Hi BCBF member,

Don't ask me why I am not doing my work on Friday afternoon and posting on this wonderful forum. Here is my answer. The weather is too nice outside and it is Friday. I don't want to work! Don't ask me why I am not on a court and samshin birds away. We don't have a court opn right now!

Anyway, back to the real business.

What do you guys think about shaft stiffness index? Here is what we have right now. Yonex and many manufactures use the rating "Flexable", "Mid Stiff", "Stiff" and "Extra Stiff" to rate shaft stiffness (not body part). However, these are relative term. when MP100 first came out, it was most stiff racquet at that time. Until AT800-o came out, the king of stiffness goes to AT800-o later the NS9000-x took the #1 spot. However, these are just relative stiffness rating between different model at that time. I would like to propose a new rating index system that is not base on relative to other racquet model. Here are my 2 proposals.
1) Get a fixed weight (ie 20lb). Attach weight to a in-elastic string (ie piano wire made out of steel). Attach the string to a hook. (the hook shoud be able to hook on to the throat of shaft). The total length from the end of weight to the top of the hook shoud be about 30cm (no reason, just need to have some length to hook it up) Mount the racquet on a surface that is at lease 40cm high on the handle. (by a C or wood clamp). Measure the distance from the ground to the shaft with racquet only. Then hook the weight on to the throat of racquet. Measure the distance again. With the change of height and length of the shaft, we can calc the angle of the shaft bend. Use the angle as the angle index (lower the number, stiffer the shaft) Repeeat the same process for all racquet.
2) Get a crank head. Mount an in-elastic string to the crank head. attach a weight scale to the other end of the string. Attach another string to the other end of the scale. The attach a string to a hook. Mount the racquet on a surface and secures the handle with a C or wood clamp. Hook the string on the throat. Slowly crank the crank head and stop when top of the throat has move for 1 cm. Take the force (tension) measure. Use that as force index. repeat the same process for all racquet.

Please post any idea or suggestion. Once we have some good idea, I will send some suggestions to Yonex to see if any stick.

Thanks and have a nice weekend.

PS, no blue pill joke.

The best person to talk to is Master NGP. He will tell right off the bat that certain Carlton models and the infamous CAB 22 ranke right up there as the stiffest pricks around :D.

The best person to talk to is Master NGP. He will tell right off the bat that certain Carlton models and the infamous CAB 22 ranke right up there as the stiffest pricks around :D.

Yeah, but those are his point of view. Beside he use middle finger as standard for the stiffness.!:D

Well, If you check the forum these kind of test has been tried..

I even tried that a few years ago.. But found the varying racket-lenght, shaft-lenghts, balances etc. affecting the results very much.. Also I have since then learned about dynamic stiffnes and static stiffness..and learned to treust my senses more :-)

So nowadays I really trust my senses more when testing than trying do-it-yourself measurements..

What really is needed is kind of the stiffness testing perofrmed for golf-shafts, where you get the shaft to osciallate and then measuers this..

Cheers,
Twobeer

P.S. Added from the wiki on measuirng golf-shafts stiffness:

"Shaft deflection is measured by clamping the butt end, then placing a weight on the tip. The deflection of the tip is then measured. Frequency of the shaft is measured by clamping it securely at the butt and then oscillating it. The number of oscillations is measured (in cycles per minute). The higher the number of oscillations for a given length, the stiffer the shaft. Both are measures of the relative stiffness only at the butt end of the shaft. Another method used to measure shaft stiffness is Energy Inertia (EI) Curves. This is a three-point bending test that measures the load along the entire length of the shaft. However, feel goes beyond these measurements which will be explained later."

D.S.

Good idea. I assume you need to attach some weight to the frame to make it easier to osciallate at higher mag?

I did porpose the method #1 before. It was just not using angle as index. I never had time and equipment to carry it out.

Good idea. I assume you need to attach some weight to the frame to make it easier to osciallate at higher mag?

I am not sure how the machines they use work exactly..

In Badminton It's even more komplicated as we also have a Stiffness issue with the head/frame.. Especially the torsion stiffness for off-center hits is interesting (theat Why Yonex have the T-joint, and other makers other solutions to acclomish this stifness..

