Main control assembly

Buckle up boys and girls! This one is a tough one! Looking back on it now doesn't seem so bad, but it took a lot of studying to get everything to fit just right.

I spent a few days studying Page 16-4 in the plans and went over every single nut, bolt, washer, and tube that was going to be required to make the main control assembly. If you haven't done so already, be sure to read the Overview section... as I explain very important details about the heim joints and inserts that differ from the plans.

After purchasing all the raw materials, it's all about taking one part at a time. Measure, cut drill... measure, cut, drill... measure, cut, drill.... after a few days of work, I had all the major components required for the main control assembly.

Let's talk bearings for a moment - there is a LOT of arguments over what bearings should be used for the control system amongst canard builders (including Cozy builders, etc.) As I explained in the Overview section, the "per plans" method is to use 1/4" phenolic plates. However, with time, the phenolic wears and develops slop. To mitigate this problem, builders have replaced the phenolic with bearings.

After searching the internet high and low, I found these bearings to be a solid solution. Aircraft Spruce sells them for $3.50 a piece! (Part #: 05-14904 TRIANGLE BEARING 5/8" BRONZE). The Cozy airplane uses a similar bearings but with a nylon swivel (FMN10).

I figured over time, the teeth holding the nylon swivel in place would eat into the nylon. So going with bronze should take care of that. Worse case, if a few years from now I start to feel slop, at $3.50 per bearing, I can easily replace all of them! I should mention that I will also use these for the ailerons and at the firewall.

Some of the tubes' lengths are not given in the plans.. there's a little asterisk saying "length will vary - leave long and trim to length on installation." So before I could cut the main torque tube (CS105) to final length, I needed to install the main bulkheads that hold the control assembly (CS109 and CS118) and measure the distance between them. These are made out of 1/4" plywood.

By studying Page 16-1 in the plans (looking at the 'front seat right console' dimensions), I could see that the forward control bulkhead (CS109) needed to be installed 5.2" aft of the instrument panel and 9.1" from the fuselage floor. So I sanded the fuselage side really well, marked where the bulkhead needed to be, and used 5-min epoxy to bond it in place.

I did the same thing for the aft bulkhead (CS118). Page 16-1 'rear seat right console' shows this bulkhead needed to be 25.8" forward of the passenger seat, 8" above the floor (although I found it more accurate to pass a level through the pilot's seat and adjusted the height of CS118 to be level with CS109).

With CS109 and CS118 tacked in place, I applied 2 plies BID @ 45 degrees to both the front and back faces of each bulkhead, with plenty of overlap onto the fuselage wall.

Peel plied all edges for a smooth transition...

After cure, I used a dremel and trimmed all the edges flush. Having the bulkheads in place, I could now measure the distance between them and cut the tubes to final length.

I then cut CS106 and CS107 to final length at the forward end... I kept CS 107 longer just to make it easier to install or remove the bolt.

I now needed to complete the main control assembly all the way to the firewall. Page 16-5 shows how CS121 passes through the firewall via a "boston gear" bronze bushing. Instead, I'll be using the same bronze bearing I used previously.

But first I needed to drill through the firewall. The plans gives WL and BL (waterlines and buttlines) to show where to drill... I wish they had given dimensions based off of the aluminum extrusion. So I took out digital calipers and did some scaling to figure out exactly where I needed to drill. Started out with a pilot hole...

And then used the 5/8" counterbore tool used for drilling out the wing attach holes...

Taaaa-daaaaa! Looking good!

I then passed CS121 through the passenger seat.. installed the universal ball joint MS20271-B10 (by the way, these universal ball joints are CRAZY expensive! Close to $100 each! One is required here and another two for the ailerons!)

Linked it to the main control assembly...

Before linking it with CS122 and CS124 (the bellcrank at the firewall that connects with the aileron pushrods), I had to make sure the control sticks were 5 degrees inboard... this picture is exaggerating the angle.. but you get the point!

I installed the bronze bearing onto the firewall and linked CS121 to CS122...

CS124 bellcrank on the firewall... connected to the aileron pushrods...

And there you have it! Main control assembly from the forward stick, all the way back to the firewall! (I'll show the details of the aileron and elevator pushrods in future posts)

No comments: