Behold The Track-Twisting Möbius Tank

November 18, 2023 by Donald Papp 17 Comments

It started with someone asking [James Bruton] about using a Möbius strip as a tank tread. He wasn’t sure what the point would be, but he was willing to make one and see what happened. Turns out it works reasonably well!

The grey plates are responsible for tensioning the tracks. Designing them as separate pieces means rework for fine-tuning avoids having to re-print structural parts.

The main design challenge was creating a tread system that would allow for the required rotation. [James] designed in the ability for each link to rotate about 18 degrees, and ensured plenty of open space on the upper side of the drive train to accommodate a full 180 degree twist. It took a little fine-tuning and looks a bit trippy, but in the end works about as well as a regular tread system.

[James] shows off a good technique to keep in mind when constructing big assemblies like this tank. It takes a lot of time and material to print large pieces, and in such cases it’s especially important to minimize rework. [James] therefore designs smaller, separate pieces as interfaces to other parts. This way, if changes are needed down the line (for example, to adjust motor placement or change tension on parts), only a smaller interface piece needs to be redone instead of having to re-print a huge part.

The unit uses an Arduino Mega, two 24 V gearmotors to drive each tread independently, an RC radio receiver, and some beefy BTS7960 DC motor drivers to drive the motors.

[James]’ unit is pretty big, but we’ve also seen 3D printed tanks capable of carrying a human driver. It’s clear that build plate size doesn’t seem to limit tank designs. Watch the Möbius tank get built and drive around in the video, just below the page break.

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Electric Truck Carries 74 Tons

November 17, 2023 by Al Williams 73 Comments

Thanks to the various measurement systems in use, we aren’t sure if Volvo has created an electric truck that carries 74 metric tons, 74 short tons, or 74 long tons, but either way, that’s a lot of cargo for an electric truck. After all, that’s somewhere between 148,000 and 163,000 pounds (or 67,000 kg to 74,000 kg). That’s about three times what a typical 18-wheeler with a flatbed carries in the US. In fact, on a U.S. road, trucks typically have to weigh less than 80,000 pounds, including the truck to be legal.

Well, the monster electric Volvo has two trailers, so it is more fair to compare it to turnpike doubles, which typically carry about 148,000 pounds of cargo. The truck operates 12 hours a day and charges when the driver takes a break. At the depot, charging is from two 180 kW chargers that use green electricity, according to the company. The truck has been running for a few months, although we haven’t heard more about how successful or unsuccessful it might be.

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Diesel Station Wagon Runs On Plastic

November 15, 2023 by Bryan Cockfield 58 Comments

Old diesel engines from various car manufacturers like Mercedes and Volkswagen are highly prized even in modern times. Not only were these engines incredibly reliable and mechanically simple, but they can easily be modified to run on a wide variety of fuels. It’s common to see old Volkswagen Jettas or Mercedes 300Ds running on used vegetable oil or any other free flammable liquid that might otherwise end up in the garbage. [Gijs Schalkx] has an diesel Volvo 240 wagon, and rather than compete with all the other diesel owners looking for cooking oil, he modified this one to run on plastic waste instead. (Google Translate from Dutch)

While our Dutch language skills aren’t the best, what we gather about this project is that it uses standard solid plastic waste for fuel, but an intermediate step of cooking the plastic into a liquid is first needed. The apparatus on the roof is actually a plastic refinery which uses a small wood fire to break the plastic molecules into usable hydrocarbons, which are then sent to the engine for burning. The car is street legal and seems to operate like any other diesel of this vintage, although the fuel delivery system may not be able to provide it enough to get it going at very high speeds.

While it is possible to use wood to produce wood gas for fuel in an internal combustion engine like this wood gas-powered lawnmower, the hydrocarbon strings in plastic are essentially stabilized hydrocarbons from refining oil and have potentially much more available energy. Releasing this energy is generally difficult enough that used plastic is simply landfilled. [Gijs Schalkx] has made plenty of alternative fuel vehicles, too, like this moped that used locally-harvested swamp gas to ride around town.

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A large, teardrop-shaped van with a wide, friendly face sits in a grassy field. A grey canvas pop top is opened on its top and solar panels extend from either side of its roof, making it look somewhat like a large insect with wings extended.

An Off-Grid EV Camper Van

November 14, 2023 by Navarre Bartz 34 Comments

Despite our predilection for creature comforts like electricity, it can be nice to get away from it all from time-to-time. Students from Eindhoven University of Technology developed Stella Vita to let you glamp from the power of the sun alone.

Solar-powered vehicles have been plying the highways for decades, but we’re only now getting vehicles with multiple seats that could potentially be used for transport outside of protected race conditions. While production vehicles that can charge off the sun are yet to appear in any appreciable numbers, universities are continuing to push the envelope of what’s possible in a solar car.

Stella Vita is a whale shark-esque camper van designed to be as aerodynamic as possible while still housing all the accoutrements one would want when car camping including a large bed, inductive cooktop, fridge, shower, sink, toilet, and standing room via a pop top. The 2 kW solar array expands to 4 kW when parked via two wings extending from the pop top that also function as awnings for your base camp. By keeping the car lightweight (1,700 kg or 3,700 lb) and aerodynamic, it can go about 600 km (370 mi) on a single charge with its 60 kWh battery.

