Monday, February 8, 2016

Control Sticks (Part 1)

In my research, I've come across a lot of great ideas and problem fixes other folks have designed.  While there are a few things I'm doing differently than anything I've found, for the most part my intent is to fly this thing ASAP. As a result, I'm borrowing heavily from a few sources. The main source is Mark Langford, partly because his ideas make a lot of sense to me, and partly because he detailed the problem, his solution, and his reasoning so well. In some cases, he designed his own parts and uploaded the design. The control sticks are one of those cases.(See them here, about halfway down the page.) My fuselage is not widened, as his is, so I adjusted the plans slightly to keep the sticks centered for pilot and pax. I also won't have flaps, so the brackets will be a little different. I've decided the best way to make everything line up is to build a complete jig, and then weld everything in place. I started with a piece of MDF that I squared up, then used a square and ruler to draw the design to scale.

After everything was drawn up, I routed a ⅝" channel ⅛" deep for the larger 1 ¼" tube to sit in, putting it at the right spot in relation to the 1" tubes. I made a few wooden "brackets" to screw down over the tubes to hold them in place. All of my tools are made for cutting wood, so I had to swap the blade on my radial arm saw. As if it wasn't a scary enough tool already! It took me about two hours to get it all squared up so I could start making cuts. I managed to get the main shaft cut and deburred, and it's in place with the washers ready to be welded on.

That's as far as I got yesterday. The two 45* tubes will be a lot more work, since the main shaft has to nest perfectly into them. As I was researching tig welding 4130, I came across a page that talks about a group that welds race cars. The author had asked one of the head welders what kind of tolerances they used when cutting pieces, and the welder responded that their tolerances ranged "from perfect to almost-not-perfect." Not a lot of room for error.
Continued in Control Sticks (Part 2)

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