The Pros And Cons Of Hydrofoils

Hydrofoils have fascinated naval architects and marine designers for years. Fitted with underwater wings, these designs traverse the waters at great speed with a minimum of drag. As with many innovative technologies, though, the use of hydrofoils is riddled with challenges that often offset the vast benefits they offer.

While hydrofoils promise a better marine transportation experience, their adoption hasn’t been smooth sailing. In this article, we’ll dive deep into the potential and pitfalls of hydrofoil designs, and look at the unique niches this technology serves today.

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Why Walking Tanks Never Became A Thing

The walking tank concept has always captured imaginations. Whether you’re talking about the AT-AT walkers of Star Wars, or the Dreadnoughts from Warhammer 40,000, they are often portrayed in fiction as mighty and capable foes on the battlefield. These legged behemoths ideally combine the firepower and defense of traditional tanks with the versatility of a legged walking frame.

Despite their futuristic allure, walking tanks never found a practical military application. Let’s take a look at why tracks still rule, and why walking combat machines are going to remain firmly in the realm of fiction for the foreseeable future.

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Books You Should Read: David Macaulay’s Architecture Series

For a lot of us, there’s a bright line separating the books we enjoyed as children from the “real” books of our more mature years. We all eventually age out of the thin, brightly illustrated picture books we enjoyed in our youth, replacing them with thicker, wordier volumes with fewer and fewer illustrations, until they become so dense with information that footnotes and appendices are needed to convey all the information, and a well-written index is a vital necessity to make use of any of it.

Such books seem like a lot less fun than kids’ books, and they probably are, but most of us adjust to the change and accept the fact that the children’s section of the library doesn’t hold much that’ll interest us anymore. But not all the books that get a “JUV” label on their spines are created equal. Some are far more than picture books, even if the pictures are the main attraction. The books of British-born American author David Macaulay come to mind, particularly the books comprising his Architecture Series.

Macaulay’s books were enormously influential in developing my engineering sensibilities, and are still a pleasure to thumb through these many years later. I still learn something about the history of construction and engineering when I pull one of these books off the shelf, which makes them Books You Should Read.

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Rocker Bogie Suspension: The Beloved Solution To Extra-Planetary Rovers

When navigating the vast and unpredictable expanses of outer space, particularly on the alien terrains of distant planets, smart engineering often underlies every major achievement. A paramount example of this is the rocker bogie suspension system. It’s an integral component of NASA’s Mars rovers and has become an iconic feature in its own right. Its success has seen the design adopted by the Indian space program and thousands of hobbyists in turn.

So, what exactly is it that makes rocker bogie suspension such a compelling design solution? Let’s dive into the engineering that makes these six-wheeled wonders so special.

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Converting Wind To Electricity Or: The Doubly-Fed Induction Generator

Humanity has been harvesting energy from the wind for centuries. The practice goes back at least to 8th century Persia where the first known historical records of windmills came, but likely extends even further back than that. Compared to the vast history of using wind energy directly to do things like mill grain, pump water, saw wood, or produce fabrics, the production of electricity is still relatively new. Despite that, there are some intriguing ways of using wind to produce electricity. Due to the unpredictable nature of wind from moment to moment, using it to turn a large grid-tied generator is not as straightforward as it might seem. Let’s take a look at four types of wind turbine configurations and how each deal with sudden changes in wind speeds. Continue reading “Converting Wind To Electricity Or: The Doubly-Fed Induction Generator”

Clipper Windpower: Solutions In Search Of Problems

The first modern wind turbines designed for bulk electricity generation came online gradually throughout the 80s and early 90s. By today’s standards these turbines are barely recognizable. They were small, had low power ratings often in the range of tens to hundreds of kilowatts, and had tiny blades that had to rotate extremely quickly.

When comparing one of these tiny machines next to a modern turbine with a power rating of 10 or more megawatts with blades with lengths on the order of a hundred meters, one might wonder if there is anything in common at all. In fact, plenty of turbines across the decades share fundamental similarities including a three-blade design, a fairly simple gearbox, and a single electric generator. While more modern turbines are increasingly using direct-drive systems that eliminate the need for a gearbox and the maintenance associated with them, in the early 2000s an American wind turbine manufacturer named Clipper Windpower went in the opposite direction, manufacturing wind turbines with an elaborate, expensive, and heavy gearbox that supported four generators in each turbine. This ended up sealing the company’s fate only a few years after the turbines were delivered to wind farms.

Some history: the largest terrestrial wind turbines were approaching the neighborhood of 2 megawatts, but some manufacturers were getting to these milestones essentially by slapping on larger blades and generators to existing designs rather than re-designing their turbines from the ground up to host these larger components. This was leading to diminishing returns, as well as an increased amount of mechanical issues in the turbines themselves, and it was only a matter of time before the existing designs wouldn’t support this trend further. Besides increased weight and other mechanical stresses on the structure itself, another major concern was finding (and paying for) cranes with enough capacity to hoist these larger components to ever-increasing heights, especially in the remote locations that wind farms are typically located. And cranes aren’t needed just for construction; they are also used whenever a large component like a generator or blade needs to be repaired or replaced. Continue reading “Clipper Windpower: Solutions In Search Of Problems”

PCIe For Hackers: An M.2 Card Journey

I’ve designed a few M.2 adapters for my own and my friends’ use, and having found those designs online, people have asked me for custom-made adapters. One of these requests is quite specific – an adapter that adds one more PCIe link to an E-key M.2 slot, the kind of slot you will see used in laptops for WiFi cards.

See, the M.2 specification allows two separate PCIe links connected to the E-key slot; however, no WiFi cards use this apart from some really old WiGig-capable ones, and manufacturers have long given up on connecting a second link. Nevertheless, there are some cards like the Google Coral M.2 E-key dual AI accelerator and the recently announced uSDR, that do indeed require the second link – otherwise, only half of their capacity is available.

It’s not clear why both Google and WaveletSDR designed for a dual-link E-key socket, since those are a rare occurrence; for the Google card, there are plenty of people complaining that the board they bought just doesn’t fully work. In theory, all you need to do to help such a situation, is getting a second PCIe link from somewhere, then wiring it up to the socket – and a perfect way to do it is to get a PCIe switch chip. You will lose out on some bandwidth because the uplink PCIe connection of the switch can only go so fast; for things like this AI accelerator, it’s not much of a problem since the main point is to get the second device accessible. For the aforementioned SDR, it might turn out useless, or you might win some but lose some – can’t know until you try! Continue reading “PCIe For Hackers: An M.2 Card Journey”