In a message dated 10/2/2003 6:52:22 AM Pacific Daylight Time, <mailto:[EMAIL PROTECTED]>[EMAIL PROTECTED] writes:* In 1991, he [Tom Wishon] and Jeff Summitt co-authored the book "Modern Guide to
Shaft Fitting". If you plot their DSFI formula, it relates frequency to
torque for the same subjective "stiffness".
* In 1996, Tom's "Modern Clubfitting" book has a table of RSSR numbers that can be similarly plotted.
When you plot both of them, you can see that he felt torque was less of a factor in 1996 than he did in 1991. His view has been changing over time. (That's not a bad thing. We live and learn. I certainly have learned a lot about how golf clubs work in the last 5 years.)
DaveT
At 10:13 AM 10/3/03 -0500, John Kaufman wrote:
Some years ago I took Dynacraft's course titled something like Advanced Shaft Technology. There was quite a dicussion about their DSFI emperical fitting equation. I remember one of the terms in the equation was the fifth root of torque. The fifth root of any small number such as a typical torque value is a number slightly larger than one. I thought it was a rather insignificant term but I had a calculator with me so just for the fun of it I cranked in a few numbers. A one degree change in torque changed the desired frequency by 10cpm. That surprised the hell out me and I'm not sure I really beleive it. It almost sounds like if we switch from a typical graphite (4 degrees or so) to a typical steel shaft we'd be down near lady's flex.
John,
That's what I was talking about. Jeff and Tom derived the equation empirically in about 1991, when Tom was at Dynacraft. When he left to become CTO at Golfsmith, he developed RSSR as an answer to DSFI, which Dynacraft "owned". Jeff has chosen to freeze the formula for DSFI, while Tom has chosen to continually evolve RSSR. Each of the decisions makes sense in its own context.
Anyway, it is not hard to plot curves of frequency vs torque for a given DSFI or RSSR. The DSFI formula is published (as you noted), as is a comprehensive table of RSSR. I have done both in the past, and might be able to dig out those notes. Anyway, when you go through the exercise, you find that the 1991 DSFI gives a lot more weight to torque than does the 1996 RSSR.
That was my point.
DaveT
