Don't blame the rubber if you don't get enough spin.

[lodro]

Well actually there have been some people high on coke that could elaborate funny concepts about noise bombs

noise bombs are a reality. Now iffen you would send both , James Z and BB out basking with a
Shakuhachi flute , all people within about 50m would instantly disappear. Another good instrument which has the same effect on many people is a bagpipe .
My personal favorite is a Sopranino Sax, When the highest notes are blown, blood streams out of my eyes ears and nose

 

[Egon]

Cool idea! We take a board with sandpaper to increase friction, and wave it once, but strongly, like a baseball bat - we get a cosmic rotation that no one in the world can handle!

 

[lodro]

Cool idea! We take a board with sandpaper to increase friction, and wave it once, but strongly, like a baseball bat - we get a cosmic rotation that no one in the world can handle!

I like the idea but I could handle it, I constantly rotate around my own axis 😇

 

[blahness]

"Linear speed of the racket = rotational frequency of the ball" has been a problematic assumption that somehow gets repeated without reservation as it ignores the effects due to moment of inertia (swingweight), which affects the kinetic/elastic (potential) energy, among others.

Experimental data collected from 6 Japanese women elite players, 5 righties and 1 lefty (one of them likely Ito from the silhouette), show that:
A power drive with an impact speed of 17.2±1.6 m/s results in ball spin of 181.4±55.2 rps;
A knuckle shot [no spin ball?] with an impact speed of 13.9±1.4 m/s results in ball spin of 104.6±39.9 rps.
Source: https://kaken.nii.ac.jp/ja/file/KAKENHI-PROJECT-16K01666/16K01666seika.pdf

That seems extremely high - I saw Fang Bo hit max measured spin rates of only 130+rps on a FH loopkill - I highly doubt Ito or any Japanese woman can get up to 180+rps while actually landing the shot on the table. Maybe the measurement methodology is not the same....

 

[blahness]

No i didn't.


NO I I DIDN'T! There must be friction to create spin.


I made it clear I assumed there was NO spring effect.


Are you talking about speed or energy. If you are talking about energy then you are probably close when talking about a flat hit. In that case 40% would be left. This equates to a normal COR of 0.63 or the rebound is 63% of the impact speed.


Read more closely. I said 30 m/s which is about 70 MPH. Then I said reduce that to reflect your skill level.


I said base ball pitchers can throw balls at 90 MPH or about 40 m/s and still have control. I assumed good TT players could manage 30 m/s
Just because you swing at 30 m/s doesn't mean the is flat hit at 30 m/s. As you start hitting the ball off center the more and more energy goes into spin and less into speed. If you flat hit, you better have a line of sight shot.

There is an optimal spin to speed ratio for each shot. I sometimes need to loop the ball from below the table. in this case more of the energy must go into spin because hitting the ball upwards too fast will cause the ball to go off the end of the table before it drops enough due to the Magnus effect.

Just saying - there are a LOT more variables than what your simplistic model has, and those variables affect the real world physics significantly. Furthermore, this is not a simple elastic collision, otherwise you would be able to generate the same spin with a wooden bat than the latest Dignics rubbers.

 

[allfj]

this is true to an extent, because if you are using a target racket with dead rubbers then it is your rubbers fault, but if you are using a very controlled rubber like mark V with a 5ply wooden blade then it is your technique.

 

[brokenball]

Just saying - there are a LOT more variables than what your simplistic model has, and those variables affect the real world physics significantly.

Like what? The temperature of the rubber affects how springy it is? You forgot the pull of the moon.
That is always the excuse. Even so called engineers make the same excuse. So what part of the formula for converting angular velocity to angular rotation is not accurate? ANSWER THIS?

Furthermore, this is not a simple elastic collision, otherwise you would be able to generate the same spin with a wooden bat than the latest Dignics rubbers.

Can't you read? I said there is no spring effect. That means I assume the rubber is in-elastic yet can create lots of spin with the right stroke. An elastic collision would generate more spin.

I can model real systems in real applications that make real money. I am usually get very close, within 5% or and often within 2%. Even NASA and ESA make mid course corrections during their space lights because their original models were not perfect. It is good enough to be close and not need to correct that much.

So far Zeio hasn't explained where the extra 5 m/s comes from.

The formula for converting angular velocity to angular rotation isn't that difficult.
The formula I am using is 10.4.23

10.4: Relating Angular and Translational Quantities

The linear kinematic equation have the rotational counterparts in which x = θ, v = ω, a = α. A system undergoing uniform circular motion has a constant angular velocity, but …

phys.libretexts.org

It is amazing how so many want to remain ignorant.

 

[lodro]

The formula for converting angular velocity to angular rotation isn't that difficult.
The formula I am using is 10.4.23

10.4: Relating Angular and Translational Quantities

The linear kinematic equation have the rotational counterparts in which x = θ, v = ω, a = α. A system undergoing uniform circular motion has a constant angular velocity, but …

phys.libretexts.org

It is amazing how so many want to remain ignorant.

of course it is not that difficult and we have tried to gently hint that the multiverse is very complex, I mean not just TT - math .
Now I really have to wonder if it is a bit of a wank or even the old "mine is bigger than yours game."
I mean really, where is the fun ?

