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View Full Version : rail cut-shot cue-ball control



dr_dave
05-30-2007, 05:13 PM
This was discussed in a previous thread (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&Board=ccb&Number=244752&Foru m=ccb&Words=driving%20into%20the%20cushion&Match=E ntire%20Phrase&Searchpage=0&Limit=25&Old=6months&M ain=244293&Search=true#Post244752). The topic is: How do you make the cue ball go where you want to with rail cut-shots, and what is the physics behind each outcome (and what does it look like in super-slow-motion)? The answers can be found in HSV A.128-A.141 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/index.html). Check them out. I think these are some of the best (most interesting) high-speed video clips I've posted recently. I've listed them in order based on how far down-table the cue ball travels. The object ball is pocketed in all of the clips from two diamonds up from the corner pocket.

Enjoy. I look forward to reading some of your comments and discussion.

Regards,
Dave

Sig
05-31-2007, 11:46 AM
I don't have any intelligent comments, but these are awesome videos!

dr_dave
05-31-2007, 12:25 PM
<blockquote><font class="small">Quote Sig:</font><hr> I don't have any intelligent comments, but these are awesome videos! <hr /></blockquote>Thank you. I was quite pleased with the results also.

Regards,
Dave

Cornerman
05-31-2007, 03:04 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> This was discussed in a previous thread (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&amp;Board=ccb&amp;Number=244752&amp;Foru m=ccb&amp;Words=driving%20into%20the%20cushion&amp;Match=E ntire%20Phrase&amp;Searchpage=0&amp;Limit=25&amp;Old=6months&amp;M ain=244293&amp;Search=true#Post244752). The topic is: How do you make the cue ball go where you want to with rail cut-shots, and what is the physics behind each outcome (and what does it look like in super-slow-motion)? The answers can be found in HSV A.128-A.141 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/index.html). Check them out. I think these are some of the best (most interesting) high-speed video clips I've posted recently. I've listed them in order based on how far down-table the cue ball travels. The object ball is pocketed in all of the clips from two diamonds up from the corner pocket.

Enjoy. I look forward to reading some of your comments and discussion.

Regards,
Dave <hr /></blockquote>These are aweseome Dave. It's tough to tell where the cueball dances off to afterwards, but it's clear that there aren't just one or two ways to make the shot and get the position.

You might want to take a look at this one:

http://www.engr.colostate.edu/~dga/pool/high_speed_videos/new/HSVA-140.htm

I've snapshot the point of rail contact:

http://home.comcast.net/~ohagnir1/HSV_A.140_Snapshot.jpg

The cueball contacts the cushion first barely, and hits the object ball while compressing, while using running english. I think this is one of the cases I discussed in the other thread (while compressing into the cushion vs. while decompressing the cushion). I don't know how easy it is to repeat this hit and video it, but I've theorized that this is the hit required for the standard running three-railer on a frozen object ball.

{edit: I see that 141 also shows the cueball hitting the object ball just as it starts its compression, which further substantiates my Theory B).

Now how about the shallower angles of approach? /ccboard/images/graemlins/wink.gif

Fred

dr_dave
05-31-2007, 04:21 PM
<blockquote><font class="small">Quote Cornerman:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> This was discussed in a previous thread (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&amp;Board=ccb&amp;Number=244752&amp;Foru m=ccb&amp;Words=driving%20into%20the%20cushion&amp;Match=E ntire%20Phrase&amp;Searchpage=0&amp;Limit=25&amp;Old=6months&amp;M ain=244293&amp;Search=true#Post244752). The topic is: How do you make the cue ball go where you want to with rail cut-shots, and what is the physics behind each outcome (and what does it look like in super-slow-motion)? The answers can be found in HSV A.128-A.141 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/index.html). Check them out. I think these are some of the best (most interesting) high-speed video clips I've posted recently. I've listed them in order based on how far down-table the cue ball travels. The object ball is pocketed in all of the clips from two diamonds up from the corner pocket.

Enjoy. I look forward to reading some of your comments and discussion.

Regards,
Dave <hr /></blockquote>These are aweseome Dave.<hr /></blockquote>Thanks.

<blockquote><font class="small">Quote Cornerman:</font><hr>It's tough to tell where the cueball dances off to afterwards, but it's clear that there aren't just one or two ways to make the shot and get the position.<hr /></blockquote>Agreed. FYI, the largest cue-ball rebound angle was achieved in HSV A.141 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/new/HSVA-141.htm). The object ball was 2 diamonds from the corner pocket, and the cue ball ended up hitting about 1 3/4 diamonds from the corner pocket on the foot rail ... about the same trajectory you illustrated here (http://cuetable.com/P/?@3Abgx3PJXb3Ubgx3UcYt3kJXb3kboi3kFlj4kbHU1kBnl4uA IU@) (although, the cue ball path is curved a little in real life).

<blockquote><font class="small">Quote Cornerman:</font><hr>You might want to take a look at this one:

http://www.engr.colostate.edu/~dga/pool/high_speed_videos/new/HSVA-140.htm

I've snapshot the point of rail contact:

http://home.comcast.net/~ohagnir1/HSV_A.140_Snapshot.jpg

The cueball contacts the cushion first barely, and hits the object ball while compressing, while using running english. I think this is one of the cases I discussed in the other thread (while compressing into the cushion vs. while decompressing the cushion). I don't know how easy it is to repeat this hit and video it, but I've theorized that this is the hit required for the standard running three-railer on a frozen object ball.
{edit: I see that 141 also shows the cueball hitting the object ball just as it starts its compression, which further substantiates my Theory B).<hr /></blockquote>Thank you for pointing this out. You are right ... the cue ball does hit the rail first (barely). I've changed the descriptions of HSV A.139-A.141 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/index.html) on my website to read:

HSV A.139: rail cut-shot hitting the rail first, hitting the ball while compressing, with natural (running) English

HSV A.140: rail cut-shot hitting the rail first (barely), hitting the ball during initial compression, with lots of natural (running) English

HSV A.141: rail cut-shot hitting the rail first (barely), hitting the ball during initial compression, slower, with stun and lots of natural (running) English

<blockquote><font class="small">Quote Cornerman:</font><hr>Now how about the shallower angles of approach? /ccboard/images/graemlins/wink.gif<hr /></blockquote>Believe it or not, I had actually planned that (plus a lot more); but as always: too little time ... too much to do.

