Monday, December 3, 2012

Brake Lines & Fuel Pumps

I have been working on my project, but sometimes you get caught up in the details and it doesn't seem like you're making any progress. In fact, you are, because attention to the details makes a better aircraft.

click on image to enlarge

I needed to run my brake lines though the lightening holes in the F2 bulkhead and they were rubbing against the edge.  Later I will be running wiring through this bulkhead also. So, I went looking for an edge trim material and finally saw a nice solution on another builders CX4. I can't remember who it was, but thank you! You can see it in the photo above. It is called Grommet Strip and I purchased it from as suggested by the other builder (Item #GSNC-1).  It comes in two sizes and this one works on material up to a thickness of .036". I ordered 4 feet and was hoping it came in one piece so I could cut it to length. Unfortunately, it came as four, one foot pieces. It is designed for circular holes for which the F2 bulkhead holes are not. They are made of a hard plastic and rely on the memory of the material to stay in place within a circle hole.  This might work for our oblong F2 bulkhead holes if it came as one piece, but it takes two pieces of the 12" strips to fill the circumference. To help keep it in place, I used some of the high temp clear caulking I was using to fill the holes around my firewall edge.  The caulking keeps the trim in place quite nicely.

This next photo shows the F2 bulkhead from the rear.  You can see that I used a larger tube to protect the brake line where it comes through the F2 bulkhead and 3 layers of heat shrink to protect it from the upper longeron hole it goes through. There is little to no movement at the point it goes through the longeron, but I wanted some protection from rubbing anyway.

I have been working on my fuel system also and decided on installing two pumps in series.  To minimize vapor lock situations, I also decided to install them on the back side of the firewall where they will remain cooler.   Instead of mounting them directly on the firewall, I created a mounting bracket from some scrap .062 aluminum I had laying around. I just bent a 90 degree flange as a mounting point. I drilled 3 holes in the lower engine mount cross angle for AN3 bolts and installed nut plates on the underside of the bracket flange so that it could be removed to work on or replace a pump.  The photos below show this installation.

Up next is the gascolator installation and running the fuel lines through the firewall.

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