assuming the dimple friction torque that slows the sidespin is created by force only at the leading edge of the dimple? And are you calculating the friction torque and force based on measured spin decelerations? If so, what are you assuming about the effective dimple radius of the leading-edge force?

Thanks,
Dave <hr /></blockquote>Dr. Dave, if I were ever foolish enough to wander into one of your engineering classes, I would show you the true meaning of "dense". /ccboard/images/graemlins/smile.gif

For better or worse, I calculated it using (essentially) the familiar expression that applies to an idealized point contact with the cloth:

V' = (5/7)[V - (2/5)W X R]

V is composed of the line of impact velocity, Vi, along with the throw velocity, Vt. From transfered draw/follow spin, the term W X R contributes something in the Vi direction, which has components parallel and perpendicular to V. So far, this is exactly the same as your analysis in TP A.24. The only change I made was to multiply that something contributed by W X R in the Vi direction by cos(0.8 deg). In other words, the effective table surface is slightly inclined to the real surface and the horizontal velocity of a ball. This is somewhat questionable perhaps, but it only makes for a very slight change.

For pure sidespin, W X R contributes RWsin(0.8) perpendicular to V, where R is taken to be inclined from the vertical by 0.8 degree. While this surely isn't exact since the force component generated by the vertical spin is always perpendicular to a ball's motion, I think it's probably a decent approximation. The justification is that the ball should curve until the "vertical" component of its spin becomes aligned with R, ie, the Wsin(0.8) component is removed. And of course, it involves the assumption that the net normal force is inclined by 0.8 deg while a ball is sliding, as well as rolling.

No doubt you could do better if motivated to analyze this in detail. I will probably look at it further, mainly in regard to that ever perpendicular force. If you see any fatal flaws or improvements that can be made, please let me know.

I haven't tried Bambu's or Bob J's shots yet, but plan on it shortly. I'm preparing the crow as we speak.

Jim <hr /></blockquote>

BigRigTom
12-31-2007, 06:22 PM
<blockquote><font class="small">Quote Bambu:</font><hr> Thanks Dr. Dave. I have been working hard at this, and am happy to have others try the shot. As far as percentages go, I am maybe 50/50 on this shot, with room for maybe 25% improvement with practice. This shot is very difficult(in my opinion of course)but like any shot, percentages will vary with skill level and practice. I cant really compare that number to what would happen on another table, because I havent been playing anywhere else but home for quite awhile. But I can speculate, based on my equipment and knowing what a typical pool room has.
I have a gold crown 4 with simonis 860, about a year old and maybe 500 hours of play. My ball set is aramith super pro cup, only about 3-4 months old and recently cleaned. Because my equipment is fairly new, I dont expect other tables to pose more of a problem unless they have new cloth. <hr /></blockquote>

I am invious!
Sounds like you have a sweet set up. I will someday have a GC III or maybe a GC V by the time I can afford it. The Gold Crown IV is a great loooking table but I never actually played on one.
By the way I went back to your shot and I guess the doubt had creeped into my mind because I made only 3 of the last 8 shots. I guess those 3 in a row were a bit of a fluke or maybe I just didn't realize how hard it was supposed to be until I came back to my desk and read more about it.

Thanks again for posting this, it is an interesting practice shot.
Happy New Year All!

Bambu
12-31-2007, 06:24 PM
Thanks for trying the shot, Tom. I am glad you made it. And I agree, these shots come up more than many realize. Its just that you dont see it if youre not looking for it.

dr_dave
12-31-2007, 06:35 PM
<blockquote><font class="small">Quote BigRigTom:</font><hr>Dr. Dave, you say this is not a throw shot?
I am confused. I thought it was a throw because you use left on the cue ball and hit the right side of the object ball causing the object ball to travel to the right after it clears the 4.<hr /></blockquote>Throw occurs only while the CB is in contact with the OB. The left English throws the OB to the right. That's why the CB must hit the OB a little right of center, so the throw makes the OB narrowly miss the 4-ball. For the 3-ball to curve after passing the 4-ball, something other than throw (e.g., OB masse spin or nap turn) must occur as the 3-ball slides and then rolls up table toward the 9-ball; otherwise, the 3-ball would head in a straight line in the thrown direction (e.g., see Diagram 1 in my August '06 article (http://billiards.colostate.edu/bd_articles/2006/aug06.pdf)).

Regards,
Dave

dr_dave
12-31-2007, 06:46 PM
Sorry if I have seemed a little hesitant or unaccepting. I just want to try some things out myself first(unfortuantely, I won't have access to my table for a couple of more days). I would also like to look at the physics a little closer to be able to explain exactly what is going on. Thanks again for bringing this to our attention.

Happy New Year,
Dave

<blockquote><font class="small">Quote Bambu:</font><hr> Thanks Dr. Dave. I have been working hard at this, and am happy to have others try the shot. As far as percentages go, I am maybe 50/50 on this shot, with room for maybe 25% improvement with practice. This shot is very difficult(in my opinion of course)but like any shot, percentages will vary with skill level and practice. I cant really compare that number to what would happen on another table, because I havent been playing anywhere else but home for quite awhile. But I can speculate, based on my equipment and knowing what a typical pool room has.
I have a gold crown 4 with simonis 860, about a year old and maybe 500 hours of play. My ball set is aramith super pro cup, only about 3-4 months old and recently cleaned. Because my equipment is fairly new, I dont expect other tables to pose more of a problem unless they have new cloth. <hr /></blockquote>

Bambu
12-31-2007, 06:55 PM
I hate to say it, but I have another shot which proves throw does not occur in a straight line. My wife is really pissed at me, but I will post that too if you care to see it. This is another way to curve an object ball, by using throw.

Bambu
12-31-2007, 07:09 PM
On the contrary Dr. Dave. You have been far more open minded about this than many others I have "thrown" this train of thought at. By all means, take your time. I really do appreciate every minute of it.

Bob_Jewett
12-31-2007, 08:55 PM
<blockquote><font class="small">Quote Bambu:</font><hr> http://CueTable.com/P/?@2CXVo2DbHU2EbHn2FbIH2GbIa3Ibbh2PXWa2qQtF&amp;ZZ2vXWa hoa@

After setting this up, remove the 5,6 and 7 balls. ... <hr /></blockquote>
In the diagram, at least the way it displays for me, the cue ball is not frozen to the 7 and the 3 ball is not frozen to the 5. I assume that the intent is to have those balls frozen. I think there is no reason to remove the 5 before shooting the shot. Having it in place ensures that the 3 has not moved out from the rail at all (or in for that matter).

Another way that I would modify the shot is to move the nine ball up the long cushion a ball or two from the pocket and freeze it so there is no possibility of confusion about how much the nine is sticking out or whether the 3 ball hits the 9 coming off the jaw of the pocket.

dr_dave
12-31-2007, 11:08 PM
<blockquote><font class="small">Quote Bambu:</font><hr> I hate to say it, but I have another shot which proves throw does not occur in a straight line. My wife is really pissed at me, but I will post that too if you care to see it. This is another way to curve an object ball, by using throw. <hr /></blockquote>Feel free to post as many examples as you like. You don't need to ask for permission. I think more examples of OB swerve might be useful in the debate.

Happy New Year,
Dave

Bambu
01-01-2008, 01:31 PM
I regret that I am new at using cuetable, please forgive the error. Yes, all the balls should be frozen. And youre right about the 5 ball. I just find aiming a bit easier with less balls around. I tried to position the 9 as best I could, trying to be sure it was on the proper side of the tangent. For some reason, the tangent line wouldnt extend to the pocket entirely.

Bambu
01-01-2008, 02:03 PM
I am prepared to prove through specific shots that both spin transfer AND throw, or bothÖ..will make your object ball curve. I like calling it ďangle bendingĒ better than curve, but thatís just my preference. While it may be true that spin transfer alone will only get you an extra quarter inch of a curve, a throw shot with 2 frozen balls can give you as much as nearly a diamonds difference. If you donít believe that, you are free to experiment with this shot:

http://CueTable.com/P/?@2HATl1IATT2PMMr2vATlhjS@

While this shot may not actually prove I can curve an object ball, itís a good way to see what speed alone can do to a throw shot. And letís not forget, every shot which isnít straight, IS a throw shot. This is also a good way to actually see the curve take place if you are looking for it. Now if I had a way to insert a blocking ball in front of the 8 ball in a consistent mannor, I would have. And, I invite anyone here to try. Just put a sliver of a blocking ball in the path of the 9 ball, and see if you can still make the same shot. The blocking ball edge must be within 1-2 balls lengths from the 9.
But thatís not good enough. You guys want proof, right? Ok. To take this a step further, I did find a better way to reproduce a similar type of shot. In this shot, I freeze 4 balls together. Next, using an ordinary music cd,(I sacrificed a judas priest cd for this!) insert the cd between the 9 ball, and ball A. Tap all 4 balls together to make sure they are frozen in place. Next, remove the cd and ball B, and place ball B where the 5 sits in the diagram. Now remove ball A. You have just set up a shot which now looks impossible. Specifically, the 9 ball cannot go directly straight into the pocket without hitting the 5. So how does it go in? It curves into the pocket. That is the only possible way, unless someone can explain otherwise. If you cant make this shot on the first few tries, donít be discouraged. It is not an easy shot, but it can be made.
Hint: aim to cut the 4 ball thin, as if you were going to cut it straight up, using left English helps too. Part of what makes these types of shots so tough, is that you need cue speed to get the spin, but at the same time a soft hit is required to throw the object ball back into line of the pocket. It is the right combination of the 2 which will sink the ball. You want as much spin as you can get, while still keeping the speed at 2-3 out of 10. Too fast and you will not allow the spin to grab the cloth and take the slight turn toward the pocket.

http://cuetable.com/P/?@1DXdB1EbNP1IXTi1POoa1QbNj1RbOB1vbNjhoa@

Bambu
01-01-2008, 03:38 PM
Now if I had a way to insert a blocking ball in front of the 8 ball in a consistent mannor, I would have.

