RC Lawn Mower Cuts With Impunity

Grass is a lovely thing to have, but unfortunately it tends to grow excessively long if left unattended. Obviously, one can use a regular lawn mower, but [Daniel] of [rctestflight] decided to build something remote-control instead. (Video, embedded below.)

To get started, [Daniel] fitted X-acto blades to a brushless outrunner motor, and tested their ability to cut grass. Satisfied with the performance, he built a trailer to tow behind an RC tank mounted to such a setup, with some success. With the concept beginning to bear fruit, he went with a clean sheet design for maximum performance.

The final build relies on an RC rock-crawler chassis, fitted with a brushless motor using field oriented control for maximum torque at low speeds. This allows the RC mower to slowly push through the grass without overwhelming the cutter heads. As for the cutter heads, the final rig has eight motors, each sporting two blades to chop down long field grasses with impunity.

[Daniel] notes that it’s remarkably fun to cut the grass in this way, and is surprised not to have seen more builds in this area. (Editor’s note: he needs to read more Hackaday.) Of course, we’ve seen plenty of autonomous builds, too.

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Ode To An AVO 8 Multimeter

I’m moving, and in the process of packing all of my belongings into storage boxes to disappear into a darkened room for the next year. Perhaps I could become one of those digital nomads I hear so much about and post my Hackaday stories from a sun-kissed beach while goldfish shoals nibble at my toes. But here in a slightly damp British autumn, box after box of a lifetime’s immersion in tech needs sorting and directing. Why on earth did I hang on to three Philips N1500 VCR system video cassette recorders from the early 1970s! (Don’t worry, those have found a good home.)

Say Hello To An Old Friend Of Mine

Instantly recognisable, the AVO 8
Instantly recognisable, the AVO 8

As I was packing up my bench, I happened upon a multimeter. I have quite a few multimeters and this isn’t the first time I’ve written about these indispensable instruments, but this one’s a little special.

It’s a treasure from my youth, that most venerable of British test equipment: the AVO 8. This was the ubiquitous multimeter to be found in all manner of electrical and electronic workshops across most of the 20th century, and remains to this day one of the highest quality examples of its type.

It’s a relatively huge Bakelite box about 190mm x 170mm x 100mm in size, and it is instantly recognisable  by its dual rotary selector switches and the window for viewing the needle, which forms a characteristic circular arc kidney shape.

The earliest ancestors of my meter appeared in the 1920s, and the first model 8 in the early 1950s. Mine is a Mk III that a penciled date on the inside of its meter movement tells me was made in November 1965 and which I bought reconditioned from Stewart of Reading in about 1991, but manufacture continued until the last Mk VIII rolled off the production line in 2008. It’s to my shame that my AVO is a bit dusty and that maybe I haven’t used it much of late, but as I picked it up all the memories of using it to fix dead TV sets and set up optimistic experiments in radio came flooding back. If there’s one instrument that connects me to the youthful would-be electronic engineer that I once was, then here it is. Continue reading “Ode To An AVO 8 Multimeter”

This Week In Security: Too Little Too Late, And Other Stories

Microsoft has just announced a way to disable JScript in Internet Explorer. This would have been very useful a few years ago, to proactively prevent problems found in the now-ancient JScript engine, which ran their own slightly different version of standard JavaScript. Even though IE is no longer under active development, it still receives security updates. JScript, on the other hand, is basically done. If you’re one of the 1.06% that still use IE, then go flip the switch to protect yourself from additional JScript vulnerabilities.

Zerologon and Samba?

Samba is an open source re-implemenation of Microsoft’s SMB protocol. There’s a clever term that describes the reality of this situation: “Bug for bug compatibility”. Remember Zerologon, the flaw where a security token’s generation could be manipulated to vastly reduce the key space? Samba follows the specification, and therefore suffers from the same issue, though it seems to be unusual to actually run Samba in a vulnerable configuration.

Other implementations cannot say the same. QNAP in particular has been bitten by Zerologon when configured as a domain controller. What’s not clear is whether QNAP is running Samba on the NAS products, or if this is yet another vulnerable implementation. Either way, go update your devices. Continue reading “This Week In Security: Too Little Too Late, And Other Stories”

Learn About Historic Firearm Design With A 3D Printer

Over the last century, very little of the basic design of firearm cartridges has changed, but the mechanics of firearms themselves have undergone many upgrades. The evolution of triggers, safeties, magazines, and operating mechanisms is a fascinating field of study. Hands-on experience with these devices is rare for most people, but thanks to people like [zvc], you can 3D print accurate replicas of historical firearms and see how all the parts fit together for yourself.

