OOAK Table Tennis Forum

Please try the links above; not all waves necessarily ripple the blade. The vibration patterns mentioned previously are continuous modes and relatively slow compared to the ball dwell. The initial "sound" type wave is the one that's in the right timeframe (not the one you hear as the material vibrates the air, but the one that travels through inside), and those tend to be compressive in relatively rigid solids as mentioned. Compressive means "tight & loose" like your head during a throbbing headache, not "up and down".

This is the stuff from basic STEM physics but I might hit up the relevant specific texts on it later to see what's up. I believe Rayleigh-Love theory & its extensions.



If the energy is limited to such a small region it would damage the wood. When you nick your nail into the wood (and it doesn't take much), that's what happens when it's not spread across a wide region, like the whole blade at the speed of sound through wood which is very fast. The wide region mean more moving mass.

Yes, it's very interesting.


So the size of the region must be somewhere between the whole blade and the edge of a fingernail. This is good progress.

The size of the region is the whole blade at the speed of sound (ie molecular coupling) through a solid. This doesn't really move the blade up and down anyway.

Consider the difference with pressing into a rubber. Notice it bounces right back and thus effects are easily localized. Wood as a rigid solid doesn't work like that.

It isn't rigid. That's what "flexible" means.

It's a matter of degree. The flexing of the blade neck (if you death-grip on the handle) is maybe a couple mm for the slowest commercially available blades. The blade transverse vibrations are much smaller than this and impossible to see. The way compressional waves work has even lessor order of magnitude effect on the surface.

"Eliminate the impossible..."
It was argued that one mechanism was impossible. So we identified a mechanism that is possible. We know that it need operate over only one small region under the ball, and that this region is smaller than the entire blade but larger than the edge of a fingernail.
It's good progress.

"The blade transverse vibrations are much smaller than this"
I'm only talking about the initial disturbance (under the ball strike), not the vibrations which result.

The initial waves are compressional, ie waves of high and low pressure inside the blade. I'm not sure what's hard to grasp about this.

> We know that it need operate over only one small region under the ball

It doesn't. The longitudinal waves travel through the entire blade. They travel at ~3km/s, or about ~0.02ms across the whole blade.

> It was argued that one mechanism was impossible. So we identified a mechanism that is possible.

Just because one mechanism for ghosts is impossible doesn't mean any other for some other kind of ghost is necessarily plausible.

If it's still your position that under a ping-pong* relevant hard ball strike the wood of, say, a VKM does not "give" under the ball, not even .1mm, then that could be tested.

Feel free to try. It's going to be exceedingly difficult without serious equipment or very clever technique given the impact video above is already at the limits of what's commercially viable, and what you're trying to measure is order(s) of magnitude smaller and faster.

To be honest I'm not sure what's being demonstrated. That slower blades are slower? We already know that...

Is it your position that e.g. a VKM will not "give", not even .1mm?

Probably not in <<1ms, especially not with 4mm coupled rubber dampening on top.

Ok, that's clear, thanks.
So, a test is necessary.
That's all I have for now.

TLDR entrenched positions over whether a blade (define blade) flexes (define flex to your own satisfaction) under ping pong conditions (define ping pong conditions, you get the idea) remain entrenched. However some agreement on there being faster and slower blades.

In other news, Christian theologians still debating how many angels can fit on the head of a pin.

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Retriever (sometimes golden, but often leaden)
Moderator, Inverted Retriever Technique sub-forum - http://ooakforum.com/viewforum.php?f=74

I think there'll always be those who contend with the science, and those who believe any contention to imply controversy.

TT blades don't seem to be terrible complicated overall outside of the basic speed metric. IMO there's a habit in equipment or any other sort of reviews to make the reviewer appear more sophisticated by introducing plausible distinctions, so those who don't adopt the language of ambiguous nuances be dismissed as unrefined. Wine reviews come to mind with the ambiance of vintage and terroir when supposed connesiours are easily fooled by switched bottles or even dyed white wine.

The lesson from this thread should at least be caveat emptor when it comes to fantastical properties of TT blades.

Ah, I see what you're getting at. Well, my answer to that (when you say you meant "something else" when you said "mass") would be that, to anyone with a high school level science education, "mass" has a very specific meaning that goes back to Sir Isaac Newton. In other words, pretty much everyone means a specific thing when they talk about the "mass" of a table tennis racket. If you want to use the term "mass" in a different and novel way, then you add an element of confusion to the conversation.

Iskandar