A lot of people complain about the fragility of the cross. Yes, it sucks to pay for an entire new cross every time you make a minor mistake and crash the drone. Personally though, I think Parrot did a wonderful design, balancing weight, cost, strength, and function in the cross. Think about how YOU would mass produce a better cross, and I believe you find it is not a simple task.
The problem is that whether you have a minor fall or a major crash, you probably have to fork over the money for a completely new cross assembly, which gets expensive after a while!
With that said, I believe aluminum arms or struts to be a better option.
In a minor crash, aluminum will bend a little, and you can just easily straighten the affected strut. In a more serious crash, the aluminum will break. Instead of replacing the entire cross, the repair is limited to one, maybe two aluminum struts.
A 1/4" (6mm) aluminum tube is not as strong as an equivalent carbon fiber tube, but it doesn't have to be. For the length of the AR strut, aluminum is just as stable and rigid. The weight difference is negligible, but aluminum is 6.4g lighter for all 4 struts. The best part is that aluminum will bend or break before breaking either the central cross or the landing leg.
I think aluminum is a win-win. It doesn't eliminate repairs, but it does make them much cheaper, much faster, and often less work.
Check out my video to see how the AR Drone flies with aluminum struts: http://youtu.be/TIIFkkuEAk8
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Here's a build video: http://youtu.be/lpeW3Ew3L34
GREAT "how-to" video, Scotty. I am particularly interested
in how you separated the carbon fiber tube from the stock,
motor-mount landing legs. One of my landing legs broke
when the AR Drone "landed" in a tree. It needs to be replaced.
Can you buy the motor-mount landing legs separately,
or, do we have to buy a new cross-member assembly?
-peter
I have not seen anywhere to buy the cross member or the motor mounts. The wiring and plugs are standard, and carbon fiber tube is plentiful, but it's not easy to replace those plastic parts.
It is actually pretty easy to separate the carbon fiber tubes from the central cross and the motor mounts. All you need to do is soften the glue with some heat, and they pull right out. I did actually make a video just about central cross disassembly: http://youtu.be/xZjG_Ok0SQo
The best way I know of to get the separate pieces is to buy used and broken crosses from others.
Nice indoor workshop seen in your video, Scotty. More windows and natural light
would make it PERFECT. Another advantage of aluminum struts is that they can
act as a "heat sink" for the motors ...IF Parrot re-designs the assembly so the
aluminum strut makes contact with the brush-less motor central rotor.
-peter