Thursday, May 3, 2012

Cambridge Mini Maker Faire + Kramnikopter

A couple weeks ago I went to the Cambridge Mini Maker Faire. It's a smaller event than the full-scale NY Maker Faire I went to in September, but it's much closer to home. In fact, it's within walking distance, so I decided to kart everything over.

Yes, kart.
It turns out that tinyKart makes a pretty good hand truck. Also along for the ride was Pneu Scooter (ziptied to the frame), Twitch, and 4pcb (in the seat). Unfortunately, the Mini Maker Faire is too crowded for the vehicles to be effectively (or safely) demo'ed. And it was too windy to fly 4pcb.

So that just left one option:

Balloon Twitch.
You can see how windy it was by how far the balloon is deflected. The balloon was my way of making sure that nobody stepped on Twitch accidentally, but it also made the robot a lot more "interactive". And by that I mean that several little kids were teased.

Sorry for the blue video...forgot to turn off manual white balance...

You can find more photos from CMMF 2012 in the Flickr pool.

I was really looking forward to demo'ing 4pcb, since it drew so much attention at the NY Maker Faire despite not actually being flyable at that point. It's small enough not to pose much of a safety risk, but micro quads really don't like wind. In general they're twitchy and hard to fly. Giant hexrotors have the opposite problem: they're very stable, but too dangerous to use anywhere near people.

To fill the gap in my flying things fleet, I decided to put together a Turnigy Talon frame from Hobby King. I got to fly one that was put together by Daniel Kramnik (of Tesla Coil fame) and was very impressed with the quality of the frame. For $34, you get a real carbon fiber + aluminum frame. Add to that four $7 motors, four $14 ESCs, and $18 battery, a $3 bag of props, and $15 control board, and you get a complete mid-size quadrotor kit (bring your own radio) for $154.


Here it is with 4pcb propped on it for size comparison:

The Talon frame is very impressive, even without considering the cost:performance ratio. It's stiff and light and it looks amazing. It also seems very durable - you'd have to crash pretty hard to break it and the landing gear is nice. When you take into account the fact that it's $34, it is one of the best deals I've seen.

The motors, on the other hand, leave something to be desired. They are the most inexpensive of an already low-cost/low-quality brand name, which means they have some issues. Mostly, I ran into axial alignment problems - the can and shaft are poorly constrained. They are also not balanced. If I were to replace one component right now, it would be the motors. They do look cool, though. 

For what it is, the KK board is an impressive deal as well. It's rate-mode only, so it can't do self-leveling, position hold, altitude hold, or any other more advanced features. 4pcb flies in self-leveling attitude mode, so returning the sticks to center means it tries to go to level (zero angle). So it took some practice for me to learn how to fly Kramnikopter in rate mode, where returning the stick to zero means zero angular velocity. You can see me learning the new input mode a little at the start of this video:

After filming the first half of that video with it, I decided to go ahead and attempt to fly my HD video camera. I have a long history of attaching my camera to things that move, but this would mark the first time that it's actually left the ground. The mount I made was pretty simple:

Kramnikam v-1.0
On one hand, the camera flew and survived. But it's not quite a cinematic experience yet. This camera weights exactly 300g, and it's just a little bit too heavy for this combination of motors and props. The resulting flight is very close to being unstable, since the motors are almost maxed out. The more obvious problem is that my initial vibration isolation solutions (foam tape, felt) didn't help much. So, lighter camera and softer mount seem to be the next steps. For now, I have a really nice medium-sized quad to play with.

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