San Francisco looking for training partner.

[dingyibvs]

If the ball doesn't dip as much after the bounce, assuming the trajectory is the same prior to the bounce, then yes, it would mean less topspin.

 

[UpSideDownCarl]

I could be wrong. If BrokenBall answers, we may have the physics behind it, or any other physics/engineering types.

I believe that what the higher kick means is actually less speed which would cause the ball to drop faster from the spin (magnus effect + gravity) and kick higher because of that faster drop and there being less forward momentum from the pace of the ball. The spin would still kick the ball forward, but the slower speed with the higher kick would indicate the faster drop which can only happen when the spin is fast enough to have a bigger impact than the forward momentum from the speed of the ball.

Said differently a ball that is slower, with the same amount of spin will drop sooner and faster than a faster ball with the same rpm of spin. Same thing with sidespin. If you had a ball that had a lot of sidespin, if it was moving slower, it would curve sooner and more, and if it was faster it would curve later and less. Later because the effect of the spin (on the air the ball is passing through) needs to overcome (outweigh) the effect of the forward momentum on the ball.

Magnus effect plus gravity on a ball that has a lot of spin but is not going so fast will cause it to drop faster and bounce higher even though it will still kick forward.

Again, someone who really knows this subject may give a better answer and I could be wrong. But I think that is the basics of the subject.

 

[God-scrubplayer]

I could be wrong. If BrokenBall answers, we may have the physics behind it, or any other physics/engineering types.

I believe that what the higher kick means is actually less speed which would cause the ball to drop faster from the spin (magnus effect + gravity) and kick higher because of that faster drop and there being less forward momentum from the pace of the ball. The spin would still kick the ball forward, but the slower speed with the higher kick would indicate the faster drop which can only happen when the spin is fast enough to have a bigger impact than the forward momentum from the speed of the ball.

Said differently a ball that is slower, with the same amount of spin will drop sooner and faster than a faster ball with the same rpm of spin. Same thing with sidespin. If you had a ball that had a lot of sidespin, if it was moving slower, it would curve sooner and more, and if it was faster it would curve later and less. Later because the effect of the spin (on the air the ball is passing through) needs to overcome (outweigh) the effect of the forward momentum on the ball.

Magnus effect plus gravity on a ball that has a lot of spin but is not going so fast will cause it to drop faster and bounce higher even though it will still kick forward.

Again, someone who really knows this subject may give a better answer and I could be wrong. But I think that is the basics of the subject.

So from what you saying, it could be the spin is the same but the speed of the ball is high because of d09c. However, something doens't make sense, because , t05 is faster compare to d09c so why would d09c have more speed?

 

[brokenball]

For people who used and play against dignics 09c we notice the second bounce have a weird arc compare to other conventional rubbers like h3 and t05. It bounces "up". Can anyone explain in science what's actually happening? why does it bounce "up"? is it less spin or more spin? If my science is right, bouncing up means it's less spin.

I am confused. What do you mean? The seconds bounce after a serve?
After the ball leaves the paddle, it doesn't care what hit it. Two balls with the same trajectory and spin will do the same thing.

 

[dingyibvs]

I could be wrong. If BrokenBall answers, we may have the physics behind it, or any other physics/engineering types.

I believe that what the higher kick means is actually less speed which would cause the ball to drop faster from the spin (magnus effect + gravity) and kick higher because of that faster drop and there being less forward momentum from the pace of the ball. The spin would still kick the ball forward, but the slower speed with the higher kick would indicate the faster drop which can only happen when the spin is fast enough to have a bigger impact than the forward momentum from the speed of the ball.

Said differently a ball that is slower, with the same amount of spin will drop sooner and faster than a faster ball with the same rpm of spin. Same thing with sidespin. If you had a ball that had a lot of sidespin, if it was moving slower, it would curve sooner and more, and if it was faster it would curve later and less. Later because the effect of the spin (on the air the ball is passing through) needs to overcome (outweigh) the effect of the forward momentum on the ball.

Magnus effect plus gravity on a ball that has a lot of spin but is not going so fast will cause it to drop faster and bounce higher even though it will still kick forward.

Again, someone who really knows this subject may give a better answer and I could be wrong. But I think that is the basics of the subject.

No, the Magnus force increases with both speed and spin.

https://blogs.solidworks.com/tech/2019/12/the-magnus-effect-the-rotation-of-various-spheres.html

 

[UpSideDownCarl]

No, the Magnus force increases with both speed and spin.

https://blogs.solidworks.com/tech/2019/12/the-magnus-effect-the-rotation-of-various-spheres.html

So, are you saying that two shots with them same amount of spin but one is slower and one is faster, and the spin is topspin, the faster one will drop sooner and gravity will take effect sooner in the arc of the ball? Are you sure about that. (BTW: this is the reverse of what I was trying to say above).