Sorry, I really meant the 9 ball here.

dr_dave
01-01-2008, 04:17 PM
Bambu,

Your first example with the 3-ball curving to pocket the 9-ball (http://cuetable.com/P/?@2CXVo2DbHU2EbHn2FbIH2GbIa3Ibbh2PXWa2qQtF&amp;ZZ2vXWa hoa@) definitely requires OB curve/swerve/bend/turn. Throw alone is not enough.

However, I don't think your two new examples are as convincing at distinguishing OB curve/swerve/bend/turn from throw. Without adding blocking balls, the frozen 8-ball-9-ball shot (http://cuetable.com/P/?@2HATl1IATT2PMMr2vATlhjS@) is just a classic frozen-ball "throw shot," which does not require OB curve/swerve/bend/turn after impact.

FYI, in case you haven't seen these yet, I have several examples of throw and spin transfer shots on my website:
- NV 4.15 - Using throw to make a partially blocked shot (http://billiards.colostate.edu/normal_videos/NV4-15.htm)
- NV 4.16 - Over-cutting a cut shot to compensate for throw (http://billiards.colostate.edu/normal_videos/NV4-16.htm)
- NV 7.5 - Frozen ball throw (http://billiards.colostate.edu/normal_videos/NV7-5.htm)
- NV 7.6 - Frozen cue ball throw (http://billiards.colostate.edu/normal_videos/NV7-6.htm)
- NV A.18 - Colin Colenso's throw test video (effects of speed and English) (http://billiards.colostate.edu/normal_videos/new/NVA-18.htm)
- NV A.21 - Bank shot using throw and spin transfer (http://billiards.colostate.edu/normal_videos/new/NVA-21.htm)

I also show and describe examples in my series of 12 articles on throw (http://billiards.colostate.edu/bd_articles/index.html). Check them out.

I'll comment on the remainder of your message (and the 2nd example) in a follow-up message.

Thanks again for posting the examples,
Dave

dr_dave
01-01-2008, 04:26 PM
<blockquote><font class="small">Quote Bambu:</font><hr>... every shot which isnít straight, IS a throw shot ...<hr /></blockquote>I personally don't like to use the phrase "throw shot" unless throw is the primary effect specifically being used to your advantage to make the shot. But, putting aside semantics for now, I agree ... with one exception: a shot with "gearing" (or "natural") outside English (gOE or NOE) also has no throw (see my January '07 article (http://billiards.colostate.edu/bd_articles/2007/jan07.pdf) for more info).

Regards,
Dave

dr_dave
01-01-2008, 04:44 PM
<blockquote><font class="small">Quote Bambu:</font><hr>In this shot, I freeze 4 balls together. Next, using an ordinary music cd,(I sacrificed a judas priest cd for this!) insert the cd between the 9 ball, and ball A. Tap all 4 balls together to make sure they are frozen in place. Next, remove the cd and ball B, and place ball B where the 5 sits in the diagram. Now remove ball A. You have just set up a shot which now looks impossible. Specifically, the 9 ball cannot go directly straight into the pocket without hitting the 5. So how does it go in? It curves into the pocket. That is the only possible way, unless someone can explain otherwise. If you cant make this shot on the first few tries, donít be discouraged. It is not an easy shot, but it can be made.
Hint: aim to cut the 4 ball thin, as if you were going to cut it straight up, using left English helps too. Part of what makes these types of shots so tough, is that you need cue speed to get the spin, but at the same time a soft hit is required to throw the object ball back into line of the pocket. It is the right combination of the 2 which will sink the ball. You want as much spin as you can get, while still keeping the speed at 2-3 out of 10. Too fast and you will not allow the spin to grab the cloth and take the slight turn toward the pocket.

http://cuetable.com/P/?@1DXdB1EbNP1IXTi1POoa1QbNj1RbOB1vbNjhoa@
<hr /></blockquote>Depending on the size and cut of the pocket, I think this shot might not need post-impact OB curve/swerve/bend/turn to work. In other words, because of the slight angle to the pocket you have created with gap, throw and spin transfer alone might be enough to send the 9-ball in a straight line to the wall ("jaw") of the pocket.

Again, I like your original example (http://cuetable.com/P/?@2CXVo2DbHU2EbHn2FbIH2GbIa3Ibbh2PXWa2qQtF&amp;ZZ2vXWa hoa@) better; because with that shot, it is clear post-impact OB swerve/curve/bend/turn is required to make the shot (provided you are not partially hopping the 3-ball over the 4-ball with a slight CB hop).

Regards,
Dave

PS: I'll still report back after I get a chance to test out your examples. I'm also hoping others will report their results with the original example.

Bambu
01-01-2008, 05:13 PM
Thanks Dr. Dave. When you say "I don't think your two new examples are as convincing at distinguishing OB curve/swerve/bend/turn from throw."
You are right about that, Dr. Dave, I cannot distinguish one from the other. The best I can say about that, is that they are one and the same. Throw itself is indicative of curve, where speed, english and angle determine how much of a curve. I only use the 2 frozen balls to dramatize the throw effect, and to show what speed can do to curve an object ball. When you say throw does not require OB curve/swerve/bend/turn after impact, I have to disagree. I am hoping that my shot with the cd proves this. I did look at your videos, and all make valid points. However, with all due respect, I have to disagree about throw occuring in a straight line.

Bambu
01-01-2008, 05:24 PM
Dr. Dave, if you look down the line of aim, you will see that it is impossible for the ball to take a straight path and still go in. Good point about the pocket size, If they were bigger than mine the shot might even go straight in. I'd say my pockets are medium, but I will take a measurement.

Bambu
01-01-2008, 05:27 PM
Yes, I agree with that Dr. Dave. Outside english cancels out much of the throw effect. That is the way to straighten out your object ball path as much as possible.

dr_dave
01-01-2008, 07:10 PM
Please look at my throw articles (http://billiards.colostate.edu/bd_articles/index.html) when you get a chance. I spent lots of time studying and doing experiments with throw during that year.

I still think it is good to understand and distinguish among the different effects. Squirt occurs only while the cue tip is in contact with the CB. Swerve (CB curve) occurs only while the CB is sliding on its way to the OB. Throw occurs only while the CB is in contact with the OB. OB swerve/curve/bend/turn occurs only while the OB is sliding and/or rolling to the target.

Throw (change in the initial OB angle off the CB) is a much, much larger effect than the OB swerve/turn effect your first example is designed to demonstrate.

I know the distinction might sound like semantics to you and some others, but to me it is very important.

Regards,
Dave

<blockquote><font class="small">Quote Bambu:</font><hr> Thanks Dr. Dave. When you say "I don't think your two new examples are as convincing at distinguishing OB curve/swerve/bend/turn from throw."
You are right about that, Dr. Dave, I cannot distinguish one from the other. The best I can say about that, is that they are one and the same. Throw itself is indicative of curve, where speed, english and angle determine how much of a curve. I only use the 2 frozen balls to dramatize the throw effect, and to show what speed can do to curve an object ball. When you say throw does not require OB curve/swerve/bend/turn after impact, I have to disagree. I am hoping that my shot with the cd proves this. I did look at your videos, and all make valid points. However, with all due respect, I have to disagree about throw occuring in a straight line. <hr /></blockquote>

Jal
01-01-2008, 07:12 PM
<blockquote><font class="small">Quote Bambu:</font><hr> Thanks Dr. Dave. When you say "I don't think your two new examples are as convincing at distinguishing OB curve/swerve/bend/turn from throw."
You are right about that, Dr. Dave, I cannot distinguish one from the other. The best I can say about that, is that they are one and the same. Throw itself is indicative of curve, where speed, english and angle determine how much of a curve. I only use the 2 frozen balls to dramatize the throw effect, and to show what speed can do to curve an object ball. When you say throw does not require OB curve/swerve/bend/turn after impact, I have to disagree. I am hoping that my shot with the cd proves this. I did look at your videos, and all make valid points. However, with all due respect, I have to disagree about throw occuring in a straight line. <hr /></blockquote>Bambu,

I'm with you that object ball curve occurs and that it can be much larger than, say, .01 degree.

Your latest test though, doesn't prove anything. I measured one of my CDs and it's just about 1/16 inch thick. If that's the size of the gap you used in the test, then the object ball can move nearly 1-3/4 inches closer to the side cushion on a straight line path before reaching the pocket.

If you could show up to 3-5 degrees of curve with the setup shown in your first diagram, and more typically 1/2 to 2 degrees, then your hypothesis would be proven. It's generally understood that that's how much friction during ball-to-ball contact can change the OB's direction. If this is in fact happening after the collision, then you should be able to get the OB to contact the side cushion well before the pocket.

Just to note that one degree is 1 inch sideways for every 57 inches forward.

