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billiards89
11-12-2007, 05:34 PM
i bought a scorpion jumb/break cue i was just wondering why they use a quarter radius tip on them is there a reason

Jal
11-12-2007, 06:33 PM
On a break shot, the effective tip offset, that is, the distance of the actual contact point from centerball as opposed to the offset of the center of the shaft, will be less when accidently hitting off-center. Since no one actually hits centerball consistently, strictly speaking, the flatter tip profile almost always provides some correction.

Depending on generated ball speed though, hitting slightly above center is often called for to impart just enough topspin to help park the cueball. A flatter tip helps here too, since an interval of apparent offsets (center of shaft) is mapped onto a smaller interval of actual offsets. In other words, it helps one to be more accurate with a deliberately off-center hit. A quarter shaped tip allows for about 33% more overshoot or undershoot error than a dime shaped tip, given some acceptable tolerance.

For example, suppose the goal is to get the actual offset within a tenth of inch. With a dime tip, the error in center shaft offset can be up to 0.13/2 inches on either side of the target. With a quarter shaped tip, the error can be up to 0.14/2 inches. The allowable margin beyond 0.1 inch is thus approximately one third (.04/.03) greater with the quarter tip.

Jim

dr_dave
11-13-2007, 10:36 AM
<blockquote><font class="small">Quote Jal:</font><hr> On a break shot, the effective tip offset, that is, the distance of the actual contact point from centerball as opposed to the offset of the center of the shaft, will be less when accidently hitting off-center. Since no one actually hits centerball consistently, strictly speaking, the flatter tip profile almost always provides some correction.<hr /></blockquote>By "correction," I assume you mean "less squirt" due to smaller offset. Is that the case?

<blockquote><font class="small">Quote Jal:</font><hr>Depending on generated ball speed though, hitting slightly above center is often called for to impart just enough topspin to help park the cueball. A flatter tip helps here too, since an interval of apparent offsets (center of shaft) is mapped onto a smaller interval of actual offsets. In other words, it helps one to be more accurate with a deliberately off-center hit. A quarter shaped tip allows for about 33% more overshoot or undershoot error than a dime shaped tip, given some acceptable tolerance.

For example, suppose the goal is to get the actual offset within a tenth of inch. With a dime tip, the error in center shaft offset can be up to 0.13/2 inches on either side of the target. With a quarter shaped tip, the error can be up to 0.14/2 inches. The allowable margin beyond 0.1 inch is thus approximately one third (.04/.03) greater with the quarter tip.<hr /></blockquote>Good points!

Regards,
Dave

PS: FYI, I have some analysis concerning the effects of tip size on squirt and English in TP B.1 (http://billiards.colostate.edu/technical_proofs/new/TP_B-1.pdf). Check it out. This is also the topic of my BD article that will come out in the January issue. I can send you the draft of the article if you want to see it. I just can't post the link in the articles section of my website (http://billiards.colostate.edu/bd_articles/index.html) yet.

Billy_Bob
11-13-2007, 01:08 PM
I use a quarter shaped tip on my break cue because it *will* become quarter shaped and stay that way no matter what you do! /ccboard/images/graemlins/grin.gif

Basically fast break shots "squish" in the tip. So if you use a dime or nickel shape, it will quickly get "squished" out of shape.

My thinking is I will be more consistent if always using the same shape tip. And a quarter shape along with a very very hard break/jump tip will keep its quarter shape for months.

Jal
11-14-2007, 02:14 AM
<blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote Jal:</font><hr> On a break shot, the effective tip offset, that is, the distance of the actual contact point from centerball as opposed to the offset of the center of the shaft, will be less when accidently hitting off-center. Since no one actually hits centerball consistently, strictly speaking, the flatter tip profile almost always provides some correction.<hr /></blockquote>By "correction," I assume you mean "less squirt" due to smaller offset. Is that the case?<hr /></blockquote>Dr. Dave,

Sorry for the delay. I did read TP_B-1 and noticed that your way of defining the pivot point is more operationally convenient, and produces a particularly simple equation for it, even taking into account all of the various curvatures. Very nice!

I hadn't thought about squirt in the above, only the reduced actual offset due to the flatter tip profile. You've carried that much further in your analysis.

I would very much like to see your article and thanks for the offer. I am a bit leary, however, of even your results given the wide ranging numbers that have been reported for the low squirt cues. Not that there is any discernible flaw in your procedures, but I would feel more comfortable if your up-and-coming stroke machine produced similar results.

I am certain though that you will finally put this whole thing to rest.

Jim

Jal
11-14-2007, 02:17 AM
<blockquote><font class="small">Quote Billy_Bob:</font><hr> I use a quarter shaped tip on my break cue because it *will* become quarter shaped and stay that way no matter what you do! /ccboard/images/graemlins/grin.gif

Basically fast break shots "squish" in the tip. So if you use a dime or nickel shape, it will quickly get "squished" out of shape.

My thinking is I will be more consistent if always using the same shape tip. And a quarter shape along with a very very hard break/jump tip will keep its quarter shape for months.
<hr /></blockquote>Welcome back Billy Bob. Very sensible advice, imo.

Jim

dr_dave
11-14-2007, 03:09 PM
<blockquote><font class="small">Quote Jal:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote Jal:</font><hr> On a break shot, the effective tip offset, that is, the distance of the actual contact point from centerball as opposed to the offset of the center of the shaft, will be less when accidently hitting off-center. Since no one actually hits centerball consistently, strictly speaking, the flatter tip profile almost always provides some correction.<hr /></blockquote>By "correction," I assume you mean "less squirt" due to smaller offset. Is that the case?<hr /></blockquote>Dr. Dave,

Sorry for the delay. I did read TP_B-1 and noticed that your way of defining the pivot point is more operationally convenient, and produces a particularly simple equation for it, even taking into account all of the various curvatures. Very nice!<hr /></blockquote>Thanks.

<blockquote><font class="small">Quote Jal:</font><hr>I hadn't thought about squirt in the above, only the reduced actual offset due to the flatter tip profile. You've carried that much further in your analysis.

I would very much like to see your article and thanks for the offer.<hr /></blockquote>Send me a PM with your e-mail address, and I'll send the draft to you.

<blockquote><font class="small">Quote Jal:</font><hr>I am a bit leary, however, of even your results given the wide ranging numbers that have been reported for the low squirt cues. Not that there is any discernible flaw in your procedures, but I would feel more comfortable if your up-and-coming stroke machine produced similar results.<hr /></blockquote>I should have data from the mechanical cue-tester by next week. I will publish the results in my February '08 article. However, I don't expect the results to be any different than what is reported in my September '07 article (http://billiards.colostate.edu/bd_articles/2007/sept07.pdf).

<blockquote><font class="small">Quote Jal:</font><hr>I am certain though that you will finally put this whole thing to rest.<hr /></blockquote>I was hoping more people would report their own results in the other thread (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&amp;Board=ccb&amp;Number=262594&amp;page =0&amp;view=collapsed&amp;sb=5&amp;o=&amp;fpart=1). If more people do the simple experiment, and if their results are in the same range as mine, I think that would help "put things to rest."

Regards,
Dave