Victorian Train Tunnel Turned Test Track

June 4, 2023 by Danie Conradie 28 Comments

Characterizing the aerodynamic performance of a vehicle usually requires a wind tunnel since it’s difficult to control all variables when actually driving. Unless you had some kind of perfectly straight, environmentally controlled, and precision-graded section of road, anyway. Turns out the Catesby Tunnel in the UK meets those requirements exactly, and [Tom Scott] recently got to take a tour of it.

The 2.7 kilometer (1.7 mile) long tunnel was constructed as a railway tunnel between 1895 and 1897, thanks to the estate owner objecting to the idea of “unsightly trains” crossing his property. The tunnel’s construction was precise even by modern standards, deviating only 3 mm from being perfectly straight along its entire length. It lay abandoned for many years until it was paved and converted into a test facility, opening in 2021.

To measure the speed without the luxury of GPS reception, a high-speed camera mounted inside a vehicle detects reflective tags mounted every 5 m along the tunnel’s wall. This provides accurate speed measurement down to 0.001 km/h. A pair of turntables are installed at the ends of the tunnel to avoid an Austin Powers multi-point turn (apparently that’s the technical term) when turning around inside the confined space.

Due to the overhead soil and sealed ends, the temperature in the tunnel only varies by 1 – 2 °C year round. This controlled environment makes the tunnel perfect for coastdown tests, where a vehicle accelerates to a designated speed and then is put into neutral and allowed to coast. By measuring the loss of speed across multiple runs, it’s possible to calculate the aerodynamic drag and friction on the wheels. Thanks to the repeatable nature of the tests, it was even possible to calculate the aerodynamic losses caused by [Tom]’s cameras mounted to the outside of the vehicle.

The Catesby Tunnel is an excellent example of repurposing old infrastructure for modern use. Some other examples we’ve seen include using coal mines and gold mines for geothermal energy.

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Bike Rides Played Back Via Aircraft Altitude Indicator

June 3, 2023 by Lewin Day 7 Comments

Any good bike ride should have a big climb to push your fitness, and a nice descent for the joy of careening down at high speed. [Glen Akins] has been recording his altitude during his mountain biking expeditions, and has now built a way to play them back on an aircraft altitude indicator.

A Python script is used to parse a recorded GPX file, which stores position and elevation data captured from a GPS device during [Glen]’s rides. The elevation data is then output to a Raspberry Pi Pico, which drives a set of three Microchip MCP4802 DACs and three TI OPA584 op-amps in order to create the necessary 400 Hz AC waveforms to drive the aircraft altitude indicator. One DAC and op-amp are used to generate 400 Hz AC to simply power the device, while the other two are used to generate synchro signals to actually drive the dial as needed. The maths involved is worth checking out, particularly if you’re into old-school instrumentation from the 20th century.

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Will Electric Tractors Farm Your Food?

May 30, 2023 by Jenny List 119 Comments

There are two professions used to driving single-seaters with hundreds of horsepower, one of which is very exclusive and the other of which can be found anywhere the ground is fertile enough to support agriculture. Formula One drivers operate fragile machines pushed to the edges of their performance envelope, while the tractor at the hands of a farmer is designed to reliably perform huge tasks on dodgy ground in all weathers. Today’s tractor is invariably a large machine powered by a diesel engine, and it’s the equal of all tasks on a modern farm. Against that backdrop then it’s interesting to read the Smithsonian magazine’s look at the emerging world of electric tractors. Will they replace diesel as the source of traction in the fields?

The two firms they focus on first are Monarch Tractor, and Solectrac. Both manufacturers offer small machines of the type we’d be inclined to describe as an orchard tractor, and Monarch are offering an autonomous option as part of their package. They also feature Farm-ng, whose machine called amusingly the Amiga, is a much smaller affair which we are guessing would be super-useful on a very intensive operation such as market gardening. We’re especially pleased to see that the emerging small electric tractor industry is embracing right to repair, something the traditional manufacturers are famous for ignoring.

It’s obvious that none of these machines are going to revolutionize the world of large high-power tractors any time soon, as they are too small for the job and can’t offer the 24/7 operation required at busy times on a farm. But it’s obvious they would be very useful on a small farm, and in particular for those tractor applications where the machine is a platform which goes from place to place to aid static work, they could be better than their diesel equivalents.

It’s odd that over the years we’ve not covered any electric tractors before. Perhaps that is, until you search instead for agricultural robots.

Adding Variometer Functionality To A GPS

May 25, 2023 by Bryan Cockfield 10 Comments

Flying a glider, or similarly piloting a paraglider or hang glider, can all be pathways into aviation with a lower barrier of entry than powered flight. Sacrificing one’s engine does generate a few complexities, but can be rewarding as the pilot searches for various means of increasing altitude like ridge soaring or thermaling. You’ll need a special instrument called a variometer to know just how much altitude you’re gaining though, like this one which is built into commercially-available handheld GPS units.

