Monday, September 16, 2019

Post M'drone


Unseasonably warm after an inclement summer, so we're making hay while the sun shines.

The GoFly challenge asked for an official team photo and while we're not all there, those currently engaged are (in the shape of self and flight-engineer).

Whilst flying airliners in Cambodia I had outlined a 'flying phone-box' optimised for eVTOL.

Exceeding the GoFly dimensions at full scale however it was re-designed as a hollowed-out drone that was 'worn' around the waist.

The proximity of propeller blades and loads sustained by the operator were unlikely to meet safety criteria though unless an airframe was retained to re-arrange motors at a lower level.

This re-introduced the original concept whilst still retaining the compact foot-print achieved by fixing one drone around the operator.

Our next step is to get it airborne under the weight of batteries alone.

Onward and upward!

Wednesday, September 11, 2019

Drone or Phone?


There's nothing I can see in the guidelines for this competition that says anything about open rotors and their potential effect on either operator or bystanders and as we pointed out to Gwen last Friday, aeroplanes have used unguarded propellers since Leonardo and while many people have been killed by inadvertent contact with them, they still pass muster with every aviation authority in the world.

Useful parallels are cars, knives or (especially if you're American), guns. The first kill more people worldwide than any other means, followed by knives in places like London or guns in the USA. Nobody suggests doing away with them however because their utility outweighs the risks. But they were all introduced centuries ago and in a more litigious age products must be bullet-proof from the outset.

This has the interesting side-effect of steering people into dangerous pastimes like climbing high-rises without ropes, or launching themselves in wing-suits. We're here to build though and not philosophise, and I agree to the casual observer our wearable drones look like the sort of props magicians use to cut their assistants in half.

I have therefore decided to split the component drones again and mount one at the base and the other around the midriff. They'll be supported by a frame like that originally envisaged for the  'flying phone-box' so that once again the constraints of competition have steered us toward the safe and narrow.

On this note I get on with searching for parts, the pursuit of projects involving the trawl of internet and industrial units as it does. One such ends here where a vital part is described variably as aluminium or steel, which are metallurgically worlds apart, and more expensive the more you buy?

They say the website will be amended to reflect, but you know it never will, because that's life.

Monday, September 9, 2019

London Calling


Together with Pete Day I travelled to London Friday to meet Gwen Lighter, whose baby the GoFly Challenge is.

I forget to take a photo, at least until crossing Waterloo Bridge enroute to the station afterward.

The meeting worthwhile if only from the point of view that as it stands, the prototype in the previous post is unlikely to pass the safety scrutiny... from what I can gather due proximity of propeller blades and pilot.

Additionally, disquiet surrounds said pilot absorbing much of the shock of a heavy landing.

Issues to address as ever, as with life itself.

Seems 838 teams up for the competition but the organisers expect there'll be significant attrition enroute.

Let's hope we're not among the attrited.

(Spellchecker accepts the word, oddly).

Tuesday, August 27, 2019

Weigh-In


20 kilos on the spring balance, with the weight of the eight speed-controllers added. At 44 pounds that's around half of my original estimate for the mass of a competition airframe.

With jet-packs and parameters weighing in anywhere between 25 and 30 kilos that leaves us around a further fifty percent or 10 kilos to dedicate to battery-packs.

My guess is that isn't going to get us far, but getting us safely airborne represents first base.

Build it and they will come.

Sunday, August 25, 2019

Step Away From The Vehicle


There was a French philosopher who once said that anything looked at for long enough appeared absurd... might have been Marcel Duchamp?

When designing though I always think it's wise to step away from the vehicle overnight and look at it with fresh eyes in the morning. Paid off here because returning to the garage today I've grown used used to those eight legs and trying it on it's comfortable to walk around in.

In other words, it works ergonomically. What I've had to devise today is its ground-handling routines, because (a) those carbon-fibre propellers are sensitive as shins and (b) there's enough weight in the airframe to put your back out if you lift it without the right technique.

In that vein it is altogether easier to mount it on the tailgate for transport instead of the roof-rack. Having adapted the spare wheel mounting (an idea I've returned to a few months on) it's good to see that only the lowest pair of propellers require ties because the others rotate freely within the road-legal span of eight feet.

The airframe span with the rotors stowed as above is just 4 feet and 8.5 inches, whilst with the propellers freely-rotating their farthest tips span only 7 feet and 4 inches.

Saturday, August 24, 2019

Four Legs Good, Eight Legs Bad?


Learned a lot here about airframe geometry and the mounting of motors, beside the practicalities of ground-handling.

Looking at it now though I could go yet smaller and lighter, but that might be deferred until after power-testing with this one here.

Hard to say whether these eight legs offer any thrust-advantage over four mounted with paired propellers, but without setting both up on a test-rig then it's anyone's guess.

Certainly light enough to wander around in, and the ESCs are unlikely to add much weight.

Batteries will be something else though, but they're a job for another day.

Friday, August 23, 2019

Motor-vation


For reasons too tiresome to enunciate I've had to modify the engine-mounts to my liking and this has involved reducing the rotor-arms by four inches along with the associated clearance, although the tips still stop short of the flight-deck (which has yet to be armoured).

It reduces the airframe span to four foot eight and a half inches, which spookily matches the railway gauge on which the original passenger rail network was based (starting right here between Liverpool and Manchester).

Happily the potato-and-paint template method for centring the drill-holes has worked a treat, or at least on this first motor to have been mounted. I shall hold it there however on this fine evening which marks the start of the August holiday weekend in the UK. Experience has taught me to tackle precision jobs with a fresh head.

I have chosen too to modify the geometry with which each set of rotors is to be mounted viz. those on the lower quad will remain upright as seen here, while those on the upper rig will be inverted.

This creates a mirror image that minimises the depth of the airframe whilst maximising the vertical spread between propellers, obviating any chance of their blades colliding no matter under what duress.