Jim

Bambu
01-01-2008, 07:13 PM
I consider the throw on any cut shot. It is not the most important aspect of the shot, but must be accounted for. If you dont factor speed and english into a shot, youre not accounting for throw.

dr_dave
01-01-2008, 07:21 PM
<blockquote><font class="small">Quote Bambu:</font><hr> I consider the throw on any cut shot. It is not the most important aspect of the shot, but must be accounted for. If you dont factor speed and english into a shot, youre not accounting for throw.<hr /></blockquote>I would agree that throw must be considered on many shots. Also, the amount of throw (the initial change in angle of the OB off the CB) depends on cut angle, speed, the amount and type of English, the amount of top/bottom spin, ball conditions in general, and sometimes specific conditions at the point of contact (e.g., as with a chalk smudge causing "cling").

Regards,
Dave

Bambu
01-01-2008, 07:55 PM
I agree, both shots show different things. The first shows what spin transfer alone can do, although I do see the point you made about the hit not being completely full. Because I thought the hit was full, I didnt think this classified as a throw shot. I stand corrected.
As for the second shot, it adds the advantage of angle, as well as dramatizes the effect of throw with the frozen balls. They are both designed to make different points. I agree, the first example will not have nearly as much of an effect as the second.
I get a bit confused when you say throw occurs only while the CB is in contact with the OB, then at the same time say OB swerve/curve/bend/turn occurs only while the OB is sliding and/or rolling to the target. I look at the entire path of the object ball as involving throw. The bend occurs while the ob slides/rolls because it is part of the initial reaction. At least, thats my interpretation. I will try to read as many of your articles as I can for a second time. But my only disagreement is that throw does not always occur in a straight path. The harder you hit, and the more outside english used, the straighter the path will truly be, because you are thereby eliminating the throw to a large degree. This can be seen most with long distance shots.

Bambu
01-01-2008, 08:12 PM
Jal, I suspect that our table dimensions are slightly different. I will have to be more specific in my pocket size, as well as the thickness of the cd I am using. I can assure you that the way I set it up at home, the shot looks impossible to go in a straight path, and still go in.
I am not sure why you say I need to show a 3-5 degree curve in the first example in order for the point to be valid. Without an angle to help aid the curve, getting 3-5 degrees is impossible, at least for me. My only wish is to acknowledge even the quarter inch, even without an angle. Sometimes I can get more than that, but I cannot gauge how much more. I also feel that better players than me will have better results.

Bambu
01-01-2008, 08:30 PM
Its hard for me to relate to throw as being an initial change in angle of the ob off the cb. I see the whole path as one reaction. I dont believe the angle instantly changes upon impact. Rather, its a continuous effect determined by speed, english and angle. Both shots I have show this.
Even in the first shot, if the angle truly changed upon impact, it would be impossible to get any curve after passing the blocking ball. Instead, the blocking ball would be hit because the angle changed upon impact.

dr_dave
01-01-2008, 09:30 PM
<blockquote><font class="small">Quote Bambu:</font><hr> Its hard for me to relate to throw as being an initial change in angle of the ob off the cb. I see the whole path as one reaction. I dont believe the angle instantly changes upon impact. Rather, its a continuous effect determined by speed, english and angle. Both shots I have show this.<hr /></blockquote>I disagree, but I don't think I can add anything else to what I have written already on this point (in this thread and in my articles).

<blockquote><font class="small">Quote Bambu:</font><hr>Even in the first shot, if the angle truly changed upon impact, it would be impossible to get any curve after passing the blocking ball. Instead, the blocking ball would be hit because the angle changed upon impact.<hr /></blockquote>There is throw on this shot, but it happens well before the blocking ball. A small cut angle must be created (e.g., with squirt and/or aim adjustment) to cancel the effects of the throw angle. The result is: the OB initially heads straight up table to narrowly clear the blocking ball (see the diagrams and explanation in the 2nd half of my July '07 article (http://billiards.colostate.edu/bd_articles/2007/july07.pdf) for more info). Then, after the blocking ball is cleared, the OB apparently curves a very small amount towards the target (enough to pocket the 9-ball). This is what we are calling OB swerve or curve or bend or turn (not throw). This can't happen without the spin transferred to the OB by the throwing force (during impact), but it is not what people usually refer to as throw. In fact, people don't usually refer to it at all. Maybe your examples will help change that.

Regards,
Dave

dr_dave
01-01-2008, 10:03 PM
<blockquote><font class="small">Quote Bambu:</font><hr>... I get a bit confused when you say throw occurs only while the CB is in contact with the OB, then at the same time say OB swerve/curve/bend/turn occurs only while the OB is sliding and/or rolling to the target ...<hr /></blockquote>When the CB hits the OB with English, sliding between the balls creates a "throwing force" resulting from friction (see the diagrams and explanations in my August '06 article (http://billiards.colostate.edu/bd_articles/2006/aug06.pdf)). This force acts only while the balls are in contact. The force does two things. It immediately "throws" the OB off the "impact line" (AKA "line of centers"). This is called "throw." The other thing the force does is "transfer spin" to the OB (see my March '07 article (http://billiards.colostate.edu/bd_articles/2007/mach07.pdf)). Based on your original example and Jal's explanations, this spin, along with sliding/rolling resistance, causes the OB path to curve a slight amount. This is what we call "OB swerve" (or curve or bend or turn). To me these are two different effects. The "throw" effect is much, much larger than the "OB swerve" effect. Believe it or not, some people don't even believe that "throw" is significant or useful ... and "OB swerve" is a much, much smaller effect! Obviously, I'm not one of these "people."

<blockquote><font class="small">Quote Bambu:</font><hr>... my only disagreement is that throw does not always occur in a straight path ...<hr /></blockquote>"Throw" makes the OB head in one direction (by as much as 5 degrees or more off the "impact line"), and "OB swerve" can change that direction slightly (maybe a few tenths of a degree) during OB motion (but after the throw has already occurred). Again, I think my explanations are consistent with how people typically use all of these terms.

Regards,
Dave

Bambu
01-01-2008, 10:03 PM
That is an interesting analysis of the shot, and I dont disagree with it. I regret I dont have the ability to break it down the way you do, Dr. Dave. If I could change the way people looked at pool even a tiny bit, it would be the best accomplishment I could ever imagine.

Bambu
01-01-2008, 10:32 PM
I understand that what you say is widely accepted. Nonetheless, in as polite a way as possible....it is my intention to show that the throw angle is developed over distance, rather than determined upon impact. I am hoping some people have success with the 2 shots I have prepared, because they show that if the throw path were truly straight, and determined upon impact, sinking the balls would be impossible. I agree that the "throw" effect is much, much larger than the "OB swerve" effect. I just look at the whole effect as part of the throw.
I dont like considering this object ball swerve because its not the same as swerve on the cueball. I say that because whatever swerve effect amounts from the throw, was not caused by a downward hit. Object balls react differently than cueballs for that reason, and also because there is no squirt, only spin transfer and throw.

Jal
01-02-2008, 12:20 AM
<blockquote><font class="small">Quote Bambu:</font><hr> I understand that what you say is widely accepted. Nonetheless, in as polite a way as possible....it is my intention to show that the throw angle is developed over distance, rather than determined upon impact. I am hoping some people have success with the 2 shots I have prepared, because they show that if the throw path were truly straight, and determined upon impact, sinking the balls would be impossible. I agree that the "throw" effect is much, much larger than the "OB swerve" effect. I just look at the whole effect as part of the throw.
I dont like considering this object ball swerve because its not the same as swerve on the cueball. I say that because whatever swerve effect amounts from the throw, was not caused by a downward hit. Object balls react differently than cueballs for that reason, and also because there is no squirt, only spin transfer and throw. <hr /></blockquote>Your wish to include an OB's curve in the concept of throw seems reasonable to me, but why cause more confusion when "throw" already has a specific meaning, as Dr. Dave has been pointing out? JoeyA of the AZB forum came up with the term "squerve" to describe squirt + swerve, so why not use something like "thurve" or "thrurve" or "thuerve" or "thruerve" or "deflection" (oh boy), or whatever to describe the combined effect?

As far as that gap in your second test goes, if the object ball is allowed to move sideways by 1/16" in 2-1/4" of travel, as per your setup and if the gap is in fact 1/16", then it will move almost 1-3/4" sideways after 62" of travel. This is in a straight line. That's certainly enough to make the shot with room to spare, isn't it? Maybe your gap is smaller?

At times it has appeared to me that the OB curved at least a few degrees. So I did test it several years ago with something like yours or Bob J.'s setup, and couldn't get it to do nothin. However, I didn't know how to maximize the effect(s) then, and wasn't trying to measure it with any precision.

Jim

Bob_Jewett
01-02-2008, 01:37 AM
<blockquote><font class="small">Quote Bambu:</font><hr> ...it is my intention to show that the throw angle is developed over distance, rather than determined upon impact. I am hoping some people have success with the 2 shots I have prepared, because they show that if the throw path were truly straight, and determined upon impact, sinking the balls would be impossible. ... <hr /></blockquote>
No. I understand that you are passionate about this topic, but your demo does not show curve. I duplicated your setup for the second shot you proposed -- with the CD -- and the object ball simply fits to the pocket. No curve is required. It is thrown along a straight line.

You will have to find some other demo, such as not moving the ball off the cushion by the CD thickness and still making it.

So far, the effect you claim, even if it were real, is not large enough to be useful. I think there is almost no situation you can describe in which it would be the right shot. It can only be the right shot if hitting the blocking ball is not a disaster.

