Jun 22, 2023     Autopilot pushrods and servo wiring - (2.5 hours)       Category: Controls

Some Dynon autopilot parts that I had been waiting for recently came in so I wanted to try to make a little bit of progress on that tonight. The autopilot pushrods come as a single piece of aluminum tubing stock that has to be measured and cut into two identical length. Then the center bore had to drilled to enlarge it to a #3 drill and then tapped for a threaded rod that would be installed in both ends.

Next, I needed to trim the wires on the autopilot roll servo and crimp on some Molex pins. It took a bit of manual cutting of the pins since they were apparently designed for an automated machine to install them, but the intro chapter in the instructions provided a good amount of detail about what needed to be done. After crimping all of the servo wires, I inserted them into the Molex plug according to the wiring diagram.

I also took some time to take the pitch servo bracket to the bench grinder to smooth some of the rough edges using the scotchbrite wheel. Then I roughed up all of the surfaces with a scotchbrite pad, cleaned with some acetone, and sprayed a light coating of self-etching primer.

I'm going to hold off on installing any more of the delicate autopilot components until after the wings are transported to the hangar, which should hopefully be happening this weekend.

  Jun 09, 2023     Prime and wrap up pushrods - (3.0 hours)       Category: Controls

Representing a little bit of time over multiple days, I have wrapped up the aileron pushrods and bellcranks for both wings. I had to prime the insides and outs of the tubes that weren't power-coated from the factory. I also had to drill the last set of holes in the torque-tubes that required a specific angle between the two arms by using a carefully measured spacer block.

The aileron bellcrank pushrods required very long rivets to be squeezed to secure the threaded rod ends. These rivets are described in the instructions as being difficult to squeeze straight, and that was indeed the case. I didn't get them squeezed with a normal looking shophead and I ended up needing to form two facets on each, but I feel they are all performing their intended purpose of securely holding in the rod ends. I may choose to redo these later if they annoy me enough.

Once all of the holes were drilled and deburred, I installed as much of the final bolts, washers, and spacers that were specified, though I didn't install any of the rods into the wings. I'll leave them out for now, since I intend to transport the wings to the hangar and do final wing assembly there.

What's next? I think I'm done with tasks that I can do on the wings for now, so I'll switch to the empennage next.

  May 30, 2023     Drilling pushrods and torque tubes - (3.0 hours)       Category: Controls

Tonight's task was to drill the holes in more of the bellcrank pushrods and the torque tubes. This was mostly straight forward, with measuring and marking approximate hole locations using a ruler. That was followed by drilling using a V-block that I had 3d-printed from a design downloaded from Thingiverse.

What's next? The insides of these 4 tubes need to be painted with primer.

  May 25, 2023     More pushrod and torque tube cutting - (2.0 hours)       Category: Controls

Based on the feedback from Vans, I took the brass bearings from the bellcrank brackets and carefully shortened their length on the bench grinder so that they were narrow enough to fit between the wing brackets and have their prescribed freeplay, and then further shortened the tube on the bellcrank bracket so that they were also shorter than the brass bearings by the amount in the instructions. Both the left and right bellcrank now fit nicely into the wing brackets.

I also spent a couple minutes to feed another piece of fishing line through the right wing, for future wire-pulling ease, and then taped the ends down against ribs. The rod-end bearings and jam nuts were also threaded into the ends of the two pushrod tubes that I had primed last night, and then stacked these tubes in the corner of the workshop for later use.

Then I started cutting the two smaller diameter bellcrank pushrods to the lengths in the instructions with the hacksaw. Attempting to insert the rod ends into this tubing was difficult, but I had expected that based on the experience of other people in the Slack channel. I used some rolled sandpaper to remove the excess powdercoating paint that might have accumulated inside of the tubes by chucking the pushrod itself into my power drill. I then also used my powerdrill to chuck the rod ends and spun them against the benchtop sander to remove some of the outer diameter so that these 4 rod ends could actually fit inside the pushrod tubes.

Since I was in a tube-cutting groove, I pulled out the black steel tubing for the torque tube and also cut two pieces to the lengths required in the instructions. A little deburring and cleanup of the ends and I could check their fit into the corresponding brackets.

What's next? I need to use a drilling jig to drill the holes in these new tubes, then prime and rivet/bolt these parts too.

  May 24, 2023     Riveting and priming aileron pushrods - (2.0 hours)       Category: Controls

Continuing from last time, I started by trying to rivet in the endcaps for the aileron pushrods. However, I quickly realized that I had not final drilled the holes to the correct size so I first upsized them to the correct size and did another quick debur of the holes. The manual hand riveter was painless and sufficient for these blind rivets.

Then a quick scuffing of the exterior of these two assembled pushrods, a cleaning with acetone, and then a quick spray with self-etching primer.

Van's support replied to my question about the tightness of the bellcrank brackets and the answer was actually not to attempt to bend the support brackets but to sand down the brass bearing (and the bellcrank brackets, if necessary) to achieve the necessary clearance. So I started by using a punch to knock the bearings out of the bellcrank brackets so that I could work further on them. This would also give me a chance to slightly reduce their outer diameter so that they don't fit so tightly in the brackets, which I had not sufficiently done the first time. Inserting the bushing into the chuck of an electric drill and letting it spin inside some sandpaper for a few seconds was enough to make the fit better.

I also ran some fishing line through the empty wiring grommets (plastic snap bushings) of the left wing, to make it easier if I ever needed to pull new wiring through those holes after the wings are closed up.

What's next? I need to finish refining the length of the brass bearings, run fishing wire through the right wing, and then work on the next set of pushrods.

  May 23, 2023     Cutting and drilling pushrods for end caps - (1.5 hours)       Category: Controls

Tonight's session was starting to prepare the two pushrods that will actuate the ailerons. The two rods had to be measured and cut from longer aluminum tubes using a hacksaw. I then deburred and sanded the cut tube. A paper template from the instructions was then cut out and taped to the ends of the tubes to allow the holes to be punched and drilled. Then the endcaps could be inserted, match-drilled, and deburred.

Then I took the tubes and endcaps outside for their first pass at priming. I sprayed nearly a full can of self-etching primer down the middle of the two tubes, rotating during the process to ensure full coverage.

What's next? I need to finish priming the outside of these tubes and then move onto installing the rivets that hold the endcaps in.

  May 21, 2023     Assembling pushrod bellcrank brackets - (2.0 hours)       Category: Controls

I decided to start working on a new section and begin working on the pushrods that control the aileron actuation. I started by measuring, final-drilling, and deburring. The right aileron bracket needed a nutplate to be riveted on with the squeezer, which will be used for the autopilot servo. Both brackets needed to have brass bearings installed into them for their pivot points. I probably should have made a greater effort to sand down the outer diameter of these bushings a little more than I did, since they were still quite difficult to push into the brackets and probably will be challenging to ever replace.

Unfortunately, it looks like one of the AN4-32A bolts that Vans shipped for the pivot points of these brackets has a bend in it. The bend was enough to make it impossible to easily insert into the bushing, so I'll have to order a replacement for one.

I'll also need to research why the mounting brackets already attached to the wing spar might be bent too close to allow this aileron bracket to easily pivot. I suspect I just need to slightly bend the angles apart slightly, but I want to verify.

The next 4 brackets needed to have pushrod-end caps inserted and then match-drilled using existing holes in the brackets. After a little more deburring, I pulled some blind-rivets to hold the ends in place.