Gyroscope Walks The Tightrope

Gyroscopes are one of those physics phenomena that are a means to many ends, but can also enjoyed as a fascinating object in their own right. Case and point being [Hyperspace Pirate]’s tightrope-balancing crawler in the video after the break.

Inside the PLA and aluminum shell is a 3D-printed wheel with steel bolts around the edge for added moment of inertia. It is powered by a low-KV¬†brushless motor with a 3:1 GT2 belt-drive and controlled by a simple servo tester, running on a 4 cell LiPo battery. The 3D-printed drive wheel is powered by a geared DC motor hooked directly to the battery. [Hyperspace Pirate] goes over the math of the design, showing that path to stability is a high speed and high moment of inertia flywheel, while staying well within the strength limits of the wheel’s material.

It’s balancing act was first demonstrated on a length of PVC conduit and then on a section of rope, with the characteristic circular wobbling of a gyroscope, known as gyroscopic precession. Without active correction, this the angle of procession will steadily increase until the machine falls over. Even so, it’s still great to watch a small scale version, like the one that inspired this build, would make a pretty cool desk toy.

Gyroscopes are commonly used in attitude indicators and and heading indicators in aircraft, and we’ve also seen them get used for balancing robots. Any ideas for practical uses for a mono-wheel rail/rope walker? Drop them in the comments below.

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Magnetic Bearings Put The Spin On This Flywheel Battery

[Tom Stanton] is right about one thing: flywheels make excellent playthings. Whether watching a spinning top that never seems to slow down, or feeling the weird forces a gyroscope exerts, spinning things are oddly satisfying. And putting a flywheel to work as a battery makes it even cooler.

Of course, using a flywheel to store energy isn’t even close to being a new concept. But the principles [Tom] demonstrates in the video below, including the advantages of magnetically levitated bearings, are pretty cool to see all in one place. The flywheel itself is just a heavy aluminum disc on a shaft, with a pair of bearings on each side made of stacks of neodymium magnets. An additional low-friction thrust bearing at the end of the shaft keeps the systems suitably constrained, and allows the flywheel to spin for twelve minutes or more.

[Tom]’s next step was to harness some of the flywheel’s angular momentum to make electricity. He built a pair of rotors carrying more magnets, with a stator of custom-wound coils sandwiched between. A full-wave bridge rectifier and a capacitor complete the circuit and allow the flywheel to power a bunch of LEDs or even a small motor. The whole thing is nicely built and looks like a fun desk toy.

This is far from [Tom]’s first flywheel rodeo; his last foray into storing mechanical energy wasn’t terribly successful, but he has succeeded in making flywheels fly, one way or another.

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Bicycle Flywheel Stores A Bit Of Energy, Not Much

Kinetic energy recovery systems have often been proposed as a useful way to improve the efficiency of on-road vehicles, and even used to great effect in motorsports for added performance. [Tom Stanton] decided to build one of his own, outfitting a simple bicycle with a flywheel system for harvesting energy. (Video, embedded below.)

The system consists of a 300 mm steel flywheel mounted in the center of the bike’s frame. It’s connected to the rear wheel via a chain and a clutch which [Tom] assembled himself using bicycle disc brake components. The clutch is controlled by a handlebar lever, allowing the rider to slow the bike by charging the flywheel, or to charge the flywheel to maximum speed by pedalling hard with the clutch engaged.

The actual utility of the flywheel is minimal; [Tom] notes that even at its peak speed of 2200 RPM, the flywheel stores a small fraction of the energy content of a AA battery. Practical demonstration shows the flywheel is only able to deliver a small push to [Tom] when riding the bike, too.

Despite the lack of performance, it’s nonetheless an interesting project and one that demonstrates the basic principles of flywheel energy storage. The underwhelming results perhaps serve as a solid indication of why it’s not something we use particularly often, on bicycles at least. We’ve seen [Tom]’s bike experiments before, too. Video after the break.

