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Lol I give up with brokenball and James Z here, they are impossible to have normal conversations with at this point.
"wrapping" the ball.
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Okay I appreciate your explanation of your categories of strokes.
But in the video the coach is hitting the back of the ball (forwards) with a near perpendicular contact and producing a loop from it (topspin and arc). This sort of stroke doesn't appear to fall into any of your neat categories.
Is it not a loop because you define it by the shape of the stroke, or is it a loop because it has the characteristics of a loop (topspin and arc) that is *usually* achieved the shape of the stroke that you generally associate with a loop?
In other words, would you not call this a loop even though it walks and talks like one, because it achieves that behavior in a way that's abnormal to you?
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So much non-sense! USDC, you should know better.
I wonder how long it took Freitas to learn how to dribble a ball like that.
Does that help Freitas win points?
Does this make money?
Someone like Stephen Hawking could easily.
Using "forum think", if you can't play you know nothing
It is kind of like a yoyo rolling back up the string into your hand.
This forum is completely clueless. I am an expert at motion control and the modeling that is required. If the project is controlling a press, I can do the calculations to control for forces and positions precisely. By "forum logic" if can't apply the force myself, I am not capable of controlling a press. The update rates are typically 1 millisecond but the control can be updated every 250 microseconds. This is MUCH MORE PRECISE than a person can achieve. The resolution can be as fine as 100 nanometers. Can I physically control to that kind of precision? NO! but I can do the math to achieve that can of control.
Now can any of you or your TT heroes match that? I bet not. On top of that what I did before I retired generated real wealth.
OK, no one can post anymore on this topic until they dribble a TT ball off the side of a table.
I wonder how long it took Freitas to learn how to dribble a ball like that.
Does that help Freitas win points?
Does this make money?
Why not ask Freitas? Do you think he can explain it?
Someone like Stephen Hawking could easily.
Using "forum think", if you can't play you know nothing
Is it a lot of small contacts or is the ball just rolling up the paddle?
It is kind of like a yoyo rolling back up the string into your hand.
Energy! The conversion of energy from one form to another with some "gotchas". There is a trick to when the ball and blade make contact as the ball is falling. I tried explaining this long ago but I got banned because USDC allowed too many clowns to clutter the thread and I got mad and called them idiots. One of the clowns said that forces causes acceleration but acceleration doesn't cause force. Obviously this guy has never sat in a Tesla and punched it so the acceleration forces you back into the seat.
This forum is completely clueless. I am an expert at motion control and the modeling that is required. If the project is controlling a press, I can do the calculations to control for forces and positions precisely. By "forum logic" if can't apply the force myself, I am not capable of controlling a press. The update rates are typically 1 millisecond but the control can be updated every 250 microseconds. This is MUCH MORE PRECISE than a person can achieve. The resolution can be as fine as 100 nanometers. Can I physically control to that kind of precision? NO! but I can do the math to achieve that can of control.
Now can any of you or your TT heroes match that? I bet not. On top of that what I did before I retired generated real wealth.
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No matter how good you are as a motion control expert, you still suck as a table tennis player. Nothing wrong with that. But if you start out by making it clear that you suck at table tennis relative to your motion control expertise, then people will be able to figure out how useful anything you say is to improving their TT. Because you were trying to use your purported expertise in motion control to set yourself as an expert in how to hit a table tennis ball. And no it doesn't translate.
Consistently add the disclaimer that you know nothing about table tennis pedagogy and that you havent coached any strong players and that your claims to teach people how to loop or topspin are dubious at best. With that established, people can put your pronouncements about dwell time in context. Solve a table tennis performance problem with your motion control expertise. Don't pretend to understand table tennis better than people who can obviously see that you don't know how to play a heavy topspin stroke.
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Spin and more spin.
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NextLevel, do you still have footage of you doing the ball against the side of the table? I remember, 5-6 years ago, there was a bunch of people who tried and videoed themselves doing the ball on the side of the table thing in the Daily Chit Chat thread.
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I have been waiting for any of the combatants in this thread to loudly and boldly state to another combatant to
"Wrap THIS"
"Wrap THIS"
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Maybe by this time @songdavid98 has coached up his cadre of 1200-1700 adults to a more respectable level.
I would wish he would come on the forum more often and contribute... but he is likely busy with a work life, a family life, a coaching life, a sport life, and still find a way to eat and sleep.