 

[Gozo Zyreruna]

BB should be censured for cultural appropriation. He is imitating Asians' stereotype of being good at maths, according to Ronny Chieng, the Asian Cultural Expert 😉

and

also according to Jimmy O Yang

p/s Back off BB, being good in maths is an Asian thing. Stop this cultural appropriation.

 

[lodro]

BB should be censured for cultural appropriation. He is imitating Asians' stereotype of being good at maths, according to Ronny Chieng, the Asian Cultural Expert 😉

and

also according to Jimmy O Yang

p/s Back off BB, being good in maths is an Asian thing. Stop this cultural appropriation.

Brilliant, I love it and it also means that all those who choose the stay ignorant
are the majority and so that is "the norm" ,
bottom line : "We win" 😁

 

[blahness]

Like what? The temperature of the rubber affects how springy it is? You forgot the pull of the moon.
That is always the excuse. Even so called engineers make the same excuse. So what part of the formula for converting angular velocity to angular rotation is not accurate? ANSWER THIS?


Can't you read? I said there is no spring effect. That means I assume the rubber is in-elastic yet can create lots of spin with the right stroke. An elastic collision would generate more spin.

I can model real systems in real applications that make real money. I am usually get very close, within 5% or and often within 2%. Even NASA and ESA make mid course corrections during their space lights because their original models were not perfect. It is good enough to be close and not need to correct that much.

So far Zeio hasn't explained where the extra 5 m/s comes from.

The formula for converting angular velocity to angular rotation isn't that difficult.
The formula I am using is 10.4.23

10.4: Relating Angular and Translational Quantities

The linear kinematic equation have the rotational counterparts in which x = θ, v = ω, a = α. A system undergoing uniform circular motion has a constant angular velocity, but …

phys.libretexts.org

It is amazing how so many want to remain ignorant.

I'm questioning this particular model you did because the assumptions are not correct. How efficiently the blade velocity transfers to ball spin/speed is of importance here. And I bet if you actually hit a ball eccentrically with a wooden paddle with no rubber, you won't be getting anywhere near the speeds/spins you predicted here. Why is that?

Any predictive model needs to be tested against reality to prove its mettle before it can be used for analysis. As an engineer you should be well aware of this. You have to provide at least some backtests to validate your model since it's so simple.

 

[Egon]

You know, Broken Ball, by your statements that you know a lot, and everyone else knows nothing, you remind me of a person whose area of knowledge is a point whose surface practically does not come into contact with the unknown surrounding it, therefore this person believes that he He knows a lot. On the contrary, a person whose area of knowledge is vast will never say that he knows a lot, because he comes into contact with much larger areas of the unknown and by increasing knowledge, he increases the unknown for himself. Think about it

 

[brokenball]

You know, Broken Ball, by your statements that you know a lot

yes

and everyone else knows nothing,

I have not said that that. Nothing is an extreme but it is obvious there aren't any engineers or physicist here on this forum. You question a simple equation I posted a link to. What am I supposed to think?

you remind me of a person whose area of knowledge is a point whose surface practically does not come into contact with the unknown surrounding it, therefore this person believes that he He knows a lot.

WTFRU to say something like that? You have no clue.
I am putting you, blahness and James Z in the category of those that make statements without any proof. USDC should do something about that.

On the contrary, a person whose area of knowledge is vast will never say that he knows a lot, because he comes into contact with much larger areas of the unknown and by increasing knowledge, he increases the unknown for himself. Think about it

Again, you know nothing. USDC knows I am the real deal. I have shown him videos. Now why are you so offended? Is it because you can't get any spin?

I'm questioning this particular model you did because the assumptions are not correct.

Exactly what is incorrect and more importantly, how would that affect the results?

How efficiently the blade velocity transfers to ball spin/speed is of importance here.

Can't you read? I have said over and over again I am assuming there is no spring effect when it comes to spin. This way the the tangential velocity of the paddle is the same as the angular velocity of the ball and that can be divided by 2*PI*radius to get the revolutions per second. If there is some spring effect then the spin will be higher but then there really is no excuse for not getting the desired spin. Is that clear?

 

[blahness]

Can't you read? I have said over and over again I am assuming there is no spring effect when it comes to spin. This way the the tangential velocity of the paddle is the same as the angular velocity of the ball and that can be divided by 2*PI*radius to get the revolutions per second. If there is some spring effect then the spin will be higher but then there really is no excuse for not getting the desired spin. Is that clear?

Your model is wrong because of this particular assumption. It simply isn't how the racket - ball system interacts. Otherwise you could easily spin a ball with any surface you want (notice that your model can't account for the differences in racket surfaces?), but everyone knows that's not the case.

 

[Attitude]

Just to be a part of this nonsense, i feel the need to mention that i usually blame my blade if it doesnt produce "enough" spin, so it is not my fault.

Where is your god now?

