the flaw with RDC flex measurement --> grips

[wallymann]

i've been doing my own DIY flex measurement in my shop and it occurs to me that there's a significant flaw in how racquets are mounted for flex measurement in an RDC.

the problem is that the fixing clamp at the butt applies pressure to the installed grip. a grip is a hugely inconsistent/variable factor that has materially significant impact on the flex measurement.

the measured flex varies in fractions of a mm...and i've found that the compression at the grip can vary greatly based on the material (leather, synthetic) and thickness and add the overgrip material/thickness/layers...multiplied by the variable force applied to the RDC fixing clamp...its a recipe for meaningless RDC numbers.

in my testing the only way to remove this inconsistent/variable factor is to clamp a racquet sans grip...i.e., the bare hairpin. once i did that the measured flex was much more consistent and repeatable from test-to-test for a given racquet.

 

[Crocodile]

How much did the flex numbers with your testing with the hairpins differ to the manufacturer’s or TW figures.
Were there big differences and were there any rogue readings where a flexible frame came out much stiffer.

 

[badmice2]

i've been doing my own DIY flex measurement in my shop and it occurs to me that there's a significant flaw in how racquets are mounted for flex measurement in an RDC.

the problem is that the fixing clamp at the butt applies pressure to the installed grip. a grip is a hugely inconsistent/variable factor that has materially significant impact on the flex measurement.

the measured flex varies in fractions of a mm...and i've found that the compression at the grip can vary greatly based on the material (leather, synthetic) and thickness and add the overgrip material/thickness/layers...multiplied by the variable force applied to the RDC fixing clamp...its a recipe for meaningless RDC numbers.

in my testing the only way to remove this inconsistent/variable factor is to clamp a racquet sans grip...i.e., the bare hairpin. once i did that the measured flex was much more consistent and repeatable from test-to-test for a given racquet.

Assuming string pattern plays into a factor (most rackets are measured strung), I’m curious to whether strings and string pattern will play a huge role with the measurement. Do you have any read out on that?

 

[fritzhimself]

Maybe that will help you.
I've been clamping the frames like this for a good 20 years.
I get good results and don't damage the handle or butt cap at all.
Btw - the unstrung frame is between 1-3 points harder.
It always depends on the frame itself and possibly the stringing stiffness and string.

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ibb.co

 

[fritzhimself]

I have replaced the grip handles on an older Head Prestige. I took the measurements on my RDC.
Yes, it is true that the flex is influenced by the grip tape. Is that bad? I would say no.
Which flex does the user feel - the flex measured on the hairpin or the flex with grip tape and overgrip?
In my case it was 1 point harder on the hairpin. So everything is fine.

 

[fritzhimself]

I uploaded a video of the measurements .....

 

[wallymann]

Which flex does the user feel - the flex measured on the hairpin or the flex with grip tape and overgrip?

the issue isnt what the player feels...its making meaningful comparisons.

with grip compressibility an uncontrolled/unpredictable variable, how can meaningful and consistent comparisons be made?

if the difference is 1 point, as your testing shows, maybe the magnitude isnt substantial enough to matter in the end.

like all aspects of racquet construction like weight, balance, swingweight...there's alot of variability already...just add stiffness to the list!

 

[fritzhimself]

Well - I have now measured exactly the same stiffness on a 58 RA frame on the hairpin and with the basic grip tape.
I regularly get several rackets of the same model for fitting or tuning, so the RA is also up to 2 points different (if you're unlucky).
So I see it as a small evil to compare rackets of different brands.
Why does everyone want to measure the world exactly when there are so many different sunsets?

 

[HitMoreBHs]

I uploaded a video of the measurements .....

Rahmen 69? That’s no noodle.

 

[fritzhimself]

The frame has 65 RA when tensioned - works like a charm.

 

[wallymann]

Why does everyone want to measure the world exactly when there are so many different sunsets?

for me, i've aligned my gamer sticks to equalize static, sw, balance specs...this is the final step in equipment consistency, just to see what's possible when starting with a pair of racquets that are ostensibly "the same" --> an academic exercise!

 

[WYK]

i've been doing my own DIY flex measurement in my shop and it occurs to me that there's a significant flaw in how racquets are mounted for flex measurement in an RDC.

the problem is that the fixing clamp at the butt applies pressure to the installed grip. a grip is a hugely inconsistent/variable factor that has materially significant impact on the flex measurement.

the measured flex varies in fractions of a mm...and i've found that the compression at the grip can vary greatly based on the material (leather, synthetic) and thickness and add the overgrip material/thickness/layers...multiplied by the variable force applied to the RDC fixing clamp...its a recipe for meaningless RDC numbers.

in my testing the only way to remove this inconsistent/variable factor is to clamp a racquet sans grip...i.e., the bare hairpin. once i did that the measured flex was much more consistent and repeatable from test-to-test for a given racquet.

Usually when you RDC a racquet, you take several readings from several units(oftentimes 2-3 readings of the same stick as well), and companies usually average all the results.
The numbers, like nearly every other measurement in sports, are a guideline.
If you wish to see how your particular grip affects the RDC, then you go and do what you are doing.
For the vast majority of people, a racquet's RDC simply guides their decisions, and is not the end all.

 

[dr325i]

Maybe that will help you.
I've been clamping the frames like this for a good 20 years.
I get good results and don't damage the handle or butt cap at all.
Btw - the unstrung frame is between 1-3 points harder.
It always depends on the frame itself and possibly the stringing stiffness and string.

20240107-100954 hosted at ImgBB

Image 20240107-100954 hosted on ImgBB

ibb.co

This is correct.
Bare hairpins have the highest flex, then unstrung palleted and gripped frames, then strung frames.
Each step reduces measured flex numbers by 1-3 points RA

 

[yonexRx32]

It always depends on the frame itself and possibly the stringing stiffness and string.

20240107-100954 hosted at ImgBB

Image 20240107-100954 hosted on ImgBB

ibb.co

Nope . Does not depend on strings. It depends on the tension of the strings and their number.

 

[yonexRx32]

This is correct.
Bare hairpins have the highest flex, then unstrung palleted and gripped frames, then strung frames.
Each step reduces measured flex numbers by 1-3 points RA

No.. The highest flex (ibility) (lowest RA number) is the strung racquet. The highest RA number is the unstrung frame. The grip and pallet have nothing to do with frame bending in the hoop, where measurement is taken. If you see it does, you're doing something wrong . Frtzhimself is on right track.If he clamped with two metal plates the length of the grip minus the butt flare, the force would be spread on a large enough area that the give of the grip and pallet would be negligible.

 

[dr325i]

No.. The highest flex (ibility) (lowest RA number) is the strung racquet. The highest RA number is the unstrung frame. The grip and pallet have nothing to do with frame bending in the hoop, where measurement is taken. If you see it does, you're doing something wrong . Frtzhimself is on right track.If he clamped with two metal plates the length of the grip minus the butt flare, the force would be spread on a large enough area that the give of the grip and pallet would be negligible.

Again, if the bare hairpin is 66RA, unstrung racket with pallets, grommets and grip will measure ~64RA and strung frame ~62RA.

And yes, grommets do affect the flex

 

[tim-ay]

for me, i've aligned my gamer sticks to equalize static, sw, balance specs...this is the final step in equipment consistency, just to see what's possible when starting with a pair of racquets that are ostensibly "the same" --> an academic exercise!

Twist weight is way more meaningful than RA when matching rackets. By a factor of 10 or 50. RA is def not “the final step”

 

[PistolPete23]

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