Tennis Balls Serve As Decent Bicycle Tires That Don’t Easily Puncture

April 3, 2023 by Lewin Day 41 Comments

Pneumatic tires provide a great ride, great grip, and yet have one fatal flaw — they’re always getting punctured and leaving you stranded. [The Q] decided to solve this problem with a unique design: tires that use tennis balls as the cushioning medium instead.

The build begins with small cut sections of plastic water pipe. These are used as housings to hold tennis balls, which are pressed in with a unique tool of [The Q]’s own construction. The individual ball assemblies are then bolted into a standard bicycle wheel, and a tread from a regular bike tire is stretched around the outside for grip.

It goes without saying that these tires won’t offer the same quality of ride as regular pneumatic bike tires. Nor will the performance be as good, due to the significant extra unsprung weight. They are eye-catching and fun, however. Plus, if you live in an area with tons of nails or prickles, you might find these are just the ticket. Maybe.

We’ve seen some other great bike hacks before, too.

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Tiny Yet Functional Bike Built From Scratch

March 31, 2023 by Lewin Day 10 Comments

Sometimes, you just want to go ride your bike in the great outdoors, but you can’t be bothered throwing it in the back of the car. That wouldn’t be a problem if you rode this latest build from [The Q]: a bike small enough to fit in a handbag.

The build starts by customizing a rollerblade wheel to act as the driven rear wheel of the bike. It’s fitted with a tiny sprocket allowing it to be chain driven. Welding some steel tubes then nets a small diamond-layout bike frame. It’s fitted with a chain ring, pedals, and steering assembly just like a full-sized bike, just in absolute miniature.

Riding the bike is “uncomfortable,” in [The Q]’s own terms, but entirely possible. It basically requires the same level of contortion and technique as displayed by the clowns of your local circus. Don’t expect to use it as viable transportation, though. Walking would be much faster.

We’ve seen [The Q] build some wild bikes before, too, like this great hubless design. Video after the break.

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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!