Electric scooters have long been a hacker’s friend, Xiaomi ones in particular – starting with M365, the Xiaomi scooter family has expanded a fair bit. They do have a weak spot, like many other devices – the battery, something you expect to wear out.

Let’s say, one day the scooter’s diagnostics app shows one section of the battery going way below 3 volts. Was it a sudden failure of one of the cells that brought the whole stage down? Or perhaps, water damage after a hastily assembled scooter? Now, what if you measure the stages with a multimeter and it turns out they are perfectly fine?

Turns out, it might just be a single capacitor’s fault. In a YouTube video, [darieee] tells us all about debugging a Xiaomi M365 battery with such a fault – a BQ76930 controller being responsible for measuring battery voltages. The BMS (Battery Management System) board has capacitors in parallel with the cells, and it appears that some of these capacitors can go faulty.

Are you experiencing this particular fault? It’s easy to check – measure the battery stages and see if the information checks out with the readings in your scooter monitoring app of choice. Could this be a mechanical failure mode for this poor MLCC? Or maybe, a bad batch of capacitors? One thing is clear, this case is worth learning from, adding this kind of failure to your collection of fun LiIon pack tidbits. This pack seems pretty hacker-friendly – other packs lock up when anything is amiss, like the Ryobi batteries do, overdue for someone to really spill their secrets!

[Ken] recently obtained an attitude indicator—sometimes called an artificial horizon—from an F-4 fighter jet. Unlike some indicators, the F-4’s can rotate to show pitch, roll, and yaw, so it moves in three different directions. [Ken] wondered how that could work, so, like any of us, he took it apart to find out.

With the cover off, the device is a marvel of compact design. Then you realize that some of the circuit is inside the ball, so there’s even more than it appears at a quick glance. As you might have guessed, there are two separate slip rings that allow the ball to turn freely without tangling wires. Of course, even if you don’t tangle wires, getting the ball to reflect the aircraft’s orientation is an exercise in control theory, and [Ken] shows us the servo loop that makes it happen. There’s a gyroscope and synchros—sometimes known by the trade name selsyn—to keep everything in the same position.

You have to be amazed by the designers of things like this. Sophisticated both electrically and mechanically, rugged, compact, and able to handle a lot of stress. Good thing it didn’t have to be cheap.

We’ve seen inside an ADI before. If you want to make any of this look simple, check out the mechanical flight computers from the 1950s.

Recently, the EPA and COBB Tuning have settled after the latter was sued for providing emissions control defeating equipment. As per the EPA’s settlement details document, COBB Tuning have since 2015 provided customers with the means to disable certain emission controls in cars, in addition to selling aftermarket exhaust pipes with insufficient catalytic systems. As part of the settlement, COBB Tuning will have to destroy any remaining device, delete any such features from its custom tuning software and otherwise take measures to fully comply with the Clean Air Act, in addition to paying a $2,914,000 civil fine.

The tuning of cars has come a long way from the 1960s when tweaking the carburetor air-fuel ratios was the way to get more power. These days cars not only have multiple layers of computers and sensor systems that constantly monitor and tweak the car’s systems, they also have a myriad of emission controls, ranging from permissible air-fuel ratios to catalytic converters. It’s little surprise that these systems can significantly impact the raw performance one might extract from a car’s engine, but if the exhaust of nitrogen-oxides and other pollutants is to be kept within legal limits, simply deleting these limits is not a permissible option.

COBB Tuning proclaimed that they weren’t aware of these issues, and that they never marketed these features as ’emission controls defeating’. They were however aware of issues regarding their products, which is why they announced ‘Project Green Speed’ in 2022, which supposedly would have brought COBB into compliance. Now it would seem that the EPA did find fault despite this, and COBB was forced to making adjustments.

Although perhaps not as egregious as modifying diesel trucks to ‘roll coal’, federal law has made it abundantly clear that if you really want to have fun tweaking and tuning your car without pesky environmental laws getting in the way, you could consider switching to electric drivetrains, even if they’re mind-numbingly easy to make performant compared to internal combustion engines.

Although battery fires in electric cars and two-wheeled vehicles are not a common phenomenon, they are notoriously hard to put out, requiring special training and equipment by firefighters. Although the full scope of the issue is part of a contentious debate, [Aarian Marshall] over at Wired recently wrote an article about how the electric car industry has a plan to make a purportedly minor issue even less of an issue. Here the questions seem to be mostly about what the true statistics are for battery fires and what can be done about the primary issue with batteries: thermal runaway.

