Casting Skateboard Wheels With A 3D Printed Mold

December 26, 2020 by Tom Nardi 7 Comments

We’ll admit that most of the Hackaday staff wouldn’t get too far on a skateboard, but that doesn’t mean we can’t appreciate the impressive DIY wheels that [Chris McCann] has managed to cast using 3D printed molds. From unique color combinations to experimental materials, the process certainly opens up some interesting possibilities for those looking to truly customize their rides. Though it’s worth noting there’s a certain element of risk involved; should a set of homemade wheels fail at speed, it could go rather poorly for the rider.

Both the STL and STEP files for the mold have been released under the Creative Commons Attribution 4.0 license, meaning anyone with a 3D printer can follow along at home. Unfortunately, it’s not quite as simple as clicking print and coming back to a usable mold. Because of the layer lines inherent to FDM 3D printing, the inside of the mold needs to be thoroughly sanded and polished. [Chris] mentions that printing the mold in ABS and using vapor smoothing might be a workable alternative to elbow grease and PLA, but he hasn’t personally tried it yet.

Once you’ve got the three part mold printed, smoothed, and coated with an appropriate release agent like petroleum jelly, it’s time to make some wheels. The core of each wheel is actually 3D printed from PETG, which should give it pretty reasonable impact resistance. If you have access to a lathe, producing aluminum cores shouldn’t be too difficult either. With the core loaded into the mold, urethane resin is poured in through the top until all the empty space is filled.

But you’re not done yet. All those little air bubbles in the resin need to be dealt with before it cures. [Chris] puts his filled molds into a pressure chamber, though he mentions that vacuum degassing might also be a possibility depending on the urethane mixture used. After everything is solidified, the mold can easily be taken apart to reveal the newly cast wheel.

While there’s often some trial and error involved, 3D printing and resin casting are an undeniably powerful combination. If you can master the techniques involved, you can produce some very impressive parts that otherwise would be exceptionally difficult to produce on a hacker’s budget. Especially when you’re ready to start casting molten metal.

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Tank Track Skateboard

December 25, 2020 by Danie Conradie 8 Comments

As electric skateboards kits and components become more commonly available, you really need to do something different to make your custom board stand out. [Emiel] [The Practical Engineer] has managed to do this by building a half-track skateboard. (Video, embedded below.)

Except for the front trucks, fasteners and bearings, all the mechanical components on the board were custom-made. The sturdy rear chassis and the track sections were machined from aluminum plate, and the wheels and track linkages were machined from POM/Delrin. The large carbon fiber deck and the polyurethane pads on the tracks were custom molded, which [Emiel] covered in detail in separate videos, also below. Two beefy brushless motors drive the tracks and are powered by LiPos in enclosed in the sheet metal electronics box. The final product looks very well-built and refined, especially considering most of the work happened in a tiny 2 m x 3 m workshop.

It looks like the board handles gravel paths well, but we would really like to see how it performs on soft surfaces like sand, where even off-road skateboards can struggle. It struggled a bit with low RPM torque, so a slight gearing change is in this board’s future.

Everything is cooler with tank tracks. If you’re willing to live with plastic tracks, 3D printing is a viable option, as demonstrated by [rctestflight]’s tracked rover and [Ivan Miranda]’s tank skateboard. Continue reading “Tank Track Skateboard” →

Radio Controlled Hovercraft Apes The SR.N1

December 15, 2020 by Lewin Day 7 Comments

Hovercraft never really caught on as regular transportation, but they are very cool. The Saunders-Roe SR.N1 was the very first practical example of the type, and served as a research vehicle to explore the dynamics of such vehicles. [mr_fid] was looking for a lockdown project, and set about crafting a radio controlled replica of his own.

The build is crafted out of a canny combination of plywood and balsa, the latter substituted in sections within the plywood hull to save weight. A pair of brushless outrunner motors are mounted in the central duct to provide lift, fitted with counter-rotating propellers in order to avoid torque effects on handling. Steering is via puff ports a la the original design, which allows the craft to spin very quickly in place to much amusement and no practical effect. The skirt is of a colorful design, carefully assembled out of polyurethane-coated nylon.

While it’s not the quickest way to build a hovercraft, it’s all the more beautiful for its attention to the details and function of the original prototype craft. We particularly like the sharp handling thanks to the puff port design. If you’re looking for a weirder design however, consider this Coanda Effect build. Video after the break.

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RC Starship Perfects Its Skydiving Routine

December 13, 2020 by Tom Nardi 12 Comments

There’s a good chance you already saw SpaceX’s towering Starship prototype make its impressive twelve kilometer test flight. While the attempt ended with a spectacular fireball, it was still a phenomenal success as it demonstrated a number of concepts that to this point had never been attempted in the real world. Most importantly, the “Belly Flop” maneuver which sees the 50 meter (160 foot) long rocket transition from vertical flight to a horizontal semi-glide using electrically actuated flight surfaces.

Finding himself inspired by this futuristic spacecraft, [Nicholas Rehm] has designed his own radio controlled Starship that’s capable of all the same aerobatic tricks as the real-thing. It swaps the rocket engines for a pair of electric brushless motors, but otherwise, it’s a fairly accurate recreation of SpaceX’s current test program vehicle. As you can see in the video after the break, it’s even able to stick the landing. Well, sometimes anyway.

