Simultaneous assessment of thermal comfort and aerodynamic drag of cycling helmets as a function of ventilation hole configuration

Although the main aim of cycling helmets is to protect cyclists from injury, the ideal cycling helmet minimizes aerodynamic drag and also allows rapid heat loss from the head to prevent overheating. This study takes the methods developed by Underwood et al., in which an aero helmet with reconfigurable ventilation holes was mounted on a heated mannequin head in a wind tunnel at 16.7 m/s (60 km/h) at a single angle and applies them to a range of angles representative of realistic riding positions. Thermal measurements were area weighted to provide a heat map of temperature variations over the head at different angles. Four helmet hole configurations were chosen for this study: no holes open, all holes open, front holes open and middle holes open. The results showed that the head angle had a stronger effect on drag than hole configuration. As expected, having all holes open had the greatest heat loss at any angle, but the lowest drag was found when the middle holes were open at head angles of 0 degrees and 20 degrees (at 0 degrees the neck is vertical) and all holes closed at head angles of 40 degrees and 60 degrees. The results indicate that a good venting geometry, combined with an efficient aerodynamic shape could provide an optimized helmet.