« Archives in November, 2007

Bellcranks, ailerons, and some pics.

6 hours.
After some adventures in tubing, it was time for some good old-fashioned mechanical hijinks, this time involving the bellcranks. Since I’ve got the quickbuild kit, the build sequence is, uh, fragmented. Supposedly, during the wing build, the plans and manual stop holding your hand and you need to just figure stuff out, which is fine, but it really makes you double-triple-quadruple-check everything before you cut metal or stick it together. In this case, the tubes and the aileron brackets were two discrete operations that were done separately. The aileron brackets (wing side) I did a couple of months ago while waiting for some rudder parts to arrive, and the tubes I did last week. This week, it was all about the bellcranks, which were good old fashioned meat-and-potatoes mechanical fun. I did have some issues cutting the aluminum spacer tube, which you are given just enough of to do right the first time. In my case I had to grind off extra material on the ends to get a flat end, thanks to my cheesy bandsaw, which is probably just more out of alignment than anything else. I had enough tube to get the left aileron on, and get it hooked up to the bellcrank via the short steel push tube, and I think it works OK, no binding, free motion. The good folks at Bill’s Air Center were nice enough to give me a cat-food can of aviation grease for the brass bushings in the bellcranks. I didn’t finish all the stuff on the right aileron though. I don’t have enough aluminum .058 wall 3/8″ tubing to make the spacers for it, so it’s on there in a temporary fashion until my spruce order shows up. But both bellcranks are in, lubed, and torqued, so we’re ready to rock.
Here’s the left aileron, in place, bellcrank installed. The blue piece near the bellcrank is the jig to hold it in the neutral position while aligning the aileron:

Close up of the aileron bracketry. Got good rivets on the pushrods, thanks VAF! The alignment of the ailerons is probably bogus, but here’s how I did it: The distance from the white aileron bracket on the aileron to the top of the reinforcing angle on the wing is measured with a micrometer in two places, down near the hinge and up near the end of the angle. When the measurement is the same, or within a few thousanths of an inch, that’s where the neutral position is, and the threaded bearing at the other end is adjusted accordingly before getting bolted to the bellcrank. I’m sure this will change, but it’s OK for now:

This is a shot of the right side bellcrank assembly. No jig on this one, I think I only got one and it’s on the other wing, unless it’s floating around in the bottom of the canoe which is where I’m storing a lot of parts until I get some shelves put up in the shop. I hope to finish this process this weekend while I’m working off turkey and stuffing.

Bunch of stuff.

4 hours.
And that’s a rough estimate, because I’m going to tally up the last 3 or so days with this entry. After I puzzled and puzzled until my puzzler was sore, I figured out that the only way these push tubes are going to get painted is if I just paint the bloody things. Many things were suggested, most of them variants on “blow a lot of paint in the tube and swirl it around.” This turned out to be the way to go, except when I poured some from a can into the tube. Oh, and important safety tip: Those red plastic cups people swill bad margaritas from at parties? They melt when paint hits them. “Use a cup to catch the excess,” was the advice. I should have thought about what happens when a volatile solvent hits a cheap plastic cup, but instead I spent 20 minutes power-washing spill off the concrete. A soup can was a better pick for that task afterward. So with that done, I moved on to the actual hardware. Fascinating setup, the bellcrank assembly. Drilling out the brass bushings was interesting, but I got that all done without too much trouble, and the only thing I fouled up was making the spacers for the aileron hinge bolts.. No biggie, got a length of 6061 5/16.058 tubing coming from spruce this week. Got one done correctly, and I should be able to finish the other in short order. But the left aileron fits on great, of course I’d expect it to, it’s a QB aileron. the bellcrank works, and everything moves freely. I have to get into the manual to see how to initially set up the push tube adjustment before I go tightening everything down on the bellcrank assembly. The next thing to do, past the right aileron, is the flap braces, then the flaps. Then I have to figure out if I want to do a return line for a fuel injection system.
Pics soon.