Electric Skateboard Becomes Mobile Skate Park

March 30, 2023 by Bryan Cockfield 4 Comments

While building a skate park might not appear to have much in common with software development, at they very least, they both suffer from a familiar problem: scalability. Bigger skate parks need more ramps and features, and there’s no real way to scale up a construction project like this efficiently like you could with certain kinds of software other than simply building more features. This was something [Kirk] noticed, but was able to scale up a skate park in a way we’ve never thought of before. He built a mobile skateboard ramp that can turn any place into a skate park.

The mobile and approximately sidewalk-width platform is able to move around thanks to an electric skateboard as its foundation. It adds a NVIDIA Jetson Nano for control with a PS4 controller for input, although steering a skateboard with an actuator took a few prototypes to figure out since skateboards are designed to be steered by shifting the rider’s weight. Since they are already designed to carry a human-amount of weight, though, it was at least able to tote the ramp around with relative ease. Another problem was lowering the ramp into position when it got to the desired area, but with an electrically-controlled jack and a few rounds of debugging was eventually able to do this without much issue.

With all of that project development behind him, [Kirk] can finally realize his dream of having ramps scattered all across his neighborhood like in the classic videogame Paperboy, without needing to build them all individually or ask for permission to place them around his neighbor’s homes. For any future iterations of this build, we might consider adding tank tracks to the electric skateboard for better off-road performance, like facilitating a jump across a patch of grass.

Weird Electric Jet Skis Are Hitting The Waves

March 29, 2023 by Lewin Day 68 Comments

When it comes to reducing emissions from human sources, we’re at the point now where we need to take a broad-based approach. It’s not enough to simply make our cars more efficient, or start using cleaner power plants. We need to hit carbon zero, and thus everything has to change.

To that end, even recreational watercraft are going electric in this day and age. Several companies are developing motor-powered models that deliver all the fun without the emissions. But to do that, they’re taking to the air.

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Bus Stop Bloom Filter

March 27, 2023 by Matthew Carlson 19 Comments

Imagine you’re sitting on a nice bench, the sun shines warmly, and a bus pulls up. You’re headed to Stendal from Osnabrück, how can you tell if you should get on that bus? [Julian Vanecek] is trying to turn that from an O(n) problem to an O(1) one with a Bloom filter right at the bus stop.

In [Julian’s] sample code, each stop is a 3-bit number that can be encoded into a 192-bit array. Your ticket is just that 3-bit number encoded, so you can look at the graphic on the side of the incoming bus, match it against your ticket, and hop on. Gone are the days of waiting for the little LED screen to cycle through all the stops, waiting for yours to come up. Your ticket should have just a few boxes filled in so it is relatively quick to search against the bus’s graphic.

Of course, there is a potential for a false positive rate. [Julian] points out that this can be tuned to prevent errors and has achieved a < 0.5% false positive rate using the Deutsche Bahn bus system. The code is written in Python and available on GitHub. Perhaps buses could have a large flip-dop display on the side, to adjust to show which stops they’re headed to next. Additionally, it doesn’t encode which stops are next, just which stops the bus will eventually go to.

In the video after the break, [Julian] explains how the system works. Whether it would be ultimately adopted is somewhat beside the point. We love the seeing people re-imagining ideas and trying to apply new techniques to improve the things around them.

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Who Needs Gasoline When You’ve Got Sodium?

March 23, 2023 by Dave Rowntree 58 Comments

YouTuber and serial debunker [Thunderf00t] was thinking about the use of sodium to counteract global warming. The theory is that sodium can be used as a fuel when combusted with air, producing a cloud of sodium hydroxide which apparently can have a cooling effect if enough of it is kicking around the upper atmosphere. The idea is to either use sodium directly as a fuel, or as a fuel additive, to increase the aerosol content of vehicle emissions and maybe reduce their impact a little.

One slight complication to using sodium as a fuel is that it’s solid at room temperature, so it would need to be either delivered as pellets or in liquid form. That’s not a major hurdle as the melting point is a smidge below 100 degrees Celsius and well within the operating region of an internal combustion engine, but you can imagine the impact of metal solidifying in your fuel system. Luckily, just like with solder eutectic mixes, sodium-potassium alloy happens to remain in liquid form at handleable temperatures and only has a slight tendency to spontaneously ignite. So that’s good.

Initial experiments using ultrasonic evaporators proved somewhat unsuccessful due to the alloy’s electrical conductivity and tendency to set everything on fire. The next attempt was using a standard automotive fuel injector from the petrol version of the Ford Fiesta. Using a suitable container, a three-way valve to allow the introduction of fuels, and an inert argon feed (preventing spontaneous combustion in the air), delivering the liquid metal fuel into the fuel injector seems straightforward enough.

[Thunderf00t] started with ethanol, then worked up to pentane before finally attempting to use the feisty sodium-potassium, once the bugs had been shaken out of the high-speed video setup. [Thunderf00t] does stress the importance of materials selection when handling this potential liquid metal fuel, since it apparently just bursts into flames in a violent manner on contact with incompatible materials. Heck, this stuff even reacts with PTFE, which is generally considered a very resistant material. We’re totally convinced we’d not like to see this stuff being pumped from a roadside gas station, at all, but it sure is a fun concept to think about.