Maybe all the H3 threads have turned him off like @Sergey-Tsos
Maybe David simply prefers to drink a cup of STFU and coach/play without any hassle or harassment from 1000 level armchair experts.
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Seeing Carl's rapid response to my thread combatant challenge, it appears that his mission days have gotten extensively longer and his Spy Phone tech exponentially upgraded.
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Someone in this thread already made some math. Although we don't have exact numbers we now know that this technique adds a little extra rotation to the ball. We might say it is likely negligible for many, but when you get in the world top 10 like Timo Boll I can imagine even the smallest improvement could be potentially an important advantage.
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Hey if he has coached a 1500 player, I would take it. Developing a player is hard. Most of the beginner players I have tried to develop in person end up around 1200, often lower. Getting a player to put in the work required to take the jump is not easy. But sometimes, you can get a player who was stuck at 1300 to take the jump to 1700 which is harder but still legit. Or you can mentor someone to change their mental approach and go from 1500 to 2000 by making them appreciate the consistency of spin more and to stop trying to play like Ma Long all the time. And if you coached yourself, like your or I did at different points, that is also legit. But the lack of self awareness that brokenball shows about technique means he needs some extraordinary success with his approach to so arrogantly mock people who are championing standard technique from the experts (and I hope enough sources have been referenced to show even the guys who disagree that nothing I have stated is abnormal TT pedagogy - it is very standard stuff). If the best brokenball can do is claim that a 2600 level player doesnt know what a counterloop off the bounce on a high ball is and is hitting the ball, at a certain point, I have to call it like it is.
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True. Can be difficult and take time. Not everyone has talent, time, ability to put in the work over time, let alone absorb all you want to convey.
Sometimes, there is enough low hanging fruit that you can get a player to realize... and that can account for several levels.
That one can be tough one. Getting a player to realize he or she of not playing within their-self and within a structure possible tactical play is a damned difficult mission.
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The key is to not think to hard about it. If thinking about "wrapping" the ball makes you have more consistency, control, and spin, go for it. If it doesn't make sense (to me I am not too fond of this word), then don't worry about it.
I think it is just a word to describe a feeling of how to hit the ball. "Wrap" the ball, "brush" the ball, "catch and throw" the ball.
I don't prefer wrap as it implies changing the blade angle a significant amount during the swing (to wrap *around* the ball), which is unpredictable and thus not good (although this is a valid technique used by many in certain circumstances). I think this is also why "wrap" is uncommon as opposed to the term "brush", which does not have any implicit relation to wrapping around.
I personally like the idea of "catching and throwing" the ball, as thinking with this phrase helps me "absorb" the ball, and with it a noticeable increase in control and spin.
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Since I was last active here, a lot has been written here. I didn't have much time. Still I want to clarify something.
We all see that TT players, profis or not, simply do change the angle of the bat during the stroke. I don't know why would someone dispute it, and I'll leave it at that. Stroke can be shorter or longer. The bat angle change can be more or less. Any combination. There are reasons for why this is so, imo, it is due to the construction of the body. That is also why I like what NL said, that thinking about the stroke is much more useful than thinking about "what matters", the contact point.
Now I knew that the contact point is short, and later zeio made the timings precise - approx. 1 ms. Honestly I expected there won't be any significant change of the bat angle possible, during that short contact point. It turns out, it is quite possible to change the angle by 2 degrees, and I'd guess the change can be even more, maybe 3-4 degrees max. This obviously influences the ball - I'll get to that later, but the point is, that even if it were not possible, even if the bat angle change during the contact interval were insignificant, we, profis or not, would still change the bat angle during the whole stroke! It is independent. We do this (change the angle during stroke), because it is natural for the body, and for the goal, too.
Now let's say we close the bat angle during the contact for 2 degrees, from 40 to 38. What is the difference to another contact in the angle 39 degrees, which we don't change during the contact. I don't know exactly, I tried to calculate it in some crude way earlier, and the result was that there is some 5% difference between those two contact points. I'm not sure, it may be more. It may add some additional nice extra plus, but as I said, imo, it is not the main reason why we change the bat angle during the whole stroke.
Earlier, I was perhaps a bit to excited (that indeed what happens in contact is richer) and my formulations were not clear, and that lead ben1229 to ask about it, whether I want to focus on doing that extra during contact point. I don't, I hope it is clearer now.
