Sun With Teeth

I’m told that “Sun with Teeth” is a common Greek phrase, but we also refer to a biting cold wind, so I can’t help but wonder how the similarity came about. Translating this into today’s meteorology we get, “it’s only sunny because the wind has blown all the clouds away”. Today is not a flying day, but then I really need a break after yesterday’s drone masterclass that we ran for thirty kids aged 12 to 13.

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The drone masterclasses always take a heavy toll on equipment and the dragonfly was the first casualty, coming into contact with a window and then the floor. I’ve still got to go through all the equipment and test it, but it does look like we got more of it back than last time.

As well as letting the kids have a go at making and flying quadcopters, we also showed them an FPV drone.

 

I did design my own frame, but then found one on Thingiverse which was better and I was a bit short on time. My own frame flew for the first time on Monday, using some 75mm diameter props which I’ve had from Unmanned Tech Shop for a while now. The problem is that they just don’t work. On both the first test with my own frame and the second test on Tuesday with a different frame, the aircraft exhibited severe oscillations indicative of over-damping in the PID parameters.

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These props caused severe oscillations.

Initially, I turned down the PID values, using just a low value “P” as a tuning base, but this made no difference. Having looked at the settings for an identical F3 EVO based quadcopter that worked, I ascertained that I was in the right area and switched to the standard HubSan 55mm diameter props (the black and green ones on the quad in the photos above). The problem was aerodynamic, but I’m not really sure why at the moment. I’ve got four packs of these things as they came with the motors, so I need to do some more investigations. The markings on them are very weird, having A1, A3, B1 and B4 on one set and A2, A2, B4 and B4 on another. I’m thinking that the pitch might be different and they didn’t realise and put them into the wrong packs? I have actually flown a bigger quad where I accidentally put the wrong pitch propeller on, but it didn’t exhibit this sort of severe vibration issue.

Anyway, that’s our current event over until the next one in March, so my time is my own again. Let’s go and fix an autogyro…

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