Interest in designing electromagnetic engines grew following the discovery of electromagnetism in 1821 and by the late 1830s a number of designs had been tried. Unfortunately, however, electromagnets produce a large force only at very short range. Charles Wheatstone (1802-1875) tried to overcome this problem. He took out a patent on his designs in 1841 and three examples survive. In this, the earliest version, the moving part is a ring mounted eccentrically inside a ring of electromagnets.
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