Apart from that, this thread is more about OP's ego-wrapping, than ball-wrapping.
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I don't dispute it. People aren't calibrated machines so the strokes aren't perfect. My point is that it isn't desirable because the ball will go to widely different locations depending on the timing and how fast the paddle is rotating. Also, 2 degree is not wrapping anything.
My disputes is with those that say wrapping is a good thing yet they can't say now much and what happens if they are a little early or a little late. No one has answered that.
We have assumed the contact time is 1 ms. This may be approximately right if the impact speed is 20 m/s as stated way up in the beginning. It will be much less in a loop/counter loop rally.
Another thing. The ball will tend to bounce off the rubber depending on the angle if incident. If a flat hit should be making contact with the ball at 90 degrees and the actual impact is 89 degrees, the ball will tend bounce off at 91 degrees depending on the spin. The issue is that some of the translations momentum get translated in to rotational momentum.
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We speak about real concrete strokes, with real and deliberate bat angle change during those strokes. zeio posted videos of those strokes, the bat angle change is clearly visible, and it is also clear (for everyone except you) that it is deliberate. It is wanted, it is desired. PUNKT.
The rest - it feels tiring to repeat over and over what was just said, trying to explain it for you in another words, which you will again fail to understand or acknowledge. DELAY NO MORE.
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Hello, I found this thread to be very interesting. However, I don't understand why we only take into account the speed of the racket and ball and not the acceleration. If the collision happens as the racket is still accelerating, the contact time should be extended compared to the model where the racket is at a constant speed. This explains why the follow-through is so large since maximum racket speed occurs after the collision followed by deacceleration.
Additionally, instead of thinking of the "wrapping" stroke as two parts, hitting and then brushing, why don't we think of it as a curved racket path. Then, "wrapping" the ball is simply fitting the curve to where the ball is, i.e finding the hitting zone. Not only does this simplify what the player needs to do, but it also introduces rotational mechanics which can further explain the directional change of the ball in response to the changing racket angle. Similar to the physics trick where demonstrators spin a cup of water around their body without it spilling onto their head.
Also, anecdotally, my feeling when wrapping the ball on my backhand where the rubber is softer is that the ball is held in the rubber, redirected, and then launched out. I don't particularly feel a wrapping sensation around the ball. What reaffirms this view is the highspeed video from butterfly posted earlier of a collision with a stationary racket. The ball essentially stops moving until the rubber rebounds and restores itself. This means that as long as the force being applied to the racket(and the ball) is greater than the force of restitution of the rubber, we should be able to hit the ball at one angle and have the ball exit when the racket is at another angle.
Additionally, instead of thinking of the "wrapping" stroke as two parts, hitting and then brushing, why don't we think of it as a curved racket path. Then, "wrapping" the ball is simply fitting the curve to where the ball is, i.e finding the hitting zone. Not only does this simplify what the player needs to do, but it also introduces rotational mechanics which can further explain the directional change of the ball in response to the changing racket angle. Similar to the physics trick where demonstrators spin a cup of water around their body without it spilling onto their head.
Also, anecdotally, my feeling when wrapping the ball on my backhand where the rubber is softer is that the ball is held in the rubber, redirected, and then launched out. I don't particularly feel a wrapping sensation around the ball. What reaffirms this view is the highspeed video from butterfly posted earlier of a collision with a stationary racket. The ball essentially stops moving until the rubber rebounds and restores itself. This means that as long as the force being applied to the racket(and the ball) is greater than the force of restitution of the rubber, we should be able to hit the ball at one angle and have the ball exit when the racket is at another angle.
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The problem is neither the physics or the technical instruction. The problem is that an engineer who doesnt play or really understand high level table tennis is trying to teach TT as an authority.
I never used the phrase "wrapping" before this thread. All I have argued is that from a pedagogical and TT technical standpoint, people who try to make hard distinctions between stroke and follow through are often placing limits on their technique. My table tennis got better when I looked at the stroke ss a continues movement per your second point. And I could continually change the effect of my ball by adjusting the trajectory of that movement. I concluded that the idea that all that matters is what happens at contact might be true from a physics standpoint but is misleading from pedagogy and technical development standpoint.
