Strengthening Quadcopter Foldable Boom Arms

I’ve been fairly satisfied with my second frame for my Alien 680mm Quadcopter. The “Alien” frame is a foldable design, meant to be more portable and easy to transport. Unhappy with the first frame I purchased, I picked up a second one and transferred all the parts. It has been much improved.

Part of the catch with my new frame is the foldable arm mounts were weak. I ran into some issues trying to level my motors and noticed that the arms were not level with each other, and were actually sagging. There was some play in the arms, vertically and horizontally. Imagine how messed up that could be in flight with arms moving up and down and the flight controller trying to compensate. And over time that play in the arms would certainly end up in an arm failing.

Notice how much play there is around this clamp? Bad bad bad.

I took a look at the old mounts which came on my first frame, and those happened to be more solid, by a long shot. So I ripped apart the bird and replaced the weak arm mounts with the more solid ones from the old frame. The difference is remarkable. My bird is much more stable and the video quality is better. I will have to mod the folding clamps a tiny bit but that’s not a big deal.

Left: the better 16mm arm mount
Right: The weak one which was removed

It’s nice to have an entire extra frame of parts to pick from when building or tweaking a build of a multirotor copter.