[ENG]골프 샤프트에서 CPM의 이해 #골프 #골프덕후 #CPM #Flex #DIY #Frequency #match - YouTube

Traditionally, shaft stiffness has been measured using this deflection board.

I made it using a light sensor and Arduino.

Hello! My nickname is Golfduckwho who a golf buff.

Today we will look at CPM and CPM matching.

CPM stands for Cycles per Minute, which is the frequency per minute.

At normal frequency we use the frequency per second, or Hz.

Therefore, CPM is the frequency expressed as the frequency per minute.

So why use the word frequency in golf?

In golf club specs, swing weights are labeled C9, D0, etc. instead of complex numbers.

Similarly, shaft strength is usually divided into R, SR and S grades.

And there is a lot of flex tables recommended depending on the head speed.

When choosing a driver according to this, select the shaft of the same strength.

This flex rating divides the CPM from the measurement.

The shaft has its own frequency according to its strength, so the strength can be calculated by CPM.

However, the value of CPM dividing this grade varies slightly from company to company.

In golf, flex is used a lot in terms of shaft strength.

But in engineering, strength and stiffness are different concepts.

Even if the material has the same strength, the stiffness varies depending on the shape made.

Making a steel pipe is lighter and stronger than a full rod.

Therefore, the exact stiffness of the shaft is an expression.

Traditionally, the shaft stiffness has been measured using this deflection board.

As you can see the approximate value, but it's a little hard to read correctly.

So a more accurate and easier way was devised.

It's measuring the natural vibration frequency.

The numerical model, called cantilever in mechanical engineering, is the structure of an arm with one side fixed to a fixed wall.

Is it similar to a deflection board?

In the figure, the suspended mass m falls by the displacement x.

Nowadays, CAD simulation can be used for numerical analysis.

It's mainly used when designing products.

The deflection board is a graph showing the bending stiffness EI as the displacement distance.

If you bounce the tip on this cantilever model, it will swing at its own frequency.

This natural frequency can be interpreted as a function of bending stiffness and length and weight.

Looking closely at the result of the equation, the bending stiffness is proportional to the square of the natural vibration frequency.

In other words, by measuring the vibration frequency instead of the deflection board, the bending stiffness can be known.

So in the 1960s, a CPM measuring instrument (Frequency Analazer) was developed.

This instrument measures the natural frequency and displays it in frequency by CPM.

The CPM measuring instrument, which measures the bending stiffness of shafts by frequency, has been used to date.

This is a light sensor type CPM measuring instrument.

This is a load cell CPM meter.

It is more precise and improved with compared to the light sensor type

I also made a CPM meter using a light sensor and an Arduino.

The program is simpler than the swing weight gauge.

I'll open how I made these two meters soon both schematic and program source.

And MOI gauge is still under development.

Shaft makers classify the bending stiffness of produced products.

They measure up to about 5 inches on the butt side, weigh a certain amount on the tip, and shake.

At this time, printing is divided into R, SR, and S grades according to the measured CPM.

If you look at it, the CPM comes out a little bit differently depending on the angle of the spine, and it shows the position.

I guess they print by applying a spine position.

Let's look at the frequency profile graph.

The horizontal axis is the shaft length and the vertical axis is the CPM.

Flex is divided according to length

In this graph, the green line represents 235 CPM as R at 45 inches.

Even with the same Flex, the shorter the length, the higher the CPM value.

I think this graph is from KBS company.

If you look at the upper part, 5.0 ~ 5.9 is classified as R.

If you look at the 5.5 line at 45 inches, it is about 236 CPM

It is generally known to measure stiffness by attaching 205g to the tip and fixing the butt side to 5 inches based on an uncut 45-inch shaft.

However, more detailed metrics and Flex classifications vary slightly from company to company.

So let's look at the process of assembling the club.

In general, the shaft is thinner at the tip and thicker at the butt.

The picture shows a parallel tip iron shaft from Dynamic Gold.

For each club, cut the tip and butt side according to the shaft maker's recommended specifications.

If you look at the weight of the iron head, the number 7 is 270g and the difference is sequentially 7g.

This is not standard, but it is almost the same.

The heads are cut and assembled in accordance with the shaft maker's recommended cutting charts for consistent weight and stiffness.

This is a graph comparing the CPM of iron and wedge sets by several makers.

Finely crafted clubs are consistent in weight and CPM.

The case of D seems to be very well organized, but the case of B is too big a difference.

It is this CPM matching that makes CPM consistent.

That is, even if the length is the same on the same bending stiffness shaft, the CPM will change if the head weight is different.

Naturally, even if the weight is the same, different lengths give different stiffness.

This is why you should not go to the fitting shop and cut the shaft.

This table shows a set of irons designed with the same CPM.

If you look at the blue swing weight, it's a lot different from what we usually know.

Iron 3 is E3.3 and sand wedge is C0..

I do not want to use this set of irons.

In general, CPM Matching (Frequency Matching) is the adjustment of a certain CPM difference between clubs.

Known golf club balancing matching methods are swing weight, moment of inertia and CPM.

This table shows the result of someone attempting all three balancing matches.

This is a very good result within the margin of error.

This is very difficult to do.

Most ready-made club makers produce only swing weight and CPM.

Only a company that makes it well.

Did you see that there are some manufacturers that just adjust swing weight and mess up CPM?

There is a way to make all three match results the same.

Just like in the Bryson Dissembo club, you'll have the same length and head weight.

The swing weight, MOI and CPM are then equal.

Your swing will be a bit weird like a Dissembo.

I mentioned swing weight and moment of inertia in the previous video as 1st moment and 2nd moment.

But here's an interesting fact.

Look at this video.

This is a swing weight meter on a tennis racket.

Isn't it a familiar sight somewhere?

That's right.

They measure the frequency by shaking a club when measuring swing weights in tennis, hockey and baseball.

In other words, the swing weight they are talking about is the second moment, our MOI.

In the previous video, “We are shaking the club dynamically.” I told you.

In fact, the first and second moments are not completely independent properties.

It is the same weight.

So if you match with swing weight, the MOI graph is tilted and if you match with MOI, SW is tilted.

Perhaps in the old days there was no technique to simply measure the moment of inertia

As an alternative, it seems to be trying to express the moment of inertia by measuring with a balance.

As long as you don't add weight to the grip side to adjust the swing weight,

As a result, it is not much different.

Theoretically, it is possible up to the 10% range.

I personally think we should now be reconsidered that relying on 14-inch scales, which we've used customarily for over 100 years.

We've looked at different ways to match your club assembly.

We don't need to know too deeply, but we should know what's important.

So far we've seen what CPM is and what CPM Club Matching is.

My nickname is Golfduckwho who a golf buff. Thank you.