Rudder Pedals and Evil Bushings!

Posted On September 30, 2019

I spent far too many hours this weekend trying to get various torque tubes that ride in bushings to turn smoothly. I gave up on the rear elevator torque tube for now, and decided to put in the rudder pedal hardware.

The rudder pedals are also torque tubes that sit in bushings… so I just can’t get away from this evil chore. After several hours and much trial and error, I finally got the rudder pedal tubes to move smoothly. I had to correct both the brackets themselves by
grinding away from the bushing brackets a little at a time, as well as the painted rudder pedal torque tube that had some oversprayed areas (the sections that rest in the bushings are supposed to be unpainted).

I did have a welcome distraction while I was working on the Sling. This past weekend the Wings of Freedom Tour visited my local airport KASH, flying in their B-17, B-24, B-25, P-40, and P-51. I didn’t go since I’ve seen these planes many times before, but they were offering rides for a donation, and I got to see the B-25 fly right over my house at about 1000′! I always get excited when planes fly over my house (it motivates me to work on my plane!), but this was pretty special… very unique sound as it approaches.

I also had to finish installing the joysticks, which again are torque tubes that rest on bushings. First, I needed to install the lock collars, after getting confirmation from TAF that I need to drill and install 4.0mm rivets in these collars. I figured this task would be easier to do in a drill press, so I removed the joysticks from their mounting brackets.

After reinstalling the joysticks and re-securing the screws that hold the rear brackets to the main spar carry-thru, I was not happy with the amount of friction on the pilot side stick. I determined that the rear bracket (CF-BKT-007-X-C-, as shown on pg E2) was not bent to the correct angle, and was therefore twisting the bushing out of axial alignment with the tube, causing friction. At first glance it looked like this bracket is bent at a right angle, but I determined (again, by trial and error) that the correct angle is 95°, see photos below for detail. I used a bench vice and a hand seamer to bend the flange to the correct angle. I didn’t measure the original angle of the part, but I’m guessing it was about 92-93°, using my iPhone’s photo editor measurement tools. At first I bent it to 97° but that was too much; bending back to 95° seems right. After I reinstalled the bracket bent to this angle, the joystick now moves buttery smooth!

Lastly, I had to finishing putting in rivnuts to the center console brackets that the skins attach to. Pascal L. recommended that I buy a chucking reamer to open the holes for the rivnuts that go into these brackets. The rivnuts are nominal 6mm in diameter, but he recommended undersizing a little to ensure a good contact surface with the ribbed section of the rivnut. He recommended a size A reamer (0.2340″), but I couldn’t find one readily available from the usual sources (Amazon, Spruce, Brown, Cleaveland), so I went with a slighter bigger 15/64″ reamer (0.2344″ / 5.953mm) from Amazon, which is still smaller than a 6mm drill bit that I had been using. Results using this reamer on a test piece were very good; I could not get the rivnut to spin when I tested with an M4 screw.