Musicfreak0 wrote: We used some Kingnik ones last roster. I didn't think there was much of a difference coming from the Donic Poly, but I'm doing some tests to compare velocities in flight and rebound velocities, as well as flight deviation, etc.. Others have done tests and showed that 5 out of 6 balls in the first carton were illegal as they were oversized, and there seem to be many others that are oversized. I've heard nothing but complaints from others about how they float up in the air, go too slowly, and seem to wobble around. Be that as it may, I'm convinced that most (or at least a lot) of it is just people overreacting to a subtle change. One thing I noticed is that the Donic ones seemed to break a lot more often. Anyway, I'll get back after these tests and hopefully I'll be able to provide some figures for this discussion.
Went back to Leaflet T3 (ITTF's ball specs are listed in there). Hadn't read it recently. Here's what it says for diameters:
Quote: B.3 Size Conformity
... celluloid balls ...
For non – celluloid balls:
The minimum diameter of every ball must be at least 40.00mm and its maximum diameter must not
exceed 40.60mm. The sample mean average diameter, i.e. the mean of the average of the maximum
and minimum diameters for each ball, must be in the range 40.00-40.50mm. Values below 39.70mm
or above 40.75mm are considered in our calculations as outliers.
B.4 Size Regularity
The standard deviation of the average diameter may not exceed 0.06mm.
So if balls are consistently above 40.50mm they're what.. not exactly illegal unless a lot of the balls out of a batch tested are so? How big were the Kingniks that were too big?
On weight:
Quote: B.1 Weight Conformity
Law 2.3.2 specifies 2.7g, but any weight between 2.67 and 2.77g is acceptable for any one ball. No
more than 1 ball out of the 24 sampled may be outside this range. The sample mean must be between
2.69 and 2.76g. In carrying out statistical calculations we treat any weights less than 2.60g or greater
than 2.85g as outliers.
B.2 Weight Regularity
The standard deviation may not exceed 0.03g.
So Igor's 2.78-2.80g are illegal.. 
Out of curiosity, I got out some balls and weighed them. Note that my balance only weighs to the nearest 10 milligrams (.01g) so it's not really accurate enough for this.
Kingnik 40+ seamless 3 star Premium sticker, date code XAAF (I forget how to translate this):
2.75, 2.76, 2.75, 2.75, 2.75, 2.75
Sanwei 40+ seamless three star
2.78, 2.77, 2.78, 2.77, 2.78, 2.78
iPong 3 star Sphere 40+, date marked on box: 2015.10.10
2.72, 2.73. 2.72, 2.72, 2.73, 2.72
The Sanwei had the best confidence-inspiring box. Technically slightly overweight. Variability between balls in a box: excellent.
Iskandar
|
), I really liked it. It seemed noticeably bigger than a normal celluloid ball, and it was a bit too light for my taste, but otherwise waaaay better than anything I've tried so far, even the 3 star XSF. Well, actually now that i think about it, I tried a 3 star celluloid nittaku ball. It had the blue stamp and it was specifically a premium 3 star i think. I like that too.
