Self-propelled vehicle

A self-propelled vehicle for traversing a surface of magnetic material, comprising a body to which equipment is or may be attached, two or more endless tracks supporting said vehicle body and incorporating a plurality of permanent magnets spaced along each track, so that in use sufficient of said magnets are located relative to the surface being traversed to create a magnetic field of a strength to attach the vehicle to the surface, each permanent magnet being mounted for limited pivotal movement relative to the endless track about an axis substantially parallel to the direction of travel of the vehicle, and means to drive said tracks to propel the vehicle over the surface while the vehicle is held on the surface by the magnets, each permanent magnet comprising a bar of magnetised ceramic magnetic material extending in a direction transverse of the track, said bar being clamped between and secured to a pair of magnetic metal plates in direct intimate contact with the ceramic bar, said metal plates each extending beyond one face of the ceramic bar at opposite edges of said one face to provide respective magnetic poles of opposite polarity whereby in use, only said poles contact the surface being traversed and the ceramic bar is spaced from the surface being traversed.