How Much Of A Battery Pack Does Your Electric Car Need?

December 25, 2017 by 143 Comments

[Elon Musk] recently staged one of his characteristic high-profile product launches, at which he unveiled a new Tesla electric semi-truck. It was long on promise and short on battery pack weight figures, so of course [Real Engineering] smelled a rat. His video investigating the issue is below the break, but it’s not the link that caught our eye for this article. As part of the investigation he also created an online calculator to estimate the battery size required for a given performance on any electric vehicle.

It’s not perfectly intuitive, for example it uses SI units rather than real-world ones so for comparison with usual automotive figures a little mental conversion is needed from kilometres and hours to metres and seconds if you’re a metric user, and miles if you use Imperial-derived units. But still it’s a fascinating tool to play with if you have an interest in designing electric cars or conversions, as you can tweak the figures for your chosen vehicle indefinitely to find the bad news for your battery pack cost.

It’s very interesting from a technical standpoint to see a credible attempt at an electric truck, and we hope that the existing truck manufacturers will show us more realistic prototypes of their own. But we can’t help thinking that the overall efficiency of electric long-distance trucking could be improved hugely were they to make a truck capable of hauling more than one trailer at once. Any safety issues could be offset by giving these super-trucks their own highways, and with such dedicated infrastructure the power could be supplied from roadside cables rather than heavy batteries. In such circumstances these long trains of electrically hauled containers could be rather successful, perhaps we might call them railroads.

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Rubik’s Cube Table Has A Hidden Surprise

December 25, 2017 by 9 Comments

[Nothorwitzer] built a pretty incredible Rubik’s Cube table with hidden storage. The coolest feature of this table is the way it opens. Twisting the top section of the cube causes two drawers to pop out from the sides. The further you turn the top, the more the drawers extend. As the top hits its rotational limit, the lid of the cube lifts up, revealing the entire top section is hollow.

[Nothorwitzer] built the table from plywood, hardboard, and MDF. Hiding inside the base is an old car wheel hub and bearing. The entire rotating system spins on this assembly. The drawers are actuated by an ingenious set of plywood cams which push the two opposing drawers out as the top assembly rotates. Two levers pop the top open.

The attention to detail here is amazing. [Nothorwitzer] build a set of hidden hinges that make the lid invisible, yet allows it to lift up and over the edge of the cube. A spring ensures that the heavy lid will pop open neatly. The lid fit is so close that air pressure ensures the top doesn’t slam down when it is dropped.

While the internal parts of the table are left in bare wood, that the external parts had to match a real Rubik’s Cube. [Nothorwitzer] scrambled a cube, then copied the colors. The panels are made of cut hardboard. Each panel is spray painted, then hot glued to the cube. The body is plywood which [Nothorwitzer] grooved with a router to match the profile of a real Rubick’s Cube.

The project doesn’t end here. [Nothorwitzer] has created a second cube, which is even more tricky. The lid pops by pressing in one section. The drawers operate in a similar way, but there is a lever to engage or disengage the drawer opening. This may be the perfect place to hide your retro gaming systems!

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The Most Tasteful Of Christmas Sweaters Come With A Trainset

December 25, 2017 by 3 Comments

Ah, Christmas, the time of festive good cheer, cherubic carol-singers standing in the crunchy snow, church bells ringing out across the frozen landscape, Santa Claus in his red suit flying down the chimney with a sack of presents, the scent of Christmas meals cooking heavy upon the air, and a Canadian guy wearing a trainset.

Wait a minute, we hear you say, a Canadian guy wearing a trainset? That’s right, not satisfied with the sheer awfulness of his ugly Christmas sweater on its own, [BD594] made it extra-special by incorporating a working Christmas tree trainset into the ensemble. As if the discovery that Christmas tree trainsets are a thing was not enough, we are treated to the spectacle of one on a plywood ring suspended from a particularly obnoxious Christmas-themed garment. Not all hacks are in good taste, and in fairness we have to note that this one is tagged as comedy rather than railroad engineering.

You can view the result in the video below the break. It’s short on technical detail, which is a slight shame as even though there are few mysteries in powering a small trainset it might be interesting to know how the method used to suspend the baseboard. We’d suspect a harness underneath that jumper, as Christmas garments are built for looks rather than strength.

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Low-Power Motor Can Run For Years On A Coin Cell

December 25, 2017 by 29 Comments

Can you run an electric motor for two years on a single lithium coin cell? [IamWe] figured out how to do it, and even though his donut motor doesn’t look like any motor we’ve ever seen before, it’s a pretty solid lesson in low-current design.