I think you can get a much higher percentage on curve shots by shooting slowly and depending on the table to roll left or right. You probably have a 50-50 chance that way.

cushioncrawler
01-02-2008, 02:00 AM
<blockquote><font class="small">Quote Jal:</font><hr>....At times it has appeared to me that the OB curved at least a few degrees. So I did test it several years ago with something like yours or Bob J.'s setup, and couldn't get it to do nothin. However, I didn't know how to maximize the effect(s) then, and wasn't trying to measure it with any precision...<hr /></blockquote>Jim -- Just thinking...
I remember doing some tests rolling qballs (rampballs) down a ramp into OBs, to meazure the throw. When i rubbed chalk on the OB the throw "off-line" woz of course at a max, but i woz amazed at how much the OB kurved early in its journey. This woz for a "rolling impakt". Here the qball woz akting a bit like a cue might when playing a 45dg (??dg) masse. Logikally there must be a similarish small masse-kurv with a non-chalked impakt -- i havnt had a good look, but it woznt obvious.

The trouble iz that much of the (rolling) masse-effekt iz lost even before the OB haz cleared its own footprint. The chalky-impakt woz strong enuff for the ball to take some masse effekt beyond the footprint.

A stun-impakt wouldnt give any masse kurv. But i reckon that there would be a bit of extra throw due to friktion in the leading edge of the OB while bobbling out of its own footprint. This sort of side-wayz (footprint) friktion would exist whenever there woz any throw -- but i guess less so when the qball haz severe backspin at impakt, here the OB would be thrown upish a little, or at least it wouldnt be thrown downish az much az in the rolling impakt.

Friktion in the leading edge of the footprint might inkreec the throw (or at least inkreec the apparent early throw), and similar friktion would further inkreec the apparent throw a little later, and this would continue untill this source of friktion evaporated. But then the rezidual sidespin would start to pull-push the OB the "other way", ie diminish the apparent throw, az the OB slowz, and this would continue untill the sidespin fell to zero. On my (direktionally) nappy 12' table, i of course get other (additional) kurv-effekts that u dont get on your napless (or non-direktional) bed-cloths.

When the qball haz severe backspin, any masse would narrow the apparent throw. I think that BobJ haz mentioned seeing this sort of effekt in hiz own tests. I tryd it, by hitting upwardz throo the netting of a corner pocket, but without "success" -- it needz an assistant. Perhaps u could do some chalky (backspin) tests on a pool table, to exaggerate this "reverse-masse" -- az i say, this would need an assistant. madMac.

Bambu
01-02-2008, 10:44 AM
By taking more specific measurements, a friend and I will figure out why the shot looks like it goes in straight for some. For me, it only goes straight in if I add a second cd as a spacer. I might need a micrometer and some spark plug gap feelers to get the spacing perfect.

Bob_Jewett
01-02-2008, 02:29 PM
<blockquote><font class="small">Quote Bambu:</font><hr> By taking more specific measurements, a friend and I will figure out why the shot looks like it goes in straight for some. For me, it only goes straight in if I add a second cd as a spacer. I might need a micrometer and some spark plug gap feelers to get the spacing perfect. <hr /></blockquote>
I think that if you need spark plug gap feelers to determine whether you need to do something very special to the cue ball, the shot is not practical. It may be interesting to the nerdy science types (who already believe that you can get 0.1 degree or so of curve from side), but there are essentially zero shots where it would be useful. As far as I can tell, your method only applies when the blocker is within a very short distance of the cue ball. On such shots, it is hard for most people to see exactly how much of the pocket is blocked.

Again: I suggest you try the shot I proposed to begin with in which the object ball is exactly one ball off the rail. Report how much of a distant ball on the rail you can hit. Alternatively, put a distant ball exactly two ball diameters off the rail and see if you can avoid hitting it and if so, by how much.

Jal
01-02-2008, 06:43 PM
<blockquote><font class="small">Quote cushioncrawler:</font><hr> <blockquote><font class="small">Quote Jal:</font><hr>....At times it has appeared to me that the OB curved at least a few degrees. So I did test it several years ago with something like yours or Bob J.'s setup, and couldn't get it to do nothin. However, I didn't know how to maximize the effect(s) then, and wasn't trying to measure it with any precision...<hr /></blockquote>Jim -- Just thinking...
I remember doing some tests rolling qballs (rampballs) down a ramp into OBs, to meazure the throw. When i rubbed chalk on the OB the throw "off-line" woz of course at a max, but i woz amazed at how much the OB kurved early in its journey. This woz for a "rolling impakt". Here the qball woz akting a bit like a cue might when playing a 45dg (??dg) masse. Logikally there must be a similarish small masse-kurv with a non-chalked impakt -- i havnt had a good look, but it woznt obvious.<hr /></blockquote>Mac, that's a nice suggestion to amplify these effects with chalk. They can then be compared more readily to theoretical predictions.

<blockquote><font class="small">Quote cushioncrawler:</font><hr>The trouble iz that much of the (rolling) masse-effekt iz lost even before the OB haz cleared its own footprint. The chalky-impakt woz strong enuff for the ball to take some masse effekt beyond the footprint.<hr /></blockquote>It's not clear to me why that is the case. For a ball curving on an idealized surface with just one point of contact, it doesn't stop curving until it reaches natural roll. Things are a little different here, as far as the sidespin effect is concerned, but I don't see why it would be that much different, unless maybe the ball was tamped down beforehand. I know that a first "bounce" has more of an effect than subsequent bounces, but having it do most of the curving right at the start seems a little strange. Any thoughts Mac?

<blockquote><font class="small">Quote cushioncrawler:</font><hr>A stun-impakt wouldnt give any masse kurv. But i reckon that there would be a bit of extra throw due to friktion in the leading edge of the OB while bobbling out of its own footprint. This sort of side-wayz (footprint) friktion would exist whenever there woz any throw -- but i guess less so when the qball haz severe backspin at impakt, here the OB would be thrown upish a little, or at least it wouldnt be thrown downish az much az in the rolling impakt.<hr /></blockquote>Yes, I can see that. Also, as you mention below, backspin + throw (one of your "masse veer" effects) works to decrease apparent throw by itself, without any help from the footprint.

<blockquote><font class="small">Quote cushioncrawler:</font><hr>Friktion in the leading edge of the footprint might inkreec the throw (or at least inkreec the apparent early throw), and similar friktion would further inkreec the apparent throw a little later, and this would continue untill this source of friktion evaporated. But then the rezidual sidespin would start to pull-push the OB the "other way", ie diminish the apparent throw, az the OB slowz, and this would continue untill the sidespin fell to zero...<hr /></blockquote>I see the sidespin, to the extent that it is a real effect, always increasing apparent throw, ever so slightly. Why do you think some pull-push develops that reverses the trend?

Jim

Bambu
01-03-2008, 09:13 AM
Bob, I really dont do this to show whats practical and whats not. The spark plug gapper is only to be sure we are all looking at the same shot. Pocket size may matter as well. For the record, my pockets are 5 and 3/8's at the widest point. I'm really not sure why you say the second shot has clearance without the blocking ball interfering. To me, the shot gets easier when you insert the cd. That makes aiming to avoid the blocking ball a bit easier. Another thing the cd does is bring the line of aim away from the pocket, not towards it. So I am unsure why you think the cd makes the shot possible.
If you leave the cd out of the picture, I can still make the shot. I admit, my percentage goes down....but it is makeable.
As for whats practical and whats not, that is a matter of opinion. Throw applies to every cut shot you make, so thats important enough for me. These shots dont depend on cueball/blocker ball distance. It is the distance between the object ball and blocking ball which does matter. Sure its hard to tell exactly how much of the pocket is blocked. But borderline shots appear quite often, thats just the nature of pool in my opinion.
Hitting a distant ball off a rail? Do you mean like in your article? I am willing to try anything you might have, but I did try your shot several times. I also explained why I cant make it. It is the distance between the blocking ball and the object ball which makes it impossible for me.
I only wish to make the point that throw does not occur in a straight line. I am not trying to say that both of those particular shots are "must haves." They are designed to show that if an object ball truly took a straight path, there would be no way to avoid the edge of a blocking ball and still go in.

Bob_Jewett
01-03-2008, 09:36 AM
<blockquote><font class="small">Quote Bambu:</font><hr> ... I only wish to make the point that throw does not occur in a straight line. ... <hr /></blockquote>
And I find that the demos you have provided are not convincing.

What would really be convincing is a demo that actually measured the angle through which the ball turns. That is, that gives an actual number of degrees. That's what Lord Kelvin would want.

dr_dave
01-03-2008, 10:03 AM
<blockquote><font class="small">Quote Bambu:</font><hr>... I'm really not sure why you say the second shot has clearance without the blocking ball interfering. To me, the shot gets easier when you insert the cd. That makes aiming to avoid the blocking ball a bit easier. Another thing the cd does is bring the line of aim away from the pocket, not towards it. So I am unsure why you think the cd makes the shot possible.<hr /></blockquote>A large enough gap (depending on pocket size) makes the shot possible with straight-line "throw" alone. In other words, no "OB swerve" is required if the gap is large enough, and it doens't take much.

<blockquote><font class="small">Quote Bambu:</font><hr>... If you leave the cd out of the picture, I can still make the shot. I admit, my percentage goes down....but it is makeable.<hr /></blockquote>Whether a shot is "practical and useful" or not does depend on the accuracy required and whether or not there are better options (e.g., safety, OB hop shot). I think your original example is "interesting," but I agree with Bob that OB swerve is not "practical or useful," other than as a proposition shot. I can't imagine any top player attempting to use OB swerve in a game situation. (Now, throw and spin transfer are a different story.) I think a safety (or even an OB hop shot) would always be better (higher percentage and lower risk) alternatives to a shot requiring OB swerve.

