All, I have enjoyed the discussion of spines and devices to find them. I believe we have missed some critical considerations in this discussion in favor of focusing predominantly on flex variations around a shaft. The suggestion is that frequency or flex variations around a shaft are the critical factor in determining the location of spines and NBP's. I believe this is an inaccurate representation of what spines and NBP's were intended to describe. See Bill Days article on this in the Shoptalk archives at http://clubmaker-online.com/spines.html., which is generally considered an accurate representation of what the spine phenomena is all about.
First, the definition of a spine and/or NBP (neutral bending position) is not related to the highest flex and lowest flex or frequency positions around a shaft in his definitions. Rather, spines are defined as the position of highest resistance to bending and a position of highest shaft instability. NBP's are defined as positions of least resistance to bending and the position of highest shaft stability. This can easily be felt in just about any bearing spine finder, like Colin Dick's. In Ed J's Feelfinder, or my Neu-finder's, there is also a deflection reading provided in thousandths of an inch, providing a magnitude for what you feel as you rotate the shaft. IMO, these simple devices find spines and NBP's more accurately and holistically than any other device. This is because they do so as a shaft is dynamically flexed, much as it would be during the downswing, and because they locate a stable shaft orientation that reflects a combination of both shaft geometric inconsistencies and flex variations. As a shaft is flexed over the bearings it immediately seeks the position of least resistance to bending. This is the NBP. A more descriptive name for the NBP might be MSBP (most stable bending position). A more descriptive name for spines might be MUBP (most unstable bending position). In a type 1 shaft, typical for steel, what these devices are predominantly locating is most likely a bend in the shaft. In a type 2 shaft, typical for graphite, they are most likely finding a combination that reflects both shaft flex in that plane and shaft geometric inconsistencies. This is due to the fact that the bearing spine finder reacts to the both geometric anomalies of shaft construction, such as a bend in the shaft, a lack of concentricity in the shaft, etc. and to flex variations around the shaft. This is exactly what we want them to do, in my opinion. We should not ignore these geometric anomalies in favor of considering only the "true flex or frequency" measurements of the shaft, especially since nearly all shafts have these geometric flaws. After all, what we are after, in terms of shaft orientation, is the most stable or neutral position for the shaft to bend in as it is deflected during the swing. To ignore what the simple spine finder tells you about both the shafts flex and its geometry could result in positioning your shaft in an unstable orientation. One in which the shaft wants to torque away from the bending plane, much as it does in the spine finder when you rotate the shaft over the MUBP or spine. The question of how to orient the MSBP/NBP to the clubface is another question entirely, and one that needs much more research. The majority of shaft orientation aficionados seem to believe that the MSBP/NBP toward the target (or at 9:00), orienting the clubface at 90� to the swing plane coming into impact, is the optimum clubface/shaft orientation. Others would argue that the shaft spends more of its time during the downswing with the clubface in positions other than 90� to the swing plane (for example as you start the downswing it is closer to parallel to the swing plane), therefore the "down the target line" orientation is not optimum. Still others would argue that the shaft is actually bending forward at the point of impact, so the MSBP/NBP should be at 3:00 or facing away from the target. All these orientations should be further tested with an eye toward discovering which orientation returns the clubface most accurately and consistently into impact, thus making the shaft "neutral". It seems to me that we should be considering all aspects of what makes a shaft become stable or unstable in certain orientations and what makes it "prefer" to bend in certain positions over others. I see no reason to ignore shaft geometric inconsistencies in favor of considering only flex variations. For these reasons, I believe simple spine finders are a must use for any shaft orientation effort. I hope this makes some sense. Happy New Year to you all! Dan Neubecker [EMAIL PROTECTED] > -----Original Message----- > From: Bernie Baymiller [mailto:[EMAIL PROTECTED]] > Sent: Tuesday, December 31, 2002 8:19 AM > To: [EMAIL PROTECTED] > Subject: Re: ShopTalk: shaft flex v.s. frequency > > > Alan, > > The GS spine studies are discussed in a GS Clubmaker article in the > September/October 1999 issue on page 18, authored by john a. > meng who has > included many comments by Tom Wishon. Good article. > > Bernie > Writeto: [EMAIL PROTECTED] > > ----- Original Message ----- > From: "Alan Brooks" <[EMAIL PROTECTED]> > To: <[EMAIL PROTECTED]> > Sent: Monday, December 30, 2002 6:11 PM > Subject: Re: ShopTalk: shaft flex v.s. frequency > > > > Thanks for that info Al, do you have any idea where I could find > > information on what was done? Either by TT and/or Golfsmith? > > > > Alan > > > > At 04:00 PM 12/30/02 -0500, you wrote: > > >Alan, > > >We went through the 1/2 cycle discussion several years > ago. You might > > >want to look at True Tempers research that they did with > their Shaft > > >Lab. It is amazing what the head does in the last few > milliseconds prior > > >to impact. Toe Bob, I think, is what they call it. They > found that pros > > >had much less to nil amount of toe bob, compared to amateurs. They > > >figured it was their ability to maintain a load on the > shaft, due to > > >continuous acceleration, into impact. The concept of > spine aligning, > > >which was later indicated by tests done by Golfsmith, > tended to minimize > > >this bobbing affect. The results were more "on center" > hits. This, in > > >effect, made for longer hits, by way of reducing distance > loss due to off > > >center hits. It's a maddening game some of us play, trying to fit > golfers. > > > > > >Al
