PDA

View Full Version : bank shot using throw and spin transfer



dr_dave
01-05-2007, 12:39 PM
I finally got around to shooting a video demo in response to spin transfer debate in a previous thread (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&Board=ccb&Number=239980&page =0&view=collapsed&sb=5&o=&fpart=&vc=). The video shows an example bank shot that could not be made without throw and spin transfer effects. It can be found at NV A.21 (http://www.engr.colostate.edu/~dga/pool/normal_videos/new/NVA-21.htm).

Please let me know if you have any comments or suggestions, because my next BD instructional article will feature this example.

Thanks,
Dave

dr_dave
01-05-2007, 12:57 PM
For the non-believers out there, I now have several resources available to prove that spin transfer exists. HSV A.66 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/new/HSVA-66.htm) provides a high-speed video demonstration of the effect. NV A.21 (http://www.engr.colostate.edu/~dga/pool/normal_videos/new/NVA-21.htm) provides a demonstration of a bank shot not possible without spin transfer. And for the physics nerds out there, TP A.27 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/new/TP_A-27.pdf) provides a mathematical proof.

If the non-believers in the congregation are still skeptical, the only thing else I can do is ask you to just have faith. Spin transfer does exist, and it can affect pool shots.

Knowledge is power,
Dave

Bob_Jewett
01-05-2007, 01:00 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> ... The video shows an example bank shot that could not be made without throw and spin transfer effects. ... <hr /></blockquote>
I believe you, but the nit-pickers will say that you made the bank not because of throw and transferred spin, but rather because you masse'd the cue ball a little to get the right hit on the object ball. Or maybe you had more clearance by the blocking ball than it appears on the video, which, after all, you set up.

It is not so easy to construct examples that the nit-pickers cannot pick on. I think I have two of them, which I plan to put in my next article in BD which will be about "transferred side spin." I'll post a pointer when I have the diagrams done.

dr_dave
01-05-2007, 01:11 PM
<blockquote><font class="small">Quote Bob_Jewett:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> ... The video shows an example bank shot that could not be made without throw and spin transfer effects. ... <hr /></blockquote>
I believe you, but the nit-pickers will say that you made the bank not because of throw and transferred spin, but rather because you masse'd the cue ball a little to get the right hit on the object ball. Or maybe you had more clearance by the blocking ball than it appears on the video, which, after all, you set up.<hr /></blockquote>
That's why I included several different cases in the video (http://www.engr.colostate.edu/~dga/pool/normal_videos/new/NVA-21.htm). The motion (or lack of motion) of the cue ball clearly demonstrates whether or not swerve is a contributing effect. Do you agree?

<blockquote><font class="small">Quote Bob_Jewett:</font><hr>It is not so easy to construct examples that the nit-pickers cannot pick on. I think I have two of them, which I plan to put in my next article in BD which will be about "transferred side spin." I'll post a pointer when I have the diagrams done.<hr /></blockquote>
I look forward to seeing your article and examples. I'm also almost done with my spin transfer article. It looks like the March issue of BD will not be lacking in spin transfer coverage. If you want to somehow collaborate on the articles, let me know. I hope to post my draft by the end of the day.

Regards,
Dave

SpiderMan
01-05-2007, 03:04 PM
HSV A.66 is all the visual evidence anyone should need to see that spin is transferred. Scott, did you view this one?

BTW, Dave - HSV 7.5 looks a lot like a foul. Has this been questioned before?

SpiderMan

dr_dave
01-05-2007, 03:14 PM
<blockquote><font class="small">Quote SpiderMan:</font><hr> HSV A.66 is all the visual evidence anyone should need to see that spin is transferred.<hr /></blockquote>
I agree, but I thought the non-believers might want the additional evidence.

Thanks,
Dave

dr_dave
01-05-2007, 03:18 PM
<blockquote><font class="small">Quote SpiderMan:</font><hr>Dave - HSV 7.5 looks a lot like a foul. Has this been questioned before?<hr /></blockquote>
I don't think HSV 7.5 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/HSV7-5.htm) looks like a foul, but I guess that depends on your definition of "foul." The cue ball is frozen to the object ball, so you are allowed (by the rules I know) to stroke through the ball, even though the cue ball is pushed in the process. Why do you think the shot is a foul?

Dave

Bob_Jewett
01-05-2007, 04:55 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote SpiderMan:</font><hr>Dave - HSV 7.5 looks a lot like a foul. Has this been questioned before?<hr /></blockquote>
I don't think HSV 7.5 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/HSV7-5.htm) looks like a foul, but I guess that depends on your definition of "foul." The cue ball is frozen to the object ball, so you are allowed (by the rules I know) to stroke through the ball, even though the cue ball is pushed in the process. Why do you think the shot is a foul?

Dave <hr /></blockquote>
If the balls are frozen, the path of the cue ball can be predicted fairly well by the "two-times-fuller" system, even with side spin. (For those not familiar with it, this is a system for figuring out the path of the cue ball when it is shot into a ball it is frozen to. It is explained in Byrne's "Standard" book, and almost explained in Ray Martin's "99 Critical Shots" book.) The cue ball does not follow that path. I conclude that either the balls weren't frozen or there was a miscue.

cushioncrawler
01-05-2007, 04:59 PM
Looks very good, i agree with the wordage. My comments....

1... I think that anyone thinking that masse haz helped here would be satisfyd with at least the shot where the qball stays on-line, ie the qball duznt follow throo to the blocking-ball side of the impact line.

2... Why not add a few shots replacing the blocking-ball with a bit of straight heavy lumber with the qball and OB leaning against the lumber. This would satisfy anyone worrying about the blocking-ball intentionally or unintentionally showing a bit of daylight to the qball, and it would appease the anti-masse crowd allso.

3... Regarding getting the max angle at pocket speed, i think that another factor helping the angle here iz that "e" for a cushion would be higher at higher speeds, hence Va/Vr would be smaller at slow speed, whereaz Vxx/Vr wouldnt be affected, hence Vxx/Va would be larger. (a) is attack, (r) is rebound, (xx) is parallel to cushion.

4... That transfer of sidespin video iz impressive, but whenever i see this sort of close-up footage of balltoball impact i allwayz look for evidence of 3% to 4% stunthroo speed by the qball, and a bit later of course even more followthroo speed or screwback depending on how much topspin or bottomspin the qball haz after impact. But in this footage there iz very little stunthroo, perhaps say 2%, i wonder if the 2 balls have a balltoball impact "e" of 0.95 or something, ie higher than the 0.90 that we find for "real" balls.

5... Just occurred to me -- re the transfer of spin video -- if the impact woz dead online, then the OB should be going a bit offline to the right besides having rhs, and the qball should initially be going left at the same xx speed as the OB. But, without looking at the video to check, i think that the qball "stayed put" -- if so, then this would imply a bit or a lot of offcenter impact, which wouldnt disqualify the rezults, but would bring into play a bit of impact-induced side, or whatever Marlow or Koehler or Byrne or someone else called it. If so, then the sidespin has a bit of tranzmitted side and induced side, this mixture iz what i have lately been calling "Tranzduced Spin", a new term i think (but no copyright). madMac.

cushioncrawler
01-05-2007, 05:25 PM
<blockquote><font class="small">Quote Dr_Dave:</font><hr> Jim, Your numbers sounded a little high to me, so I also worked through the math and physics. The details can be found in TP A.27. I come up with a typical maximum possible spin transfer percentage of about 25%. This is lower than your numbers; however, it is still significant (e.g., enough to affect bank shots dramatically). Regards, Dave <hr /></blockquote>
Dr Dave -- I carried this snippet over from the last page of the earlyr thread. I would have thort that for a full-ball impact a qball couldnt transfer more than 50% of its sidespin, or, allowing for balltoball sliding friction energy (spin) losses of 2/7ths, say 5/7ths of 50%, which iz 35.7%, ie 5/14ths (but i havnt given this much thort here, alltho i have lost a lot of sleep over this stuff in years gone bye).

6... Which remindz me, in my previous posting, i could have added that it might be worthwhile to play at least one shot uzing zero side, ie fullball, ie the OB shood come straight back at nearnuff 90dg if u just-miss the blocking-ball. madMac.

Bob_Jewett
01-05-2007, 06:20 PM
<blockquote><font class="small">Quote cushioncrawler:</font><hr> ... whenever i see this sort of close-up footage of balltoball impact i allwayz look for evidence of 3% to 4% stunthroo speed by the qball, and a bit later of course even more followthroo speed or screwback depending on how much topspin or bottomspin the qball haz after impact. But in this footage there iz very little stunthroo, perhaps say 2%, i wonder if the 2 balls have a balltoball impact "e" of 0.95 or something, ie higher than the 0.90 that we find for "real" balls.... <hr /></blockquote>
The balls shown are not cast phenolic. Polycarbonate, maybe? But are Aramith balls really as low as .9?

cushioncrawler
01-05-2007, 07:09 PM
<blockquote><font class="small">Quote Bob_Jewett:</font><hr> .... The balls shown are not cast phenolic. Polycarbonate, maybe? But are Aramith balls really as low as .9? <hr /></blockquote>
Hi Bob -- My tests show that 2-1/16" Aramiths (english billiard set of 3 in box, white red yellow) are 0.935 at 1.7m/s balltoball impact, 0.914 at 3.3m/s, and 0.897 at 5.4m/s.

At 5.4m/s i got -- Ivory 0.782 ( old cracked 2" balls here), bonzoline 0.823 (cellulose they say), crystalate 0.849 (cellulose plus crushed ox shin bone they say), newish model of supercrystalates 0.895 (polyester), Aramith 0.897 (bakelite), oldish model of supercrystalates 0.909 (polyester), BBA 0.940 (melamine).

So, at slow pace, probably like in the tranzmitted side video (??), a bakelite ball (aramith) might have an e of allmost 0.95. And some sort of ball like a BBA might (at slow speed) have an e of 0.97 say (this might give stunthroo of say 1.5%, not sure, havnt done the calcs). madMac.

dr_dave
01-06-2007, 07:42 AM
<blockquote><font class="small">Quote Bob_Jewett:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote SpiderMan:</font><hr>Dave - HSV 7.5 looks a lot like a foul. Has this been questioned before?<hr /></blockquote>
I don't think HSV 7.5 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/HSV7-5.htm) looks like a foul, but I guess that depends on your definition of "foul." The cue ball is frozen to the object ball, so you are allowed (by the rules I know) to stroke through the ball, even though the cue ball is pushed in the process. Why do you think the shot is a foul?

Dave <hr /></blockquote>
If the balls are frozen, the path of the cue ball can be predicted fairly well by the "two-times-fuller" system, even with side spin. (For those not familiar with it, this is a system for figuring out the path of the cue ball when it is shot into a ball it is frozen to. It is explained in Byrne's "Standard" book, and almost explained in Ray Martin's "99 Critical Shots" book.) The cue ball does not follow that path. I conclude that either the balls weren't frozen or there was a miscue. <hr /></blockquote>
Agreed. The question still remains: Is the shot a foul? What do you think?

Dave

dr_dave
01-06-2007, 07:49 AM
<blockquote><font class="small">Quote cushioncrawler:</font><hr>I think that anyone thinking that masse haz helped here would be satisfyd with at least the shot where the qball stays on-line, ie the qball duznt follow throo to the blocking-ball side of the impact line.<hr /></blockquote>Agreed!

<blockquote><font class="small">Quote cushioncrawler:</font><hr>Why not add a few shots replacing the blocking-ball with a bit of straight heavy lumber with the qball and OB leaning against the lumber. This would satisfy anyone worrying about the blocking-ball intentionally or unintentionally showing a bit of daylight to the qball, and it would appease the anti-masse crowd allso.<hr /></blockquote>That's a great idea. If the nay-sayers come out in force, I'll pull out the wood.

Thank you for your comments,
Dave

dr_dave
01-06-2007, 07:52 AM
<blockquote><font class="small">Quote cushioncrawler:</font><hr>in my previous posting, i could have added that it might be worthwhile to play at least one shot uzing zero side, ie fullball, ie the OB shood come straight back at nearnuff 90dg if u just-miss the blocking-ball.<hr /></blockquote>That's a great idea. If I decide to re-shoot the video, I will most certainly do this. That would help show that I wasn't cheating with the ball setup, and that the table is level. BTW, I wasn't cheating, and the table was level.

Regards,
Dave

SpiderMan
01-06-2007, 01:42 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote SpiderMan:</font><hr>Dave - HSV 7.5 looks a lot like a foul. Has this been questioned before?<hr /></blockquote>
I don't think HSV 7.5 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/HSV7-5.htm) looks like a foul, but I guess that depends on your definition of "foul." The cue ball is frozen to the object ball, so you are allowed (by the rules I know) to stroke through the ball, even though the cue ball is pushed in the process. Why do you think the shot is a foul?

Dave <hr /></blockquote>

I think that the tip must have made a second contact. Perhaps not all miscues are fouls, but this one appears to be.

SpiderMan

SpiderMan
01-06-2007, 01:45 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote SpiderMan:</font><hr> HSV A.66 is all the visual evidence anyone should need to see that spin is transferred.<hr /></blockquote>
I agree, but I thought the non-believers might want the additional evidence.

Thanks,
Dave <hr /></blockquote>

Pretty solid evidence - the object ball is clearly turning after contact. I like this much better than the bank shot, which requires the skeptic to deduce that spin must have transferred, as opposed to seeing it directly.

I was never able to capture that to my satisfaction using my regular camcorder.

SpiderMan

dr_dave
01-06-2007, 08:31 PM
<blockquote><font class="small">Quote SpiderMan:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote SpiderMan:</font><hr>Dave - HSV 7.5 looks a lot like a foul. Has this been questioned before?<hr /></blockquote>
I don't think HSV 7.5 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/HSV7-5.htm) looks like a foul, but I guess that depends on your definition of "foul." The cue ball is frozen to the object ball, so you are allowed (by the rules I know) to stroke through the ball, even though the cue ball is pushed in the process. Why do you think the shot is a foul?

Dave <hr /></blockquote>

I think that the tip must have made a second contact. Perhaps not all miscues are fouls, but this one appears to be.<hr /></blockquote>
I don't know of anything in standard rules that would make this shot a foul, even if there is a miscue. Do you?

Dave

Jal
01-07-2007, 10:27 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> I finally got around to shooting a video demo in response to spin transfer debate...<hr /></blockquote>Dr. Dave,

It's a pretty convincing demonstration, but it's been a bit disconcerting for me.

After coming off the cushion, the object ball travels about 9/10 of a diamond down table and 4 diamonds across, for a rebound of approximately 13 degrees with respect to the normal. Of course it varied from shot to shot; this is just a rough value. And it was apparently even greater in some cases.

In another thread I predicted, with considerable confidence no less, that it should come off at about the throw angle. It's not that I'm unfamiliar with these shots as a player, but I've never calculated the numeric angle. It appears that my estimate was off by a factor of three or four! /ccboard/images/graemlins/blush.gif

Do you (or anyone) have an explanation for this much angle?

Jim

SpiderMan
01-08-2007, 09:21 AM
<blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote SpiderMan:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote SpiderMan:</font><hr>Dave - HSV 7.5 looks a lot like a foul. Has this been questioned before?<hr /></blockquote>
I don't think HSV 7.5 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/HSV7-5.htm) looks like a foul, but I guess that depends on your definition of "foul." The cue ball is frozen to the object ball, so you are allowed (by the rules I know) to stroke through the ball, even though the cue ball is pushed in the process. Why do you think the shot is a foul?

Dave <hr /></blockquote>

I think that the tip must have made a second contact. Perhaps not all miscues are fouls, but this one appears to be.<hr /></blockquote>
I don't know of anything in standard rules that would make this shot a foul, even if there is a miscue. Do you?

Dave <hr /></blockquote>

Yes, it is always a foul when the cue contacts the cue ball twice. From the video, it appears that there is a miscue where the tip leaves the cueball and returns for a second contact.

Of course, no one could prove it without HS video, but I personally suspect that many miscues foul the cueball by re-contacting it with the side of the ferrule or the tip. This is seen very clearly in at least one miscue example on the so-called "Jacksonville" video.

HSV 7.5 isn't clear enough to actually see the tip lose contact, but this can be deduced. There's no time scale for the video, so I'll guess that the ball speeds are about 5 MPH, or 88 inches per second. The linear distance from first contact to finally losing contact is about 1.5 inches, which translates to an unlikely dwell time of 17 milliseconds. This leads me to believe that there is not continuous contact, but rather multiple contact.

SpiderMan

dr_dave
01-08-2007, 11:48 AM
<blockquote><font class="small">Quote Jal:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> I finally got around to shooting a video demo in response to spin transfer debate...<hr /></blockquote>Dr. Dave,

It's a pretty convincing demonstration, but it's been a bit disconcerting for me.

After coming off the cushion, the object ball travels about 9/10 of a diamond down table and 4 diamonds across, for a rebound of approximately 13 degrees with respect to the normal. Of course it varied from shot to shot; this is just a rough value. And it was apparently even greater in some cases.

In another thread I predicted, with considerable confidence no less, that it should come off at about the throw angle. It's not that I'm unfamiliar with these shots as a player, but I've never calculated the numeric angle. It appears that my estimate was off by a factor of three or four! /ccboard/images/graemlins/blush.gif

Do you (or anyone) have an explanation for this much angle?

Jim<hr /></blockquote>
Are you accounting for the throw angle affecting the approach angle into the rail? If there is an approach angle, the rebound angle will be at least that to start, and the transferred spin lengthens the angle even more. Also, becasue the shot is hit softly, the OB is rolling, which will increase the rebound angle even more.

Regards,
Dave

dr_dave
01-08-2007, 12:08 PM
<blockquote><font class="small">Quote SpiderMan:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote SpiderMan:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote SpiderMan:</font><hr>Dave - HSV 7.5 looks a lot like a foul. Has this been questioned before?<hr /></blockquote>
I don't think HSV 7.5 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/HSV7-5.htm) looks like a foul, but I guess that depends on your definition of "foul." The cue ball is frozen to the object ball, so you are allowed (by the rules I know) to stroke through the ball, even though the cue ball is pushed in the process. Why do you think the shot is a foul?

Dave <hr /></blockquote>

I think that the tip must have made a second contact. Perhaps not all miscues are fouls, but this one appears to be.<hr /></blockquote>
I don't know of anything in standard rules that would make this shot a foul, even if there is a miscue. Do you?

Dave <hr /></blockquote>

Yes, it is always a foul when the cue contacts the cue ball twice. From the video, it appears that there is a miscue where the tip leaves the cueball and returns for a second contact.<hr /></blockquote>A miscue is not a foul, unless it is used to perform an illegal "scoop" jump shot. Therefore, I don't think this shot should be ruled a foul.

<blockquote><font class="small">Quote SpiderMan:</font><hr>Of course, no one could prove it without HS video, but I personally suspect that many miscues foul the cueball by re-contacting it with the side of the ferrule or the tip. This is seen very clearly in at least one miscue example on the so-called "Jacksonville" video.<hr /></blockquote>
HSV 2.1 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/HSV2-1.htm) shows a good example of a typical miscue. HSV A.98 through A.109 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/index.html) show many more examples under different conditions. In most miscues, the ferrule and/or cue stick make secondary contact with the cue ball. That partially explains the slapping sound you hear.

