Firewall Forward « Matt's RV-7 Project

Archive for the ‘Firewall Forward’ Category

Firewall electrical stuff

Sunday, October 21st, 2007

This weekend's big accomplishment was getting the remainder of the major electrical components mounted on the firewall:

Down by the starter contactor, I installed bases for ANL current limiters. One is where the main alternator B-lead will attach, and the other will feed the main electrical bus through the firewall. They both take power from the upstream side of the starter contactor via copper bus bars. I'll insulate this area with rubber terminal boots when I bolt down the fuses.

This 6-position fuseblock comprises my always-hot battery bus. It will be fed by a short 10 AWG wire directly from the hot side of the master contactor, and will power things like the hourmeter, the electronic ignition, and so forth. Just above the fuseblock is the relay that energizes the E-bus. By the way, these are all automotive-grade components, so I don't have any qualms about mounting them on the hot side of the firewall.

Above the E-bus relay are two holders for Littelfuse Midi fuses, with I think are the same as a Bussman AMI fuse. These do the same job as their cousins down below, they're just smaller… one will connect to the standby alternator B-lead, and the other will feed the E-bus through the firewall. Since they are OEM automotive components these fuse blocks have 5mm studs, which may end up being the only metric hardware on the whole airplane.

All this stuff is attached to the firewall with nutplates – lots of nutplates. I fabricated a whole series of doublers to mount everything, which is what consumed the majority of my building effort this weekend. Then Mary, who is awesome, took time off from studying to help me rivet them to the firewall, even though she has exams this week, because that's how awesome she is.

Seriously, did I mention she is awesome?

Posted in Electrical/Panel, Firewall Forward |

Firewall doublers

Sunday, October 14th, 2007

I was occupied doing various other things for most of the weekend, so I didn't get much done on the airplane. I did manage to make another little doubler for the firewall, to secure a cable clamp next to the master contactor. One of the rivets ties into the diagonal firewall stiffener:

Mary was nice enough to come help me rivet on the two doublers that needed to be installed. We back riveted them, with her doing the bucking on the outside and me taking many trips down between the rudder pedals to drive the shop heads:

Here's the same doubler riveted in place. It supports a nutplate that anchors the lower end of the positive battery cable near where it connects to the master contactor.

Up above, I riveted another nutplate to the firewall stiffener to capture the other end of the cable. Now the cable is mechanically secured by the clamps, and there isn't any stress on the terminals. The battery cable is from B&C, by the way.

We also riveted on the doubler for the fuel fitting:

Even though I moved it a bit, the fuel hose is still going to be quite close to the starter contactor, though apparently that's normal. This photo exaggerates the effect – there's really a half-inch of clearance between the two components. I'll just insulate and clamp everything really well so there won't be any interference issues.

You can also see in the photo above how I insulated the copper bar between the master and starter contactors with some rubber terminal boots.

I just had time to start sketching where I want to put the remaining firewall-mounted electrical components before I had to call it quits.

Posted in Electrical/Panel, Firewall Forward |

Further fuel plumbing

Thursday, October 11th, 2007

The Andair fuel valve has mounting ears that are pre-drilled for nutplates. Actually, they're even pre-countersunk. Cool.

I fabricated the line that goes from the pressure relief valve (small blue cylinder) back to the tee on the fuel valve.

Then I made the line that comes out of the other leg of the fuel valve's tee fitting, runs under the pump bracket, and connects to the input of the fuel filter. The 180-degree bender I borrowed from John made this pretty easy.

Here's an interesting little gotcha I found… if you have an engine with horizontal induction, the doubler for the fuel fitting that goes through the firewall interferes with the starter contactor. Maybe I'm the first person to install both an engine and a battery on their airplane? Anyway, some people have worked around this problem by installing the doubler on the inside of the fuselage (example here). I ended up just making a bigger doubler that fits completely underneath the starter contactor's mounting foot.

Posted in Firewall Forward, Fuselage |

ELT access door

Sunday, April 1st, 2007

After not getting very much done yesterday, I wanted to pick a simple project and blast through it today. I chose the access door for the ELT, and I got it mostly done after several hours of work. The goal was to create a door in the baggage floor that covers the ELT and fastens with latches that can be opened without any tools – I figure that might make a difference after an accident. The latches also have to be flush when the door is closed – this area will be covered with carpet, so protruding fasteners like these won't work. The last goal was to avoid sacrificing any of the strength of the baggage floor, despite cutting a big hole in it.

I started by cutting a blank out of 0.032" alclad and match drilling it to some of the screw holes in the left side baggage floor. This piece was the start of a doubler for the big hole I later cut in the floor.

I fashioned it into a doubler ring, using a unibit, snips, and files. Before it's installed permanently, I'll bevel the edges so the material of the baggage floor will lay over it properly.

Then I cut the hole in the floor, using the same method. The doubler has a 3/8" lip on three sides, and no lip on the side where the hinge goes. The hole looks overly large here, but you actually need this much area in order to get the ELT in and out and to give the latches a place to fasten. And yes, at this stage I did make doubly sure that I could finagle the ELT in and out through the hole.

I made a simple door out of more 0.032" and fit it for a hinge. I also fashioned some scrap angle into stiffeners that run along the front and back.

Test fitting the door. Notice that I doubled up on the screw holes around the door to reduce the amount of flex.

More test fitting of the door. The way the door matches the cutout in the area of the hinge leaves a little to be desired, but I'm not too worried since this will all be hidden under the carpet when people are looking at my airplane.

To keep the door closed, I'm using a pair of Hartwell latches. (Compare ACS's new price to their surplus price – ouch! Luckily I can get surplus ones locally even cheaper.) I only had time to rough out the hole for one latch, but it turned out okay. A little more filing and deburring and it will be done, then I'll do the other one to match. I wish Avery sold a drill bit that would make a square hole.

Here's a view of the back side of the latch. These are designed for thicker material, so I'm probably going to have to make some shims to make them flush with the top of the door – otherwise I suspect I would have latches opening inadvertantly when I put luggage back there.

My other project today was removing the blade from my mower and taking it to the hardware store to be sharpened. It won't be done till Friday, so that means I get to avoid mowing the hateful lawn, which is already getting pretty long, for yet another week. I can't imagine ever regretting that decision!

Posted in Firewall Forward |

Engine arrived

Monday, February 26th, 2007

This morning I got a call from the freight company telling me that the engine was waiting at the dock, so after work John helped me bring it home using his pickup. Then, he and Scott helped me get the 400 pound crate into the garage. Behold:

Shiny:

More shiny:

Shiny here too:

Mattituck Red Gold engines are built from start to finish by one technician, who then signs his name in gold on the case. Good job, Pat.

Unfortunately the huge crate was taking up more than its fair share of the garage, so I broke it down and put my little card table over the top of it so I can use the area for plans and parts. The engine will hide under there till I need it.

I'm thinking of calling it the "Limited Edition Lycoming Executive Desk". Take that, MotoArt!

Thanks to John and Scott for all the help getting this thing into its new home.

Posted in Engine, Firewall Forward |