Remember, in a topspin shot, the topspin is trying to bring the ball down and the force of gravity is as well.

 

[UpSideDownCarl]

I am confused. What do you mean? The seconds bounce after a serve?
After the ball leaves the paddle, it doesn't care what hit it. Two balls with the same trajectory and spin will do the same thing.

I think he is trying to figure out if D09c is faster, creates more spin, is slower, makes less spin.....and why, with one rubber, he gets a bounce that is higher and with another rubber, he gets a bounce that is lower. So he is trying to figure out if D09c is getting more or less spin than the other rubber, and if it is faster or slower than the other rubber.

My guess is, same or more spin, but slower would cause the bounce he is referring to to be a little higher.

 

[brokenball]

Dingyibvs is correct in that the Magnus force is proportional to the speed time spin assuming the spin axis is perpendicular to the trajectory of the ball.
What is NOT defined above is the term "SOONER". "Sooner" in terms of time or soon in terms of distance? Think about this!

I still want to know about the second bounce.

 

[James Z]

Dingyibvs is correct in that the Magnus force is proportional to the speed time spin assuming the spin axis is perpendicular to the trajectory of the ball.
What is NOT defined above is the term "SOONER". "Sooner" in terms of time or soon in terms of distance? Think about this!

I still want to know about the second bounce.

speed time spin > Whatever the hell does that mean ? This may be because you are calculating the standard deviation & variance to an inverse polynoimal of a Poisson distribution of regression which may not work for multivariate random variables ?

The more I read yoru posts , tehmore convinced i am that you pull some random fancy phrases out of the internet that makes no sense to the topic under discussion because your standard deviation & variance is way off🤣🙄😏

 

[UpSideDownCarl]

Dingyibvs is correct in that the Magnus force is proportional to the speed time spin assuming the spin axis is perpendicular to the trajectory of the ball.
What is NOT defined above is the term "SOONER". "Sooner" in terms of time or soon in terms of distance? Think about this!

I still want to know about the second bounce.

Yeah. I guess I am thinking of the distance the ball has traveled. Not amount of time.

 

[dingyibvs]

So, are you saying that two shots with them same amount of spin but one is slower and one is faster, and the spin is topspin, the faster one will drop sooner and gravity will take effect sooner in the arc of the ball? Are you sure about that. (BTW: this is the reverse of what I was trying to say above).

Remember, in a topspin shot, the topspin is trying to bring the ball down and the force of gravity is as well.

If they have the same launch angle, yes, the faster ball will hit the table sooner.

Whether the second bounce will be lower is much more complicated. If two shots have the same incidence angle as it hits the table, then the faster, spinnier one should kick more and bounce lower. However, there's no reasonable way for us to measure the incidence angle without some expensive equipment, and the the angle will change based on how you hit the ball and which rubber you hit it with.

What all this amounts to is basically I don't think you can say the D09C is spinner just by seeing how high it bounces. I think the most reliable realistic way to judge a rubber's looping ability is still the most unscientific one--how reliable are your loops landing, and how "heavy" does your opponent's loop feel when you block him as he uses that rubber vs the comparison? Consistency x power (speed + spin) = wins, after all, if everything else is the same.

 

[dingyibvs]

speed time spin > Whatever the hell does that mean ? This may be because you are calculating the standard deviation & variance to an inverse polynoimal of a Poisson distribution of regression which may not work for multivariate random variables ?

The more I read yoru posts , tehmore convinced i am that you pull some random fancy phrases out of the internet that makes no sense to the topic under discussion because your standard deviation & variance is way off🤣🙄😏

I think he meant speed time spin. It's just a typo. This means that the magnus force is positively and linearly correlated with both speed and spin.

 

[UpSideDownCarl]

If they have the same launch angle, yes, the faster ball will hit the table sooner.

Whether the second bounce will be lower is much more complicated. If two shots have the same incidence angle as it hits the table, then the faster, spinnier one should kick more and bounce lower. However, there's no reasonable way for us to measure the incidence angle without some expensive equipment, and the the angle will change based on how you hit the ball and which rubber you hit it with.

What all this amounts to is basically I don't think you can say the D09C is spinner just by seeing how high it bounces. I think the most reliable realistic way to judge a rubber's looping ability is still the most unscientific one--how reliable are your loops landing, and how "heavy" does your opponent's loop feel when you block him as he uses that rubber vs the comparison? Consistency x power (speed + spin) = wins, after all, if everything else is the same.

But he is talking about a serve, and the second bounce. And I don't know if D09c helps you generate more spin. But, if it generates about the same spin and is slower, would this cause the second bounce of a serve to bounce a little higher? Or is there another reason why the second bounce on a serve would bounce higher?

 

[dingyibvs]

But he is talking about a serve, and the second bounce. And I don't know if D09c helps you generate more spin. But, if it generates about the same spin and is slower, would this cause the second bounce of a serve to bounce a little higher? Or is there another reason why the second bounce on a serve would bounce higher?

