A solar cone grill is designed out of cones.
It seems to me that the Solar Cone Grill is easier to construct than the Solar Grill made out of sectors. In a solar cone grill, each cone can be cut out from a metal plate as each cone is a segment of a cirle with a given diameter. Each cone form a part of a parabolic shape heating excactly the same spot. The spot heated is depending on the size of the cones.
I am here adding a new element on this type of design with four cones. One of these models is almost identical to the Earth Bound Cooker. I have just added a new cone on the top of the third cone. The other model is four cones up to 45 degree. This gives a solar grill that is more powerful than one with 3 cones. The focal pont or more right the focal sphere is here 10 cm diameter.
There are benefits to this. One idea is to focus the sun evenly on a sphere, not a point. Even with a big reflector the sphere could be just as big or small as you liked. By adding more cones to the 90-45 degrees area the solar grill would become bigger, but without loosing the focus zone.
Check also out Earth Bound Cookers fromhttp://solarcooking.wikia.com/wiki/EarthBound_Cooker.
A five cones solar grill would look like this:
