Step the Halbach from My Magnets

[Klaus Halbach] gets his name attached to these clever arrangements of permanent magnets but the effect was discovered by [John C. Mallinson]. Mallinson array sounds good too, but what’s in a name? A Halbach array consists of permanent magnets with their poles rotated relative to each other. Depending on how they’re rotated, you can create some useful patterns in the overall magnetic field.

Over at the K&J Magnetics blog, they dig into the effects and power of these arrays in the linear form and the circular form. The Halbach effect may not be a common topic over dinner, but the arrays are appearing in some of the best tech including maglev trains, hoverboards (that don’t ride on rubber wheels), and the particle accelerators they were designed for.

Once aligned, these arrays sculpt a magnetic field. The field can be one-sided, neutralized at one point, and metal filings are used to demonstrate the shape of these fields in a quick video. In the video after the break, a powerful magnetic field is built but when a rare earth magnet is placed in the center, rather than blasting into one of the nearby magnets, it wobbles lazily.

Be careful when working with powerful magnets, they can pinch and crush, but go ahead and build your own levitating flyer or if you came for hoverboards, check out this hoverboard built with gardening tools.


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Stop Buying Expensive Circular Saw Blades, Use Paper Instead

[John Heisz] was contemplating the secrets of the universe when an errant thought led him to wonder, could I use a sheet of paper as the blade in my table saw?

He takes a sheet of regular printer paper, draws a circle on it the same diameter as his regular blades, and cuts it out. He then bolts it into place on the spindle, slots in the table saw insert for really really thin kerf blades, and fires it up.

The blade is surprisingly dangerous. One would maybe expect a paper blade to be minimally damaging to a finger at best, but it quickly shows itself to be capable of tearing through paper and cutting through wood at a reasonable clip. Since the paper is minimally conductive, a SawStop couldn’t save someone from a lack of caution.

The blade finally meets its match half way through a half-inch thick piece of wood scrap. Wood and paper dust explode outward as the experiment ends. Video after the break.

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