A Cold Gas Thruster On An RC Car

August 15, 2021 by Lewin Day 12 Comments

Tesla have boldly claimed that one day they’ll ship a Roadster complete with a cold-gas thruster for truly ridiculous acceleration. Whether or not that ever comes to pass remains to be seen, but [Engineering After Hours] decided to try out the technology on an RC car instead.

The thruster uses a pair of disposable CO2 canisters to deliver 1770 g of thrust via a converging-diverging nozzle. Actuated by servos and a simple valve, the system dumps the high-pressure CO2 to help accelerate the car up to speed. Paired with sticky tires and a powerful brushless motor, the plan was to try and beat Tesla’s claimed 1.1 second 0-60mph acceleration figure for the thruster-boosted roadster.

Unfortunately, the high center of gravity of the RC car led to stability issues, largely due to the mounting of the thruster itself. Additionally, the high weight of the car – around 4.3kg – meant that at best, the thruster would only add 0.5g to the vehicle’s acceleration.

While the car didn’t net a quick 0-60 time, it’s still neat to see a cold gas thruster on an RC car. It may not have been a Tesla-beater like some earlier projects, but it was cool all the same. Video after the break.

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Solar Plane Is Like One Big Flying Solar Panel

May 29, 2021 by Lewin Day 15 Comments

Solar-powered plane concepts typically focus on high-efficiency glider-type designs, so as to make the best possible use of the limited power available from the sun. [rctestflight] wanted to try a different school of thought, instead building a relatively inefficient plane that nonetheless packed a huge amount of solar panels on board.

The plane consisted of a pizza-box style design, with a simple foam rectangular wing that was absolutely covered in solar panels. The plane was controlled with an off-the-shelf autopilot, and fitted with cheap, no-brand MPPT modules to handle charging the batteries. The plane faced difficulties in flight, most often with stability, which led to the autopilot getting the plane lost on one occasion. However, one flight was achieved with a full one hour and thirty minute duration, indicating the solar panels were helping to extend flight times beyond what was capable with batteries alone.

Further research on the ground showed that the cheap MPPT modules were wasting power, and there was more to be had. A better MPPT module was subbed in and showed that the panels could generate up to 5 amps under good conditions, while the plane only needed roughly 4.2 amps to fly. This would allow for indefinite flight in sunny conditions, though probably would not allow enough energy to be banked to fly 24 hours round the clock due to the lack of power at night.

We’ve followed [rctestflight]’s solar plane experiments for a while now, and can’t wait to see the next iteration. Video after the break.

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Modding A Hot Wheels Car Into A Radio Controlled Drift Weapon

April 23, 2021 by Lewin Day 14 Comments

Hot Wheels are some of the most popular diecast toy cars worldwide. The car bodies are faithful recreations of the real thing, though the models are mere stationary playthings. That wasn’t good enough for [Jakarta Diecast Project], who set about modifying a little BMW E30 M3 into an awesome radio-controlled drift car.

The build starts by disassembling the original car, and pulling out the original wheels. The baseplate is then modified to accept a new rear suspension and axle assembly. A small DC motor is mounted to the assembly to drive the rear wheels. A set of front steering knuckles are then installed up front, with their own suspension and hooked up to a tiny servo for steering. Everything’s controlled by a compact off-the-shelf RC receiver, which even features a gyro to help keep the tiny car straight under acceleration. The bodyshell is then stripped of paint, and given a sweet bodykit, before receiving a lurid orange paint job and decals. It’s reattached to the car’s baseplate via magnets, which make taking the car apart easy when service or modifications are required.

While the build doesn’t go into the nitty gritty on some of the harder parts, like the construction of the incredibly complex front knuckles, it’s nonetheless a great guide to building such a tiny and well-presented RC car. In looks and performance, the result trounces typical commercial offerings in the same scale, as you’d expect from such a hand-crafted masterpiece. It may not be the smallest RC car we’ve featured, but it is one of the coolest. Video after the break.

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Teardown: Linkimals Musical Moose

April 13, 2021 by Tom Nardi 23 Comments

Like so many consumer products these days, baby toys seem to get progressively more complex with each passing year. Despite the fact that the average toddler will more often than not be completely engrossed by a simple cardboard box, toy companies are apparently hell-bent on producing battery powered contraptions that need to be licensed with the FCC.

As a perfect example, we have Fisher-Price’s Linkimals. These friendly creatures can operate independently by singing songs and flashing their integrated RGB LEDs in response to button presses, but get a few of them in the room together, and their 2.4 GHz radios kick in to create an impromptu mesh network of fun.

