If you are a watcher of the world of drones, or multirotors, you may have a fixed idea of what one of these aircraft looks like in your mind. There will be a central pod containing batteries and avionics, with a set of arms radiating from it, each of which will have a motor and a propeller on its end. You are almost certainly picturing a four-rotor design, such as the extremely popular DJI Phantom series of craft.
Of course, four-rotor designs are just one of many possible configurations of a multirotor. You will commonly see octocopters, but sometimes we’ve brought you craft that really put the “multi” in “multirotor”. If the computer can physically control a given even number of motors, within reason, it can be flown.
There is one type of multirotor you don’t see very often though, the trirotor. Three propellers on a drone is a rare sight, and it’s something we find surprising because it’s a configuration that can have some surprising benefits. To think about why, it’s worth taking a look at some of the characteristics of a three-rotor machine’s flight.
We have all been beneficiaries of the boom in availability of cheap imported electronics over the last decade. It is difficult to convey to someone under a certain age the step change in availability of parts and modules that has come about as a result of both the growth of Chinese manufacturing and Internet sales that allow us direct access to sellers we would once only have found through a lengthy flight and an intractable language barrier.
So being able to buy an ESP8266 module or an OLED display for relative pennies is good news, but there is a downside to this free-for-all. Not all the products on offer are manufactured to legal standards wherever in the world we as customers might be, and not all of them are safe to use. We’ve all seen teardowns of lethal iPhone charger knock-offs, but this week the ARRL has highlighted an illegal import that could take being dangerous to a whole new level as well as bring an already beleaguered section of our community to a new low.
The products the radio amateurs are concerned about are video transmitters that work in the 1.2GHz band. These are sold for use with FPV cameras on multirotors, popularly referred to as drones, and are also being described as amateur radio products though their amateur radio application is minimal. The ARRL go into detail in their official complaint (PDF) about how these devices’ channels sit squarely over the frequencies used by GLONASS positioning systems, and most seriously, the frequencies used by the aircraft transponders on which the safety of our air traffic control system relies.
The multirotor community is the unfortunate recipient of a lot of bad press, most of which is arguably undeserved and the result of ignorant mass media reporting. We’ve written on this subject in the past, and reported on some of the proposals from governments which do not sound good for the enthusiast. It is thus a huge concern that products like those the ARRL is highlighting could result in interference with air traffic, this is exactly not the association that multirotor fliers need in a hostile environment.
The ARRL complaint highlights a particular model with a 5W output, which is easily high enough to cause significant interference. It is however just one of many similar products, which a very straightforward search on the likes of AliExpress or eBay will find on sale for prices well under $100. So if you are concerned with multirotors we’d urge you to ensure that the FPV transmitters you or your friends use are within the legal frequencies and power levels. We’re sure none of you would want an incident involving a manned aircraft on your conscience, nor would you relish the prospect of the encounter with law enforcement that would inevitably follow.
When a claim is made for something being the world’s lightest it is easy to scoff, after all that’s a bold assertion to make. It hasn’t stopped [fishpepper] though, who claims to have made the world’s lightest brushless FPV quadcopter. Weighing in at 32.4 grams (1.143 oz) it’s certainly pretty light.
The frame is a circular design cut from carbon-fiber-reinforced polymer, and on it are mounted four tiny brushless motors. In the center are the camera and battery on a 3D printed mount, as well as custom flight and speed controller boards. There are a series of posts detailing some of the design steps, and the result is certainly a capable aircraft for something so tiny. If you fancy experimenting with the design yourself, the files are available for download on the first page linked above.
There are two aspects to this build that make it interesting to us. First, the lightest in the world claim. We think someone will come along with something a bit lighter, and we can’t wait to see a lightest multirotor arms race. Good things come of technology races, which brings us to the second aspect. Governments are busy restricting the use of larger multirotors, to the extent that in some parts of the world all that will be available for non professionals will be sub-200g toy craft. Any project like this one which aims to push the boundaries of what is possible with smaller multirotors is thus extremely interesting, and we hope the community continue to innovate in this direction if only to make a mockery of any restrictions.
All over your TV and radio this morning if you live in the UK is the news that the British government is to hold a consultation over the licensing of multirotors, or drones as they are popularly known. It is being reported that users will have to sit a test to acquire a licence before they can operate any machine that weighs above 250 g, and there is the usual fog of sloppy reporting that surrounds any drone story.
This story concerns us on several fronts. First, because many within our community are multirotor enthusiasts and thus we recognise its importance to our readership. And then because it takes as its basis of fact a series of reported near misses with aircraft that look very serious if taken at face value, but whose reported facts simply don’t match the capabilities of real multirotors. We’ve covered this issue in the past with an incident-by-incident analysis, and raised the concern that incident investigators behave irresponsibly in saying “It must have been a drone!” on the basis of no provable evidence. Indeed the only proven British collision was found to have been with a plastic bag.
Of course irresponsible multirotor fliers who threaten public safety should be brought to book. Lock them up, throw away the key, whatever is appropriate. But before that can be done, any debate must be conducted on a level playing field. Our final concern is that this is an issue which is being framed almost entirely on the basis of one side’s interest groups and hysteria on the part of the uninformed about a new technology, rather than a balanced examination of the issues involved. It’s the old “People are having fun. This must be stopped!” idea that infects so much lawmaking, and it’s not very pretty.
