Thanks, Racer,
So, I conclude that all else being equal (including coefficient of restitution or internal friction), I can reduce the strain energy and therefore the energy loss by using softer rubber (lower elastic constants) in both the casing and the tread material. Of course, thinner components are also desired.
I am over my head here-- adding a second phase to the rubber, such as colloidal silica, could act to "pin" movable elements in the small-scale (e.g., molecular) structure thereby reducing internal friction. (This is called dispersion hardening in metals.) While hardening may occur, this could actually be detrimental.
Comments?
Ernie Rogers
Quote:
Originally Posted by CapriRacer
Here's the deal about the tread elements - the opposite of the grooves.
When you bend a flat plate, the surfaces are either put in compression or tension. In the case here, the "plate" is being unbent, and the base of the tread elements is being compressed.
But there is another factor to consider: Pantographing. That's the word that is used to describe what happens because of the cords in the tire.
If you consider the individual cords to be attached to the adjacent layer, what you have a a series of parallelograms. So as the tread enters the footprint, the undertread "unbends" and gets shorter (it is traveling along the "chord" and not the "arc" of a circle), so the width gets wider.
That means that not only is there movement in the radial direction (We're calling it "bending") and movement in the circumferential direction (because of the "chord" effect), but there is also movement in the lateral direction.
Another thing to consider is that compared to the cords, rubber is very flexible. So changing the tread rubber has an unusually high proportional affect on the energy not returned, compared to its effect on stiffness.
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