<blockquote><font class="small">Quote Bambu:</font><hr>... I only wish to make the point that throw does not occur in a straight line.<hr /></blockquote>Technically, this is correct. A small amount of OB swerve is possible. However, for all "practical" purposes, the OB heads very nearly straight in the throw direction after leaving the CB.

I feel like we are starting to beat a dead horse here. Your original example is "interesting" and maybe good as a proposition shot, but to me it proves (as with Bob's article example) that "OB swerve" is a very small effect that is difficult and impractical to use to one's advantage in actual play.

Regards,
Dave

Bambu
01-03-2008, 10:33 AM
I understand what you are saying,Dave. And I agree, the throw effect outweighs the swerve effect. I tend to look at the effect as one reaction, but thats another way to look at it. But if thats really object ball swerve and not throw, how did the object ball get swerve without a downward hit? And even if it is swerve, wouldnt that mean that object balls do not travel in straight lines if there is throw involved?
Perhaps until now I have been trying to prove this from an awkward angle. What I mean by that is, why try to prove that object balls curve? Proving that they dont always travel straight should be easier.
Lets imagine that we stood together at a pool table. You say throw occurs in a straight line, and I disagree. Just a friendly chat amongst pool lovers. I would refer to my earlier example of a throw shot, only this time I would expand on that shot.
http://cuetable.com/P/?@2HATl1IATT2PMMr2vATlhjS@

I would then ask you to take that shot, and observe the curve. Provided you dont see the curve, even at slow speeds, I would then ask you to show me the straight path to the pocket. I would hand you 2 house cues, and ask you to indicate that path. I would allow a 3 inch gap, and I am hoping you might arrange the cues something like this:

http://s212.photobucket.com/albums/cc34/NYCBambu/?action=view&amp;current=Jan08083.jpg

The picture is not perfect, but the line of aim of the frozen balls should point about half way between the pocket and the first diamond. After trying to make the ball in straight without hitting the cues, you would see how hard that is to do.
If I wanted to be more precise about this, I would use 2 chalk lines, one red and one blue. But this time, you only get a 2 and 1/4 inch channel, since thats the size of the balls. The blue line would show the direct path to the pocket, while the red would show where the curve occurs depending on speed. As Bob said, Lord Kelvin would want to see where the ball breaks toward the pocket, and the red chalk line would show this. I will leave the actual number measurement to those who are better qualified to do so, but there would be no way to keep that ball in the straight blue path. Even if you were to adjust the cues or the blue line channel to your liking, you would need to widen the path to allow for the curve. Using pool cues to accomplish this is a crude way of accomplishing the same thing. Having a friend around to see what part of the cue was hit helps alot. I hope that this is a better way to show that throw does not occur in a straight line, and that this is a much easier way to show it. Thanks to everyone for taking the time to hear me out, whether you agree or disagree.

Bambu
01-03-2008, 10:55 AM
I agree with that Dr. Dave, object ball swerve alone is tiny and pretty much not practical for most players. But that is only the tip of the iceberg, because that is the result of what only sidespin alone does to curve an object ball. The big picture is what happens when you introduce larger variables, such as more throw,(which is speed, angle and english dependent). I am willing to forget the example with the cd, but I still cannot accept that throw occurs in a straight line. What reasoning do you use to explain this to an average joe like me?

Bambu
01-03-2008, 11:22 AM
Jal, its that I dont see 2 different things happening. I dont see swerve because there is no downward hit, only spin transfer, and throw. I also dont see the throw angle changing upon impact. Rather, it is developed. Where the curve actually takes place and how much all depends on the shot, but every cut shot involves throw to some extent.
As for the cd, I get less than 1/16 th of an inch, but I will get an exact measurement if you like.

cushioncrawler
01-03-2008, 04:09 PM
<blockquote><font class="small">Quote Jal:</font><hr><blockquote><font class="small">Quote cushioncrawler:</font><hr>The trouble iz that much of the (rolling) masse-effekt iz lost even before the OB haz cleared its own footprint. The chalky-impakt woz strong enuff for the ball to take some masse effekt beyond the footprint.<hr /></blockquote>It's not clear to me why that is the case. For a ball curving on an idealized surface with just one point of contact, it doesn't stop curving until it reaches natural roll. Things are a little different here, as far as the sidespin effect is concerned, but I don't see why it would be that much different, unless maybe the ball was tamped down beforehand. I know that a first "bounce" has more of an effect than subsequent bounces, but having it do most of the curving right at the start seems a little strange. Any thoughts Mac?<hr /></blockquote>Jim, i think that if an OB bounces for say 3" then any kurv (masse kurv for sure, and perhaps other kurv allso) that it might have suffered in that distance would all have happened (angle-wize) while still in its footprint. Likewize for the second bounce (if any). And, for the weak effekts that are being talked about here, 3" iz a lot. madMac.<blockquote><font class="small">Quote cushioncrawler:</font><hr>Friktion in the leading edge of the footprint might inkreec the throw (or at least inkreec the apparent early throw), and similar friktion would further inkreec the apparent throw a little later, and this would continue untill this source of friktion evaporated. But then the rezidual sidespin would start to pull-push the OB the "other way", ie diminish the apparent throw, az the OB slowz, and this would continue untill the sidespin fell to zero...<hr /></blockquote>I see the sidespin, to the extent that it is a real effect, always increasing apparent throw, ever so slightly. Why do you think some pull-push develops that reverses the trend?..<hr /></blockquote>Jim -- The way i see it iz that there are 2 types of sidespin. Initially, while the OB iz still sorting itself out, the sidewayz friktion forces in the leading edge are paramount, hence the OB kurvz and inkreecez the throw angle. This iz especially so in (before) the "first bounce".

Then, when "rolling" iz established, the OB still haz some sidespin. In this phaze the rolling (ie velocity) iz slowing, and the sidewayz friktion forces in the rear of the (temp) footprint bekum paramount, hence we see the kurv the "other" way. This iz for a napless bedcloth, a nappy cloth would do (kood do) stranger thingz.

In fakt, i woz watching some videos of snooker last nite. There woz a telescopik closeup of the green being cut allmost straight towards the camera into a corner pocket. Here the green definitely kurved (early) in its journey, but, this woz a nappy bedcloth, and here some kurv iz allmost certain, due to the sidespin on the nappy cloth. It duznt necessaryly help the arguement for a napless (or at least non-direktional) pool cloth. madMac.

dr_dave
01-03-2008, 04:41 PM
<blockquote><font class="small">Quote Bambu:</font><hr>But if thats really object ball swerve and not throw, how did the object ball get swerve without a downward hit?<hr /></blockquote>You are correct ... a pure stun English shot (with sidespin only, and no roll or draw) should result in absolutely no OB swerve (but it still might "turn" slightly due to other effects per my list below). However, if the CB develops any roll on its way to the OB (e.g., if the CB is not hit below center enough to create stun at impact, after drag), then there will be a small amount of OB swerve; although, as theory suggests, this is a tiny effect.

<blockquote><font class="small">Quote Bambu:</font><hr>And even if it is swerve, wouldnt that mean that object balls do not travel in straight lines if there is throw involved?<hr /></blockquote>There are many things that can cause an OB to not travel in an exact straight line (after it is thrown by the CB). Assuming the table is level and doesn't suffer from roll-off, possible causes are: OB swerve, nap turn, rolling resistance dimple turn, specs of dirt, cloth irregularities, Coriolis force due to rotation of the earth, non-round or out-of-balance balls, etc.). For all practical purposes, under typical playing conditions, I don't think these effects can be used to one's advantage at a pool table.

<blockquote><font class="small">Quote Bambu:</font><hr>Perhaps until now I have been trying to prove this from an awkward angle. What I mean by that is, why try to prove that object balls curve? Proving that they dont always travel straight should be easier.
Lets imagine that we stood together at a pool table. You say throw occurs in a straight line, and I disagree. Just a friendly chat amongst pool lovers. I would refer to my earlier example of a throw shot, only this time I would expand on that shot.
http://cuetable.com/P/?@2HATl1IATT2PMMr2vATlhjS@

I would then ask you to take that shot, and observe the curve. Provided you dont see the curve, even at slow speeds, I would then ask you to show me the straight path to the pocket. I would hand you 2 house cues, and ask you to indicate that path. I would allow a 3 inch gap, and I am hoping you might arrange the cues something like this:

http://s212.photobucket.com/albums/cc34/NYCBambu/?action=view&amp;current=Jan08083.jpg

The picture is not perfect, but the line of aim of the frozen balls should point about half way between the pocket and the first diamond. After trying to make the ball in straight without hitting the cues, you would see how hard that is to do.<hr /></blockquote>That's a good idea. I'll give it a try. I will also try to put together a video showing some of the results of Bob's example and your original example.

Regards,
Dave

dr_dave
01-03-2008, 05:02 PM
<blockquote><font class="small">Quote Bambu:</font><hr> I agree with that Dr. Dave, object ball swerve alone is tiny and pretty much not practical for most players. But that is only the tip of the iceberg, because that is the result of what only sidespin alone does to curve an object ball.<hr /></blockquote>Actually, sidespin does not cause OB swerve. Only masse spin created by a downward or upward hit on the OB can cause "OB swerve."