<blockquote><font class="small">Quote SpiderMan:</font><hr>HSV 7.5 isn't clear enough to actually see the tip lose contact, but this can be deduced. There's no time scale for the video, so I'll guess that the ball speeds are about 5 MPH, or 88 inches per second. The linear distance from first contact to finally losing contact is about 1.5 inches, which translates to an unlikely dwell time of 17 milliseconds. This leads me to believe that there is not continuous contact, but rather multiple contact.<hr /></blockquote>
Again, when the cue ball is frozen, you are allowed to push through the cue ball with a normal stroke. I agree that there appears to be multiple or extended contact in HSV 7.5 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/HSV7-5.htm), but I think the stroke is still legal.

Regards,
Dave

SpiderMan
01-08-2007, 03:29 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote SpiderMan:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote SpiderMan:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote SpiderMan:</font><hr>Dave - HSV 7.5 looks a lot like a foul. Has this been questioned before?<hr /></blockquote>
I don't think HSV 7.5 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/HSV7-5.htm) looks like a foul, but I guess that depends on your definition of "foul." The cue ball is frozen to the object ball, so you are allowed (by the rules I know) to stroke through the ball, even though the cue ball is pushed in the process. Why do you think the shot is a foul?

Dave <hr /></blockquote>

I think that the tip must have made a second contact. Perhaps not all miscues are fouls, but this one appears to be.<hr /></blockquote>
I don't know of anything in standard rules that would make this shot a foul, even if there is a miscue. Do you?

Dave <hr /></blockquote>

Yes, it is always a foul when the cue contacts the cue ball twice. From the video, it appears that there is a miscue where the tip leaves the cueball and returns for a second contact.<hr /></blockquote>A miscue is not a foul, unless it is used to perform an illegal "scoop" jump shot. Therefore, I don't think this shot should be ruled a foul.

<blockquote><font class="small">Quote SpiderMan:</font><hr>Of course, no one could prove it without HS video, but I personally suspect that many miscues foul the cueball by re-contacting it with the side of the ferrule or the tip. This is seen very clearly in at least one miscue example on the so-called "Jacksonville" video.<hr /></blockquote>
HSV 2.1 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/HSV2-1.htm) shows a good example of a typical miscue. HSV A.98 through A.109 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/index.html) show many more examples under different conditions. In most miscues, the ferrule and/or cue stick make secondary contact with the cue ball. That partially explains the slapping sound you hear.

<blockquote><font class="small">Quote SpiderMan:</font><hr>HSV 7.5 isn't clear enough to actually see the tip lose contact, but this can be deduced. There's no time scale for the video, so I'll guess that the ball speeds are about 5 MPH, or 88 inches per second. The linear distance from first contact to finally losing contact is about 1.5 inches, which translates to an unlikely dwell time of 17 milliseconds. This leads me to believe that there is not continuous contact, but rather multiple contact.<hr /></blockquote>
Again, when the cue ball is frozen, you are allowed to push through the cue ball with a normal stroke. I agree that there appears to be multiple or extended contact in HSV 7.5 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/HSV7-5.htm), but I think the stroke is still legal.

Regards,
Dave <hr /></blockquote>

Dave,

When the cueball and object ball are frozen, you are allowed to shoot into it using a "normal stroke", as outlined by 3.23 in "general rules of pocket billiards".

You are NEVER allowed to "push through" any shot. Rule 3.24 further clarifies this by stating that it is a foul if the contact is "maintained for more than the momentary time commensurate with a stroked shot".

The HSV 7.5 contact is either "maintained for more than the momentary time commensurate with a stroked shot", or else it is a multiple contact. I believe it is the latter, but it would be a foul in either case.

SpiderMan

dr_dave
01-08-2007, 04:10 PM
<blockquote><font class="small">Quote SpiderMan:</font><hr>When the cueball and object ball are frozen, you are allowed to shoot into it using a "normal stroke", as outlined by 3.23 in "general rules of pocket billiards".<hr /></blockquote>
HSV 7.5 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/HSV7-5.htm) was shot with a normal stroke.

<blockquote><font class="small">Quote SpiderMan:</font><hr>You are NEVER allowed to "push through" any shot. Rule 3.24 further clarifies this by stating that it is a foul if the contact is "maintained for more than the momentary time commensurate with a stroked shot".<hr /></blockquote>
I think that with a frozen cue ball shot, you can't help but "push" the CB a little with a normal stroke and grip.

<blockquote><font class="small">Quote SpiderMan:</font><hr>The HSV 7.5 contact is either "maintained for more than the momentary time commensurate with a stroked shot", or else it is a multiple contact. I believe it is the latter, but it would be a foul in either case.<hr /></blockquote>Again, the cause for the extended contact or multiple contacts with this shot was a miscue, and I don't think a miscue is a foul. A miscue is a foul only when it is purposely used to execute an illegal "scoop" jump shot.

What do you and others (e.g., Bob) think?

Dave

dr_dave
01-08-2007, 04:23 PM
FYI, my detailed instructional article that covers spin transfer and the bank example is now available. You can view it here (http://www.engr.colostate.edu/~dga/pool/bd_articles/index.html) under March '07.

Please let me know if you have a feedback or suggestions. I still have a little time to make changes before it goes to print.

Regards,
Dave

Sid_Vicious
01-08-2007, 05:22 PM
"Again, the cause for the extended contact or multiple contacts with this shot was a miscue, and I don't think a miscue is a foul . A miscue is a foul only when it is purposely used to execute an illegal "scoop" jump shot."

I don't agree with the fact that it is NOT a foul, but you are correct. As long as this legality exists in the rules concerning miscues, fouling analyis should merely be a topic of discussion, such as we are having here. Frankly speaking though, there is nearly always some incidental collisions in all miscues, and IMO, it should be a foul...sid

Jal
01-08-2007, 06:19 PM
<blockquote><font class="small">Quote dr_dave:</font><hr>...Are you accounting for the throw angle affecting the approach angle into the rail? If there is an approach angle, the rebound angle will be at least that to start, and the transferred spin lengthens the angle even more. Also, becasue the shot is hit softly, the OB is rolling, which will increase the rebound angle even more.

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

You've given me some hope. I'll take a closer look. It did appear on several shots that the OB was may have been actually moving away from the end rail, but it was kind of hard to tell upon casual viewing. I did ignore the acquired topspin from the cloth, which I didn't think was much, but could be the salvation I'm looking for. Thanks for the suggestions.

Jim

cushioncrawler
01-08-2007, 07:04 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> FYI, my detailed instructional article that covers spin transfer and the bank example is now available. You can view it here (http://www.engr.colostate.edu/~dga/pool/bd_articles/index.html) under March '07. Please let me know if you have a feedback or suggestions. I still have a little time to make changes before it goes to print. Regards, Dave <hr /></blockquote>
Dr Dave. I dug up a few computer programz that i did some years ago. One program allowed me to stun a qball into an OB uzing varying amounts of sidespin. Today, in my "tests", the max amount of OB sidespin that i was able to get was 39.45% of the qball'z original spin.

This "tranzmitted side" is more than the 25% quoted in your article. In some cases it will depend on the initial conditions. In my "tests" the qball was stunned with V=1.29m/s and a Spin of 0.01m/s, 0.10m/s, 0.20m/s, and 0.40m/s, ie not very much sidespin.

Now, the strange thing that i found today is that no matter what combination of V and S that i might try, i was never able to come up with a full-ball impact where the qball's sidespin and the objectball's sidespin ended up with the same value. The largest amount of objectball sidespin was 65.2% of the qball final sidespin. This is amazing, i allwayz believed that it would be eezy to achieve equal sidespins. But, no -- not for a full ball impact. Amazing stuff. I will have to check my program for bugs -- but i wont find any -- this iz a "real" deal. Any thorts from across the ocean ?? madMac.

Qtec
01-08-2007, 07:14 PM
[ QUOTE ]
HSV 7.5 was shot with a normal stroke. <hr /></blockquote>

Dave, I guarantee you that there is not a player on this forum that in a match, would not call a foul on that stroke.
Anyone here who has ever played at a high level would not even attempt that shot in a match , certainly not at that Q angle, which virtually ensures a double hit.
Its the classic push stroke. End of story.
Qtec

cushioncrawler
01-08-2007, 07:34 PM
Dr Dave. I should have explained that the amount of transmitted side is limited partly by the fact that for a fullball impact the OB is thrown one way and the qball is thrown an equal "amount" the other. Thusly, the poor old qball finds that the OB is running away (to the side), and the qball karnt transmit any more spin, even tho it has a "theoretical" surplus. The sideways throw has spoilt the party.

Nothing can be done to overcome this little "problem". Higher friction wont work. Higher speed wont work. Less sidespin wont work. By the way, i used a single unvarying balltoball friction factor of 0.05, ie 1 in 20. This figure is a little on the low side, in which case my figures should increase just a little if using better numbers. I can improve the model by using a varyable friction, ie less friction at higher speeds -- but this iznt going to affect theze rezults much.

For solid spheres it appears that the max amount of transmitted side for a fullball impact is say 66%, here we are comparing it to the qball's final spin, not the qball's initial spin. U have my permission to call this limiting phenomenon madMac's Number, or madMac's First Law of Tranzmitted Side, or madMac's Theory. madMac.

Jal
01-09-2007, 12:12 AM
<blockquote><font class="small">Quote cushioncrawler:</font><hr>...Today, in my "tests", the max amount of OB sidespin that i was able to get was 39.45% of the qball'z original spin.<hr /></blockquote>Mac, I believe you called it right in your earlier post when you said it was 35.7%, which is 100(1/7)(5/2). This is the prediction of simple physics, anyway. It applies to all cueball spins up to and including that which produces maximum throw, and is independent of cueball speed and coefficient of friction. It's less at greater spins. But I have no doubt you're looking at details which I can't even imagine. Any idea how it got bumped up to 39.45?

<blockquote><font class="small">Quote cushioncrawler:</font><hr>...Now, the strange thing that i found today is that no matter what combination of V and S that i might try, i was never able to come up with a full-ball impact where the qball's sidespin and the objectball's sidespin ended up with the same value. The largest amount of objectball sidespin was 65.2% of the qball final sidespin.<hr /></blockquote>This is consistent with your 39.45% figure. But the simple physics answer (using 35.7%) would be 55.5%. The only way they could be equal is if the OB acquired 50% of the cueball's initial spin, I think.

Jim

SpiderMan
01-09-2007, 10:08 AM
<blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote SpiderMan:</font><hr>You are NEVER allowed to "push through" any shot. Rule 3.24 further clarifies this by stating that it is a foul if the contact is "maintained for more than the momentary time commensurate with a stroked shot".<hr /></blockquote>
I think that with a frozen cue ball shot, you can't help but "push" the CB a little with a normal stroke and grip..<hr /></blockquote>

This is something you should be able to demo using your high-speed video equipment. Set up two frozen balls with centers perfectly aligned in direction of aim, and stroke straight into them normally (no intentional "push"). I think that, without the miscue, you will observe only a "momentary contact". Analytically, it is no different than stroking into a single ball of 2X the mass.

SpiderMan



<blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote SpiderMan:</font><hr>The HSV 7.5 contact is either "maintained for more than the momentary time commensurate with a stroked shot", or else it is a multiple contact. I believe it is the latter, but it would be a foul in either case.<hr /></blockquote>Again, the cause for the extended contact or multiple contacts with this shot was a miscue, and I don't think a miscue is a foul. A miscue is a foul only when it is purposely used to execute an illegal "scoop" jump shot.
What do you and others (e.g., Bob) think?
Dave <hr /></blockquote>

Again, I'll refer you to the Jacksonville video, which clearly showed that some miscues are multiple-contact fouls while others are not. HSV 7.5 appears to me to fall in the "foul double-hit miscue" category, but even if it doesn't then it necessarily falls out of the "momentary contact" category and is therefore a foul push. Have you watched the Jacksonville video? It's only for insomniacs, but it was ground-breaking in the light it shed.

Of course miscues are almost never called as fouls, because the referee can't see whether it was or wasn't. Usually the referee isn't even present, because that would require one of the shooters to anticipate a miscue and call him over. Miscues are therefore one of those "grin, shrug, and continue" shots that are not judged rigorously. The shooter must get the benefit of doubt. He sometimes double-contacts, but isn't called on it.

I almost never call these against the shooter, mainly because the unwashed masses in bars I frequent aren't astute enough to follow any reasoning on why the CB went the "wrong" direction. And I also give the shooter the benefit, since I don't have HSV for instant replay. I doubt this will ever officially change.

I think you'd always get away with the foul in HSV 7.5, but I still assert that it happened.

SpiderMan

dr_dave
01-09-2007, 10:43 AM
<blockquote><font class="small">Quote cushioncrawler:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> FYI, my detailed instructional article that covers spin transfer and the bank example is now available. You can view it here (http://www.engr.colostate.edu/~dga/pool/bd_articles/index.html) under March '07. Please let me know if you have a feedback or suggestions. I still have a little time to make changes before it goes to print. Regards, Dave <hr /></blockquote>
Dr Dave. I dug up a few computer programz that i did some years ago. One program allowed me to stun a qball into an OB uzing varying amounts of sidespin. Today, in my "tests", the max amount of OB sidespin that i was able to get was 39.45% of the qball'z original spin.

This "tranzmitted side" is more than the 25% quoted in your article. In some cases it will depend on the initial conditions. In my "tests" the qball was stunned with V=1.29m/s and a Spin of 0.01m/s, 0.10m/s, 0.20m/s, and 0.40m/s, ie not very much sidespin.

Now, the strange thing that i found today is that no matter what combination of V and S that i might try, i was never able to come up with a full-ball impact where the qball's sidespin and the objectball's sidespin ended up with the same value. The largest amount of objectball sidespin was 65.2% of the qball final sidespin. This is amazing, i allwayz believed that it would be eezy to achieve equal sidespins. But, no -- not for a full ball impact. Amazing stuff. I will have to check my program for bugs -- but i wont find any -- this iz a "real" deal. Any thorts from across the ocean ?? madMac.<hr /></blockquote>

madMac,

In response to the messages from you and Jal, I've extended TP A.27 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/new/TP_A-27.pdf) to cover more cases. Jal's reported spin transfer percentage of 35.7% is derived. It applies only for the limiting case where the CB and OB gear together by the end of the collision. I've included an analysis and plots to cover all other cases as well. The spin transfer percentage numbers can be all over the place; however, I don't think these numbers are very useful. In the analysis, I define a spin transfer effectiveness (STE) ratio. It shows that spin transfer percentages are closer to the 25% range when spin transfer is used most effectively.

Regards,
Dave

PS: Thank you for posting the message. It made me think about things a lot more. I also changed the sentence in my article to read:
"It is usually in the 25% range when it is used most effectively (see TP A.27)."
I'll try to thank you and Jal in my next article when I discuss spin transfer further. Thanks again!

dr_dave
01-09-2007, 11:15 AM
<blockquote><font class="small">Quote SpiderMan:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote SpiderMan:</font><hr>You are NEVER allowed to "push through" any shot. Rule 3.24 further clarifies this by stating that it is a foul if the contact is "maintained for more than the momentary time commensurate with a stroked shot".<hr /></blockquote>
I think that with a frozen cue ball shot, you can't help but "push" the CB a little with a normal stroke and grip..<hr /></blockquote>
This is something you should be able to demo using your high-speed video equipment. Set up two frozen balls with centers perfectly aligned in direction of aim, and stroke straight into them normally (no intentional "push"). I think that, without the miscue, you will observe only a "momentary contact". Analytically, it is no different than stroking into a single ball of 2X the mass.<hr /></blockquote>
I've already added this to my list for my next HSV shoot.

<blockquote><font class="small">Quote SpiderMan:</font><hr><blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote SpiderMan:</font><hr>The HSV 7.5 contact is either "maintained for more than the momentary time commensurate with a stroked shot", or else it is a multiple contact. I believe it is the latter, but it would be a foul in either case.<hr /></blockquote>Again, the cause for the extended contact or multiple contacts with this shot was a miscue, and I don't think a miscue is a foul. A miscue is a foul only when it is purposely used to execute an illegal "scoop" jump shot.
What do you and others (e.g., Bob) think?
Dave <hr /></blockquote>
Again, I'll refer you to the Jacksonville video, which clearly showed that some miscues are multiple-contact fouls while others are not. HSV 7.5 appears to me to fall in the "foul double-hit miscue" category, but even if it doesn't then it necessarily falls out of the "momentary contact" category and is therefore a foul push. Have you watched the Jacksonville video? It's only for insomniacs, but it was ground-breaking in the light it shed.

Of course miscues are almost never called as fouls, because the referee can't see whether it was or wasn't. Usually the referee isn't even present, because that would require one of the shooters to anticipate a miscue and call him over. Miscues are therefore one of those "grin, shrug, and continue" shots that are not judged rigorously. The shooter must get the benefit of doubt. He sometimes double-contacts, but isn't called on it.

I almost never call these against the shooter, mainly because the unwashed masses in bars I frequent aren't astute enough to follow any reasoning on why the CB went the "wrong" direction. And I also give the shooter the benefit, since I don't have HSV for instant replay. I doubt this will ever officially change.

I think you'd always get away with the foul in HSV 7.5, but I still assert that it happened.<hr /></blockquote>
I have seen the Jacksonville video ... I have a copy. And I am aware that not all miscues result in multiple contacts. HSV A.98-A.109 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/index.html) show examples of every type of miscue for various speeds and tip hardnesses.

Concerning whether a miscue is a foul or not, I have always assumed that a miscue could never be called a foul unless it was used to execute an intentional, illegal "scoop" jump shot. However, the only statements about miscues I could find in the general rules are:
from 1.4: "The player may apply chalk to his tip to prevent miscues."
from 3.27: "Any miscue when executing a jump shot is a foul."

I think miscues should be specifically dealt with in the rules. They should be clearly designated as a foul or not. As you have suggested, it is too controversial to make it a judgment call. For now, I still stand by my original claim that a miscue is not a foul under typical intrepretations of the current rules.

Regards,
Dave

dr_dave
01-09-2007, 11:23 AM
<blockquote><font class="small">Quote Qtec:</font><hr><blockquote><font class="small">Quote dr_dave:</font><hr>HSV 7.5 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/HSV7-5.htm) was shot with a normal stroke.<hr /></blockquote>
Dave, I guarantee you that there is not a player on this forum that in a match, would not call a foul on that stroke.<hr /></blockquote>That may be true. But I bet if that the same player executed the shot (hypothetically), they would not allow their opponent to call it a foul. I think the shooter has a case, because the shot is a miscue.

<blockquote><font class="small">Quote Qtec:</font><hr>Anyone here who has ever played at a high level would not even attempt that shot in a match ...<hr /></blockquote>Agreed.

Regards,
Dave

Sid_Vicious
01-09-2007, 11:33 AM
"I think that with a frozen cue ball shot, you can't help but "push" the CB a little with a normal stroke and grip.."

You physics guys might tell me if there is some law which is relative to a 19oz cue, hitting parallel to the direction of CB trave, hitting into 10-11oz of mass between the two frozen balls and with tip follow through,,,would or would not make it predominently impossible to not to push. Frankly I like the rule as it is now, and I still feel that the miscue should be a foul merely because it very many times double hits, plus the arguement-factor within ght bulk of the BCA players would be eliminated altogether. If there is an iron-clad rule in place(and I assume there is) that miscues are grin and keep shooting...that accomplishes the second opinion I made about the disagreements which pop up...sid

dr_dave
01-09-2007, 11:45 AM
I agree that the rules should be clearer concerning miscues. However, if a miscue is a foul, then there would be a lot of controversy over what is and isn't a miscue. That's why I think it is better to not penalize a miscue with a foul if the shot is legal otherwise and if the miscue is not being intentionally used to execute a "scoop" jump shot. The miscue is penalty enough.

