What would you have done differently if you built this oven again?
This is probably the most asked question, and the hardest to answer. The nature of a project such as this is to learn as you build and, often, to come up with good ideas as soon as it's too late to implement them. I won't go into all of the subtle changes that I would make to the second version, but will cover the following changes which shoud improve construction time and usability once in service.
1. Purchase the elements new. Do not use salvaged elements. I used salvaged elements (free) and each one had a different mounting detail. This caused me to "re-invent the wheel" for each element, spending more time and effort than I would have had the mounting method been the same for each element.
2. Make the base in two halves. This would allow the oven to be either 3' long or 6' long. The smaller size would be great for doing wheels, swing arms, etc., while the longer size could be used for frames and long items.
Where can I buy insulation?
Several different manufacturers make the same insulation. It's a 2" thick, 3PCF, rigid, unfaced fiberglass board. I would suggest the websites marked on the Links page and search through each site for the "Where to buy" or "Find a distributor" page. Look for distributors in your local area. Some distributors may be willing to ship a bundle of the insulation to you. You'll have to call and ask if they offer this service. I don't know of any online sources at present.
Is the base of the oven insulated?
No, the base is not insulated. The bottom of the burner pans sit about 2" above floor level. Since I don't use the oven on a continuous basis, I don't think this is much of a problem as far as heat loss. If the oven is used continuously, insulating the base will be more energy efficient. Important Note: My oven is always used over a non-combustible concrete floor and therefore presents no fire hazard. If you plan to use your oven over any sort of combustible floor or floorcovering, you must insulate the base! You also should provide a thin layer of insulating material under the base since the metal of the base will conduct heat and could cause a fire hazard. I would suggest cement backerboard, used for ceramic tile substrate, as a possible material for this use. This is known as providing a "thermal break" between the different parts of the assembly, a technique widely used in aluminum windows and storefronts.
Does the oven need a circulation fan?
A low profile or horizontal format oven of small volume will probably not need a fan. The distance from the elements to the roof is small and the heat radiates well enough to heat the interior pretty evenly. As the volume increases, or if the oven is a vertical format with a larger distance from bottom to top, a fan should be considered. A fan from a convection kitchen oven would be an excellent choice, as would a fan from a downdraft cooktop. The fan from the cooktop would probably move too much volume and would require a choke to limit the volume somewhat.