The earlier studies in this measurement series defined the limits and aims for design process to create better ventilating helmets [1], and tested the insulation [2] and evaporative characteristics [3] of the designed mock-ups. In addition some of the tested mock-ups were modified to study more closely the factors that were expected to improve heat transfer from the bicycle helmets. The present paper covers making a new prototype that allowed modifications of the air channels and in- and outlet openings. In total 2 new helmet design concept mock-ups were created and tested with 13 modifications in comparison with 6 selected helmets from the previous studies including the modified versions. The mock-ups were tested at the Thermal Environment Laboratory, Lund University for insulation and evaporative resistance. Dry tests for insulation were carried on at 20 °C temperature in a wind tunnel on a thermal head manikin at the chosen air velocities of 1.6 m/s on a bald head and 1.6 m/s and 6 m/s with the wig in order to simulate the effect of hair. Wet tests were carried out with textile skin on the head manikin, using the air velocity 1.6 m/s with and without the wig. As the main result it was concluded that a well ventilating helmet is characterized by less contact with the head, and proper air channels with strategically placed air inlets and outlets. Large openings worked much better than a several small ones, yet, the care has to be taken as too large openings reduce the helmet protective capabilities. The shape and other design related modifications of the air inlets and outlets had minimal effect on ventilation.
[1]
Kalev Kuklane,et al.
User friendly bicycle helmet for commuters
,
2013
.
[2]
Ingvar Holmér,et al.
Development and validity of a universal empirical equation to predict skin surface temperature on thermal manikins
,
2010
.
[3]
I Holmér,et al.
Evaluation of evaporative heat transfer characteristics of helmets.
,
1997,
Applied human science : journal of physiological anthropology.
[4]
J D Abeysekera,et al.
Adaptation to discomfort in personal protective devices: an example with safety helmets.
,
1990,
Ergonomics.
[5]
C. P. Bogerd,et al.
Heat transfer variations of bicycle helmets
,
2006,
Journal of sports sciences.