Regards,
Dave

<blockquote><font class="small">Quote Sid_Vicious:</font><hr> "I think that with a frozen cue ball shot, you can't help but "push" the CB a little with a normal stroke and grip.."

You physics guys might tell me if there is some law which is relative to a 19oz cue, hitting parallel to the direction of CB trave, hitting into 10-11oz of mass between the two frozen balls and with tip follow through,,,would or would not make it predominently impossible to not to push. Frankly I like the rule as it is now, and I still feel that the miscue should be a foul merely because it very many times double hits, plus the arguement-factor within ght bulk of the BCA players would be eliminated altogether. If there is an iron-clad rule in place(and I assume there is) that miscues are grin and keep shooting...that accomplishes the second opinion I made about the disagreements which pop up...sid <hr /></blockquote>

SpiderMan
01-09-2007, 01:49 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> I think miscues should be specifically dealt with in the rules. They should be clearly designated as a foul or not. As you have suggested, it is too controversial to make it a judgment call. For now, I still stand by my original claim that a miscue is not a foul under typical intrepretations of the current rules.

Regards,
Dave <hr /></blockquote>

Dave,

Your original claim did not mention miscue - your original statement was that you thought the rules allowed you to push the cueball if it was frozen to an object ball:

http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&amp;Board=ccb&amp;Number=241616&amp;page =0&amp;view=collapsed&amp;sb=5&amp;o=&amp;vc=1

We've since digressed to a discussion of miscue, which does also occur in HSV 7.5, but is not particularly relevant to determining whether the cueball was pushed (as you originally noted) or double-hit (as might alternately have happened). Either is a foul, though often undetectable and therefore seldom called in similar setups in game situations.

Continuing the miscue discussion - the problem with declaring a "miscue" always fair or foul is that we know it isn't black and white.

A multiple hit is always foul, and a push (as you originally assigned to HSV 7.5) is always foul. Sometimes, but not always, a miscue also involves a multiple hit, but it's seldom documented for instant replay.

When you can't adequately observe the phenomenon (as with the oft-referenced "simultaneous hit"), the shooter receives the benefit of doubt. This means we call most miscues fair, unless it's really obvious the shooter whacked the cueball sideways with his ferrule or did something deliberate to gain advantage (but that's an even stickier situation, trying to judge "intent").

That doubt wasn't there for HSV 7.5 because of the video documentation, which prompted me to note it has to be either a push or multiple hit. I'm not saying that a foul would be called in a game (it probably would not), but I am saying that a foul did occur.

Maybe we can get an opinion from someone with both rules and physics authority, such as Bob Jewett, to comment on the video.

SpiderMan

dr_dave
01-09-2007, 02:08 PM
<blockquote><font class="small">Quote SpiderMan:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> I think miscues should be specifically dealt with in the rules. They should be clearly designated as a foul or not. As you have suggested, it is too controversial to make it a judgment call. For now, I still stand by my original claim that a miscue is not a foul under typical intrepretations of the current rules.<hr /></blockquote>Your original claim did not mention miscue - your original statement was that you thought the rules allowed you to push the cueball if it was frozen to an object ball:

http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&amp;Board=ccb&amp;Number=241616&amp;page =0&amp;view=collapsed&amp;sb=5&amp;o=&amp;vc=1
<hr /></blockquote>Your points are well taken. I guess now we can start a separate debate on what a "push" is. When I get some time, I'll try to film with regular and high-speed video various frozen CB shots with various grips and strokes to see if it is easy to determine what is and isn't a "push."

<blockquote><font class="small">Quote SpiderMan:</font><hr>We've since digressed to a discussion of miscue, which does also occur in HSV 7.5, but is not particularly relevant to determining whether the cueball was pushed (as you originally noted) or double-hit (as might alternately have happened). Either is a foul, though often undetectable and therefore seldom called in similar setups in game situations.<hr /></blockquote>
I'm not so sure HSV 7.5 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/HSV7-5.htm) is a "push" shot. It's not clear because of the miscue. Regardless, I agree with you that the shot could not be reasonably ruled as a foul in a match, especially an unrefereed match.

So is HSV 7.5 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/HSV7-5.htm) a foul or not? I guess the answer is: "yes" theoretically but "no" practically.

Thank you for the interesting and challenging debate,
Dave

dr_dave
01-09-2007, 02:17 PM
<blockquote><font class="small">Quote SpiderMan:</font><hr>Continuing the miscue discussion - the problem with declaring a "miscue" always fair or foul is that we know it isn't black and white.<hr /></blockquote>
Because it is difficult to determine is a miscue is a foul or not (by a strict interpretation of the current rules), I think a miscue should specifically be designated as a non-foul. Isn't this how most leagues and tournaments currently deal with miscues? A foul is not called for a miscue (unless used for an illegal "scoop" jump shot).

<blockquote><font class="small">Quote SpiderMan:</font><hr>A multiple hit is always foul, and a push (as you originally assigned to HSV 7.5) is always foul. Sometimes, but not always, a miscue also involves a multiple hit, but it's seldom documented for instant replay.

When you can't adequately observe the phenomenon (as with the oft-referenced "simultaneous hit"), the shooter receives the benefit of doubt. This means we call most miscues fair, unless it's really obvious the shooter whacked the cueball sideways with his ferrule or did something deliberate to gain advantage (but that's an even stickier situation, trying to judge "intent").

That doubt wasn't there for HSV 7.5 because of the video documentation, which prompted me to note it has to be either a push or multiple hit. I'm not saying that a foul would be called in a game (it probably would not), but I am saying that a foul did occur.<hr /></blockquote>Agreed.

<blockquote><font class="small">Quote SpiderMan:</font><hr>Maybe we can get an opinion from someone with both rules and physics authority, such as Bob Jewett, to comment on the video.<hr /></blockquote>I would also be curious to see what Bob has to say about miscues, pushes, fouls, and HSV 7.5 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/HSV7-5.htm).

Thanks again for your thorough responses,
Dave

SpiderMan
01-09-2007, 02:19 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote SpiderMan:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> I think miscues should be specifically dealt with in the rules. They should be clearly designated as a foul or not. As you have suggested, it is too controversial to make it a judgment call. For now, I still stand by my original claim that a miscue is not a foul under typical intrepretations of the current rules.<hr /></blockquote>Your original claim did not mention miscue - your original statement was that you thought the rules allowed you to push the cueball if it was frozen to an object ball:

http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&amp;Board=ccb&amp;Number=241616&amp;page =0&amp;view=collapsed&amp;sb=5&amp;o=&amp;vc=1
<hr /></blockquote>Your points are well taken. I guess now we can start a separate debate on what a "push" is. When I get some time, I'll try to film with regular and high-speed video various frozen CB shots with various grips and strokes to see if it is easy to determine what is and isn't a "push."

<blockquote><font class="small">Quote SpiderMan:</font><hr>We've since digressed to a discussion of miscue, which does also occur in HSV 7.5, but is not particularly relevant to determining whether the cueball was pushed (as you originally noted) or double-hit (as might alternately have happened). Either is a foul, though often undetectable and therefore seldom called in similar setups in game situations.<hr /></blockquote>
I'm not so sure HSV 7.5 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/HSV7-5.htm) is a "push" shot. It's not clear because of the miscue. Regardless, I agree with you that the shot could not be reasonably ruled as a foul in a match, especially an unrefereed match.

So is HSV 7.5 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/HSV7-5.htm) a foul or not? I guess the answer is: "yes" theoretically but "no" practically.

Thank you for the interesting and challenging debate,
Dave <hr /></blockquote>

And to you for continuing to provide such outstanding material to us all, to fuel such debates.

I sometimes feel guilty to jump in and argue, as it's your data and not one in a hundred (or more) of us has the facility to reproduce your experiments. I guess it's the engineer in me - I can't help it.

SpiderMan

dr_dave
01-09-2007, 02:24 PM
<blockquote><font class="small">Quote SpiderMan:</font><hr><blockquote><font class="small">Quote dr_dave:</font><hr>Thank you for the interesting and challenging debate<hr /></blockquote>
And to you for continuing to provide such outstanding material to us all, to fuel such debates.

I sometimes feel guilty to jump in and argue, as it's your data and not one in a hundred (or more) of us has the facility to reproduce your experiments.<hr /></blockquote>
Thank you for your kind and supportive words.

Please continue to keep me honest by challenging my stuff. Most of my better instructional articles are the result of such challenges and debate.

Thanks again,
Dave (still part Texan at heart)

cushioncrawler
01-09-2007, 02:49 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> ..... Jal's reported spin transfer percentage of 35.7% is derived. It applies only for the limiting case where the CB and OB gear together by the end of the collision. I've included an analysis and plots to cover all other cases as well. The spin transfer percentage numbers can be all over the place; however, I don't think these numbers are very useful. In the analysis, I define a spin transfer effectiveness (STE) ratio. It shows that spin transfer percentages are closer to the 25% range when spin transfer is used most effectively..... <hr /></blockquote>
Dr. Dave. Just thinking a little more....

1... I think that if the OB and qball have the same sidespin before impact then they will have equal sidespin after impact (but this equality is unlikely if the qball has some rolling or screw, ie equality would apply for stun). Ignoring bed friction etc during impact.

2... I might have a program hiding somewhere that deals with offcenter impacts -- i will look later -- anyhow, i think that this will tell me that "gearing" is an impossibility for any imact of any sort (unless there is gearing pre-impact). Still thinking.

3... Re madMac's Number, ie 0.666 -- i will run that little program more accurately to a few decimal places, and i will insert a friction factor of 0.06 (instead of 0.05), and i might use varyable friction allso, to check. madMac.

cushioncrawler
01-09-2007, 03:30 PM
<blockquote><font class="small">Quote Jal:</font><hr> .... I believe you called it right in your earlier post when you said it was 35.7%, which is 100(1/7)(5/2). This is the prediction of simple physics, anyway. It applies to all cueball spins up to and including that which produces maximum throw, and is independent of cueball speed and coefficient of friction. It's less at greater spins. But I have no doubt you're looking at details which I can't even imagine. Any idea how it got bumped up to 39.45? ..... The only way they could be equal is if the OB acquired 50% of the cueball's initial spin, I think... <hr /></blockquote>
Hi Jim -- I am looking further into this as i speak -- Will get back to u and doc a bit later. In the meantime, what do u think about the "impossibility of gearing" bizness that i mentioned to Dr Dave. madMac.

dr_dave
01-09-2007, 04:04 PM
<blockquote><font class="small">Quote cushioncrawler:</font><hr>1... I think that if the OB and qball have the same sidespin before impact then they will have equal sidespin after impact (but this equality is unlikely if the qball has some rolling or screw, ie equality would apply for stun). Ignoring bed friction etc during impact.<hr /></blockquote>Sounds right to me. Although, you must mean "equal and opposite" sidespin, so the CB and OB are "gearing." All of the physics and math details can be found in TP's A.14, A.26, and A.27 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/index.html).

<blockquote><font class="small">Quote cushioncrawler:</font><hr>2... I might have a program hiding somewhere that deals with offcenter impacts -- i will look later -- anyhow, i think that this will tell me that "gearing" is an impossibility for any imact of any sort (unless there is gearing pre-impact). Still thinking.<hr /></blockquote>Not true. It is possible for the relative surface speed between the CB and OB to be lost during the collision. The details can be found in TP A.14 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/new/TP_A-14.pdf) (see Equations 8-15).

<blockquote><font class="small">Quote cushioncrawler:</font><hr>3... Re madMac's Number, ie 0.666 -- i will run that little program more accurately to a few decimal places, and i will insert a friction factor of 0.06 (instead of 0.05), and i might use varyable friction allso, to check. madMac.<hr /></blockquote>A good model and equation for friction can be found in TP A.14 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/new/TP_A-14.pdf) (see page 4).

Regards,
Dave

Jal
01-09-2007, 09:31 PM
<blockquote><font class="small">Quote cushioncrawler:</font><hr>...In the meantime, what do u think about the "impossibility of gearing" bizness that i mentioned to Dr Dave. madMac. <hr /></blockquote>I'm glad you asked Mac because it caught my eye. I assume we all agree that "gearing" is synonymous with rolling. If so, I have to agree with Dr. Dave that it is possible.

If you look at the experimental plots of throw angle vs cut angle for stun shots without english (Bob Jewett has these at his website and I'm pretty sure Dr. Dave has independently obtained ones also), throw angle increases almost linearly up to certain cut angle. The simplest explanation is that they end up rolling across each other during impact. This makes the throw angle independent of mu (COF) within this range of cut angles, namely:

tan(gamma) = [(1/7)Vsin(theta)]/Vcos(theta) = (1/7)tan(theta)

where gamma is the throw angle and theta is the cut angle. The quantity in brackets is 1/7'th of the initial surface speed, the rest of which gets taken up as cueball throw and spin on both balls. (I'm pretty sure you're familiar with this Mac, just thought I'd offer up the best evidence.)

Otherwise the tangent of the throw angle would be equal to mu (as it is outside of this range), and you should see large values of throw at tiny cut angles. Either that or you would have to assume that mu exhibits some odd behavior as a function of surface speed, which I suppose can't be ruled out apriori, but seems unlikely.

The size of the range of cut angles for which the above formula apparently applies, does depend on mu, however.

If you can show that it's poppycock, that would be interesting too.

Jim

cushioncrawler
01-09-2007, 10:51 PM
<blockquote><font class="small">Quote Jal:</font><hr> <blockquote><font class="small">Quote cushioncrawler:</font><hr>...In the meantime, what do u think about the "impossibility of gearing" bizness that i mentioned to Dr Dave. madMac. <hr /></blockquote>I'm glad you asked Mac because it caught my eye. I assume we all agree that "gearing" is synonymous with rolling. If so, I have to agree with Dr. Dave that it is possible...... <hr /></blockquote>
Jim. I am still thinking about gearing -- more later.

But, regarding that max tranzmitted side bizness, for a full-ball impact -- u said the max iz 35.71%, i agreed but later did some comps that said 39%, and Dr Dave is sticking with a max of 25% ( but later said that max might be more). Ok, i have now added a few more decimal points to my computer programz, and i have taken greater pains to find the accurate "zero-points" where ball to ball sliding stops or where impact stops etc.

And, the official rezult iz --- 35.71% iz the best answer -- congratulationz to our winner -- Jim -- (but Dr Dave will have something to say here).

This rezult iz very interesting. The only way that i could get it (35.71%) woz when i played with the qball's initial spin (remember there iz no rolling, ie it iz a stun shot), i varyd the spin untill i got the happy situation that ball to ball slippage continued up untill the end of ball to ball impact, and, here, i mean that ball to ball slippage ceased at the same time that impact ceased.

If "too much" qball spin, the tranzmitted side falls gradually (but quickly) below 35.71%, ie down to 10% (or much lower).

If "too little" qball spin, the tranzmitted side rizes gradually above 35.71%, ie up to my 39%, but not much higher.

And, here (for 35.71%), the ratio of OB final-spin to qball final-spin iz 55.56%, az u said i think, this followz naturally of course, one goze with the other.

Now, another thing, i did the comps for a fixed friction factor of 0.05, and allso for 0.06. Changing the friction changed the rezults for the amount of tranzmitted side in every case (ie for any one qball initial spin rate). But, the 35.71% figure never changed, it stayed the same -- but i had to find (by trial and error) the correct qball initial spin rate, ie such that slippage stopped at the same time as impact stopped. For instance, the critical spin rate for V = 1.28m/s and friction = 0.05 was 0.44184m/s, and for 0.06 was 0.53020m/s. So, the 35.71% iz correct for all frictions (if not zero).

Anyhow, Dr Dave wont be happy with this -- but i am pretty happy with my comps -- i think that Bob is going to end up with the job of referee here.

Anyhow, gearing is impossible for a fullball impact. Now, i will look into gearing etc for other impacts -- i think that the truth will lay "in the middle". madMac.

cushioncrawler
01-09-2007, 11:36 PM
Dr. Dave -- Since adding some decimal places etc, i find that 35.71% is the "best" answer for the amount of tranzmitted side possible for a fullball stunned impact. The details are in my previous posting to Jim.

But i did make one mistake there, my latest computations show that for small values of qball initial spin the tranzmitted spin in fact barely reaches 37.5% and the OB/QB final spins ratio barely reaches 60.0% (not the 39% and 66% figures that i mentioned yesterday). So, madMac's Number is more like 60%, rather than 66.6% -- allso the 60% falls a bit if friction is reduced -- allso, i havnt really looked at how this 60% "upper limit" responds to V of impact (i have only looked at a qball initial V of 1.288m/s, ie a slow impact).

I am now even more convinced that gearing is impossible for a fullball impact (any comments here). I wouldnt have thort so one week ago. Strange bizness.

I am now keen to look more closely at the gearing question for non-fullball impacts -- this will be a more difficult project i think. madMac.

Jal
01-09-2007, 11:44 PM
<blockquote><font class="small">Quote dr_dave:</font><hr>...Jal's reported spin transfer percentage of 35.7% is derived. It applies only for the limiting case where the CB and OB gear together by the end of the collision.<hr /></blockquote>Dr. Dave,

But I would like to add that this covers a fairly broad, though minority range of situations. It applies to tip offsets from zero to almost (1/5)R for slow shots, and one-half of that for very fast shots, ignoring additional spin picked up from the cloth.

I'm not sure about your second and third graphs in TP A.27.

You labeled the second one as "spin transfer percentage" but are apparently not dividing by the cueball's pre-impact spin (looking at the equation for STP). If you did, I can't see how you would get anything but a constant of 35.7% for all initial cueball spin values from zero up to the one that yields maximum throw at a particular speed. In other words, I think the equation where you derive the 35.7% figure should apply to this portion of the plots.

<blockquote><font class="small">Quote dr_dave:</font><hr>...In the analysis, I define a spin transfer effectiveness (STE) ratio.<hr /></blockquote>I think this could be very useful to a serious but still relatively inexperienced banker (and to us weekend players). Thank you for adding that but I think it needs some modification as per above.

Awaiting your verdict.

Jim

dr_dave
01-10-2007, 07:20 AM
<blockquote><font class="small">Quote cushioncrawler:</font><hr>... regarding that max tranzmitted side bizness, for a full-ball impact -- u said the max iz 35.71%, i agreed but later did some comps that said 39%, and Dr Dave is sticking with a max of 25% ( but later said that max might be more).<hr /></blockquote>I'm not sticking to 25%. The 2nd plot on page 4 of my revised TP A.27 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/new/TP_A-27.pdf) clearly shows that the spin transfer percentage can be much more than 25%.

<blockquote><font class="small">Quote cushioncrawler:</font><hr>Ok, i have now added a few more decimal points to my computer programz, and i have taken greater pains to find the accurate "zero-points" where ball to ball sliding stops or where impact stops etc.

And, the official rezult iz --- 35.71% iz the best answer -- congratulationz to our winner -- Jim -- (but Dr Dave will have something to say here).<hr /></blockquote>I have nothing more to say other than "Thank You" to both of you for helping me think through and add more detail to TP A.27 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/new/TP_A-27.pdf). I think the "spin transfer effectiveness" (STE) measure I added tells a more complete story for spin transfer. (BTW, if you want to be picky, the exact value for "gearing" spin transfer is 5/14, even better than 37.51%)

Regards,
Dave

dr_dave
01-10-2007, 07:35 AM
<blockquote><font class="small">Quote Jal:</font><hr> <blockquote><font class="small">Quote cushioncrawler:</font><hr>...In the meantime, what do u think about the "impossibility of gearing" bizness that i mentioned to Dr Dave. madMac. <hr /></blockquote>I'm glad you asked Mac because it caught my eye. I assume we all agree that "gearing" is synonymous with rolling. If so, I have to agree with Dr. Dave that it is possible.<hr /></blockquote>
madMac,
It is not only possible. It is absolutely true. The proof is in TP A.14 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/new/TP_A-14.pdf). I don't have any conclusive video evidence, but I think HSV A.82 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/new/HSVA-82.htm) helps make it more believable.

