Rebuild #24

For the purposes of the prototype at least I elect to mount the motors inverted on the upper quad... the upper quad itself may yet feature underslung power units in addition to top-mounted in order to provide a necessary failure redundancy for human carriage but for now it is more a case of extracting every last ounce of thrust from the motors we have available.

In all drones there are losses incurred from the imposition of cantilevers in the efflux of the propellers, and by mounting them underneath these losses are absolved. There may be losses incurred from having moved the uppermost propeller that bit nearer to the lower, but instinct suggests that these will be negligible.

The efflux from a propeller is shaped like the horn of a trumpet in that it progressively narrows on departure to form a column somewhat smaller in diameter. Manufacturers of motors caution that up to 25% of thrust might be lost when motors are mounted in pairs one above another.

The only research I have seen on this found that once the lower propeller is around a third or half of the propeller diameter removed, losses are diminished altogether. This suggests that once our propellers on upper and lower quad are separated vertically by at least a foot, there is nothing to be gained by removing them further.

This aside, following the disappointment of our last test-flight I pledged to return to the drawing board and both redesign and rebuild a prototype that has more than an evens chance of success ~ and within the course of a month.

And this is it.

Rebuild #23

Here's the finished motor-mount. You can see that for the studio shot the axis of each motor on the lower quad was mounted full-square on the undercarriage leg. I'm from Apple's philosophy of design and tho' aesthetically that may look better, this is a more practical means of fixing motors for flight-testing. Prototyping involves selling out at times along the way.

Rebuild #22

We enjoyed ourselves at the studio, didn't we, but then life's not all beer and skittles and it's time to replace our plywood motor-mounts with something more substantial. I note that I've been too economical with the length of the cantilevers and the upshot is ~ and this is the benefit of prototyping in the absence of computer aided design ~ that the X-braces leave less clearance for the propeller arcs than is desired.

Accordingly I set the axis of each motor on the inside edge of the cantilever an inch from the end, and fix an angle alloy to suit. I shall also file off the surplus alloy so that it matches the outline of the motor, for the sake of posterity: one day this will hang in a museum, as do two of our previous prototypes.

An advantage of offsetting the motors this way ~ and one from real-world experience of shifting these airframes around like furniture ~ is that it insets the propellers and thus protects them to some extent when the airframe is parked up against a wall or rolled on its side. Note the templates we are using, too. These were screen-saved from T-motor's tech spec and imported into Apple Pages where they were sized to suit prior to printing.

As I do all of this too, on the radio Seal is singing how, "In a world full of people only some want to fly, isn't that crazy?".

And he's right, isn't he?

Moon Shot

I take a couple dozen shots, though eventually select the first as representative of the species. Omitted are the batteries and ESCs (along with actual motors and propellers), because firstly they are elsewhere and secondly I wanted to exemplify the cleanliness and practicality of the design. Thanks are due as ever to Vessel Studios in Liverpool for the facilities.

Tuna Sub

With the motors and propellers still at the workshop nearest the flying field where the previous prototype was test-flown, I mock up their appearance for the benefit of a PR shot at the studio in Liverpool. Tins of tuna sub for motors and it matters not whether in spring water or oil. Propellers are fashioned from flooring laminate, twisted with a heat-gun before being stuck to the tins with bathroom silicone.

If you don't intend flying your prototype, these make for a cheap and tasty alternative.

Rebuild #21

Worth a pause now that the cross-braces are installed, which in the past when we've built similar airframes have prompted people to suggest that t looks vaguely like those TIE fighters that Darth Vader was apt to use during Star Wars... which I kind of like.

Next we've to turn our attention to the motor-mounts.

Zapata Airscooter

It's undoubtably good news that Franky Zapata has joined the fray, doubtless realising that the upfront and running costs of turbine jets are likely to cut the mustard for the PAV market. I did get to fly in a Harrier long since, and while the F35 jet fighter retains SVTOL capabilities, this is likely to be in order that it more easily be operated from off carriers.

Though it appears to be an octocopter, four of the arms include two propellers and so that makes a dozen... although as the TELEDRONE under development can be fitted with twelve motors too I'm relaxed about that. The outliers either side support hybrid motors that include petrol-engines in order to up the range, though whether they tilt forward is unclear from the ample arthouse renders that accompany the website.

Certainly with that airfoil at the rear ~ presumably intended to provide lift rather than merely stabilise flight ~ then there'd need to be some countervailing lift at the forward and and vectored thrust might fit the bill. On balance it looks unduly complicated and unlikely to fit through the garage door (though the colourful PR surely would).

