In late 2016, I felt like doing something with a discarded auxiliary burner and grill from an old Coleman 425F base-camp stove. Seven years earlier, I had discarded these parts after developing my DIY robust retro stove. In particular, I wanted a two-burner Coleman stove that would take up less space on future Ghia road trips. Packing the tiny '64 Karmann Ghia for a 5-day camping trip is a challenge.
The design is fairly self-evident, and thus I won't go into great detail. Essentially, I created a primary burner out of ¾-inch copper plumbing pipe, attached the auxiliary burner, provided the two burners with legs, hooked folding legs to the grill, and provided a Coleman-stove fuel tank.
To make the primary burner tubing, I bought four parts and scrounged around in the garage for the remainder. I discovered that I could spot-weld the copper provided that I held a bead long enough in one spot to achieve penetration. Three slots were sawed near the end of the tubing, and steel screen material was wrapped around this section. Four holes were drilled around the upper section where the generator plugs in, to provide air mixing. A detachable spring pulls the fuel tank and burner together, thereby keeping the generator plugged into the burner tubing. Three-sixteenths-inch steel rod, bent and welded where needed, provided the legs for the burners and grill. Chains keep the grill legs at the proper angle.
The fuel tank has a story all its own. On a particularly long walk with Alice about a year earlier, we happened upon an abandoned burned-down house. We snuck through a gap in a temporary fence across the front. Among the debris, there was a burned-out Coleman base-camp stove. The fuel tank, I thought, might be salvageable assuming that the pump valve was working. The tank sat on the side of our house until one day when I tried the pump. The neoprene piston was toast, but I had a spare, which I swapped in, and the pump now worked, and the tank held compressed air overnight. The other controls and fittings also worked. Some external and internal cleaning and a coat of red paint (the original color) then yielded a nice, big, working, old Coleman-stove fuel tank.
Another perspective, without shielding.
Both burners engaged.
I noticed that in low-flame (simmer) mode, there was a tendency for a flame to spontaneously start in the aeration section and the flame at the burner to extinguish. The cause, evidently, was heat from the burner flame entering the aeration holes and prematurely igniting the air-fuel mixture there. My solution was to cut a shield from sheet steel and install it between the burner and aeration section and cut another cylindrical shield from a beer can and install it around the aeration section. The shielding is shown installed in the uppermost photograph.