We’re not entirely sure what to call this one. It’s got the usual trappings of a drone, but with only a single rotor it clearly can’t be called by any of the standard multicopter names. Helicopter? Close, but not quite, since the rotor blades are fixed-pitch. We’ll just go with “monocopter” for now and sort out the details later for this ducted-fan, thrust-vectored UAV.
Whatever we choose to call it — builder [tesla500] dubbed it the simultaneously optimistic and fatalistic “Ikarus” — it’s really unique. The monocopter is built around a 90-mm electric ducted fan mounted vertically on a 3D-printed shroud. The shroud serves as a mounting point for the landing legs and for four servos that swivel vanes within the rotor wash. The vanes deflect the airstream and provide the thrust vectoring that gives this little machine its control.
Coming to the correct control method was not easy, though. Thanks mainly to the strong gyroscopic force exerted by the rotor, [tesla500] had a hard time getting the flight controller to cooperate. He built a gimballed test stand to work the problem through, and eventually rewrote LibrePilot to deal with the unique forces on the craft and tuned the PID loops accordingly. Check out the results in the video below.
Some attempts to reduce the number of rotors work better than others, of course, but this worked out great, and we’re looking forward to the promised improvements to come.
While quadcopters seem to attract all the attention of the moment, spare some love for the rotary-wing aircraft that started it all: the helicopter. Quads may abstract away most of the aerodynamic problems faced by other rotorcraft systems through using software, but the helicopter has to solve those problems mechanically. And they are non-trivial problems, since the pitch of the rotors blades has to be controlled while the whole rotor disk is tilted relative to its axis.
The device that makes this possible is the swashplate, and its engineering is not for the faint of heart. And yet [MonkeyMonkeey] chose not only to build a swashplate from scratch for a high school project, but since the parts were to be cast from aluminum, he had to teach himself the art of metal casting from the ground up. That includes building at least three separate furnaces, one of which was an electric arc furnace based on an arc welder with carbon fiber rods for electrodes (spoiler alert: bad choice). The learning curves were plentiful and steep, including getting the right sand mix for mold making and metallurgy by trial and error.
With some machining help from his school, [MonkeyMonkeey] finally came up with a good design, and we can’t wait to see what the rest of the ‘copter looks like. As he gets there, we’d say he might want to take a look at this series of videos explaining the physics of helicopter flight, but we suspect he’s well-informed on that topic already.
It’s time once again to see how those tax dollars are spent, this time in the form of a “Data Entry Keyboard” manufactured by Hughes Helicopters. This device was built circa 1986 or so, and was used in the AH-64A Apache. Specifically, this panel would have been located by the gunner’s left knee, and served as a general purpose input device for the Apache’s Fire Control System. Eventually the Apache was upgraded with a so-called “glass cockpit”; consolidating various vehicle functions into a handful of multi-purpose digital displays. As such, this particular device became obsolete and was pulled from the active Apache fleet.
The military vehicle aficionados out there may know that while the Apache is currently a product of Boeing, it was originally designed by Hughes Helicopter. In 1984, McDonnell Douglas purchased Hughes Helicopter and took over production of the Apache, and then McDonnell Douglas themselves were merged with Boeing in 1997.
So it’s somewhat interesting that this device bears the name of Hughes Helicopter, as of the time it was manufactured, they would have been known as McDonnell Douglas Helicopter Systems. Presumably they had to work through existing stock of components that already had Hughes branding on them, leaving some transitional examples such as this one.
But you didn’t come here for a history lesson on the American military-industrial complex, you want to know about the hardware itself. So let’s crack it open to see what we can learn about this piece of aviation history.
Today, when we say “Jesus nut”, we’re not referring to the people who spend their days proselytizing down at the mall. The term, likely spawned in the Vietnam war, refers to the main nut holding the rotors on to the mast of a helicopter which is in the shape of the Christian cross. If the “Jesus nut” was to fail, the rotors would detach from the craft, and there would be little for crews to do except to pray.
The first step was to reconstruct the broken piece so it could be measured and then modeled in CAD software with the help of calipers to determine the original dimensions. What followed will be familiar to many 3D printing enthusiasts — a case of educated trial and error, experimenting with different filaments and print settings until a usable part was produced. [Marius] notes on the part’s Thingiverse page that they achieved the best print with an 0.2mm layer height, and printing two parts at once to allow the layers more time to cool during each pass. It was then a simple matter of tidying up the part with sandpaper and a drill bit before installing it on the vehicle.
[Marius] reports that the part was successful, being both strong enough to withstand the forces involved as well as having a fit that was just right to suit the rotor pin which needs to be able to turn freely within the Jesus nut. While they’re not always the right tool for the job, 3D printed replacement parts can sometimes surprise you. These prints that are used in repair work often don’t attract the same interest as printing cosplay armor, kinetic art, and low-poly Pokemon. But they quickly prove how transformative having a 3D printer, and the skills to use it, are. That’s why we’re running the Repairs You Can Print contest… take a few minutes to show off the really useful repairs you’ve pulled off with your 3D printer!