Nonetheless with Ryse and Hexa too, personal air vehicles appear to be... on the rise?

Paul Kelly R.I.P.

September 5th of 1990, or thirty-three years ago according to the log-book that I last flew with the above, during an instrument flying-test out of RAF Woodvale; to where I return one more time in order to see his ashes scattered there during a slow fly-past. Not from this, I might add, but it was worth a picture by way of marking the date.

The engine I would have guessed was a Pratt and Whitney, but turned out to be by the Continental Motor Company according to the plate.

Rebuild #20

In some ways the airframe could be viewed as a biplane, and this is the conventional means of bracing the structure in order once again to provide the required stiffness. These are 1000 x 12 x 2mm carbon fibre strips and my only concession to the material as yet. (We've larger strips somewhere in the workshop at the flying field that can be subbed on the day). They are attached where the 6mm end-bolts secure the cross-spars at the leading and trailing edges of the panniers, with the overhangs ground off; whilst a pop-rivet connects the pair at each centre-point.

Rebuild #19

Add a cover for the avionics bay in the shape of the conventional dome of the classic GPO phone-box. We'll 'go commando' during testing with flight-controller uncovered, but retain the branding for the PR push.

It being that it will do what it says on the tin: teleport people by drone.

Rebuild #18

In the 'capping out' ceremony (for which local dignitaries were here in attendance), an aluminium panel spans the top-side of the vehicle. It is here where the 'dome' of the telephone-box will be fitted, housing an avionics bay that includes a controller tasked with steering the vessel. After the ceremony I thanked all assembled and celebrations continued at a local Subway, where steak and cheese subs were enjoyed by all.

Rebuild #17

With the airframe upright again, pack your 1" (actually 25mm here in Europe) insulation foam into the panniers on either side of the passenger booth, as we did for the lower quad earlier. Note that the upper quad lies flush with the top end of the booth, so as to maximise the headroom without extending the overall height of the vehicle unduly.

Rebuild #16

A momentous occasion as wing-bolts securing upper quad and passenger-booth are hydraulically riveted into place in the workshop. These enormous brackets are forged in a Czech foundry, before being shipped to the UK and sold by the dozen at Screwfix.

Rebuild #15

With the pilot's booth in situ and the spars bolted together (including cross-members adjacent the booth itself), apply the 0.5mm panels either side. You'll get through a lot of 4 x 12mm pop-rivets in all of this ~ and I often buy the full box of 1000 pieces ~ but then remember there's three-quarter million rivets in a 747 and three million in what is left of the Titanic. And when you think about it, both were a resounding success... not least in the latter's case for being the only ship most of the world has heard of.

Proto Typing

Both the helicopter and the first practical VTOL jet in the shape of the Harrier took to the skies in the form of an inexpensive space-frame, the 'flying bedstead' in the case of the latter. TCab's flying taxi will look very much like Vertical's once complete, which begs the question as to why complete it prior to flight-testing, as the latter effectively did (along with most others)?

The PR value of producing the finished article ~ at least from outward appearances ~ is inestimable in the race for funding. And although there is a negative effect in seeing it wrecked on the ground, that funding was already in the bag in Vertical's case. Call it wealth destruction if you like, but then it's other people's wealth after all.

Another aspect of TCab's recent test-flight of note is that the motors are undergoing certification, which means that they're rigorously tested for reliability prior to fitment. This has long been the norm in aviation (and the motor manufacturer Safran claim to have built the original aero-engines at turn of last century), but conspicuously absent until now in the production of the sort of motors designed to produce eVTOL aircraft.

There are two sides to certification. On the one hand it provides motors with reliability effectively guaranteed... except that it doesn't, or at least prior operational experience. The world's most reliable machine ever in the form of the CFM56 (which I've operated on both Boeing and Airbus types), was among the least reliable upon service entry. As well as this, it should be pointed out that invariably what fails in eVTOL testing is not generally the motors anyway.

What creeping certification does, at least as it will inevitably work its way down the scale, is to greatly increase the cost of development for no apparent gain in reliability. It has, however, inevitable if only because technological evolution in the modern world  trends toward absurd levels of risk avoidance on the one hand, which plays itself on the other to the larger corporations that rule our world in cahoots with the finance houses.

Thus it is that Vertical Aerospace ~ love-child of someone who'd made his millions in the privatised UK energy market ~ is that much more likely to succeed than are we.

And that's just the way it is... some things will never change.

Rebuild #14

We don't have the luxury of CAD/CAM to locate the various holes that need drilling out and so the ideal way to construct the upper quad is turning the air vehicle on its head and using it as a jig.

