Tiny RC Truck And Trailer Motors Around Tabletop

Most RC cars replicate real-world race cars or fantastical off-road buggies for outdoor escapades. [diorama111] is an expert at building tiny desk-roaming models, though, and built this exquisite micro semi-truck and trailer.

Based on a 1/150 scale truck and trailer model, the build starts with the tractor unit. It’s disassembled, and its plastic wheels are machined on a tiny lathe so they can be fitted with grippy rubber tires carved out of O-ring material. The front wheels are given hubs and mounted to a motor-driven screw-type steering assembly. A photodetector is used to aid in self-centering. The rear axle is fitted with a geared drivetrain, running off a small DC motor. Multiple gear stages are used to give the build plenty of torque for pulling the trailer. Remote control of the model is achieved over Bluetooth, with an ATtiny3217 tucked inside with motor drivers to run the show.

The microcontroller also runs a full set of driving, tail, and indicator lights. The trailer is fitted with an infrared receiver and a battery of its own. It receives signals from an infrared LED on the tractor unit, which tell the trailer when to turn on the taillights and indicators.

There aren’t too many modelers working in the RC space at the 1:150 scale. [diorama111] has form here, though, and we’ve featured a previous Toyota Crown build before.

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A circular wheeled robot sits on a white background. There is a green tank of butane/propane in the center surrounded by wires and electronics.

Doomba: Purifying Your Floors With Fire

If you’ve ever thought that your floor cleaning robot eating the fringe on your rug wasn’t destructive enough, [Kyle Brinkerhoff] is working on a solution — Doomba.

This blazingly fast RC vehicle has a tank of butane/propane gas nestled snugly amid its electronics and drive system to fuel a (not yet implemented) flamethrower. Watching how quickly this little bot can move in the video below certainly made our hearts race with anticipation for the inevitable fireworks glory of completed build. Dual motors and a tank-style drive ensure that this firebug will be able to maneuver around any obstacle.

As of writing, the flamethrower and an updated carriage for the drivetrain are underway. Apparently, spinning very quickly in circles can be just as disorienting for robots as it is for us biological beings. During the test shown below, the robot kicked out one of its drive motors. [Kyle] says the final touch will be putting the whole assembly inside an actual Roomba shell for that authentic look.

With spooky season upon us, it’s always good to have the cleansing power of fire at hand in case you find more than you bargained for with your Ghost-Hunting PKE Meter. While there’s no indication whether Doomba can actually run DOOM, you might be interested in this other Doomba Project that uses Roomba’s maps of your house to generate levels for the iconic shooter.

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RC Lawnmower Is Built To Last

Mowing the lawn is one of those tasks that someone will always be optimizing or automating. To allow him to mow the lawn while seated comfortably in the shade, [Workshop from Scratch] built an RC Lawnmower in his signature solid steel frame style.

The chassis consists of a heavy welded steel frame from square tubing, with a pair of knobbly go-kart wheels on the back and large caster wheels on the front. The actual grass-cutting part is a 173cc petrol lawnmower engine with a steel hull, mounted on an articulating subframe which can be remotely raised and lowered using a linear actuator. The rear wheels are attached to a pair of custom sprocket hubs, driven via chain by two 200 W geared DC motors to allow skid steering.

The motors and electronics are powered by a set of 18 Ah lead-acid batteries wired in parallel. The petrol engine can also charge the batteries, but its current isn’t enough to keep up while mowing. However, it does help to extend the range. All the electronics are housed in a plastic enclosure with a power switch, key start for the engine, and battery charge indicator on the lid. The power from the batteries runs through a pair of automotive relays connected to the power switch and a set of fuses for protection. For safety [Workshop from Scratch] wired a relay to the engines’ coil to shut it off remotely, or when the radio link to the controller is lost. An action cam was also mounted on the electronics box to stream a first-person view to a smartphone over WiFi.

Overall this is a very well built project, especially mechanically, and looks like the perfect platform for further self-driving using Ardurover. [rctestflight] has demonstrated the capabilities of the open source autopilot with several rovers, including a tiny lawnmower that cuts grass with Exacto blades.

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Autogyro Models Are Hard — Even For [Peter Sripol]

Aviation consists of two major groups. Airplane enthusiasts, and helicopter enthusiasts. The two groups rarely get along, each extolling the virtues of their chosen craft. Somewhere in between are autogyro folks. People who like vehicles that blend the best (or worst) of both airplanes and helicopters. Aviation master [Peter Sripol] has dipped his toes into the autogyro world, but not without some trouble.

Autogyros are propelled by a propeller, like a plane. They also have a tail section that works similar to a fixed-wing aircraft. That’s where the similarities end though. Lift for autogyros comes in the form of a rotating set of blades, much like a helicopter. Autogyro rotors aren’t powered during flight. They utilize autorotation. The blades freewheel, spun by the air as the craft moves forward.

