3-Wheeled Electric Skateboard Does Things Differently

February 9, 2022 by Zoe Skyforest 6 Comments

Typically, electric skateboards drive one or more wheels with brushless motors, while keeping everything mounted on otherwise fairly-standard trucks to maintain maneuverability. However, [swedishFeetballs] decided to go a different route, building a 3-wheeled design using some interesting parts.

The build relies on a large combined hub motor and wheel, similar to those you would find on a hoverboard or some electric scooters; this one is a Xiaomi part sourced from eBay. It’s controlled via an off-the-shelf electric skateboard speed controller that comes complete with its own remote.

The hardware is all bolted up to a custom skateboard deck built from scratch to accept the large single rear wheel. Up front, a regular skateboard truck is used. Batteries are mounted under the deck. Reportedly, the board has a top speed of 15 mph, which unsurprisingly matches that of the Xiaomi M365 the hub motor is sourced from.

It’s a neat way to build an electric skateboard, and to be honest we couldn’t be more curious as to how it rides. Unfortunately, only a few seconds of footage is available, but we’ve embedded it below for your watching pleasure!

Meanwhile, you might also be curious as to the benefits of a half-track skateboard. Video after the break.

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China Loves Battery Swapping EVs, But Will They Ever Make It Here?

February 9, 2022 by Zoe Skyforest 122 Comments

Electric vehicles promise efficiency gains over their gas-fuelled predecessors, but the issue of recharging remains a hurdle for many eager to jump on board with the technology. The problem is only magnified for those that regularly street park their vehicles or live in apartments, without provision to charge a vehicle overnight at home.

Battery swapping promises to solve that issue, letting drivers of EVs change out their empty battery for a freshly charged one in a matter of minutes. The technology has been widely panned and failed to gain traction in the US.

However, as it turns out, battery swapping for EVs is actually thing in China, and it’s catching on at a rapid rate.

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Mystery Effect Causing LEDs To Glow During Reflow

February 9, 2022 by Zoe Skyforest 34 Comments

Sometimes you notice something small that nevertheless you can’t explain. [Greg Davill] found himself in just such a situation this week when he noticed some green LEDs glowing dimly when reflowing some boards. Naturally, [Greg] set out to investigate.

The green LEDs were wired up as power indicators, and [Greg] suspected that the polymer caps on the board might be generating a small current somehow that was causing the LEDs to light up ever so slightly. A simple test hooked a polymer cap directly up to a multimeter. When warmed with a heat gun, the meter showed a small current “in the 5-10 uA range.”

Going further, [Greg] soldered an LED to the cap and once again heated it up, this time to 100° C. The LED glowed, continuing to do so for around 60 seconds with heat removed. The mystery also grew deeper – [Greg] noticed that this only happened with “fresh” capacitors. Once they’d been through one heat cycle, the caps would no longer light an LED when warmed up.

It’s a curious case, and has many speculating as to the causative mechanism on Twitter. Explanations from thermoelectric effects to chemical reactions inside the capacitor. If you’ve got the inside scoop on what’s going on here, don’t hesitate to let us know in the comments. Meanwhile, check out some of [Greg]’s best work – a glowing D20 dice featuring a whopping 2400 LEDs.

[Thanks to J Peterson for the tip!]

Keep Track Of Your Google Calendar With This Custom Build

February 2, 2022 by Zoe Skyforest 9 Comments

Keeping track of your appointments on Google Calendar is easy enough if you’re holding a phone or sitting at a computer, but sometimes you just want to know what’s going on at a glance. This desktop calendar build from [andrei.erdei] does just that with plenty of helpful LEDs.

The attract mode is very cool, even if it doesn’t display any actual information.

The design is simple, using WS2812 LEDs to backlight numbers to indicate whether they are weekdays, weekends, anniversaries, holidays, or any other dates of importance. The numerical layout is a nifty perpetual design allowing the display to easily accommodate the structure of any month, even those neat and tidy ones that start on Monday.

The design relies on an ESP-01 to communicate with Google Calendar and display the relevant data. It’s all wrapped up in a 3D printed case, with the printed paper template backlit from behind some smoked acrylic giving a surprisingly professional-looking finish.

