Chapter 22 – Triparagon Cross Shelf

Technically, I started off today by spending about 2 hours finishing up my blog & tweaking this website.

I then called Bob at TCW Technologies and had a good discussion on connecting the IBBS power cables to the 9-pin D-Sub connector that will be the new X-Bus (vs the ATC fuse panel).

I then went down to the shop, marked up the front top edge of the Triparagon cross shelf in the location where I would drill the beginning holes for the rivets that will secure the parts mounting overhang tabs.

Triparagon cross shelf marked for front overhangs

My first real action though was drilling the front & aft rivet holes on the mounting flanges that secures the cross shelf to the vertical plate.  These are the first 2 of 4 total larger diameter rivets that I’ll use to secure connect these Triparagon pieces.  I couldn’t actually press the rivets in place since I can’t get in there with my rivet pressing tool, so I’ll have to mount the rivets when I remove the vertical Triparagon plate.

Riveting cross shelf to vertical plate

I drilled the aft rivet hole first (right, above) since the cross shelf needed to come up about 0.070″ on the front side to be at 0° level, which is what the double-checked longerons showed.  After drilling the front side & inserting the rivet, I confirmed that the cross shelf was still level from front to back, matching the 0° longeron level… which you can see it did!

Cross shelf matches 0 degree longerons

I took this shot specifically to show the 6 countersunk screw positions that are used to hold the cross shelf to the vertical plate via the angled mount extrusions and nutplates. You may note in the next pic that the nice aluminum material in the areas between the pairs of countersink holes were targeted for lightening… Yes, the weight loss program continues!

Removing cross shelf plate

In the pic above you can see all the dots along the leading edge of the top cross shelf where I marked the it for the rivet drill points.  I then drilled a 1/16″ pilot hole at each dot where I would be installing a rivet.  I then I clamped each overhang piece in place, drilled the #40 hole through the cross shelf pilot holes into the overhang extrusion clamped underneath.  I then deburred all the rivet holes, and then mounted one overhang at a time.  I would drill the countersink on a rivet hole, press the rivet into place and then move onto the next rivet.  You can see all the rivets installed below, which of course means that the overhangs are mounted.  Also note there are a number of new lightening holes.  After I drilled the new lightening holes, I spent a good 20 minutes cleaning up the rough edges of the larger cross shelf lightening holes.

New lightening holes & rivets!

The overhangs have the dual purpose of providing a mounting surface for the CrackerJack parts, and also to provide a flange to mount the upcoming diagonal supports that will secure the outboard ends of the cross shelf to the upper mid-point area of the vertical plate.  You can see that I pre-identified the locations for the airspeed switches and drilled the mounting holes on the overhangs before riveting them in place.

Cross shelf front overhangs - action shot

Here’s a shot of the overhang rivets . . .

Cross shelf overhangs rivets

And a shot of the entire Triparagon cross shelf . . . in repose!  ha!  I weighed the cross shelf with its attached brackets, and with the new lightening holes it weighs in at 0.476 lbs. Add that to 0.7 lbs of the vertical upright (which will get another round of lightening holes) and I get a respectable 1.176 lbs total currently.  Again, I suspect that I’ll come in at about 1.1 lbs for final Triparagon install weight.

Cross shelf front overhangs

I then mocked up and test mounted my Crackerjack parts, aka airspeed switches, onto the front overhang mounting tabs.  Note that airspeed #1 is mounted on the right side (left in the pic) on the aft side of the overhang tab staggered behind and just to the left (looking from front) of airspeed switch #2.  I mounted airspeed #1 to allow me to adjust the target airspeed set point with the setscrew.

Airspeed switches test mounted

I then spent a good couple of hours updating my IBBS wiring diagram and determining the pinouts for my PQD (Panel Quick Disconnect) connectors.

Tomorrow I’ll continue working on the Triparagon and the avionics bay electrical wiring stuff.  I figure I have at least another good week to finalize this round of electrical system stuff before moving on to the wheel pants!


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