Table of Contents

Materials and Structure





The diagram shows the main structural components of a conventional bicycle frame. Normally the material used is a steel, however aluminum alloys are also used with this same geometry and at least one composite bike follows a similar configuration. The frame geometry is almost two triangles but the head tube makes the front section a quadrilateral. The joints in such a frame are rigid and can, therefore, transmit torques as well as tensile and compressive forces. Even with pin joints the triangular rear section would be stable and its component tubes would be either in tension or compression and experience no bending moments. With pinned joints the front section would be unstable and the tubes could rotate through wide angles within the plane. For this component the welded or brazed joints are required for stability.

In normal use the materials are expected to stay in their elastic range so that applied stresses must be below the yield stress of the material. Toughness is also a desirable property so that the components will bend rather than fracture if they are overloaded.

From: McMahon and Graham:
"The Bicycle and the Walkman," Merion (1992)