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Archive for the ‘Firewall Forward’ Category

More Wiring – 8 hrs

November 9, 2013 Leave a comment

Saturday Nov 9, 2013

I admit I am slow at this. It takes me hours to arrange and make these electrical connections because I don’t want to create a rats nest of wires. All the details have to be determined as I go – such as the routing of the wires, tie down locations, and most importantly the wire length. Today I connected all the wires for the EGT and CHT sensors for cylinders 1 and 3. This photo is the fruit of about 4 hours of work.

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I next made two 26 AWG fusible links from a kit I bought from B&C Specialty. These are for the ammeter shunt.

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Here is a photo showing the wires for the ammeter shunt installed including the two fusible links. I also wired the master switch to the battery contactor. I confirmed that the contactor closes when the switch is thrown. That is the first test of the power circuits.

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Categories: Firewall Forward, Wiring

EGT and CHT Wiring, Annunciators – 9 hrs

September 8, 2013 Leave a comment

Sunday Sep 8, 2013

I been moving more into the electrical wiring work this weekend. For the audio panel I did a test installation of the connector backplate onto the tray to determine how this goes together. The instructions in the PSEngineering installation guide are rather limited.

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Next I assembled the second annunciator controller module and tested it. This one is wired to sense two circuits going to ground and two circuits going high to 12V. Everything checked out as expected so these are ready to be installed in the airplane.

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The next adventure was cutting and terminating the exhaust gas temperature (EGT) and cylinder head temperature (CHT) sensor leads between the engine and the engine monitoring system (EMS). I hoped this would be straightforward but I stumbled upon some posts on VAF and the Dynon forum about problems with erratic EGT readings and bad crimps seem to be the cause. On further investigation I learned that the thermocouple wire used in these leads is a hard metal and does not crimp well to typical copper terminals. So at least I was alert to the issue. I started by doing a sample crimp on a short piece of scrap wire and sure enough it pulled off when I did a pull test. The EGT wire is seven strands and the gauge is a little small for a 18-22 AWG terminal. So I tried again by stripping the wire twice as long and folding the wire back on itself to double the area inside the crimp. That was too large and would not go into the barrel so I cut three of the seven strands at the mid point of the fold so it effectively had 11 stands in the crimp area. That fit into the terminal barrel and produced a good crimp that passed the pull test. I did not measure the force but I pulled on it pretty hard.

For the CHT wires the strands seem to be slightly finer and the wire would fit into the barrel folded back double without trimming any strands. That too produced a strong crimp.

After experimenting to get this solution I was able to terminate all the EGT and CHT leads on the left side (cylinders 2 and 4). I cut pieces of shrink sleeving to go over each mating pair of Faston connectors but have not shrunk them because I may install some fireproof expandable sleeving over this bundle later. The routing I chose provides plenty of slack for the relative motion of the engine without getting too extreme.

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Here is a better view that shows how I spread the terminations out to avoid a big bulge in one region. The Dynon instructions recommend against trimming any of the armored sections of the cables so I did one loop back on the EGT4 cable to keep the terminals in a reasonable region. Otherwise they would have been up inside the firewall pass-through and I was not going with that.

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With all the wiring planning I have been doing I was able to get a list of the wires and sizes that route through the fuselage center section. The holes to pass wires through the center section is limited to four snap bushings about .450 diameter each and one of those is filled by the elevator trim cable. When I saw the full list of wires that have to get through there it was clear they were not going to fit with the two pitot hoses (pitot and static) that need to go to the Gemini PFD. So I decided to reroute the pitot hoses under the canopy sills to make more room for wires. This picture shows the static line (white) rerouted from behind the baggage compartment beneath the main longerons through a hole I added to the F-706 bulkhead (as a contingency) when I originally built it.

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The hose comes out behind the fresh air inlet  behind the panel which is perfect for routing to the Gemini. I did the same thing on the left side with the green pitot hose. I still need to add a few tie bases to tidy up the routing but I think this will help the wire routing problems considerably.

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Categories: Avionics, Engine Sensors

Electrical Planning – 9 hrs

August 25, 2013 1 comment

Sunday Aug 25, 2013

Most of my time this weekend was again spent on electrical planning. I now have 20 separate schematics for the different major subsystems of the airplane such as main power backbone, ignition, VP-X wiring, transponder, autopilot, etc. It was just way too confusing to try to put those all on one schematic so I did it in modules. They are pretty close to done now. I am just cross checking everything and looking for errors. From that I compiled a list of materials I need such as wire, connectors, switches, and terminals. I was stunned when I added it all up and it came to almost $500 worth of new materials? The RG-400 coax and connectors alone total over $80.

After almost a full day of this I was aching to make something with my hands so I took a break from the electrical planning and worked on a couple of small hardware projects. One thing on my to-do list has been to install a quick release detent catch on the copilot control stick. A lot of builders do this for the wife so the stick can be removed for more comfort on long cross country runs. I bought the detent spring from McMaster Carr (P/N 92988A650). In fact I had to buy a bag of five so I have four left over and will gladly mail one to anyone who needs one. All it takes is a 1/4 inch hole drilled through the stick tube and receiver fitting. The detent spring just pops in. I put some heat shrink tubing on the spring before installing it to prevent chaffing on the electrical wires that will run through the tube for the copilot radio button. This view shows the detent spring installed in the tube.

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And this photo shows the tube inserted and the detent snapped into place. It is quite solid.

