So, I got the Audocopter 3DR kit about a week ago and I finally finished putting it together. I had finished all the tests and was in the processing of mounting the props when I ran into a snag. No matter how hard I screwed the prop nut down, the prop wouldn't fully attach to the motor shaft. There was some resistance, but very little.
Since I'm new to RC props, and the instructions warn to not over-tighten the prop adapter, I figured this was ok. The copter flew for about 15 seconds before one of the props shot off and it nose dived into the dirt. Luckily it was only about 1 ft off the ground at the time, so other then a little dust there appears to be no damage.
Figuring I just hadn't tightened them enough, I cranked the ejected prop down until the hub shattered. It will still loose right up until the moment it gave. In an effort to at least get the other three adapters on I ended up stripping two nuts. I've been poking around online trying to figure out what went wrong, and I think I've figured it out.
All the instructions I've read (here and elsewhere) say that the washer I select should fit snugly over the threaded portion of the prop adapter, and that's what I did. After looking at it more closely, that washer will never fully compress the collet. There's an odd flare at the top of the collet that every other prop adapter I've seen appears to not have. This collides with the washer preventing the prop from being tightened down, effectively tightening it against itself. See pic:
Notice the gap between the washer and the sleeve. The other problem with this is it is impossible to see the gap with the prop installed. Now, there is a washer that will fit over the flare, and I've tried it on my one remaining adapter, but the prop is extremely wobbly when it is attached. It does clamp properly over the motor shaft.
Now, my question is: Is this a manufacturing defect or was this just something I should have known? If it's something I should have known, can someone please update either the wiki or the detailed notes here: http://diydrones.com/forum/topics/propeller-install-notes . I'm getting the impression several other people may have made the same mistake, judging by some other posts.
I don't fly the crappy prop adapters that come with the motors. I usually fly these:
I ordered some of those after the first set 'died'. :) I figure the prop adapters that came with the 3DR are pretty cheap, but it would have been nice to have it fly at least once before having to buy another $30 (not including shipping) in parts.
I agree the prop adapters which came with the stock motors are crappy due to too much tolerance (gap). If you can find some metal or alluminum spacers as in the new prop adapters it should tighten quite well else you can use some loctite on the motor shaft but be careful not to flow into the motor bearings.