A Peek Inside A 747 Fuel Gauge

June 11, 2023 by Matthew Carlson 28 Comments

It isn’t that often that we civilians get the chance to closely examine the fantastic internals that make up the modern marvels of avionic engineering. Luckily for us, [Glen] got his hands on a 747 fuel gauge and tore it down for our benefit. Not only does he tear it down, but he also builds a controller to display values.

Unlike your typical automotive fuel gauge that reports the distance from the top of the tank to the fuel level, this gauge reports the number of pounds of fuel. The fact that the indicator pictured above can go all the way to 95,000 pounds of fuel hits home the sheer scale of the fuel tanks on a 747 compared to your Volvo. Of course, where this gets interesting is the teardown with the metal sleeve removed. A 400 HZ AC servo motor moves the pointer and counter through the gearing with the help of a feedback potentiometer. The resistance tolerance is only 3%, as there are adjustment knobs on the back. But the linearity spec is only 0.06%, putting this part in a different grade from most pots.

One of the indicators was in worse shape than the others, so [Glen] got to work tapping into the internals of the gauge to drive the motor directly. A custom AC power supply repurposed from another project provided power, and a Raspberry Pi Pico was the PID controller. For [Glen], it isn’t all roses. Unfortunately, a noisy spot around 22,500 prevents accurate placement around there.

The code is up on GitHub, and we love having a gauge on the desk to show whatever value we like. If you are curious about more 747 instruments, this retro control unit might interest you.

Continue reading “A Peek Inside A 747 Fuel Gauge” →

The Yamato 1, a sleek grey ship that looks vaguely like a computer mouse or Star Trek shuttlecraft. It has an enclosed cockpit up front with black windows and blue trim. It is sitting on land in front of a red tower at a museum in Tokyo.

Navy Program PUMPs Up Hopes For Magnetic Propulsion

June 5, 2023 by Navarre Bartz 43 Comments

The “caterpillar drive” in The Hunt for Red October allowed the sub to travel virtually undetected through the ocean, but real examples of magnetohydrodynamic drives (MHDs) are rare. The US Navy’s recently announced Principles of Undersea Magnetohydrodynamic Pumps (PUMP) intends to jump-start the technology for a new era.

Dating back to the 1960s, research on MHDs has been stymied by lower efficiencies when compared with driving a propeller from the same power source. In 1992 the Japanese Yamato-1 prototype, pictured at the top of the page, was able to hit a blistering 6.6 knots (that’s 12 kph or 7.4 mph for you landlubbers) with a 4 Tesla liquid helium-cooled MHD. Recent advances courtesy of fusion research have resulted in magnets capable of generating fields up to 20 Telsa, which should provide a considerable performance boost.

The new PUMP program will endeavor to find solutions for more robust electrode materials that can survive the high currents, magnetic fields, and seawater in a marine environment. If successful, ships using the technology would be both sneakier and more environmentally friendly. While you just missed the Proposers Day, there is more information about getting involved in the project here.

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.

Continue reading “Victorian Train Tunnel Turned Test Track” →

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.

Continue reading “Bike Rides Played Back Via Aircraft Altitude Indicator” →

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.

Continue reading “Bike Camper With Retro Flair” →