Large Tip Driven Copter Turns Very Slowly

August 8, 2022 by Danie Conradie 21 Comments

Picking propeller size for any aircraft, but especially VTOLs, it’s a tradeoff between size and RPM. You can either move a large volume of air slowly or a small volume of air quickly. Small and fast tend to be the most practical for many applications, but if you’re thinking outside the box like [amazingdiyprojects], you can build a massive propeller and make it fly at just one revolution per second. (Video, embedded below the break.)

One of the challenges of large propellers is their high torque requirements. To get around this, [amazingdiyprojects] drives the 5m diameter propeller from the tips using electric motors with propellers. The blades are simple welded aluminum frames covered with heat-shrunk packing tape, braced with wires for stiffness.

The flight controller, with its own battery, is prevented from spinning with the blades by counteracting the spin of a small DC motor. Each blade is equipped with a servo-driven control surface, which can give roll and pitch control by adjusting deflection based on the blade’s radial position.

[amazingdiyprojects] control setup is very creative but somewhat imprecise. Instead of trying to write a custom control scheme, he configured the old KK2.15HC flight controller for a hexacopter. Each control servo’s PWM signal routes through a commutator disc with six sectors, one for each motor of the virtual hexacopter. This means each of the servos switches between six different PWM channels throughout its rotation. To compensate for lag when switching between channels, [amazingdiyprojects] had to tune the offset of the commutator disc otherwise it would veer off in the wrong direction. After a second test flight session to tune the flight controller settings, control authority improved, although it is still very docile in terms of response.

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Solar Plane Might Be Able To Last Through The Night

August 6, 2022 by Danie Conradie 15 Comments

“Just add solar panels to the wings” is a popular suggestion for improving the flight times of fixed-wing drones. However, the reality is not so simple, and it’s easy to hurt rather than help flight times with the added weight and complexity. The team at [Bearospace Industries] has been working on the challenge for the while, and their Solar Dragon aircraft recently had a very successful test flight, producing about 50% more power than it was consuming.

Instead of just trying to slap solar panels to an existing plane, an airframe should ideally be designed from the ground up as a balancing act between a range of factors. These include weight, efficiency, flight envelope, structural integrity, and maximum surface area for solar panels. All the considerations are discussed by [Bearospace] in an excellent in-depth video, which is an indispensable resource for anyone planning to build a solar plane.

[Bearospace] put all the theory into practice on Solar Dragon, which incorporates over 250 W of high-efficiency Maxeon C60 solar cells on the wing, tail, and triangular fuselage. The cells were wired to match their maximum power point voltage as closely as possible to the plane’s 3S lithium-ion battery pack, enabling the solar cells to charge the battery directly. To prevent overcharging, a solid state relay was used to disconnect the solar cells from the battery as required.

The batteries maintained the same average state of charge during the entire one-hour late morning flight, even though the panels were only connected 65% of the time. The team expects they might be able to get even better performance from the cells with a good MPPT charger, which will be required for less than ideal solar conditions.

Solar Dragon has a much larger payload capacity than was used during the test flight, more than enough for an MPPT charger and a significantly larger battery. With this and a long list of other planned improvements, it might be possible for the Solar Dragon to charge up during the day and fly throughout the night on battery power alone. One interesting potential approach mentioned is to also store energy in the form of altitude during the day, and use the aircraft’s slow sink rate to minimize battery usage at night.

Solar planes come up every few months on Hackaday, with [rctestflight] being one of the usual suspects. You also don’t need solar panels for long flight times, as [Matthew Heiskell] proved with a 10-hour 45 minute flight on battery power alone.

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R2Home Is Ready To Bring Back Your High Altitude Payload

August 1, 2022 by Danie Conradie 23 Comments

With high-altitude ballooning, you are at the mercy of the winds, which can move your payload hundreds of kilometers and deposit it in some inaccessible spot. To solve this [Yohan Hadji] created R2Home, an autonomous parachute-based recovery system that can fly a payload to any specified landing site within its gliding range.

We first covered R2Home at the start of 2021, when he was still in the early experimental phases, but the project has matured massively since then. It just completed its longest and highest test flight. Descending autonomously from a release altitude of 3500 m, with an additional radiosonde payload, it landed within 5 m of the launch point.

R2Home electronics with it's insulated enclosure — R2Home electronics with its insulated enclosure

R2Home can fly using a variety of steerable canopies, even a DIY ram-air parachute, as demonstrated in an earlier version. [Yohan] is currently using a high-performance wing for RC paragliders.

A lot of effort went into developing a reliable parachute deployment system. The main canopy is packed carefully in a custom “Dbag”, which is attached to a drogue chute to stabilize the system during free-fall and deploy the main canopy at a preset altitude. This is done with a servo operated release mechanism, while steering is handled by a pair of modified winch servos intended for RC sailboats.

All the electronics are mounted on a stack of circular 3D printed brackets which fit in a tubular housing, bolted together with threaded rods. With the help of a design student [Yohan] also upgraded the simple tube housing to a lockable, foam-insulated design to help it handle temperatures at high altitudes.

The flight main flight computer is a Teensy 4.1 plugged into a custom PCB to connect all the navigation, communication, and flight systems. The custom Arduino-based autopilot takes inputs from a GPS receiver, and pilots the system to the desired drop zone, which it circles until touchdown.

