Is It Strong Enough?

While walking through a field of wildflowers one might find a feather nestled amongst the flora. The feather is light, airy and delicate. Beneath the floral landscape, one might find a stone. It is heavy, solid and strong. Based on these quick observations, one might decide that the stone is superior to the feather. This same thought process occurs daily when designers consider metal vs. plastic as a material for gearing.