<blockquote><font class="small">Quote Jal:</font><hr>If you look at the experimental plots of throw angle vs cut angle for stun shots without english (Bob Jewett has these at his website and I'm pretty sure Dr. Dave has independently obtained ones also), throw angle increases almost linearly up to certain cut angle. The simplest explanation is that they end up rolling across each other during impact. This makes the throw angle independent of mu (COF) within this range of cut angles<hr /></blockquote>
FYI, my experimental plots and comparison to theory can be found in my September '06 instructional article (http://www.engr.colostate.edu/~dga/pool/bd_articles/2006/sept06.pdf). Bob's experimental plot, which looks better, can be found here (http://www.sfbilliards.com/throw.gif). That's pretty solid evidence ... independent experimental verification backed up by theory.

<blockquote><font class="small">Quote Jal:</font><hr>If you can show that it's poppycock, that would be interesting too.<hr /></blockquote>madMac,
If you can show it is poppycock, I'll personally fly to Australia and let you kick my arse with the biggest boot you can find. /ccboard/images/graemlins/grin.gif

Regards,
Dave

dr_dave
01-10-2007, 09:36 AM
<blockquote><font class="small">Quote Jal:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr>...Jal's reported spin transfer percentage of 35.7% is derived. It applies only for the limiting case where the CB and OB gear together by the end of the collision.<hr /></blockquote>Dr. Dave,

But I would like to add that this covers a fairly broad, though minority range of situations. It applies to tip offsets from zero to almost (1/5)R for slow shots, and one-half of that for very fast shots, ignoring additional spin picked up from the cloth.<hr /></blockquote>
Agreed. I shouldn't have used the word "limiting" because it is misleading. It is the "limiting case" only because it represents a limitation on the amount of spin that can be transferred.

Regards,
Dave

dr_dave
01-10-2007, 09:48 AM
<blockquote><font class="small">Quote Jal:</font><hr>I'm not sure about your second and third graphs in TP A.27 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/new/TP_A-27.pdf).

You labeled the second one as "spin transfer percentage" but are apparently not dividing by the cueball's pre-impact spin (looking at the equation for STP). If you did, I can't see how you would get anything but a constant of 35.7% for all initial cueball spin values from zero up to the one that yields maximum throw at a particular speed. In other words, I think the equation where you derive the 35.7% figure should apply to this portion of the plots.<hr /></blockquote>
Jim,

Thank you so much for spotting this error. (I thought the results looked a little suspicious.) The equation and graph are now correct. I've also had to once more revise the sentence in my article. It now reads: "The amount of spin transfer can be as high as 35.7% (see TP A.27), but it can be much lower." I hope the editor can make the change, because I think I finally have it right.

I'll try to thank you in my next article. You have helped me a bunch with this one.

Thanks,
Dave

dr_dave
01-10-2007, 09:53 AM
<blockquote><font class="small">Quote Jal:</font><hr><blockquote><font class="small">Quote dr_dave:</font><hr>...In the analysis, I define a spin transfer effectiveness (STE) ratio.<hr /></blockquote>I think this could be very useful to a serious but still relatively inexperienced banker (and to us weekend players). Thank you for adding that but I think it needs some modification as per above.

Awaiting your verdict.<hr /></blockquote>
I also think this measure and graph are useful for understanding spin transfer effects.

I don't think this graph is impacted by the spin transfer percentage issue (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&amp;Board=ccb&amp;Number=241857&amp;page =0&amp;view=collapsed&amp;sb=5&amp;o=&amp;vc=1), but let me know if you still think otherwise.

Thanks,
Dave

Chopstick
01-10-2007, 10:13 AM
How about this one?

tan(gamma) = [(1/7)Vsin(theta)]/Vcos(theta) = (1/7)tan(theta) <font color="blue">= (Three Friggin Balls) </font color>

Sorry guys, I just couldn't resist. /ccboard/images/graemlins/laugh.gif

dr_dave
01-10-2007, 10:24 AM
<blockquote><font class="small">Quote Chopstick:</font><hr> How about this one?

tan(gamma) = [(1/7)Vsin(theta)]/Vcos(theta) = (1/7)tan(theta) <font color="blue">= (Three Friggin Balls) </font color>

Sorry guys, I just couldn't resist. /ccboard/images/graemlins/laugh.gif <hr /></blockquote>
Nice work. You just earned yourself an A+. /ccboard/images/graemlins/wink.gif

Dr. Dave

Jal
01-10-2007, 12:50 PM
<blockquote><font class="small">Quote dr_dave:</font><hr>...I don't think this graph is impacted by the spin transfer percentage issue (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&amp;Board=ccb&amp;Number=241857&amp;page =0&amp;view=collapsed&amp;sb=5&amp;o=&amp;vc=1), but let me know if you still think otherwise.<hr /></blockquote>Yes, of course you're correct Dr. Dave. (One of these days we'll all get it right!). But Mac's model may still have something to say about it. Maybe looking at inelasticity and the conservations laws may swing things in favor of his slightly larger numbbers? I'll try to take a look at this later, but be my guest. /ccboard/images/graemlins/smile.gif

For all the good stuff you've given us, it's nice that we can be of service once in a while.

Jim

Jal
01-10-2007, 12:57 PM
<blockquote><font class="small">Quote Chopstick:</font><hr> How about this one?

tan(gamma) = [(1/7)Vsin(theta)]/Vcos(theta) = (1/7)tan(theta) <font color="blue">= (Three Friggin Balls) </font color>

Sorry guys, I just couldn't resist. /ccboard/images/graemlins/laugh.gif <hr /></blockquote>Somedays, sometimes, I'm afraid you don't know how right you are. But ya doesn't has to rub it in.

Jim

Jal
01-10-2007, 01:03 PM
<blockquote><font class="small">Quote cushioncrawler:</font><hr>...But i did make one mistake there, my latest computations show that for small values of qball initial spin the tranzmitted spin in fact barely reaches 37.5% and the OB/QB final spins ratio barely reaches 60.0% (not the 39% and 66% figures that i mentioned yesterday). So, madMac's Number is more like 60%, rather than 66.6% -- allso the 60% falls a bit if friction is reduced -- allso, i havnt really looked at how this 60% "upper limit" responds to V of impact (i have only looked at a qball initial V of 1.288m/s, ie a slow impact).<hr /></blockquote>If you get the time, and when you're ready, can you give us some idea what things your model takes into account beyond the "simple physics", Mac.

<blockquote><font class="small">Quote cushioncrawler:</font><hr>I am now even more convinced that gearing is impossible for a fullball impact (any comments here). <hr /></blockquote>Why do you think so?

Jim

cushioncrawler
01-10-2007, 03:35 PM
<blockquote><font class="small">Quote Jal:</font><hr> .... But Mac's model may still have something to say about it. Maybe looking at inelasticity and the conservations laws may swing things in favor of his slightly larger numbbers? I'll try to take a look at this later, but be my guest.... <hr /></blockquote>
Jim, The elasticity and "e" etc wouldnt affect things much. My method (computer model) takes into account the "loss" due to throw, i karnt really add much more than what i posted earlyr, as follows...

<blockquote><font class="small">Quote madMac:</font><hr>...Dr Dave. I should have explained that the amount of transmitted side is limited partly by the fact that for a fullball impact the OB is thrown one way and the qball is thrown an equal "amount" the other. Thusly, the poor old qball finds that the OB is running away (to the side), and the qball karnt transmit any more spin, even tho it has a "theoretical" surplus. The sideways throw has spoilt the party.

Nothing can be done to overcome this little "problem". Higher friction wont work. Higher speed wont work. Less sidespin wont work.....

For solid spheres it appears that the max amount of transmitted side for a fullball impact is say 66%, here we are comparing it to the qball's final spin, not the qball's initial spin. U have my permission to call this limiting phenomenon madMac's Number, or madMac's First Law of Tranzmitted Side, or madMac's Theory..... <hr /></blockquote>
My computer model steps throo an impact at about 0.000001 seconds at a step, using simple Newton to update the speeds and spins and forces and slippage etc for each step.

Dr Dave sez that 35.71% transfer is achieved if gearing is achieved at the very instant that impact finishes. In my model, i use trial and error for setting the qball's initial spin, such that balltoball slippage stops at the very instant that impact stops. Here, the transfer is 35.71%. It is never 35.71% for any other "spin" condition (full ball stun impact here). Note that i said "such that slippage stops" -- there is no gearing here, there is never any gearing for any fullball impact (except for when the qball haz zero spin).

My model might not be a very true model -- it is based on measurements and properties from my tests on small balls -- but as far as i can see none of these properties are critical. For instance my computer model estimates the size of the temporary flatspot for each step, plus the force, and includes an allowance for inelasticity "e" -- none of which is critical to the results (spin transfer) that we are talking about. Proof (for me) is that when i took much care i got exactly 35.71% for both cases that i modelled (ie 2 cases where slippage stopped at the same time as impact stopped), one case was for friction=0.05, and the other was for 0.06.

I found that when the qball's initial spin was more than the "critical" value then slippage continued beyond the end of impact (so to speak), and the 35.71% dropped towards 0.00% (but lets say towards 10.00% in the practical range of qball spins).

I found that when the qball's initial spin was less than the "critical" value then slippage stopped before the end of impact, and the 35.71% rose to 37.52% (this was for an initial qball spin of 0.01m/s). It might go much higher than 37.52%, but then the qball's initial spin would be so small that the % would be allmost meaningless. For 0.05 the 37.52% fell to 37.39%, so friction affects this a bit here (not so for the 35.71% figure).

When i say "slippage stopped before the end of impact", Dr Dave might call this a form of gearing. Gearing i guess can be defined in a number of ways.

1A... The classical definition might be that (during an impact) the qball and object ball have equal and opposite spin rates and that at the same instant there is zero balltoball slippage.

1B... Or, the classical definition might be that (during an impact) the qball and object ball have equal and opposite spin rates in the horizontal plane and that at the same instant there is zero balltoball slippage in the horizontal plane, even tho there might be a vertical component of spin and slippage.

2A... Or, that (during an impact) there is zero balltoball slippage, even tho the spin rates might not be "equal".

2B... Or, that (during an impact) there is zero balltoball slippage in the horizontal plane, even tho there might be slippage in a vertical plane (and even tho the spin rates might not be equal).

But, i feel sure that Dr Dave is talking about 1A gearing. I reckon that 2A "gearing" happens here (or can happen sometimes), and that 1A is impossible (alltimes). If Dr Dave swears on a stack of bibles that he meant 2A all along, then he will save the cost of a plane ticket. Here i might add that i have a trophy on my wall for winning a long-kicking contest -- i won this when a mere boy, kicking an ozzy rules football, versus the best men from an ozzy rules footy club, and at that stage i had only ever played soccer (they were all pissed off i can tell u). The good news is that if Dr Dave duz fly over, at least he wont need a return ticket.

What do u think ?? madMac.

cushioncrawler
01-10-2007, 04:12 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> ....If you can show it is poppycock, I'll personally fly to Australia and let you kick my arse with the biggest boot you can find. /ccboard/images/graemlins/grin.gif Regards, Dave <hr /></blockquote>
Hi Dr Dave -- I tryd to explain my thinking in the previous posting to Jim -- duz that posting help much?? -- i can probably improov on that a bit if anyone wants.

I suppoze the question arizes -- How iz it possible to exceed 35.71%??? -- this refers to my 37.52% result -- in fact i think that Jim did ask that question. I think that 35.71% is a sort of theoretical upper limit for transfer, based on the unavoidable standard losses due to balltoball slippage friction (heat) losses (i guess that this sort of loss applies for all frictional drives and couplings, if there is slippage).

I think that transfer of spin is based on force and time. But heat loss (work) is based on force and distance. In my (our) impacts, the throw of the OB robs some of the effective slippage distance, in fact the reverse-throw of the qball likewize robs some slippage distance, ie a double dose of throw, and yet the force itself is unchanged (in my model), and when slippage (slowly) stops the friction force (abruptly) falls to zero allso. Thusly we can get more than 35.71%. If the 2 balls were fixed on some sort of axles and held together then 35.71% would be the upper limit.

What do u think ??? I can explain my thinking better if anyone wants. madMac.

dr_dave
01-10-2007, 04:39 PM
<blockquote><font class="small">Quote cushioncrawler:</font><hr>I tryd to explain my thinking in the previous posting to Jim -- duz that posting help much?? -- i can probably improov on that a bit if anyone wants.<hr /></blockquote>
Could you provide a quote from or a link to the posting, so I know which one you are talking about?

<blockquote><font class="small">Quote cushioncrawler:</font><hr>I suppoze the question arizes -- How iz it possible to exceed 35.71%??? -- this refers to my 37.52% result -- in fact i think that Jim did ask that question. I think that 35.71% is a sort of theoretical upper limit for transfer, based on the unavoidable standard losses due to balltoball slippage friction (heat) losses (i guess that this sort of loss applies for all frictional drives and couplings, if there is slippage).<hr /></blockquote>
The theoretical result (35.71%) accounts for momentum conservation directly ... it doesn't rely on energy calculations (see TP A.27 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/new/TP_A-27.pdf)). Now, one thing the analysis doesn't account for is ball inelasticity (i.e., the coefficient of restitution). I think this would just reduce the spin transfer numbers a little because there is less normal impulse than in the ideal case (see Equation 8 in TP A.5 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/new/TP_A-5.pdf)).

Regards,
Dave

dr_dave
01-10-2007, 04:43 PM
<blockquote><font class="small">Quote cushioncrawler:</font><hr>I think that transfer of spin is based on force and time.<hr /></blockquote>
Agreed. Impulse is the sum of force over time, and impulse is what changes momentum.

<blockquote><font class="small">Quote cushioncrawler:</font><hr>But heat loss (work) is based on force and distance. In my (our) impacts, the throw of the OB robs some of the effective slippage distance, in fact the reverse-throw of the qball likewize robs some slippage distance, ie a double dose of throw, and yet the force itself is unchanged (in my model), and when slippage (slowly) stops the friction force (abruptly) falls to zero allso. Thusly we can get more than 35.71%. If the 2 balls were fixed on some sort of axles and held together then 35.71% would be the upper limit.<hr /></blockquote>Sorry, but you lose me here.

Regards,
Dave

dr_dave
01-10-2007, 04:57 PM
<blockquote><font class="small">Quote Jal:</font><hr>... Maybe looking at inelasticity and the conservations laws may swing things in favor of his slightly larger numbbers? I'll try to take a look at this later, but be my guest.<hr /></blockquote>
If you do want to explore this further, TP A.5 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/new/TP_A-5.pdf) might be a useful starting point, combined with TP A.27 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/new/TP_A-27.pdf). With a cursory look, I think the coefficient of restitution would decrease the normal impulse and decrease the spin transfer number a little. I don't feel a need to pursue this further, but please let me know if you come up with something to the contrary.

<blockquote><font class="small">Quote Jal:</font><hr>For all the good stuff you've given us, it's nice that we can be of service once in a while.<hr /></blockquote>
Thanks again for your help, and thank you for the kind words.

Regards,
Dave

cushioncrawler
01-10-2007, 05:41 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> ....Could you provide a quote from or a link to the posting, so I know which one you are talking about?...<hr /></blockquote>
This is the posting before this one (but unfortunately it appears overleaf at the bottom of page 2).

<blockquote><font class="small">Quote dr_dave:</font><hr>...The theoretical result (35.71%) accounts for momentum conservation directly ... it doesn't rely on energy calculations .... Now, one thing the analysis doesn't account for is ball inelasticity (i.e., the coefficient of restitution). I think this would just reduce the spin transfer numbers a little because there is less normal impulse than in the ideal case.... <hr /></blockquote>
But, the 35.71% duz take energy into account. If it were a cogged qball (with spin) impacting fullball on a cogged OB, then energy wouldnt be a consideration. The qball would end up being thrown left (say) with say 42.7% of its initial spin remaining, and the OB would go right with equal but opposite spin and equal but opposite xx speed. The 42.7% is my wild guess based on "losses" due to throw(s), but based on zero losses due to friction (alltho u could introduce some sort of e here for this sort of cogged "coming together", which would reduce the % just a bit). Thus, any momentum-type calculation giving something less than say 42.7% (eg 35.71%) can only do that by in some way taking into account the frictional slippage energy losses, whether it is readily apparant or not.

The coefficient of restitution (ie being less than 1) would reduce the impulse to the OB and hence reduce the transfer of spin, but, at the same time, it duznt. Its a chicken and egg sort of thing. Most of my (our) work on balltoball friction is based mainly on the outcome of throw tests -- the throw tests allready have an inherent dependence on e. I guess that if we used a "pure" or "direct" sort of value for balltoball friction, then an allowance for e would be necessary to accurately predict spin transfer and throw.

I will pause here, is any of this making sense?? madMac.

cushioncrawler
01-10-2007, 06:13 PM
<blockquote><font class="small">Quote dr_dave:</font><hr><blockquote><font class="small">Quote cushioncrawler:</font><hr>....But heat loss (work) is based on force and distance. In my (our) impacts, the throw of the OB robs some of the effective slippage distance, in fact the reverse-throw of the qball likewize robs some slippage distance, ie a double dose of throw, and yet the force itself is unchanged (in my model), and when slippage (slowly) stops the friction force (abruptly) falls to zero allso. Thusly we can get more than 35.71%. If the 2 balls were fixed on some sort of axles and held together then 35.71% would be the upper limit.<hr /></blockquote>Sorry, but you lose me here. Regards, Dave <hr /></blockquote>
Dr Dave -- If the balls were "fixed" on axles that only allowed yy moovment (fullball impact here), ie allowed zero xx (sideways) moovment, then the max transfer would be 35.71% for any and all impacts fullball or not. And, gearing would be possible for fullball etc impacts (depending on exact spins etc).

But, in a "real" (fullball) impact, the OB is thrown sideways, and likewise the qball equally (but in the opposite direction). Thusly, the balltoball slippage is reduced by this throw(s). Thusly, u can (and do) get cases where the qball has more spin than the OB, and where impact hasnt finished (ie the balls are still touching), but the qball karnt give any more spin to the OB koz slippage haz fallen to zero.

Pause here -- What do u think ?? madMac.

Jal
01-10-2007, 07:51 PM
Mac,

Thanks for explaining the type of gearing you had in mind. I see what you meant by the 1A,B types being impossible in the cases we're discussing.

As far as your model exceedinng the 35.7% simple physics limit, I've had a few thoughts.

1) Maybe your program deals with the cloth interaction. The average forces here are of course very small compared to the ball/ball ones. But when slippage ends very early during impact, the ball/ball forces haven't had much time to build up, so the cloth has more of an effect; it opposes the throw action a little more. And when throw is inhibited, this pushes the numbers up toward 50% (at least in that direction). At the extreme, if throw was completely inhibited, you could only get gearing in your 1A sense, ie, a 50% transfer.

2) Perhaps your "friction squeeze" mechanism is at play. If you think this is the cause, perhaps you would explain it a little further. But I don't see this having a greater effect at smaller cueball spins.

