So we spent some of the session on Saturday playing around with the servos for Hummingbird, we  started by taken one of them apart so we could solder a new wire in there and get some feedback on the current position:

We then spend the rest of the day wiring up the two servos, one for the x-axis and one for the y-axis, creating a circuit and attaching it to the Arduino so we could control them independently:

As you can see, the servos are currently being controlled by a 2D joystick; this is just a concept idea, eventually that control will be replaced by a gyroscopic and magnetic sensor which will tell the servos which direction the motor needs to point to stay on course.

See them in action below:

Now we just need to order those gyroscopic and magnetic sensors!

Here’s a quick concept layout of Hummingbird. It’s inspired by David Wyatt’s Kestrel design, but uses a gimballed rocket motor instead of cold gas thrusters. (if you’re wondering what that’s about, there’ll be more about different attitude control systems in a later blog post!)

It’ll be a very modular vehicle, so it’s easy to swap out parts for improved parts once it’s been test-flown a few times and we’ve spotted things that need improving (or, erm, after we’ve broken things and need to replace them…). Features you can see above include:

• A platform to make batteries and the flight computer easily accessible and swappable.
• Landing legs made of carbon fibre kite spars. Not shown is some sort of shock absorber – this is definitely needed, becase a solid-fuelled motor can’t be throttled, so we’ll always land with a bit of residual vertical speed. (If you’re really on the ball you’ll have spotted that even with a single motor it’s possible to set the thrust-to-weight ratio slightly above 1 and then move towards the ground by “tacking” or “fluttering” from side to side… but that’s a bit of a complicated flight profile for the first batch of flights!)
• A roll cage, just in case Hummingbird lands on its head.
• The red cylinder in the middle is a Klima D3-P motor. For scale, it’s 70mm long.
• The grey boxes are placeholders for small servos as used in RC models, something like this: