I’m new here so I have not seen a lot of the discussions on deflection and shaft design…so for those of you who have followed this conceptually, please don’t let me confuse this issue with old and fully settled questions. Simply point me to the answer and I’ll get up to speed without troubling anyone. I was obliged recently to answer criticism heaped on one of my friends and customers for posting his new cue in the cue gallery and showing his exuberance. In the process, one fellow posted a link to an article on cue ball squirt that uses some quantified methods of physics and maths to explain the squirt phenomenon. For those of you who have not read the article the link is
http://www.sfbilliards.com/Shepard_squirt.pdf
I first heard the term “deflection” a couple of years ago and had to shake my head in disbelief at “the straining at a gnat while swallowing a camel” feeling I got at the explanation received. I have come to understand that the explanation was flawed but my impression has not abated. I posted this excerpt in the cue gallery and got no direct rebuttal so I decided to post it again, properly titled, to generate discourse and understanding.
I really enjoyed the referenced article...particularly enjoyed the methods. But I don't understand?...
"The parameter Mtip is not the total stick mass. Rather, it is the inertial resistance to sideways motion that the tip possesses. This effective mass Mtip is sometimes called the endmass...It is clear from the last expression that the individual endmass and ball mass values are not important, but rather it is only the ball mass to endmass ratio that matters."
It appears that the article is drawing an effective parallel between mass and inertial resistance to force...is this done so the reader may quantify additional values at some later date using this "mass" as a component for some kind of thrust calc that may actually define the curve of the resistance of different shafts?
What seems to be the prevailing conclusion from the methods of this study is that the value of "endmass" equals the weight of the tip or last 6" or so of the shaft and that this is the most significant factor in the actual resistance to sideways motion. I wonder if weight has so strong a correlation to this resistance as does, say, the material used, or better yet, the combination of the material and the chosen structure. Surely, at the level of establishing paramaters for initial consideration; weight may serve as a proxy for clarity but under more rigorous analysis of the elements, other factors would quickly show more promise as leading contributors to the phenomon. Particularly those whose results do not approximate experience. Possibly this is the source of the volume and voracity of the debate on this issue. If I set up a quick experiment where we take a given structure (1 unique shaft) and test its "inertial resistance to sideways motion" at the tip by measuring the "impulse" thrust required to move it a specified distance I think we would find that the location of the bridge/fulcrum would have a much greater effect on the "endmass" than adding or removing weight that might fall within the limits of reasonable possibility. My experience tells me that shortening up my bridge distance allows me to more accurately aim. I am a great believer in the scientific method and great admirer of those who follow it but it is not without its traps. A cursory study of history will provide ample evidence to support this.
As you may suspect, I take issue with several other premise forwarded in this article. We can address them another day in another thread.
http://www.sfbilliards.com/Shepard_squirt.pdf
I first heard the term “deflection” a couple of years ago and had to shake my head in disbelief at “the straining at a gnat while swallowing a camel” feeling I got at the explanation received. I have come to understand that the explanation was flawed but my impression has not abated. I posted this excerpt in the cue gallery and got no direct rebuttal so I decided to post it again, properly titled, to generate discourse and understanding.
I really enjoyed the referenced article...particularly enjoyed the methods. But I don't understand?...
"The parameter Mtip is not the total stick mass. Rather, it is the inertial resistance to sideways motion that the tip possesses. This effective mass Mtip is sometimes called the endmass...It is clear from the last expression that the individual endmass and ball mass values are not important, but rather it is only the ball mass to endmass ratio that matters."
It appears that the article is drawing an effective parallel between mass and inertial resistance to force...is this done so the reader may quantify additional values at some later date using this "mass" as a component for some kind of thrust calc that may actually define the curve of the resistance of different shafts?
What seems to be the prevailing conclusion from the methods of this study is that the value of "endmass" equals the weight of the tip or last 6" or so of the shaft and that this is the most significant factor in the actual resistance to sideways motion. I wonder if weight has so strong a correlation to this resistance as does, say, the material used, or better yet, the combination of the material and the chosen structure. Surely, at the level of establishing paramaters for initial consideration; weight may serve as a proxy for clarity but under more rigorous analysis of the elements, other factors would quickly show more promise as leading contributors to the phenomon. Particularly those whose results do not approximate experience. Possibly this is the source of the volume and voracity of the debate on this issue. If I set up a quick experiment where we take a given structure (1 unique shaft) and test its "inertial resistance to sideways motion" at the tip by measuring the "impulse" thrust required to move it a specified distance I think we would find that the location of the bridge/fulcrum would have a much greater effect on the "endmass" than adding or removing weight that might fall within the limits of reasonable possibility. My experience tells me that shortening up my bridge distance allows me to more accurately aim. I am a great believer in the scientific method and great admirer of those who follow it but it is not without its traps. A cursory study of history will provide ample evidence to support this.
As you may suspect, I take issue with several other premise forwarded in this article. We can address them another day in another thread.