<blockquote><font class="small">Quote Bambu:</font><hr>The big picture is what happens when you introduce larger variables, such as more throw,(which is speed, angle and english dependent).<hr /></blockquote>Throw can be an extremely important effect, and it can vary with many factors, as my articles (with experimental results) document. Bob has also written many articles over the years about throw and spin transfer. All of my articles and a link to many of Bob's articles can be found here (http://billiards.colostate.edu/bd_articles/index.html).

<blockquote><font class="small">Quote Bambu:</font><hr>I am willing to forget the example with the cd, but I still cannot accept that throw occurs in a straight line. What reasoning do you use to explain this to an average joe like me?<hr /></blockquote>I think I have already explained this in details several times in this thread. "Throw" is created by the friction force between the CB and OB while they are in contact. After the OB leaves the CB, there is no more force from the CB so there can't be any more "throw." I think you are still trying to use a different definition for "throw," but I will continue to use the standard definition. Now, other effects (e.g., "OB swerve," "English turn" due to roll or spin resistance, and other effects I listed in a previous message) can still cause the OB to curve, but I think these effects are too small to be put to practical use on a pool table.

The other reasoning (and illustrations, and examples, and videos) I would use to explain squirt, swerve, throw, and spin transfer can be found in all of my articles on these topics.

Regards,
Dave

Bambu
01-03-2008, 05:12 PM
I apologize Dr. Dave. I could not remember your explanation. Sometimes my head is in a fog over all this. Lately, its all I think about. And I thank you once again, for all your time and for not simply dismissing me as a fool. Your patience is greatly appreciated. I sincerely do not do this to waste anyones time.

Bambu
01-04-2008, 02:13 PM
Thanks again Dave. I look forward to seeing the results.

Jal
01-06-2008, 04:44 PM
<blockquote><font class="small">Quote cushioncrawler:</font><hr> Jim, i think that if an OB bounces for say 3" then any kurv (masse kurv for sure, and perhaps other kurv allso) that it might have suffered in that distance would all have happened (angle-wize) while still in its footprint. Likewize for the second bounce (if any). And, for the weak effekts that are being talked about here, 3" iz a lot. madMac.<hr /></blockquote>I see what you're saying Mac (and agree).

<blockquote><font class="small">Quote cushioncrawler:</font><hr>Jim -- The way i see it iz that there are 2 types of sidespin. Initially, while the OB iz still sorting itself out, the sidewayz friktion forces in the leading edge are paramount, hence the OB kurvz and inkreecez the throw angle. This iz especially so in (before) the "first bounce".

Then, when "rolling" iz established, the OB still haz some sidespin. In this phaze the rolling (ie velocity) iz slowing, and the sidewayz friktion forces in the rear of the (temp) footprint bekum paramount, hence we see the kurv the "other" way. This iz for a napless bedcloth, a nappy cloth would do (kood do) stranger thingz.<hr /></blockquote>Dr. Dave was kind enough to discuss this with me at length - the general issue of sidespin curve. Though he didn't show it, it must have been frustrating for him because I just didn't get what he was saying. He was trying to get me to look at the torque on the ball, and as per his prompting, I have done so. Thanks Dr. Dave!

My assumption that an inclined net normal force necessarily means a larger friction force on the front of the ball than on the back, was dead wrong. I'm sure you realize this too. It could mean then that a ball doesn't curve at all from pure sidespin, or in fact curves the other way. Maybe it's a face saving mind set on my part, but I still tend to think there would be more friction on the leading edge than trailing one. It certainly isn't a given though, and if it is true, for a while, it's not obvious why it would change as the ball slowed down. Any more thoughts on this, Mac?

I also assumed that curving would cease when and if the sidespin component became aligned with the net normal force direction. For the same reasons, this is not necessarily true either.

Taking all of this into consideration, here is a revised version of the graph I linked to earlier:

http://ww2.netnitco.net/users/gtech/OB_Masse3.jpg

Jim

Bambu
01-07-2008, 09:13 AM
Hello Jal,

I was just wondering if you or anyone else had a chance to test for object ball curve, by trying my last throw test with the cues? (Scroll up a bit if you didnt see it.)

dr_dave
01-07-2008, 09:36 AM
<blockquote><font class="small">Quote Bambu:</font><hr> Hello Jal,

I was just wondering if you or anyone else had a chance to test for object ball curve, by trying my last throw test with the cues? (Scroll up a bit if you didnt see it.) <hr /></blockquote>I shot some video and did some experiments and analysis over the weekend. I hope to have it all ready to post later today. Bottom line: I didn't observe any significant or consistent OB swerve or OB turn. My tests show the OB being thrown in a straight line.

Regards,
Dave

Jal
01-07-2008, 12:39 PM
<blockquote><font class="small">Quote Bambu:</font><hr> Hello Jal,

I was just wondering if you or anyone else had a chance to test for object ball curve, by trying my last throw test with the cues? (Scroll up a bit if you didnt see it.) <hr /></blockquote>Sorry Bambu, not yet. I did look at your latest version, but have one in mind that I think would actually measure the amount of curve, if any, with some degree of accuracy. But first, it'll be interesting to see what Dr. Dave did and whether this other test might show anything his didn't.

Jim

Bambu
01-07-2008, 03:46 PM
Ah, thanks anyway Jal. Wow, a measurable test would be great. I look forward to seeing that, as well as Daves results.

Bambu
01-07-2008, 03:47 PM
Hmmm, thanks Dave. I do look forward to seeing your results.

dr_dave
01-07-2008, 05:32 PM
<blockquote><font class="small">Quote Bambu:</font><hr> Ah, thanks anyway Jal. Wow, a measurable test would be great. I look forward to seeing that, as well as Daves results.<hr /></blockquote>I decided to post the videos in a fresh thread so we can begin a new discussion with concrete definitions and demonstrations. Here's the new thread (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&amp;Board=ccb&amp;Number=270330&amp;page =0&amp;view=collapsed&amp;sb=5&amp;o=&amp;fpart=1). I also did some experiments and physics to back up some of the claims, but it will take me a while to write it up and post it.

Regards,
Dave

dr_dave
01-07-2008, 06:02 PM
I tried this shot many times, varying aim, speed, and amount of English. When the shot was set up very carefully (i.e., all balls frozen to each other and to the rail cushion perfectly), I was not able to convert the shot. Now, if there was even a tiny gap between the 5-ball and the cushion and/or between the 3-ball and 5-ball, the shot was easy with "throw" alone. However, I was apparently not able to create "OB turn." Maybe "OB turn" is easier on some cloths under certain conditions. It isn't easy (or even possible consistently) on mine.

Sorry,
Dave

PS: BTW, to achieve maximum throw and spin transfer, 50% English is better than maximum English (see my December '06 article (http://billiards.colostate.edu/bd_articles/2006/dec06.pdf), my March '07 article (http://billiards.colostate.edu/bd_articles/2007/mach07.pdf), and NV A.21 - Bank shot using throw and spin transfer (http://billiards.colostate.edu/normal_videos/new/NVA-21.htm)).

<blockquote><font class="small">Quote Bambu:</font><hr> http://CueTable.com/P/?@2CXVo2DbHU2EbHn2FbIH2GbIa3Ibbh2PXWa2qQtF&amp;ZZ2vXWa hoa@

After setting this up, remove the 5,6 and 7 balls. Feel free to try making the 9 first using no English, and to also check for table roll. Then try using extreme 9:00 left English to impart right spin to the 3 ball. the spin transfers initially opposite, but then the object ball takes on more of a forward roll, combined with the right spin. When done at just the right speed and with enough english, you can transfer enough spin to that 3 ball to make it curve towards the pocket. Not super slow, maybe a 2-3 out of 10. Line of aim is to just barely not hit the 4. The 3 will go straight for 1-2 balls lengths before curving towards the pocket, if you get it right. The curve is nowhere near enough to sink the 9 ball in Bobs shot, but in this case, if you can manage to get it, that quarter inch helps.
This is a tough shot, but certainly make able. Part of what makes these types of shots so tough, is that you need cue speed to get the spin, but at the same time a soft hit is required to curve the object ball towards the pocket. It is the right combination of the 2 which will sink the ball. You want as much spin as you can get, while still keeping the speed at maybe 2+ out of 10 AND getting the line of aim perfect. Too hard and you will not allow the spin to grab the cloth and take the slight turn.
If this were a game of say, ring game 9 ball, where a safety doesnt do you much good, this would be the choice for me. Even in regular 9 ball, you could lose to a good kick(depending on how good a safety you can pull off). Even if you manage to freeze your cueball perfectly on the 4, the short rail could be used to kick at the 3. <hr /></blockquote>

Bambu
01-09-2008, 01:11 AM
Personally, I think its just a really hard shot. I dont think the cloth has much to do with it, but thanks for trying anyway. I do appreciate it.

dr_dave
01-14-2008, 01:45 PM
<blockquote><font class="small">Quote Jal:</font><hr>Dr. Dave was kind enough to discuss this with me at length - the general issue of sidespin curve. Though he didn't show it, it must have been frustrating for him because I just didn't get what he was saying. He was trying to get me to look at the torque on the ball, and as per his prompting, I have done so. Thanks Dr. Dave!

