Loading and structural stiffness of tandem bicycle frames

Abstract

Tandem bicycles are used for all para-cycling events for visually impaired athletes. Tandems are structurally more challenging to design than solo bicycles: they must resist higher loading over a longer wheelbase, yet must still fit between the legs of the riders. Despite this, there is limited published work on tandem design. This paper presents a method for determining maximal loading of a tandem bicycle frame in racing scenarios. The only inputs required are the dimensions of the frame and the torques exerted by the riders. Outputs are the forces acting on the frame. The method is used to provide loads for structural analyses of tandem frames of different topologies. Twisting of the frame under a starting effort is shown to be the worst load case. The “double diamond” is shown to be the most efficient tubular frame design, on a stiffness per weight basis, but is only 2% superior to an “open” topology.