Sponge hardness on rubbers

[zeio]

In before hardheaded engineer after wasting enough of my time. The interest here is to find out the general trend, not an outlier. Those Giant Dragon Guard/Guard Special do not even qualify as an outlier as I highly doubt they are legal. How they got approved in the first place is another story. So stop citing them to support your arguments. Stop spreading myths.

https://equipment.ittf.com/#/equipment/manuals
M4 RC MANUAL September 2023

2.3 MATERIAL & TYPE
Rubber implies any material that can be stretched at room temperature to twice its original
length, and that, after being held in the stretched state for one minute, retracts within one
further minute to less than 1.5 times its original length.

 

[brokenball]

But Giant Dragon Guard exists or did exist. It blows your theory out of the water.

It seems that the type of rubber makes difference difference. So each type of rubber requires a formula or graph.
So how can you use hardness to predict COR when it depends on other factors?

BTW, the harder the rubber the less energy it absorbs so the less energy is lost. When bouncing off a steel plate the COR is about 0.9 for the TT ball alone since the steel block doesn't absorb and significant amount of energy.

I don't understand your problem. There is a difference between hardness and elasticity.

 

[igorponger]

REBOUND INDEX IS OF UTMOST IMPORTANCE.

Tensor rubber is a generic name for all the highly resilient rubbers on market. The "dropping ball" test is now preferably used in making rubber materials, Those materials giving rebound index over 40% are classified as high resilience. The Hard series sponges may differ in elasticity by far, either tough and springy. This is to say that Hardness on table tennis rubber is a misleading info, anyway.

 

[lodro]

not being critical re the ball resilience testers but would like to ask : "If an identical sponge is tested using two different rubbers, eg, a rubber with a very hard top and another with a very soft top will this influence the outcome of the test ???"

 

[brokenball]

not being critical re the ball resilience testers but would like to ask : "If an identical sponge is tested using two different rubbers, eg, a rubber with a very hard top and another with a very soft top will this influence the outcome of the test ???"

Yes.