3) I thought that maybe you might be tracking the changing moments of inertia of the balls as the flat spot develops. A reduction in them would result in an increased transfer, ie, 5/2 becomes something greater than 5/2. But this should have its greatest effect when gearing is achieved late in the impact (after the flat spot has done its thing).

Please tell me that your program includes the cloth.

I'm now thinking that by itself, the inelasticity doesn't affect the transfer, as you've been indicating. The fact is that no matter how the friction force evolves or is attenuated, the ratio of spin change to speed change remains the same (5/2), as long as the moment of inertia doesn't change. And this is what gives you the transfer percentage, barring additional forces (cloth).

If you would like to comment on any of this, or expand on your earlier thoughts....

<blockquote><font class="small">Quote cushioncrawler:</font><hr>....In my (our) impacts, the throw of the OB robs some of the effective slippage distance, in fact the reverse-throw of the qball likewize robs some slippage distance, ie a double dose of throw, and yet the force itself is unchanged (in my model), and when slippage (slowly) stops the friction force (abruptly) falls to zero allso. Thusly we can get more than 35.71%. If the 2 balls were fixed on some sort of axles and held together then 35.71% would be the upper limit....<hr /></blockquote>I think it's the opposite if I'm understanding you here Mac. The more the throw takes away from the surface speed, the less spin transfer percentage you get, because the spin transfer no longer has to do as big a job in reducing the surface speed. For ideal spheres, the apportionment of the task is determined by the moment of inertia, and is always in a 5/2 ratio, unless something suppresses either one.

If your program does treat the cloth, you should see an opposite trend when draw or topspin is applied. Here spin would be inhibited a little, but not throw.

Jim

cushioncrawler
01-10-2007, 07:56 PM
<blockquote><font class="small">Quote Jal:</font><hr> ....If you get the time, and when you're ready, can you give us some idea what things your model takes into account beyond the "simple physics".... <hr /></blockquote>
Jim -- I havnt included any non-simple physics in this here stuff, but i could have, have a look at this....

Throw iz made up of Throw and Sqeez. Sqeez iz a geometric sort of effect. During impact, the balls moov over a bit, ie due to friction throw. Now, as soon as the balltoball line moovs "off-line", u have the xx bit of the ordinary non-friction component of the impact contributing directly to the throw. As impact progresses, and as this off-line angle increases, this non-friction contribution becomes significant. My old calculations show that at slow speeds the Sqeez can increase the throw by 0.24%, and at hi-speed by 2.3%. Duznt sound like much, but its the thort that counts. I can send u my program if u are interested. When the balls finally part company, the balltoball angle has changed (from the initial balltoball angle of 00.00dg) by 0.03dg for the slow impact and by 0.33dg for the hi-speed impact -- this is a lot really. The softer the ball the more the Sqeez and the more the Sqeez-Angle, and hence the more the throw. Alltho, like i said, i didnt bother with any of this (non-simple-physics) in my current stuff.

There is one more sort of geometric effect that i think of, but which is definitely insignificant, but, as i say, its the thort that counts. Its like this....
When the OB is hit other than dead straight, the OB's trajectory is allways drawn as a straight line, but it never is. During impact, the balltoball line changes -- here i am talking about the angle, moreso than the pozzy. The first bit of the trajectory is allways a sort of S shape, after impact it is dead straight (depending on masse etc). The S shape is due to the fact that the OB duznt fly away in line with the final balltoball line, it allways splits the difference (between the initial and final balltoball line). What this meenz is that the OB's trajectory is the effective sum of all of the forces and their angles during the whole impact event. This means that, even if there is zero balltoball friction, during the first half of impact (nearnuff),the OB will be pushed say right of "the line", and during the second half of impact it will be pushed left of "the line". Hence, the OB follows an S trajectory during impact. Hence, the final straight bit of the trajectory never points to where the OB was initially sitting, it points a bit to one side. I might have calculated this "offset" -- its the sort of thing i like doing, the problem would be to find my work, but, its no big deal, here we are talking about say 0.1mm, but, like i say, its the thort that counts. madMac.

cushioncrawler
01-10-2007, 08:23 PM
<blockquote><font class="small">Quote Jal:</font><hr> Mac, Thanks for explaining the type of gearing you had in mind. I see what you meant by the 1A,B types being impossible in the cases we're discussing. As far as your model exceedinng the 35.7% simple physics limit, I've had a few thoughts.

1) Maybe your program deals with the cloth interaction. The average forces here are of course very small compared to the ball/ball ones. But when slippage ends very early during impact, the ball/ball forces haven't had much time to build up, so the cloth has more of an effect; it opposes the throw action a little more. And when throw is inhibited, this pushes the numbers up toward 50% (at least in that direction). At the extreme, if throw was completely inhibited, you could only get gearing in your 1A sense, ie, a 50% transfer.

2) Perhaps your "friction squeeze" mechanism is at play. If you think this is the cause, perhaps you would explain it a little further. But I don't see this having a greater effect at smaller cueball spins.

3) I thought that maybe you might be tracking the changing moments of inertia of the balls as the flat spot develops. A reduction in them would result in an increased transfer, ie, 5/2 becomes something greater than 5/2. But this should have its greatest effect when gearing is achieved late in the impact (after the flat spot has done its thing).

Please tell me that your program includes the cloth.

I'm now thinking that by itself, the inelasticity doesn't affect the transfer, as you've been indicating. The fact is that no matter how the friction force evolves or is attenuated, the ratio of spin change to speed change remains the same (5/2), as long as the moment of inertia doesn't change. And this is what gives you the transfer percentage, barring additional forces (cloth).

If you would like to comment on any of this, or expand on your earlier thoughts....

<blockquote><font class="small">Quote cushioncrawler:</font><hr>....In my (our) impacts, the throw of the OB robs some of the effective slippage distance, in fact the reverse-throw of the qball likewize robs some slippage distance, ie a double dose of throw, and yet the force itself is unchanged (in my model), and when slippage (slowly) stops the friction force (abruptly) falls to zero allso. Thusly we can get more than 35.71%. If the 2 balls were fixed on some sort of axles and held together then 35.71% would be the upper limit....<hr /></blockquote>I think it's the opposite if I'm understanding you here Mac. The more the throw takes away from the surface speed, the less spin transfer percentage you get, because the spin transfer no longer has to do as big a job in reducing the surface speed. For ideal spheres, the apportionment of the task is determined by the moment of inertia, and is always in a 5/2 ratio, unless something suppresses either one.

If your program does treat the cloth, you should see an opposite trend when draw or topspin is applied. Here spin would be inhibited a little, but not throw. Jim<hr /></blockquote>
Jim -- I see that our mails crossed in cyberspace. Here i am referring mainly to your query regarding Sqeez. I didnt realize that we had allready discussed Sqeez a long long time ago. Anyhow, my new posting probably sez enuff about Sqeez to answer your query -- tell me if it duznt, i might be able to add more info.

No, i didnt look into any cloth-effects etc, that sort of stuff comes into play too late to interest most of us i think, and is too practical (the old "pure mathematics" talking here). In fact, i suppose that the cloth-effect is itself a sort of chicken and egg sort of effect. What i mean is that when (if) we do throw tests to "measure" balltoball friction, the natural effect of the bedcloth, and the natural effect of the ball having to get out of its own footprint, all have an effect on our measurement, and hence are inherent in our figure, and hence shoodnt need a correction later, koz this would be a double correction, ie fixing something which iznt broke.

The effect of the changing radius on the balls effective inertia (ie due to the temporary flatspot), or more truely, the effect on the (frictional) torqs, -- i have thort of this sort of thing in years gone by, but i have never looked into it, i have allways been able to massage my figures well enuff without looking more closely at this sort of thing -- it must have a small effect, but no i didnt worry about it here.

No, its just as simple as i have been saying. If one simply imagines the slippage distance as being less due to throw, then this simply explains the less work done against friction, ie less energy loss, ie less heat loss. Hence, more energy (momentum, whatever) available to do good deeds. Some of the wordage i used in my posting to Dr Dave covers this some more. I'm happy to explain some more if u want. madMac.

Jal
01-10-2007, 11:59 PM
<blockquote><font class="small">Quote cushioncrawler:</font><hr>...When the OB is hit other than dead straight, the OB's trajectory is allways drawn as a straight line, but it never is. During impact, the balltoball line changes -- here i am talking about the angle, moreso than the pozzy. The first bit of the trajectory is allways a sort of S shape, after impact it is dead straight (depending on masse etc). The S shape is due to the fact that the OB duznt fly away in line with the final balltoball line, it allways splits the difference (between the initial and final balltoball line).<hr /></blockquote>I love it. For what it's worth, I also agree with it and your friction squeeze (which I knew about from earlier materials you sent to me). I'd be interested in your program, but I'll send you a PM since this is getting personal.


<blockquote><font class="small">Quote cushioncrawler:</font><hr>...No, its just as simple as i have been saying. If one simply imagines the slippage distance as being less due to throw, then this simply explains the less work done against friction, ie less energy loss, ie less heat loss. Hence, more energy (momentum, whatever) available to do good deeds. Some of the wordage i used in my posting to Dr Dave covers this some more. I'm happy to explain some more if u want. madMac. <hr /></blockquote>Mac, I'm sorry but I'm afraid I still don't see it. You're saying that the energy loss is less because of throw. But throw itself will produce energy loss. And regardless of any losses or gains, if the friction force reduces the surface speed to zero, then the moment of inertia dictates how the initial surface speed will be parceled out as spin and throw. This is in the ratio mentioned in my last post (5/2), and it's not obvious how you can get around it (without the special effects we've discussed). But maybe some further explication will help.

Pretty soon we should probably carry this on privately since we're really splitting hairs here.

Jim

cushioncrawler
01-11-2007, 12:50 AM
<blockquote><font class="small">Quote Jal:</font><hr> <blockquote><font class="small">Quote cushioncrawler:</font><hr>...No, its just as simple as i have been saying. If one simply imagines the slippage distance as being less due to throw, then this simply explains the less work done against friction, ie less energy loss, ie less heat loss. Hence, more energy (momentum, whatever) available to do good deeds. Some of the wordage i used in my posting to Dr Dave covers this some more. I'm happy to explain some more if u want. madMac. <hr /></blockquote>Mac, I'm sorry but I'm afraid I still don't see it. You're saying that the energy loss is less because of throw. But throw itself will produce energy loss. And regardless of any losses or gains, if the friction force reduces the surface speed to zero, then the moment of inertia dictates how the initial surface speed will be parceled out as spin and throw. This is in the ratio mentioned in my last post (5/2), and it's not obvious how you can get around it (without the special effects we've discussed). But maybe some further explication will help. Pretty soon we should probably carry this on privately since we're really splitting hairs here...<hr /></blockquote> Jim -- This all reminds me of that 16th century never-ending arguement between Newton and Bernoulli (names and years probably wrong here) where in the end it was found (by others) that one was talking about energy and the other was talking about momentum (alltho i think that these two words werent around in them days).

I agree that the 5/2 ratio applies to the OB's spin/throw ratio, throo-out the whole impact event, and at the end, allways. But the 2/7ths loss ratio, due to slippage heat loss, is only correct if frictional intercourse is allowed to reach a climax, the way i see it. In these fullball impacts, the throw(s) rear their ugly heads and interupt the 2/7th loss. Sorry, must go now, dinner is ready, I'll be back with more later. madMac.

dr_dave
01-11-2007, 07:42 AM
<blockquote><font class="small">Quote cushioncrawler:</font><hr>Most of my (our) work on balltoball friction is based mainly on the outcome of throw tests -- the throw tests allready have an inherent dependence on e. I guess that if we used a "pure" or "direct" sort of value for balltoball friction, then an allowance for e would be necessary to accurately predict spin transfer and throw.<hr /></blockquote>You make a good point here. The friction model is based on throw experiments, so care must be taken to make sure friction and inelasticity effects are not muddled. However, I think if Equation 8 from TP A.5 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/new/TP_A-5.pdf) is used with e=0.93 in Equation 6 of TP A.14 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/new/TP_A-14.pdf), then everything would be proper. But this won't affect the results very much ... it certainly won't affect any of the trends, which are the most important conclusions. Also, the 35.71% would still hold because this result is independent of fiction (see Equations 8-14 and the corresponding justifications in TP A.14 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/new/TP_A-14.pdf)).

Thanks again for helping to keep me honest and thorough,
Dave

dr_dave
01-11-2007, 07:48 AM
<blockquote><font class="small">Quote cushioncrawler:</font><hr>If the balls were "fixed" on axles that only allowed yy moovment (fullball impact here), ie allowed zero xx (sideways) moovment, then the max transfer would be 35.71% for any and all impacts fullball or not. And, gearing would be possible for fullball etc impacts (depending on exact spins etc).

But, in a "real" (fullball) impact, the OB is thrown sideways, and likewise the qball equally (but in the opposite direction). Thusly, the balltoball slippage is reduced by this throw(s). Thusly, u can (and do) get cases where the qball has more spin than the OB, and where impact hasnt finished (ie the balls are still touching), but the qball karnt give any more spin to the OB koz slippage haz fallen to zero.<hr /></blockquote>Thank you for the clarification. This effect is accounted for in Equations 8-15 in TP A.14 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/new/TP_A-14.pdf). This is exactly the effect that leads to the 35.71% spin transfer number in TP A.27 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/new/TP_A-27.pdf).

Regards,
Dave

cushioncrawler
01-11-2007, 05:02 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote cushioncrawler:</font><hr>If the balls were "fixed" on axles that only allowed yy moovment (fullball impact here), ie allowed zero xx (sideways) moovment, then the max transfer would be 35.71% for any and all impacts fullball or not. And, gearing would be possible for fullball etc impacts (depending on exact spins etc).

But, in a "real" (fullball) impact, the OB is thrown sideways, and likewise the qball equally (but in the opposite direction). Thusly, the balltoball slippage is reduced by this throw(s). Thusly, u can (and do) get cases where the qball has more spin than the OB, and where impact hasnt finished (ie the balls are still touching), but the qball karnt give any more spin to the OB koz slippage haz fallen to zero.<hr /></blockquote>Thank you for the clarification. This effect is accounted for in Equations 8-15 in TP A.14 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/new/TP_A-14.pdf). This is exactly the effect that leads to the 35.71% spin transfer number in TP A.27 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/new/TP_A-27.pdf). Regards,Dave <hr /></blockquote>
Dr Dave -- Yes, u are correct, TPA14 duz include an allowance for loss of balltoball slippage due to throw(s) -- my apology. This is Type 2B gearing (my posting to Jim refers).

TPA27 is very relevent to our discussions -- it shows spin transfer rather than throw, alltho of course throw and spin are related. Here, i probably owe u another apology, koz u do in fact nominate 35.71% as being the max possible transfer in the limiting case, which means that we (u &amp; me &amp; Jim) were all pretty much in agreement the whole time. The graph at the bottom of page 4 is most relevant.

I think that where we start to drift apart is perhaps due to a confusion in terminology. For instance, i might agree that the max possible spin rate (SR) (ie rps or m/s) is transferred at the limiting case and allso that here it is 35.71%, but what i have been talking about is the spin-transfer-rate (STR) (%). I have been saying (meaning) that the STR can be more than 35.71% (i said 37.52%), even tho the SR at this point might be (is) a very low figure(rps). But, here again, there is a slight chance that we are in agreement, koz, at the very end of TPA27 u mention that the spin transfer can be as high as 37.5%. Is this a typo, or were u miles ahead of me (and Jim).

The gist of my claim, is that the left hand end of the graph at the bottom of page 4 of TPA27 should rise higher (towards 38%) as the percentage english (PE) approaches zero%.

The reason(s) behind this seemingly impossible theory is (are) the gist of much of what i have been saying in posts to yourself and Jim in previous days. madMac.

cushioncrawler
01-11-2007, 05:46 PM
<blockquote><font class="small">Quote Jal:</font><hr>...Mac, I'm sorry but I'm afraid I still don't see it. You're saying that the energy loss is less because of throw. But throw itself will produce energy loss.... <hr /></blockquote> Jim -- Carrying on from before -- Yes throw itself robs energy, but not as much as u might think. The momentum of the throw(s) is only say 0.06 times the momentum of the drive, and, as (i think) momentum is a vector, it is the momentum of the hypotenuse that would need to be used to work out the energy "lost", rather than adding driveM to throwM.

Like i said, one shoodnt get too transfixed with the 2/7ths loss due to heat. This 2/7ths only occurs for one case for a fullball impact, ie the case where slippage stops at the same time that impact stops. We are all in agreement that the spin transfer percentage drops away when the qball has "too much" initial spin, but i am having a hard time convincing all that, in a similar way, the % rises (a little) when the qball has "too little" initial spin, ie the flat bit of the graph(s) at the bottom of page 4 of TPA27 shoodnt be flat.

I am beginning to think that likewize this 2/7ths only occurs for non-fullball impacts when (if) slippage stops at the same time that impact stops. I will look into this another day.

Anyhow, i will improov my model by using smaller steps or something, and see if my 37.52% holds up. madMac.

Jal
01-11-2007, 08:48 PM
<blockquote><font class="small">Quote cushioncrawler:</font><hr> Jim -- Carrying on from before -- Yes throw itself robs energy, but not as much as u might think. The momentum of the throw(s) is only say 0.06 times the momentum of the drive, and, as (i think) momentum is a vector, it is the momentum of the hypotenuse that would need to be used to work out the energy "lost", rather than adding driveM to throwM.

Like i said, one shoodnt get too transfixed with the 2/7ths loss due to heat. This 2/7ths only occurs for one case for a fullball impact, ie the case where slippage stops at the same time that impact stops. We are all in agreement that the spin transfer percentage drops away when the qball has "too much" initial spin, but i am having a hard time convincing all that, in a similar way, the % rises (a little) when the qball has "too little" initial spin, ie the flat bit of the graph(s) at the bottom of page 4 of TPA27 shoodnt be flat.<hr /></blockquote>Hi Mac,

If we're coming to an agreement that the energy loss is not important, I'll be happy to sign on to that. The take up of 2/7'ths of the surface speed to throw is not necessarily associated with any energy loss. You could conceive of it happening without this.

Consider that all of this governed by two relations:

Ft = m(d_v)

RFt = I(d_w)

where F is the time averaged friction force. It doesn't matter what happens to it or t as result of energy loss, or whatever. When you divide one equation by the other, the relation between the throw velocity, d_v, and the spin change, d_w, is completely determined by the moment of inertia, I, and moment arm R (whch I neglected to mention earlier). As I see it, the only way you could achieve a transfer beyond 35.71% is if one of the following were to occur:

1)The initial relative surface speed is increased in some way. (I looked further into "friction squeeze", and for a full ball hit, its effect is to reduce it.)

2)The moment(s) of inertia are decreased (without decreasing the moment arms so as to offset this).

3)The moment arm R is increased (without increasing I so as to offset it).

4)Throw (d_v) is inhibited in some way.

I'm willing to accept your 37.5% figure (not that it matters), but I have to say that you won't convince me unles you can demonstrate that one or more of the above is at work in your model.

<blockquote><font class="small">Quote cushioncrawler:</font><hr>I am beginning to think that likewize this 2/7ths only occurs for non-fullball impacts when (if) slippage stops at the same time that impact stops.<hr /></blockquote>The above equations, without the caveats, say that 2/7'ths of the change in the relative surface speed will be taken up as throw of the two balls, the remaining 5/7'ths as spin changes (1/7'th and 5/14'th respectively per ball). This is true whether or not the balls reach the rolling state. When they do, then 5/14'ths of all of it is taken up as OB spin.

