Tuesday, February 23, 2016

Control Sticks (Part 6)

Continued from Control Sticks (Part 5)
I finished cutting, shaping, and drilling the aluminum brackets, as well as the nylon bearing surfaces. I was very careful to make sure there would be no slop in the system when I was drilling the holes. Somehow, once again, I managed to order the wrong size hardware, so everything is temporarily assembled with other bolts I had on hand. I'm going to write up a list, or maybe a spreadsheet, that lays out what length bolt is ideal for various depths of material, because I can't seem to get it right. I test assembled everything on my workbench, and marked my layout so I could transfer the brackets to the plane.

Next I marked on the front spar where I wanted the brackets to be, lined them up and clamped them, and started drilling holes. I drilled one hole at a time, making sure everything lined up before committing to another hole. I really didn't wanna screw this up!

Everything in place, at least temporarily:

As you can see, I left the actual sticks long because I wasn't sure what length I'd want. I'm going to have to give them both a slight bend so they'll have enough throw to clear the front spar, whilst remaining far enough forward to be comfortable. I'll have to disassemble when the correct hardware arrives, and I may paint everything for corrosion resistance. I also need to redo the cables - only one of the three cables has a turnbuckle, which means if the cables ever stretched or needed adjustment, you'd have a heck of a time getting things realigned. Regardless, I'm much happier with this setup - lower profile, much better geometry, and working on this gave me an idea for a really simplistic aileron trim that'd be pretty easy to implement.

Monday, February 22, 2016

Control Sticks (Part 5)

Continued from Control Sticks (Part 4)
I got my brackets and sticks back from the welder today. I forgot to take a picture of the bracket, but this is how I fitted and attached the aluminum "fingers" to the sticks for welding.

I cut a square wooden peg to match the OD of the aluminum tube, drilled a hole where the aileron cable connection will be, then chucked it up in my lathe and turned the other end down to the ID. I turned far enough along the peg to set the depth of my jig.

This is the jig inserted into the tube, with the fingers already welded on. A small C-clamp held the fingers to the tube for tack welding, and then was removed for the full passes.

I realized after I got these sticks back that I had forgotten to mark where I needed the other set of holes. The main problem I faced was getting the holes in the center of the tubing and lined up with the existing holes. My drill press vise is just far enough off of level and plumb that I didn't trust it, so instead I used a speed square to find the center on both sides, then drill and ream the holes.

I drilled and tapped a length of ¼" 4130 tubing to connect my two control sticks along the horizontal axis, which turned out to be a little bit of a trick. I chucked the tubing in my lathe in order to drill it out so I could tap it, then locked the lathe up and tapped it by hand. I didn't drill quite far enough on one end, so I broke the tap... luckily, enough was sticking out that I could grab it with pliers and screw it right back out. Another trip to the hardware store for a new tap, and I was finished. I threaded in two AN42B "eye bolts," and it was ready to connect.

The last of the metalwork for the control sticks was to make the mounting brackets. I needed a set of brackets to hold the control sticks, and a set of brackets that will mount to the back of the rear spar where the pushrod will transition to cables. I did some adjusting to Mark Langford's drawings for the former, and did some math and drew up the latter on some graph paper. Here they are, attached to ⅛" 6061 T6 aluminum angles, but not cut out yet. I started by drilling all the holes, since that can be a difficult procedure once everything is cut out.

Tomorrow I hope to finish the mounting brackets and begin assembly in the fuselage.
Continued in Control Sticks (Part 6)

Thursday, February 18, 2016

Control Sticks (Part 4)

Continued from Control Sticks (Part 3)
I made progress on a lot of little things today. I laid out, drilled, and cut the nylon bearing surfaces for the control sticks. Forgot to take pictures of that. I redesigned the brackets that'll bolt to the front spar, because the plans I'm using account for a flap design I'm not using. I'm still waiting on the material I need to fashion the brackets, so I couldn't work any further on that. I also drew up plans for the bracket assembly to hold the bellcrank behind the rear spar,  where my pushrod will transition to cables for elevator control.

I've found no matter how much I work with various CAD software, the easiest and fastest way for me to design things is still on paper. (Partly because I usually spend about an hour fighting with my printer when I want the finished design printed to scale.)

I'm not a very proficient welder, and I don't have the right tools, so I sent my jigged-up assemblies out to be welded. Once those come back and the rest of my material shows up, I'll be able to finish this project and move forward. I believe I'll finish the rudder pedal assembly next. Sometimes I feel like I'm going to run out of work that isn't fiberglassing before it warms up, but I'm well known for taking *way* longer than I say I will to finish projects.

Thursday, February 11, 2016

Control Sticks (Part 3)

Continued from Control Sticks (Part 2)
I finished cutting the steel for the main body of the assembly today.  I saved the diagonals for last, since they're the only set whose length is critical. I found a great site that allows you to input tubing diameter and thickness, angle, offset, and generates a template you can print out and transfer to your tubes. Check it out here.

I set up my shop for woodworking, so I had to get creative to cut and grind some of these pieces. I do have an angle grinder, so that got clamped to my workbench, and I cut the curved portions (where the round tube nested inside another round) with that. It was a lot easier than I envisioned it.

I used the RAS to cut my 45* to the rectangular tubing, then used my bench sander/grinder to make the fit really precise. Finally, I attached them to the jig, which will be welded after I cut and fit all my aluminum (in case there are any surprises).

I measured and cut the pushrod/shuttle that will connect the two control sticks, and drilled the ends to accept a 10-32 tap. Unfortunately, I cannot find my 10-32 tap, so this is where I quit for the day.
Continued in Control Sticks (Part 4)

Tuesday, February 9, 2016

Control Sticks (Part 2)

Continued from Control Sticks (Part 1)
I've decided to go ahead and post something just about every time I make progress, rather than waiting for an area to be entirely finished, and then consolidate once something is completed. I think that'll help me remember more of each step, so I'm not trying to remember what I did a month ago.

I drilled, cut, and placed my rectangular tubing today. First I marked the hole location on both sides of the tubing, then drilled pilot holes individually for each side.  (My drill press vise doesn't seem to hold material very square.) These only need to be 3/16" holes, so I jumped up to 11/64 and again drilled each side separately. Finally, I chucked up a reamer that's .0015" smaller than I need, and reamed through the entire tube. This made the holes in each wall line up very well.

After my holes were drilled, I cut the tubing to length on the RAS. I spent another hour or so making sure the blade was square and straight, and it still wasn't perfect, so I cut the pieces a hair too long and used my bench grinder to get them perfect.

I then used the drilled tubing as a guide to drill two straight holes through my jig board, and used two bolts to hold the tubing in place. This works better than building a clamp like I am for the round tubing, since the hole placement is what's really important.

Next I'll be cutting the diagonal tubing, which needs to be really perfect. I have enough material for at least one mess-up, though, so maybe I'll be able to finish this without ordering more.
Continued in Control Sticks (Part 3)

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)