Dave I appreciate you asking me for some comments. Just as each of you experienced indivduals, are doing, this spring, too damn cold now(23* this morning), I want to apply Six Sigma testing capabilties to shaft spining-frequenzy. I feel I am not good enough a player to be consistantly repetitive to distinguish testing. But I do have those around me that are good enough that are worthy of testing with good results. Six Sigma is designed as a testing medium that looks like it would be perfect for this type of testing. It lets you look at a number of attributes at the same time and lets you distinguish between each of them. And I do want to load some good shafts with some knowingly predictable (bad) shafts. I want to know exactly what does a bad shaft do. And then I want to know what does a good shaft do. I want to classify good shafts, so that I can predict what part shaft orientation plays. I know that many of you already have and are doing this now. I would appreciate any help into how to lay out the test and any info that you have already derived. Also I want to test club heads designs so that I know which club heads are best for what kind of fairways. As you can see, I have many quetions with few answers. Building clubs started out as a hobby, and now has turned into a passion for knowledge. I guess this shows my ignorance, but that has shown many times before. So what's new. Thanks Reed ----- Original Message ----- From: "Dave Tutelman" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]> Sent: Tuesday, December 24, 2002 5:41 PM Subject: Re: ShopTalk: shaft flex v.s. frequency
> I guess sometimes it pays not to respond too quickly on a high-volume > topic. Somebody else writes a note that serves your agenda well. (See > Bernie, I DID notice. :-) > > This time there were at least two. I'm responding here to: > * John Kaufman's statements about spine and bent shafts. > * Charlie Badami's invitation to comment about bent shafts. > * An unspoken but underlying question about NeuFinders as spine finders. > > At 09:56 AM 12/24/02 -0600, John Kaufman wrote: > >I just stick a shaft in my Club Scout clamp and check the frequency. I > >then loosen the clamp and rotate the shaft a few degrees. If the frequency > >goes up I'm moving in the wrong direction so I immediately rotate the > >shaft in the other direction. I keep doing this until I get FLO in the > >minimum stiffness (frequency) plane. I don't tweak it forever to get it > >down to 1 degree alignment. This is the old process of measuring with a > >micrometer and cutting with an axe. > >...I took a pretty crummy shaft a few minutes ago and found the plane I > >was looking for in 15 seconds. It's not a big deal. > > That's a little faster than me. Takes me about a minute. But it gives the > REAL spine, not an indeterminate combination of spine and "geometric > imperfections". Bernie, when I used that term earlier, bend was uppermost > in my mind. But out-of-round will also spoof a bearing-based spine finder. > I suspect bend is the most likely culprit, though I'm not sure. > > And what John says about not needing alignment to a single degree makes a > lot of sense. > > >We talk a lot about type 1 shafts, I prefer to just call them bent. > > YES!!! > I've been saying this ever since spines were first mentioned on RSG. > Probably something like 6 years. I'm delighted to hear another engineer, > and a very knowledgeable one, speak up. Hey, Reed, what about you? > > My position is that any structural beam (like a golf shaft in bending) is > either equally flexible in every direction or has two axes of flat > oscillation, a hard one and a soft one. This has the following interesting > properties, assuming the tensile and compressive moduli are similar (which > they are in shaft materials -- and just about identical in steel): > > * The hard and soft planes are at right angles. > > * The two planes are the planes of the highest and lowest frequencies > that the shaft will vibrate. > > * Deflection stiffness is THE SAME IN BOTH DIRECTIONS in each of these > two planes. > > The last point is the one that says what John just said. If you have an NBP > in one plane and no NBP 180* away from it, then you don't have a real NBP. > Same for a spine. Every structural design book I've ever seen says so, and > it's not hard to derive from the first couple of weeks of any structural > engineering course. But it's counter-intuitive to the point of unbelievable > for anyone who hasn't gone through such a book or course. > > As for empirical evidence, look at the "bow tie" graphs that John plotted > in his tech notes, http://www.csfa.com/techframe.htm. These are shafts that > looked like type 1 on spine finder and deflection board, but showed > behavior consistent with the theory when the differential deflection was > measured rather than the absolute deflection. (The differential deflection > measures stiffness; the absolute deflection measures stiffness plus bend.) > > >What I'd like to hear about is some testing that indicates aligning an > >otherwise very uniform stiffness shaft that is simply bent ( generally all > >steel shafts) has any effect on the clubs performance. I know of three > >sets of tests that indicated no effect on performance from alignment of a > >type 1 shaft but I've not seen any data on tests that indicate alignment > >did improve performance. > > That's certainly what I'd expect offhand from the very small > out-of-straight of typical commercial shafts. But it's not what Charlie > reports in the very next ShopTalk post. And Charlie is an ultimate > empiricist with a very sensitive measuring instrument. > > At 09:59 AM 12/24/02 -0500, [EMAIL PROTECTED] wrote: > > I agree with your descriptions of shaft alignment and the results but > > as you know no shaft is perfectly straight and that is why I also check > > the shaft for straightness and align it accordingly. Steve Boccieri is > > perhaps one of the most knowledgeable people I know of as far as shaft > > geometry goes and we have been discussing this alignment thing for the > > past three years and he definitely says that it has effect and was > > interested in the results of the blind test I had done which had > > confirmed his suspicions. > > Double-blind? Definitely not. > Single-blind? Maybe. I didn't see the test. But Charlie is a very > expressive individual (I know you won't dispute that, Charlie), and Rich > has been working with him for a while. So I'm not at all sure that Rich > didn't "know" -- perhaps even subconsciously -- when the club was > "supposed" to be good. That why "really blind" means "double blind" in > serious human factors experiments. > > But Rich is the "sensitive measuring instrument" that Charlie uses to test > such things. He can feel differences, or detect them in performance, that I > wouldn't expect a golfer to be able to. > > Anyway, I don't know how "blind" the test was, nor how consistently the > result was duplicated. It was certainly based on only one golfer. So the > results are intriguing but not yet conclusive. > > >I ran into Dave T at the range while working with one of my players and we > >had the discussion on shaft curve and I know he will be able to explain it > >better than I. Arnie, about your comment on shaft manipulation, Rich hits > >a predominate straight ball although he is able to work the ball both ways > >on command, when I see a club continuously leave the ball hanging in one > >direction or another I believe that the shaft is not in a neutral position > >and am looking to place that shaft as neutral as I can so that he can do > >whatever he deems is necessary for each particular shot. > > We really did just "run into one another at the range". And it's a public > range, not a private club where you expect to see your friends. (BTW, that > suggests that we're enjoying plausible weather for late December in NJ. We > are; I golfed twice in the last 5 days. Well, I went out with clubs on the > course anyway. It's artistic license to call it golf. :-) > > The "neutral position" makes a certain amount of sense, if you assume that > small a bend has any effect at all. I wouldn't have guessed it, but Rich > claims to feel it. My explanation below is based on intuition, and a mental > exaggeration of the bend to something much larger. Since we all know by now > how misleading intuition can be when discussing golf physics (for instance, > see "Type 1 = bent" discussion above), let's not assume this is actually > correct, but rather just a first hypothesis: > > The most violent motions of the clubhead during the downswing > occur in the last fraction of a second (probably about 50 milliseconds) > before impact. Particularly in a good swing, the clubhead is "releasing"... > that is, it is actually pulling the shaft into a forward bend. The wrist > usually can't uncock fast enough to keep up, so a light grip does the least > damage. So let's look at what is probably happening during this critical > period. And we'll imagine a seriously bent shaft, just so we can visualize > it more easily. Unfortunately, the actual effect with a small bend may be > qualitatively different. Also, this argument doesn't quantify the effect > enough to know if anybody -- or maybe anybody but Rich -- is affected by > the actual bend one experiences in real shafts. > Late during this release time, when the clubface is square to the > ball, the bend may be described on the clockface for a right-handed golfer, > as we often do when talking about spines. Let's look at the cardinal points > of the clock for bend: > 12 o'clock: clubhead wants to pull the face shut. > 3 o'clock: clubhead is unstable; might "jump" either way. > 6 o'clock: clubhead wants to pull the face open. > 9 o'clock: clubhead wants to pull the face straight ahead, square. > > I'm pretty sure Charlie said he found that the 9 o'clock position was the > "neutral" one. This agrees with the hand-waving I've done above -- and it > is still in the realm of hand-waving as far as I'm concerned. We didn't > have time to discuss the specific results of the other compass points; > Charlie, does the explanation correctly predict what you observed? > > One last comment. (BTW, I hope that NeuFinder discussion groupies are also > ShopTalkers, because I'm not cross-posting this.) > > The discussion above about bent shafts strongly suggests that the NeuFinder > does not find a true spine as a spine-finder, but is spoofed by geometry. I > believe that to be completely true. But you CAN use a NeuFinder as a > spine-finder if you do it right. Unfortunately, this process is more > tedious than what Bernie and John and I attribute to finding spines with a > frequency analyzer. > > You have to find NOT the direction of minimum dial reading, but minimum > difference in dial reading for a known change in deflection. That means you > have to take two dial readings at each interesting rotation, and compute > the difference in readings. The direction with the smallest difference is > the NBP. > > John explains in his tech notes how he did this with a V-block added to his > inverted flex board. Dan has designed a reversible bearing to to the same > thing more conveniently. I'm sure he'll post it if there is enough interest > in going to this precision. > > Have a happy holiday, all! > DaveT > > > >
