In this paper, design of a recumbent bicycle for loading cargo is introduced as an application example of practical engineering. This device consists of a main frame due to the main load, an occupant seat considering the human body structural condition, a steering device(handle), a power transmission device (gear/chain, pedal, and crank), and a braking device (disk brake). In order to design and manufacture of the device, various subjects learned during the school year are reviewed and practiced. In particular, by designing the shape considering the load acting on the recumbent and the structural conditions of the human body, it is possible to understand the detailed mechanical mechanism as well as the understanding for the basic design. Through this case study, students can develop and enhance their creativity and practical skills for related industries by designing and manufacturing a real recumbent bike and, if necessary, industrializing these skills.

This article deals with the transient analysis in bicycle shifting using a discrete chain model. Among the various components of a bicycle, we focused in the power-transmissions on the contact points between the chain element and sprocket. And by imposing kinematic motions on the front and rear derailleurs, we analyzed the shifting mechanism for increasing the rotational speed of rear wheel. In order to build the dynamic analysis model, we first tore down the real bicycle and measured each component's design parameters. Then we made 3-dimensional CAD models for each component related to the power transmission of a bicycle. Using the converted 3-dimensional dynamic model for the simulation program, we performed non-shifting and shifting dynamic analysis. As a result, we investigated the dynamic behaviors of a discrete chain model focused on the interaction between the chain and sprocket wheel.