Role of the visor in forced convective heat loss with bicycle helmets

Twenty-six bicycle helmets and the visors supplied with them were characterized for convective heat loss using a thermal manikin headform in a climate chamber, in order to assess the role of the visors in forced convection. Two head tilt angles were studied (vertical or 0 degrees, and forward or 30 degrees), with and without the visor supplied with each helmet. Large variations were found for several helmets, with the strongest visor-induced changes corresponding to approximately 5% in the face and 10% in the scalp. When the visor visually blocked the face or the front vents from the wind direction, such as at 30 degrees, for the face, a reduction in convection heat loss was usually observed, whereas the visor had no or a slightly negative effect on the face at 0 degrees, with opposite trends for the scalp. Hence visor design can help to optimize thermal comfort via convective heat loss. Relevance to industry: Understanding (forced convective) heat loss of bicycle helmets and the role of the visor is necessary for optimization of thermal comfort. In turn this is likely to increase the willingness to wear such protective helmets, and may contribute to the performance of the wearer. (C) 2008 Elsevier B.V. All rights reserved.