Your model may very well be reporting some of the subtle tweaks that actually take place, but it would be nice if you could identify which one(s).

Jim

cushioncrawler
01-12-2007, 02:58 AM
<blockquote><font class="small">Quote madMac:</font><hr>...Jim -- Carrying on from before -- Yes throw itself robs energy, but not as much as u might think. The momentum of the throw(s) is only say 0.06 times the momentum of the drive, and, as (i think) momentum is a vector, it is the momentum of the hypotenuse that would need to be used to work out the energy "lost", rather than adding driveM to throwM..... <hr /></blockquote>
Jim -- I led u astray here above. I just checked the energy balance due to throw and spin transfer and loss to slippage heat, and, the only way that i could get the energy to balance was to treat the throw velocity energy of the OB and qball directly, ie i couldnt use the hypotenuse velocity, ie the XY velocity. Shows that i dont understand vectors and scalars.

Still havnt found anything (else) wrong with my work and ideas. In fact i am now looking at a slightly different slant on things that i think might be convincing -- more later. madMac.

Qtec
01-12-2007, 08:26 AM
Lets say, hypothetically of course /ccboard/images/graemlins/grin.gif', that I understand everything thats been said in this thread.
How do I apply this info to my game to make me a better player?

Qtec......thinks its time for a non-pool related techie forum . /ccboard/images/graemlins/confused.gif /ccboard/images/graemlins/grin.gif

dr_dave
01-12-2007, 09:23 AM
<blockquote><font class="small">Quote cushioncrawler:</font><hr>Yes, u are correct, TPA14 duz include an allowance for loss of balltoball slippage due to throw(s) -- my apology. This is Type 2B gearing (my posting to Jim refers).

TPA27 is very relevent to our discussions -- it shows spin transfer rather than throw, alltho of course throw and spin are related. Here, i probably owe u another apology, koz u do in fact nominate 35.71% as being the max possible transfer in the limiting case, which means that we (u &amp; me &amp; Jim) were all pretty much in agreement the whole time. The graph at the bottom of page 4 is most relevant.<hr /></blockquote>
madMac,

No need for apologies. You guys helped me find some errors, and my level of understanding is much better now than it was before you started questioning some of the results. That's what this forum is all about ... people learning from each other.

Regards,
Dave

dr_dave
01-12-2007, 09:33 AM
<blockquote><font class="small">Quote cushioncrawler:</font><hr>I think that where we start to drift apart is perhaps due to a confusion in terminology. For instance, i might agree that the max possible spin rate (SR) (ie rps or m/s) is transferred at the limiting case and allso that here it is 35.71%, but what i have been talking about is the spin-transfer-rate (STR) (%). I have been saying (meaning) that the STR can be more than 35.71% (i said 37.52%), even tho the SR at this point might be (is) a very low figure(rps).<hr /></blockquote>The numbers and graphs reported in TP A.27 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/new/TP_A-27.pdf) deal with spin transfer percentage (STP), which is the ratio of the transferred spin rate to the initial CB spin rate. I don't think the confusion is with the terminology.

<blockquote><font class="small">Quote cushioncrawler:</font><hr>But, here again, there is a slight chance that we are in agreement, koz, at the very end of TPA27 u mention that the spin transfer can be as high as 37.5%. Is this a typo, or were u miles ahead of me (and Jim).<hr /></blockquote>Sorry, that was a typo. It's been fixed. The largest the STP can ever be (for any spin rates, speeds, ball elasticity, energy loss, friction, etc.) is 35.71%!

Regards,
Dave

dr_dave
01-12-2007, 09:39 AM
<blockquote><font class="small">Quote Jal:</font><hr>Maybe looking at inelasticity and the conservations laws may swing things in favor of his slightly larger numbbers? I'll try to take a look at this later, but be my guest. /ccboard/images/graemlins/smile.gif<hr /></blockquote>Jim,

Since it was relatively straightforward to include, I went ahead and did it (see Equation 1 in TP A.27 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/new/TP_A-27.pdf)). The limit for the maximum possible spin transfer percentage is still 35.71% (see Equation 6). For typical (non ideal) pool balls, the actual limiting value is closer to 34.5% (see Equation 7).

Regards,
Dave

dr_dave
01-12-2007, 10:02 AM
<blockquote><font class="small">Quote Qtec:</font><hr>Lets say, hypothetically of course /ccboard/images/graemlins/grin.gif', that I understand everything thats been said in this thread.
How do I apply this info to my game to make me a better player?<hr /></blockquote>
First of all, I agree that much of this thread is of little interest to many people on this forum. Also, the purpose of detailed physics understanding isn't always to provide info that directly helps people improve their game. The purpose here was to help strengthen the understanding of the physics behind throw and spin transfer. To me that is very useful, because I have used this physics to back up and expand on knowledge concerning throw. And I think some of this knowledge is useful in game situations. Some people have this "knowledge" already from many years of experience, which has helped create "intuition." However, for many people, the knowledge can help speed the learning process and serve as reinforcement for their intuition.

For a summary of many of the conclusions from the throw and spin tranfer analyses that are useful in one's game, see the examples and summaries in my throw-related instructional articles:
August '06 through March '07 (http://www.engr.colostate.edu/~dga/pool/bd_articles/index.html), with more to come.

<blockquote><font class="small">Quote Qtec:</font><hr>Qtec......thinks its time for a non-pool related techie forum . /ccboard/images/graemlins/confused.gif /ccboard/images/graemlins/grin.gif <hr /></blockquote>
/ccboard/images/graemlins/confused.gif
I think there's room enough in this forum for everybody: the players (all levels), newbies, the cue makers, the instructors, the instructional authors, the socializers, enthusiasts, the old-timers, and yes ... even the techies.

Regards,
Dave (the player, enthusiast, instructional author, socializer, and sometimes ... a proud techie).

Chopstick
01-12-2007, 10:32 AM
<blockquote><font class="small">Quote Qtec:</font><hr> Lets say, hypothetically of course /ccboard/images/graemlins/grin.gif', that I understand everything thats been said in this thread.
How do I apply this info to my game to make me a better player?

Qtec......thinks its time for a non-pool related techie forum . /ccboard/images/graemlins/confused.gif /ccboard/images/graemlins/grin.gif <hr /></blockquote>


Would all of this apply if you were playing in a no-spin zone? /ccboard/images/graemlins/laugh.gif

Qtec
01-12-2007, 11:18 AM
[ QUOTE ]
First of all, I agree that much of this thread is of little interest to many people on this forum. <hr /></blockquote>

This thread belongs on a physics forum. Its got very little to do with pool. You say it yourself, this 'knowledge'isn't going to help one single reader make one single ball.!
Any info that helps people play better is more than welcolme on this forum, at least that is my observation, but telling someone that they will get % 35.72 spin transfer.............. /ccboard/images/graemlins/confused.gif LOL ??????????? % 35.72 of an unknown? /ccboard/images/graemlins/grin.gif


Pool is a very SIMPLE game to play - its just very difficult to play it well. There is no mystery, no secret aiming system, no secret knowledge, no equations ....etc.

You might know your physics Dave but do you know ANYTHING about Pool? Pool is a game between 2 individuals, not about who has the better understanding of physics.

IMO, you have always approached the game from a scientific view point and not as a player.

I think your site is great and a good reference point but thats it. IMO there is nothing on your site that will make a bad player good.
Thats why you have instructors.

The REAL good info will probably not be heard or ignored on this forum. The best info is certainly NOT the crap that the techies dish out.

Nothing personal Dave but I,ve had enouigh of this crap.

The acid test in instruction is about being able to back up what you teach. I once wanted to teach golf but my handicap wasn't low enough.
Q.............

dr_dave
01-12-2007, 11:40 AM
<blockquote><font class="small">Quote Qtec:</font><hr>This thread belongs on a physics forum<hr /></blockquote>Maybe, but not everything in the thread is just physics.

<blockquote><font class="small">Quote Qtec:</font><hr>You might know your physics Dave but do you know ANYTHING about Pool? Pool is a game between 2 individuals, not about who has the better understanding of physics.<hr /></blockquote>Is your only point here to try to insult me? If so, it didn't work. I've played in leagues and some small tournaments (and won a couple). I can run racks of 9-ball and 8-ball (not every time, but often enough to hope to do it every time). I have several pool buddies I play with periodically. My friends and I all have pool tables in our homes. I think about pool pretty much every day. I wrote a book on pool. I write monthly instructional articles for Billiards Digest on pool. Is that enough to convince you that I care about more than just physics?

<blockquote><font class="small">Quote Qtec:</font><hr>I think your site is great and a good reference point but thats it. IMO there is nothing on your site that will make a bad player good.<hr /></blockquote>I agree. But I think there's lots there to help make a player (any level) better.

<blockquote><font class="small">Quote Qtec:</font><hr>Thats why you have instructors.<hr /></blockquote>I agree that instructors can be instrumental in a player's improvement.

<blockquote><font class="small">Quote Qtec:</font><hr>Nothing personal Dave but I,ve had enouigh of this crap.<hr /></blockquote>Then stop reading it.

Respectfully,
Dave

bsmutz
01-12-2007, 12:39 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> Then stop reading it.

Respectfully,
Dave <hr /></blockquote>
I wholeheartedly concur. This IS a POOL forum and any discussion that has anything to do with POOL should be permissible. If the subject of a series of posts is boring to you or makes you sick, don't frigging read it. It obviously is very interesting to some people given the length of this thread. Your opinion would have been better kept to yourself, IMO.

dr_dave
01-12-2007, 01:14 PM
<blockquote><font class="small">Quote bsmutz:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> Then stop reading it.

Respectfully,
Dave <hr /></blockquote>
I wholeheartedly concur. This IS a POOL forum and any discussion that has anything to do with POOL should be permissible. If the subject of a series of posts is boring to you or makes you sick, don't frigging read it. It obviously is very interesting to some people given the length of this thread. Your opinion would have been better kept to yourself, IMO. <hr /></blockquote>

Thank you. I'm glad there are others out there (at least one, anyway) that agree.

Regards,
Dave

JPB
01-12-2007, 01:44 PM
Qtec your post is out of line IMO.

cushioncrawler
01-12-2007, 03:58 PM
Dr Dave. Me, myself, i have learnt a few techie things off u &amp; this forum which i think have helped my game. The main one was perhaps that throw is less at hi-speed. I allways thort that missing a hi-speed pot (missing too thin usually) was mainly a problem with my eyes and (hi-speed) stroke, but now i make the needed allowance and let it rip. Dont know how many hours i wasted (in praktis) trying to fix something that wasnt broke.

Regarding your videos. Would it be possible to show how a little bit of outside english can actually increase the throw. This might be difficult. Perhaps if u do a setup where u drive the OB square to the cushion, and the extra angle that it comes back at (compared to zero english) would help proov the effect. Dont know, its not a big effect and it would be very frustrating.

There is some truth to what Q sez. On the other hand, nowaday, if a schoolkid googles "ball impact friction energy restitution" etc, he/she will often get directly into the Billiards Digest forum, and possible learn a few techie things. I know that there are a few websites out there that have good stuff (and bad stuff) on them, and there are math forums and physics forums, but most of these guys are not billiards-techies.

I have often seen bloggs etc where some schoolkid etc is asking for help regarding looking closely into some techie balltoball thing, and the kid is advised that it carnt be done (eg creating a computer program that mimics real balls, or at least helps to explain and predict what happens), when i know that i have allready done it (eg made a program) myself. Likewise, i see kids being given encouragement to do something that i know is next to impossible (i shood stick my nose in their bizness, but i dont). madMac.

dr_dave
01-12-2007, 04:13 PM
<blockquote><font class="small">Quote cushioncrawler:</font><hr> Dr Dave. Me, myself, i have learnt a few techie things off u &amp; this forum which i think have helped my game. The main one was perhaps that throw is less at hi-speed. I allways thort that missing a hi-speed pot (missing too thin usually) was mainly a problem with my eyes and (hi-speed) stroke, but now i make the needed allowance and let it rip. Dont know how many hours i wasted (in praktis) trying to fix something that wasnt broke.<hr /></blockquote>Thank you for sharing this testimonial. All of the insight I've gained this last 8 months with throw has also made me more aware of stuff that happens at the table. I think I miss less shots as a result. I certainly now know why I have missed some shots I thought I should have made.

<blockquote><font class="small">Quote cushioncrawler:</font><hr>Regarding your videos. Would it be possible to show how a little bit of outside english can actually increase the throw. This might be difficult. Perhaps if u do a setup where u drive the OB square to the cushion, and the extra angle that it comes back at (compared to zero english) would help proov the effect. Dont know, its not a big effect and it would be very frustrating.<hr /></blockquote>I agree that this would be difficult to show, and I already have enough on my list.

<blockquote><font class="small">Quote cushioncrawler:</font><hr>There is some truth to what Q sez. On the other hand, nowaday, if a schoolkid googles "ball impact friction energy restitution" etc, he/she will often get directly into the Billiards Digest forum, and possible learn a few techie things. I know that there are a few websites out there that have good stuff (and bad stuff) on them, and there are math forums and physics forums, but most of these guys are not billiards-techies.

I have often seen bloggs etc where some schoolkid etc is asking for help regarding looking closely into some techie balltoball thing, and the kid is advised that it carnt be done (eg creating a computer program that mimics real balls, or at least helps to explain and predict what happens), when i know that i have allready done it (eg made a program) myself. Likewise, i see kids being given encouragement to do something that i know is next to impossible (i shood stick my nose in their bizness, but i dont). madMac. <hr /></blockquote>Thank you for sharing your thoughts.

Dave

Jal
01-12-2007, 06:40 PM
<blockquote><font class="small">Quote dr_dave:</font><hr>...Since it was relatively straightforward to include, I went ahead and did it (see Equation 1 in TP A.27 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/new/TP_A-27.pdf)). The limit for the maximum possible spin transfer percentage is still 35.71% (see Equation 6). For typical (non ideal) pool balls, the actual limiting value is closer to 34.5% (see Equation 7).<hr /></blockquote>Thank you Dr. Dave. (Better you than me.) And thank you for not stonewalling it or browbeating us earlier. It's very much appreciated. (And also for giving Qtec his come-uppins - that I really enjoyed. /ccboard/images/graemlins/smirk.gif And while I'm at it, to a couple of the other posters for expressing approval or at least toleration of these technical posts.)

Another thing which I believe reduces the transfer is Mac's "friction squeeze". I have the formula but haven't done any calculations yet. But conceptually, the initial tangent line is rotated a little during imapct because of the finite compression time and the mutual throw velocities. This gives the cueball a component of velocity along the average direction of the tangent line, and it opposes and diminishes the effective initial surface speed due to the spin alone. This, if true, should happend at any cut angle with any spin, but according to what Mac has calculated, the effect should be very small. As he says, it's the thought that counts.

I'm wondering if we're not stonewalling him. He's been invoking energy losses in his posts, while I've been saying that they're irrelevant. In fact, I said that all of this can happen without any losses (from looking at other situations). However, when you add up the post-impact energies (translational and spin), they don't come very close to the pre-impact values. I think I'm forgetting some some basic physics here, and will look at it further myself, but if you or Mac or anyone have some thoughts...

Jim

dr_dave
01-12-2007, 07:37 PM
<blockquote><font class="small">Quote Jal:</font><hr>Thank you ... for giving Qtec his come-uppins - that I really enjoyed. /ccboard/images/graemlins/smirk.gif And while I'm at it, to a couple of the other posters for expressing approval or at least toleration of these technical posts.<hr /></blockquote>
It was my pleasure.

Your thanks to others is well stated. Tolerance is indeed a great virtue.

Regards and Happy New Year,
Dave

dr_dave
01-12-2007, 07:41 PM
<blockquote><font class="small">Quote Jal:</font><hr>Another thing which I believe reduces the transfer is Mac's "friction squeeze". I have the formula but haven't done any calculations yet. But conceptually, the initial tangent line is rotated a little during imapct because of the finite compression time and the mutual throw velocities. This gives the cueball a component of velocity along the average direction of the tangent line, and it opposes and diminishes the effective initial surface speed due to the spin alone. This, if true, should happend at any cut angle with any spin, but according to what Mac has calculated, the effect should be very small. As he says, it's the thought that counts.<hr /></blockquote>Thank you for sharing that. I agree with the bottom line on this one: it's probably just the thought that counts ... the effect is tiny for pool balls.

Regards,
Dave

dr_dave
01-12-2007, 07:56 PM
<blockquote><font class="small">Quote Jal:</font><hr>when you add up the post-impact energies (translational and spin), they don't come very close to the pre-impact values. I think I'm forgetting some some basic physics here, and will look at it further myself, but if you or Mac or anyone have some thoughts...<hr /></blockquote>
Jim,

I would expect there to be significant energy loss due to the friction and relative surface motion during impact ... not to mention the losses due to the coefficient of restitution. The beauty of the impulse-momentum-vector-based calculations is that the kinematics all works out (i.e., we automatically get the translational and angular velocities of both balls) without having to do a bunch of scalar-based energy balances (from which it is difficult to extract ball vector motion).

Regards,
Dave

PS: I don't mean to stonewall madMac or you with the energy stuff. Personally, I just don't see how it would add much to the conclusions already stated.

PS: Thanks again to you and madMac for helping find and fix all of my errors. I was a little sloppy with this whole spin transfer business.

Jal
01-13-2007, 08:12 AM
<blockquote><font class="small">Quote cushioncrawler:</font><hr>
Jim -- I led u astray here above. I just checked the energy balance due to throw and spin transfer and loss to slippage heat, and, the only way that i could get the energy to balance was to treat the throw velocity energy of the OB and qball directly, ie i couldnt use the hypotenuse velocity, ie the XY velocity. Shows that i dont understand vectors and scalars.

Still havnt found anything (else) wrong with my work and ideas. In fact i am now looking at a slightly different slant on things that i think might be convincing -- more later. madMac. <hr /></blockquote>You didn't lead me astray, I did that myself. I've been confused over what you've been saying because I've been implicity assuming that energy is conserved, since I didn't see how energy losses we're being introduced into the math picture. Very dumb ((they're introduced when you assign values for the acting forces not derived from the conservation laws!) and I'm sorry for not catching on to your points sooner.

So I went back and reread your posts and understand your argument better. But the impulse/momentum treatment still seems very convincing that the 35.71% limit holds, unless some of the mechanisms mentioned earlier are involved. Since mechanical energy isn't conserved, I don't think it can tell you much about the end state. But if you've come up with what might be a more persuasive version...

By the way, you stated the 35.71% figure first. And if it wasn't for your pushing of the issue, a number of us would still have some wrong ideas about it. Thanks Mac and I look forward to any more thoughts you might have.

Jim

bradb
01-17-2007, 10:14 AM
Over the years I have learned to use as little spin as possible on a bank shot. I've been playing snooker and on that table a bank is a crap shoot, so your bank cuing has to be as simple as possible. Of course there are times when spin is needed to bank a ball that is not presenting a good angle but basically for a bank every stroke is the same.
Since I have switched to the 9' table and the fast cloth I have noticed quite a difference in banking. For a side bank (of a ball near the opposite side pocket) should the ball just miss shy of the pocket, it will angle back to the other side pocket for a double. In fact many players use this technique for better position play but usually its just a happy accident. How frustrating though to find that on simonis the ball will not continue its angle but return to where it rebounded? It cost me many a game until I adjusted to allow for that. It must be in the make up of the rail, but I can't figure out why?

dr_dave
01-17-2007, 10:57 AM
<blockquote><font class="small">Quote bradb:</font><hr> Over the years I have learned to use as little spin as possible on a bank shot.<hr /></blockquote>I think that most people would agree that this is good advice in general. However, one should be aware of the effects. Sometimes the spin can help you make a bank shot (e.g., see NV A.21 (http://www.engr.colostate.edu/~dga/pool/normal_videos/new/NVA-21.htm)). Also, with bank shots with a cut angle, collision-induced throw (CIT) imparts spin to the object ball. If you don't account for this spin with your aim, you will miss many bank shots.