The donut motor is really just a brushless DC motor with a sign-pole stator and a multi-pole rotor. The frame of the motor is built from a styrofoam donut, hence the motor’s name. The rotor is a styrofoam sphere with neodymium magnets embedded around its equator. A sharpened bicycle spoke serves as an axle, and clever magnetic bearings provide near-zero friction rotation. The stator coil comes from an old solenoid and is driven by a very simple two-transistor oscillator. [IamWe]’s calculations show that the single CR2032 coin cell should power this motor for over two years. This one looks easy enough to whip up that it might make a nice project for a long winter’s night. Watch it spin in the video below.

This one seems like a perfect entry for the Coin Cell Challenge contest. Sure, it may not be a coin cell jump starter for your car, but our guess is this motor will still be spinning in 2020, and that’s no mean feat.

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Powder Coating With A Fluidized Bed

December 25, 2017 by 16 Comments

There’s no beating the beauty and durability of a high-quality powder-coated part. There’s just something about the look and feel of the finish that goes far beyond mere painting and makes it worth the effort and expense. The typical electrostatic spray powder-coating setup can be expensive, though, and not necessarily suitable for every workpiece.

Enter the fluidized-bed powder coating chamber, perfect for limited runs of small parts, and the brainchild of [Andrew Mayhall]. With a business providing furniture kits based on iron pipe, [Andrew] needed a way to finish flanges and fittings, and powder coating provided the best look. The fluidizer he built is a great alternative to spray coating; it blows air through a bed of fine thermoplastic granules, which causes them to act like a fluid. It’s similar to the fluidized-bed hot tub we recently featured, but on a much smaller scale and with different requirements based on the ultrafine particle size and aggregation properties of the powder. [Andrew] had to add mechanical agitation to achieve a homogeneous fluid bed, and after much experimentation he’s now able to dip preheated parts into the bed and achieve one-step powder coating. The video after the break shows some of the operational details.

Does electrostatic powder-coating sound like more of your thing? No problem – DIY solutions abound, and a homebrew oven to bake your parts may be as close as the nearest file cabinet.

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Image Source: Brannon Dorsey

Art Eavesdrops On Life And Pagers

December 24, 2017 by 32 Comments

Before cell phones, pagers were the way to communicate on the go. At first, they were almost a status symbol. Eventually, they became the mark of someone who couldn’t or wouldn’t carry a cell phone. However, apparently, there are still some users that clutch their pagers with a death grip, including medical professionals. In an art project called HolyPager, [Brannon Dorsey] intercepted all the pager messages in a city and printed them on a few old-style roll printers. The results were a little surprising. You can check out the video below.

Almost all the pages were medical and many of them had sensitive information. From a technical standpoint, [Brannon’s] page doesn’t shed much light, but an article about the project says that it and other art projects that show the hidden world or radio waves are using our old friend the RTL-SDR dongle.

Pagers use a protocol — POCSAG — that predates our modern (and well-founded) obsession with privacy and security. That isn’t surprising although the idea that private medical data is flying through the air like this is. Decoding POCSAG isn’t hard. GNU Radio, for example, can easily handle the task.

We’ve looked at pager hacking in the past. You can even run your own pager network, but don’t blame us if you get fined.

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Hexbright Repair Keeps Torch Out Of Landfill

December 24, 2017 by 26 Comments

The Hexbright was a Kickstarter project from a few years ago, to create an open source, rechargeable LED light. [Nick] quite likes them, and has learned a thing or two about keeping them operational.

The torches have a few key issues which [Nick] lists for us, before outlining the necessary repairs. These problems highlight certain design flaws, something one might expect for a hardware product from a new startup. Components inside are easily damaged if the device is dropped, and there is no reverse polarity protection on the battery.

It’s always disappointing to see a product in the marketplace fail to take into account such rudimentary things, but in the meantime, repair is always possible. The guide highlights the basic parts and tools required, which is important, but also goes the extra mile and gives important hints and tips on how to effectively execute the repair in a quick and easy fashion.

Overall, it may not be a hack, but what [Nick] has done both educated on us the mistakes made by a crowdfunded hardware startup and also taught us how to write a useful and thorough repair guide. It’s not just about the parts that need to be replaced, it’s about the best method to replace them. The details and the order of operations always helps – anyone that’s ever attempted a serious automotive repair knows this, for example.

We see a lot of great repair hacks here – like this excellent use of a 3D printer to reproduce belts for old hardware.