High Speed RC Jet Car Is A Harsh Teacher

August 28, 2022 by Danie Conradie 8 Comments

Making machines go fast has always been a seemingly unavoidable impulse for humans. With the advent of radio control, it’s possible to get a taste of the rush without putting your life and too much money on the line. In the spirit of speed, [James Whomsley] strapped a jet turbine engine to an RC car, and learned some hard lessons along the way.

The car started as a four-wheel drive electric race car, but [James] removed most of the drive train components and mounted the jet turbine engine on a pair of 3D printed struts. Originally intended for large-scale RC planes, the little jet engine produces about 120 N of thrust. To allow the car to stop, [James] kept the drive shafts and connected them to a centrally mounted disk brake unit.

For the first high-speed test runs, James added a vacuum-formed shell and a pair of large vertical stabilizers for high-speed stability. On the 3rd test run at a local racetrack, the car got up to 190 km/h (118 MPH) before it veered off the track and crashed. Fortunately, the chassis and engine only sustained minor damage and were easy to repair.

James rebuilt the car with a lower engine to reduce the center of gravity and added an electronic gyro in an attempt to stabilize the car at high speed. Time ran out, and he wasn’t able to test the car before taking it to a high-speed RC event held on a runway. This led to another crash when the car again veered off the track after badly oscillating. After checking the onboard footage, [James] discovered the receiver had experienced a loss of signal, and an incorrect fail-safe setting made the engine go full throttle. After more tests, James also found that excessive play in the steering mechanism had caused the gyro to induce oscillations.

Although this car failed in the end, [James] intends to take the lessons learned into a new high-speed car build. [rctestflight] also did some testing with an EDF-powered RC car recently, and used a drone flight controller for high speed stability. This is not [James]’ first foray into speed machines, having previously experimented with a rocket plane.

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High-Speed RC Car Needs A Flight Controller

August 23, 2022 by Danie Conradie 2 Comments

The fastest ground vehicles on earth are not driven by their wheels but by an aircraft jet engine. At world record speeds, they run on an aerodynamic razor’s edge between downforce, which limits speed, and liftoff, which can result in death and destruction. [rctestflight] wanted to see what it takes to run an RC car at very high speeds, so he built a ducted-fan powered car with aerodynamic control surfaces and an aircraft flight controller.

This high-speed car is built on the chassis of a 1/14th scale RC buggy, powered by 4 EDF (electric ducted fans) mounted on a very long aerodynamic foam board shell. It also has an aircraft-style tail with elevons and rudders for stabilization and control at high speed using an ArduPilot flight controller. The flight controller is set up to stabilize in the roll and yaw axis, with only fixed trim in the pitch axis.

[rctestflight] got the car up to 71 MPH (114 km/h), which is fast for most RC cars but well short of the 202 MPH RC car speed record. It was still quite hard to keep in a straight line, and the bumpy roads certainly didn’t help. He hopes to revisit the challenge in the future with larger motors and high voltage batteries.

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Hacking Toy RC Cars With The HackRF One

April 30, 2022 by Ryan Flowers 3 Comments

The origin story for many who’d call themselves a member of the hacker community usually starts with taking things apart as a child just to see how they worked. For [Radoslav], that trend doesn’t seem to have slowed down, and he’s continued taking toys apart. Although since it’s his daughters little radio controlled car, he stuck to a non-destructive teardown. The result? He’s able to control the car with his laptop through a HackRF One SDR transceiver as shown in the video below the break.

[Radoslav] is no stranger to reverse engineering embedded devices, IoT gadgets, and probably more. So he started with what information was publicly available about the radio control interface in use. Many electronic devices sold in the US must be certified by the FCC (Federal Communications Commission) and prominently display their ID number, and this toy was no exception. The FCC database gave [Radoslav] enough information to know that the communication protocol is modulated with GFSK, a type of Frequency Shift Keying.

He fired up his favorite radio signal analysis tool and and got to work on the protocol itself. Along the way he found that communication between the car and controller is bidirectional but also very easy to get around. The result is that he can drive the car around with his laptop- definitely a cool hack, but for this one, the journey was surely the goal, not the destination.

If hacking on RC cars really gets your wheels turning, you might like this little RC car that can drive on the ceiling. Or if you’re feeling a bit hungry, check out how you can use the HackRF to nab a table at your local restaurant.

