Rick's b.log - entry 2010/11/06

My new toy ☺

My local supermarket has unrolled its Christmas presents section, and a little helicopter caught my eye.
Okay, it is utter crap when you compare with the helicopter I would have liked (a Morley F1 Carbon - see here). But then, this cost €35 and the F1 would have run to around €1500+ with accessories and a decent gyro. You can kinda see where I'm going with this...

Anyway, the hope is to fit some sort of camera to it.

Here's the first picture, of the model in tickover:

The model I have does not appear to contain a gyro to stabilise the flight, though there are reports (go Google) that the gyro can make things worse. My model is a "TianXiang 9009" which appears to be the same as the "Syma Alloy Shark s006"

One thing that bugged me was one of the astonishingly bright front lights was mounted skewed. So I set about fixing it. Well, as good an excuse as any to disrobe the thing!

On the photo on the box there is no metal shroud around the motor and gearing (you can see an example on the US version). I could make a comment about the Chinese concept of 'safety', but I won't. For the European market, I would imagine the shroud was necessary. So I took one half of this off, unscrewed the top of the front cover, and then unclipped the bottom, to reveal:

The control board is quite visible, with ICs on the underside, for what we see here is mostly the switching for the motors. Under the control board is a 3.7V 1000mAh Li-Ion battery. This is said to give around 8-10 minutes flight time (!) for a charge of around an hour. Yikes.
Looking back, you can see two huge cogs and a very visible motor. There is a motor in front of the spindle as well (look for the heavy duty wires).

The way the helicopter flies and "hovers" is by having two rotors which spin in opposite directions. There is no true tail rotor, so without this the helicopter would just spin itself to oblivion. The way around this is to run two rotors of equal weight in opposite directions. The forces that would cause the spin thus cancel each other out and, no spin. This is Newton's Third Law in action. It is, however, a bit of a balancing act as if the rotor speeds are mismatched, a spin can occur.
This, actually, is used for the steering. By deliberately slowing one or other of the rotors, the helicopter will turn.
Forward and backward flight is so simple it is comical. There's a tiny (and I mean astonishingly miniature) motor on the tail boom, with a tiny rotor like 4-5cm end to end also mounted horizontally. When you ask to go forwards or backwards, after an annoying delay this motor kicks in. The direction of the movement either pushes the tail boom up or down. This disbalances the centre of gravity and, hence, the helicopter moves forward and backward.
Up and down is simple - how fast are you moving those blades again?

The model is claimed to weigh 218g, though mine measured at 231g. This might be the metal shroud?
Unfortunately, the lightest digital camera I can find is 109g with batteries. I rubber-banded this to the base of the model and at full tilt it cleared the floor by barely an inch, threw the centre of gravity well off, and another crash&burn. Hmmm, will it even survive tomorrow!?

I'm thinking... there's another (el cheapo) digital cam around. Can I strip off the casing and any unnecessary optics? I ought to lose a fair bit of weight by dropping the batteries and running it tapped into the heli's cell. I'm not worried about the heli, for this camera is supposed to work off of AAAs. More of a worry is if 3.7V might be a bit much for the camera - I'll need to meter the battery to see what it is actually giving. Likewise, I'll need to see what happens if we go from standby to full throttle. Is the power supply fairly clean? Finally, what happens if the power drops out? I'm not worried if the MJPEG AVI is not written properly if it is possible to access what was previously recorded. I think you can with MJPEG, which is more than I can say for MPEG4 PVRs (if there's a power fail 59 minutes into an hour long recording, the entire recording is trashed, how lame!).

Who knows? I think the helicopter ought to be able to fly up to around maybe 250g (some testing will tell). While that is only 20g extra, removing the shielding and stripping the camera and using the Li-Ion instead of AAAs might make it viable? That'll no doubt be my project for this winter, asides from getting this thing balanced.

Later...

I took the opportunity to suspend the helicopter from some fishing line to check its centre of gravity. It seemed to me to hang slightly lower on the right, but the ruler says otherwise. It seems, actually, to be pretty well balanced. I suspended it by the nobbles on the lower rotor, and it hung straight.

I also took a picture of the cute little tail rotor.

Doing some research, it would seem that this model does not cope with the ground effect very well, having a tendency to drift backwards, spin, and try to roll over. The answer is to make a pretty sharp take-off to get it into the air. But, as I said above, I'm not confident enough with the controls to do that in an enclosed area. Maybe later, for while it may drift (look at how often the tail rotor is still), this YouTube video shows some pretty fine flying.
This one too, but if you look carefully it appears there is no tail motor, so I think the design is slightly different for the gyro model. Still, it's a well balanced budgie.

Finally, not the same model, but to show these things are fun, take a look at this. Note the nerdy-looking girlfriend, the pet bunny (!), and the freaky telly antenna. Oh yeah, and there's a model helicopter too. You can also watch the "girlfriend" flying a cute UFO helicopter, and note that knowing the right amount of throttle is extremely tricky - damn that thing is resiliant!

The weather tomorrow is supposed to be cloudy, but not raining. Okay, that's probably the kiss of death, but... We'll see...

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