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These pages document an attempt to make the Lego RCX programmable brick fly a 'hang glider' along a pre-programmed flight-path.

The pictures are organized as follows...
The pilot: close-up pictures of the RCX pilot, details of the external power supply.
Testing: the test rig, modifications to the stunt kite, attachment of the RCX to the kite.
Flight: the RCX (mostly) in the air.

Ready for launch!

If you try this yourself, you do so at your own risk. I strongly recommend that you make a 'test pilot' out of a bunch of 1x16 Technic beams and a Lego weight element. That's what I did to try and figure out the bridle setup for slinging the RCX under the kite. My first test flight from the balcony launch position was an immediate stall and plummet -- I'm not sure the RCX would have survived if it had been attached. Similarly, once I had the RCX mounted, I did numerous test launches at ground level before moving up to the balcony launch point. Start small, work up, and don't blame me if you trash your RCX.


The 'hang glider' was actually a slightly modified two meter stunt kite.

The flight path was trivial -- fly straight for one second and then run a micromotor (attached via a cam and tiller line to the bridle of the kite) for a brief interval to shift the weight of the RCX and bank the kite into a gentle descending spiral. I chose this flight path because: a) I wanted the RCX to do something, not just be a dumb payload; b) as you can maybe see from the flight photos, our yard is not the ideal place for testing this application of the RCX -- there is a big tree to the right of the launch point, a telephone pole with cables strung to our house on the left, and a chain-link fence around the perimeter; I wanted to avoid smashing the RCX into any of the above if at all possible.

The program used for this job can be downloaded from the Code link. The program beeps a countdown, waits one second, turns the micromotor on for a brief interval; after the countdown, a separate task beeps at 0.5 second intervals so that I can tell the flight time.

The trick is to power the RCX with an external 9V battery connected to the RCX's AC/DC power port, and then take the six AAs out. This modification makes the RCX significantly lighter, thus prolonging flight time and also reducing the g-shock on 'landing'. Note that the RCXs which come with the LEGO RIS 1.5 and 2.0 do not have an AC/DC power port -- if you don't have RCX 1.0, no one can call you a chicken if you don't try this yourself.

The RCX is really too heavy for the available kite. Even with the external 9V battery it has all the aerodynamic style and grace of, well, a brick. Maybe the Microscout from the DDK would have been more suitable for this task, but I don't have one of those.

For the record, the RCX made 17 'flights' and is still functioning fine. The maximum flight time achieved was 4.5 seconds (flight #2: RCX as dumb payload, a lucky gust of wind, and it switchbacked over the chain-link fence).

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