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RC Car Test Tether Takes Car Testing To New Lengths

April 5, 2022 by Ryan Flowers 8 Comments

It’s fascinating to see what happens when a creative hacker is given a set of constraints to work within. [rctestflight] found themselves in a very specific set of circumstances: Free RC cars from sponsors, and no real purpose for them. Instead of just taking them apart to see what made them tick (itself the past time of many a beginning hacker), [rctestflight] decided to let the RC cars disassemble themselves, destructively, on their way to 100,000 (scale) RC Car Miles, tallying up the distance (and the carnage) in the end as you see in the video below the break.

Re-using a jig and test track (his backyard) from another test, [rctestflight] set up solar powered tether that could power any of the vehicles under test. The vehicles were modified as needed to drive along the circular track on a tether, and once stability was achieved, the cars were set on their own to either drive 100,000 scale miles or die trying.

Seeing as how [rctestflight] hales from the Pacific NorthWet of the United States near Seattle, the endurance test turned out to be not just a test of distance. Among the factors evaluated were how well each vehicle could withstand the mud, grime, and yes, even earthworms, that awaited them.

After each vehicle failed beyond the point of a quick fix, they were all torn down. Where each manufacturer cut corners could clearly be seen, and the weaknesses and strengths of each vehicle were pretty interesting. Plus, there’s a pretty great (awful) uh… rendition… of an iconic 80’s song. Twice. And of course the final conclusion: Exactly how many miles did each vehicle go before catastrophic failure? Check the video for results.

Regular readers will know that [rctestflight] is somewhat of a Hackaday regular, with plentiful great hacks such as this drone boat that sails the high seas of Lake Washington.

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Ground Effect Aerodynamics On An RC Car

December 21, 2021 by Lewin Day 3 Comments

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” →

Building An Aluminum RC Truck From Scratch

September 5, 2021 by Adam Fabio 14 Comments

These days you can get just about any kind of radio controlled vehicle as a ready-to-run model. Cars, trucks, excavators, you name it. Open the box, charge the batteries, and you’re ready to roll. Even with all these modern conveniences, there is still a special breed of modelers who create their own models using only a few off-the-shelf parts.

[Rini Anita] is exactly that rare breed, creating this aluminum RC truck from scratch. The truck itself is a cab-over — short for Cab Over Engine (COE), a style seen making local deliveries worldwide. He starts with the ladder frame chassis, which is constructed using an extruded aluminum channel. This is the same material you’d normally use for the door tracks in retail store display cases. The electronics and standard RC fare: a receiver, electronic speed control, and a servo for steering. Batteries are recycled lithium cells. The main gearbox and drive axle look to be sourced from another RC vehicle, while leaf springs and suspension components are all custom built.

The truck’s body is a great example hand forming metal. First, a wooden form was created. Sections for the windows and door panels were carved out. Sheet aluminum was then bent over the wood form. Carefully placed hammer blows bend the metal into the carved sections – leaving the imprints of doors, windows, and other panel lines.

Throughout this build, we’re amazed by [Rini]’s skills, and the fact that the entire job was done with basic tools. A grinder, an old drill press, and a rivet gun are the go-to tools; no welder or 3D printer to be found. This puts a project like this well within the means of just about any hacker — though it may take some time to hone your skills! For his next truck, maybe [Rini] can add a self driving option!

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Fan Lets RC Car Drive On The Ceiling

September 4, 2021 by Lewin Day 7 Comments

Downforce is a major part of modern motorsport, keeping cars glued to the track at high speeds. However, for small radio control cars, adding a fan for a little suction can achieve even greater feats, as demonstrated by this build by [DD ElectroTech].

The build began as a simple two-motor, skid-steer RC car build with a fan for suction. Controlled by a smartphone app, a cheap Arduino board with an HC-05 Bluetooth module ran the show. However, when this was all assembled, the car was too heavy to climb walls or stick to the ceiling.

Thus, a weight-saving plan was in order. Wheels were swapped out for lighter 3D printed parts. The electronics saw significant re-engineering, too, with the multiple separate modules all condensed down into one single custom PCB. After a few other tweaks, the new lighter car was able to easily drive on the ceiling and even climb walls, albeit with some difficulty.

It’s a fun little build and a good demonstration of how easy it is to whip up cool projects with modern electronics and 3D printed parts. We’ve seen other printed fan car builds before, too, but did you know the concept was first trialed in real-world motorsport competition? Video after the break.

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