Sergio Daniel Roa

Los Andes University (Colombia) | UNIANDES · Department of Mechanical Engineering

The estimation of aerodynamic drag in cycling through road tests has the advantage of considering actual cycling conditions. The main drawback is that its accuracy depends on factors of the testing scenario as the wind speed (vw) and the road grade (θ). For that reason, the effect of vw and θ on the estimation of drag area (CDA) was studied. Numeri...

The basic Whipple-Carvallo bicycle model for the study of stability takes into account only geometric and mass properties. Analytical bicycle models of increasing complexity are now available, they consider frame compliance, tire properties, and rider posture. From the point of view of the designer, it is important to know if geometric and mass pro...

Stability of bicycles has been studied by using models that assume both a rider with hands-off and hands-on the handlebars. Some authors have presented a general comparison between the behavior of the modes of vibration which affect stability in the two configurations; nonetheless, a systematic analysis of the influence of several parameters on eac...

The uphill time-trial is a cycling race in which there is at least one mountain pass or a combination of low and high gradient sections. Usually, climbing cyclists achieve good results in uphill time-trials; however, in addition to the cyclist’s ability, the race strategy is also important for achieving good results. As part of the race strategy, t...

La cronoescalada es un tipo de competencia de contrarreloj en bicicleta que se caracteriza por tenerun ascenso de montaña o una mezcla de secciones planas y ascensos. En este tipo de competencia sesuelen destacar los ciclistas con gran habilidad de ascenso. Sin embargo, adicional a la habilidad deldeportista, la estrategia de carrera también es dec...

In recent years the Whipple Carvallo Bicycle Model has been extended to analyse high speed stability of bicycles. Various researchers have developed models taking into account the effects of front frame compliance and tyre properties, nonetheless, a systematic analysis has not been yet carried out. This paper aims at analysing parametrically the in...

In uphill time-trial cycling races, riders have to travel along routes characterized by high-gradient variations in the shortest time possible. Due to this gradient variation, the appropriate selection among time-trial bicycles and traditional road bicycles is essential to reduce the power demand. For some uphill courses, the bicycle selection is n...

Different models for cycling power prediction have been presented and validated by different authors. The model validation processes have been performed in laboratory tests and field experimental tests. In field tests, different methods have been used, and in recent years, cycle-mounted power meters have been widely used for model validation and bi...

There is a tradeoff between power delivery and aerodynamic drag force when cyclists ride at different altitudes. The result is particular to the characteristics of the bicycle as well as the aerobic fitness of the cyclist. This work proposes a methodology based on an integrated approach to the study of the influence of altitude on power output and...

The effect on stability of mass, geometric and stiffness parameters of a bicycle with compliant frame, fork and wheel is studied. Critical stiffnesses of the structural elements are identified by means of specific experimental tests based on modal analysis and static stiffness measurement. Numerical stability analysis is carried out by means of a M...

Some studies of bicycle dynamics have applied the Whipple Carvallo bicycle model (WCBM) for the stability analysis. The WCBM is limited, since structural elements are assumed to be rigid bodies. In this paper, the WCBM is extended to include the front assembly lateral compliance, and analysis focuses on the study of the open loop stability of a ben...

Aerodynamic drag is the main opposing force that a cyclist has to overcome when cycling on level ground at moderate-to-high speeds. Therefore, the aerodynamic study of the bike-cyclist set has been identified as a key factor for the analysis and improvement of performance. Although there are many reference aerodynamic studies, for the specific anal...

During the individual time-trial competitions in cycling, the cyclist’s skills are essential, but it is also important the race strategy. The race strategy includes the manner in which the cyclist competes and the selection and set-up of the cycling equipment. For hilly time-trials, part of the race strategy consists of the right selection of the b...

Multiple parameters affect energy cost and comfort during cycling, and for some of them there is a trade-off between both phenomena. The aim of this paper is to present a methodology to evaluate the influence of different cycling conditions on energy cost and cyclist’s comfort. The proposed methodology is based on on-road tests where power on pedal...

This work presents a methodology for the evaluation of energy cost on cycling through on-road tests. The proposed methodology consists on the measurement of the power delivered by the cyclist on the pedals when riding on a real circuit. The aim of the methodology is to generate indexes for the direct evaluation of the effect on energy cost generate...

For the achievement of an efficient powertrain design of a hybrid electric off-road vehicle, various designs and configurations of the gearboxes were evaluated under an optimal design viewpoint. Due to off-road requirements, it is not possible to use a single fixed gearbox. Design solutions are evaluated according to specific requirements and const...

This paper presents the conceptual design of a hybrid electric off-road vehicle. The vehicle is intended to be used in Colombia (South America) where the topographical conditions require special considerations for the design of the critical systems. A study and preliminary design of the power supply system, the suspension and the powertrain are pre...