Click on the little picture to see it larger.
The problem is that during summer duty, the shelter (box) hatch (rear door) gets opened and shut repeatedly, letting the cold air out. Furthermore, measurements were made indicating that when it is 100 degrees outside with sunshine, the shelter's outer skin is 120 degrees. With the 8000BTU unit running, the interior skin is 100 degrees and the interior air temperature is 78 degrees. This would be acceptable if the hatch were seldom opened, but the usual situation prevents that, and we end up with about 85 degrees. At that temperature, the radio gear begins to get uncomfortable, especially under heavy use. It also adds heat to the shelter. The total heat load to the interior due to electronics is about 800 to 1400 watts.
Details of the construction are shown here. I had never done anything like this before, so I took the first goal to be strength and safety for this heavy unit. A hasty spray with some brown paint took the bling (shiny metal) out of the equation. It wil be properly painted later. First, the upright supports were put in place, then the bottom tray was assembled. Finally, the diagonal supports were put in place. Careful measurements of the condensing unit width allow a snug fit in the tray. Be sure to account for the thickness of the heads of the bolts which hold the tray and bracket together. This was about 1/4". A Milwaukee "sawzall" was used to cut the metal. The hardest part of the job was putting the 65 LB condensing unit on my shoulder and carrying it up the extension ladder to the roof of the truck.
Here is another picture of the underside which may clear up some details. Once the job is completed, the protrding angles will be sawed off flush with the bracket and tray assembly for a neat job.
Here is what it looks like on the truck so far. Once the copper tubing is soldered in place and the electrical wiring run, the condensing unit will be bolted int place with 1/4" lag bolts through its thisck bottom plate, and some #12 sheet metal screws through the sides. Care will be taken to avoid the coils, plumbing, and compressor! Lockwashers are always used in these applications to keep the scres and bolts from getting loose. In any case, proper PMCS requires them to be checked periodically.