Re: veal

Pictures tell a story, this one the increasing credibility of these means of transporting people over reasonable distances in three dimensions. Featuring the revised layout of four power-units, I knew I was onto something when the guy running the studio ~ who rarely expresses an opinion ~ said that it looked more compact than anything else that had graced the floor. We seem to be getting nearer the point when people, not least of all me, might actually want one.

Not given up on red, but used black for the same reason most Formula One racing-car teams have done the same this season: as the native material colour it saves the cost and weight of paint.

Plus it did Ford no harm at all for the first several years.

36" Octocopter

Four-way connectors pay dividends at each corner of the airframe in the event of both octo and quad builds. In the case of the former then provide a nearly coincident locus for mounting contra-rotating propellers. For the latter they allow for the airframe to be leaned up against the garage wall when not in use ~ without damage to motors or propellers ~ when disconnected from the passenger cage. As the airframe is scaled up in size, this becomes a practical consideration.

Nonetheless as such connectors cost over a fiver each ex-VAT they won't be appearing in the forthcoming studio shot, thank you. Stubs included as seen here on the current airframe (featuring 750mm perimeter bars) would extend its foot-print to around 36" square, as against a smidgeon over 30".

Dread Locks

For a variety of reasons I don't like this as a satisfactory means of mounting motors, or at least in its current form, but principally because it increases the depth of the upper drone unduly when it comes to transporting it. I shall therefore revert to those lateral stubs pictured a few posts ago, extending fore and aft in the same plane as the frame itself. Worthwhile exercise in itself however and better to admit defeat now than after the show is on the road. The appearance of the overall frame I like a lot, the bedknobs not withstanding. At every stage in prototyping though you have to ask yourself firstly, "How practical is this?" besides the "Why am I wasting my life in this way?".

Mounting Tension

Tricky, but nonetheless doable. It's not perfectly level but then that is something that will come out in the wash during flight. The motor can also be unscrewed as a single unit for a quick change without tackling the four decidedly short-shanked fasteners, which is a bonus as those threads are easily stripped or cross-threaded. In fact it is not the ideal motor to work with, things being altogether less fiddly as they get that bit larger.

Note that I'm rigging the motors top-side too, as this makes the drone wholly easier to work on, set as it is around elbow-height. I shall be rigging it as a straight quad tho' as it will be evident to all concerned that the drone can as easily be configured as an X-8 octocopter by merely subbing a four-way tube-connector for the three-way seen here.

The frame at foot-level I've retained however, albeit minus the four stubs used to fix the motors in place. My gut-feeling is that an octocopter driven from top and bottom would be altogether more manoeuvrable than one with all eight motors top-side, tho' finding out is by no means an inexpensive exercise.

I think what we're trying to showcase here is that human beings can ~ and will ~ one day be lofted skywards in something not at all unlike a piece of street-furniture in the shape of a phone-box... and then my work, like that of Shane, will be done here.

Incidentally ~ as we're learning-by-doing ~ the one fly in the ointment in all this is that the wires do not emerge from the motor facing the way I'd want. Going forward this is solved by tightening the M8 foot-plate fully, and afterward removing and re-orienting the threaded tube-insert prior to fixing; better than leaving the motor-mount loosely tightened, when torque-reaction might loosen it altogether during operation.

Mounting Matters

Conventional wisdom tossed aside in the effort to build our off-the-shelf mega-drone, we turn now to motor mounts. I've used M8 office-furniture feet, which are delighted to be going flying instead of sitting around a cubicle. I've downloaded the spec for the U7 motor and scaled it to size by overlaying a 30mm (red) circle using Apple Pages, so as to print it and stick it to the foot-plate by way of a template. Centre punches to hand please, as the holes must be accurate; though you can drill them oversize if they don't quite align, as I know from bitter experience.

Meanwhile looking at YouTube there's a conversation going on amongst drone racers as to the benefit of 'soft mounting' methods of fixing motors with Scotch mounting tape. The reason for the ballyhoo is down to resonance, as the flight computer on a drone is sensing tilt hundreds of times per second, and adjusting motor RPMs to maintain the level. Should the airframe vibrate and flex, the motor itself might be rapidly tilted and this might fool the computer into thinking a correction is required; which may result in a self-reinforcing feedback loop which results in a loss of control.

This can be accommodated by PID tuning i.e. software response, though an easier way to dampen vibration is to use sticky-tape. PID stands for Proportional, Integrative, Derivative... which means as much to me as it does to you. Sadly aviation is beset with acronyms that people like to use in order to demonstrate their superiority in the field.

Whereas I'm just an ageing dirt-bag baby, who listens to Iron Maiden maybe.

Re: straint

A re-worked restraint (and eminently scaleable), viz. pair of U-channels riveted to the sides of the cage. The back-rest is fixed in place and the flight-control console is slid into position after pilot ingress. Note the locking pins (here a pair of unused rivets), which are essential in the event of bailing out. Checklist memory items, if you please?

