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.
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.
It should come as no surprise that the COVID-19 pandemic has sparked renewed interest in robotic deliveries. Amazon saying they would some day land Prime orders in your backyard with a drone sounded pretty fanciful a few years ago, but now that traditional delivery services are under enormous strain and people are looking to avoid as much human contact as possible, it’s starting to make a lot more sense.
Now to be clear, we don’t think you’ll be seeing this modified RC truck rolling up your driveway with a pizza in tow anytime soon. But the experiments that [Sean] has been doing with it are certainly interesting, and show just how far autonomous rover technology has progressed at the hobbyist level. Whether you need to move some sushi or a sensor package, his build is a great starting point for anyone interested in DIY robotic ground vehicles.
Especially if you want to take things off the beaten path once and awhile. By combining the Pixhawk autopilot system with an off-road RC truck by Traxxas, [Sean] has created a delivery bot that’s not afraid of a little mud. Or even the occasional jump, should the need arise. Just don’t expect your shrimp cocktail and champagne to arrive in one piece after they’ve been given the Dukes of Hazzard treatment.
In the video after the break [Sean] goes over some of the lessons learned on this build, including how he managed to keep the electronics from cooking themselves in the Texas heat. He also goes over the realities of building an autonomous driving system that doesn’t actually have a camera onboard; sure you can plan a route for it in advance, but all bets are off if an unexpected obstacle blocks the path. It’s a pretty serious shortcoming he’s looking to address in the future, as well as upgrading to a far more accurate RTK-GPS receiver.
Don’t let the friendly smile on this RC cart fool you, it will take your strawberries away — though that’s kinda the point. It’s an RC car that [transistor-man] and a few friends modified for carrying freshly picked strawberries at strawberry fields so that you don’t have to.
They started with an older Traxxas Emaxx, a 4-wheel drive RC monster truck. The team also bought a suitable sized water cooler at a local hardware store. A quick load test showed that 5lbs collapsed the springs and shock absorbers, causing the chassis to sink close to the ground. The team had two options: switching to stronger springs or locking out the springs altogether. They decided to replace one set of shocks with metal plates effectively locking them. After that it was time for some CAD work, followed by the use of a water jet to cut some aluminum plate. They soon had a mounting plate for the water cooler to sit in. This mounting plate was attached to 4 posts which originally held the vehicle’s Lexan body. A bungee cord wrapped around the cooler and posts on the mounting plate holds the cooler in place.
Some initial testing showed that the vehicle moved too fast even in low gear and tended to tip over, as you can see in the first video below. Some practice helped but a 3:1 reduction planetary gearbox brought the vehicle down to walking speed, making a big difference. A trip was arranged to go to local strawberry picking field at Red Fire Farms, but not without some excitement first. At 1AM the UNIK 320A High Voltage Speed controller emitted some magic smoke. A quick check with a thermal-camera found the culprit, one of the MOSFETs had failed, and after swapping it with one that was close enough they were back in business.
As you can see in the second video below, testing in the strawberry field went very well, though it wasn’t without some tipping. Kids also found it a fun diversion from picking strawberries, alternating between mock fright and delight.
R.I.P sand-colored radio-controlled truck. Your life ended with a bang and in doing so, saved some lives. This little work-horse is a hack that [Ernie Fessenden] put together and sent to his brother [Sergeant Chris Fessenden] who is on a tour of duty in Afghanistan.
[Chris’] team is trained to be on the lookout for roadside bombs, but [Ernie] wanted to sent him something cool that could also keep him safe. By adding a camera to the hood of the Traxxis Stampede and using a gun-mountable LCD screen, the soldiers now have a way to see what’s on the road ahead from their armored Humvee. Sounds like it would work just fine right? Well the hack just got a big endorsement when it tripped an IED made of around 500 pounds of explosives. [Chris] and five other soldiers on patrol were unharmed in the event, and [Ernie] already has a replacement model on the way.
[Thanks Rioexxo and Alex]
More proof that battlefield hacks deserve a place next to some of the high-ticket items you’d usually associate with weapons of war.
[ESylin] built an autonomous rover that roams the vacant halls of his school. On the hood of the vehicle he’s mounted two Maxbotix sonar sensors that do a great job of keeping the vehicle centered in the hallway. It will follow a wall around a corner (favoring its left side because of the left-facing sensor) and it will stop to correct itself if it gets off course. That’s because when you’re not driving a dsPIC33 is, with a Traxxas XL-5 speed controller and a hobby servo for steering. But this little guy hasn’t lost all his pep. Manual control and be switched on from from an R/C controller so you can burn up the floor tiles. Take a look at the demo after the break, with the manual control demo shown at about 4:10. Continue reading “Autonomous Rover Roams The Halls”→