If you’re tired of picking up your phone for every last thing, this design could be just what you’re after for keeping track of your appointments. Alternatively, you could always go the hard copy route. Video after the break.

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Underwater Tanks Turn Energy Storage Upside-Down

February 2, 2022 by Zoe Skyforest 129 Comments

Pumped hydro storage is one of the oldest grid storage technologies, and one of the most widely deployed, too. The concept is simple – use excess energy to pump a lot of water up high, then run it back through a turbine when you want to get the energy back later.

With the rise in renewable energy deployments around the world, there is much interest in finding ways to store energy from these often-intermittent sources. Traditional pumped hydro can help, but there is only so much suitable land to work with.

However, there could be a solution, and it lurks deep under the waves. Yes, we’re talking about underwater pumped hydro storage!

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Building Forged Carbon Fiber Wings For Radio Control Cars

February 2, 2022 by Zoe Skyforest 6 Comments

When it comes to building decent aerodynamic devices, you want to focus on getting your geometry accurate, and making sure your parts are strong enough to deal with the force they’re generating. This build from [Engineering After Hours] delivers on those fronts, consisting of a high-downforce wing for a small RC car.

The video points out that, at best, even a decent RC car will have pretty crappy aerodynamic parts from the factory, with a lift-to-drag (L/D)ratio of 2-3:1 at best. This means that, while they may create some small amount of downforce, they’re also creating plenty of drag at the same time.

The dual-element wing designed here is much more efficient, hitting an L/D ratio in the vicinity of 17:1 – a huge improvement. Even a casual eye can note that the design looks a lot more like something you’d see on a full-size car, versus some of the whackier designs seen on toys.

The wing is built with a forged carbon fiber process using 3D-printed molds, to give the wing plenty of strength. Given that it’s built for an RC car that can do over 100 mph, making sure the wing is stiff enough to perform at speed is key.

[Engineering After Hours] does a great job of showing how to prepare the molds, fill them with carbon fiber, and pour the resin, and discusses plenty of useful tips on how to achieve good results with the forged carbon process.

The result is an incredibly impressive rear wing with aerodynamic performance to match its good looks. It may be more complicated than 3D printing, but the results of the work are that much tougher.

We’ve seen other aero experiments from [Engineering After Hours] before, too. Video after the break.

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Will A Kettle Filled With Alcohol Boil Dry?

February 1, 2022 by Zoe Skyforest 31 Comments

The average home kettle is set up to switch off automatically when water reaches its boiling point. But would a kettle filled with alcohol, which has a significantly lower boiling point, actually turn off? [Steve Mould] set out to find out.

The prediction was that a kettle full of 40% strength vodka would boil dry, as the vodka would evaporate before it actually got to a hot enough temperature to cause the kettle’s cutout mechanism to kick in. The experiment was done outside to minimise the dangers from the ethanol vapor. As it turns out, the vapor from the boiling vodka is about 80% ethanol and just 20% water, so eventually the mixture left in the kettle is mostly water and it boils hot enough to trigger the cutout mechanism.

However, the experiment doesn’t end there. Trying again with 99% ethanol, when the fluid started boiling, the kettle switched off even more quickly. So what’s going on?

The kettle in question uses a bimetallic strip, which trips the switch off in the base of the kettle when it gets too hot. There’s also a tube inside the kettle that carries vapor from the internal cavity and lets it pass over the bimetallic strip. When the liquid inside the kettle boils, it forces hot vapor through the tube, out of the kettle and over the bimetallic strip.

This strip triggers at a temperature significantly lower than the boiling point of water; indeed, as long as the liquid in the kettle is fairly hot and is boiling enough to force vapor out the tube, the kettle will switch off. [Steve] points out that it’s a good mechanism, as this mechanism allows the kettle to respond to boiling itself, rather than the arbitrary 100 C point which water technically only boils at when one is at sea level.

It’s an interesting look at a safety system baked into something many of us use every day without even thinking. It’s not the first time we’ve seen [Steve] dive deep into the world of tea-making apparatus, either. Video after the break.

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