Reading on the internet, it becomes clear that many aid agencies import solar cookers into Africa and sell them to the people at a subsidized price. The thinking is to save effort and energy and resources by using solar cookers in place of wood fires. This should also help prevent desertification and reduce incidence of diseases due to smoke inhalation.

Research shows that deep trough parabolic solar cookers are among the best, they focus the heat evenly round the food, and have the focus inside the parabola so it is hard to injure your eyes. Solar cookers are either made to high specifications with fine materials in other countries and imported or made to a template from cruder imported materials in the poor country.

A problem with parabolic solar cookers is that they are harder to make than inferior types. Generally people do the math first, calculate the size of the parabola and then make up a template (usually from metal or wood). The template is then used almost as a mould for the parabola. But look at the chain of production there! Mathematician, fine woodworker or metal worker, perhaps someone else to put the reflective coat on and then selling the product to the end user! Pretty technologically advanced, I would say! Certainly not a chain that you can easily find in a poverty stricken agrarian society or a shanty town.

Why not use the skills and tools available at ground zero instead? People in poor countries have been building mud huts and doing daub and wattle construction for thousands of years! All they really need is a simple device to trace out a parabola as they build, and they can build the parabola's themselves! Perhaps even as part of their houses as they are built! Then all the outside material that they need will be the reflective material and perhaps pots for cooking!

Here is a picture of my first ever mechanical mathematician! This was made from an old curtain rod, a waste T-pipe joiner, some pieces of wood, a metal leg for an office desk, a piece of string and the bottom of an old office chair. (Not your typical 3rd world items, to be sure!)

Using this mechanical mathematician as the guide, I made the parabola in the picture below. It is a large parabola almost 4 ft by 4 ft and the focal length is about 15 inches. The parabola is made from cob (a straw, clay, sand mix.)

When I had formed the cob sufficiently, I stuck the reflective material (ordinary kitchen foil) directly to the cob!

No glue was used! I have used this cob parabola in the past couple of weeks and it has performed well.

I have also used a different mechanical mathematician to construct cardboard parabolic solar cookers.

This one is much simpler (different materials but same design) and using it, I constructed a cardboard panel solar cooker.

Once again, the mechanical mathematician made the parabola possible!

Normally lines and folds in a cardboard box makes the solar cooker more difficult to construct but the mechanical mathematician uses them as the fold lines between panels! This means that any piece of cardboard has the potential to be the backing for a solar cooker! No need to stick to one particular template if you get a container load of assorted waste cardboard boxes! The mechanical mathematician means you can use each and every box to make a slightly different but functional Parabola! and the cuts in the boxes can all be used in the design.

So, there you have it, the mechanical mathematician can help people use local material and also help them use varied unsorted foreign material too!

How to make the Mathematician

The Mathematician consists of a central post, a slider bar coming off the post at right angles, a rod coming down through the slider bar at right angles and a piece of string! As you move the slider bar closer to the middle, the rod drops down and keeps the string in tension.

The bottom tip of the rod follows a parabolic curve.

So now you have a very simple device to guide people in making good parabolic basins for making solar ovens!

The central post could be pointed at the sun at construction stage to make the correct parabola in place with the focus correct.

In the animation, the focus is at the 8 inch mark. tie it to a different hook and it will be a different focal length.

That's quicker than a real mathematician too! I believe this type of simple device will help a lot of people to improve their lives.