Bendy magnets are proving a big attraction – up to 7.5 tonnes of pulling force – for divers, and workers on dry land.
When submerged, the problem is staying close to an object while exerting pressure against it. The tendency is to float away. This is counter-productive if force is needed, for example repairing a ship’s hull.
Magnets are usually flat so it is difficult to attach them to curved steel surfaces. The gap between the magnet and the surface weakens the magnetic field.
Medical and optical device designer Diverse Technologies & Systems of Cambridge has come up with the flexible electro-magnet which self-adjusts to a curved profile.
Take a doughnut and cut it into six equal segments and you have the basis of the magnet’s design. The individual segments, made from soft iron, are joined by tough, slightly flexible rubber. This allows a minimum gap and hence maximum pull.
Around the inside of the doughnut is a copper coil insulated in a potting compound. When the current is on, the magnet is energised, with the inner and outer rings corresponding to the north and south magnetic poles.
For underwater applications, the magnet has an umbilical cord of up to 300m. On land, it could be used to attach metal to metal while machining, lifting or welding.