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I also fabbed a shield for the canopy release switch. I was worried that the microswitch could get damaged by a passenger getting in or out because it was somewhat exposed at the passenger’s right shoulder and that little lever on the switch is quite delicate. The cover is .032 alclad aluminum and it is attached by the same two screws that hold the switch plate to the latch. This photo shows it installed with the seat back pulled forward.

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You can see in this next photo with the seat back in the normal position and the latch open that the switch would be more exposed without the cover. No doubt it will be even better with the seat cushions installed.

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I also mounted the prop (maybe for the final time) and installed the spinner with my newly custom made gap fillers. You can see how nicely they fit in this view. Yes, you can only see one because the other two are on the far side but they all look virtually identical.

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Categories: Canopy Latch Fingers, Prop

Finished Prop Gap Fillers – 3 hrs

August 17, 2013 Leave a comment

Friday Aug 16, 2013

This post summarizes the work over several evenings to finish the prop gap fillers I made for my Catto 3-blade prop. Here is a view of one of the three gap fillers. I applied a layer of epoxy with microlight filler to each part and sanded them out flat to hide the rivets and make the surface flush with the spinner. Then I applied a good thick layer of UV Smooth Prime.

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Categories: Prop

Installed ADSB Module, Making Prop Gap Fillers – 11 hrs

August 11, 2013 Leave a comment

Sunday Aug 11, 2013

My friend Scott came over on Saturday to help me install the Dynon ADSB module. I decided to mount it behind the baggage compartment using a modified Vans ELT/strobe mounting bracket. I ordered that kit a few months ago so we pulled it out and I climbed into the baggage compartment to match drill it to the J-stringers. It would have been a lot easier to install this thing before I closed out the aft fuselage. It was uncomfortable but we got it done including spraying a coat of primer on the bracket before riveting it to the stringers. The only modification I made was to install four nutplates in a pattern that matches the ADSB module hole pattern. This is ready for electrical and RF wiring.

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Another project is the fabrication of prop gap fillers behind the blades. I considered making these out of fiberglass but I did not see an easy way to mold them so I followed the Vans suggestion and made aluminum two-piece gap fillers, Here is my first attempt. It started with a paper template that I refined in two or three iterations then I transferred that to aluminum. The part you can see below is .062 aluminum sheet and there is a .032 doubler behind it for a nutplate about 1.8 inches forward of the back edge of the spinner. The doubler prevents the sharp forward edge of the gap filler from bending outward under centrifugal forces. Catto must use a tool for making these cutouts because all three are very consistent.

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Here are the two pieces that make up one gap filler. The .062 thick piece is on the left. Compound curves are required to make these fit properly. I beat the parts over a large wood with a rubber mallet to form the curve that matches the circumference of the spinner. I simply bent it with my hands to match the conical curvature.

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In this view the two pieces are riveted together such that the .032 is underneath and forms a flange that extends under the fiberglass spinner and a nutplate is installed for the lower left screw. That gives it a lot of strength and helps pull the two parts together for a flush profile.

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This view shows the first filler mounted to the spinner back plate so you can see the underlying flange easily. I got all three of these made today but I need to do some surface finish work to make them look nice.

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Categories: Avionics, Prop

Finished GPS Mount – 5 hrs

August 4, 2013 Leave a comment

Sunday Aug 4, 2013

I was able to finish the GPS mount today. Yesterday I left you with few details of the design but today the finished product is revealed. I put a light coat of primer on the mount parts first, then after the parts baked in the sun for an hour or so I sanded them smooth with 400 grit paper and applied a good coat of white enamel paint. That baked another hour in the sun and because I was impatient I riveted them together.

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Here is how it mounts in the airplane. The hinge is attached to the engine mount using two Adel clamps. The aft edge attaches to the angle bracket I made and mounted to the firewall. It is quite sturdy and should have an excellent view to the satellites through the fiberglass cowl.

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By removing just two screws I can tilt the GPS plate up to gain clear access to the oil filter. Here is how it looks tilted forward. Now the Dynon GPS antenna is mounted and I ran the wires aft through the pass-thru because they connect directly to the EFIS.

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Today I also sanded the spinner exterior surface to knock off the gloss and sprayed it with two coats of UV Smooth Prime.  This thing looks great now. It is pristine clean and very smooth. I like it.

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Categories: Avionics, Prop

Spinner Work, Making GPS Mount – 6 hrs

August 3, 2013 Leave a comment

Saturday Aug 3, 2013

Today I worked on two projects; completing the spinner and spinner bulkheads, and making a mount for the GPS antenna. The first major step was drilling the bulkheads for the K1000-08 nut plates, fifteen on the aft bulkhead and six on the forward bulkhead. I also finished the edges of the bulkheads and did the scotchbrite process to prepare for primer. After preping the aluminum bulkheads I sprayed on a light coat of primer and left them dry in the warm dry air outside.

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While that was drying I started making a mount for the GPS antenna. I decided to mount the antenna forward of the firewall and under the fiberglass cowl. A lot of builders put antennas there. I designed this on the fly with available scrap materials. The idea is to have a plate big enough for two antennas (expansion room) and make it hinge so it can be moved out of the way for access to the oil filter. You’ll see what I mean later. This is how far I got on the fabrication today. All the aluminum parts are made and I started riveting them together. I will prime and paint this tomorrow when I have more time.

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By now the spinner bulkheads were well dryed so I riveted the nutplates around the perimeters.

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Categories: Avionics, Prop