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Magnetic Bearings, Eddy Currents, And Mirroring

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My first thread! Yay!


I've been in the process of designing my own E-LSA (Experimental Light Sport Aircraft) for a few years now. Throughout this design process I have been trying to stay on the cutting edge of material and design processes. One such aspect of these designs has been regarding bearings. My current design incorporates a ducted fan design with blades that run the perimeter along the inside of the duct (essentially the inner wall of the duct rotates with the blades). That design idea aside, I've been trying to develop a way to create bearings that could handle such a large mass, moderately unstable operating conditions, and large circumference. Traditional ball bearings are expensive on that scale and will wear quickly. Fluid bearings are complex and failure would have huge repercussions... involving the ground and some fire/blood.


Trying to find a reliable, super-stiff, and maintenance free bearing sounds damned near impossible.


But, I found a very interesting thesis: http://www.diva-portal.org/smash/get/diva2:7845/FULLTEXT01.pdf - it details the construction of a simple axial homopolar bearing using a rotor made of aluminum or copper. Apparently the author managed to make a fairly stable bearing capable of moderate to high speeds with high stiffness in such a configuration.


My hope is to scale this up using a copper or aluminum sheet shell for the inner wall and axially magnetized rings or perhaps even simple (strong) bar magnets laid side by side. Either static magnetic or heavy duty roller bearings along the ends will serve as the caps; or landing bearings should anything fail.


My hope is that the large diameter of the rotor will add to the stiffness of the bearing (higher speed along the circumference = stronger magnetic mirroring) if I understood the paper correctly.


Any thoughts? Anyone here ever encounter something like this before? I know my current propulsion design is unorthodox. I'm still working on it but I'd like to keep away from that design element for the moment and focus on the bearing.


I'll be doing a proof of concept with some smaller materials to see what sort of stability I can generate. If I can keep everything to scale (magnetic field, size, speed) I think I may just have an idea here that can help reduce my power losses, reduce complexity of the build, and keep me safe.  :cool:


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