Measuring the Golf Shaft

Several years ago I learned the term EI from engineers in the business of designing shafts. The instrument most used was in the $10K+ range, and therefore not affordable to most. Not even all shaft companies had these instruments. It took about 2 years to come up with the original affordable EI measuring design. I relied on gravity,removing the cost of hydraulic pumps and controls. The shaft profiles on GolfShaftReviews shows measurements taken with the Fit2Score instrument.

After many years of use, I redesign and improved the instrument. The improved version 7 of the Fit2Score EI shaft measuring instrument is shown below. This animation show it cycling on a shaft. The Fit2Score instrument is owned by several shaft companies.


In the version 7 instrument shown here, the gauge was re-positioned to improve accuracy and repeat-ability of measurements. Positioning pins were incorporated into a manufactured weight and the lift design was simplified. A unique self centering shaft support maintains the radius of the earlier design while centering the shaft. The shaft naturally ‘falls’ to the bottom of a saddle. This makes measuring faster and much more accurate. Skillful placement of the shaft in the instrument is no longer necessary.

A hoop strength measuring fixture has been added. It provides a platform to center the shaft under the press and uses the 11 kg weight and .0001 gauge to measure hoop deformation. To measure tube deformation during the measuring process, a limited number of instruments were converted to add additional gauges. The additional deformation data allowed me to correct the EI calculation from the error inherent in using a process designed for solids on hollow tubes. That data very closely correlates with hoop strength.

Instrument owners were all given hoop measuring platforms. The new database structure includes fields for hoop strength readings along the length of the shaft. Hoop deformation is used in the EI calculation to accurately describe shaft center-line bend profiles.This pulls aside another veil of golf shaft understanding. 

Contact if you are interested in subscribing to the software used by the top golf club fitters and many golf shaft companies.

By Russ Ryden, Fit2Score, A Dallas Fort Worth Club Fitter & Club Maker
The Golf Center at the Highlands, Carrollton Texas