While the Wired article references a study by a car insurance company about the incidence of car fires by fuel type (gas, hybrid, electric), its cited sources are dubious as the NTSB nor NHTSA collect statistics on these fires. The NFPA does, but this only gets you up to 2018, and they note that the data gathering here is spotty. Better data is found from European sources, which makes clear that battery electric vehicles (BEVs) catch fire less often than gasoline cars at 25 per 100,000 cars sold vs 1529/100k for ICE cars, but when BEVs do burn it’s most often (60%) from thermal runaway, which can be due to factors like a short circuit in a cell, overcharging and high ambient temperatures (including from arson or after-effects of a car crash).

As for the claimed ways to make battery-powered vehicles safer, the Wired article mentions the shift to more stable lithium-ion chemistries like lithium-ion phosphate (LiFePO4, or LFP for short), experimenting with solid-state batteries and easier ways to extinguish a fire and disconnect the BEV’s battery, along with firefighter training. Meanwhile the European Union will require a ‘battery passport’ starting in 2027 which tracks the origin, manufacturing and testing of batteries.

Of the risks with batteries, thermal runaway is probably the least predictable, with a review article by [Mahn-Kien Tran] and colleagues in Processes from 2022 covering our current understanding here, including ways to model and predict the occurrence of thermal runaway to increase safety while e.g. charging a battery. As internal shorts due to wear and/or manufacturing defects can be hard to predict, it is essential to detect thermal runaway before it has a chance to get out of hand.

Beyond electric cars, electric bikes are far more notorious for catching on fire, with these devices in New York City having gained the reputation of burning down apartment buildings, generally while charging. As MIT Technology Review reports, a solution here may have been found in battery swapping stations that are equipped with sensors and fire extinguishing systems, so that delivery drivers and other e-bike users do not have to charge batteries at their apartments while praying that they don’t wake up to thick smoke and a screaming fire alarm.

As battery-powered vehicles and devices become more and more common, it’s clear that even if the risk of fire from these vehicles is small compared to their gasoline-powered brethren, those generally do not catch on fire while parked in one’s garage or hallway. Finding ways to mitigate this risk is therefore more than welcome.

One major flaw of designing societies around cars is the sheer amount of signage that drivers are expected to recognize, read, and react to. It’s a highly complex system that requires constant vigilance to a relatively boring task with high stakes, which is not something humans are particularly well adapted for. Modern GPS equipment can solve a few of these attention problems, with some able to at least show the current speed limit and perhaps an ongoing information feed of the current driving conditions., Trains, on the other hand, solved a lot of these problems long ago. [Philo] and [Tris], two train aficionados, were recently able to get an old speed indicator from a train and get it working in a similar way in their own car.

The speed indicator itself came from a train on the Red Line of the T, Boston’s subway system run by the Massachusetts Bay Transportation Authority (MBTA). Trains have a few unique ways of making sure they go the correct speed for whatever track they’re on as well as avoid colliding with other trains, and this speed indicator is part of that system. [Philo] and [Tris] found out through some reverse engineering that most of the parts were off-the-shelf components, and were able to repair a few things as well as eventually power everything up. With the help of an Arduino, an I/O expander, and some transistors to handle the 28V requirement for the speed indicator, the pair set off in their car to do some real-world testing.

This did take a few tries to get right, as there were some issues with the power supply as well as some bugs to work out in order to interface with the vehicle’s OBD-II port. They also tried to use GPS for approximating speed as well, and after a few runs around Boston they were successful in getting this speed indicator working as a speedometer for their car. It’s an impressive bit of reverse engineering as well as interfacing newer technology with old. For some other bits of train technology reproduced in the modern world you might also want to look at this recreation of a train whistle.

The number of people going on cruises keeps rising year over year, with the number passengers carried increasing from just over 3.7 million in 1990 to well over 28 million in 2023. This has meant an increasing demand for more and also much larger cruise ships, which has led to an interesting phenomenon where it has become more economical to chop up an existing cruise ship and put in an extra slice to add many meters to each deck. This makes intuitively sense, as the segment added is fairly ‘dumb’, with no engine room, control systems, but mostly more rooms and cabins.