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Grinding Coffee Beans The Machine Shop Way

Okay, so you bought a bag of heavenly-smelling single-origin beans down at the hipster coffee shop, but forgot to have them ground. What do you do? If you’re [Jimmy DiResta], there’s no way you can run down to Walmart and pick up a grinder for $15. You commune with your tools and spend a few hours building a grinder from stuff lying around in the workshop.

This hand-crank grinder would make a great post-apocalyptic appliance, as long as we still have a way to heat water. [Jimmy] started with an old manual abrasive disc grinder, like for grinding metal, not beans.

After oiling it up to run without a hitch, he pulled out a couple of conical gears and got to work mounting one to the grinder shaft and the other to the business part of a vintage industrial light fixture.

We thought for sure this was going to be a burr grinder, but were a bit disappointed to watch [Jimmy] drill holes through a utility knife blade in order to make a blade grinder. Honestly, we’re kind of surprised that he didn’t machine some burrs, but the result is impressive and lovely nonetheless.

We love that the whole thing quick-disconnects from the grinder thanks to a custom cuff that holds the light bulb just so, we just hope that [Jimmy] gave that light bulb a good cleaning first. Grab a cup of whatever and check out the build video after the break.

Not exactly your kind of shop? You could always print an emergency coffee grinder.

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Steam Engine Replica From LEGO

If engineering choices a hundred years ago had been only slightly different, we could have ended up in a world full of steam engines rather than internal combustion engines. For now, though, steam engines are limited to a few niche applications and, of course, models built by enthusiasts. This one for example is built entirely in LEGO as a scale replica of a steam engine originally produced in 1907.

The model is based on a 2500 horsepower triple-expansion four-cylinder engine that was actually in use during the first half of the 20th century. Since the model is built using nothing but LEGO (and a few rubber bands) it operates using a vacuum rather than with working steam, but the principle is essentially the same. It also includes Corliss valves, a technology from c.1850 that used rotating valves and improved steam engine efficiency dramatically for the time.

This build is an impressive recreation of the original machine, and can even run at extremely slow speeds thanks to a working valve on the top,¬† allowing its operation to be viewed in detail. Maximum speed is about 80 rpm, very close to the original machine’s 68 rpm operational speed. If you’d prefer your steam engines to have real-world applications, though, make sure to check out this steam-powered lawnmower.

Thanks to [Hari] for the tip!

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Flywheel Trebuchet Spins Right Round

Most of us gained a familiarity with siege weapons from Age of Empires, and the march of technology has meant these relics aren’t typically seen on modern battlefields. However, development continues apace in the enthusiast community, and [Tom Stanton]’s latest trebuchet design puts a different spin on launching projectiles at speed.

The design takes advantage of the flywheel as an energy storage device. The flywheel is spun up to speed using a hand crank, through a timing belt and a set of hybrid 3D printed and CNC aluminium gears. Once spun up to sufficient angular velocity, a trigger releases the tennis ball payload from a sling, flinging it forth at speeds over 180 miles per hour.

Moving on from classical materials such as wood and nails, [Tom]’s latest design relies on aluminium in an effort to build something that won’t rot when left outside in the rain. The use of aluminium profiles also makes adjustment and redesigns easy, while providing the necessary adjustments to dial in things like release point and belt tension. We’ve featured a few different designs over the years; the walking-arm trebuchet is perhaps the most oddball of all. Video after the break.

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Hackaday Podcast 079: Wobble Sphere, Pixelflut, Skeeter Traps, And Tracing Apps

Hackaday editors Mike Szczys and Elliot Williams gaze upon the most eye-popping projects from the past week. Who would have known that springy doorstops could be so artistic? Speaking of art, what happens if you give everyone on the network the chance to collectively paint using pixels? There as better way to catch a rat, and a dubious way to lure mosquitoes. We scratch our heads at sending code to the arctic, and Elliot takes a deep look at the contact tracing apps developed and in use throughout Europe.

Take a look at the links below if you want to follow along, and as always, tell us what you think about this episode in the comments!

Take a look at the links below if you want to follow along, and as always, tell us what you think about this episode in the comments!

Direct download (60 MB or so.)

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