The ADS-B new radio stack project has taken way, way longer than I expected. As you know, I've chosen to do all the work myself (under the supervision of my AME) and I realize that I move at a glacial pace (compared to the avionics techs, who do this all the time)
This stuff is really complicated. There are wires running everywhere and I'm having to learn a lot about electronic components and nomenclature.
Nevertheless, I'm enjoying the process immensely.
Once everything had been ripped out of the plane, the first step in the rebuild was to mount the trays for the new radios. This process turned out to be way easier said than done.
Initially, I figured I'd start at the bottom (with the new transponder), mount that tray and then work my way up. Dave at Eagle suggested that each tray should be separated by a minimum of 40 thousand, so I cut a couple of strips of .040 aluminum to act as spacers.
Each tray is secured by four #6 machine screws that screw into floating nut plates that are clipped on each side of the instrument panel frame. Needless to say, the hole pattern in the new Garmin trays were not the same as the old tray pattern. So new holes had to be drilled.
After fitting and marking, I used Chris' air powered, right angled drill to drill the new holes. Each hole had to be centre punched big time to prevent the drill bit from wandering, but I managed ok.
I clipped on the nut plates, slid in the tray and fastened the screws. It looked pretty good. So on to the next tray (my old Narco Mk 12D radio).
What became quickly apparent however, was the difficulty of trying to judge the how far back in the frame to mount the tray, without the two radios being in place. And if I slid the radios into the trays, it was impossible to mark the location of the holes!
So I took my best guess and drilled away. After screwing in the second tray and sliding in the radios, I was dismayed to see that the radios were about 1/8" out of alignment!! Oh, oh. Clearly my "bottom up" approach was not going to work!
After chatting with Chris, I came up with a different approach. I decided to stack all the trays (5 of them, 6 including the AirGizmos panel dock) on the bench and clipped them together using cleco clamps. I slid in all the radios and then tweaked the trays to ensure everything lined up.
I then removed the radios and clamped two aluminum stips to each side of my temporary "stack" and marked the hole locations using a fine tipped marker. Voila! I now had two perfect templates for the hole locations.
I then drilled out the holes on the drill press, mounted the templates on each side of the instrument frame with cleco clamps and drilled away using the template as a guide! This time I was confident that everything would line up properly and it did!!
All the radios slid in nicely and were perfectly lined up top to bottom. Beauty! Standing back, the whole thing looked pretty awesome. However, it was only a facade because there were no wires connecting anything yet.
So stay tuned! Installing the wiring harness is next!!
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