SOKAZ forum

[h3n]

[ib]

Iz nekog razloga sam naivno mislio da pokušavaju napravit što sličnije loptice celuloidnima.

Što bi rekao Guga:

[Drogi]

@55 - hrapavija loptica ne mora nužno i znaciti bolja hvatljivost? . Kod tacky guma daleko bolje prijanjaju glatke Butterfly loptice od ostalih. Primjer se može vidjeti na Geekovom siteu gdje Softa drži reket s dva Hurricane-a 3 neo i lopta se doslovno ljepi, a s lopticama tipa DHS ili Nittaku to nije slucaj.

Ono što hrapavost loptice sigurno dodaje to je trenje u zraku to jest ima veci otpor dok putuje zrakom i dok rotira u zraku, od tud valjda i osjecaj manje rotacije.

E sad trenje između dvije površine ovisi o puno faktora, a ovaj nama oku vidljiv "hrapavi" nije nužno bolji za trenje jer se isti odvija na puno manjem nivou tam nekom mikro/nano ili tako nešto . Dobar primjer su gume za formulu gdje slick gume bolje prijanjaju od istih takvih koje imaju (utor ili ripne) većina ljudi koji su pratili se sjecaju kada su usporavali formulu na sve moguće nacine, a tako i zabranom slick guma.

Pošto sam ja iz "mladih" snaga sokaza i nemam pojma o svemu vec pisem iz glave i neke logike ovo ne mora biti nuzno tocno, ali bih zato zamolio uvažene starije clanove ako imaju korisnih infomacijama da ih podjele i argumentiraju.

[geek]

U skladu sa novim standardima i bešavne loptice, u najnovijoj verziji, su promijenjene, pa manjak rotacije može biti posljedica povećane težine. Apsolutno je bez veze što ITTF ne objavljuje dinamičke testove loptica. Znači, uzmu robot, u njega ubace 100 loptica, te izmjere srednje vrijednosti rotacije, brzine, dinamičke visine odskoka. Poslije, svatko bira po svom nahođenju. Ovako se sve završava na osobnim mišljenjima (i optužbama), bez mogućnosti eksplicitnog dokaza. Prije neku večer sam uzeo "stare" šavne loptice (1. generacije), da "osjetim" imaju li više rotacije od novih. Odgovor: NE.

Evo, što piše na OOAK forumu:

"ABS balls are harder and are perfectly round. The hardness of the ABS material is why people often describe Nittaku Premium balls as being "heavy" when they are in fact the lightest 40+ ball currently sold. (Average weight 2.68 grams compared to 2.76 for DHS 40+ (STARE) and seamless). As you get used to ABS balls, either the Nittaku or the DHS D40+ (NOVE), you will like them a lot. The consistency of the bounce is what will sell you. They bounce exactly the same height as celluloid, which is in marked contrast to the DHS 40+ (STARE) you have been using (which bounce lower) or seamless (which bounce a little higher)."
_________________
Butterfly Jonyer-H FL
FH: DHS Hurricane3 Neo H37 2.1
BH: DHS Hurricane3 Neo National 2.2
中國膠 (KINESKE GUME)

[Drogi]

@Geek -

[Drogi]

Evo još malo infa o lopticama:

izvukao iz intervjua s Ma Longom gdje isto potvrđuje priče nekih iskusnih sokazovaca da nove ABS lopte ne rotiraju tolko dobro što znaći da ne prijanjaju uz gumu tolko dobro.

Ma Long:"
This is the only tournament before WTTC which I can get used to the new (Nittaku) ball. Overall, I feel good about today's match."
(Note: He mentioned previously that Nittaku and DHS ABS balls are not as spiny as old DHS balls.)"

[ib]

Ovaj sport će stvarno postat ko lupanje rekreativaca na stolovima na Jarunu.

[Brod]

Ma naviknu se "konji" na sve!
Kad smo počeli trenirat s plastičnim,niko nije mogao dobit Wolfa i Vjeku,danas se ipak malo drukča slika kaže!
_________________
Ako ti je slaba pamet,moraš imat jaku kičmu!

[doktor]

[Iceman]

evo, naletio na jedan odlican post o plasticnim lopticama:

"In 2000, the ball manufacturers had changed from 38mm balls to 40mm, and they tried to keep the thickness of the shell same so as to retain the nature of the rebound same.
According to these calculations the weight of the 40mm ball was decided at 2.78 grams. This was to provide near the same shell thickness as the 38mm ball.

In 2016, ABS plastic came out on market, this plastic has a low specific gravity compared to celuloide 1.10 g/cm3 vs. 1.40 g/cm3 and therefore, the new balls have a very thick shell. Here's the main reason that plastic plays differently than celluloid.

If use of plastic of high specific gravity and make the wall of such thickness as celluloid then plastic balls will play almost like celluloid. Until then, we're bound to this ABS plastic and we have much grief with this ball..

