Hello, Clark,
I appreciate the effort you have put into this subject. The ideas you present are good ideas. Your fundamental points here are--
1) Stiff load-bearing materials take less energy because they deflect less
2) Strong plates take less energy in bending because they are thinner.
You have to be careful about applying these rules to pneumatic tires--
1) The load bearing material in a tire is the air, not the rubber. Making the air stiffer (higher pressure) helps because the tire deflects less. But, in this case lowering the stiffness of the rubber also helps because it absorbs less energy (bends easier). The tire deflection (contact patch) is almost exactly the same no matter how hard or soft the rubber is. For a solid rubber tire, the conclusion is the opposite because the rubber supports the load.
2) A "soft, thick" tire wall is bad because the energy for bending goes up as the fourth power of thickness. The ideal tire wall is soft in bending but very strong and stiff in tension. That is the purpose of the cords, allowing great tensile strength in a thin, flexible tire. And, of course steel would do this best.
Ernie Rogers
Quote:
Originally Posted by ConnClark
Yes air does return more energy than rubber and steel. However the less it is compressed or disturbed the less energy lost. The same holds true for rubber and steel, the less it is flexed the less the energy that is lost.
hard rubber looses less energy.
http://www.vittoria.com/index2.php?o...=358&Itemid=71
From the box on the second page.
"Rubber compounds affect rolling resistance because they absorb different amounts of energy. In rough terms, thick, soft rubber usually absorbs more energy than thin, hard rubber. "
Caster Wheels - Performance TPR Wheels - Soft Rubber Wheels - Hard Rubber Wheels - Mold-On Rubber Wheels - Elastomeric High Tensile Rubber Wheels
From the comparison of types of caster wheels. Read the descriptions of the Soft rubber wheels and the Hard rubber wheels.
"Soft Rubber Wheels are a good choice for those applications where the average load is light with occasional loads using the full capacity of the wheel. Soft Rubber Wheels are manufactured of quality materials with a resilient rubber tread bonded to the hard rubber core."
"Hard Rubber Wheels are used where low cost, easy rolling wheels are required. Hard Rubber Wheels offer good floor protection, are quieter than steel wheels, and are strong and chip resistant."
Occasionally someone makes an advance in material science like adding silica to tire rubber allowing softer rubber to have a lower rolling resistance and better wearing characteristics. This is the exception and not the rule. It can be added to harder rubbers too but they won't grip as well.
My father designed tires. I learned a lot from him. |