All of the balls burn (no surprise there); The "plastic" ones burn more slowly, which may mean they are safer.

Jacek, a slower burning ball looks safer, but there are certainly a boatload of smoke and chems from the burning plastic, the celluloid balls appear to burn a lot "cleaner" :) How is the killa BH coming along?

Depends on the stroke.  But you forget that the racket has two to four millimeters of cushioning sponge that makes that collision quite different than the collision with the table.

And players report weird shots all the time in my experience.  How many times have you seen a player look at his racket after missing a shot?  I see that all the time. That's an indication that the shot didn't work the way the player expected ... for whatever reason.

Time and more player experiences will prove this out.  This is where the NP 40+ is superior to celluloid balls.  If it had a bit more bounce and a reasonable price, I'd be pretty happy with it.

You were pointing out that the racket would be more likely to create "weird" results.  Given the surface differences I'm simply saying that isn't necessarily so.

As for "weird" I took that as meaning unexpected and hence inconsistent from the beginning.  So in my mind we've always been discussing consistency.  Anyway, my point is that I believe players observe "weird" results all the time and that this could very well be an indication of inconsistent ball performance.  I don't think we can conclude that we are not experiencing and seeing inconsistent ball rebounds from rackets.

Those details will be hard to come by. But getting back to the beginning, I'm merely suggesting the possibility that the NP 40+ seam construction could be contributing to what many people are reporting as a truer and more consistent bounce.  It seems like a reasonable hypothesis to me and I haven't found your counterpoints to be very persuasive.  

That said, the hypothesis is far from being demonstrated as true. Heck, right now we can't even objectively say that the bounce is actually more true. Though it certainly seems to be.

No, as far as I'm concerned all celluloid brands that I've played with will exhibit bad bounces from time to time.  

Sometimes we do lots of things.  But I'm not putting too much faith in any generalization here.  I'm simply making an observation that one ball has a better than normal bounce consistency than normal (celluloid) and that maybe the ball's relatively consistent seam thickness is contributing the reason for (or at least part of the reason for) that consistency. I didn't say it was the cause.  I supposed that it might be.

BTW, this consistency of bounce was something observed by Sean O'Neil many months ago and is one of the reasons he gave for looking at this ball as a "game changer."    From his post:

http://www.usatt.net/forum/viewtopic.php?f=5&t=356" rel="nofollow - http://www.usatt.net/forum/viewtopic.php?f=5&t=356

Yes, the ball slows down significantly. Part of that is parasitic drag and part of that is the horizontal velocity being changed to vertical velocity due to the topspin.

But there's a whole new wrinkle to the bounce consistency question.  I looked at Pathfinder's video again and his method of dropping the ball appears to introduce inconsistencies all by itself.  He rolls the ball through an opening in a bottle.  In some shots the ball seems to drop cleanly, rolling off of the lip.  That raises the question of what the drop height actually is since the ball rolls downward before experiencing full freefall.  But in other drops, the ball seems to momentarily catch on the opposite lip of the opening causing the ball to "freeze" momentarily at a height of around 290 mm (precisely 292 mm in one shot). In these shots we can actually observe and measure the effective release point.  But it too low and It may or may not vary.  It could be that it varies less on the 40+ balls because perhaps they "catch" more consistently. But that's pure speculation. You'd have to view all the videos to know what's really happening. He only shows exemplars in the YouTube video.

No, I can't control for the spin.  Even robots are inconsistent in the balls they throw.  I can only observe a general tendency and range in a drill where the ball is being sent with the goal of consistency.  Of course there is a lot of inconsistency within the drill.  But there are occasional outliers that far exceed the normal range of flight paths.

 

I'm inducing from my general experience with materials and their behavior.  The problem with deducing from the existing data is that it is so very limited.  There are problems, of course, with my induction.  But like I said, it is just a working theory.

I was also remembering that the ITTF made an issue out of the shell thickness when evaluating the seamless ball in 2013.  Their conclusions may not be correct, but they presumably came to them by analyzing empirical data from their tests.  So I went back and looked at the paper.  They correlated bounce consistency with shell thickness but even more-so with veer results (due to limitation of measuring only six points for thickness on seamless ball).  They also implicitly admitted that the "imperfect celluloid balls" have irregular bounces.  

Perhaps.  I don't know the math on that and have no intent to check on it.  But it's the one thing that would be worth at least doing a napkin analysis on before dismissing it.

I believe my release mechanism and impact target will work well enough to test likely conformity to the ITTF spec.  I may be able to borrow some Joola balls in order test them on my apparatus.  My bet is that the seamed Chinese balls will be within the design spec. when tested on my apparatus.  That said, they might very well have a lower average bounce. The DHS celluloid balls I tested were on the high side of the spec.