How Powerful Should An Electric Bike Be? The UK Is Asking

March 6, 2024 by Jenny List 119 Comments

As electric drives sweep their way to dominance in the automotive world, there’s another transport sector in which their is also continuing apace. Electric-assisted bicycles preserve the feeling of riding a bike as you always have, along with an electric motor to effortlessly power the rider over hill and dale. European electric two-wheelers are limited to a legal top speed of about 15 miles per hour and a 250 watt motor, but in a post-Brexit dash for independence the British government are asking whether that power should be increased to 500 watts.

The Westminster politicians think such a move will make electric bikes more attractive to consumers, and along with a move to motorcycle-style throttles rather than pedal-to-go throttles they want it to accelerate the take-up of greener transport in a country with plenty of hills. Meanwhile cycling groups and safety groups are concerned, the former whether the move is needed at all, and the latter over the fire risk from more powerful battery packs.

The Hackaday electric bike stable gives us a bit of experience on the matter, and our take is that with a 15 mile-per-hour limit there’s little point in upping the motor power. There’s a 350 watt European limit for three-wheelers though, which we could see would really benefit from a raise if applied to cargo bikes. We can however see that a readily-available supply of cheap 500 W motors would be worth having.

Retrotechtacular: The Free Piston Engine

March 4, 2024 by Jenny List 20 Comments

We all know how a conventional internal combustion engine works, with a piston and a crankshaft. But that’s by no means the only way to make an engine, and one of the slightly more unusual alternatives comes to us courtesy of a vintage Shell Film Unit film, The Free Piston Engine, which we’ve placed below the break. It’s a beautiful period piece of mid-century animation and jazz, but it’s also an introduction to these fascinating machines.

We’re introduced to the traditional two-stroke diesel engine as thermally efficient but not smooth-running, and then the gas turbine as smooth but much more inefficient. The free piston engine, a design with opposed pistons working against compressed air springs and combining both compression and firing strokes in a single axis, doesn’t turn anything in itself, but instead works as a continuous supplier of high pressure combustion gasses. The clever part of this arrangement is that these gasses can then turn the power turbine from a gas turbine engine, achieving a smooth engine without compromising efficiency.

This sounds like a promising design for an engine, and we’re introduced to a rosy picture of railway locomotives, ships, factories, and power stations all driven by free piston engines. Why then, here in 2024 do we not see them everywhere? A quick Google search reveals an inordinately high number of scientific review papers about them but not so many real-world examples. In that they’re not alone, for alternative engine designs are one of those technologies for which if we had a dollar for every one we’d seen that didn’t make it, as the saying goes, we’d be rich.

It seems that the problem with these engines is that they don’t offer the control over their timing that we’re used to from more conventional designs, and thus the speed of their operation also can’t be controlled. The British firm Libertine claim to have solved this with their line of linear electrical generators, but perhaps understandably for commercial reasons they are a little coy about the details. Their focus is on free piston engines as power sources for hybrid electric vehicles, something which due to their small size they seem ideally suited for.

Perhaps the free piston engine has faced its biggest problem not in the matter of technology but in inertia. There’s an old saying in the computer industry: “Nobody ever got fired for buying IBM“, meaning that the conventional conservative choice always wins, and it’s fair to guess that the same applies anywhere a large engine has been needed. A conventional diesel engine may be a complex device with many moving parts, but it’s a well-understood machine that whoever wields the cheque book feels comfortable with. That’s a huge obstacle for any new technology to climb. Meanwhile though it offers obvious benefits in terms of efficiency, at the moment its time could have come due to environmental concerns, any internal combustion engine has fallen out of fashion. It’s possible that it could find a life as an engine running on an alternative fuel such as hydrogen or ammonia, but we’re not so sure. If new free piston engines do take off though, we’ll be more pleased than anyone to eat our words.

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Car Driving Simulators For Students, Or: When Simulators Make Sense

February 21, 2024 by Maya Posch 69 Comments

There are many benefits to learning to fly an airplane, drive a racing car, or operate some complex piece of machinery. Ideally, you’d do so in a perfectly safe environment, even when the instructor decides to flip on a number of disaster options and you find your method of transportation careening towards the ground, or the refinery column you’re monitoring indicating that it’s mere seconds away from going critical and wiping out itself and half the refinery with it.

Still, we send inexperienced drivers in cars onto the roads each day as they either work towards getting their driving license, or have passed their driving exam and are working towards gaining experience. It is this inexperience with dangerous situations and tendency to underestimate them which is among the primary factors why new teenage drivers are much more likely to end up in crashes, with the 16-19 age group having a fatal crash nearly three times as high as drivers aged 20 and up.

After an initial surge in car driving simulators being used for students during the 1950s and 1960s, it now appears that we might see them return in a modern format.

