My Work Here is Done

I re-abandon the idea of testing the prototype in the absence of the phone-box, and by the end of last week had effectively gone as far as I felt inclined. Without mentioning the Titanic I would compare this stage to that prior to 'fitting out' as it applied to shipbuilding... the moment the hull is launched (or wheeled from the hangar in my case) ready for its luxury superstructure to be applied.

This will take the form here of wiring up the electronic components and programming the associated parameters for flight. As per the launch of a ship, what you see here is equipped with the equivalent of the coal-bunkers and steam-engines, except in the form here of Lipo battery-packs and electric-motors.

I would have liked a pack to address each of the eight motors, but the fact we'd already invested in a pair of seven-cell packs suggested it were better to invest in a further pair to suit the top-end of the vehicle. As the prototype is over-powered in its current form ~ flying only a Mothercare mannekin in lieu of a human being ~ a pair of six-packs would prove to be sufficient.

Despite the lockdown I managed to source these off-the-shelf at Alien Power Systems, a company recommended me by Pete Bitar in the 'States and which proved serendipitously to be only a half-hour drive in the car to collect. Alien is my sort of enterprise, begun a man who arrived from Italy and worked in a restaurant prior to founding a successful operation that does business world-wide.

I also speak to the man who established DJI in the USA (a marriage made in heaven). He advises that with many hundreds of eVTOL efforts abounding on YouTube that it's no longer enough to get some sort of proof-of-concept airborne, but rather to prove that for whatever reason it is proven to be superior flight solution.

I'm confident this is, but that would be like Edmund Hillary saying at base camp that he was confident of climbing Everest. He did so too, but there was much between 'here and there'.

Flying Bedstead

I re-visit a previous notion (search 'jury rig' here) armed now with the knowledge derived in recent days regards how to put this thing together. The drones now feature brackets around the outside corners of the centre-body with which the passenger booth can be secured with an external set of tie-rods.

The nice thing about transferring the load to the outsides of the structure (as the engineer Peter Rice pioneered with iconic buildings like the Centre Pompidou in Paris or the Lloyds of London headquarters) is that it is flying-friendly and in many ways takes us back to the earliest development of bi-planes, when you'd 'kick a tire and twang a wire' prior to flight.

A by-product of this development so far as the drone is concerned is the the payload can be swapped out for what is effectively a 'spacer' that separates the two drones ready for wiring and subsequent flight-testing.

It therefore references Rolls Royce's own vertical-lift test-bed, with the exception being that the drone here is as yet uninhabited. This I can accede to fairly readily, the original "flying bedstead' having accounted for at least one Wing Commander during flight trials.

The prototype is thus ready for delivery and officially 'ex-Works' as of today, from whence it will be transported upon the roof of the Jimny to the project's electrical engineering facility.

Devil's in the Details

Working my way through fitting out each drone prior to incorporating the passenger booth. This includes a double skin on the centre body of each, as I notice a degree of bowing on the lower once loaded up... which is unsurprising as this is the lightest gauge of alloy tubing that I am using ~ I started out building these prototypes at the heaviest and working backwards before working in the opposite direction, if only in view of the budget.

I also add battery trays to the upper drone as I want a pack to address each pair of rotors left and right, although this will involve a considerable outlay on the additional packs of Lipo. I add brackets too at the point I figure is best to mount the electronic speed controllers (ESCs)  before realising they will have to be relocated... though there has been endless construction and deconstruction from the outset.

The reason for having to relocate said brackets is that I discover there is a sufficient length of lead to connect the lower ESCs to the flight controller mounted on the upper drone. In effect this means that the upper drone will be the 'brains' and the lower the 'brawn' that will work in tandem (occupying as it does a literal and figurative lower level in the workplace).

Re: dux

This taken on Saturday May 2nd, and so effectively April has seen the prototype redesigned and rebuilt from the ground up, and single-handedly. Considering this is less than two months since the previous iteration appeared at the event in California ~ and during a national lockdown that saw the UK population effectively curfew throughout most of the period ~ then I can be justifiably proud.

All the elements are now in place. I had built an identical frame to that of the drones purely to support the undercarriage (by placing it under the lower), but this weighed an extra six pounds and seemed like an unnecessary indulgence. In the event therefore I lengthened the cantilevers by six inches to support each castor. I had wanted them fixed directly beneath the lower set of motors, but this only complicated the assembly and disassembly of each of these components and I prefer to err on the side of simplicity. It doesn't look to bad, and in fact adds that much more protection to the lower set of propellers.

Plan is these will be arrested and lined up with the lower frame during take off and landing anyway, so as not to leave them exposed. We totalled a pair of these at said event, at a cost of the best part of three hundred pounds as I recall.