Simple Demo Shows The Potential Of Magnetic Gears

We’ve probably all used gears in our projects at one time or another, and even if we’re not familiar with the engineering details, the principles of transmitting torque through meshed teeth are pretty easy to understand. Magnetic gears, though, are a little less intuitive, which is why we appreciated stumbling upon this magnetic gear drivetrain demonstration project.

[William Fraser]’s demo may be simple, but it’s a great introduction to magnetic gearing. The stator is a block of wood with twelve bolts to act as pole pieces, closely spaced in a circle around a shaft. Both ends of the shaft have rotors, one with eleven pairs of neodymium magnets arranged in a circle with alternating polarity, and a pinion on the other side of the stator with a single pair of magnets. When the pinion is spun, the magnetic flux across the pole pieces forces the rotor to revolve in the opposite direction at a 12:1 ratio.

Watching the video below, it would be easy to assume such an arrangement would only work for low torque applications, but [William] demonstrated that the system could take a significant load before clutching out. That could even be a feature for some applications. We’ve got an “Ask Hackaday” article on magnetic gears if you want to dive a little deeper and see what these interesting mechanisms are good for.

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Benchtop Lathe Gets An Electronic Leadscrew Makeover

The king of machine tools is the lathe, and if the king has a heart, it’s probably the leadscrew. That’s the bit that allows threading operations, arguably the most important job a lathe can tackle. It’s a simple concept, really – the leadscrew is mechanically linked through gears to the spindle so that the cutting tool moves along the long axis of the workpiece as it rotates, allowing it to cut threads of the desired pitch.

But what’s simple in concept can be complicated in reality. As [Clough42] points out, most lathes couple the lead screw to the spindle drive through a complex series of gears that need to be swapped in and out to accommodate different thread pitches, and makes going from imperial to metric a whole ball of wax by itself. So he set about building an electronic leadscrew for his lathe. The idea is to forgo the gear train and drive the leadscrew directly with a high-quality stepper motor. That sounds easy enough, but bear in mind that the translation of the tool needs to be perfectly synchronized with the rotation of the spindle to make threading possible. That will be accomplished with an industrial-grade quadrature encoder coupled to the spindle, which will tell software running on a TI LaunchPad how fast to turn the stepper – and in which direction, to control thread handedness. The video below has some great detail on real-time operating systems on microcontrollers as well as tests on all the hardware to be used.

This is only a proof of concept at this point, but we’re looking forward to the rest of this series. In the meantime, [Quinn Dunki]’s excellent series on choosing a lathe should keep you going.

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Unicycle Given A Hand Crafted Gear Box

Being able to coast on a bicycle is a feature that is often taken for granted. The use of a freewheel was an improvement made early in the bicycle’s history, for obvious reasons. This also unlocked the ability to build bikes with multiple gears, allowing higher speeds to be easily reached. On a unicycle, however, there’s no chain and the pedals are permanently fixed to the wheel’s axle, meaning that there is (usually) no freewheel and no gearing. [johnybondo] wanted to get some more speed out of his unicycle, though, and realized he could do this with his own homemade internal geared hub for his unicycle.

The internal hub gear was machined and welded by hand as a one-off prototype. There are commercial offerings, but at $1700 it’s almost best to fund your own machine shop. It uses a planet gearset which is more compact than a standard gear, allowing it to fit in the axle. Once all the machining was done, it was time to assemble all of the gears into the hub, lace it to the wheel with spokes, and start pedaling away. Since it was so successful, he plans to build another and lace it to a larger wheel which will allow him to reach even higher speeds. If this isn’t fast enough for you, personally, there are other options available for ludicrous speed.

Now, this gear is still “fixed” in the sense that it’s a permanent gear ratio for his unicycle and it doesn’t allow him to shift gears or coast. There’s no freewheel mechanism so the unicycle can still be pedaled forward and backwards like a traditional unicycle. The advantage of this setup is that the wheel spins 1.5 times for every one revolution of the pedals, allowing him to more easily reach higher speeds.