Regards,
Dave

dr_dave
01-17-2007, 11:01 AM
<blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote bradb:</font><hr> Over the years I have learned to use as little spin as possible on a bank shot.<hr /></blockquote>I think that most people would agree that this is good advice in general. However, one should be aware of the effects. Sometimes the spin can help you make a bank shot (e.g., see NV A.21 (http://www.engr.colostate.edu/~dga/pool/normal_videos/new/NVA-21.htm)). Also, with bank shots with a cut angle, collision-induced throw (CIT) imparts spin to the object ball. If you don't account for this spin with your aim, you will miss many bank shots.<hr /></blockquote>FYI, video demos of the cut angle effect can be found in NV 6.12 (http://www.engr.colostate.edu/~dga/pool/normal_videos/NV6-12.htm) and NV 6.13 (http://www.engr.colostate.edu/~dga/pool/normal_videos/NV6-13.htm).

Regards,
Dave

bradb
01-17-2007, 01:29 PM
I understand what you are saying in to regards of how much the cut will effect the rebound, But the simonis cloth banks differently than the napped snooker cloth? I was very good at banking on the snooker table, now I feel like I'm starting all over again. The bank I described has the object ball losing its angle on the second rebound. My guess is the fast cloth imparts much more spin on the ball so the angle that got me to the other side is killed should it have to return. If thats the case it makes a double bank almost impossible to gauge.

Deeman3
01-17-2007, 01:42 PM
Cornerman and I actually had a conversation about this with Jerry Breseith at Derby City the other day. We were talking about how new cloth makes the angle open and the ball go long. I also remember how old timers claimed that the new simonis (made after the 1050's) would not keep spin well off the third cushion.

As your cloth gets broken in, perhaps it will react more like you expect. However, I would not ever expect it to replicate heavy napped snooker cloth.

DeeMan

Cornerman
01-17-2007, 03:24 PM
<blockquote><font class="small">Quote Deeman3:</font><hr>
As your cloth gets broken in, perhaps it will react more like you expect. However, I would not ever expect it to replicate heavy napped snooker cloth.

DeeMan <hr /></blockquote>Nor would I expect it to replicate the flat-face snooker cushions.

Discussions of banks on snooker tables and pool tables are two entirely different animals.

Fred

Deeman3
01-17-2007, 03:50 PM
Very Good Point.

DeeMan

bradb
01-17-2007, 04:41 PM
Yes, I was wondering if the different rail is a factor also. But I think its mostly the weave that effects the ball so drastically.
I never expected it to play exactly like a snooker table but little did i know how much the difference would be.

Thanks for the info. I'll just adapt and hope it smooths out as mentioned.
-Brad

Chopstick
01-18-2007, 11:07 AM
<blockquote><font class="small">Quote dr_dave:</font><hr>

The beauty of the impulse-momentum-vector-based calculations is that the kinematics all works out (i.e., we automatically get the translational and angular velocities of both balls) without having to do a bunch of scalar-based energy balances (from which it is difficult to extract ball vector motion).

<hr /></blockquote>

Well Dr. Dave that is one hell of a sentence. /ccboard/images/graemlins/laugh.gif

I don't have the background to understand all of what you guys are talking about but I do think that the interchange of ideas between scientists is important and contributes to the overall understanding of the game. Some say it is of no use. I disagree. For generations knowledge of pool has been handed down by word of mouth. There are a lot of myths and wives tales about how things work. The work you guys do separates the myth from reality and provides us all with a better foundation for development of our games.

As far as not using an engineering principle in a game, that's nonsense. Spiderman will definitely throw a move on ya.

dr_dave
01-18-2007, 11:30 AM
<blockquote><font class="small">Quote Chopstick:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr>The beauty of the impulse-momentum-vector-based calculations is that the kinematics all works out (i.e., we automatically get the translational and angular velocities of both balls) without having to do a bunch of scalar-based energy balances (from which it is difficult to extract ball vector motion).<hr /></blockquote>Well Dr. Dave that is one hell of a sentence. /ccboard/images/graemlins/laugh.gif<hr /></blockquote>You got me on that one; but, in my defense, it was really directed at only a small set of people on the forum.

<blockquote><font class="small">Quote Chopstick:</font><hr>I don't have the background to understand all of what you guys are talking about but I do think that the interchange of ideas between scientists is important and contributes to the overall understanding of the game. Some say it is of no use. I disagree. For generations knowledge of pool has been handed down by word of mouth. There are a lot of myths and wives tales about how things work. The work you guys do separates the myth from reality and provides us all with a better foundation for development of our games.

As far as not using an engineering principle in a game, that's nonsense. Spiderman will definitely throw a move on ya.<hr /></blockquote>
Thank you for the tolerance and support,
Dave

Deeman3
01-18-2007, 11:48 AM
<blockquote><font class="small">Quote Chopstick:</font><hr> As far as not using an engineering principle in a game, that's nonsense. Spiderman will definitely throw a move on ya. <hr /></blockquote>

<font color="blue"> That he will! However, you have been known to throw a move or two on people yourself!
/ccboard/images/graemlins/grin.gif
</font color>

DeeMan
Pettypoint, later this year, you and me with lazer sabers from ten paces..... /ccboard/images/graemlins/cool.gif

SPetty
01-18-2007, 07:21 PM
<blockquote><font class="small">Quote Deeman3:</font><hr>Pettypoint, later this year, you and me with lazer sabers from ten paces..... /ccboard/images/graemlins/cool.gif <hr /></blockquote>I'm there! Just name the time! Spiderman and I will be doing some damage in Vegas this year as BCA Scotch Doubles partners!!!

Deeman3
01-19-2007, 07:06 AM
<blockquote><font class="small">Quote SPetty:</font><hr> <blockquote><font class="small">Quote Deeman3:</font><hr>Pettypoint, later this year, you and me with lazer sabers from ten paces..... /ccboard/images/graemlins/cool.gif <hr /></blockquote>I'm there! Just name the time! Spiderman and I will be doing some damage in Vegas this year as BCA Scotch Doubles partners!!! <hr /></blockquote>

<font color="blue"> Spiderman,

That lucky Devil! He always gets the good partner. Do us a favor and carry him. I know he will be pretending to call the shots but we know who will come with the big shot when it counts.

Best of luck and shooting to you two. We will be putting the hex on your opponents from afar... /ccboard/images/graemlins/grin.gif</font color>

DeeMan
I miss SPetty.....

Chopstick
01-19-2007, 09:27 AM
<blockquote><font class="small">Quote Deeman3:</font><hr>
DeeMan
Pettypoint, later this year, you and me with lazer sabers from ten paces..... /ccboard/images/graemlins/cool.gif <hr /></blockquote>

That reminds me, I never did get me one of them green lasers. Where did you get yours?

I've got plenty of vacation this year. We should do it. People down here don't even know what one pocket is.

Deeman3
01-19-2007, 10:08 AM
I got mine off a web-site but it's been so long I don't remember. I think I did a search for Green Laser. I have not, however, forced any airplanes to the ground as of yet. /ccboard/images/graemlins/smirk.gif

I'm all for a PettyPoint Gathering. But as I just got back from Derby City I may need to wait a couple of months before escaping again.

DeeMan

DeeMan

caedos
01-20-2007, 12:32 PM
I'm replying to this one to make sure it shows up in Dave's e-mail queue.

I personally welcome the technical threads, even though the analysis as a whole oftentimes doesn't give me anything to work with personally when I play or teach. In fact, it often gives me 'tired head' looking for something of interest buried in the semantics of formulas and energy relationships. A piece buried in the analysis can be useful, or the rare contribution or observation I can add to the discussion. What I would like to see more of are the results in simple English guidelines that I can teach to many people and use as a player. Dr.Jewett has been great at putting experiments anyone can do in his BD articles over the years. Dr.Dave had a good three piece checklist for player reference towards the end of his Nov.'06 BD article (pages 34-35). [Dave -- a word I might add to that list is in #1 change "hitting the center of that cue ball;" to "hitting the vertical center of that cue ball;".]
The end result of threads like this is that the people we trust with the science of our sport get a good resource to add to their work and help validate things that do and don't work. The benefit for the rest of us are the tidbits we do understand, to give confidence in applying the knowledge in competition. Player instinct is to get the job done effectively (survive/win), and only ask why if things go wrong (miss/lose). Engineers and scientists try to figure out as much about 'why' as soon as possible. It's no wonder these discussions drive one side or the other a bit crazy at times.

Qtec: If it's crap to you, stay out of the thread. There are plenty of other threads for you to enjoy. I agree with you that pool is simple to play and enjoy, and difficult to do well. You are out of line by being personally antagonistic about your view on the practical value of this thread. The conclusions that are drawn from such collaborations may well results in some teaching tools for future players. Don't be such a killjoy.

"The REAL good info will probably not be heard or ignored on this forum. The best info is certainly NOT the crap that the techies dish out.

Nothing personal Dave but I,ve had enouigh of this crap."

That is personal. You are attacking someone who is sharing good information. As a by product, you are also attacking his chosen life work. I spend time teaching pool to all levels of players, mired in what makes things work, why things are breaking down, and how to get a player playing again. This forum has many instructional aspects to it, and not just billiards gossip and hearsay. If you want coaching tips and you're not finding them in this thread you can look deeper, ask a productive question, wait for the exploration to end and then ask for applicable conclusions, or leave the others in peace to work on what interests them. You've made good contributions in other threads, so why is this one so irritating to you? I don't post often, but I lurk and read plenty when I can. I stay out of threads that don't interest me. Please consider doing the same instead of kicking sand on the people you find dishing out the proven 'crap' that the entire physical aspect of our game on the table is based upon.


Cheers!




Carl

dr_dave
01-20-2007, 06:07 PM
Carl,

Thank you for your insight, advice, and encouragement. I thought everything was well stated and appropriate.

Regards,
Dave

<blockquote><font class="small">Quote caedos:</font><hr> I'm replying to this one to make sure it shows up in Dave's e-mail queue.

I personally welcome the technical threads, even though the analysis as a whole oftentimes doesn't give me anything to work with personally when I play or teach. In fact, it often gives me 'tired head' looking for something of interest buried in the semantics of formulas and energy relationships. A piece buried in the analysis can be useful, or the rare contribution or observation I can add to the discussion. What I would like to see more of are the results in simple English guidelines that I can teach to many people and use as a player. Dr.Jewett has been great at putting experiments anyone can do in his BD articles over the years. Dr.Dave had a good three piece checklist for player reference towards the end of his Nov.'06 BD article (pages 34-35). [Dave -- a word I might add to that list is in #1 change "hitting the center of that cue ball;" to "hitting the vertical center of that cue ball;".]
The end result of threads like this is that the people we trust with the science of our sport get a good resource to add to their work and help validate things that do and don't work. The benefit for the rest of us are the tidbits we do understand, to give confidence in applying the knowledge in competition. Player instinct is to get the job done effectively (survive/win), and only ask why if things go wrong (miss/lose). Engineers and scientists try to figure out as much about 'why' as soon as possible. It's no wonder these discussions drive one side or the other a bit crazy at times.

Qtec: If it's crap to you, stay out of the thread. There are plenty of other threads for you to enjoy. I agree with you that pool is simple to play and enjoy, and difficult to do well. You are out of line by being personally antagonistic about your view on the practical value of this thread. The conclusions that are drawn from such collaborations may well results in some teaching tools for future players. Don't be such a killjoy.

"The REAL good info will probably not be heard or ignored on this forum. The best info is certainly NOT the crap that the techies dish out.

Nothing personal Dave but I,ve had enouigh of this crap."

That is personal. You are attacking someone who is sharing good information. As a by product, you are also attacking his chosen life work. I spend time teaching pool to all levels of players, mired in what makes things work, why things are breaking down, and how to get a player playing again. This forum has many instructional aspects to it, and not just billiards gossip and hearsay. If you want coaching tips and you're not finding them in this thread you can look deeper, ask a productive question, wait for the exploration to end and then ask for applicable conclusions, or leave the others in peace to work on what interests them. You've made good contributions in other threads, so why is this one so irritating to you? I don't post often, but I lurk and read plenty when I can. I stay out of threads that don't interest me. Please consider doing the same instead of kicking sand on the people you find dishing out the proven 'crap' that the entire physical aspect of our game on the table is based upon.


Cheers!




Carl


<hr /></blockquote>

dr_dave
02-01-2007, 01:38 PM
FYI, based on feedback from Jal, I have corrected some small errors in my analysis and added some graphs that show how spin transfer effectiveness changes with ball conditions. See the graphs and conclusions at the end of TP A.27 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/new/TP_A-27.pdf) if you want to see the results. You can skip all of the physics and math if it doesn't interest you.

Regards,
Dave

cushioncrawler
02-02-2007, 09:45 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> ....PS: I don't mean to stonewall madMac or you with the energy stuff. Personally, I just don't see how it would add much to the conclusions already stated.

PS: Thanks again to you and madMac for helping find and fix all of my errors. I was a little sloppy with this whole spin transfer business. <hr /></blockquote> Dr Dave. U were correct re the 35.71% max spin transfer. It duznt go up as high as the 37.52% that i calculated. My iteration method using simple newton had an inbuilt bias.

In recent dayz i increased the number of slices in my computer program (of the impact event) by a factor of 10, and then later by 100, and i found that the 37.52% dropped to the your (correct) figure of 35.71%. My coarse earlydayz iterations had (correctly) given me exactly 5/14ths spin transfer for impacts where qball spin ends at exactly the same time as impact ends, and (correctly) exactly 5/14ths balltoball frictional energy (heat) loss allso, and this perfikt rezult had given me more faith in my program than it dezerved. The bias in the first half of impact is (was) balanced by the reverse bias in the second half.

The program iz ok, but, when the qball spin ends before impact ends, i need lots of slices to give an accurate answer, the more slices the better. So, disregard everything that i said -- hope u werent thinking of buying a "Nights In White Satin" record (or dvd). But, Type 2AB gearing is still out there. madMac.
Oh, and thanks to Jim for his PM's which helped me to get to the bottom of this bizness.

jkwylde78
02-03-2007, 03:27 PM
hsv.75 - that approach may be used to execute a legal shot, however the example is a foul - the cueball slowed in speed before exiting to the right, also, it moved forward first- I could stand corrected, however, if the rules of a 'push ' shot have changed. Otherwise, this example would be a clear push.

dr_dave
02-03-2007, 03:57 PM
madMac,

Thanks for the follow-up (and thank you for using mostly the "Queen's English"). I'm glad your numbers agree with Jim's and mine. It's nice to know that the laws of physics behave, regardless of who is interpreting them.

Thanks again for helping to push the debate.

Regards,
Dave
<blockquote><font class="small">Quote cushioncrawler:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> ....PS: I don't mean to stonewall madMac or you with the energy stuff. Personally, I just don't see how it would add much to the conclusions already stated.

PS: Thanks again to you and madMac for helping find and fix all of my errors. I was a little sloppy with this whole spin transfer business. <hr /></blockquote> Dr Dave. U were correct re the 35.71% max spin transfer. It duznt go up as high as the 37.52% that i calculated. My iteration method using simple newton had an inbuilt bias.

In recent dayz i increased the number of slices in my computer program (of the impact event) by a factor of 10, and then later by 100, and i found that the 37.52% dropped to the your (correct) figure of 35.71%. My coarse earlydayz iterations had (correctly) given me exactly 5/14ths spin transfer for impacts where qball spin ends at exactly the same time as impact ends, and (correctly) exactly 5/14ths balltoball frictional energy (heat) loss allso, and this perfikt rezult had given me more faith in my program than it dezerved. The bias in the first half of impact is (was) balanced by the reverse bias in the second half.

The program iz ok, but, when the qball spin ends before impact ends, i need lots of slices to give an accurate answer, the more slices the better. So, disregard everything that i said -- hope u werent thinking of buying a "Nights In White Satin" record (or dvd). But, Type 2AB gearing is still out there. madMac.
Oh, and thanks to Jim for his PM's which helped me to get to the bottom of this bizness. <hr /></blockquote>

dr_dave
02-05-2007, 04:28 PM
FYI, I just posted a draft of a follow-up spin transfer article on my website (see the April '07 article (http://www.engr.colostate.edu/~dga/pool/bd_articles/2007/april07.pdf)). The article illustrates and describes in detail an example people have often cited on this forum as proof that throw and spin transfer are negligible. I hope you will disagree with these people after you read the article.

Please let me know if you have any feedback or recommendations. The article won't go to production for a few weeks.

Thanks,
Dave

cushioncrawler
02-05-2007, 06:43 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> FYI, I just posted a draft of a follow-up spin transfer article on my website (see the April '07 article (http://www.engr.colostate.edu/~dga/pool/bd_articles/2007/april07.pdf)). The article illustrates and describes in detail an example people have often cited on this forum as proof that throw and spin transfer are negligible. I hope you will disagree with these people after you read the article. Please let me know if you have any feedback or recommendations. The article won't go to production for a few weeks. Thanks,
Dave <hr /></blockquote> Dr Dave. I havnt bothered to read all of the old postings, but i think that it is impossible to do the stun-spin "stopshot" without transmiting english, the striped OB would proov this. And, if the OB is hit truely squarely into a cushion, it must have a slightly angled rebound. Alltho i agree that english evaporates very quickly -- but the "wobbly stripe" would tell anyhow. I will check this stuff out when i next see my 6' table at my mountain home in a week or so.

Re the ceiling of 35.71% transfer for a fullball impact, i was wondering what angle of off-center impact would be needed to get exactly 50% transfer. Allto i realize that technically the extra 14.29% would be partly (if not wholly) due to "collision induced english".

Az a point of interest, this happy impact angle would i reckon be the one and only case where one would get type 1AB gearing, ie where the qball and OB end up with the same spin (ok, same but opposite). Type 1AB gearing would of course only occur if balltoball slippage ended before impact ended (or ended at the same instant). madMac.

Qtec
02-05-2007, 07:52 PM
Carl. I admit I could have said it better but at least I was being honest. What you call , throwing sand in the face, I would call having another piont of view,
just seeing things from another angle.

Qtec

Jal
02-06-2007, 12:35 AM
<blockquote><font class="small">Quote cushioncrawler:</font><hr>Re the ceiling of 35.71% transfer for a fullball impact, i was wondering what angle of off-center impact would be needed to get exactly 50% transfer. Allto i realize that technically the extra 14.29% would be partly (if not wholly) due to "collision induced english".

Az a point of interest, this happy impact angle would i reckon be the one and only case where one would get type 1AB gearing, ie where the qball and OB end up with the same spin (ok, same but opposite). Type 1AB gearing would of course only occur if balltoball slippage ended before impact ended (or ended at the same instant). madMac. <hr /></blockquote>Mac, this will happen on any cut shot with inside english where the tip offset is equal to the distance of the contact point on the object ball from center, and the surface speed isn't so great that gearing can't occur (ie, only smallish cut angles need apply). It can't happen with outside english.

