Analysis and Design of a Class of Cam Profile --as Applied to Compound Archery Bow

摘要

Compound bow was invented in Missouri in 1969.The main advantage of this type of bow is the so-called let-off property,which is determined by profiles of one or more cams.Available literature used empirical methods to determine the cam profdes.This paper proposes an analytical approach to determine the relationship among draw-force,spring force,and cam profile.Results from study demonstrated while mechanical advantage is decreasing when the bow is drawn,the cam profile can transfer tension forces between main and secondary strings,making draw-force smaller.The combined effect produced the so-called let-off property.With this working principle analytically explained,optimal design tools such as calculus of variations can be applied to optimize the cam profile design.The goal will be limiting the maximum draw-force while maximizing the total energy stored in the bow limbs,achieving largest possible arrow velocity.