The Mizuno Tetra-axial woven used in their high-end rackets are even more interesting :-) (Se my review of the TX700 and 500 :-) )

check out http://www.gws.hk/artman/publish/printer_25.php for example

/T

unfortunately, badminton shaft is not sold separately. I would be happy if someone wanna donate his inventory of rackets and allow me to cut off the racket frame head off for the oscillation test. Also, i would need a machine to count the oscillation as well:)

unfortunately, badminton shaft is not sold separately. I would be happy if someone wanna donate his inventory of rackets and allow me to cut off the racket frame head off for the oscillation test. Also, i would need a machine to count the oscillation as well:)

I know of one forum member with lots of broken frames, from off-center hits ;)

/Twobeer

Geezzzz, I wonder why he hasn't donated those rackets yet ;):p:D.

I know of one forum member with lots of broken frames, from off-center hits ;)

/Twobeer

Yeah, but those are his point of view. Beside he use middle finger as standard for the stiffness.!:D

Wrong! A panda tests stiffness or a racket shaft by hitting the racket and how hard the racket hits back. :p

I know of one forum member with lots of broken frames, from off-center hits ;)

/Twobeer


Naaaw, you need new rackets that have not been used. Used rackets, all the shafts are soft, flexy and wobbly. The test would not be valid, at least not for measuring new rackets.

You need aviation grade carbon-graphite composite :p.

Naaaw, you need new rackets that have not been used. Used rackets, all the shafts have been soft, flexy and wobbly. The test would not be valid, at least not for measuring new rackets.

that is why i did what i did in the stiffness test. Badminton shaft is not high quality as those use in high end golf clubs. No need to be so precise as in golf since badminton shaft is often pushed beyond its yield flex point, therefore making it softer over time. Also, badminton racket is a multifunctional stick, unlike each golf club which is use for one specific range of performance.

I can tell you now, based on a stiffness, it's the Cab 22* and then everybody else. :p

*I did try a Carlton racket that was stiffness as a board but didn't hit it enough to be able to give a valid comparison.

lots of factor determine flex. I think badminton racquets should incorporate the same flex determination methods as golf clubs. In golf, club flex is determined by, assuming all things equal:

Head weight - heavier the club head, the more flexible the club will feel
Shaft length - longer shaft feels more flexible
Shaft flex rating - whatever the indicated flex

There are other factors that determines flex, but badminton should at least begin to incorporate the above 3 important factors in flex determination.

I believe currently the market only use what silentheart suggested, eg. put a specified force on the shaft and see how much is bends. However, for example, an AT700 shaft may only bend as much as a typical x-stiff shaft, hence rated x-stiff. however, cuz AT700 is very head heavy (ie. heavy head), therefore the x-stiff doesn't feel like an x-stiff.

Also take into consideration the shaft length. The shorter the shaft, the more stiff it will be, all else being equal. This is another reason why the Cab22 is so stiff.

OK, I will scrap the idea...

the problem with measuring like this is that the stiffness of the racket can indeed be measured like that (placing the weight on the Tjoin, and clamping on the handle takes length, stiffness (and balancepoint) into account)
measuring like this is however a static problem. The basics of which lie in what is essentially a see-saw model (but then instead of turning, flexing)

But when you swing your racket, you have a dynamic problem. The difference is night and day, but since my colleges will start only in september, I'm hardly qualified to explain everything. (going for mechanical engineering)
I just have one great example of a dynamic problem that only occures when things move: the Chinook ground resonance test.
everythign stands still: nothing happens, blades move, everything resonates: devastation:
http://www.youtube.com/watch?v=-LFLV47VAbI

the problem with measuring like this is that the stiffness of the racket can indeed be measured like that (placing the weight on the Tjoin, and clamping on the handle takes length, stiffness (and balancepoint) into account)
measuring like this is however a static problem. The basics of which lie in what is essentially a see-saw model (but then instead of turning, flexing)

But when you swing your racket, you have a dynamic problem. The difference is night and day, but since my colleges will start only in september, I'm hardly qualified to explain everything. (going for mechanical engineering)
I just have one great example of a dynamic problem that only occures when things move: the Chinook ground resonance test.
everythign stands still: nothing happens, blades move, everything resonates: devastation:
http://www.youtube.com/watch?v=-LFLV47VAbI
Yeah, I rememberd that one. I agree with all you and other's point. Indeed I was thinking about using static measure to predict the dynamic situation. I thought it might be a good start. However, I agree that it will not be enough at this point.

Thank you for all of your inputs.

Yeah, I rememberd that one. I agree with all you and other's point. Indeed I was thinking about using static measure to predict the dynamic situation. I thought it might be a good start. However, I agree that it will not be enough at this point.