Jim

dr_dave
02-06-2007, 09:15 AM
<blockquote><font class="small">Quote cushioncrawler:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> FYI, I just posted a draft of a follow-up spin transfer article on my website (see the April '07 article (http://www.engr.colostate.edu/~dga/pool/bd_articles/2007/april07.pdf)). The article illustrates and describes in detail an example people have often cited on this forum as proof that throw and spin transfer are negligible. I hope you will disagree with these people after you read the article. Please let me know if you have any feedback or recommendations. The article won't go to production for a few weeks. Thanks,
Dave <hr /></blockquote> Dr Dave. I havnt bothered to read all of the old postings, but i think that it is impossible to do the stun-spin "stopshot" without transmiting english, the striped OB would proov this. And, if the OB is hit truely squarely into a cushion, it must have a slightly angled rebound. Alltho i agree that english evaporates very quickly -- but the "wobbly stripe" would tell anyhow.<hr /></blockquote>I agree. That's really the whole point of the article. Diagram 1 is not possible under typical playing conditions. Diagram 2 is what is more expected.
<blockquote><font class="small">Quote cushioncrawler:</font><hr>I will check this stuff out when i next see my 6' table at my mountain home in a week or so.<hr /></blockquote>Let me know if you come up with something that disagrees with the conclusions in the article. Thanks.

<blockquote><font class="small">Quote cushioncrawler:</font><hr>Re the ceiling of 35.71% transfer for a fullball impact, i was wondering what angle of off-center impact would be needed to get exactly 50% transfer.<hr /></blockquote>Spin transfer is not as clear with cut shots. Spin can transfer due to collision-induced throw (CIT) and/or spin-induced throw (SIT). With "gearing" outside English, there is absolutely no throw or spin transfer (see my January '07 article (http://www.engr.colostate.edu/~dga/pool/bd_articles/2007/jan07.pdf)). For a cut shot with no English, CIT transfers spin to the OB. Since the CB has no spin to begin with, the spin transfer percentage can be considered infinite!!! Therefore, spin transfer percentages don't have much meaning when referring to cut shots.

Regards,
Dave

cushioncrawler
02-06-2007, 02:40 PM
<blockquote><font class="small">Quote Jal:</font><hr> <blockquote><font class="small">Quote cushioncrawler:</font><hr>Re the ceiling of 35.71% transfer for a fullball impact, i was wondering what angle of off-center impact would be needed to get exactly 50% transfer. Allto i realize that technically the extra 14.29% would be partly (if not wholly) due to "collision induced english". Az a point of interest, this happy impact angle would i reckon be the one and only case where one would get type 1AB gearing, ie where the qball and OB end up with the same spin (ok, same but opposite). Type 1AB gearing would of course only occur if balltoball slippage ended before impact ended (or ended at the same instant). madMac. <hr /></blockquote>Mac, this will happen on any cut shot with inside english where the tip offset is equal to the distance of the contact point on the object ball from center, and the surface speed isn't so great that gearing can't occur (ie, only smallish cut angles need apply). It can't happen with outside english. Jim <hr /></blockquote> Jim -- I think that all gearing is Type 2AB, except of course when it is Type 1AB. But Type 1AB is an allmost impossible "happy" happening, Type 1AB can only occur (i reckon) when u uze a little bit of inside english with an allmost fullball impact, and for a given balltoball friction one shood be able to calculate the exact combination of english and contact needed.

So, if the qball haz zero english, or outside english, then the gearing (if it is acheeved at all) can only be Type 2A or 2B. And, if the qball haz inside english, Type 1A or Type 1B are possible, but only for one fixed combination of spin-rate and impact-angle (for any one nominated value of friction).

Jim, it looks to me that u might be correct when u say ..."this will happen on any cut shot with inside english where the tip offset is equal to the distance of the contact point on the object ball from center, and the surface speed isn't so great that gearing can't occur (ie, only smallish cut angles need apply)".

How did u work this out?? Of course none of this is of any use in play. On the other hand, perhaps it is of some use, koz, the max (dg) throw, and max spin (%) transfer, can only be acheeved when balltoball slippage ends at the same instant that balltoball impact ends, in which case some sort of "formula", like the formula u mention, might be allmost usefull. But i'm not much interested in play, i am interested in the impact-fizzyks theory. madMac.

Jal
02-06-2007, 04:52 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> FYI, I just posted a draft of a follow-up spin transfer article on my website (see the April '07 article (http://www.engr.colostate.edu/~dga/pool/bd_articles/2007/april07.pdf)). The article illustrates and describes in detail an example people have often cited on this forum as proof that throw and spin transfer are negligible. I hope you will disagree with these people after you read the article.

Please let me know if you have any feedback or recommendations. The article won't go to production for a few weeks.

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

Thanks for the mention, and again for making these articles available to us. Because of people like you, Bob Jewett, the instructors, etc., as well as insights from the general player, the myths surrounding the game are falling at an unprecedented rate. And for those interested in the technical side, especially those of us for whom the physics is mostly a vague memory, your proofs are welcomed not only as reminders, but offer much more than we likely ever understood in the first place. Please keep em coming.

Jim

Jal
02-06-2007, 06:42 PM
<blockquote><font class="small">Quote cushioncrawler:</font><hr> Jim -- I think that all gearing is Type 2AB, except of course when it is Type 1AB. But Type 1AB is an allmost impossible "happy" happening, Type 1AB can only occur (i reckon) when u uze a little bit of inside english with an allmost fullball impact, and for a given balltoball friction one shood be able to calculate the exact combination of english and contact needed.

So, if the qball haz zero english, or outside english, then the gearing (if it is acheeved at all) can only be Type 2A or 2B. And, if the qball haz inside english, Type 1A or Type 1B are possible, but only for one fixed combination of spin-rate and impact-angle (for any one nominated value of friction).

Jim, it looks to me that u might be correct when u say ..."this will happen on any cut shot with inside english where the tip offset is equal to the distance of the contact point on the object ball from center, and the surface speed isn't so great that gearing can't occur (ie, only smallish cut angles need apply)".

How did u work this out?? Of course none of this is of any use in play. On the other hand, perhaps it is of some use, koz, the max (dg) throw, and max spin (%) transfer, can only be acheeved when balltoball slippage ends at the same instant that balltoball impact ends, in which case some sort of "formula", like the formula u mention, might be allmost usefull. But i'm not much interested in play, i am interested in the impact-fizzyks theory. madMac.<hr /></blockquote>Hi Mac,

Your first sentence is about as committed as I like to be. /ccboard/images/graemlins/smile.gif If you intuited the conditions when 1A gearing occurs (as I expect you did), nice job. I can't see it myself without the math pointing the way. The proof is very straighforward if you think in terms of surface speed.

Let the surface speed at the "point" of contact with the OB be S. It consists of Sv and Sw, where Sv (read S sub v) is the speed component from the cut angle (= Vsin(theta)), and Sw is the component from the cueball's spin (=RW). So:

1) S = Sv + Sw

We have to be careful about the signs (I got different results by not being careful). Either Sv or Sw may be negative for all we know at this point. Let's arbitrarily define the positive direction in the direction of S, which we do by making the larger of Sv and Sw positive.

Let Sw' be the post-impact surface speed due to spin on the cueball, and Sow' the surface speed due to spin on the object ball. From all that's been said in this thread, we know that when gearing takes place:

2) Sow' = (5/14)S

Since friction acts in the opposite direction on the cueball, we know that the change in its surface speed from a change in spin will be - (5/14)S. So:

3) Sw' = Sw - (5/14)S

The condition that the balls have equal but opposite spins after impact is:

4) Sw' = Sow'

Yes, the signs are the same even though the spins are opposite. Now we can solve for the cueball's initial surface speed due to spin, Sw, by substituting in eq (4) for Sw' and Sow' from eqs (2) and (3):

Sw - (5/14)S = (5/14)S ,then

Sw = (10/14)S = (10/14)(Sv + Sw) , then solving for Sw

Sw = (5/2)Sv

Since the sign of Sw is the same as Sv, Sw must represent inside english. This is the only solution allowed, so that eliminates outside english as a possibility. Finding S, Sw' and Sow' :

from eq (1),
S = Sv + (5/2)Sv = (7/2)Sv

from eq (2),
Sow' = (5/14)S = (5/14)(7/2)Sv = (5/4)Sv

from eq (3),
Sw' = (5/2)Sv - (5/14)(7/2)Sv = (5/4)Sv

So Sw' = Sow' and the balls have equal/opposite spins (1A gearing). Also, both balls have one-half the cueball's initial spin (surface speed) of (5/2)Sv, in magnitude anyway.

Unfortunately, it's not even useful for predicting where maximum throw will occur, since this will take place anytime gearing occurs during impact (and Sw = (5/2)Sv), not just at the end. Predicating that is a bit more complicated and requires a series of successive approximations (or some such thing). I have a program that does it using Newton's Method, which is much quicker than semi-blind guessing. If you want any info on this, let me know.

Using the term "transfer of spin" gets us into some trouble here. It's kind of loose talk, which we did engage in for the full-hit case. It seemed more natural there. This may be just as bad, but I think you could say that the object ball's spin is derived from, and a necessary condition, for the conservation of the system's angular momentum, which includes the apparent purely translational velocities of the balls before and after impact (r x p stuff). In that sense, it really doesn't get it directly from the cueball's spin (especially since it's in the opposite direction!)

As far as tip offset, we know that in general, the cueball's spin rate (RW actually) is given by:

RW = (5/2)(b/R)V

where b/R is the tip offset as a fraction of radius, and V is its speed. Since

Sw = RW = (5/2)Sv = (5/2)Vsin(theta)

for 1A gearing, b/R must equal sin(theta), which is the distance from the contact point to center on the object ball (simple physics-wise).

Hope that makes some sense (and possibly is even right).

Jim

cushioncrawler
02-06-2007, 07:42 PM
<blockquote><font class="small">Quote Jal:</font><hr> .... Unfortunately, it's not even useful for predicting where maximum throw will occur, since this will take place anytime gearing occurs during impact (and Sw = (5/2)Sv), not just at the end. Predicating that is a bit more complicated and requires a series of successive approximations (or some such thing). I have a program that does it using Newton's Method, which is much quicker than semi-blind guessing. If you want any info on this, let me know.<hr /></blockquote> Jim -- U have talked me into it, i will put together a little iteration program and get my little newton-shmoos to work on this. My shmoos will tell me that "throw is indeed at a max when balltoball slippage falls to zero at the same instant that impact ends" (this wording is not as loose as the wording i used earlyr) -- Alltho i am a bit worried here, koz, part of the reason is that balltoball friction (ie throw) is at a maximum when slippage falls "gradually" to zero at the end of impact, and my shmoos karnt proov that, but i dont think that this hiccup will stop them, i will use a "fixed" friction factor, say 0.060 (this will be nearnuff).

And, my shmoos will tell me the qball-to-objectball impact angle when Type 1A gearing occurs. This will be a trial&amp;error affair, in addition to uzing iteration (newton-shmoos), which might be similar to what u said. I suspect that this "angle" will depend on the "0.06", and i wouldnt be surprized if it didnt depend on the qball spinrate at all. Velocity of course wont be a factor, but i shood check that allso, if i have time.

Anyhow, i can see a 3-way shootout looming -- like in "the good the bad and the ugly". There is me, MacUgly, with my newton-shmoos, u, Jim Bad, with your Newton-Shmoos, and Dr Good.

Jim, did u say that your equations wont tell u what the impact-angle is, for 1A gearing ?? I will have a deeper look at your tip offset stuff after i have do the other stuff. madMac.

Jal
02-07-2007, 12:32 AM
<blockquote><font class="small">Quote cushioncrawler:</font><hr>...Anyhow, i can see a 3-way shootout looming -- like in "the good the bad and the ugly". There is me, MacUgly, with my newton-shmoos, u, Jim Bad, with your Newton-Shmoos, and Dr Good.

Jim, did u say that your equations wont tell u what the impact-angle is, for 1A gearing ?? I will have a deeper look at your tip offset stuff after i have do the other stuff. madMac. <hr /></blockquote>I doubt that Dr. Dave will get involved since he tends to deal with more practical issues. So far, neither of us has come up with a situation where this could conceivably be of any importance.

But knowing where maximum throw occurs, is very useful. For starters, we agree on the how, which is good. But you won't get the same numbers as Dr. Dave or my program, because they're based on a value for the coefficient of friction (mu) which varies with, and is a function of surface speed. You should get the same amount of throw when gearing occurs well before the end of impact, since this isn't dependent on mu.

Regarding 1A gearing, the above equations show that it will happen at any impact angle where slippage ends during impact, and the cueball's pre-impact inside english is such that:

RW = (5/2)Vsin(theta)

where W is its spin rate in radians/sec, R is its radius, and Vsin(theta) is the component of its velocity along the tangent line. There's no single impact angle in which it will take place. It'll happen over a range of angles, from the smallest one possible just beyond zero, up to where the surface speed is too great to allow slippage to end during impact. The latter has to be modest because of the requirement on the cueball's spin.

Our "Newton's" methods are two different things. The one I refered to is a means of making educated guesses (all automated) to arrive at an answer. It's quite powerful and generally produces two additional decimal digits of accuracy per guess. I think you would like it from the way you approach problems, but it does involve a foray into calculus. Apparently Newton himself, the co-inventor of calculus, did not fully understand it, although it is really pretty simple...when someone explains the finished product and you're not busy discovering all of these things!

Jim

dr_dave
02-07-2007, 08:56 AM
<blockquote><font class="small">Quote Jal:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> FYI, I just posted a draft of a follow-up spin transfer article on my website (see the April '07 article (http://www.engr.colostate.edu/~dga/pool/bd_articles/2007/april07.pdf)). The article illustrates and describes in detail an example people have often cited on this forum as proof that throw and spin transfer are negligible. I hope you will disagree with these people after you read the article.

Please let me know if you have any feedback or recommendations. The article won't go to production for a few weeks.

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

Thanks for the mention, and again for making these articles available to us. Because of people like you, Bob Jewett, the instructors, etc., as well as insights from the general player, the myths surrounding the game are falling at an unprecedented rate. And for those interested in the technical side, especially those of us for whom the physics is mostly a vague memory, your proofs are welcomed not only as reminders, but offer much more than we likely ever understood in the first place. Please keep em coming.<hr /></blockquote>
Jim,

You are very welcome, and thank you for the nice words. It helps my motivation level to know that people appreciate what I do.

Regards,
Dave

dr_dave
02-07-2007, 09:22 AM
FYI, I think TP A.27 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/new/TP_A-27.pdf) and Equations 7-15 in TP A.14 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/new/TP_A-14.pdf) tell the whole story, regardless of the type and amount of English, regardless of the speed, regardless of the type of gearing, and regardless of the cut angle. The plots at the end of the analyses visually show what the equations imply.

Regards,
Dave
<blockquote><font class="small">Quote cushioncrawler:</font><hr> <blockquote><font class="small">Quote Jal:</font><hr> .... Unfortunately, it's not even useful for predicting where maximum throw will occur, since this will take place anytime gearing occurs during impact (and Sw = (5/2)Sv), not just at the end. Predicating that is a bit more complicated and requires a series of successive approximations (or some such thing). I have a program that does it using Newton's Method, which is much quicker than semi-blind guessing. If you want any info on this, let me know.<hr /></blockquote> Jim -- U have talked me into it, i will put together a little iteration program and get my little newton-shmoos to work on this. My shmoos will tell me that "throw is indeed at a max when balltoball slippage falls to zero at the same instant that impact ends" (this wording is not as loose as the wording i used earlyr) -- Alltho i am a bit worried here, koz, part of the reason is that balltoball friction (ie throw) is at a maximum when slippage falls "gradually" to zero at the end of impact, and my shmoos karnt proov that, but i dont think that this hiccup will stop them, i will use a "fixed" friction factor, say 0.060 (this will be nearnuff).

And, my shmoos will tell me the qball-to-objectball impact angle when Type 1A gearing occurs. This will be a trial&amp;error affair, in addition to uzing iteration (newton-shmoos), which might be similar to what u said. I suspect that this "angle" will depend on the "0.06", and i wouldnt be surprized if it didnt depend on the qball spinrate at all. Velocity of course wont be a factor, but i shood check that allso, if i have time.

Anyhow, i can see a 3-way shootout looming -- like in "the good the bad and the ugly". There is me, MacUgly, with my newton-shmoos, u, Jim Bad, with your Newton-Shmoos, and Dr Good.

Jim, did u say that your equations wont tell u what the impact-angle is, for 1A gearing ?? I will have a deeper look at your tip offset stuff after i have do the other stuff. madMac. <hr /></blockquote>

dr_dave
02-07-2007, 09:24 AM
<blockquote><font class="small">Quote Jal:</font><hr> <blockquote><font class="small">Quote cushioncrawler:</font><hr>...Anyhow, i can see a 3-way shootout looming -- like in "the good the bad and the ugly". There is me, MacUgly, with my newton-shmoos, u, Jim Bad, with your Newton-Shmoos, and Dr Good.

Jim, did u say that your equations wont tell u what the impact-angle is, for 1A gearing ?? I will have a deeper look at your tip offset stuff after i have do the other stuff. madMac. <hr /></blockquote>I doubt that Dr. Dave will get involved since he tends to deal with more practical issues. So far, neither of us has come up with a situation where this could conceivably be of any importance.

But knowing where maximum throw occurs, is very useful. For starters, we agree on the how, which is good. But you won't get the same numbers as Dr. Dave or my program, because they're based on a value for the coefficient of friction (mu) which varies with, and is a function of surface speed. You should get the same amount of throw when gearing occurs well before the end of impact, since this isn't dependent on mu.<hr /></blockquote>Jim,

Nice summary. I agree 100%.

Dave

Deeman3
02-07-2007, 10:24 AM
I am considering mailing out free pocket protectors to everyone who has replied in this post. /ccboard/images/graemlins/grin.gif

DeeMan
getting a headache...

dr_dave
02-07-2007, 11:01 AM
<blockquote><font class="small">Quote Deeman3:</font><hr> I am considering mailing out free pocket protectors to everyone who has replied in this post. /ccboard/images/graemlins/grin.gif<hr /></blockquote>I much prefer pool gizmos. Even though most of them are complete garbage, they are fun to play with anyway. Please keep me in mind when you're making your Christmas list. /ccboard/images/graemlins/cool.gif

Dave

cushioncrawler
02-07-2007, 02:54 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> FYI, I think TP A.27 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/new/TP_A-27.pdf) and Equations 7-15 in TP A.14 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/new/TP_A-14.pdf) tell the whole story, regardless of the type and amount of English, regardless of the speed, regardless of the type of gearing, and regardless of the cut angle. The plots at the end of the analyses visually show what the equations imply. Regards, Dave <hr /></blockquote> Dr Dave -- Thanks, i looked throo theze (updated now) again. I think that my (aforementioned)thinking wont necessarily have to contradict any of your graphs etc, and i think it wont. Anyhow, i will push ahead and report back. madMac.

cushioncrawler
02-07-2007, 03:02 PM
<blockquote><font class="small">Quote Deeman3:</font><hr> I am considering mailing out free pocket protectors to everyone who has replied in this post. /ccboard/images/graemlins/grin.gif DeeMan ..getting a headache... <hr /></blockquote> What sort of tests shood i do on my "pocket protectors" ??? Is there any scope for a graph of %-protection versus spin-rate ??? I would prefer some theoretical information, but as a last resort i might accept some actual test data. No, i have changed my mind, theory only thank u. madMac.