Fortunately while it is being reported in some quarters as a done deal as in “Drone fliers must sit a test”, in fact this story is “The Government will ask people what they think about drone fliers sitting a test”. It’s a consultation, which means a Parliamentary committee will sit down and hear evidence before deciding on any legislation. The good news about consultations is that they are open to submissions from the general public, so if you are a British multirotor flier you can submit your own arguments. We will keep you posted with any news about the consultation as we have it.
If you hail from somewhere to which Australian beers have been exported, you could be forgiven for forming a view of the country based solely on TV adverts for Foster’s, or Castlemaine XXXX. Entertaining 30-second stories of wily young Aussies, and their inventive schemes to get their hands on a cool glass of the Amber Nectar.
From one perspective the video of the event which we’ve posted below the break is a very entertaining film. We see the flight over houses and a main road to a local branch of Bunnings, an Australian hardware store chain. Their sausage sizzle is a weekly institution in which local non-profit groups sell barbecued sausages from a stall in the car park as a fundraiser. The drone lowers a bag on a string over people queuing, with a note saying “Please buy snag(Aussie slang for sausage) and put in bag, here’s $10”. Someone complies, and the tasty treat is flown back over suburbia to our hero in his tub. It’s fairly obviously a production with many takes and supporting actors rather than a real continuous flight, but the Australian Civil Aviation Safety Authority is nevertheless investigating it. Breaches of the rules are reported as being use of a drone within 30 metres of people, as well as flight beyond the line of sight and over a populated area. The original video has been taken down, but it lives on courtesy of Australian tech site EFTM.
Aside from providing our readership with entertainment courtesy of our Australian friends there is an important message to take away from this story. It’s likely that if they can adequately prove that their flight was never out of the line of sight they can escape some of the charges, but even so they have strayed into difficult territory. We’ve written about drone hysteria on the part of authorities before, and we are living in an age during which twitchy agencies have shown themselves willing to view what we know to be little more than grown-up toys as something akin to terror weapons. Of course people who use multirotors for wilful endangerment should be brought to book in no uncertain terms, but the line between that and innocuous use feels sometimes to have been shifted in an alarming direction. Please keep entertaining us with your multirotor exploits and hacks, but never take your eye off how what you are doing could be misconstrued by those in authority. We’d prefer not to be writing up drone stories involving fines.
The mass media are funny in the way they deal with new technology. First it’s all “Wow, that’s Cool!”, then it’s “Ooh, that’s scary”, and finally it’s “BURN THE WITCH!”. Then a year or so later it’s part of normal life and they treat it as such. We’ve seen the same pattern repeated time and time again over the years.
Seasoned readers may remember silly stories in the papers claiming that the Soviets could somehow use the technology in Western 8-bit home computers for nefarious purposes, since then a myriad breathless exclusives have predicted a youth meltdown which never materialised as the inevitable result of computer gaming, and more recently groundless panics have erupted over 3D printing of gun parts. There might be a British flavour to the examples in this piece because that’s where it is being written, but it’s a universal phenomenon wherever in the world technologically clueless journalists are required to fill column inches on technical stories.
The latest piece of technology to feel the heat in this way is the multirotor. Popularly referred to as the drone, you will probably be most familiar with them as model-sized aircraft usually with four rotors. We have been fed a continuous stream of stories involving tales of near-misses between commercial aircraft and drones, and there is a subtext in the air that Something Must Be Done.
Are multirotors unfairly being given bad press? It certainly seems that way as the common thread among all the stories is a complete and utter lack of proof. But before we rush to their defence it’s worth taking a look at the recent stories and examining their credibility. After all if there really are a set of irresponsible owners flying into commercial aircraft then they should rightly be bought to book and it would do us no favours to defend them. So let’s examine each of those incident reports from that BBC story.
[marhar] was pretty confident in his quadcopter building skills when he made a bet to build and fly a quadcopter in just one hour! This is a big task but he saved valuable time by using some unlikely parts that were hanging around his parts bin. And to make the task a little more difficult, this build wasn’t done in a nice shop, either. It was built outside on a patio floor with the only power tools available being a hand drill, miter saw and small drill press!
The frame is made from cheap, sturdy and available scrap wood. The center plates are 1/4″ plywood and the arms are 3/4″ square fir strips. Notice the landing gear, yes, those are mini wiffle balls zip-tied to the wooden arms. Although an unlikely candidate for landing gear, they are surprisingly effective.
The flight controller board is an Ardupilot. [marhar] did use a flight controller that he previously had in another quadcopter. He used it as-is, and it worked, but no programming or configuration time is included in the 1-hour limit. Even so, it doesn’t take away from the impressiveness of the build time. The motors, ESC’s and battery are just standard types used for most multirotors.
[marhar] doesn’t say what he won for completing the ‘copter but we hope it was something good, he deserves it. If you’d like to make something similar, [marhar] gives very detailed instructions and provides templates for the wood parts on his Instructables page. Check out the time-lapse build video after the break…