Thank you for all of your inputs.

Just go with the IPRS Test (Informal Panda Racket Stiffness) Test, it's free, easy to use and relatively accurate. :D

Just go with the IPRS Test (Informal Panda Racket Stiffness) Test, it's free, easy to use and relatively accurate. :D

have you register the IPRS??:D:D
ease to use; my guess, i have one(named X) of the rackets that are listed in IPRS. so, i check to IPRS, X = stiff. if i want a stiffer racket, i get something that is stiff+ or very stiff-. if i want a less stiff racket, i get those in the range of stiff- or moderate+.....
err... am i lost??:o

Maybe a sort-of stiffness wiki can eventually turn out a nice list?

Shaft stiffness index is like the displacement of an engine, with that alone, you have no idea how the car will perform.

You got my point?

it doesn't give the complete picture, but does that make it irrelavent?

it's just one part that gives a clue (no facts, nothing absolute, just a clue) on it's performance, juts like weight, gripsize, balance etc...

The IPRS test :eek:
lol lol lol :D

I like this 'Informal Panda Racket Stiffness' test :rolleyes:
It has an important sound to it :p

Wrong! A panda tests stiffness or a racket shaft by hitting the racket and how hard the racket hits back. :p

it doesn't give the complete picture, but does that make it irrelavent?

it's just one part that gives a clue (no facts, nothing absolute, just a clue) on it's performance, juts like weight, gripsize, balance etc...
To many people, shaft stiffness is more misleading than informative. When this factor is singled out, or discussed alone, it is just more likely so.

I have little doubt it won't confuse you. But do you agree with me many who talk about it do not realise what's going on?

I agree with you on that, certainly... Maybe the key is in context?

Now I see what you meant with the motor displacement comment , because I indeed have no clue what motor displacement is :p

I agree with you on that, certainly... Maybe the key is in context?

Now I see what you meant with the motor displacement comment , because I indeed have no clue what motor displacement is :p
I think it's quite a valid analogy. besides engine displacement, there is weight, there is aerodynamics, there is rev.... the list can go out of your monitor. When you see two guys only talk about the displacement of engines, you are pretty sure they know nuts about cars. that's exactly what's going on here. :D

At my club, the only comments you hear about stiffness is "nice" or "not nice"

It's only at BC were nutters try and get to the bottom of things...I rarely had a coach/salesman go fysics on me ;)

I guess I fit right in here :o:D

What about the Accuswing from Alphatennis(measuring swing weight) with the stiffness test of silentheart, is it possible to come up with a formula for stiffness?

A possible resolution to this heavy issue of figuring out a calculable Staff Stiffness Index could be found in the records maintained by the ancient Romans, circa 26 BC. :cool:

They had javelins, didn't they?
And the javelins had shafts, didn't they?
And they had a forum (called a Senate), didn't they? :rolleyes:
Perhaps they too discussed this vexing Shaft Stiffness Index. :D

I'd vote for Dinkalot's 'Informal Panda Racket Stiffness' test any day. :p

At my club, the only comments you hear about stiffness is "nice" or "not nice"

It's only at BC were nutters try and get to the bottom of things...I rarely had a coach/salesman go fysics on me ;)

I guess I fit right in here :o:D

Honestly, I don't understand why we need to get so complicated here. :mad:

I bet if you were to ask Rudy Hartono or Yang Yang or Lin Dan for their views on the Shaft Stiffness Index and how it impacted their careers, you'd very likely get, er, shafted. :p

Agree, it doesn't need to be too complicated. A super computer can spec out the "ideal" racket for me and if I play with it and don't like it, I don't like it.

Every professional player I have talked to, when I ask them about racket selection, they all say "feel" is the most important thing for them. If the racket feels good, they will use it. If it does not feel good, no matter how good on paper it is or how good others claim it to be, they won't use it.