Regards,
Dave

cushioncrawler
05-31-2007, 06:15 PM
Dr Dave -- The Vernon Elliot cutshot slo-mo appears to proov what i woz theorizing a few months ago. The qball haz clockwize spin. The OB comes off the cushion with clockwize spin. This is what i predicted (what a guy -- FIGJAM). The OB got (tried to get) a good dose of Anti-Clockwize spin during ball'to'ball impact, and this rezulted (initially) in retrograde XX cushion force, and later just before the ball left the cushion the cushion had enuff XX deformation remaining enabling it to continue with this retrograde XX force.

A few weeks ago, i couldnt get any such cutback effect with the L-Profile cushions on an english 6' by 2' billiards'n'snooker table. Here the XX deformation and XX forces and bounce are much stronger and quick-acting than the YY forces and bounce. Unlike the K55 etc profiles where the XX force and bounce seem to be more in harmony with the natural YY bounce.

Clearly too, the YY cushion deformation (in the slo-mo) is huge. I had never been convinced of Bob's (and other's) theory that the cushion sort of bunches up ahead of an attacking ball, and in effect changes (squares-up) the effektiv angle of attack. I allways reckoned that this could be simply explained by simple hysterisis. But, seeing such a big deformation at what is really a softish impact, i am starting to agree that this "squaring-up" is a big factor here (whether mainly hysterisis on not).

Allso, notice that the ball'to'ball impakt angle is in fact not very thin at all. It might be about 1/32nd ball, not 1/128 or something else very thin. madMac.

Paul_Mon
06-01-2007, 08:16 AM
Dave,

Those are some great videos. I was particularly interested and surprised by some of the transferred english.

How big are the corner pockets? From the looks of the following video it appears that the object ball is way off target.

HSV A.137 - rail cut-shot hitting the rail first, hitting the ball while compressing, fast, with draw and natural (running) English

Great stuff..........Paul Mon

dr_dave
06-01-2007, 09:28 AM
<blockquote><font class="small">Quote Paul_Mon:</font><hr> Dave,

Those are some great videos. I was particularly interested and surprised by some of the transferred english.

How big are the corner pockets?<hr /></blockquote>The corner pockets are BCA-standard: 5 inches at the mouth (i.e., pretty big).

<blockquote><font class="small">Quote Paul_Mon:</font><hr>From the looks of the following video it appears that the object ball is way off target.

HSV A.137 - rail cut-shot hitting the rail first, hitting the ball while compressing, fast, with draw and natural (running) English<hr /></blockquote>You are right. The ball does seem to be coming away from the rail quite a bit in HSV A.137 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/new/HSVA-137.htm). I tried to edit out all of the attempts that resulted in missing the pocket, but I might have made a mistake with this one (although, I'm not sure ... it may have gone in ... my notes didn't indicate a miss with this shot, but I shot video all day long, so I wouldn't be surprised if I had an error in my notes).

<blockquote><font class="small">Quote Paul_Mon:</font><hr>Great stuff<hr /></blockquote>Thanks.

Regards,
Dave

dr_dave
06-01-2007, 10:12 AM
Mac,

FYI, to keep things better organized, I responded to your comments below in the Vernon Elliott cross-side bank thread (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&amp;Board=ccb&amp;Number=252128&amp;page =0&amp;view=collapsed&amp;sb=5&amp;o=&amp;vc=1). Here's a direct link to my response (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&amp;Board=ccb&amp;Number=252242&amp;page =0&amp;view=collapsed&amp;sb=5&amp;o=&amp;fpart=&amp;vc=).

Regards,
Dave

<blockquote><font class="small">Quote cushioncrawler:</font><hr> Dr Dave -- The Vernon Elliot cutshot slo-mo appears to proov what i woz theorizing a few months ago. The qball haz clockwize spin. The OB comes off the cushion with clockwize spin. This is what i predicted (what a guy -- FIGJAM). The OB got (tried to get) a good dose of Anti-Clockwize spin during ball'to'ball impact, and this rezulted (initially) in retrograde XX cushion force, and later just before the ball left the cushion the cushion had enuff XX deformation remaining enabling it to continue with this retrograde XX force.

A few weeks ago, i couldnt get any such cutback effect with the L-Profile cushions on an english 6' by 2' billiards'n'snooker table. Here the XX deformation and XX forces and bounce are much stronger and quick-acting than the YY forces and bounce. Unlike the K55 etc profiles where the XX force and bounce seem to be more in harmony with the natural YY bounce.

Clearly too, the YY cushion deformation (in the slo-mo) is huge. I had never been convinced of Bob's (and other's) theory that the cushion sort of bunches up ahead of an attacking ball, and in effect changes (squares-up) the effektiv angle of attack. I allways reckoned that this could be simply explained by simple hysterisis. But, seeing such a big deformation at what is really a softish impact, i am starting to agree that this "squaring-up" is a big factor here (whether mainly hysterisis on not).

Allso, notice that the ball'to'ball impakt angle is in fact not very thin at all. It might be about 1/32nd ball, not 1/128 or something else very thin. madMac. <hr /></blockquote>