Lessons from ShaftLab

Dave Tutelman -- October 20, 2007

In the early 1990s, the R&D lab for TrueTemper shafts came up with a measurement tool they called ShaftLab. Its purpose was to find out more about how golfers bend the shaft during the downswing. It did that job admirably. In fact, it created such a stir that TrueTemper decided to market it to clubfitters as a high-end shaft-fitting tool. They have indeed sold some, though it is hardly common to find one in a custom club establishment. It is still too expensive. Also, it is limited in function for the price; it is closer to cost-effective as a research tool, which is how it started its life.

This article covers what we have learned from ShaftLab. I am an engineer, and I wrote the article from an engineer's point of view. There aren't any equations. But if graphs throw you for a loop, you may have trouble with it. For you, the conclusions are stated concisely in the Executive Summary on this page. But understanding how we come to these conclusions will require wading through the graphs and the physical reasoning.

Contents

  • Executive summary. Just the facts, ma'am.
  • What ShaftLab is. How it works, what it can do, and what it can't tell us.
  • What TrueTemper learned. In 1994, Ed Weathers of TT wrote an article for Golf Digest explaining what he believed ShaftLab taught us about shaft bend.
  • Lessons from the data. We can deduce things from looking at the traces, including lessons that Weathers' article did not cover.

Executive Summary

This section simply states the lessons that ShaftLab has taught us. To learn how ShaftLab works and how we gleaned these lessons, you will have to read the rest of the article:
  • Just about all swings of real golfers fall into one of three profiles:
    • Double peak
    • Single peak
    • Ramp
  • Clubhead speed is not a reliable indicator of how much you bend the shaft.
  • The biggest factor in shaft fitting is maximum bend of the shaft. This seems to be TrueTemper's conclusion; I'm not sure I agree with it.
  • Changing shaft flex does not increase your clubhead speed.
  • "Kick velocity" does exist, but it isn't a very large component of clubhead speed. For good swings (like the pros'), kick velocity is at less than 5% of their clubhead speed.
  • The biggest bend during the swing is between toe-up and lagging, and occurs sometime near the beginning of release.
  • At impact, just about every golfer has the shaft bent with clubhead lead (shaft bent forward) and toe droop.
  • Bend at impact is influenced by a lot more than just "centrifugal pull" on the center of gravity of the clubhead.
  • Frequency is useful as a measure of shaft stiffness, but don't read too much into it. For instance, it is not an indicator of the "free response" of the shaft during the downswing.
  • At impact, the net bend of the shaft is nowhere near the target line.


Last modified  10/27/2007