The entire project is extremely well documented, and all the design files and code are open source and available on Github. Continue reading “R2Home Is Ready To Bring Back Your High Altitude Payload” →

Turn Drone Into A Large Propeller To Increase Hover Efficiency

July 24, 2022 by Danie Conradie 42 Comments

Multirotor drones are significantly more popular than conventional helicopter designs for many reasons, which do not include efficiency. Making use of the aerodynamic effects behind this, [Nicholas Rehm] was able to significantly increase the efficiency of his experimental tricopter by turning it into one large spinning propeller.

Since aerodynamic drag is proportional to velocity, a small, high-RPM propeller will require more power to produce the same thrust as a large, low-RPM propeller. With this in mind, [Nicholas] built a tricopter that can rotate all three long arms together using a single servo, giving it very aggressive yaw control. By attaching a wing to each of the arms, it becomes a large variable pitch propeller powered by tip thrusters.

To measure the efficiency of the craft, a small lidar sensor was added to allow accurate PID altitude control. While keeping the drone at a constant altitude a few feet off the ground, [Nicholas] measured the power draw of the motors in a hover, and then let the drone spin around its yaw axis up to almost 5 rev/s.

At a spin rate of 4 rev/s, the power draw of the motors was reduced by more than 60%. Even compared to the drone without the added weight of the wings, it still used 50% less power to maintain altitude.

Since [Nicholas] hadn’t yet implemented horizontal position control while spinning, the length of each test run was limited by the wind drift. He plans to solve this, and also do some testing of the drone in horizontal flight, where the added airfoils will also increase efficiency.

We’ve featured a few of [Nicholas]’ flying machines here on Hackaday, including a foam F-35 VTOL and a cyclocopter. Most of his aircraft run his open source dRehmFlight flight stabilization, created specifically for hacking.

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It Turns Out You Can’t Just Fly A Drone Under Water

July 17, 2022 by Matthew Carlson 27 Comments

The differences between a drone and an underwater remote-operated vehicle (ROV) aren’t actually that large. Both have powerful motors that move large volumes of fluid (yes, air is a fluid), a camera, a remote, and an onboard battery. So when [RCLifeOn] got his hands on a cheap used drone, he reckoned that it could fly underwater just as well as it did in the air.

To his credit, the principle was sound, and the initial tests looked promising. However, we will spoil the ending and tell you it doesn’t work out as well as he hoped due to water leakage. He printed a case with a large panel for accessing electronics inside and an acrylic window for the camera. The panel pressed up against a gasket via the few dozen metric screws along the perimeter. Despite the design being quite whimsical, he quickly regrets the screws as getting inside is tiring on the wrists. He epoxies the hatch to the hull and drills holes to charge the battery to stop the seemingly never-ending water leaks. After its maiden journey, water got inside and fried some of the motor controllers. So for the second test run, he used what limited capabilities it had left.

Despite the project not working out how he expected, it’s a great example of how some reused parts and some 3d printing can make something entirely different. So perhaps next time, instead of throwing that broken drone away, see if it could be given just a bit of love. Possibly the propellers can be combined or make do with only three motors. Or just go the [RCLifeOn] route and make it into something new entirely.

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Up In The Sky… It’s A Bird… It’s A Drone… Oh Yeah, It’s A Drone

June 21, 2022 by Al Williams 15 Comments

One staple of science fiction is the ornithopter, which is a plane with moving wings. While these haven’t proved very practical in the general sense, a recent paper talks about mimicking natural wings changing shape to improve maneuverability in drones and other aircraft. In particular, the paper talks about how the flight performance of many birds and bats far exceeds that of conventional aircraft.

The technical term for being more maneuverable than a conventional aircraft is, unsurprisingly, called supermaneuverability. Aircraft performing things like the Pugachev Cobra maneuver (watch the video below, or the latest Top Gun movie) require this type of operation, and with modern aircraft, this means using thrust-vector technology along with unstable airframes and sophisticated computer control. That’s not how birds or bats operate, though, and the paper uses modern flight simulation techniques to show that biomimicry and thrust vector technology don’t have to be mutually exclusive.

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Can A Drone Push A Bike?

June 19, 2022 by Matthew Carlson 20 Comments

It sounds like a rhetorical question that a Midwestern engineer might ask, something on the order of ‘can you fix this bad PCB spin?’ [Tom Stanton] sets out to answer the title question and ends up building a working e-bike with a drone motor.

You might be thinking, a motor is a motor; what’s the big deal? But a drone motor and a regular e-bike motor are made for very different purposes. Drone motors spin at 30,000 RPM, and an e-bike hub motor typically does around 200-300 RPM while being much larger. Additionally, a drone motor goes in short spurts with a large fan blowing right on it, and an e-bike motor can run almost continuously.

The first step was to use gears and pulleys to reduce the RPM on the motor to provide more torque. A little bit of CAD and 3D printing later, [Tom] had a setup ready to try. However, the motor quickly burned out. With a slightly bigger motor and more gear reduction, version 2 performed remarkably well. After the race between a proper e-bike and the drone bike, the coils were almost melted.

If you’re thinking about making your bike electric, we have some advice. We’ll throw in a second piece of advice for free: use a larger motor than the drone motor, even though it technically works. Video after the break.

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