Well I feel better now. I'm always a little nervous to fly a new ship until the first crash. You never know how she'll deal with adversity. 

I was flying FPV in loiter at ~15m when it suddenly pulled hard right and back making a nice arc into the ground at about 20kph according to the telemetry log. The current jumped from the ~30A normal to over 60A in the few seconds of the death plunge. When I got there  the motors were spinning and wouldn't react to transmitter commands including disarm. All the props were broken of course.

Looked through the logs a bit, but I can't tell what happened. If anybody cares to take a glance and give me some insight, I would be very grateful. I don't mind when things go terrible if I can at least understand why it happened. 

The damage seems to be limited to a couple of cracked arms and a few other frame bits. The GoPro was fine thanks to the waterproof housing. Not even a broken antenna on the 3dr radio or video Tx! I'm taking it all apart tonight and checking the electronics, they got covered in snow, but no physical damage that I can see so far. I'll upload some pics once Iphoto stops crashing every time I try to get them off my camera. There must be weird solar weather or something going on today, I've never had a problem getting pics off of my camera before, really strange... 

I'll have to upload my tlogs from the windows machine, just a minute.

: )

2013-01-17%2015-24-08.zip

It's raining robots-

That will be the headline all of us will cringe at, when the Media goes manic over the first commercial drone crashes of any significance. The same way they do anytime something new takes a stumble (or two).

The thought of my craft hitting somebody really haunts my mind. I'm sorry to be a downer, this topic is definitely a buzz-kill from the heady intoxication of being in the midst of the next great economic boom, but I can't let it go.

So the topic is failure. Despite what your high school sports coach told you, failure is not just an option, it's a guarantee. Yes- our thrust makers, power systems, flight controls, and firmware will get better quickly. However, even if we could magically achieve 100% reliability with all of our flight critical components, failure will still be there. The most random shit is always going to happen.

 The project-

I'm focusing on multicopters in particular with this project, but I feel that a similar strategy would be effective with fixed wing craft as well, in fact it's used all the time.

The specific type of failure scenario I want to tackle here is a total loss of thrust and/or control. Deployable parachutes are being developed, and seem to be working well. I would like to pursue a more passive system, an aerodynamic design built into the airframe itself. Inspired by watching Marcy fly around and wingsuit pilots, I hope to achieve a passive "auto-rotation" or glide of the entire airframe. If the the craft looses thrust, the actual act of falling makes the conversion into an alternate flight mode. A slow spiraling glide to the ground, with a gear down orientation maintained. Energy absorbing landing gear, maybe even a supplemental air bag would compliment the design. The key in my opinion is making the recovery mode completely non-dependent on any system other than gravity and wind resistance. Time is so critical in a recovery scheme for these types of failures at the altitude multis usually work. No sensors, servos, or firmware required, just a thoughtful arm and frame design. The challenge will be to prevent undesired flight characteristics while in normal powered flight, in fast controlled descents we don't want to be induced into a flat spin! Can the free fall decent rate be slowed enough to usefully lower the risk of damage on the ground and airframe itself?

Step one- Get to the sewing machine and build a Bat suit for one of my quads

To be continued.

One handed plug removal, simple labeling in case the copter ends up on the ground and I'm not the first one there.

10cm of kevlar thread, 6cm plastic tubing, label 

I've had this idea in my head for some time now, finally got serious about sketching it out.

Yes, I know that all the props are pushers ; ) I couldn't find the tractors and wanted to get some pics up anyway. First flights will all be with gemfan carbon plastics, but I'm stoked to use these wooden props once everything is verified to function in flight. She looks a little fat in the rear I admit, but that is 5.6 Ah 4s in a hard case. All up weight is 2.71kg.

Spindly landing gear fills in for top-secret next gen gear that can't be shown yet. This configuration has some Klingon Bird of Prey in it, that's obvious.

The goal for this project is a clear view, roll/tilt gimbal that utilizes the waterproof GoPro housing and is positioned coplanar with the motor mounts. 