[zvc] is slowly building up a library of 3D models, with nine available so far, from the Mauser C96 “Broomhandle” pistol to the modern M4 rifle. Except for springs and some fasteners, almost every single part of [zvc]’s models are 3D printed, down to the takedown pins and extractors. With the obvious exception of being able to fire a live round, it looks like all the components fit and work together like on the real firearms. None were ever designed with 3D printing in mind, so a well-tuned printer, lots of support structure, and post-processing are required to make everything work. The surface finish will be a bit rough, and some smaller and thin-walled components might be susceptible to breaking after the repeated operation or excessive force. The models are not free, but all prices are below €10.

These models do demonstrate one of the real superpowers of 3D printing: functional mock-ups and prototypes. The ability to do rapid iterative design updates and to have the latest design in hand within a few hours is invaluable in product development. [Giaco] used this extensively during the development of his kinetic driver. When you buy 3D printable models online, always make sure what possible pitfalls exist.

Peeking Inside Executables And Libraries To Make Debugging Easier

At first glance, both the executables that a compiler produces, and the libraries that are used during the building process seem like they’re not very accessible. They are these black boxes that make an application go, or make the linker happy when you hand it the ‘right’ library file. There is also a lot to be said for not digging too deeply into either, as normally things will Just Work™ without having to bother with such additional details.

The thing is that both executables and libraries contain a lot of information that normally is just used by the OS, toolchain, debuggers and similar tools. Whether these files are in Windows PE format, old-school Linux a.out or modern-day .elf, when things go south during development, sometimes one has to break out the right tools to inspect them in order to make sense of what is happening.

This article will focus primarily on the Linux platform, though most of it also applies to BSD and MacOS, and to some extent Windows.

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Old School Rotary Tools That Weren’t Made By Dremel

Albert Dremel developed the now famous rotary tool and started the company in 1932 to make blade sharpeners. It would be 1935 before the company produced the Moto-Tool which is mostly recognizable as an ancestor of the modern Dremel.

Dremel achieved such dominance that today the name is synonymous with rotary tools in the same way Xerox means photocopy and Crock-Pot is any slow cooker. Sure, there are knock offs you can get from the usual cheap tool outlets, but generally, people reach for a Dremel even when it isn’t really one. Today that tool might really be a Black and Decker or a Dewalt or even a cheap brand like Wen or Chicago Electric. But in the first half of the 20th century, you might have reached for a Handee.

A Whole Shop Full of Tools

The Handee was a product of the Chicago Wheel and Manufacturing Company who, in 1937, billed it as “a whole shop full of tools in one,” as you can see in this ad. While $10.75 might sound like a price for a Harbor Freight cheapie tool, adjusted for inflation that’s around $200 in 2020 money. At least for that price you got three free accessories out of the over 200 available.

I didn’t remember the Handee and I wanted to see if I could figure out what happened to it and the company who made it. After all, with the Internet at your disposal, how hard could it be? Turns out, I did learn a lot, but in the end, tracing down a company like this from the old days isn’t always as easy as you might think.

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Ingenious Hacks That Brought The Original Prince Of Persia To Life

For many 8-bit computing veterans, the original Prince of Persia game was our first exposure to fluid life-like animation on screen. This groundbreaking technical achievement earned the game’s place in nostalgia and history. Ars Technica invited its original creator [Jordan Mechner] to sit in front of a camera and talk through many technical and game design challenges he had to solve. (Video embedded below. Bonus: correct pronunciation of Karateka directly from the creator’s mouth.)

Enjoy the journey back in time as [Jordan] broke down the convoluted process behind Prince of Persia‘s rotoscope animation. Starting with VCR footage, to film negatives, to tracing out with black markers and white correction fluid to generate a high contrast reference suitable for the (then) state-of-the-art digitizer. But generating those frames was just the beginning! They consumed majority of an Apple II’s memory, thus fighting memory constraints was a persistent headache. Fortunately for us, that limitation also motivated memorable elements such as our “Shadow Man” alter ego.

This Prince of Persia feature is the latest episode of Ars Technica’s “War Stories” series, inviting people behind notable games to talk about their work behind the scenes. The creators of Myst put a lot of effort into minimizing the impact of CD-ROM seek times, an entirely theoretical endeavour as they had no CD burner for verification. The creators of Crash Bandicoot paged in game content from CD in 64kb chunks as a player progressed, allowing creation of levels too large to fit in a PlayStation’s memory all at once. Read over these and other short synopsis of episodes so far or go straight to their YouTube playlist.

If this talk of wrangling bits with 6502 assembly code has whet your appetite for more, the source code for Prince of Persia is available for digging into. Don’t worry if you have long since lost track of your Apple II (or never had one) as the code can run in an emulator.

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