For a long time radial aircraft engines, with their distinctive cylinder housings arranged in a circle, were a common sight on aircraft. As an experiment, [KendinYap], wanted to see if he could combine 3 small DC motors into a usable RC aircraft motor, effectively creating an electric radial engine.
The assembly consists of three “180” type brushed DC motors, mounted radially in a 3D printed casing. A 3D printed conical gear is attached to each motor shaft, which drives a single output gear and shaft mounted in the center with two bearings. The gear ratio is 3:1. A variety of propellers can be mounted using 3D printed adaptors. As a baseline, [KendinYap] tested a single motor on a scale with a 4.25-inch propeller on a scale, which produced 170 g of thrust at 21500 RPM. Once integrated into the engine housing, the three motors produced 490 g of thrust at 5700 RPM, with a larger propeller. Three independent motors and propellers should theoretically provide 510 g of thrust, so there are some mechanical losses when combining 3 of them in a single assembly. However, it should still be capable of powering a small RC plane. It’s also not impossible that a different propeller could yield better results.
While there is no doubt that it’s no match for a brushless RC motor, testing random ideas just to see if it’s possible is usually fun and an excellent learning experience. We’ve seen some crazy flyable RC power plants, including a cordless drill, a squirrel-cage blower, and a leaf blower.
[rctestflight] has built several autonomous boats, and with missions becoming longer and more challenging, he bought an inflatable kayak to serve as a dedicated rescue vessel. Instead of relying on outdated manual paddling, he built an autonomous solar-powered tugboat.
The tugboat uses a pair of molded fiberglass hulls in a catamaran configuration. The wide platform allows a pair of 100W solar panels to be mounted on top. It was [rctestflight]’s first time molding anything out of fiberglass, so there was quite a bit of trial and error going on. The mold was 3D printed in sections, aligned with dowel pins, and glued together. After the epoxy had cured, the mold halves could be split apart for easier removal of the hull.
As with most of [rctestflights] autonomous vehicles, control is handled by a Pixhawk 4 running ArduPilot/ArduRover. A pair of 76 mm brass propellers powered by brushless motors provide propulsion and differential steering. The motors get power from six LiFePO4 batteries, which charge from the solar panels via MPPT charge controllers. The hulls are covered with plywood decks with removable hatches and inspection windows. After a bit of tuning, he took the boat for a few test runs, the longest being 5.1 km with himself in tow in the kayak. At less than 5 km/h (3 mph) it’s no speedboat, but certainly looks like a relaxing ride. Many of [rctestflight]’s previous vessels were airboats to avoid getting underwater propellers tangled in weeds. It was less of an issue this time since he could just haul the tugboat close to the kayak and clear the propellers.
[rctestflights] are always entertaining and educational to watch, and this one certainly sets the standard for sea-shanty soundtracks at 13:32 in part two.
One of the major perks of all the affordable flight controllers and motors available from the hobby market is that you can really experiment with some crazy aircraft designs. [amazingdiyprojects] is experimenting with a coaxial helicopter design, with the goal off possibly using for a manned version in the future. (Video link, embedded below.)
The aircraft uses a pair of coaxial counter-rotating motors with large propellers, with several redundant control surfaces below the propellers. One of the theoretical advantages of this arrangement, compared to the more conventional quadcopter type designs, is redundancy. While a quadcopter will start tumbling when a single motor fails, this design will still be able to descend safely with just one motor.
It is also not dependent on the main motors for yaw, pitch and roll control. In multirotors, the motors need to keep a significant amount of the motor’s available power in reserve to increase torque at a moment’s notice for attitude control. This craft can use all the available thrust from the motors for lift, since control is provided by the control surfaces. There are five sets of redundant control surfaces below the propellers, each set connected to a separate flight controller.
Another advantage of this design is efficient for a given footprint, since one large propeller will always be more efficient than multiple smaller propellers. One of the goals for [amazingdiyprojects] is to fit the full size craft in a shipping container or on a trailer for transport without dissasembly.
This is newsworthy in itself because despite several years and significant resources being devoted to the problem of drones hitting planes, demonstrable cases remain vanishingly rare. The machine in this case being a police one will we expect result in many fewer column inches for the event than had it been flown at the hands of a private multirotor pilot, serving only to heighten the contrast with coverage of previous events such as the Gatwick closure lacking any drone evidence.
It’s picking an easy target to lay into the Your Regional Police over this incident, but it is worth making the point that their reaction would have been disproportionately larger had the drone not been theirs. The CTV news report mentions that air traffic regulators were unaware of the drone’s presence:
NAV Canada, the country’s air navigation service provider, had not been notified about the YRP drone, Transport Canada said.