    UPPER-DRONE MASTER SWITCH         .........................     CUT-OFF

    LOWER-DRONE MASTER SWITCH        .........................     CUT-OFF

    UPPER-DRONE FIRE HANDLE              .........................     PULL

    LOWER-DRONE FIRE HANDLE             .........................     PULL

    DRONE BALLISTIC PARACHUTE           .........................     ARM

    FLIGHT CONSOLE LOCKING PINS        .........................     REMOVE

    PERSONAL PARACHUTE HARNESS      .........................     SECURE

    AIR TRAFFIC CONTROL                      .........................     ADVISE

Re: Render

Occasionally it pays to post twice in a day, as I do here after a reconfiguration around the corners. Stubs for mounting motors are replaced by plinths and undercarriage legs are omitted, so that the outline of the drones is matching. It reduces the parts count, and improves ground-stability and general aesthetic: as a devotee of Apple I've always valued form and function equally. As important is the means of construction, and the use of stock product has meant that reiterative prototyping has been cost-effective as well as ecologically sound, beside eminently doable.

For those motor-mounts for instance I've switched back to sixteenth-gauge aluminium because it is more easily removable from the tube connectors ~ whereas those plastic sections that you see in black are so tight a fit as to require removing with a mallet. In fact at shorter lengths it can prove impossible to separate the two, in which cases you can steam them for a minute or two on the hob and let expansion do the trick.

This is nothing new in aviation: vital connections like the bearings that support 'swing-wings' are so tight a fit that they are cooled in liquid nitrogen at point of assembly so as to contract them sufficiently enough to fit. Fortunately more of us have a cooker to hand in the kitchen than, say, a liquefaction generator.

The 'tower' is made of metre-length tubes and I've retained a foot-square foot-print as a leftover from previous versions; as this is a half-scale prototype you and I would normally be looking at two-feet square. At the full-scale though I might switch to a half-metre (20"), because sheet material is often retailed in metric here in Europe...

...but mainly because it'll look more Marvel-ous.

Black Out

Okay so far as it goes but as ever am not entirely satisfied and figure it can be made more practical again... kind of feeling our way in the dark here. "How goes it?" types of review like this at each stage of the game are invaluable when it comes to the lessons to be learned. The study of static and dynamic loads is essential, it having accounted for the loss of a Space Shuttle, for instance, and what I don't like here is the load the lower drone is subject to by the weight of all that above.

You can see it in the flexing of those perimeter spars, albeit constructed in plastic as they are. This temporarily depressed me, and especially so after a week's work on the project, but as ever there will be a workaround. Taking comfort from the positives is essential in prototyping, and we can list these as being (a) it goes together quickly and easily (b) a pair of quads separated vertically appears to be credible and (c) I like the 'flight-deck' a lot.

The latter splits fore-and-aft to form a natural back-rest and safety-restraint, as well as a flight-control console. The foremost half is slid into position using U-section rails and locking-pins, whereupon it acts as a brace that reinforces the 'transporter' tower. The tower itself is self-contained, and therefore able to be detached from each drone. As yet these modules are loosely stacked, though aligned in place by use of four nubs on the surface of each drone which engage with holes in the floor and the roof of the tower itself.

Re: jig

By way of recap, decision was made to power up the transporter-style booth using an identical quadcopter at half-scale around both base and dome, the former doubling as a landing gear. Constructed in plastic throughout, each airframe can be assembled in less time than an IKEA coffee-table using only push-fit tube connectors and Allen key. Four-way connectors at each corner provide lugs for fast-fitment of motor-units.

The airframe retains the outline of previous prototypes whilst reducing foot-print and weight to a minimum: the configuration has the same capacity as the airframe in the background but reduces its foot-print by a third and its weight by over forty percent. Perimeter sections measure 750mm and the cantilevers 500mm, so that overall length is a nominal 1000mm and the width (without motors) is 800mm; the basic airframe weighing 2.0kg or 4.40 pounds. The centre-section remains 300mm square in support of stock transporters, however.

Next up the 'fitting out' of this lower drone with battery-packs, ESCs and motor-units. I've gone for black extrusions to avoid paint, and because people seem to take drones more seriously that way.

Henry Ford would be delighted.

Put out the Moon, and dismantle the drone.

For me this (final) effort to launch a credible personal air vehicle is a moonshot itself and so in order to give to the best chance of success in the longer term I retrieve the prototype in order to adapt it in three principal ways.

First, the 'Star Trek' model in the foreground has to go, if only to a museum. Carrying a third party for remuneration would require conventional flight certification, not overly cheaper in itself than an Apollo moonshot. Practically the market is for owner-drivers in the US, which has adapted its regulations to suit in the shape of the FAA's Part 103. In turn that means that a means of onboard control via sidesticks is the way forward.

Secondly if it is to be a pilot's machine it is going to need to be as manoeuvrable as a conventional helicopter, if not moreso. The only feasible way to do so in this case is to add a quadcopter at the base of the booth as well as around the dome, which pitches the centres of thrust and gravity around the mid-riff. This will give each of the drones the maximum purchase for flight-control motions.

Thirdly the adoption of that arrangement appearing at...

http://teledrone.blogspot.com/2023/01/30-by-12-inch.html

...so as to render the foot-print as compact as possible.

I order the parts accordingly, and principally in plastic.

Caution to the Winds

A few mods to be made before we commit to wiring and flying...