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Engineering Innovators Without Borders
Human Powered Grain Crusher Justification: A bicycle-powered grain crusher would be useful in many rural parts of the world where the conversion of grain to flour is often made difficult because of the lack of electricity for motorized grain crushers. Design: When the project commenced, it was decided that the most reasonable device to fulfill the purposes of this project would be the quern, which is essentially two circular stones, one on top of the other, with an axle in the center and a handle attached to the top stone. The grain to be ground is placed between the two stones and the top stone is rotated about the axle. On more advanced designs, a small hole in the top stone allows for the continual introduction of fresh grain into the space between the stones. The quern was constructed using circular cement "paver" stones and a steel rod as an axle. It was tested by grinding various types of grains and proved to be adequate as a working model. Having realized that the technology of the quern would not allow for improvements beyond what already existed, the focus of the project shifted to developing improved methods to power an existing grinder. During the research, some previous designs with similar project goals were found. Designs included bicycles or stationary bicycles modified with a chain or drive belt used to turn a crank on a personal, kitchen type grinder. The development team decided that a bicycle stand for an existing bicycle would be the best idea for the scope of the project. A bicycle stand was constructed with intentions to be attached to a pre existing grinder. Of critical importance to the design was a wide range of adjustability so that the final product could fit a variety of bicycles. The stand would need to fit bikes with tire diameters ranging from 20" to 26", and also with varying rear axle widths. The design also had to allow for adjustment of the tension in the drive belt, so it was decided that the grain crusher's location would be adjustable to provide such tension. The only fixed components would be the center drive axle and its supports. An overview of the previous design is shown below. An
effort was also made to use as many off-the-shelf components as possible.
This would limit machining time. National Recognition
TIMELINE of DESIGN
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