My assumption that an inclined net normal force necessarily means a larger friction force on the front of the ball than on the back, was dead wrong. I'm sure you realize this too. It could mean then that a ball doesn't curve at all from pure sidespin, or in fact curves the other way. Maybe it's a face saving mind set on my part, but I still tend to think there would be more friction on the leading edge than trailing one.<hr /></blockquote>Jal,

I have an analysis posted in TP B.2 (http://billiards.colostate.edu/technical_proofs/new/TP_B-2.pdf). I hope you, Mac, and others might look at it and comment on whether or not you agree with the assumptions and approach. I think the results are reasonable; although, the numbers are a little larger than I expected based on observations (e.g., NV B.7 (http://billiards.colostate.edu/normal_videos/new/NVB-7.htm)).

Thank you for all of your help this last week looking at my original analysis draft and helping to convince me that I was going down the wrong path.

Regards,
Dave

cushioncrawler
01-16-2008, 05:45 AM
<blockquote><font class="small">Quote Jal:</font><hr>....My assumption that an inclined net normal force necessarily means a larger friction force on the front of the ball than on the back, was dead wrong. I'm sure you realize this too. It could mean then that a ball doesn't curve at all from pure sidespin, or in fact curves the other way. Maybe it's a face saving mind set on my part, but I still tend to think there would be more friction on the leading edge than trailing one. It certainly isn't a given though, and if it is true, for a while, it's not obvious why it would change as the ball slowed down. Any more thoughts on this, Mac?

I also assumed that curving would cease when and if the sidespin component became aligned with the net normal force direction. For the same reasons, this is not necessarily true either.....<hr /></blockquote>Jim -- I reckon that the spin axis findz the angle (or tryz to find the angle) wherebye the leftwards and rightwards (out of balance) forces bekum balanced. It might never actually acheev it (balance), but it tryz.

Az the ball slowz, the pressures (supporting the ball) must change, ie in the varyus parts of the footprint. And, the areas themselves must change (ie the overall dia and depth of the footprint). And, the friktional coefficients must change (with skid-speed etc) in theze areas (spin-skid here).

I have trouble thinking about this. Az a ball slowz, the rear area of the footprint kood be imagined to grow in area, and pressure. On the other hand, az the ball slowz, it presses the nap down more, ie it irons the nap better, if so then the rear pressure (and area) gets weaker (and smaller). Its difficult to think about.

Re friction being greater in the leading edge, this factoid could allmost be uzed to support reverse-kurv, koz surely this greater friction could be said to reduce much more greatly (exponentially or something) during slowing than duz the lesser friction in the trailing edge?? (If u see what i mean). madMac.

cushioncrawler
01-16-2008, 06:00 AM
<blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote Jal:</font><hr>Dr. Dave was kind enough to discuss this with me at length - the general issue of sidespin curve. Though he didn't show it, it must have been frustrating for him because I just didn't get what he was saying. He was trying to get me to look at the torque on the ball, and as per his prompting, I have done so. Thanks Dr. Dave!

My assumption that an inclined net normal force necessarily means a larger friction force on the front of the ball than on the back, was dead wrong. I'm sure you realize this too. It could mean then that a ball doesn't curve at all from pure sidespin, or in fact curves the other way. Maybe it's a face saving mind set on my part, but I still tend to think there would be more friction on the leading edge than trailing one.<hr /></blockquote>Jal,

I have an analysis posted in TP B.2 (http://billiards.colostate.edu/technical_proofs/new/TP_B-2.pdf). I hope you, Mac, and others might look at it and comment on whether or not you agree with the assumptions and approach. I think the results are reasonable; although, the numbers are a little larger than I expected based on observations (e.g., NV B.7 (http://billiards.colostate.edu/normal_videos/new/NVB-7.htm)).

Thank you for all of your help this last week looking at my original analysis draft and helping to convince me that I was going down the wrong path. Regards, Dave<hr /></blockquote>Dr Dave -- I think that one problem with spinkurv iz that it might total a few inches in many seconds (from friktion etc indirecktly mostly), compared to skid-deceleration and masse-kurv (from direkt friktion) which might total many inches in a split second. So, any little old subtle effekt can do the trick (ie affekt spin-kurv). In fakt, for a directionally napped cloth, i have identifyed at least 10 effekts -- some of theze are possibly very strong, but they are all mostly fighting each other. And, thinking about it just now, i karnt see why every one of the 10 shoodnt have at least a small effekt on a pool cloth having a non-direktional nap (but most of theze 10 wouldnt exist if a cloth had zero nap). madMac.

dr_dave
01-16-2008, 10:39 AM
<blockquote><font class="small">Quote cushioncrawler:</font><hr> <blockquote><font class="small">Quote Jal:</font><hr>....My assumption that an inclined net normal force necessarily means a larger friction force on the front of the ball than on the back, was dead wrong...<hr /></blockquote>...Re friction being greater in the leading edge, this factoid could allmost be uzed to support reverse-kurv, koz surely this greater friction could be said to reduce much more greatly (exponentially or something) during slowing than duz the lesser friction in the trailing edge?? (If u see what i mean).<hr /></blockquote>If the leading friction force is greater than the trailing friction force, the ball must turn in the natural (not reverse) direction (e.g., right curve for right spin). If the leading edge force is greater, even if it is decreasing, the ball will still continue to turn in that direction (unless it decreases lower than the trailing edge force).

The force Ft in the second diagram in TP B.2 (http://billiards.colostate.edu/technical_proofs/new/TP_B-2.pdf) is the resultant of the leading and trailing edge friction forces. The direction is consistent with natural turn implying the friction force is greater on the leading edge. The analysis shows that the torque, friction, and turn directions are all consistent.

Regards,
Dave

cushioncrawler
01-17-2008, 05:07 AM
<blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote cushioncrawler:</font><hr> <blockquote><font class="small">Quote Jal:</font><hr>....My assumption that an inclined net normal force necessarily means a larger friction force on the front of the ball than on the back, was dead wrong...<hr /></blockquote>...Re friction being greater in the leading edge, this factoid could allmost be uzed to support reverse-kurv, koz surely this greater friction could be said to reduce much more greatly (exponentially or something) during slowing than duz the lesser friction in the trailing edge?? (If u see what i mean).<hr /></blockquote>If the leading friction force is greater than the trailing friction force, the ball must turn in the natural (not reverse) direction (e.g., right curve for right spin). If the leading edge force is greater, even if it is decreasing, the ball will still continue to turn in that direction (unless it decreases lower than the trailing edge force).

The force Ft in the second diagram in TP B.2 (http://billiards.colostate.edu/technical_proofs/new/TP_B-2.pdf) is the resultant of the leading and trailing edge friction forces. The direction is consistent with natural turn implying the friction force is greater on the leading edge. The analysis shows that the torque, friction, and turn directions are all consistent. Regards, Dave<hr /></blockquote>Dr Dave -- All forces, no matter what they are, sort themselves out during the skidding phaze. Then, we have (allmost have) equilibrium. Then (in the rolling phaze) it iz a new ball game. If the giant sized forces in the leading edge diminish very quickly, and if the itsy bitsy teen weeny little forces in the trailing edge diminish not so quickly, then we have "revers kurv". madMac.

dr_dave
01-17-2008, 10:31 AM
<blockquote><font class="small">Quote cushioncrawler:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote cushioncrawler:</font><hr> <blockquote><font class="small">Quote Jal:</font><hr>....My assumption that an inclined net normal force necessarily means a larger friction force on the front of the ball than on the back, was dead wrong...<hr /></blockquote>...Re friction being greater in the leading edge, this factoid could allmost be uzed to support reverse-kurv, koz surely this greater friction could be said to reduce much more greatly (exponentially or something) during slowing than duz the lesser friction in the trailing edge?? (If u see what i mean).<hr /></blockquote>If the leading friction force is greater than the trailing friction force, the ball must turn in the natural (not reverse) direction (e.g., right curve for right spin). If the leading edge force is greater, even if it is decreasing, the ball will still continue to turn in that direction (unless it decreases lower than the trailing edge force).

The force Ft in the second diagram in TP B.2 (http://billiards.colostate.edu/technical_proofs/new/TP_B-2.pdf) is the resultant of the leading and trailing edge friction forces. The direction is consistent with natural turn implying the friction force is greater on the leading edge. The analysis shows that the torque, friction, and turn directions are all consistent. Regards, Dave<hr /></blockquote>Dr Dave -- All forces, no matter what they are, sort themselves out during the skidding phaze.<hr /></blockquote>My analysis doesn't concern the skidding phase, only the rolling phase. The question at hand is: when a ball is rolling (not skidding) with sidespin, are there forces that tend to make the ball curve. TP B.2 (http://billiards.colostate.edu/technical_proofs/new/TP_B-2.pdf) suggest there might be a small force, and NV B.7 (http://billiards.colostate.edu/normal_videos/new/NVB-7.htm) demonstrates how small and insignificant the effect is.

<blockquote><font class="small">Quote cushioncrawler:</font><hr>Then, we have (allmost have) equilibrium. Then (in the rolling phaze) it iz a new ball game. If the giant sized forces in the leading edge diminish very quickly, and if the itsy bitsy teen weeny little forces in the trailing edge diminish not so quickly, then we have "revers kurv". madMac.<hr /></blockquote>My "equilibrium" analysis makes a case for natural (not reverse) curve. Do you see any flaws in the logic or approach in TP B.2 (http://billiards.colostate.edu/technical_proofs/new/TP_B-2.pdf)?

