Dave Since for most golfers the position of the club at the top of the swing, the toe is pointed down an the clubhead face plain is parallel to the line of flight, turning the club quickly from the back swing to the down swing or pulling down hard from the top will induce a toe up deflection of the shaft out of the hitting plain. Yes, when the player then stats to rotate the club the load is released from the off axis plain and the bob starts. Look at the Shaft Lab data and you can see there is a significant toe up stress in the shaft at the top of the swing. But it dose vary with the player just as determinator accelerations vary with the player ( The way they have you orient the head of the determinator vertical at the top of the swing say the primary acceleration it is reading is at the top of the swing).
llhack ----- Original Message ----- From: "Dave Tutelman" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]> Sent: Thursday, January 02, 2003 3:19 PM Subject: Re: ShopTalk: shaft flex v.s. frequency > Let me throw in yet a different explanation. (And yes, I have looked at > ShaftLab data, though it was pre-2000 data.) > > First, about the other two theories I've seen: > > (1) Al, you would not be that far off on the deceleration theory -- if > there were enough deceleration to significantly change the velocity and > thus the centrifugal force. There really isn't, unless the swing is > terrible. The decel of the average middle handicapper probably doesn't > account for even a 5% decrease in clubhead speed from max in the downswing > to impact, not enough for the sort of toe bob we're talking about. > So, while centrifugal force is a major contributor to toe-down > deflection at impact, it probably doesn't explain "toe bob" -- which is > really a dynamic and usually unpredictable component of the toe deflection > that isn't simply explainable by centrifugal force. > > (2) Lloyd, it isn't a reaction to the toe-up deflection. Deflections and > their reactions occur in a single inertial plane. The toe-heel plane is not > an inertial plane; it rotates through the inertial reference during the > downswing. The toe-heel plane rotates from the target plane (an inertial > plane) at the top of the downswing to a plane roughly perpendicular to the > target plane at impact. So any reaction to an initial toe-up deflection > (caused by casting, for instance) would have to be in the target plane and > would not cause toe bob. > > But the argument against #2 does suggest another theory. Toe bob may well > be a reaction to deflections induced by the golfer during the downswing as > Lloyd suggests, but those deflections would have to be in the plane that is > perpendicular to the target plane and through the shaft. Let's remember > that the target plane is, ideally, also the swing plane. In other words, > any off-plane bobbles the golfer introduces during the downswing might > induce a reaction that takes the form of an unpredictable toe-heel > deflection at impact. > > Actually, that makes fair sense to me. One of the things that marks the > better golfer is that the swing is on plane... that from the pull down from > the top the shaft stays in the target plane, with no forces from the hands > pushing it outside the target plane. So if toe bob is a reaction to > outside-the-plane forces in the downswing, one would expect less of it from > the pro than the duffer. > > OK, I think I understand that. Where did I go wrong? > > Cheers! > DaveT > > At 01:16 PM 1/2/03 -0500, Al Taylor wrote: > >Lloyd, > >I hate to argue with an engineer since I am out of my league then, but I > >believe that the TT shaft lab results do show that higher head speeds have > >greater toe down. Along this area, the Pros usually are still > >accelerating into impact and, as a result, have little to nil toe > >bob. The amateur often starts to decelerate prior to impact and the toe > >then starts back up, or bobs. The TT graphs show that somehow there is > >often a series of toe ups and toe downs on the later example. > > > >I know that my irons profile is similar to pro iron profiles (wonder why > >my shot results aren't the same?) but my driver shows some toe bob. > > > >Al > > > >At 09:40 AM 1/2/2003, you wrote: > >>Royce and Alan > >> > >>The centrifugal force is certainly part of the Toe down deflection at > >>impact. Since toe down deflection is dependent on club head speed this > >>would make the better players with the high clubhead speeds have greater toe > >>down deflection ( opposite True Temper results ). What I described earlier > >>is the other component of toe down defection at impact. As can be seen in > >>all of the Shaft Lab data there is initially a toe up deflection at the top > >>of the swing. This deflection along with the time from the start of the down > >>swing to impact gives the shaft time to go through 1/3 to 2/3 cycle of its > >>natural frequency resulting in some degree of toe down deflection. This > >>resulting defection is a function of how much the club is loaded at the top > >>of the swing to produce the initial toe up deflection. Herein lies the > >>difference between the good player and the others.... > >
