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Measuring Instruments and Shop Tools
Do-It-Yourself
Digital Swingweight Scale
The
swingweight scale market is going digital. There are a bunch of digital
swingweight scales on the market today. They are all priced at
$330-$350. You can get a less
expensive swingweight balance with a sliding weight for $50-$150; they
are accurate enough, but slower and harder to read.
Or
you can make your own digital swingweight scale. Here
are plans for a digital instrument, where the parts cost is
about $50.
Modify Your Swingweight Scale to
be Digital
After
I posted instructions for making your own digital swingweight scale, I
started getting questions about modifying a conventional swingweight
scale to be digital. Yes, it can be done, and here is how.
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.
Errors
in EI Measurement due to Shaft Weight
Instruments
that measure EI tend
to use substantial forces to load the shaft, forces way more than the
weight of the shaft. For that reason, the shaft weight is usually
ignored, on the assumption that it is negligible compared to the
loading force. In fact, the errors are not necessarily negligible. This
article gives an estimate of the errors introduced.
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.
Do-It-Yourself
Shaft Puller
This article is about a Shaft Extractor, a tool that helps a clubmaker
remove a shaft from a clubhead. The featured tool is one you can build
for yourself. The original idea (including the key components) comes
from Ron Blanchard, and I modified his initial prototype to be easier
to build and more practical to use.
Do-It-Yourself
Hosel Boring Fixture
If
you ream out or re-cone hosels, it is easier, smoother, and an overall
better job if you use your drill press and a hosel boring fixture. But
the fixtures are expensive enough that most clubmakers do it with a
vise and a hand drill. Here's a hosel boring fixture you can build
yourself for less than $20 in parts, and it does the job just fine.
Club
Ruler - New vs Old
As of 2004, the USGA and R&A introduced a Rule specifying how
the
length of a golf club is to be measured. Rather than measuring with to
sole at the actual lie angle, it imposed an angle of 60º. Since then,
clubmaking tool catalogs have seen new club rulers designed to the new
Rule. The question arises: "How different are the measurements of the
old ruler and the new ruler?" This article answers that question.
Does
averaging stats work?
In
golf research (and other types of research as well) we often find data
available in the form of averages over a lot of trials. (A good example
is PGA Tour stats.) It is seldom the raw data for each individual
trial, unless we did the experiment ourselves. Is it valid to use such
averaged data to test or even derive mathematical relationships?
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.
Focal
Plane Distortion of Shaft Bend
Pictures
of shafts bending often have the bend exaggerated, due to the way
digital cameras and even focal plane shutters work. Here is what causes
the distortion, and a way to take photos that minimizes the
exaggeration of bend.
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. Since
that model, we have released a NF4.1 (an upgraded load
cell and readout) and an NF9 (an improvement in ease of
construction and use, but no new capability). We keep
talking about a complete rework and improvement, but we're both very
busy and it stays on the back burner.
There was actually a business model for the NF4. Tim Hewitt, the owner
of MyOstrich Golf, sold the construction plans and user manual for $35.
Actually, the documents resided on the MyOstrich web site, and Tim sold
access to them. Dan and I sometimes got reimbursed for actual expenses
incurred in development, but the business was pretty much a non-profit.
At this point, MyOstrich Golf is no more, Tim has moved on to other
things, and Dan and I don't want to run the NF4 as a business. So until
the future NF comes along (and perhaps a new business model with it),
we are making the plans freely accessible -- along with the technical
articles that have long resided on my site.
NF4
and 4.1 Documentation
The
complete construction plans and user manual.
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 - Introduction
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.
Shaft
Deflection Profiling - Better Plotting
It
is difficult to learn much about a shaft profile from a raw plot of
deflection vs beam length. In the previous article, I introduced the
notion of transforming the raw deflection load data to make the graph
easier to read. Here is a much-improved data reduction transform. It is
easier to understand, as well as no longer dependent on measuring some
"standard" shaft. Instead, the data is subjected to a simple
calculation not based on comparison with any other shaft.
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.
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