While it’s still experimental, the team took Stella Vita on a road trip of 3,000 km (1,900 mi) to the south of Spain and were able to get there with only a couple charging stops to account for technical difficulties. A full charge on solar alone takes 2-3 days, which we can see being a convenient amount of time to stop in one spot for your outdoor adventures before heading home or to your next destination.

If you want to build a slightly smaller off-grid camper that’s fueled by coffee instead, you might want to check out this bike camper or this other example.

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An Open-Source Ebike Motor Controller

November 8, 2023 by Bryan Cockfield 18 Comments

DIY e-bikes are often easy to spot. If they’re not built out of something insane like an old washing machine motor, the more subtle kits that are generally used still stand out when compared to a non-assisted bike. The motors tend to be hub- or mid-drive systems with visible wires leading to a bulky battery, all of which stand out when you know what to look for. To get a stealthy ebike that looks basically the same as a standard bicycle is only possible with proprietary name-brand solutions that don’t lend themselves to owner repair or modification, but this one has at least been adapted for use with an open source motor controller.

The bike in use here is a model called the Curt from Estonian ebike builder Ampler, which is notable in that it looks indistinguishable from a regular bicycle with the exception of the small 36-volt, 350-watt hub motor somewhat hidden in the rear wheel. [BB8] decided based on no reason in particular to replace the proprietary motor controller with one based on VESC, an open-source electric motor controller for all kinds of motors even beyond ebikes. Installed on a tiny Arduino, it fits inside the bike’s downtube to keep the stealthy look and can get the bike comfortably up to around 35 kph. It’s also been programmed to turn on the bike’s lights if the pedals are spun backwards, and this method is also used to change the pedal assist level, meaning less buttons and other user-interface devices on the handlebars. Continue reading “An Open-Source Ebike Motor Controller” →

An ebike motor with the controller cover removed. A number of wires and connectors take up most of the space in the cavity.

Open Brain Surgery For EBikes And EScooters

November 6, 2023 by Navarre Bartz 7 Comments

Personal Electric Vehicles (PEVs) all contain the same basic set of parts: a motor, a battery, a motor controller, some sensors, and a display to parse the information. This simplicity allowed [casainho] to develop a custom controller setup for their own PEVs.

Built around the venerable VESC motor controller, [casainho]’s addition is the EBike/EScooter board that interfaces the existing motor of a device to the controller. Their ESP32-powered CircuitPython solution takes the sensor output of a given bike or scooter (throttle, cadence, or torque) and translates it into the inputs the controller uses to set the motor power.

They’ve also designed an ESP32-based display to interface the rest of the system to the user while riding. Since it also runs CircuitPython, it’s easy to reconfigure the functions of the three button device to display whatever you’d like as well as change various drive modes of your system. I know I’d love to see my own ebikes have a different mode for riding on road versus on shared paths since not getting run over by cars and not harassing pedestrians aren’t going to have the same power profile.

If you want to find more ways to join the PEV revolution, check out this wild omni-wheeled bike or this solar car built from two separate e-bikes. If that doesn’t suit your fancy, how about an off-label use for an e-bike battery to power your laptop off grid?

Behold The Mega-Wheelie, A Huge One-Wheeled Electric Skateboard

October 29, 2023 by Donald Papp 8 Comments

DIY electric personal vehicles are a field where even hobbyists can meaningfully innovate, and that’s demonstrated by the Mega-Wheelie, a self-balancing one-wheeled skateboard constructed as an experiment in traversing off-road conditions.

[John Dingley] and [Nick Thatcher] have been building and testing self-balancing electric vehicles since 2008, with a beach being a common testing ground. They suspected that a larger wheel was the key to working better on rough ground and dry sand and tested this idea by creating a skateboard with a single wheel. A very big, very wide wheel, in fact.

The Mega-Wheelie houses a 24V LiFePO4 battery pack, 450 W gearmotor with chain and sprocket drive, SyRen motor controller from Dimension Engineering, Arduino microcontroller, and an inertial measurement unit to enable the self-balancing function. Steering is done by leaning, and the handheld controller is just a dead man’s switch that disables the vehicle if the person piloting it lets go.

Design-wise, a device like this has a few challenging constraints. A big wheel is essential for performance but takes up space that could otherwise be used for things like batteries. Also, the platform upon which the pilot stands needs to be as low to the ground as possible for maximum stability. Otherwise, it’s too easy to fall sideways. On the other hand, one must balance this against the need for sufficient ground clearance.

Beaches are rarely covered in perfectly smooth and firm sand, making them a good test area.

In the end, how well did it work? Well enough to warrant a future version, says [John]. We can’t wait to see what that looks like, considering their past 3000 W unicycle’s only limitation was “personal courage” and featured a slick mechanism that shifted the pilot’s weight subtly to aid steering. A video of the Mega-Wheelie (and a more recent unicycle design) is embedded just below the page break.

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