They’ll soon be back, and in greater numbers.

Once connected to each other, the digital critters synchronize their LEDs and sing in unison. Will your two year old pay attention long enough to notice? I know mine certainly wouldn’t. But it does make for a compelling commercial, and when you’re selling kid’s toys, that’s really the most important thing.

On the suggestion of one of our beloved readers, I picked up a second-hand Linkimals Musical Moose to take a closer look at how this cuddly pal operates. Though in hindsight, I didn’t really need to; a quick browse on Amazon shows that despite their high-tech internals, these little fellows are surprisingly cheap. In fact, I’m somewhat embarrassed to admit that given its current retail price of just under $10 USD, I actually paid more for my used moose.

But you didn’t come here to read about my fiscal irresponsibility, you want to see an anthropomorphic woodland creature get dissected. So let’s pull this smug Moose apart and see what’s inside.

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Driving Upside Down With An RC Fan Car

February 3, 2021 by Lewin Day 8 Comments

We’ve all seen those tiny little RC cars that can climb walls thanks to the suction generated with fans. Their principle is essentially the opposite to that of a hovercraft. [Engineering After Hours] wanted to build his own RC car that could do the same, driving upside down and generating huge amounts of grip.

The build is based on a Traxxas RC car, but heavily modified for the task. An undertray is crafted, with ducts feeding a pair of twin 50mm electric fans. A skirt is fitted around the edge of the undertray, helping create a seal to maximise the downforce generated. This skirt is the area of much engineering effort, as it must form a good seal with the ground, particularly over minor pertubations, without creating undue levels of friction. Suspension components correspondingly need to be beefed up to stop the car bottoming out with the huge downforce generated by the fan system.

After much experimentation, the kinks are worked out, and the car is able to drive upside down successfully. It generates far more downforce than earlier wing experiments from [Engineering After Hours], as expected – with a tradeoff of higher weight and complexity. With the plan to create an RC car capable of huge lateral acceleration, we can’t wait to see what comes next. Video after the break.

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Active Aero For A Radio Control Car

January 3, 2021 by Lewin Day 12 Comments

Motorsport became obsessed with aerodynamics in the middle of the 20th century. Moving on from simple streamlined shapes, designers aimed to generate downforce with wing elements in order to get more grip between the tyres and the track. This culminated in the development of active aero, where wing elements are controlled by actuators to adjust the downforce as needed for maximum grip and minimum drag. Recently, [Engineering After Hours] decided to implement the technology on his Traxxas RC car.

The system consists of a simple multi-element front wing, chosen for its good trade-off between downforce and drag. The wing is mounted to a servo, which varies the angle of attack as the car’s pitch changes, as detected by a gyroscope. As the car pitches up during acceleration, the angle of the wing is increased to generate more downforce, keeping the nose planted.

The basic concept is sound, though as always, significant issues present themselves in the implementation. Small bumps cause the system to over-react, folding the wing under the front wheels. Additionally, the greater front downforce caused over-steer, leading to the install of a rear wing as well for better aero balance.

Regardless of some hurdles along the way, it’s clear the system has potential. We look forward to the next build from [Engineering After Hours], which promises to mimic the fan cars of the 70s and 80s. If you’re looking to improve aero on your full-size car, we’ve got a guide to that too. Video after the break.

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Radio Controlled Hovercraft Apes The SR.N1

December 15, 2020 by Lewin Day 7 Comments

Hovercraft never really caught on as regular transportation, but they are very cool. The Saunders-Roe SR.N1 was the very first practical example of the type, and served as a research vehicle to explore the dynamics of such vehicles. [mr_fid] was looking for a lockdown project, and set about crafting a radio controlled replica of his own.

The build is crafted out of a canny combination of plywood and balsa, the latter substituted in sections within the plywood hull to save weight. A pair of brushless outrunner motors are mounted in the central duct to provide lift, fitted with counter-rotating propellers in order to avoid torque effects on handling. Steering is via puff ports a la the original design, which allows the craft to spin very quickly in place to much amusement and no practical effect. The skirt is of a colorful design, carefully assembled out of polyurethane-coated nylon.

While it’s not the quickest way to build a hovercraft, it’s all the more beautiful for its attention to the details and function of the original prototype craft. We particularly like the sharp handling thanks to the puff port design. If you’re looking for a weirder design however, consider this Coanda Effect build. Video after the break.

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