Dual Purpose Reflector Cooker

This isn't really a backpacking stove, but a fun thing to have if motor-camping, sailing or just in the garden.

This particular cooker was inspired by a type of Solar cooker called the “Sausage Sizzler” shown on the BBC program “Science Shack”.

This is a very simple parabolic cooker since the parabola is only curved in one direction because it is designed to cook long thin foods, such as (surprise!) sausages.

It suddenly occurred to me that this reminded me of another cooking device, the fireside reflector oven. Why not create a device that can cook both by the fire or by the sun, and can cook more than just sausages?

The formulae for a parabola is

where a is the position of the focus vertically from the base of the parabola. The data points below use a=5 cm and generate a curve that fits neatly in a 40 by 20 cm box. By using the formulae above and a pocket calculator you can generate a larger or smaller parabola with a different focal point.

Unlike the Sausage Sizzler, this cooker will need to withstand strong heat when used by the fire, so don't use cardboard!

You'll need two side pieces, about 40 x 25cm each, and a sheet of thin polished aluminium, 70cm long and at least 25cm across.

Take a piece of centimetre squared graph paper and plot out the above figures, or those that you have selected. Then cut along the curve to construct a template. Use this to draw a curve on each of the side pieces.

How you decide to attach the reflector to the sides is up to you, depending on what you have available. You can cut slots along the curve, and have tabs on the reflector that insert into these and bend over, or you can position “L” shaped brackets along the curve and pop-rivet these to the reflector.

You can also add a back, top and bottom to the sides to strengthen the assembly and to create an insulating airspace behind the parabola.

Only job left is to add the cooking supports. On the original Sausage Sizzler a skewer was pushed across at the focal point, which for the above figures is 5cm in front of y=0 (point "5, 0" in Cartesian co-ordinates). I suggest you also make a hole a "3, 0" and "7, 0" too. Infact you may choose to make these two holes a centimetre or two lower. Pass a skewer or similar piece of stiff wire through the 7 and 3 holes. These skewers are the tray supports, and placing them a bit lower places the food in the focal point.

A little wrinkle here is to cut a vertical channel from "5, 0" to "5, 2", then make a horizontal cut from the front edge of the side to this point. The reason for this will become clearer later.

Next you need to get a piece of metal about 6cm across and short enough to rest across the skewers. Measure about a centimetre in from the long sides and bend one edge down and the other in the opposite direction. This constructs a little tray that rests over the two skewers. Ideally this should be dark rather than reflective since you want it to absorb the light directed onto it and heat up. You can paint the bottom with a heat-resistant black paint, but the upper surface should be safe to put food on. Traditional reflector ovens usually had a larger tray with sides to catch the juices for making gravy.

How to Use

Face the reflector into the sun, or place it beside a fire. You don't need to wait for the fire to die down to coals before you start cooking. If you have an open fireplace at home you can use the reflector indoors as well as out.

Food will cook quicker if it is cut into small pieces, though this is true of most cooking.

The reflector is a device for baking or roasting, it's not the sort of cooker that you could use to heat up a billy full of water (unless you had a very long thin billy!). If cooking by a fire there's no reason why you can't hang a billy over the same fire you place the reflector before.

You have several options with respect to how you cook your food. The original method is to thread the food onto the skewer at the focal point. Sausages are an obvious one here, but you can also use it to cook twister bread or cook anything that you can cook on a kebab –cubes of meat, fish, peppers, onions, tomatoes, mushrooms etc. Dust the outside of the meat with flour to absorb the juices. The slot we cut earlier allows you to remove or replace the skewer without needing to cut the food off.

The tray you constructed can also be placed on the two other skewers, and food placed on this. Some foods can be placed on top of the skewers without bothering about the tray.

While writing this it occurs to me that there may be other uses for a reflector.

An obvious one is to use it as a heliograph, either for emergency signalling or long distance communication. A friend of mine says that if he was adrift on a boat he'd direct his reflector towards a rescue helicopter's searchlight. A fireless cooker like the reflector would be quite a useful thing to have on a yacht.

A reflector could also be placed behind a broken down vehicle at night to warn other road users. This will be particularly effective if used in conjunction with a road flare.

By the Author of the Scrapboard : Blog of the Books.
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