Will The Lilium Jet Work? A Deep-Dive Into The Physics Behind EVTOL Aircraft

June 22, 2023 by 26 Comments

The Lilium Jet is a proposed eVTOL (electric Vertical Take Off and Landing) aircraft that the German company Lilium GmbH has claimed it will bring to the market ‘soon’, which would made it the first eVTOL aircraft in the world to enter into commercial service. As anyone who has any experience with VTOL knows, it’s a tricky subject to engineer, let alone when you want to do it fully electric. In a deep-dive video on the Lilium Jet and eVTOL in general, [John Lou] goes through the physics behind VTOL take-off, landing and flight, as well as range and general performance.

It is clear that Lilium’s presented aircraft concept has many issues, some of which are due to new and unproven technologies, while others seem to be founded in over-promising and likely under-delivering. With Lilium having signed a number of contracts to deliver the first Pioneer Edition Lilium Jets and commercial service promised by 2025, it’s hard to ignore that the first full prototype of the 7-seater Lilium Jet is supposed to fly this year.

Although as [John] points out in the video, eVTOL is not an impossible concept, it is important to remain realistic about what is physically possible, and not seek to push the boundaries. When the UK introduced its first mass-produced VTOL jet in the form of the Harrier, it too faced an uncomfortable time as bugs got ironed out. As these eVTOL aircraft would be carrying real human passengers, it’s a good place to realize that although you can pick a fight with physics, you will never come out on the winning side.

Hopefully Lilium realizes this too, and these sleek, battery-powered aircraft will truly take to the skies in a few years.

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A Ride-On Picnic Table For Those Idylic Summer Evenings

June 12, 2023 by 12 Comments

For most outsiders the Netherlands is a country of picturesque cities, windmills, tulips, and maybe those famous coffee shops. Head away from the coast though and you enter the country’s rural hinterland, farming country with lush green fields, dairy cattle, and farm lads doing what they do best, which is hacking old machinery to do crazy things under those wide skies. [Plodno] are based on a farm somewhere in the eastern Netherlands, and the latest of these lads’ creations is a motorised picnic table (Dutch language, you’ll need YouTube translated subtitles).

This is farm hacking at its best, with a scrap FIAT hatchback donating its running gear to a welded tubular frame, with a chain drive to a small single-cylinder engine. There’s no suspension save for the air in the tyres, the steering column is vertical, and the brake is a single inboard disk on the rear axle. Perhaps it’s fortunate that the intended beating heart, a Kawasaki motorycle engine, was misfiring, as it would have been truly lethal with that much power. We’re not too convinced at the legality of taking such a contraption on the public road in the Netherlands, but they seem to get away with it. Take a look at the build in the video below the break.

Here at Hackaday we like a good hacky farm build, even though sometimes they’re not so well-assembled.

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Tree Planting Festivals, Air Cannons, Self-Burying Seeds, And The Complexities Of Reforestation

June 8, 2023 by 20 Comments

At first glance the problem of how to plant trees would seem to be a straightforward one: take a seed, jam it into the soil and let nature take its course. Or alternatively do much the same with a sapling that already got a start in a nice, comfortable greenhouse before leaving it to its own devices. To the average person this is generally the point where it’s considered a ‘done deal’, but one only has to take a look at the average survival rate of saplings out in the wild to perish that thought.

Each environment offers its own set of challenges when it comes to reforestation, which can perhaps be considered ironic as many of these trees are being planted where forests used to be, albeit centuries ago in many cases. There are the easy spots, such as flat fields, with rich soil, ample rain and mild weather, to the challenging terrain of Iceland, or mountainous terrain. Here the logistics are challenging and where once rich forests flourished, the very landscape seems adamant to reject this botanic intrusion.

Further complicating matters here are the myriad of reasons why we’re looking at planting so many new trees that it has even become an internet thing, as with the 2019 ‘Team Trees’ 20 million new trees challenge. So how did we get here, why exactly are we doing all of this, and how much of these attempts do bear fruit?

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A blue work tricycle (single front wheel with platform between two rear wheels) sits on an asphalt path with trees and wildflowers in the background. A boxy, white camper with a front overhanging the bike seat is attached to the platform. It has a yellow stripe and curtains like many campers did in the 1970s. One white male is exiting the door of the camper while his brother is standing to the left of the camper by the bike seat.

Bike Camper With Retro Flair

May 23, 2023 by 33 Comments

As we’re approaching summer here in the Northern Hemisphere, thoughts naturally turn toward road trips. While most people do this in their car, the [Dangie Bros] built a 500 lb bike camper for their own take on the great American Road Trip.

