Before I can get together a final design for the frame of the quadcopter (now that I know what the inside is going to look like) I need to decide on and model a connection from the four arms to the central body. They can’t all be printed at once because my printer isn’t big enough, and anyway it’s always better to print smaller parts in case anything goes wrong or you have to change something.
At my disposal, without having to go and buy anything, are lots of countersunk M3x10, M3x8 and M3x6 screws, and so I’m going to use these along with some nuts to attach the arms to the frame.
One thing to bear in mind is the actual design of the arm, which I haven’t settled upon yet. Although it poses problems with support material, which I’ll discuss later, I quite like the idea of having the arms hollow (or at least with a thin channel down them) so that the cables to the motors are hidden from plain sight. It makes everything look tidier. However I won’t assume this, so in my design I’m going to use a mockup of what the end of the arm could look like, with a hollow section at the very end (you’ll see what I mean).
Right so there are a few options. I could add a ‘t-shaped’ bracket to the end of each arm that screws directly into the body. The problem with this is that, the only thing holding the arm up is the plastic itself, and due to the nature of 3D printed plastic this is probably not going to be strong enough, at least for my purposes.
Although there are other things I could do, the best option seems to me to be hollowing out the very end of the arm and creating a ‘slot’ in the frame that is goes into, and then is screwed in place from the sides to secure it.
Kind of like this:
I had significant fun with the rendering workspace in Fusion 360:
Main CAD design up next.