This is my test oven, it is made from an old storm window 20"x22" the box is from cedar fence boards so it is weather resistant, I used 4 six footers at $1.30 each. The polyisocyanate insulation is left over from my solar collector but believe it to cost about $10. The tilt frame was made from one 2x4x8' and cost $2, the other lumber was scrap and on hand. This took about 3 hours to make to this point.
In the upper right corner you will notice a small nail set at the same pitch as the glass, I call it a sun dog and will tell you when the oven is tilted right at the sun. When the front to back tilt angle and east to west swivel is set perfectly parallel to the sun the shadow will disappear.
I also left the inside with the silver reflective foil the insulation came with thinking it may add in reflecting the sun to the black pot and so far has proved that. I have black aluminum sheets to slip in for more testing later. I will also test with a reflective aluminum shroud to act as a parabolic and should increase the temperature from 200F to 350F after done with these first tests.
An easy to remove pipe with pot hanging from it is necessary to keep it level as you tilt the box every hour to follow the sun. I am going to buy a cast iron dutch oven to hang in there because the heavy mass of it will help keep the temperature stable through cloudy periods. You can regulate the temperature by not following the sun and keeping it a bit off angle.
During the day and the seasons the tilt angle will vary, for me at a latitude 36 degrees it will go from almost pointing straight up to the angle of which a 6' step ladder is when opened.
From my testing so far I will get good strong sun from 10am to 5pm in summer and maybe two hours less in the winter, outside temperature makes very little difference in the ovens inside temperature as I have proven with my solar collector, though the intensity is reduced and will lower the total available heat. I have two sheets of this glass and will test accordingly to see if the the double reflective surface saves more in re-radiation as it would block.
More info and data to follow
In the upper right corner you will notice a small nail set at the same pitch as the glass, I call it a sun dog and will tell you when the oven is tilted right at the sun. When the front to back tilt angle and east to west swivel is set perfectly parallel to the sun the shadow will disappear.
I also left the inside with the silver reflective foil the insulation came with thinking it may add in reflecting the sun to the black pot and so far has proved that. I have black aluminum sheets to slip in for more testing later. I will also test with a reflective aluminum shroud to act as a parabolic and should increase the temperature from 200F to 350F after done with these first tests.
An easy to remove pipe with pot hanging from it is necessary to keep it level as you tilt the box every hour to follow the sun. I am going to buy a cast iron dutch oven to hang in there because the heavy mass of it will help keep the temperature stable through cloudy periods. You can regulate the temperature by not following the sun and keeping it a bit off angle.
During the day and the seasons the tilt angle will vary, for me at a latitude 36 degrees it will go from almost pointing straight up to the angle of which a 6' step ladder is when opened.
From my testing so far I will get good strong sun from 10am to 5pm in summer and maybe two hours less in the winter, outside temperature makes very little difference in the ovens inside temperature as I have proven with my solar collector, though the intensity is reduced and will lower the total available heat. I have two sheets of this glass and will test accordingly to see if the the double reflective surface saves more in re-radiation as it would block.
More info and data to follow
