A Narrow-Track Tilting Tricycle With Variable Stability That the Rider Can Control Manually

Abstract

Many health, environmental, and quality-of-life benefits to cycling have been identified, including exercise, zero-emissions, reduced pavement requirements compared to cars and busses, and nearly silent operation. [1] There has also been a huge recent world-wide investment in infrastructure, including kilometers of lanes and paths, parking, bike share, and shower facilities at workplaces. [2] A significant fraction of the population, however, is unable to join in this activity with traditional upright bicycles, including people with balance or joint limitations caused by injury, disease, or age. [3] One solution to these ergonomic difficulties is the recumbent bicycle, but many riders find them difficult to balance and steer because of several factors, including centre of mass location and steering geometry. [4] Another solution, the recumbent tricycle, must have a wide axle track for lateral stability when turning, which requires more pavement and creates more aerodynamic drag than the bicycle equivalent. [4] Tilting tricycles can behave just like bicycles and so have the same handling issues or incorporate complicated and costly tilting actuation. [5][6] We present a solution that aims to combine the best attributes of all these vehicles and eliminate the drawbacks: a tilting tricycle with variable stability that the rider can control manually. By varying the centre of mass trajectory while tilting, it balances like a bicycle when going fast and so has lateral stability provided by tilting like a bicycle, and it balances like a tricycle when stopped or going slow to eliminate excessive steering burden on the rider. [7] It also requires no more pavement than a bicycle and has little more aerodynamic drag than a recumbent bicycle because of its narrow track.An additional beneficial side-effect of the variable tilting mechanism is that the seat can be higher when stable to facilitate getting in and out of it, and the seat can be lower when unstable to reduce frontal area and therefore aerodynamic drag.We present the titling linkage that implements this functionality, a mathematical model and the stability eigenvalues it produces, and confirmation of the model with a ridable physical prototype.