Regards,
Dave

Bambu
01-19-2008, 07:54 AM
Is it possible that mac means reverse, as in opposite english? Just a hunch. (Left english transfers right spin.)

dr_dave
01-20-2008, 01:34 PM
<blockquote><font class="small">Quote Bambu:</font><hr> Is it possible that mac means reverse, as in opposite english? Just a hunch. (Left english transfers right spin.)<hr /></blockquote>I don't think so. He claims the trailing edge forces might be larger creating "revers kurv." By "reverse" I think he means in the opposite direction you would expect if the forces were greater on the leading edge, but only Mac can say.

Regards,
Dave

dr_dave
01-20-2008, 01:37 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote Bambu:</font><hr> Is it possible that mac means reverse, as in opposite english? Just a hunch. (Left english transfers right spin.)<hr /></blockquote>I don't think so. He claims the trailing edge forces might be larger creating "revers kurv." By "reverse" I think he means in the opposite direction you would expect if the forces were greater on the leading edge, but only Mac can say.<hr /></blockquote>The fact that we can't even seem to agree on which way the ball might curve says a lot about the unimportance of this effect (IMO).

Regards,
Dave

cushioncrawler
01-22-2008, 04:59 AM
<blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote Bambu:</font><hr> Is it possible that mac means reverse, as in opposite english? Just a hunch. (Left english transfers right spin.)<hr /></blockquote>I don't think so. He claims the trailing edge forces might be larger creating "revers kurv." By "reverse" I think he means in the opposite direction you would expect if the forces were greater on the leading edge, but only Mac can say. Regards,
Dave<hr /></blockquote>Dr Dave/Bambu -- Yes by reverse kurv i mean that a ball with clockwize (left) spin kurves right (not left). madMac.

cushioncrawler
01-22-2008, 05:15 AM
<blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote cushioncrawler:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote cushioncrawler:</font><hr> <blockquote><font class="small">Quote Jal:</font><hr>....My assumption that an inclined net normal force necessarily means a larger friction force on the front of the ball than on the back, was dead wrong...<hr /></blockquote>...Re friction being greater in the leading edge, this factoid could allmost be uzed to support reverse-kurv, koz surely this greater friction could be said to reduce much more greatly (exponentially or something) during slowing than duz the lesser friction in the trailing edge?? (If u see what i mean).<hr /></blockquote>If the leading friction force is greater than the trailing friction force, the ball must turn in the natural (not reverse) direction (e.g., right curve for right spin). If the leading edge force is greater, even if it is decreasing, the ball will still continue to turn in that direction (unless it decreases lower than the trailing edge force).

The force Ft in the second diagram in TP B.2 (http://billiards.colostate.edu/technical_proofs/new/TP_B-2.pdf) is the resultant of the leading and trailing edge friction forces. The direction is consistent with natural turn implying the friction force is greater on the leading edge. The analysis shows that the torque, friction, and turn directions are all consistent. Regards, Dave<hr /></blockquote>Dr Dave -- All forces, no matter what they are, sort themselves out during the skidding phaze.<hr /></blockquote>My analysis doesn't concern the skidding phase, only the rolling phase. The question at hand is: when a ball is rolling (not skidding) with sidespin, are there forces that tend to make the ball curve. TP B.2 (http://billiards.colostate.edu/technical_proofs/new/TP_B-2.pdf) suggest there might be a small force, and NV B.7 (http://billiards.colostate.edu/normal_videos/new/NVB-7.htm) demonstrates how small and insignificant the effect is.

<blockquote><font class="small">Quote cushioncrawler:</font><hr>Then, we have (allmost have) equilibrium. Then (in the rolling phaze) it iz a new ball game. If the giant sized forces in the leading edge diminish very quickly, and if the itsy bitsy teen weeny little forces in the trailing edge diminish not so quickly, then we have "revers kurv". madMac.<hr /></blockquote>My "equilibrium" analysis makes a case for natural (not reverse) curve. Do you see any flaws in the logic or approach in TP B.2 (http://billiards.colostate.edu/technical_proofs/new/TP_B-2.pdf)? Regards, Dave<hr /></blockquote>Dr Dave -- I think that Jim covered my thorts more or less in the other (related) thread. Assuming that the spin axis etc findz some sort of equilibrium at the end of skidding, then all of the torques (and forcez) in the footprint will be related to their dispozition etc relativ to the spin axis (at that instant) and wont be related much to the grade of the hill nor to the effektiv supporting force etc. More than that, whether the supporting force(s) and mu(s) and frictional force(s) and the area(s) and torq-arm(s) of the varyus bits of the footprint get bigger or smaller depends on ??? and iz/are a big unknown. madMac.

Bambu
01-22-2008, 11:00 AM
Forgive me Dave, but this reminds me of a favorite quote of mine. In the immortal words of the great Oscar Gamble(1977 NY Yankees):

"They dont think it be like it is, but it do."

dr_dave
01-22-2008, 03:01 PM
<blockquote><font class="small">Quote cushioncrawler:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote cushioncrawler:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote cushioncrawler:</font><hr> <blockquote><font class="small">Quote Jal:</font><hr>....My assumption that an inclined net normal force necessarily means a larger friction force on the front of the ball than on the back, was dead wrong...<hr /></blockquote>...Re friction being greater in the leading edge, this factoid could allmost be uzed to support reverse-kurv, koz surely this greater friction could be said to reduce much more greatly (exponentially or something) during slowing than duz the lesser friction in the trailing edge?? (If u see what i mean).<hr /></blockquote>If the leading friction force is greater than the trailing friction force, the ball must turn in the natural (not reverse) direction (e.g., right curve for right spin). If the leading edge force is greater, even if it is decreasing, the ball will still continue to turn in that direction (unless it decreases lower than the trailing edge force).

The force Ft in the second diagram in TP B.2 (http://billiards.colostate.edu/technical_proofs/new/TP_B-2.pdf) is the resultant of the leading and trailing edge friction forces. The direction is consistent with natural turn implying the friction force is greater on the leading edge. The analysis shows that the torque, friction, and turn directions are all consistent. Regards, Dave<hr /></blockquote>Dr Dave -- All forces, no matter what they are, sort themselves out during the skidding phaze.<hr /></blockquote>My analysis doesn't concern the skidding phase, only the rolling phase. The question at hand is: when a ball is rolling (not skidding) with sidespin, are there forces that tend to make the ball curve. TP B.2 (http://billiards.colostate.edu/technical_proofs/new/TP_B-2.pdf) suggest there might be a small force, and NV B.7 (http://billiards.colostate.edu/normal_videos/new/NVB-7.htm) demonstrates how small and insignificant the effect is.

<blockquote><font class="small">Quote cushioncrawler:</font><hr>Then, we have (allmost have) equilibrium. Then (in the rolling phaze) it iz a new ball game. If the giant sized forces in the leading edge diminish very quickly, and if the itsy bitsy teen weeny little forces in the trailing edge diminish not so quickly, then we have "revers kurv". madMac.<hr /></blockquote>My "equilibrium" analysis makes a case for natural (not reverse) curve. Do you see any flaws in the logic or approach in TP B.2 (http://billiards.colostate.edu/technical_proofs/new/TP_B-2.pdf)? Regards, Dave<hr /></blockquote>Dr Dave -- I think that Jim covered my thorts more or less in the other (related) thread. Assuming that the spin axis etc findz some sort of equilibrium at the end of skidding, then all of the torques (and forcez) in the footprint will be related to their dispozition etc relativ to the spin axis (at that instant) and wont be related much to the grade of the hill nor to the effektiv supporting force etc. More than that, whether the supporting force(s) and mu(s) and frictional force(s) and the area(s) and torq-arm(s) of the varyus bits of the footprint get bigger or smaller depends on ??? and iz/are a big unknown. madMac. <hr /></blockquote>Lot's to think about. I'll take one more stab at an improved analysis, but I think you and Jal might be right that it might be impossible to conclusively predict curve in one direction or the other. Maybe we should just go back to saying: "a rolling ball with English goes straight for all practical purposes" per NV B.7 - Ball "turn" caused by sidespin (http://billiards.colostate.edu/normal_videos/new/NVB-7.htm) and NV B.8 - Straight throw of a second object ball (http://billiards.colostate.edu/normal_videos/new/NVB-8.htm).

Regards,
Dave

Bambu
01-22-2008, 07:58 PM
I agree the effect is not very important. But, I dont see how any curve other than one in the direction of the spin would be possible at all(short of table roll). For a ball to curve it must be within a perfect range and combination of spin axes, rpm's, speed, and cloth sensitivity. When curve does occur, a ball has no choice but to curve in the direction of the english(IMO).

dr_dave
01-23-2008, 09:38 AM
<blockquote><font class="small">Quote Bambu:</font><hr> I agree the effect is not very important. But, I dont see how any curve other than one in the direction of the spin would be possible at all(short of table roll). For a ball to curve it must be within a perfect range and combination of spin axes, rpm's, speed, and cloth sensitivity. When curve does occur, a ball has no choice but to curve in the direction of the english(IMO).<hr /></blockquote>Intuitively, I agree with you, per my description in NV B.7 (http://billiards.colostate.edu/normal_videos/new/NVB-7.htm); but the physics is complicated and subtle, making intuition difficult.

Dave

Bambu
01-24-2008, 03:31 PM
Perhaps the only way to really know for sure would be to run multiple tests using high speed/quality, ultra violet, slow motion video. Or, something like this:

http://www.bskunion.at/efler/Faszination_Dreiband_Windows_Media_9.wmv

Deeman3
01-24-2008, 03:54 PM
Nice video!