Measuring Instruments for Golf Clubs

Dave Tutelman's Frequency Meter
In early 1996, I decided I really needed a frequency meter. Since most of my degrees are in Electrical Engineering, it was only natural that I should build my own. Here are the schematic diagrams for the circuit, along with a bunch of photos of the finished product. You might find the design of the clamp interesting, even if you don't build the circuit.

Frequency Matching With a Meter
The question comes up every month or so on various golf forums: "I just got a frequency meter. Now... how do I build a frequency-matched set of clubs with it?" Here's how I do it. It may be a little different from others, but it works for me.

Let's also keep in mind that this article does not deal with: How do I choose a frequency or frequency slope? That's a design issue. This article is limited to shop practice. It assumes you know the frequencies you want, and describes how to build the clubs to those frequencies.

Dave Tutelman's EI Machine
An EI machine shows a shaft's flex profile as the stiffness at the point where the measurement is taken. That may or may not be the best way for custom clubmakers to look at a profile, but it definitely is the way shaft design engineers see profiles. This article describes an EI machine I made and use, and the design considerations that went into it.

Testing a Digital Scale
In working with golf club instruments, sooner or later you will encounter a digital scale or force meter. And you may well have reason to want to test it, to see if it is accurate. Most of us don't have lab standard weights around the shop, but it is possible to give the scale a pretty good test with things you are likely to have on hand.

Precision, Accuracy, and Resolution
Too many people use the terms "precision" and "accuracy" interchangeably. They shouldn't. Precision and accuracy are completely different concepts. Let's explore what they really mean, and how to tell the difference. While we're at it, we will also throw in "resolution", which is also too-often confused with precision.

NeuFinder

The NeuFinder 4 (NF4) is an instrument to measure shaft flex and flex profile. It uses deflection rather than frequency. It is a major improvement to Dan Neubecker's original NF and NF2, which were not digital and, more importantly, not capable of being calibrated. I got involved with Dan when the NF2's weaknesses became apparent. We engineered the NF4 to allow calibration (so owners can exchange data) and to facilitate flex profiling. Most important, it was designed to allow a lab-quality instrument to be built by home craftsmen. Dan and I are now working on future enhancements, and we are pretty sure there will be an NF8 or higher.

The NeuFinder has its own web site, but some technical articles about it are here:

NF4 Load Reading vs Frequency
There is ample reason to want to be able to convert between the load reading from an NF4 and the corresponding frequency of the shaft. There isn't a simple conversion, but here is a pretty good estimator.

Shaft Deflection Profiling
I have been using the NeuFinder 4 to profile shafts. Frequency profiling ("zone frequency") is a concept that is evolving and starting to catch on. This article shows that deflection can be as good or better than frequency for "zoning" a shaft. It also introduces some data reduction (which works for both deflection and frequency) that highlights the profile differences between shafts -- which might otherwise be masked by overall stiffness differences.

Calibration Shaft Variation
As people have been building their NeuFinders, they have been posting the profile of their calibration shaft, as measured on their NF4. It turns out this can be a good sanity test, and has helped in finding and fixing bugs in a couple of machines. Here is a sample of six calibration shaft profiles for reference purposes.