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HELMETS |
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Project Driver:The new helmets used by afghan deminers are far lighter and more comfortable than the previous models. However, they can still be very uncomfortable to wear for extended periods, especially in hot weather. Hot, humid, stale air is trapped underneath the helmet, which acts as a insulator to keep the heat in. A small fan could expel the hot air and replace it with cooler, drier air from outside. This would increase the evaporation of the deminer´s perspiration and make them much cooler and hence more comfortable. If the deminer is more comfortable they suffer less fatigue, leading to an increase in productivity and less accidents. Design:The helmet ventilation device had to incorporate a small, low maintenance, lightweight fan with a long battery/power source life. An earlier prototype incorporated a 12Volt fan, which requires a large, heavy battery to provide a usable run-time. The next prototype was based around a solar powered motor. Unfortunately the solar panel did not provide usable power except in the brightest sunlight. The same motor was then used with a single 1.5Volt battery. A single AA carbon cell provides over 10 hours of run-time for the motor at a noticeably higher speed than the solar cell could provide under the best conditions. This is the basis of the current design. The fan is mounted inside a piece of plastic tubing to protect it and control the airflow. This tubing is fixed into a hole cut in the back of the helmet. By placing the fan at the back of the helmet it is protected from damage by the brim of the helmet and is at the highest point when the deminer is working – allowing the best possible heat extraction. Performance:The ventilation fan is currently undergoing field-testing in Pakistan where deminers will evaluate its performance under operational usage. Through the development we found that it did generate a noticeable cooling effect for the wearer. An added bonus is that the cooler, drier air moving past the visor reduces fogging and greatly improves the cooling effect by increasing evaporation from the deminer´s face.
These photographs show the battery powered unit being worn - it is discreet and adds only a few grammes to the helmet weight and about US$10 to the cost. No volume production has been attempted however. (left, right full size pictures) Copyright reserved © 1998 UWA Demining Project
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