[Peter] recently got his hands on a full-scale autogyro. So it made sense to build a model to help learn to fly. This isn’t [Peter’s] first attempt with autogyro models. He’s built a few in the past, with limited success. This time he started from scratch and ran into even more problems!

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Radio Control Joby Aircraft Uses Six Tiltrotors To Fly

eVTOL (Electric Vertical Take-off and Landing) craft are some of the more exciting air vehicles being developed lately. They aim to combine the maneuverability and landing benefits of helicopters with the environmental benefits of electric drive, and are often touted as the only way air taxis could ever be practical. The aircraft from Joby Aviation are some of the most advanced in this space, and [Peter Ryseck] set about building a radio-controlled model that flies in the same way.

The design is inspired by the Joby eVTOL test vehicle.

The result is mighty complex, with six tilt rotors controlled via servos for the utmost in maneuverability. These allow the vehicle to take off vertically, while allowing the rotors to tilt horizontally for better efficiency in forward flight, as seen on the Bell-Boeing V-22 Osprey.

The build uses a 3D-printed chassis which made implementing all the tilt rotor mounts and mechanisms as straightforward as possible. A Teensy flight controller is responsible for controlling the craft, running the dRehmFlight VTOL firmware. The assembled craft only weighs 320 grams including battery; an impressive achievement given the extra motors and servos used relative to a regular quadcopter build.

With some tuning, hovering flight proved relatively easy to achieve. The inner four motors are used like a traditional quadcopter in this mode, constantly varying RPM to keep the craft stable. The outer two motors are then pivoted as needed for additional control authority.

In forward flight, pitch is controlled by adjusting the angle of the central four motors. Roll is achieved by tilting the rotors on either side of the plane’s central axis, and yaw control is provided by differential thrust. In the transitional period between modes, simple interpolation is used between both modes until transition is complete.

Outdoor flight testing showed the vehicle is readily capable of graceful forward flight much like a conventional fixed wing plane. In the hover mode, it just looks like any other multirotor. Overall, it’s a great demonstration of what it takes to build a successful tilt rotor craft.

We’ve seen tilt rotor UAVs before, and they’re as cool as they are complicated to build. Video after the break.

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Running Methanol RC Engines On Gasoline

Methanol is a popular fuel for small engines used in radio-controlled models, but comes at a higher price than gasoline. It’s also harder to source and can be a mite corrosive, too. Gasoline comes with some benefits, but running it in a methanol engine usually requires some mods. [David] and [Bert] worked together to build a mixture controller for just this purpose.

The controller uses a solenoid to control the flow of gasoline to a conventional methanol-tuned carburetor for a small RC engine, allowing it to be accurately tuned to run gasoline well across the whole RPM range. Having gone through many revisions, all documented in a big forum thread, the latest version uses a Seeduino Xiao controller and a BMP280 pressure and temperature sensor for determining the right fuel/air mixture for the conditions. A small OLED screen can optionally be fitted to help with configuration of the mixture controller.

The system has worked well in testing, with [David] and [Bert] reporting that they have “converted engines as small as 0.3 CID up to large radials with this system.” It’s a promising tool that could be handy to have in the RC modeller’s arsenal.

These tiny engines have other applications too; they can make for one crazy power drill, that’s for sure!

Ground Effect Aerodynamics On An RC Car

Ground effect aerodynamics will return to Formula 1 in a big way in the 2022 season, hopefully washing away the bad taste left in fan’s mouths after the recent controversial season decider. [Engineering After Hours] has experimented with F1 aerodynamics on RC cars before, and decided that it was time to try and implement a proper ground-effect design himself.

The aim of ground effect aerodynamics is to create a constriction for airflow between the bottom of the car and the ground underneath. This constriction accelerates the flow beneath the car, and as per Bernoulli’s principle, causes a corresponding pressure drop, sucking the car down onto the track. Viscosity also plays a role; from the car’s perspective, the road beneath the vehicle is moving backwards at some speed, pulling on the fluid thanks to the boundary layer on the ground itself. This further helps increase the strength of the effect.

A vacuum-formed undertray complete with side skirts was installed on the RC car in order to generate ground effect downforce. A quick test with a leaf blower indicates the system works, and that the side skirts are a key component.

Lateral acceleration was significantly improved by around 20% in testing with the ground effects installed, though [Engineering After Hours] admits that without a wind tunnel, the results aren’t the most scientific. However, with the undertray being relatively lightweight, we suspect the aero elements are likely providing plenty of benefit without too much of a negative effect on acceleration or handling.

Check out some of the other aero experiments [Engineering After Hours] has undertaken, too. Video after the break. Continue reading “Ground Effect Aerodynamics On An RC Car”