Abstract: A bicycle drive sprocket apparatus which allows for varying torque transmission during its rotation and for varying angular velocity of said sprocket when constant rotational force is applied thereto. The device provides for accelerating and decelerating angular velocity during predetermined sectors of the rotational cycle. Through elliptical and other non-uniform radius gear parts, said apparatus converts varying torque inputs into constant torque output. Used as an improved front sprocket for a bicycle, it provides increased resistance to the operator of said bicycle during the downward stroke of the pedal and relatively less resistance during the horizontal portion of the pedal cycle.

Abstract: A hypervelocity projectile is provided with aluminum components, such as s and windshields, which possess a coating having high resistance to thermodynamic ablation on the aluminum components. The coating is formed by first producing a "hard" anodic coating on the aluminum component by anodic oxidation of the aluminum in an acid electrolyte maintained below 10.degree. C, and sealing the hard coating with a hot aqueous solution of an alkali metal silicate of the formula Me.sub.2 O:x.SiO.sub.2, wherein Me is an alkali metal and x is at least about 2.0, e.g., a 5 - 10% aqueous solution of Na.sub.2 O:x.SiO.sub.2, wherein x is about 3.25.