In this project, [Robert] is standing on the shoulders of giants, so to speak – we’ve seen others reverse engineer the S107G’s communications protocol before. [Robert] combined the efforts of several others to understand how to send commands to the helicopter, including use of two separate channels for controlling two at once.
It’s not the neatest, most lightweight way of building a new controller for your remote control toy, but it does show how quickly one can throw together a project in a weekend by combining modern hardware and software tools. Plus, it’s a great learning experience on a platform that’s been experimented with the world over.
It started life as a 1969 Bell OH-58 Kiowa (US Army Vietnam Assault helo) and had not only served in Vietnam but also for a federal drug task force. It was chopped up for parts and the body found its way to [SpeedyCop] and friends. The body now sits on an 80s Toyota van chassis, has a Mazda Miata rear suspension, and Audi 3.0 V6 engine.
The pontoons were originally added to hide the seam between the helicopter body and the van but they then inspired the idea of making it amphibious. And with the addition of a four-blade, 7000 RPM propeller from a parasail boat, the idea became reality, as you can see in the video after the break (we suspect the trailing line is a rope to pull it back to shore in case of engine failure).
At my university, we were all forced to take a class called Engineering 101. Weirdly, we could take it at any point in our careers at the school. So I put it off for more interesting classes until I was forced to take it in one of my final years. It was a mess of a class and never quite seemed to build up to a theme or a message. However, every third class or so they’d dredge up a veritable fossil from their ranks of graduates. These greybeards would sit at the front of the class and tell us about incredible things. It was worth the other two days of nondescript rambling by whichever engineering professor drew the short straw for one of their TAs.
One greybeard in particular had a long career in America’s unending string of, “Build cool stuff to help us make bad guys more deader,” projects. He worked on stealth boats, airplanes with wings that flex, and all sorts of incredibly cool stuff. I forgot about the details of those, but the one that stuck with me was the Cyclocrane. It had a ton of issues, and as the final verdict from a DARPA higher-up with a military rank was that it, “looked dumb as shit” (or so the greybeard informed us).
The Cyclocrane was a hybrid airship. Part aerodynamic and part aerostatic, or more simply put, a big balloon with an airplane glued on. Airships are great because they have a constant static lift, in nearly all cases this is buoyancy from a gas that is lighter than air. The ship doesn’t “weigh” anything, so the only energy that needs to be expended is the energy needed to move it through the air to wherever it needs to go. Airplanes are also great, but need to spend fuel to lift themselves off the ground as well as point in the right direction. Helicopters are cool because they make so much noise that the earth can’t stand to be near them, providing lift. Now, there’s a huge list of pros and cons for each and there’s certainly a reason we use airplanes and not dirigibles for most tasks. The Cyclocrane was designed to fit an interesting use case somewhere in the middle.
In the logging industry they often use helicopters to lift machinery in and out of remote areas. However, lifting two tons with a helicopter is not the most efficient way to go about it. Airplanes are way more efficient but there’s an obvious problem with that. They only reach their peak efficiency at the speed and direction for which their various aerodynamic surfaces have been tuned. Also worth noting that they’re fairly bad at hovering. It’s really hard to lift a basket of chainsaws out of the woods safely when the vehicle doing it is moving at 120mph.
The cyclocrane wanted all the efficiency of a dirigible with the maneuverability of a helicopter. It wanted to be able to use the effective lifting design of an airplane wing too. It wanted to have and eat three cakes. It nearly did.
A Spinning Balloon with Wings
Four wings stick out of a rotating balloon. The balloon provides half of the aerostatic lift needed to hold the plane and the cargo up in the air. The weight is tied to the static ends of the balloon and hang via cables below the construction. The clever part is the four equidistant wings sticking out at right angles from the center of the ship. At the tip of each wing is a construction made up of a propellor and a second wing. Using this array of aerofoils and engines it was possible for the cyclocrane to spin its core at 13 revolutions per minute. This produced an airspeed of 60 mph for the wings. Which resulted in a ton of lift when the wings were angled back and forth in a cyclical pattern. All the while, the ship remaining perfectly stationary.
Now the ship had lots of problems. It was too heavy. It needed bigger engines. It was slow. It looked goofy. It didn’t like strong winds. The biggest problem was a lack of funding. It’s possible that the cyclocrane could have changed a few industries if its designers had been able to keep testing it. In the end it had a mere seven hours of flying time logged with its only commercial contract before the money was gone.
However! There may be some opportunity for hackers here. If you want to make the quadcopter nerds feel a slight sting of jealousy, a cyclocrane is the project for you. A heavy lift robot that’s potentially more efficient than a balloon with fans on it is pretty neat. T2here’s a bit of reverse engineering to be done before a true performance statement can be made. If nothing else. It’s just a cool piece of aerospace history that reminds us of the comforting fact that we haven’t even come close to inventing it all yet.
If you’d like to learn more there’s a ton of information and pictures on one of the engineer’s website. Naturally wikipedia has a bit to say. There’s also decent documentary on youtube, viewable below.
Photo Credits: Rob Crimmins and Hal Denison
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