 

[TareqPhoto]

It is not just about "Spin", but even "Speed", i know a person or player, he has really fast blade and fast rubber, or let's say good enough rubber such as Tenergy 05 or Dignics, and yet he still keep saying "I want more speed, i want faster, this Tenergy 05 is slow for me", so if you have the fastest blade and fastest rubber and you still want more, WHY? HOW? In fact i have Long 5 X blade with H3 Prov blue sponge boosted, and many tried it and they all said "Very fast, can't control, not suit for me", oh really, then what suits you!!!

Kind of when they lack something then they scream for more, and when they get it they complain again for something else, it is kind of they never blame themselves and putting it on their equipment.

 

[Gozo Zyreruna]

It is not just about "Spin", but even "Speed", i know a person or player, he has really fast blade and fast rubber, or let's say good enough rubber such as Tenergy 05 or Dignics, and yet he still keep saying "I want more speed, i want faster, this Tenergy 05 is slow for me", so if you have the fastest blade and fastest rubber and you still want more, WHY? HOW? In fact i have Long 5 X blade with H3 Prov blue sponge boosted, and many tried it and they all said "Very fast, can't control, not suit for me", oh really, then what suits you!!!

Kind of when they lack something then they scream for more, and when they get it they complain again for something else, it is kind of they never blame themselves and putting it on their equipment.

I want speed, faster and faster and faster... then I found Donic Bluestorm Z1. I am now a happy lil'camper...

 

[brokenball]

Your model is wrong because of this particular assumption. It simply isn't how the racket - ball system interacts. Otherwise you could easily spin a ball with any surface you want (notice that your model can't account for the differences in racket surfaces?), but everyone knows that's not the case.

What is wrong with my assumption? Can you explain how you would correct it? I bet not. The math is pretty simple if I assume there is no spring effect and the impact is in-elastic. I posted a link but that simple formulas seems to confused you. So lets assume the impact isn't in-elastic. Can you derive the speed and spin after impact formulas? Do you even know what they are? Now you are really lost.

How can you criticize what you don't understand?

Does it really change anything? The point is that one should be able to generate enough spin even with a dead rubber. One should be able to generate more than enough spin with rubber that that has some tangential elasticity. If you can generate spin with these new rubbers, and just about any of them, it is your problem not the equipment.

I am still waiting for Zeio to explain how power stroke, hitting through the ball, can generate the claimed spin. There is a way, but not very likely. let's see if Zeio can explain it.

 

[turbozed]

What is wrong with my assumption? Can you explain how you would correct it? I bet not. The math is pretty simple if I assume there is no spring effect and the impact is in-elastic. I posted a link but that simple formulas seems to confused you. So lets assume the impact isn't in-elastic. Can you derive the speed and spin after impact formulas? Do you even know what they are? Now you are really lost.

How can you criticize what you don't understand?

Does it really change anything? The point is that one should be able to generate enough spin even with a dead rubber. One should be able to generate more than enough spin with rubber that that has some tangential elasticity. If you can generate spin with these new rubbers, and just about any of them, it is your problem not the equipment.

I am still waiting for Zeio to explain how power stroke, hitting through the ball, can generate the claimed spin. There is a way, but not very likely. let's see if Zeio can explain it.

I don't understand this at all and I'm trying to follow along with the conversation. I do have a few questions:

Does the formula you describe apply for any material the ball impacts with?

If the answer is yes, then does the rubber only provide spring effect from elasticity? How would that be represented?

Does the formula account for any changes in ball trajectory or course from the ball sinking into the topsheet/sponge material?

I've seen slow motion videos of the ball impacting tacky rubber, and visibly climbing up the rubber before bouncing off the surface. Is this phenomenon accounted for in the formula, or is there a separate formula involved there?

I just find this sort of thing very fascinating, and your confidence is giving me the impression like you can answer these questions I've always wondered about. Thank you in advance!

 

[NextLevel]

What is wrong with my assumption? Can you explain how you would correct it? I bet not. The math is pretty simple if I assume there is no spring effect and the impact is in-elastic. I posted a link but that simple formulas seems to confused you. So lets assume the impact isn't in-elastic. Can you derive the speed and spin after impact formulas? Do you even know what they are? Now you are really lost.

How can you criticize what you don't understand?

Does it really change anything? The point is that one should be able to generate enough spin even with a dead rubber. One should be able to generate more than enough spin with rubber that that has some tangential elasticity. If you can generate spin with these new rubbers, and just about any of them, it is your problem not the equipment.

I am still waiting for Zeio to explain how power stroke, hitting through the ball, can generate the claimed spin. There is a way, but not very likely. let's see if Zeio can explain it.

He has already explained what is wrong with your assumption - if it were true, then the rubber used, whether dead or not, would have no impact on the observed differences in spin production when one changes rubber. And this is clearly not what we see in the real world. No, one cannot produce enough spin with a dead rubber. You should be able to explain that. There are differences in surface grip and sponge elasticity that affect spin production.

You probably meant to write "If you can't generate spin with these new rubbers..." . If you can't be precise with your language, then why are you being so annoying quibbling about things you are divorcing from what happens in the real world? How many top players use dead rubbers? Is it because they are idiots who don't know how to get spin?

You don't even know how to play decent forehand topspin. Is that why you get kicks off insulting people online?