Sodium-Potassium alloy doesn’t feature on these pages too often, but here’s a little fountain of the stuff, just because why not?

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Wireless Charging On A Massive Scale

March 21, 2023 by Bryan Cockfield 26 Comments

Despite the increasing popularity of various electric vehicles, the limits of battery technology continue to be a bottleneck in their day-to-day use. They don’t behave well in extreme temperatures, they can wear out quickly, and, perhaps most obviously, charging them is often burdensome. Larger batteries take longer to charge, and this can take a lot of time and space, but this research team from Chalmers University are looking to make this process just a little bit easier.

The group has been developing an inductive wireless charging method for large vehicles including cars, trucks, busses, and ferries that can deliver 500 kW across a 15 cm (6 inch) air gap. The system relies on a silicon carbide semiconductor and extremely thin copper wire in order to make all this happen, and eliminates the need for any human involvement in the charging process. This might not be too much of a hassle for plugging in an electric car, but for larger vehicles like busses and ferries traditional charging methods often require a robot arm or human to attach the charging cables.

While this technology won’t decrease the amount of time it takes batteries to charge, it will improve the usability of devices like these. Even for cars, this could mean simply pulling into a parking space and getting the car’s battery topped off automatically. For all the talk about charging times of batteries, there is another problem looming which is that plenty of charging methods are proprietary as well. This charger attempts to develop an open-source standard instead.

Thanks to [Ben] for the tip!

Hacking Skis, Rules, And Friendships

March 13, 2023 by Bryan Cockfield 15 Comments

The American Birkebeiner is the second largest cross-country skiing race in the world and is quite a big deal within that sport. At 55 kilometers it’s not a short event, either, requiring a significant amount of training to even complete, let alone perform well enough to be competitive. Around a decade ago, friends [Joe] and [Chris] ran afoul of the rules when [Joe] accidentally won the race wearing [Chris]’s assigned entry number, a technicality that resulted in both being banned from the race for two years. Now they’re back, having learned their lesson, and are strictly adhering to those rules this time using these tandem cross-country skis.

The idea for this build was to make sure they could both compete in the race and win because they’d compete in a category no one enters, mostly because it effectively didn’t exist before these two invented it. This required a custom set of skis, but since ski manufacturers don’t typically make skis for two people, they had to get creative. The duo picked up the longest pair of skis they could find at their local ski shop, moving the bindings forward on the skis to make room for the second set of bindings that were added to the back.

This presented a few unique challenges, the first of which is that cross-country skis typically use a special material on the bottom of the skis which grabs the snow to make uphill travel possible, and with the wider distribution of weight this material wasn’t functioning at peak efficiency. The other problem was the stress on the bindings caused by two riders, especially during a crash. This eventually resulted in a broken binding while [Joe] and [Chris] were training. They then upgraded to a more modern pair of skis rated for a single 269-pound rider, had the bindings fitted for two riders, and added a special grip tape over the larger area on the bottom of the ski.

After four months of training and getting in sync, the two were ready for the race. The results are covered in a second video linked below, and while neither of them won the overall race this time, they did finish the event with in-tact skis, first in the new “tandem” class, and completely within the bounds of the strict rules of the race as well. Although winter is winding down in the northern hemisphere, for any of our southern friends looking for some other things to do with an old set of skis for the upcoming winter season, take a look at this sled which adapts some alpine skis to achieve some extremely high speeds.

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27 Litres And 12 Cylinders, With A Practical Station Wagon Body

March 10, 2023 by Jenny List 39 Comments

If you were to name one of the most famous individual road cars in the world, what would it be? If you’re British and of a Certain Age, then it’s possible your nomination is for sale, because “The Beast”, the one-off creation of [John Dodd] using a 27-litre Rolls-Royce Merlin aero engine, is up for auction. The Late Brake Show’s [Jonny Smith] has given it a drive, and we’ve pasted the resulting video below the break.

A second-hand motor isn’t usual Hackaday fare, but it’s the manner of this car’s building which we think will draw you in. [John] originally acquired somebody’s failed project featuring not a Merlin but its de-tuned derivative intended for tanks. He solved the problem of finding a transmission able to handle the immense power, and built it up with a pretty 1970s coupe body. After a fire a few years later he commissioned a new body from a dragster manufacturer, which is the wildly period estate car you’ll see in the video. It famously originally had a Rolls-Royce Cars grille, for which he ended up in court in the 1980s as the carmaker sought successfully to have it removed.

The tale of this car is one of epic scale hackery, as there is quite simply nothing else like it. It was once the world’s most powerful road car, and remains capable of well over 200 miles per hour. Sadly we couldn’t afford to buy it even if we could fit its immense length in our parking space.

Hungry for more epic British car hackery? Have we got the roadster for you!

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