Firewall Support Bracket & Aileron Controls

I have spent the last month (has it really been that long since my last post?) doing non-picturesque stuff for my Bede BD-4C. The good news is that I now have 368 hours into the project, which means that I am 41% done, if you believe BedeCorp’s estimate of 900 hours to build the BD-4C kit, and if you ignore the time required to install the engine, and if you ignore the time required to install the instruments, and if you ignore the time required to install the interior amenities, and if you ignore the time required to paint the plane. But I’m holding onto that 41% figure because I’m a terminal optimist!

First up was the firewall support bracket, one of the very few steel parts that had to be fabricated and spot welded in my plane. This bracket is a large V-shape, attaching to the center of the firewall and extending back and up to the sides of the fuselage. Most of the parts for this bracket were simple flat plates. There was also a short tube which was easy to cut. I had some trouble with the two long tubes (the legs of the V) so I mocked them up with pieces of scrap wood. Each needed to be angled at the top en, then angled and cupped (to fit onto the short tube) at the bottom end. Here is a photo of one of these mock-ups being test fitted. This picture is taken looking forward and to the right; the co-pilot’s pedals will be installed in the bottom, center of the picture. (Click this, or any, photo to see a larger version.)

Roy Jonas, son of one of the men in EAA chapter 32, is an absolute welding wizard. He came over and spot welded everything together in the plane. (I can claim that I “helped” because I held things in position while Roy did all the real work.) A couple of days later, Roy brought back a TIG-welded firewall support bracket which fit perfectly.

Roy also welded the rod ends into the five push-pull tubes that I had built. I had riveted the rod ends in place, although welding was the recommended procedure. The heat from the welding ruined the rivets and the paint so I spent some time drilling out the rivets and installing new ones (as back-up, in case a weld cracks) and repainting.

I spent the rest of June working on the aileron controls (or hiding from the heat).

The aileron cables form a large rectangle and there are four pulleys, one at each corner. I fabricated shims out of 0.063 inch thick aluminum to facilitate mounting the rear pulleys.

The aileron cables pass through the main gear box. It had 3/16 inch pilot holes drilled for the cables. I enlarged these to 1/2 inch. Later, I will install plastic grommets.

I assembled the lower bell cranks, which entailed remaking one of the bell crank brackets because the first one that I made was 1/10 inch too short. Then I fastened the bell cranks to the fuselage. Here is a picture of the left bell crank. The aileron cables will attach to (and move) the arm on the right. A push-pull tube will get attached to the arm on the left (which will move up and down).

Before you ask: No, my hand is not a permanent part of the aileron control assembly. The push-pull rod will be attached with an AN4 bolt. 🙂

With the bell cranks in place, I decided to mock up the aileron cables with Nylon rope. Doing the mock-up is letting me assure that all of the holes for the cables are in the right places so that the cables will not rub on other parts. It is also giving me a chance to figure out how to assemble all of the parts without cutting up the steel cable.

I am most of the way through this process, with five of the six mock-cables built. Here is a photo looking into the fuselage from the co-pilot’s side.

There are five cables built so far:

1. The first cable runs from Candy’s hand through the left, rear pulley, and into the left bell crank (which was pictured above).
2. The next cable runs from the bell crank, through the gear box, to a turnbuckle between the gear box and the left, front pulley.
3. The third cable runs from the turnbuckle, around the pulley, to the bottom of the pilot’s control stick (wooden mock-up in this photo). A push-pull tube connects the bottoms of the two control sticks.
4. The fourth cable runs from the bottom of the co-pilot’s stick (another wooden mock-up), around the right, front pulley, into another turnbuckle. You can see the beginning of this cable in the lower, right corner of the picture.
5. The last cable runs from the turnbuckle, through the gear box, and to the right bell crank. You cannot see this on in the photo.

The sixth cable will run from the right bell crank, through the right, rear  pulley, and to a turnbuckle which will close the loop, connecting to the first cable. Do scroll back up and click on the photo. You will see a larger version of the picture and will be able to see the details that I have described.

Next: mocking up the last cable and then building the whole set out of steel.