After others e.g. broken ball asked him to clarify, I realized that I actually don't really understand his question either. I had assumed he meant a topspin, but he didn't actually say that. He didn't even clarify if he meant a serve or not. He would need to clarify his question before it can even begin to be answered.

With that said, if he's talking about the 2nd bounce after a service, then there are probably too many factors at play for me to truly answer it. Now, it should be noted that backspins would pop higher with higher speed and spin, the opposite of topspins.

 

[brokenball]

speed time spin > Whatever the hell does that mean ? This may be because you are calculating the standard deviation & variance to an inverse polynoimal of a Poisson distribution of regression which may not work for multivariate random variables ?

It should be speed times spin or speed*spin.
You misspelled polynomial. A spelling check should have caught that. Do you know that TTD has a spelling checker?

The more I read yoru posts , tehmore convinced i am that you pull some random fancy phrases out of the internet that makes no sense to the topic under discussion because your standard deviation & variance is way off🤣🙄😏

More misspelled words. This is definitely unforgivable. I think we should ban him for not using the forum's spell checker.

USDC knows I am the real deal.

I am still waiting for the OP's definition of second bounce.

USDC is assuming that "sooner" means before that ball goes off the end of the table. If the ball hits the second time during a serve then the ball didn't go off the end of the table. That is why I am confused.

Now if talking about after the serve then we have a different situation. The Magnus effect increases with speed but the ball is also traveling faster and may go off the end of the table before the ball drops enough. maybe James Z can enlighten us. I don't know how many balls I have "looped" that seem to break just after going off the end of the table. Obviously I didn't loop them well enough. This is an important topic but I am not sure it applies to the OP's second bounce question.

 

[IB66]

Kicker serve, sometimes these bounce up slightly more, or appear to, or is it that the ball shoots forward faster than expected. Players get caught out by the 2nd bounce.

 

[brokenball]

Kicker serve, sometimes these bounce up slightly more, or appear to, or is it that the ball shoots forward faster than expected. Players get caught out by the 2nd bounce.

Shooting out forward and low I can understand. However, the ball must have a lot of top spin so that 2*PI*rev/sec>velocity.
This won't work well unless the table top has some friction for the ball to push off from. The Magnus effect should make the ball shoot out low too.

The fastest serve video by the Japanese player, Sakai, is a super kicker serve. There is a lot of top spin and Magnus effect on those balls. I was provided high speed video of that serve. I counted frames to get the timing and calculate/estimate the speed and spin.

Bouncing high is suspect because normally back spin balls don't have a lot of back spin AND speed for the Magnus effect to be noticeable. A no spin ball will bounce up to about 80% of the highest point of its trajectory on a serve.

 

[UpSideDownCarl]

For people who used and play against dignics 09c we notice the second bounce have a weird arc compare to other conventional rubbers like h3 and t05. It bounces "up". Can anyone explain in science what's actually happening? why does it bounce "up"? is it less spin or more spin? If my science is right, bouncing up means it's less spin.

I am confused. What do you mean? The seconds bounce after a serve?

After others e.g. broken ball asked him to clarify, I realized that I actually don't really understand his question either. I had assumed he meant a topspin, but he didn't actually say that. He didn't even clarify if he meant a serve or not. He would need to clarify his question before it can even begin to be answered.

With that said, if he's talking about the 2nd bounce after a service, then there are probably too many factors at play for me to truly answer it. Now, it should be noted that backspins would pop higher with higher speed and spin, the opposite of topspins.

I realize, BrokenBall and DingyIBVS have a really good point. I was just assuming topspin/kicker serve. But, none of us really know if the question is about the second bounce of a serve, a topspin ball, a backspin ball or something else. So....I guess, unless ScrubPlayer comes back to clarify, we may not get clarification on the specifics of what ScrubPlayer is asking about.

BTW: thanks to BrokenBall and DingyIBVS for clearing up the information on magnus effect. It is nice to have people who do know what they are talking about to clarify things and clear up my lack of understanding on the subject.

 

[Zwill]

Usually Chinese reference the 2nd bounce as when the ball bounces on the opponent's side. I guess the initial bounce would be your racket and the 2nd bounce is on the opponent's side of the table. In this regard, his question is why the opponent's topspin coming off of D09c bounces higher on the table than with H3 or Tenergy. Less spin or more or why?

 

[UpSideDownCarl]

Usually Chinese reference the 2nd bounce as when the ball bounces on the opponent's side. I guess the initial bounce would be your racket and the 2nd bounce is on the opponent's side of the table. In this regard, his question is why the opponent's topspin coming off of D09c bounces higher on the table than with H3 or Tenergy. Less spin or more or why?

Interesting. That may be what he means. It sounds reasonable. But, since ScrubPlayer asked the question, hopefully he will clarify exactly what he means.