There are days I don't feel like doing any of this, and just getting started is challenging. Though I find during the course of the build that what emerges looks increasingly right or altogether less so; and as this shapes up I feel increasingly confident that it will look equally good at full scale.

Rebuild #13

Colour-wise I've gone for drab olive, as I've only the camouflage top for the mannekin. The skids are plastic extrusions bolstered by wooden section inserts at the points that they are fastened to the lower quad with 8mm countersunk bolts. Be cracking on with the upper quad next.

Peter Beck, whose business literally is rocket science, said whatever you build should be beautiful: for in that event the time was never wasted whether it work or not. And rockets, like eVTOLs, only work as often as not during their development and testing.

Creative Destruction

Wouldn't be he first prototype they've written off but then they ~ like us ~ are in good company, the evolution of aviation having been one of trial-and-error. Along with Bell, Boeing and Joby ~ whose prototypes each suffered similar fates along the way ~ Vertical benefits from investment more easily expressed in billions of dollars than in millions; although such investment is a monkey on your back, 'due diligence' requiring all such reversals to be declared.

Rebuild #12

I've been hauled over the coals by the head of PR for allowing a toilet bowl to feature in the previous post, and in view of the fact I am the head of PR that was quite a feat. But here I've added a back to the 'phone-box' if for no other reason than a return to our roots. Actually it does, at the cost of a little weight and material cost, add again significantly to the rigidity of the whole. And as no one else out there appears to be trying to fly people bracketed by a pair of drones, we need all the rigidity we can get.

Rebuild #11

Elect to mount the motors direct to the alloy cantilevers for minimum flexure, and opt for skids at the same time. To accommodate all of which I lower the footwell to 4 inch depth, which improves the overall proportions.

Rebuild #10

Here's the box secured to the lower quad. The cantilevers are terminated at three-way connectors that provide for a motor pylon at the corners, with the total weight of the payload carried through the airframe at rest (allowing for a higher drone altogether). Happily though the mannekin is split into halves and can be flown like Douglas Bader with legs either on or off... else absented altogether, which makes for flexibility at the flight-testing stage. Those undercarriage legs incidentally can be fitted with skids, but I can't be bothered buying any more plastic tubing for now.

Target weight suggested by the gurus back at the lab was twenty kilos, and what you see here weighs just seven. I could have added a back to the 'phone-box' in order to stiffen things further, but we'll keep that one up our sleeve at present. As it is, ingress might be from any side of the vehicle, and that step into the foot-well is scaled at the ten-inch (25cm) mark, which is as good as my old knees get at this stage of the game.

Rebuild #9

Fit the split 'flight-deck' and secure the mannekin. Ordinarily much of the front of the box would be open in order that the operator may step back into it and secure around the waist using the forward half of that deck, which also serves to brace the airframe.

Rebuild #8

Using a home insulation product, line the interior of the box using a spray-on glue and a filet of silicone at the corners. This does wonders for rigidity without adding unduly to the weight (and even those wings carrying people into space nowadays are skinned foam fabrications). In reality at full scale this won't be a closed compartment because access has still to be accommodated for ingress by stepping back into the booth from out front.

Note the orientation arrow is duplicated up top prior to its being covered at the base!

Rebuild #7

Add side panels to the accommodation booth, to a height of around 16" in this case, as the booth is around three feet high so as to scale to nearer six. As a representative ergonomic model I chose the average height of the Great British female, which stands at 5' and 3". The mannekin therefore has now to identify as a woman, which we can only applaud as our modest contribution to Pride Month. Sadly (s)he has no hair, and has also to identify as a woman of average height challenged by Alopecia Totalis. Building drones is a whole lot more involved than I'd ever imagined.

Rebuild #6

Add the uprights to the base and dome sub-frames, a point at which the phone-box is able to be tailored to the size of the operator... "Suits you, Sir!".

Rebuild #5

Use the remainder of the half-dozen tube-connectors to assemble the sub-frame for the dome of the phone-box, marking this up for final orientation in the same way due our working to the nearest couple of millimetres tolerance. I've stuck with super-light plastic for the passenger 'transporter' as we're working to around a twenty-kilo limit.

Rebuild #4

Now's a good time to fit the base to the phone-box, with a handful of 4mm pop-rivets and a smear of silicone around the inside edges to firm things up. I should have used black, but used one left over from recent work in the downstairs cloakroom instead.

Rebuild #3

With the shear webs attached to the panniers either side, now's time to fit the made to measure phone-box for transporting the passenger. To ensure that it's going to slide into the lower quad, cut the plastic tubing to suit and assemble the base of the box in situ like this by using three-way connectors. Note that the drone and passenger booth have been marked up as to direction of travel in order that everything fits prior to final assembly.