The current top-of-the-line cruise ship experience is exemplified by the Icon class that’s being constructed for the Royal Caribbean Group. The first in this line is the Icon of the Seas, which is the largest cruise ship in the world with a length of 364.75 meters and a gross tonnage of 248,663. All of this cost €1.86 billion and over two years of construction time, compared to around $80 million and a few months in the drydock. When combined with a scheduled maintenance period in the drydock, this ‘Jumboization’ process can be considered to be a great deal that gives existing cruise ships a new lease on life.

Extending a ship in this manner is fairly routine as well, with many ships beyond cruise ships seeing the torch before being split. A newly built segment is then slid in place, the metal segments are welded together, wires, tubing and more are spliced together, before the in and outside are ready for a new coat of paint that makes it seem like nothing ever happened to the ship.

[Michelle Hampson] reports in IEEE Spectrum that Chinese researchers may improve self-driving cars by mimicking how the human eye works. In some autonomous cars, two cameras use polarizing filters to help understand details about what the car sees. However, these filters can penalize the car’s vision in low light conditions.

Humans, however, have excellent vision in low-lighting conditions. The Retinex theory (based on the Land Effect discovered by [Edwin Land]) attributes this to the fact that our eyes sense both the reflectance and the illumination of light. The new approach processes polarized light from the car’s cameras in the same way.

The images pass through two algorithms. One compensates for brightness levels, while the other processes the reflective properties of the incoming light. They mounted cameras on real cars and drove them in actual dim environments to test everything out.

The result? Studies show that the approach improved driving accuracy by approximately 10%. However, the algorithms require extensive training on difficult-to-obtain data sets, so that is one challenge to adoption.

Self-driving cars certainly need improving. Oddly enough, navigation can be done with polarizing filter cameras and a clear view of the sky. Or, you can look under the road.

You know, it feels as though it’s getting more and more difficult to compete for Father of the Year around here. And [Jon Petter Skagmo] just laid down a new gauntlet — the incredibly overly-engineered kids car.

While the original plan was to build the entire car from scratch, [Jon] eventually opted to use an off-the-shelf car that had a dead battery.

While the original architecture was quite simple, the new hardware has just about everything a kid could want in a tricked-out ride, most of which is accessible through the really cool dashboard.

We’re talking headlights, a music player, a siren, a selfie video cam that doubles as two-way communication with the driver, and even a garage door opener that uses an MQTT connection.

Under the cute little hood is where you’ll find most of the electronics. The car’s brain is a Raspberry Pi 3B, and there’s a custom daughter board that includes GPS/GNSS. This was originally meant to geofence [Baby Girl Skagmo] in, but Dad quickly realized that kids are gonna kid and disabled it pretty soon after.

This isn’t the first high-tech rebuild of a kiddie car that we’ve seen here at Hackaday. Makes us wish we were quite a bit smaller…

Monorails aren’t just the core reason why The Simpsons remains on air after thirty-six seasons, twenty-six of which are unredeemable garbage. They’re also an interesting example of oddball rail travel which has never really caught on beyond the odd gadgetbahn project here and there. [Hyperspace Pirate] recently decided to investigate the most interesting kind of monorail of all—the gyro stabilized type—on a small scale for our viewing pleasure.

The idea of a gyro-stabilized monorail is to use active stability systems to allow a train to balance on a single very thin rail. The benefits of this are questionable; one ends up with an incredibly expensive and complex rail vehicle that must always run perfectly or else it will tip over. However, it is charming to watch in action.

[Hyperspace Pirate] explains how the monorail vehicle uses control moment gyroscopes to keep itself upright. The video also explains the more common concept of reaction wheels so the two systems can be contrasted and compared. It all culminates in a wonderful practical demonstration with a small 3D printed version of a 20th-century gyro monorail running on a 24″ track.

If you’re studying mechanical engineering this is a great project to pore over to see theoretical principles put into obvious practice. Video after the break.

In a modern car, your speedometer might look analog, but it is almost certainly digital and driven by the computer that has to monitor all sorts of things anyway. But how did they work before your car was a rolling computer complex? The electronic speedometer has been around for well over a century and, when you think about it, qualifies as a technlogical marvel.

If you already know how they work, this isn’t a fair question. But if you don’t, think about this. Your dashboard has a cable running into it. The inner part of the cable spins at some rate, which is related to either the car’s transmission or a wheel sensor. How do you make a needle deflect based on the speed?

