V-22 Osprey Project - Swashplate Repair

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It's been a while since my last post.  In July my father, my son, and I traveled to Malvern, OH, for the annual Flite Fest RC festival hosted by Flite Test.  I took the Osprey with me to show off with the hopes of a demonstration flight, but it was not to be.

I noticed prior to leaving for Ohio that one of the ball links on the left swashplate had stripped out and was loose.  I attempted to glue it back in with CA glue as an extreme thread locker, but it came loose during the 1500 mile trip.  At the festival I tried to glue it again with some epoxy, but it came loose again in handling at the festival.  Without any additional supplies on hand this meant that any demonstration flights were cancelled.

When I got home I was able to repair the swashplate and ball link by drilling out the ball link itself and threading it with a 2-56 thread.  The original threads were 2mm and 2-56 is just slightly larger at 2.18mm.  I also drilled and threaded the swashplate for 2-56.  I used a short section of 2-56 threaded rod to thread into the ball link.  I cut a little relief on the back side of the of the swashplate to allow a nut to seat flat.  I then assembled the ball link, swashplate, and retaining nut using the threaded rod and thread locker.  After assembly, I cut the remaining rod flush with the ball link.  I'm confident that this won't be the weakest link any longer!


I do have some lingering concerns over this build, and I'm not confident that this will be the winning design.

  1. There is a decent amount of backlash in the tilt mechanism gear.  There is a lot of torque on the servo and gear and I think this backlash may have a negative impact on stability and flight.

  2. The most recent 3D printed parts I used a transparent PETG filament that I thought would look nice and be more durable.  However, after printing and assembling these parts I performed some other prints with the same filament and it seemed quite brittle and had poor layer adhesion.  I'm concerned that with the stresses involved that these parts could fail with spectacular results.
My thoughts on how to remedy these issues:
  1. For the printer filament issue I can certainly re-print all of the affected parts.  However, this means completely rebuilding the wing.  Rebuilding it would take up considerable time and supplies.

  2. I've long thought that using a simple gear tilt mechanism would have too much backlash or not enough holding torque from the servos.  I've examined the mechanism in the Rotormast V-22 and it uses a rack and pinion mechanism with a customized servo with external potentiometer.  I believe that I could copy this design, but it will require many modifications of my design.  First, I only have a single stage gear reduction in the rotor.  This means that the driven gear is quite large and sticks out from the rotor side plates.  The gear would interfere with the rack portion of the actuator.  I would also need to modify the servos to have an external potentiometer.

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