Recently, a Japanese research group made a comparative analysis of the Nittaku 40 (celluloid) and Nittaku Premium 40+ (plastic) and they definitely proved that the plastic has a different bounce and a different ballistics. It's interesting to read and need to learn each coach and each athlete."

i sad predobar pdf pun formula i grafikona u kojem ce uzivat svi matematicari (ib? ):

https://www.researchgate.net/profile/Sho_Tamaki2/publication/312344216_Effect_of_Changing_Table_Tennis_Ball_Material_from_Celluloid_to_Plastic_on_the_Post-Collision_Ball_Trajectory/links/587b85dc08ae4445c0641f3a/Effect-of-Changing-Table-Tennis-Ball-Material-from-Celluloid-to-Plastic-on-the-Post-Collision-Ball-Trajectory.pdf

kom se ne da citat sve, bitan je kraj (ali i dalje dosta teksta ):

"To bring all the results together and consider game situations, some adjustments for predicting ball trajectories of plastic balls are suggested. First, as mentioned above, since services with back-spin will experience greater deceleration upon collision with the table, players can serve the ball that does not approach too close the opponent. When the ball decelerates upon collision with the table on the opponent’s side and does not go beyond the end of the table, but instead stays within the table boundary, it is more difficult for the receiver to return the ball with great top-spin since the table obstructs the swing of the racket. Therefore, a server can make use of this phenomenon with plastic balls and the receiver should expect a higher possibility of its occurrence with plastic balls than with celluloid ones. In addition, since plastic balls have a higher coefficient of friction with the table, they are expected to present greater changes in trajectories to their post-collision trajectory, not only regarding back-spin, but also side-spin or combinations of back-spin and side-spin. Therefore, players should expect greater changes in trajectories with plastic balls and consider new tactics to make use of these characteristics of plastic balls. In addition to adjustments in the prediction of ball trajectories of slower balls such as a service, some adjustments are suggested for plays with faster balls such as a smash or a drive. Players should expect drives to accelerate more with a plastic ball having greater top-spin upon collision with the table than a celluloid ball, so the plastic ball approaches the player faster than expected. A smash with a plastic ball having greater initial vertical velocity will bounce off higher than expected in a smash with a celluloid ball. These behavioral changes between the two types of the ball may possibly influence defensive players who play far away from the table (often referred to as a “chopper”). If their opponent smashes a plastic ball, the ball will bounce off higher than expected in a smash with a celluloid ball, giving the player more time to react and hit the ball as precisely as they desire. On the other hand, if the opponent responds to a back-spin ball hit by a chopper with the back-spin “stop” technique, which also decelerates the ball with counter back-spin, causing the plastic ball to experience more stops upon collision with the table, choppers will have to travel back and forth for greater distances. However, since the behavior of the balls upon collision with the racket was not investigated, future research should be conducted if specific tactics are to be recommended with regard to the change in ball materials. Moreover, since only balls having back-spin were tested in this study, further research is required to identify how sidespin or other types of spin with different velocities affects the behavior of the two types of the ball. "


kom se dalo citat, mogli bi prokomentirat malo...
_________________
I must not fear. Fear is the mind-killer. Fear is the little death that brings total obliteration. I will face my fear. I will permit it to pass over me and through me. And when it has gone past I will turn my inner eye to see its path. Where the fear has gone there will be nothing. Only I will remain.

[Stip]

Hvala Pongi, zanimljiv članak
Pročitao sam cijeli pdf, sa strane znanstvene metode vidim čistu ljepotu, ali iskreno većinu terminologije i metoda nikad nisam koristio od faksa do danas, a prošlo je nešto godina ....

Ako pustimo metodu na stranu, zaključak je isti kakav ostane nakon što izbaciš psovke iz komentara mnogih SOKAZovaca:
- To (****no g**no) od loptice odskače previsoko, zato svaku (****nu) može zdrajfati
- Stane u zraku, (p***a joj ********), ne dođem do nje, (***em ti plastičnu mamu)

Po meni je ključna rečenica članka:
"Since the time to react to the ball is limited because of the fast rallies, it is assumed that players anticipate the approximate amount and direction of the spin applied to the ball, velocity of the ball and the resulting trajectory of the ball that is returned by the opponent player. "
Ili drugim riječima, ne stigneš reagirati na to kako loptica stvarno odskoči, već barem započneš udarac temeljem pretpostavke kako će loptica odskočiti. A ta pretpostavka temeljena je na stečenom iskustvu. A to iskustvo je nakon uvođenja plastike često pogrešno.

S jedne strane, zato sada najbolje prolaze igrači koji su uspjeli 'zaboraviti' celuloid. A s druge, zato je izluđujuće kako su i plastične loptice međusobno različite. Ne postoji jedan standard kojem si se morao prilagoditi nakon prelaska na plastiku, već ovisiš o loptici s kojom domaćini igraju.

[Iceman]

tako je Stip,

i isto mi je zanimljiva opservacija da plasticna loptica ima vece trenje sa stolom od celuloidne, tako da su side spin serve posebno neugodne jer loptica skrene vise nego inace...

to jako dobro objasnjava kako ljudi sa neugodnim servama nisu puno ili nista izgubili sa plasticnim loptama...a prije uvodjenja plastike se mislilo da ce biti drugacije...

isto tako da je lakse izvest kratku servu koja 2 puta pada zbog povecanja trenja i tzv. braking efekta...
_________________
I must not fear. Fear is the mind-killer. Fear is the little death that brings total obliteration. I will face my fear. I will permit it to pass over me and through me. And when it has gone past I will turn my inner eye to see its path. Where the fear has gone there will be nothing. Only I will remain.

[mixer]

Igraš sa antispinom tak da ne zbunjuj ljude.

[Iceman]

?
_________________
I must not fear. Fear is the mind-killer. Fear is the little death that brings total obliteration. I will face my fear. I will permit it to pass over me and through me. And when it has gone past I will turn my inner eye to see its path. Where the fear has gone there will be nothing. Only I will remain.

[trnac]

to je samo mixer

Njemu i prašina smeta.

[mixer]

Pa vi znalci bi mogli i na dasci za peglanje igrat