What do you do when you come across a cheap electric bicycle on Facebook Marketplace from a seller who has a few hundred of the same ones available? If you’re someone like [Max Helmetag], you figure that it’s probably legit since nobody would be reselling hundreds of Lime ridesharing e-bikes. Thus, it makes for an excellent project to see how usable an old ridesharing bicycle is. According to the information on the e-bike’s frame, it was manufactured in 2017, and based on the plastic still covering parts of the bike, it had barely been used, if at all.
The ground-effect (GE) refers to the almost mystical property where the interaction of the airflow around an aircraft’s wing and the ground massively increases efficiency due to the reduction of lift-dependent drag, perhaps best demonstrated by the Soviet Lun-class “ekranoplans” of the 1980s and 90s. Interestingly, this principle also applies to rotary aircraft, which led the [rctestflight] YouTube channel to wonder what would happen if a quadcopter were to be adapted for GE.
As noted on the Wikipedia entry for Ground-effect vehicle (GEV), it’s essential to have some kind of forward motion. With a rotorcraft like a helicopter or quadcopter this motion is already provided by the spinning propeller, which makes it noticeably easier to get the aircraft into the ground-effect. operating mode. Following the notion that the GE becomes noticeable at an altitude that’s dependent on the length of the aircraft’s wings, this got translated into putting the largest propellers available on the custom inverted-prop (to put them lower to the ground) quadcopter, to see what effect this would have on the quadcopter’s performance. As demonstrated by the recorded current drawn (each time with a fully charged battery), bigger is indeed better, and the GE effect is indeed very noticeable for a quadcopter.
Getting a usable GEV out of the basic inverted-prop quadcopter required some more lateral thinking, however, as it was not very easy to control this low to the ground. Here following design cues from skirtless hovercraft designs helped a lot, essentially drawing on the Coandă effect. Although this improved performance, at this point the quadcopter had been fitted with a fifth propeller for propulsion and was skidding about more like a skirtless hovercraft and less of a quadcopter.
Although great for scaring the living daylights out of unsuspecting water-based wildlife, what this unfortunately demonstrates is that GEVs are still hard, no matter which form they take. At the very least it does make for an excellent introduction into various aspects of aerodynamics.
Fast charging is all the rage with new electric cars touting faster and faster times to full, but other EVs like ebikes and scooters are often left out of the fun with exceedingly slow charging times. [eprotiva] wanted to change this, so he rigged up a fast charging solution for his cargo bike.
Level 2 electric vehicle chargers typically output power at 7 kW with the idea you will fill up your electric car overnight, but when converted down to 60 V DC for a DJI Agras T10 battery, [eprotiva] is able to charge from 20% to 100% capacity in as little as 7 minutes. He originally picked this setup for maxing the regen capability of the bike, but with the high current capability, he found it had the added bonus of fast charging.
The setup uses a Tesla (NACS) plug since they are the most plentiful destination charger, but an adapter allows him to also connect to a J1772 Type 1 connector. The EV charging cable is converted to a standard 240 V computer cable which feeds power to a drone charger. This charger can be set to “fast charge” and then feeds into the battery unit. As an added bonus, many chargers that do cost money don’t start charging until after the first five minutes, so the bike is even cheaper to power than you’d expect.
For some reason, you can watch him do this on TikTok too.
A piece of manufacturing news from Tesla Motors caught our eye, that Elon Musk’s car company plans to die-cast major underbody structures — in effect the chassis — for its cars. All the ingredients beloved of the popular tech press are there, a crazy new manufacturing technology coupled with the Musk pixie dust. It’s undeniably a very cool process involving a set of huge presses and advanced 3D-printing for the sand components of the mould, but is it really the breakthrough it’s depicted as? Or has the California company simply scored another PR hit?
