The Solar Forge

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The Solar Forge is comprised of a large parabola section reflector, a carriage, and a target. The parabola concentrates sunlight, the carriage allows the parabola to track the sun, and the target makes the resulting heat available for a practical purpose. The Solar Forge concentrates enough power to be useful for small commercial processes in sunny climes, particularly in developing nations.


In developing nations the Solar Forge can be used as a small industrial power source to forge recycled metal. As it happens, it is impossible to manufacture the springs or drive shaft of any car out of bad steel. It is a shame to let such good material be mixed in with scrap iron and not forge it into the tools that people really need. Craft items made with the Solar Forge can be sold with the claim, "Forged by the Sun," which will give them good market value in developed countries. The target can also double as a food cooker and hot water source.


The parabola is the size of the floor of a two-car garage and is attached to the carriage by a simple hinge. To track the sun, the parabola section is rolled in a circle around the target and tipped over with a small block and tackle. The target stays in one place, making it much easier to use the heat. All the sunlight falling on the 74-square foot collection area is focused to less than one square foot in the target. On a sunny day a forge this size will continuously put about 7.0 kilowatts of heat on the target.
The parabola is built like a boat haul and covered with the shiniest material available, usually pieces of glass mirror. The carriage is fashioned from an old pickup truck, while the target is assembled from old car parts. There is also a sun tracker, made from one lens and plastic pipe.

Elegance of the Design

The Solar Forge is designed using only a compass and straightedge. The process can be taught easily and does not even require two numbers to be multiplied together. This makes the forge very easy to adapt to local conditions, materials, and purposes.
This design process is called lofting and was used to design the great sailing ships of old. You simply layout the design on a large flat surface, such as sheets of plywood. You can then swiftly draw the curves for the parabola in only a few minutes and then use this full-sized curve to make patterns for all the other parts.


The practical application of solar energy is critical in arid regions. It is particularly valuable where the collection of firewood has decimated the environment.
State of the Project
Three prototypes have been successfully built in the USA. It is now time to build a full scale unit in a developing nation. For more information see:

Solar Forge


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  • Name:
    Tom Riley
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    The needs of the American people in the 21st century
  • Hardware used for this entry:
    compass and straightedge
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