Just like the real Starship, vectored thrust is used to both stabilize the vehicle during vertical ascent and help transition it into and out of horizontal flight. Of course, there are no rocket nozzles to slew around, so [Nicholas] is using servo-controlled vanes in the bottom of the rocket to divert the airflow from the motors. Servos are also used to control the external control surfaces, which provide stability and a bit of control authority as the vehicle is falling.

As an interesting aside, Internet sleuths looking through pictures of the Starship’s wreckage have noted that SpaceX appears to be actuating the flaps with gearboxes driven by Tesla motors. The vehicle is reportedly using Tesla battery packs as well. So while moving the control surfaces on model aircraft with battery-powered servos might historically have been a compromise to minimize internal complexity, here it’s actually quite close to the real thing.

Unfortunately, the RC Starship made a hard landing of its own on a recent test flight, so [Nicholas] currently has to rebuild the craft before he can continue with further development. We’re confident he’ll get it back in the air, though it will be interesting to see whether or not he’s flying before SpaceX fires off their next prototype.

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Remoticon Video: Learn How To Hack A Car With Amith Reddy

December 10, 2020 by Dan Maloney 14 Comments

There was a time not too long ago when hacking a car more often than not involved literal hacking. Sheet metal was cut, engine cylinders were bored, and crankshafts were machined to increase piston travel. It was all in the pursuit of milking the last ounce performance out of every drop of gasoline, along with a little personal expression in the form of paint and chrome.

While it’s still possible — and encouraged — to hack cars thus, the inclusion of engine control units and other systems to our rides has created an entirely different universe of car hacking options, which Amith Reddy distilled into his very popular workshop at the 2020 Remoticon. The secret sauce behind all the hacks you can accomplish in today’s drive-by-wire cars is the Controller Area Network (CAN), the network used to connect the array of sensors, actuators, and controllers that lie under the metal and plastic of modern cars.

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Hyperloop: Fast, But At What Cost?

December 9, 2020 by Lewin Day 162 Comments

When it comes to travelling long distances, Americans tend to rely on planes, while the Chinese and Europeans love their high speed rail. However, a new technology promises greater speed with lower fares, with fancy pods travelling in large tubes held at near-vacuum pressures. It goes by the name of Hyperloop.

Virgin Hyperloop recently ran the first-ever passenger test of a Hyperloop vehicle, reaching 100 mph on a short test track.

Spawned from an “alpha paper” put together by Elon Musk in 2013, the technology is similar to other vactrain systems proposed in the past. Claiming potential top speeds of up to 760 mph, Hyperloop has been touted as a new high-speed solution for inter city travel, beating planes and high speed rail for travel time. Various groups have sprung up around the world to propose potential routes and develop the technology. Virgin Hyperloop are one of the companies at the forefront, being the first to run a pod on their test track with live human passengers, reaching speeds of 100 mph over a short 500 meter run.

It’s an exciting technology with a futuristic bent, but to hit the big time, it needs to beat out all comers on price and practicality. Let’s take a look at how it breaks down.

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North American Field Guide To Rail Cars

December 9, 2020 by Kristina Panos 55 Comments

Trains are one of the oldest and most reliable ways we have of transporting things and people over long distances. But how often do you think about trains? Where I live, they can clearly be heard every hour or so. I should be used to the sound of them by now, but I like it enough to stop what I’m doing and listen to the whistles almost every time. In the early morning quiet, I can even hear the dull roar as it rumbles down the track.

I recently got a front row seat at a railroad crossing, and as the train chugged through the intersection, I found myself wondering for the hundredth time what all the cars had in them. And then, as I have for the last twenty or thirty years, I wondered why I never see a caboose anymore. I figured it was high time to answer both questions.

Boxcar

Boxcars are probably the most easily identifiable after the engine and the caboose.

Boxcars carry crated and palletized freight like paper, lumber, packaged goods, and even boxes. Refrigerated box cars carry everything from produce to frozen foods.

Boxcars (and barns for that matter) are traditionally a rusty red color because there were few paint options in the late 1800s, and iron-rich dirt-based paint was dirt cheap.

Flat Car

Standard, no-frills flat cars are the oldest types of rail cars. These are just big, flat platform cars that can carry anything from pipe, rail, and steel beams to tractors and military vehicles.

Flat cars come in different lengths and are also made with and without bulkheads that help keep the cargo in place. Some flat cars have a depression in the middle for really tall or heavy loads, like electrical transformers.

Auto Rack

As the name implies, auto racks carry passenger cars, trucks, and SUV from factories to distributors. They come in two- and three-level models, although there have been specialized auto racks over the years.

Perhaps the strangest auto rack of them all was the Vert-a-Pac. When Chevrolet came up with the Vega in the gas-conscious 1970s, they wanted to be able to move them as cheaply as possible, so they shipped the cars on end. If you’re wondering about all the fluids in the car when they were upended, a special baffle kept oil from leaking out, the batteries were capped, and the windshield washer fluid bottle was positioned at an angle.

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