Given the evident danger to aviation caused by their actions it’s not unreasonable to demand that the officers concerned face the same penalties as would any other multirotor pilot who caused such an incident. We aren’t holding our breath though.
While it’s great to be experienced and have a ton of specialist knowledge needed to solve a problem, there’s something liberating about coming at things from a position of ignorance. Starting at ground zero can lead you down the path less traveled, and reveal solutions that might otherwise not have presented themselves. And, if [Robin Debreuil]’s exploration of the “minimum viable quadcopter” is any example, some pretty fun failure modes too.
The minimum viable product concept is nothing new of course, being a core concept in Lean methodologies and a common practice in many different industries. The idea of building an MVP is to get something working and in the hands of users, who will then give you feedback on everything wrong with it, plus, if you’re lucky, what you got right. That feedback informs the next design, which leads to more feedback and a whole iterative process that should design the perfect widget.
In [Robin]’s case, he wanted to build a quadcopter, but didn’t know where to start. So his first version was as simple as possible: a motor with a propellor and a small LiPo battery. No chassis, no control electronics — nothing. And it worked just about as well as expected. But fixing that problem led to different designs, the process of which was fascinating — we especially liked the quad with opposing motors controlled by mercury tilt switches to sense attitude changes.
In the end, [Robin] took a more conventional tack and used a microcontroller and BetaFlight to get his popsicle stick and hot glue UAV airborne. But the decision to start with a minimum viable design and iterate from there was a powerful learning experience in tune with [Robin]’s off-beat and low-key outlook, which we’ve seen before with his use of bismuth for desoldering and his scratch-off PCBs.
In the previous versions, researchers showed that they were able to steer the SAW (Samara Autorotating Wing) by actuating the trailing edge of the blade with a servo. It takes input from an onboard 3-axis magnetometer and GPS, and adjusts the control surface continuously depending on its orientation to make it fly in the chosen direction. The latest paper (PDF) focuses on the craft’s new ability to switch from autorotation to a rapid dive and back to autorotation. Named the dSAW (diving SAW), it can drop like a rock by changing the control surface angle to almost 90° the wing to stall it. It exits the dive by simply moving the control surface back to the normal autorotation position. The kinetic energy built up during the dive is converted to rotational energy very quickly, which slows its vertical velocity to almost zero for an instant before settling back into its normal glide.
We can certainly see this being useful where the dSAW needs to quickly lose altitude to avoid being pushed off-course by the wind. The video below demonstrates this by dropping three dSAWs from an RC airplane. On command, they spread out, each in its designated direction, and then repeatedly switch between dive and autorotation mode as they descend to the ground. The researchers envision this being used to scatter sensor units over a large area in a controlled fashion from a single aircraft. What would you do with this technology? Let us know below.Continue reading “Helicopter Seed Robot Can Also Drop Like A Rock”→
For conventional vertical takeoff and landing rotors on vertical shafts are the most common solution, as seen in helicopters and multirotors. A much less popular solution is the cyclocopter, which consists of a pair of rotors spinning around a horizontal shaft with horizontal blades. [Nicholas Rehm] built a remote-controlled cyclocopter as part of a research project and gave us an excellent overview of this unique craft in the video after the break.
Also known as the cyclogyro, the idea is not new, with the first one constructed in 1909. The first flight was a long time later in the 1930s, but it was quickly discovered that they were too unstable to be flown manually by a human, so the idea was shelved. Thanks to modern microcontrollers, researchers have recently been able to build small-scale versions, like the tiny example from the University of Texas.
Lift is produced using four or more airfoils on each of the two cycloidal rotors. At the top and bottom of rotation they have a positive angle of attack, with a neutral angle on the sides. The blades’ angle of attack can be adjusted to produce forward or reverse thrust. An additional motor with a conventional propeller is mounted on the nose to counteract the torque created by the main rotors, similar to a helicopter’s tail rotor.
Unlike multirotors, cyclocopters don’t need to pitch forward to move horizontally. The blades also don’t need to be tapered and twisted like a conventional rotorcraft, since the relative airflow velocity remains constant along the length of the blade. However, they have some significant downsides that will likely prevent them from moving beyond the experimental stage for the foreseeable future. The rotors are quite complex mechanically and need to be very lightweight since the design doesn’t lend itself to great structural strength. This was demonstrated by [Nicholas] when a minor crash snapped one of the rotor arms. However, it is an excellent demonstration of the adaptability of [Nicholas]’ open-source dRehmFlight flight controller, which he has also used to fly a VTOL F-35 and belly-flopping starship.