Taking a maximalist approach not seen in most bike campers, this behemoth has a working sink, propane stove, seating area, and an upstairs sleeping area. A small window in the front of the camper opens to let the passenger inside converse with the person pedaling, and a solar panel charges a small battery for lights and a roof fan.

While the camper is very ’70s retro-chic, its lack of assist (other than the passenger getting out to push) meant that on the second day of their road trip they resorted to towing the camper behind a second bike in a pseudo-tandem arrangement. The fold out bed takes some design cues from RVs, but clearly needed more reinforcement since it collapsed partway through the night. With an e-assist and some refinements, this could be comfortable (albeit slow) way to go bike glamping.

If you’d like to try your own hand at a bike camper but do it more aerodynamically and attached to an assisted bike, checkout this teardrop trailer or this bike camper.

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Remote-Controlled Hypercar Slices Through Air

May 23, 2023 by 17 Comments

Almost all entry-level physics courses, and even some well into a degree program, will have the student make some assumptions in order to avoid some complex topics later on. Most commonly this is something to the effect of “ignore the effects of wind resistance” which can make an otherwise simple question in math several orders of magnitude more difficult. At some point, though, wind resistance can’t be ignored any more like when building this remote-controlled car designed for extremely high speeds.

[Indeterminate Design] has been working on this project for a while now, and it’s quite a bit beyond the design of most other RC cars we’ve seen before. The design took into account extreme aerodynamics to help the car generate not only the downforce needed to keep the tires in contact with the ground, but to keep the car stable in high-speed turns thanks to its custom 3D printed body. There is a suite of high-speed sensors on board as well which help control the vehicle including four-wheel independent torque vectoring, allowing for precise control of each wheel. During initial tests the car has demonstrated its ability to  corner at 2.6 lateral G, a 250% increase in corning speed over the same car without the aid of aerodynamics.

We’ve linked the playlist to the entire build log above, but be sure to take a look at the video linked after the break which goes into detail about the car’s aerodynamic design specifically. [Indeterminate Design] notes that it’s still very early in the car’s development, but has already exceeded the original expectations for the build. There are also some scaled-up vehicles capable of transporting people which have gone to extremes in aerodynamic design to take a look at as well.

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AirTags, Tiles, SmartTags And The Dilemmas Of Personal Tracking Devices

May 22, 2023 by 17 Comments

In an ideal world we would never lose our belongings, and not spend a single hour fruitlessly searching for some keys, a piece of luggage, a smartphone or one of the two dozen remote controls which are scattered around the average home these days. Since we do not live in this ideal world, we have had to come up with ways to keep track of our belongings, whether inside or outside our homes, which has led to today’s ubiquitous personal tracking devices.

Today’s popular Bluetooth-based trackers constantly announce their presence to devices set up to listen for them. Within a home, this range is generally enough to find the tracker and associated item using a smartphone, after which using special software the tracker can be made to sound its built-in speaker to ease localizing it by ear. Outside the home, these trackers can use mesh networks formed by smartphones and other devices to ‘phone home’ to paired devices.

This is great when it’s your purse. But this also gives anyone the ability to stick such a tracker device onto a victim’s belongings and track them without their consent, for whatever nefarious purpose. Yet it is this duality between useful and illegal that has people on edge when it comes to these trackers. How can we still use the benefits they offer, without giving stalkers and criminals free reign? A draft proposal by Apple and Google, submitted to the Internet Engineering Task Force (IETF), seeks to address these points but it remains complicated.

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An Open-Source 4-Shaft Portable Loom

May 14, 2023 by 18 Comments

Part of writing for Hackaday involves doing the rounds of our community’s events in search of amazing projects for your delectation. This weekend it was a trip to Maker Faire Delft, thanks to the wonders of the European Interail scheme. Once on the site, [Aslı Aydın Aksan]’s 4-shaft weaving loom immediately caught our eye. This is an open-source portable folding loom design. In weaving terms, shafts are sliding vertical frames. As the name implies, this loom has four, which allow different sets of warp threads to be brought to the surface of the weave at different times. This feature makes it capable of weaving complex patterns in the fabric and thus makes it a very interesting project indeed.

The frame of the loom is laser-cut ply, cunningly designed such that when not in use it can be folded into a compact unit. The attachments are all 3D-printed PLA in the prototypes, the comb is laser-cut acrylic, and the heddles are 3D printed in a flexible material. These last components conceal a further trick, they’re designed to be extra-easy to move between shafts on the fly, allowing even more complex patterns to be created.

All in all this is one of those special projects that comes out of the blue and raises the bar on all in its class. If there’s another 4-shaft loom this accessible, we’ve yet to hear of it.

It’s not the first loom we’ve covered, however, this one wasn’t nearly as accomplished.