We produced an overview of die casting earlier in the year, and the custom sand moulding in the Tesla process sounds to us a sort of half-way house between traditional die casting and more conventional foundry moulding. I don’t doubt that the resulting large parts will be strong enough for the job as the Tesla engineers and metallurgists will have done their work to a high standard, but I’m curious as to how this process will give them the edge over a more traditional car manufacturer building a monocoque from pressed steel. The Reuters article gushes about a faster development time which is no doubt true, but since the days of Henry Ford the automakers have continuously perfected the process of making mass-market cars as cheaply as possible. Will these cast assemblies be able to compete with pressed steel when applied to much lower-margin small cars? I have my doubts.
Aside from the excessive road noise of the Tesla we had a ride in over the summer, if I had a wish list for their engineers it would include giving their cars some longevity.
Header: Steve Jurvetson, CC BY 2.0.
Humans have a need for speed, and students from the Academic Motorsports Club Zurich (AMZ) have set a new acceleration record for an electric vehicle with a 0 to 100 km/h (0 to 62 mph) time of 0.956 seconds.
The mythen features four custom electric hub motors with a total output of 240 kW and a vehicle weight of 140 kg (309 lb) thanks to the use of carbon fiber and aluminum honeycomb. The car was able to get up to speed over only 12.3 m (40 ft)! As with many student design team projects, every component was hand built and designed to optimize the power to weight ratio of the vehicle.
The students from ETH Zurich and Lucerne University of Applied Sciences and Arts were excited to regain the record from the team at the University of Stuttgart, having previously held the title in 2014 and 2016. We suspect that they will find any European EV maker’s engineering department excited for the chance to hire them come graduation.
The UK bank holiday weekend at the end of August is a national holiday in which it sometimes seems the entire country ups sticks and makes for somewhere with a beach. This year though, many of them couldn’t, because the country’s NATS air traffic system went down and stranded many to grumble in the heat of a crowded terminal. At the time it was blamed on faulty flight data, but news now emerges that the data which brought down an entire country’s air traffic control may have not been faulty at all.
Armed with the official incident report and publicly available flight data, Internet sleuths theorize that the trouble was due to one particular flight: French Bee flight 731 from Los Angeles to Paris. The flight itself was unremarkable, but the data which sent the NATS computers into a tailspin came from two of its waypoints — Devil’s Lake Wisconsin and Deauville Normandy — having the same DVL identifier. Given the vast distance between the two points, the system believed it was looking at a faulty route, and refused to process it. A backup system automatically stepped in to try and reconcile the data, but it made the same determination as the primary software, so the whole system apparently ground to a halt.
It’s important to note that there was nothing wrong with the flight plan entered in by the French Bee pilots, and that early stories blaming faulty data were themselves at fault. However we are guessing that air traffic software developers worldwide are currently scrambling to check their code for this particular bug. We’re fortunate indeed that safety wasn’t compromised and only inconvenience was the major outcome.
Air traffic control doesn’t feature here too often, but we’ve previously looked at a much earlier system.
Header image: John Evans, CC BY-SA 2.0.
Cargo bikes can haul an impressive amount of stuff and serve as a car replacement for many folks around the world. While there are more models every year from bike manufacturers, the siren song of a custom build has led [Phil Vandelay] to build his own dream cargo bike.
The latest in a number of experiments in hand-built cargo bike frames, this electrified front-loader is an impressive machine. With a dual suspension and frame-integrated cargo area, this bike can haul in style and comfort. It uses a cable steering system to circumvent the boat-like handling of steering arm long john bikes and includes a number of nice touches like (mostly) internal cable routing.
The video below the break mostly covers welding the frame with [Vandelay]’s drool-worthy frame jig, so be sure to watch Part 2 of the video for how he outfits the bike including the internal cable routing and turning some parts for the cable steering system on the lathe. If you get an urge to build your own cargo bike after following along, he offers plans of this and some of his other cargo bike designs. [Vandelay] says this particular bike is not for the beginner, unlike his previous version built with square tubing.