Firewall

July 14th – I have been working over the last couple of months on planning the location of, and then installing, the various components that are mounted on the firewall. These are the Gascolator, Battery Box, Coils, Battery Contactor, Voltage Regulator, Oil Separator, and the Main Grounding Bus Bar.

Firewall components.

To get an idea of where all these components will be mounted, I installed the Intake Manifold and Starter Motor, then mocked up the location with some foam versions.

After making sure there would be room, I then removed the engine to allow better access.

The first item to install was the Gascolator. This is essentially a sump, with some filters in it, to provide a low point in the fuel system to trap debris and allow fuel samples to be taken. The version that came with the kit had the fuel line coming in the back, but, as I want to minimize the number of holes in the firewall, I made up a bracket out of angle to change the orientation to line up better.

When the firewall component section is complete, I am going to have some fuel lines made up that will be wrapped in firesleeve, but I will have to re-hang the engine to get accurate measurements.

The next few items were simple to fix in place though I did move things around to make for efficient runs of cables and lines.

I am using an EarthX Lithium battery, which is both light and powerful, but is smaller than the battery called out on the Sonex plans, so I had to measure and make up the battery box.

Version 1 was okay, V2 was better; V3 probably would have been perfect, but in the spirit of ‘perfection is the enemy of completion’, I decided that V2 would suffice.

I made a retaining strap, and then riveted it all in place.

Next, I had to provide access through the firewall for the wiring. There are two major issues with making holes in a firewall, preventing flames getting through in the event of an engine compartment fire, and, more insidiously, preventing Carbon Monoxide getting into the cabin. I do have a CO monitor in the cockpit, but this is definitely a case of ‘an ounce of prevention is better than a pound of cure’.

I am using a stainless steel fitting that is wrapped in two layers of firesleeve, and, when the wiring is complete, will also be filled up with a fireproof sealant.

With my change in plan regarding not being able to use the Vertical Power PPS system, I redesigned the electrical system, ran some new wires, then tidied up the remaining spaghetti…

Then it was a question of measuring, crimping on the connectors, and hooking things up.

Some of the leads have been left long, ready for final install when the engine is back in place, but I got sufficient things hooked up to put power to the onboard systems using the aircraft battery for the first time. I had two of the data wires crossed up, but after trouble shooting that, it all worked! Most satisfying.

I can’t do much else here without re-hanging the engine, and before I do that, I have to install the fuel tank and run the fuel lines. Stay tuned…

September 11th – Upon further review, there were a couple of other things that I took care of before the fuel tank as I needed access to the area under the glare shield and it’s a squeeze as it is. The first was the brakes; I was never really happy with the Nylon lines running through the engine bay, so I ordered some tubing, fittings, and a flaring tool and ran solid lines inside the cabin.

Then I measured from the through the floor fitting to the calipers, and had some braided brake lines made up.

 

Next came another oops moment. As I mentioned previously, I am using an EarthX Battery which is a Lithium Iron Phosphate battery, and as such needs a specific charger, I ordered one up and then went to take the battery out to put it on the bench. That was when I discovered that the current sensor mount and fuse box were perfectly positioned to prevent removing the battery. Rather than try to reposition them, I removed the battery box and made a removable side door so I can take the battery out sideways.

In the cockpit, I then roughed up the position of the Throttle and Mixture controls, as they will both have to pass through the firewall too. The trim will be mounted in the same area, but the cable for that will come back under the seat to attach to the elevator pushrod.

Then I got the crane out and rehung the engine. As you can see, it’s tight working back there, but there is no other way to ensure all the wiring and control runs work.

I ran the electrical wires first, and eventually the rat’s nest started to get sorted out; the pictures don’t really show much difference, so take my word for it. After much head scratching, I decide to run the Throttle and Mixture cables outside of the oil collector so I drilled some holes and ran the cables. I also needed something at the other end to attach them to so I mounted the AeroInjector, a flat slide unit, which is what Sonex recommend instead of a bowl type carburetor.

There then ensued a period of fitting and finagling the cables to ensure smooth operation without any binding. I ended up moving the throttle cable but eventually succeeded in getting everything working in a satisfactory manner. With the AeroInjector in place, I had measured the required runs for the fuel lines, and with these set in place along with the exhaust pipes, we have a working fit. I also put the sticks back in to ensure clearance between the pilot’s stick and the trim wheel.

I then bit the bullet and mounted the fuel tank permanently; the bending of the fuel line was fiddly and the less said about working upside down under the tank to get the strap bolts connected, the better.

There are a few more electrical wires to run to the RDAC but I’m getting to the point where I need to start wrapping bundles and permanently installing instruments, which means I’m going to have to start some finish work to make it look pretty. I guess I’m going to have to figure out paint, fabric and etching…