These GPS units are normally intended for use on terra firma only, but [Oganisyan] has figured out a clever way to add this flight instrumentation to these units to help when operating a paraglider. An ATmega328 paired with a pressure sensor is added to the inside of the GPS units and communicates with an available serial interface within the units. To complete the modification, a patched firmware must be installed which adds the variometer function to the display. This upgrade is compatible with a handful of GPS units as well such as the BikePilot2+ or Falk Tiger.

For those who already own one of these GPS units, this could be a cost-effective way of obtaining a variometer, especially since commercially-available variometers tailored for this sort of application can cost around $200 to $500. It is an activity sensitive to cost, though, as it offers a much more affordable option for taking to the skies than any powered craft could, with an exception made for this powered paraglider which offers the ability for powered take off and flight extension using electric-powered props.

Thanks to [MartinO] for the tip!

A blue work tricycle (single front wheel with platform between two rear wheels) sits on an asphalt path with trees and wildflowers in the background. A boxy, white camper with a front overhanging the bike seat is attached to the platform. It has a yellow stripe and curtains like many campers did in the 1970s. One white male is exiting the door of the camper while his brother is standing to the left of the camper by the bike seat.

Bike Camper With Retro Flair

May 23, 2023 by Navarre Bartz 33 Comments

As we’re approaching summer here in the Northern Hemisphere, thoughts naturally turn toward road trips. While most people do this in their car, the [Dangie Bros] built a 500 lb bike camper for their own take on the great American Road Trip.

Taking a maximalist approach not seen in most bike campers, this behemoth has a working sink, propane stove, seating area, and an upstairs sleeping area. A small window in the front of the camper opens to let the passenger inside converse with the person pedaling, and a solar panel charges a small battery for lights and a roof fan.

While the camper is very ’70s retro-chic, its lack of assist (other than the passenger getting out to push) meant that on the second day of their road trip they resorted to towing the camper behind a second bike in a pseudo-tandem arrangement. The fold out bed takes some design cues from RVs, but clearly needed more reinforcement since it collapsed partway through the night. With an e-assist and some refinements, this could be comfortable (albeit slow) way to go bike glamping.

If you’d like to try your own hand at a bike camper but do it more aerodynamically and attached to an assisted bike, checkout this teardrop trailer or this bike camper.

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Hoverboard Rides On Eddy Currents

May 22, 2023 by Bryan Cockfield 32 Comments

The famous hoverboards of Back to the Future haven’t quite gotten here yet, but that hasn’t stopped anyone with a unique personal vehicle from using the name any time they need some quick marketing. The self-balancing scooter trend of the mid-2010s was the best example of this in recent memory, but there are also water-propelled platforms that use the popular name as well as a myriad of other more skateboard-like devices that never got off the ground at all. This project from [Damien Dolata], on the other hand, might be the most authentic prototype we’ve seen compared against the fictional version presented in the movie.

The hoverboard uses a set of rotating magnets, referred to in this build as magneto-rotational repulsors, which spin up to an extremely high rotational speed underneath the board. When above a metal surface, the spinning magnets generate eddy currents in the metal beneath them which create the strong magnetic field needed to levitate the board. Unlike the Lexus hoverboard system which used supercooling magnets, this is a much more affordable way of producing magnetic fields but is a little bit more complicated due to the extra moving parts.

As this is still in the prototyping stages, it has only been able to lift around 30 kg and hasn’t been tested in motion yet, but there are two small turbines built into the hoverboard to generate thrust whenever [Damien] gets to that point. It would require a larger metal surface to move across as well, which might be the main reason why it hasn’t been tested this way yet. For any native French speakers taking a look at this project, be sure to fill in any of our gaps in the comments below, and for other ways that eddy currents have been used in transportation take a look at this bicycle that uses them in its drivetrain.

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Self-Driving Library For Python

May 16, 2023 by Bryan Cockfield 3 Comments

Fully autonomous vehicles seem to perennially be just a few years away, sort of like the automotive equivalent of fusion power. But just because robotic vehicles haven’t made much progress on our roadways doesn’t mean we can’t play with the technology at the hobbyist level. You can embark on your own experimentation right now with this open source self-driving Python library.

Granted, this is a library built for much smaller vehicles, but it’s still quite full-featured. Known as Donkey Car, it’s mostly intended for what would otherwise be remote-controlled cars or robotics platforms. The library is built to be as minimalist as possible with modularity as a design principle, and includes the ability to self-drive with computer vision using machine-learning algorithms. It is capable of logging sensor data and interfacing with various controllers as well, either physical devices or through something like a browser.

To build a complete platform costs around $250 in parts, but most things needed for a Donkey Car compatible build are easily sourced and it won’t be too long before your own RC vehicle has more “full self-driving” capabilities than a Tesla, and potentially less risk of having a major security vulnerability as well.