Rebuild #2

Taken the oppo to reduce the phone-box insert to 11" square, although when I've built something similar at full-scale (albeit stretching only to elbow-height), lesson learned was that it can be wider than it is deep: me like many others being that shape myself. Here it gives those propeller disks all the clearance they need from the superstructure while at the same time looking better proportioned altogether... those holes down the sides are exactly one third (12") in. I packed the voids out too with left-over insulation from a partition wall, as it ups its overall rigidity without increasing its weight unduly.

Rebuild #1

A quick mock-up to ensure it'll all fit together. 36" cantilevers connected by inch-alloy sections cut down to 750mm to allow for the M6 tube-inserts to accommodate bolts. Either side of the booth are inch-square plastic extrusions taken down to 295mm to suit the same tube-inserts. Although these brace the airframe they are non-structural and serve principally to retain the inch-thick insulation foam that will be used to pack out the voids prior to application of shear-webs top and bottom. These to be identical so that the lower quad can be raised around the box to some extent prior to fitment in order to provide ground clearance for the props. All in all a promising start, and as ever, starting is invariably the hardest part. Well done, Colin.

A Very Good Place to Start

Revisit the 1/10th scale draft in Apple's Pages on the basis of 'Measure twice, cut once' and indeed there are dimensional errors that require correcting among our outline of the lower quad. A point to notice in these documents is that the software dimensions each element to the centreline of each object, so that where we've tubular sections of around 1" (or 5-point in typeset with), the width of the tube itself will add a half-inch in excess of the drafted measure.

That said, all of these are outside dimensions, the extended length of the cantilevers being attributable to an extra 2" to mount the motors, plus a further 1" to represent the right-angle tube connector that will provide a stub undercarriage at each corner, upon which either skids or simple feet will be mounted. The weight at these points will be considerably relieved why the fact that the payload in the shape of mannekin, phone-box accommodation and upper quad will be 'nested' with the 12" aperture at the centre-point prior to fixing in place.

The aims of the rebuild are to shorten and stiffen the 'phone-box' whilst rendering the airframe altogether more rigid at the same time, in order for the flight-controller not to be countered in its operation by undue flexure. We shall look at a draft upper quad in the subsequent post.

Meantimes the GoFly Challenge and its million-dollar prize remains open 'til the 26th of next month, by when I expect some traction at a half-scale at least, albeit any hope of competing for anything at full scale remains a distant prospect as yet. Nonetheless anyone designing air vehicles with distributed electrical propulsion need consider this: every aspect of the software and hardware can only improve year upon year in order to simplify the task of building a practical personal flyer, whilst the only static variable remains the aerodynamics.

Accordingly, should we achieve a full-scale beta-product in the months ahead then its prospects will only improve in the period beyond and not least with operational usage.

A Stroll Around the Lower Quad

As we re-focus on a rebuild of the double-decked octocopter, there are benefits to be derived from our excursion into a more conventional layout a few posts back:

http://teledrone.blogspot.com/2023/07/the-maltese-falcon.html

Specifically, the inclusion of a central void in the lower quad allows for the phone-box to be inset, so that its weight will be supported whilst the air vehicle is at rest on the ground. Bear in mind that in flight the burden of the payload is split 50/50, tho' before lift-off the lower quad has to support 100% of the gross weight.

This is alleviated altogether if the phone-box is tasked with supporting the weight the upper quad, along with that of the passenger. In turn this means that the lower quad can be altogether lighter. At the same time it means that the lower set of propellers may still be raised to some extent clear of the ground, so as to avoid the prop-strike hazard that inevitably attends an air vehicle with a proportion of its power around its base.

All will become clear, however, once construction is recommenced.

Fuck, Fuck, Fuckety-Fuck.

The prevailing view from the lab is that we should persist with what we've got, viz. a caged operator vertically flanked by a pair of drones... and in truth it's rather been our USP throughout five years of back-and-forth. After ten hours of travel in torrential rain so typical of an English summer, we therefore have to re-build around aero-dynamics rather than those of a US patent application. Talk you through it as ever, step-by-step.

Cage Flight

Recovery and rebuild of half-scale octocopter to commence as of, in accordance with the allowable claims within the US patent application: focused on independent means of elevating the drone freely around the passenger compartment to engage and launch it into the air. An aspect of the development of the airframe is that it may be arrested either at elbow height, or the overhead and therefore tested for manoeuvrability either way. Undoubtedly that configuration offering the maximum is preferred at this outset.