So we now have our engineer stuck trying to argue against things that no one ever claimed. Of course wrapping can be excessive and that the components of the vector can be mistimed, just as is the case with any stroke. A stroke should usually produce two effects. The speed effect and the turning effect. Sometimes brokenball falls to distinguish between both effects by focusing on angle changes. While forgetting that the wrapping is mostly done to accentuate the turning effect. Of course if mistimed, a turning effect might turn into a hitting effect, but his framing in terms of exit distances based on exit angles completely missed the point.
In what will hopefully be my final post on this thread, here is an example of wrapping gone wrong. The server is arguably Australia's greatest ever player so he must know what he is doing taking this level of risk.
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At least I wouldn't teach non-sense. I do play. I played today. Now I just play for the health of it. Today my practice partner was chopping and I was looping balls to get them back most of the time.
On my BH I was playing with 802-1 1.8mm which is very good for flat hitting
My mistake is not copying the statements made from another thread into my fist post so the guilty party would be clear.
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This thread is full of people trying to justify wrapping the ball. The ball is not stationary during this event so how does one "wrap" the ball
If I posted the math, would you understand it? You never have before.
I want someone to show me the math. If the ball is traveling 20 m/s If you are swing up with a paddle speed of 20 m/s then in 2 ms it may be possible to wrap 4 mm of the balls surface if the timing is perfect. So far no one has made the case. The spin would be almost 80 rps. if the ball hit the paddle perpendicularly or normal to the paddle the normal speed impact speed is still 20 m/s. In this case you are relying on the incoming energy to be enough to get the ball over the net.
Wrapping the ball may work a small percentage of the time. I know people can get lucky a hit the ball at just the right instance.
What really get me is the forum logic. By forum logic, someone like Stephen Hawking would know nothing about the physics of TT. Being able to dribble a TT ball is a plus. Give me a break.
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Shoo...nothing to see here. - zeio
Below is a quote on pronation/supination from another Polish study (2018) by the same authors on the angles in select joints during FH topspin among 10 of the top 16 female players in Poland.
https://pubmed.ncbi.nlm.nih.gov/29523053/
Another study (2019) by Japan Sport Council on 10 JNT male players, 8 righties (a silhouette of possibly Harimoto is used), 2 lefties, measured the racket head speed and racket angular velocity (tip of racket) on 3 types of shots. From Figure 4, both values reach the maximum ~30ms after impact, suggesting the racket accelerates through the contact. From Figure 6, the racket swing reaches the maximum speed ~10ms before impact on step over (crossover?), ~5ms after impact on chance ball, ~10ms after impact on step around.
一流卓球選手のフォアハンドトップスピンストロークにおける肩と腰の可動性について
https://www.jpnsport.go.jp/hpsc/study/history/tabid/1579/EntryID/236/Default.aspx
Figure 5
Upon impact:
Racket head speed = ~22m/s (max ~23m/s at ~30ms after impact)
Racket angular velocity = ~1500deg/s (max ~1600deg/s at ~30ms after impact)
https://i.imgur.com/hK4wbFz.png
Figure 6
Step over (max speed ~10ms before impact)
Chance ball (max speed ~5ms after impact)
Step around (max speed ~10ms after impact)
https://i.imgur.com/QMiWytI.png
Another study (2006) from Taiwan, with participants such as Chiang Peng-Lung (only one shown in the plots), Chang Yen-Shu, Chen Chien-An, Chiang Hung-Chieh, Huang Sheng-Sheng, measured the angles and angular velocities of practically all major joints during a FH slow loop and fast loop.
The data shows that the penhold and shakehand players supinate and then pronate the forearm (while remaining in supination), and ulnar-deviate and then radial-deviate the wrist (while remaining in ulnar deviation) moments before and through the contact. In terms of angle, penhold and shakehand players supinate for a similar amount but the former radial-deviate double the amount (34.75±4.69 vs 16.88±4.27 for slow loop and 36.38±15.79 vs 20.06±3.06 for fast loop) while the latter pronate double the amount (10.29±1.25 vs 18.19±9.95 for slow loop and 8.75±4.52 vs 19.89±15.24 for fast loop). In terms of angular velocity, the same trend is seen for penhold (radial-deviating 276.70±0.06/303.98±22.75 and pronating 98.26±9.05/89.86±13.84 for slow/fast loop) and shakehand players (radial-deviating 164.90±42.93/211.73±53.63 and pronating 142.81±80.87/181.25±151.16 for slow/fast loop).
優秀桌球選手正手拉球之運動學分析
https://imgur.com/a/2ti03a0
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