Building A Chain Drive Differential From Junkyard Parts

December 15, 2022 by Lewin Day 26 Comments

A differential is a very useful thing for a vehicle. It allows two driven wheels to rotate at different speeds, such as when going around a corner. [Workshop From Scratch] needed a chain driven differential, so set about building one from a salvaged automotive unit.

The differential itself was taken from a BMW E46 3-Series, specifically a 2.0-liter diesel model. The work began by removing the differential’s center gears from its big, hefty iron housing. Disassembly then ensued, with the spider gears removed from their carrier and the other components discarded. The differential gears themselves were installed instead in a new compact housing, fabricated with much welding and lathery. The housing was fitted with a large chain sprocket to deliver drive, in place of the original differential’s ring gear and pinion.

The video’s description states it would be an ideal differential for a go-kart, buggy, or other such small vehicle. Given the differential gears were originally built to handle a full-sized car, they should be more than capable of dealing with such applications.

If you’re a little unfamiliar with how differentials work, check out this primer from the early 20th century. It’s widely considered to be the best education on the topic. Video after the break.

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Build A Better Mousetrap… But It Better Be Better!

December 8, 2022 by Al Williams 22 Comments

As creative problem solvers, we like to “think outside the box,” and we should strive for that. But what happens if your strange idea isn’t kept in check by cooler heads? There is a real danger — especially if you work alone — to falling so in love with your idea, that you lose sight of what it really means to be better.

Case in point. The self-parking car. Well, not the modern variant, which seems to work pretty well. But did you know that the self-parking car was invented in the 1930s and used an extra fifth wheel? Hard to imagine? See the video below. History tells us that the idea didn’t catch on.

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Converting A Porsche 944 To Run A MAF

December 2, 2022 by Lewin Day 28 Comments

Electronic fuel injection was a big leap forward for engine control. However, early implementations often left something to be desired. This was the case for [Rob] and his Porsche 944, which had relied on an old-fashioned mechanical air flow meter (AFM). He decided to replace this with a modern mass air flow (MAF) sensor instead, and documented the process online.

The output of the sensors was compared with a rig built using a vacuum cleaner to create air flow.

AFMs are often a target for replacement on old cars. They’re usually based on a flap that moves a potentiometer wiper across a carbon trace which wears out over the years. They can also present an air flow restriction in some cases, limiting performance. MAF sensors instead measure the amount of air flowing through with a hot wire. The amount of current required to maintain the temperature of the wire indicates the amount of air flowing through the sensor. They’re less restrictive and readily available as they’re used in many cars today.

To run a MAF in place of the AFM requires a circuit to emulate the AFM’s output. [Rob] used a STM32 Cortex-M0 to read the MAF, and then output the relevant voltage to the Porsche’s engine computer via PWM and a low pass filter. To figure out how to map the MAF’s output to match the AFM, [Rob] built a rig to blow air through both devices in series, and measuring their output on an oscilloscope. This data was used to program the STM32 to output the right emulated AFM voltage for the given MAF signal.

It’s a great piece of work from [Rob] that has his Porsche running happily on new parts. We’ve seen similar hacks done to other cars before, as well! Video after the break.

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The J1772 Hydra Helps You Charge Two EVs At Once

December 2, 2022 by Lewin Day 20 Comments

There are plenty of electric vehicle (EV) chargers out there that are underutilized. This is particularly common where older EVs are involved, where the cars may only be able to charge at a few kW despite the charger being capable of delivering more. [Nick Sayer] regularly found 6.6 kW chargers being used by vehicles that could only draw down 3.3 kW at his work. Thus, he built the J1772 Hydra as a nifty double-adapter to charge two cars at once.

The Hydra comes in two versions. One is a “splitter,” which is designed to be plugged into an existing J1772 AC charger. The other is a version designed for permanent installation to an AC power supply as an EV charger in its own right. Either way, both versions of the Hydra work the same way. In “shared” mode, the Hydra splits the available AC power equally between both cars connected to the charger. When one completes, the other gets full power. Alternatively, it can be set up in “sequential” mode, allowing one car to first charge, then the other. This is great when you have two cars to charge overnight and don’t want to wake up to shift the plugs around.

It’s a neat hack that could be useful if you’re running older EVs that rely on slower AC charging. We’ve seen other DIY EV chargers before, too. Expect hacking in these areas to become more commonplace as EVs grow in popularity.

Car Batteries: More Than Just Wet Lead

December 1, 2022 by Al Williams 47 Comments

Working on car electrical systems used to be easy. The battery simply provided power for the car’s starter motor when starting or to run the small number of accessories when the engine wasn’t running. The rest of the time, the alternator charged the battery and provided power for the rest of the vehicle and the ignition system. While very early cars didn’t have batteries, and some old cars had 6 V positive ground systems, most of us have lived our entire lives where car batteries come in several sizes (controlled by Battery Council International) and cars have a 12 V, negative ground system.

Times have changed. Cars don’t have distributors anymore, they have computers. They also have lots of gadgets from GPS to backup cameras and cellphone chargers. Batteries have had to get beefier and the modern trend is to also require less maintenance So, today, you’ll find that there isn’t just one kind of car battery. But how do these other batteries work and what was wrong with the good old lead acid wet cell?

For the purposes of this post, I’m not talking about electric car batteries which is a whole different topic — and most of them have a regular car battery, too. Continue reading “Car Batteries: More Than Just Wet Lead” →

EV Chargers Could Be A Serious Target For Hackers

November 28, 2022 by Lewin Day 56 Comments

Computers! They’re in everything these days. Everything from thermostats to fridges and even window blinds are now on the Internet, and that makes them all ripe for hacking.

Electric vehicle chargers are becoming a part of regular life. They too are connected devices, and thus pose a security risk if not designed and maintained properly. As with so many other devices on the Internet of Things, the truth is anything but.

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Spoofing LIDAR Could Blind Autonomous Vehicles To Obstacles

November 22, 2022 by Lewin Day 74 Comments

Humans manage to drive in an acceptable fashion using just two eyes and two ears to sense the world around them. Autonomous vehicles are kitted out with sensor packages altogether more complex. They typically rely on radar, lidar, ultrasonic sensors, or cameras all working in concert to detect the road conditions ahead.

While humans are pretty wily and difficult to fool, our robot driving friends are less robust. Some researchers are concerned that LiDAR sensors could be spoofed, hiding obstacles and tricking driverless cars into crashes, or worse.

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