I'm using a pull/pull set up for both axes. It works well, but a little more dialing in will be needed. I'll get a video up tomorrow after I clean my shop. 

Tilt control and video out are fed down the central rotating axle. This axle and gopro housing are the only moving parts, both riding on nylon bushings. Tilt pivot is vibration isolated from airframe. "Manually printed"- pivot sockets, control horns, and video out connector are attached to waterproof gp housing.

Stiffen and lighten this yoke, increase the diameter of the axle, print some proper gopro attachments (Rostock-Kossel in the works!!) The camera housing is easily opened without removing from the yoke.

Belly up view. Remember, this is just a rough draft, plenty of little changes to make for MkII, starting with a completely different frame. I'm done with the hub and spoke form. Multi-copters are basically just a packaging exercise, and I keep wishing for a different shape while trying to integrate all these sweet-ass robot parts. The next frame will be a folding Roman five, a "V" with horizontal bars top and bottom.

I can remove a lot of weight from this of course, the motor mounts, arms, wiring, etc. I like to make things heavy and adjustable at first, then begin to lighten and lock down everything.

The important part is the parallel rails and the gimbal arrangement, that's what i want to develop a bit more. The roll axis motivation could come from any number of sources, I've used pull/pull for it so the servos could be grouped and positioned optimally for weight balancing. 

One of the major weak spots with multi-rotors is the exposed propeller blades, they break and they hurt things.

I know people have designed guards and experimented with ducted fans, but has anyone done work with a boundary layer turbine arrangement? I've been kicking this idea around in the back of my head for some time now and just recently saw a ceiling fan project that uses this effect.

 I always imagined a nested conical frustum stack (imagine lamp shades stacked on top of one another with a small gap between each). As the assembly spins, air is accelerated from the center down and out at an acute angle relative to the vertical axis, whereas the above ceiling fan example moves the air perpendicular to the rotation axis. I know it will blow air, but will it move enough to provide any useful thrust? 

Any thoughts?

Now if I could just get a hold of some graphene and aerogel lampshades to experiment with...

Here are the last steps in constructing an AV plug that will fit inside the GoPro waterproof housing-

All the parts are cut down to leave room for the soldered connections, don't cut them too short or the plug will be weak and floppy. The plastic insulation has NO heat tolerance at all! be very careful if you have to solder near it, even high temp hot glue will distort it if you are not careful and conservative with the heat!

I use a small amount of hot glue to insulate anything that needs it and to help hold everything together as I put the parts back together, this is a bit fussy, you may prefer to use something that gives you more time, like epoxy or liquid tape. Just be very careful to not make a mess on the outside of the plug, also be careful not to mar any of the contact surfaces of the poles during all this taking apart and putting together!

Looks like a plug again!

Now just use some hot glue or epoxy etc. to create a strain relief that holds everything down as flat as possible. Hot glue is nice here because it can be shaped or removed very easily.

This plug is very fragile! Never pull it out of the camera by the wires, simply wedge a fingernail under the metal shoulder and pull it out.

Now drill a small hole in the back of the case, feed your wires through and terminate them with the connector of your choice, seal the penetration and go fly!

If you don't need the audio signal this project can be done much easier, as the video and ground are very simple to solder, that audio wire is a bit of a bitch to attach without adding too much bulk and making it impossible to slip everything back together. I don't recommend omitting any of the parts even if they are not attached to a wire, the plug gets really weak and the female jack in the camera likes to have the original form of the plug. If the plug comes apart inside the camera it's not that big of a deal to take the camera apart and push the pieces out of the jack, but obviously you'll be happier to avoid this.

Here are a couple of images that show a hacked 2.5mm 4-pole AV plug cut down to its smallest possible form.

 I converted this to 3-pole by omitting the tip. For mkII I will keep the tip for mechanical reasons, GoPro puts out only one channel of audio for live view, so we just need the first 3 poles to have conductors attached.

 The motive was to be able to have live video out while using the waterproof case, and it works! I bring the wires through the back of the case, where they are sealed and a servo lead terminates on the outside. This position is a neutral point for the tilt and roll arcs, a great place to make a connection!