Honestly, I don't understand why we need to get so complicated here. :mad:

I bet if you were to ask Rudy Hartono or Yang Yang or Lin Dan for their views on the Shaft Stiffness Index and how it impacted their careers, you'd very likely get, er, shafted. :p

The Informal Panda Stiffness Test is great and very accurate.
But its fun to have experiment going :D

Honestly, I don't understand why we need to get so complicated here. :mad:

I bet if you were to ask Rudy Hartono or Yang Yang or Lin Dan for their views on the Shaft Stiffness Index and how it impacted their careers, you'd very likely get, er, shafted. :p
I completly agree, adn when you ask most pro's a racket question you won't get any further than "this feels nice" "it's a good racket" etc etc

When you ask it me personally, you'd get the same:o

I'm just too much of baddict to not think about that crud...:o

I agree with jerby and Dink no doubt. Shaft stiffness is more a topic of science, than sports.

i can never understand when people talk about science unscientifically.

my point is, you are terribly wrong if you think you'll improve your badminton by knowing more about shaft stiffness. world champions are all nutters of badminton physics, i'm nutter of badminton the game.

so, the only reason i can see for the BCers to get this topic so deep and complicated is for the sake of curiosity in physics. physics in the real world.

It is a serious and fun topic to me. and i don't think BC is gonna forbid such a discussion. but the thing is, is this what you want and are you ready?

It is a serious and fun topic to me. and i don't think BC is gonna forbid such a discussion. but the thing is, is this what you want and are you ready?

Of course :-)

For some of us, it is not simply enough to know that a racket feels good.. Its very useful to know WHY it feels good :-)

Especially when looking for alternatives and better gear trying to get a rough estimate limits, properties of new rackets without having to try 1 zillion of them, based on knowledge & previous experiences :-)

Knowledge is never a hard burden to bear... :D

/Twobeer

Knowledge is never a hard burden to bear... :D


That's profound :eek:

Knowledge is never a hard burden to bear... :D

"Bear"? What about "bare"? I say, "panda"!!! :D:D:D

Of course :-)

For some of us, it is not simply enough to know that a racket feels good.. Its very useful to know WHY it feels good :-)

Especially when looking for alternatives and better gear trying to get a rough estimate limits, properties of new rackets without having to try 1 zillion of them, based on knowledge & previous experiences :-)

Knowledge is never a hard burden to bear... :D

/Twobeer
quite right. just that the answer why it feels good in your hand lies not only in the racket, but also in you! :D

one racket can feel right in Lin Dan's hand and wrong in Taufik's hand. It takes little effort to conclude that the 'why' is with difference between the players rather than the difference between the same racket.:p and we know pretty well how difficult if not impossible that is to study every difference between LD and Taufik! :mad:

it is pretty possibe to use the knowledge as his guide for racket choice, but only after he has tried so many rackets that he has enough data to summarise what weight, balance & shaft stiffness etc are 'right' to himself. and unfortunately, this empirical formula is not transferable to another person, the second guy has to collect his own data and establish his own formula.

I was just highlighting the difficulty of the analysis. I will enjoy the discussion with you folks never the less. you talk sense.

as this topic has come around many times, i'd put my thoughts in a reply some time ago, pls comment.

http://www.badmintoncentral.com/forums/showthread.php?t=43309

"Bear"? What about "bare"? I say, "panda"!!! :D:D:D

A 'bare bear' fetish :eek:
I'm worried for you Dinks :rolleyes:

Knowledge is never a hard burden to bear... :D

/Twobeer
the irony, it burns!!!

;)

If we keep going like this, we'll need a philosophy forum:p:D

A 'bare bear' fetish :eek:
I'm worried for you Dinks :rolleyes:

I worry for you, Sir; as I only have a "panda" fetish. :D

"Bear"? What about "bare"? I say, "panda"!!! :D:D:D

I really meant to write "beer" ;)

quite right. just that the answer why it feels good in your hand lies not only in the racket, but also in you! :D

one racket can feel right in Lin Dan's hand and wrong in Taufik's hand. It takes little effort to conclude that the 'why' is with difference between the players rather than the difference between the same racket.:p and we know pretty well how difficult if not impossible that is to study every difference between LD and Taufik! :mad:



hehe, Well I kinda look like it like weather predictions.. The more paramters you have the more accurate you can be :p

for example I can easilly conclude that a racket rated as flexy, 110g, bp 320mm, g5 grip, classic headshape and mx-tension 20lbs, would probably not be a racket worth spending 7 days play-time testing on for me :cool:

[QUOTE=franxon;646539
it is pretty possibe to use the knowledge as his guide for racket choice, but only after he has tried so many rackets that he has enough data to summarise what weight, balance & shaft stiffness etc are 'right' to himself. and unfortunately, this empirical formula is not transferable to another person, the second guy has to collect his own data and establish his own formula.[/QUOTE]

That's where the science comes in.. gettting the metrics and measuerments right, so each individual will be able to draw conslusion based on his individual preferences :)

/T