Electrical/Panel « Matt's RV-7 Project

Archive for the ‘Electrical/Panel’ Category

Transponder antenna doubler

Sunday, July 26th, 2009

I bent a doubler for the transponder antenna out of 0.050" alclad and drilled a bunch holes for rivets and mounting studs and antenna connectors through it:

Then I crawled into the fuselage and match-drilled the doubler to the belly skin and the F-729 bellcrank rib, about a foot behind the baggage bulkhead. In terms of the length of coax needed to reach this location, I'm right at the limit of what the Garmin install manual allows, but I couldn't find a better place to put it. Not to mention, I hope the transponder-rays won't do anything weird to the pitch servo. Also, I shortened the doubler slightly between these two pictures, since I'm thinking about moving the ELT back here and I wanted to be sure to leave plenty of room.

A view from the outside. I need to deburr, dimple, and alodine the mating surfaces, and then see if I can coax Mary into helping with the riveting duties.

Posted in Electrical/Panel, Fuselage |

Marker beacon adapter

Sunday, July 26th, 2009

For whatever reason, designers of audio panels with marker beacon receivers in them never seem to do the obvious and put a BNC connector on the back (as you'd find with a comm radio, GPS, etc). That means you have to fabricate an adapter to go from the antenna coax to the D-sub pins on the back of the audio panel:

Here's a closer look… the center conductor is spliced to a 22 AWG wire, and another one is soldered to the shield. A female BNC connector is crimped onto the other end, and then I put heatshrink over the joint. What makes it a little harder is that the butt splice can't withstand the heat used to shrink the solder sleeve (ask me how I found out) so the order of operations gets a little fiddly.

I haven't run any antenna coax yet, of course, but this is just one more little item on my to-do list.

Posted in Electrical/Panel |

Flap motor wiring

Sunday, July 19th, 2009

Since I had one of the required components in hand already, I decided to also work on the flap motor and associated wiring this weekend. Here I've mounted the flap positioning system control box on the new backrest brace:

Here's another view to show how it stands off from the underlying rivets, thanks to a few nylon washers. That dimpled hole in the foreground is for mounting an adel clamp.

As I previously threatened, I cut the wire harness between the control box and position sensor and crimped on some connectors. Now the motor and control box don't have to both come out of the fuselage at the same time.

Since the flap motor is now no longer permanently tethered to anything else, I couldn't think of a reason not to (semi) permanently attach it to the flap actuator channel. This photo is proof that I did put the cotter pin in:

Then I spent several hours running wires to the flap switch and pulling wires back to the flap motor. Properly bundling and securing new wires takes me about ten minutes per linear foot per wire (longer if I have to drill new grommet holes or install new clamps or tie wrap anchors) so consequently this took all afternoon. I left the flap switch hanging from the panel for now, since there's no need to go to the trouble of bolting it in place for an electrical test.

Once I had all the connectors installed, I plugged it in and gave it a floor run… it works! Bump the switch, and the flaps move one notch up or down. Nice. I'll clean up the wires in a future work session.

Posted in Electrical/Panel, Flaps, Fuselage |

Wiring

Sunday, July 5th, 2009

Lots of wiring but not very many pictures today. I ran the power and potentiometer wires to the dimmer unit, and connected the Garmin avionics (all seven boxes!) to one of the analog outputs. I do not like these little screw connectors… give me a D-sub and a bag of gold crimp pins any day.

I also hooked up the CO detector, and verified it's alive by listening to the annunciator light output pulsing my continuity detector when I pulled the test pin to ground. If you're not an engineer, don't worry if that sentence made no sense, just nod and keep reading.

Here's another "look at all these crazy wires!" picture:

Posted in Electrical/Panel |

Wiring

Sunday, June 28th, 2009

Spent the whole day running wires. Not much worth photographing other than the occasional "look at all these crazy wires!" picture.

The main transverse wire bundle is getting pretty fat (average human thumb shown for reference).

Posted in Electrical/Panel |