I posted a thought on this a while ago on SpineTalk that questioned if we should really be looking at expansion and compression values of separate shaft walls located 180* from each other. (view this as a plane where we take into account 2 compression values located 180* apart as well as 2 expansion values located 180* apart). I snipped some conversation from it below. Remember a lot of this is thought and I am looking for insight.
For this, lets presume we have a tough Type 1 shaft that has equal freq
and basically equal FLO in all directions, but exhibits a spine and a NBP. First lets picture a shaft in an upside down U deflection position (like in a Colin MKII or a NF2). As shafts are hollow, we must presume there is a possibility that each wall of the shaft could act differently. In the above referred position, the outside of the curve we will call Wall A, the inside of the curve we will call Wall B.As flex is really a dynamic idea, we need to realize that flex is not merely the resistance to compression of one side (ie: wall) and the resistance to expansion of another, but the resistance to compression and expansion characteristics of Both Walls, 180* opposite each other, simultaneously and how they interact with one another. For a shaft to have equal freqs at 180* to each other, the sum of the resistance to expansion of Wall A and the resistance to compression of Wall B must equal the resistance to compression of Wall A and the resistance to expansion of Wall B. Lets assign arbitrary some values to aid in this with:
Expansion Compression
Wall A 6 7 Wall B 3 4 and 2 other walls at 90* to the original walls Wall C 5 6 Wall D 4 5 Now lets start to look at this how it relates to what we feel in a spinefinder. What we now feel as the "bump" is where the value of Wall A Expansion is above any other point in the shaft with the corresponding Wall B Compression being below any other point and Wall A Compression is above any average point. What we now feel as the "resting spot" is where the value of Wall A Expansion is below any other point with the corresponding Wall B Compression being above average and Wall A Expansion is below any average point. FLO in this shaft example I believe exists when the following condition exists: 1. Wall A Expansion and Wall B Compression closely equate to Wall A Compression and Wall B Expansion WHILE no other closely located plane of walls exhibit a closer value.
Needless to say, this can easily be expanded to better qualify shafts
that have unequal freqs 180* from each other as well as better classify FLO in those shafts.
I had a hard time describing what I was thinking then. Maybe we can discuss at the PGA show.
Mark
Al Taylor wrote:
Alan,
Thanks for the explanation. It seems to make more sense that way. Question: You have a table or statue or any other object that stands on legs. One leg is made of steel the other is made of paper. It falls over into the leg of paper. Why the paper leg and not the steel leg? I am smart enough to know this is too simple to apply to shafts, so await the dressing down. Is this not similar to the two sides of a shaft? As Dave referred to, it seems intuitively that it would bend in one direction more easily than the other, though in reality it doesn't. I may get out of 9th grade physics yet.
Al
