Lloyd says there no torsional deflection of the shaft during the downswing, while Pat says...
At 09:14 AM 3/20/03 -0500, [EMAIL PROTECTED] wrote:
After watching and listening to many tour players over the last 5 years as lower torque shafts have found a way into their bags, I'll offer that the low torque shaft has a very noticable effect on dispersion, and very little effect (if any) on all other emperically measured parameters.
I decided to try a calculation to see if I could quantify any of this. If there are engineers out there who could double-check what my calcs, I'd appreciate it, because it has been a while since I did of these where units mattered. (BTW, I used MKS, now called SI, units.)
What I wanted to do was find the moment of inertia (I) of a driver head, and see how much torque it would take to rotate it 90* (that is, square it up) in the last 20% of the downswing. I was assuming that the last 20% of the downswing is where the hands of Pat's tour players would release and turn the club. So my starting approximations were:
The driver head is a thin-walled ellipsoid of revolution about 4" in diameter and 200 grams in mass.
The club turns 90* (pi/2 radians) in .05 seconds.
Assuming for simplicity that the torque is constant over the .05 sec, I got a torque of about a quarter foot-pound needed to square the clubface. What does that imply about shaft twist?
Well, a shaft rated at 4* torque would twist 4* upon application of a torque of 1 foot-pound. So such a shaft would twist about 1* under the quarter foot-pound of torque needed to square the clubface. That would probably:
* Be a negligible twist for most golfers to notice. Anyway, most golfers wouldn't have such a late release, so the torque would also be smaller, making the twist even smaller.
* Be enough for a tour player to start noticing dispersion, since they expect to hit it exactly where they aim; one degree off is a much bigger deal for them than for me. Cutting the "torque" rating of the shaft in half (making it twice as stiff torsionally) could reduce dispersion that a tour player might notice.
So maybe they are both right, Pat about the tour players and Lloyd about the rest of us.
BTW, this is not to challenge Greg's (and others') assertion that the main effect of torque rating is feel. Just trying to quantify the apparent disagreement between Lloyd and Pat on the performance aspects.
Just a thought. DaveT
