Fatal flaw

Another video of a stable flight. 

Gonna try a backflip next time so that you won't get bored!

So, this is starting to become routine now: We assemble the copter, head out and make one very successful flight. Then we land and try to take off again only to crash. However, this time we had a fairly calm landing, but it broke nonetheless. After further analyzis, we realized that we have a very crucial design flaw regarding the current design of the copter. The small contact area of the crossbar in the lattice work is not enough to sustain the amount of stress we put on it, causing the layers to separate.

Layer separation.

Since it takes about 2½ hours to print one arm, I was not very keen on just reinforcing the bars, so this called for a completely new design, the fourth iteration of the arm.

Arm v4

It is printed in two parts, then rotated around the x and y axis creating a completely symmetric piece. It is also screwed together keeping the layers together, so layer separation should not be an issue with this iteration. Screwed together it forms an I-beam (http://en.wikipedia.org/wiki/I-beam) which is extremely tolerant when it comes to shear and bending loads. On the downside it does not handle torsion very well, but we havn't seen much of that to be honest. One major upside of the new design is that it takes a lot less time to print, one of the reasons being that you can print 4 parts (2 arms) at a time.. These 4 were printed after lunch yesterday:

Four of the new arms!

Since it is very long (18cm) it tends to warp while printing, but another benefit of the design is that since we bolt it together, the individual pieces align and become straight as an arrow!

It took some redesigning of the centerpiece aswell (not something we really wished for since the old one took 5½ hours to print, but since the socket has changed it is a necessity). I decided to make it modular (so that if it breaks, you can just change the parts needing changing) according to the same concept as the arms with two pieces per direction, as follows:

New modular centerpiece arms v3.

And it all comes together as below:

Centerpiece v3 assembled.

That is all from construction for now!