New Shaft Testing Equipment Added to Hireko’s R&D Lab

Santa was especially kind to me this year and delivered a new piece of equipment (called an EI shaft profiler) to augment the equipment we already have on hand to educate you more on the proper golf club shaft choices.  See, it pays to be nice!  If you are not familiar with EI (short for elasticity times inertia), as few will, it is a 3-point bending test that measures the golf club shaft deflection along a span of the golf shaft. By taking measurements from the tip to the butt and plotting the results provides a more comprehensive look at the golf shaft’s stiffness distribution and a better understanding of how that shaft will react.

I began scientifically testing shafts in 1989 to more accurately compare one from to another. In 1991, I created the DSFI (Dynacraft Shaft Fitting Index) formula as a way to accurately compare shaft stiffness based on the interrelation between golf club frequencies and torque that is still published annually to this day. That was the first year the data was published to help fellow golf clubmakers fit more precisely. In 2006, I expanded it one step further and started compiling tip and butt deflections measurements and added them to the DSFI formula.  This would provide a much clearer picture as how two shafts, that at least on paper appeared to be the same, could be actually quite different.  With the addition of our EI shaft profiler, we hope to provide you with more accurate shaft fitting for years to come.

It will take a while to compile all the data and put in into a format that will be easy for our customer base to understand and use.  I wanted to let you know we don’t rest on our laurels and hope to expand our knowledge base so that we may increase yours too.  Here is a snippet with a comparison of three cut #5-iron shaft deflections. All are of the same length, frequency and weight but completely different shaft stiffness distribution profiles.

The left side of the chart represents the tip and each of the 14 data point’s measures 2” closer to the butt.  The lower the reading; the stiffer the shaft is at a certain point.  For example, Series 2 (or the shaft in red) has a much stiffer tip section that the other two, but is more flexible in the butt end.  This shaft should produce a lower golf club launch angle, while the shaft in green will produce the highest golf club launch angle as they exhibited at the range. That is how to interpret the data.


  1. DaveT says:

    Glad to see you’re getting into profiling. I have a few questions and a comment:

    Comment: EI does not mean “energy and inertia”, it stands for “elasticity times inertia”. It is the modulus of elasticity of the shaft material times the geometric moment of inertia of the shaft’s cross section. It has been around for a long time. Engineers have used it to express the flexibility of a beam for over a century.

    Question #1: What is the span you use for measurement? It looks from the picture like it’s about 10″.

    Question #2: On the graph, which end is the tip? I suspect it’s the left side. If so, isn’t the vertical axis deflection, not EI? (Deflection is the inverse of EI.)

    Question #3: Still on the graph, what does the measurement on the horizontal axis represent? You CAN NOT get the load within 1″ of either end of the shaft, so I don’t see how you get a 1″ reading.

    Question #4: Is that Russ Ryden’s EI instrument? Sure looks like it. Definitely the best around.

    For more on EI measurement, see my article at While we’re here, Jeff, look at, the fourth and fifth pictures down; you’ll see some familiar faces.

  2. Jeff Summitt says:


    Q1, changed – thanks for the correction.
    Q2, 10″, This is a graph of the deflections readings rather than the EI, which as you said is the the inverse
    Q3, Those are data points and not actual measurements as the 1st data point is 6″ from the tip.
    Q4, Yes

  3. Trae says:

    So will the DSFI still be produced or are you coming up with a new expanded system using this new data?

  4. Jeff Summitt says:


    We will continue with the DSFI, but it might be augmented or changed in the future. It will take several hundred hours (if not over a thousand) to retest the shafts I have using the new machine so it is still too early to say how it may affect future publications.

  5. Trae says:

    Sounds like it is time for you to add an Intern.

  6. Rusty says:

    That looks like something I built a few years ago. Glad to see it landed somewhere were it will see some use. See you at the PGA show next week.

  7. Joe says:

    Good work. I’ve seen similar charts on manufacturer’s websites, but it was sometimes confusing to me as to what the chart meant, as it isn’t necessarily explained to the consumer.
    I wasn’t even sure which end of their charts described the tip and which the butt. Plus, I thought that the higher on the graph, the stiffer, though their charts may be frequency and not deflection.
    Looking forward to the day you expand the DSFI to include the new info.
    I still have the books (yes, paper books) which I purchased from Dynacraft about twenty+ years ago describing the DSFI stuff, how it all worked, including a limited number of shafts such as the Aldila HM series that was popular back then, written long before most present day shaft companies even existed.

  8. […] twenty plus years, you would already know this isn’t always the case. Plus I recently acquired a new toy (called an EI Golf Shaft Profiler)  for my R&D lab that examines shafts better than what I had been using and I wanted to test a […]

  9. Chris Joyce says:

    Hi Jeff,

    What is the manufacturing company called of the EI shaft profiler, and what country do they originate? I’m writing my PhD literature review, and have included EI testing methods.

  10. Jeff Summitt says:


    The devise originated in the US from Russ Ryden at Fit2Score. There were only 15 units made and that was it.

  11. Gene W Wines says:

    Hi Russ: I haven’t hear from you in ages, I have not visited any of those old dialogue message sites in ages. I got a little wore out with all the hub-hub. Are you still in Dallas? Next time I go to TCU, I will let you know and maybe drop in and see what a golf lab is to the world. Oh to be YOUNG again..

    Take care drop me a line once in awhile, when your not busy. I am not going to the PGA Show, my old hips are wearing out.
    You know you have to do a lot of walking down, their, I have been so many times, and with the weather improving here in Cypress, I can play golf, here it was about 70 today, lovely out on the course. Gene “The Machine”.

  12. […] gram). For you techno-geeks like me, let’s provide you with some comparative data. Using our new shaft profiler, we are able measure the deflection or stiffness along the length of the shaft so you get more of a […]

  13. Mario says:

    How much does the equipment cost?

  14. Jeff Summitt says:


    It is best to contact Russ at Fit-2-Score directly for pricing and availability.

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