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3D Print Train Wheels For Garden Railway

February 18, 2024 by Jenny List 15 Comments

There’s something magical about a train, whether you call it a railway or a railroad, plenty of us have hankered after our own little piece of line on which to shunt wagons or chuff around our domain. Envy [Otis Rowell] then, because he’s made himself a garden railway with the laudable purpose of moving wood pellets for his heating. A mere garden railway may be cool but it’s not in itself special, so the reason we’re featuring it here comes from something else. He’s making his rail wheels by 3D printing them with a normal printer.

It’s important to understand that these wheels are not for a high-speed mainline express freight train but for a small flat car designed to carry a modest tub of pellets, thus they are less in need of high strength than their full-size cousins. But even a small car on garden railway-sized aluminum rails can exert significant force, so we would be fascinated to see how well these do. The write-up is a work in progress as this article is being written so we know there’s more to come, but there’s no harm in speculating as to how a better 3D-printed wheel might be made. We would be particularly curious for example as to whether a novel slicing regime could be used to make a stronger wheel.

If backyard railways interest you, it’s not the first time we’ve seen one.

AI-Powered Bumper Sticker Provides Context-Sensitive Urban Camouflage

February 14, 2024 by Dan Maloney 17 Comments

While we absolutely support the right of everyone to express their opinions, it seems to us that it’s rarely wise to turn your vehicle into a mobile billboard for your positions. Aside from potentially messing up the finish on your car, what’s popular and acceptable at home might attract unwanted attention while traveling abroad, leading to confrontations that might make your trip a little more eventful than it needs to be.

So why not let technology help you speak your mind in a locally sensitive manner? That’s the idea behind [Pegor]’s “smahtSticker”, an AI-powered bumper sticker that provides the ultimate in context-sensitive urban camouflage. The business end of smahtSticker — we’re going to go out on a limb here and predict that [Pegor] hails from the Boston area — is an 8.8″ (22-cm) wide HDMI display capable of 1920×480 resolution. That goes on the back of your car and is driven by a Raspberry Pi Zero with a GPS module. The Pi grabs a geolocation every second, and if you’ve moved more than 25 feet (7.6 m) — political divisions are at least that granular in the US right now, trust us — it grabs your current ZIP code using GeoPy. That initiates a query to the OpenAI API to determine the current political attitudes in your location, which is used to select the right slogan to display. You’ll fit in no matter where you wander — wicked smaht!

Now, of course, this is all in good fun, and with tongue planted firmly in cheek. The display isn’t weatherized at all, so that would need to be addressed if one felt like fielding this. Also, ZIP codes may be good for a lot of things, but it’s not the best proxy for political alignment, so you might want to touch that part up.

Bringing Modern Technology To A Sled

February 12, 2024 by Bryan Cockfield 17 Comments

Street sledding, a popular pastime in Norway, is an activity that is slowly dwindling in popularity, at least as far as [Justin] aka [Garage Avenger] has noticed. It used to be a fun way of getting around frozen lakes and roads during winter, and while some still have their sleds [Justin] wanted to see if there was a way to revitalize one of these sleds for the modern era. He’s equipped this one with powerful electric turbines than can quickly push the sled and a few passengers around the ice.

Since this particular sled is sized for child-sized passengers, fuel-burning jet engines have been omitted and replaced with electric motors that can spin their turbine blades at an impressive 80,000 rpm. The antique sled first needed to be refurbished, including removing the rust from the runners and reconditioning the wood. With a sturdy base ready to go, the sled gets a set of 3D printed cowlings for the turbines, a thumb throttle on the upgraded handlebars, and a big battery with an Arduino to bring it all together.

With everything assembled and a sheet of ice to try it out on, the powerful sled easily gets its passengers up to the 20-30 kph range depending on passenger weight and size. There’s a brake built on an old ice skate for emergency stops, and the sled was a huge hit for everyone at the skating pond. There are plenty of other ways to spruce up old sleds, too, like this one which adds a suspension for rocketing down unplowed roads.

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How Airplanes Mostly Stopped Flying Into Terrain And Other Safety Improvements

February 8, 2024 by Maya Posch 13 Comments

We have all heard the statistics on how safe air travel is, with more people dying and getting injured on their way to and from the airport than while traveling by airplane. Things weren’t always this way, of course. Throughout the early days of commercial air travel and well into the 1980s there were many crashes that served as harsh lessons on basic air safety. The most tragic ones are probably those with a human cause, whether it was due to improper maintenance or pilot error, as we generally assume that we have a human element in the chain of events explicitly to prevent tragedies like these.

Among the worst pilot errors we find the phenomenon of controlled flight into terrain (CFIT), which usually sees the pilot losing track of his bearings due to a variety of reasons before a usually high-speed and fatal crash. When it comes to keeping airplanes off the ground until they’re at their destination, here ground proximity warning systems (GPWS) and successors have added a layer of safety, along with stall warnings and other automatic warning signals provided by the avionics.

With the recent passing of C. Donald Bateman – who has been credited with designing the GPWS – it seems like a good time to appreciate the technology that makes flying into the relatively safe experience that it is today.

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