Mechanical Solutions

Early versions of the speedometer used a governor pulling against a spring. The faster it rotates, the more the two weights of the governor pull out against the spring, and the needle moves with the weights.

As an aside, this sort of centrifugal governor is also known as a fly-ball governor, and similar devices were commonly used to regulate the maximum throttle on steam engines. The arms of the governor would be fully extended once the engine reached its top speed, which lead to the term “balls-out” becoming used to describe a machine operating at its upper limits.

Another type of mechanical speedometer had an escapement like a watch. The time mechanism would move the needle back, and the rotation of the wheels would move it forward. The net result was a needle position that would increase with speed.

The Magnetic Approach

However, most cars use a magnetic type speedometer — although it doesn’t work in the way you might imagine. There’s no reed relay or Hall effect sensing the magnetic field. Instead, there is an aluminum cup attached to the speedometer needle and, nearby, a magnet that spins on a shaft moving at some ratio of the car’s speed. There’s no direct connection between the two.

Being a non-ferrous metal, aluminum is not generally something we think of being affected by magnets. Under normal circumstances that might be true, but a moving magnetic field will induce eddy currents in aluminum. This forms a field in the aluminum, too, and the spinning magnet tends to drag the cup, thereby deflecting the pointer.

A spring similar to one you might find in a mechanical clock or watch pulls back the pointer so the needle hovers at the point where the force of the magnet pulls against the spring. The pull on the spring has to account for the gear ratios and the size of the tires to accurately reflect the vehicle’s speed.

If you want to see an entertaining teardown of an old speedometer, [Tubalcain/Mr Pete] has you covered in the video below. He also shows how the odometer part worked, too.

Modern Times

Of course, these days you are more likely to pick up a pulse using a Hall effect or some other part of the vehicle and just count the pulses in the car’s computer. In fact, the pulses might be encoded at the source and travel over something like a CAN bus to get to the computer.

It is also possible to pick up speed from other tracking information like GPS, although that might not be as accurate. But if you have, for example, a mobile phone app that shows your speed, that’s probably what it is doing. The obvious way to do that is to take position measurements periodically and then do the math. However, more sophisticated systems can actually measure Doppler shift to get a more accurate reading.

We see a lot of bicycle speedometers for some reason. Eddy currents make induction cooktops work, too. Even tiny ones.

Although the designation ‘Air Force One’ is now commonly known to refer to the airplane used by the President of the United States, it wasn’t until Eisenhower that the US President would make significant use of a dedicated airplane. He would have a Lockheed VC-121A kitted out to act as his office as commander-in-chief. Called the Columbine II after the Colorado columbine flower, it served a crucial role during the Korean War and would result the coining of the ‘Air Force One’ designation following a near-disaster in 1954.

This involved a mix-up between Eastern Air Lines 8610 and Air Force 8610 (the VC-121A). After the Columbine II was replaced with a VC-121E model (Columbine III), the Columbine II was mistakenly sold to a private owner, and got pretty close to being scrapped.

Although nobody is really sure how this mistake happened, it resulted in the private owner stripping the airplane for parts to keep other Lockheed C-121s and compatible airplanes flying. Shortly before scrapping the airplane, he received a call from the Smithsonian Institution, informing him that this particular airplane was Eisenhower’s first presidential airplane and the first ever Air Force One. This led to him instead fixing up the airplane and trying to sell it off. Ultimately the CEO of the airplane maintenance company Dynamic Aviation, [Karl D. Stoltzfus] bought the partially restored airplane after it had spent another few years baking in the unrelenting sun.

Although in a sorry state at this point, [Stoltzfus] put a team led by mechanic [Brian Miklos] to work who got the airplane in a flying condition by 2016 after a year of work, so that they could fly the airplane over to Dynamic Aviation facilities for a complete restoration. At this point the ‘nuts and bolts’ restoration is mostly complete after a lot of improvisation and manufacturing of parts for the 80 year old airplane, with restoration of the Eisenhower-era interior and exterior now in progress. This should take another few years and another $12 million or so, but would result in a fully restored and flight-worthy Columbine II, exactly as it would have looked in 1953, plus a few modern-day safety upgrades.

Although [Stoltzfus] recently passed away unexpectedly before being able to see the final result, his legacy will live on in the restored airplane, which will after so many years be able to meet up again with the Columbine III, which is on display at the National Museum of the USAF.