Page:Motors and motor-driving (1902).djvu/184

152. Perhaps the best known of this type of machine is the 'Simms-Bosch.' The magneto consists of a number of horseshoe-pattern magnets supported on a metal base, on the inner faces of which are fastened two pieces of metal known as pole-pieces, provided with hollow faces, within which is fastened an H-shaped piece of soft iron (armature). The channels of this armature are filled with insulated wire. In the space between the armature and pole-pieces a 'shield' or tube of soft iron is caused to oscillate. To one end of this shield is attached a crank, operated by a connecting rod from the half-speed shaft on the engine.



When the shield is caused to oscillate rapidly, currents of electricity are induced in the winding of the armature. These currents are led away through a connected insulated wire to a special device which automatically makes and breaks a circuit in the interior of the combustion chamber. The action is as follows:—The wiper is normally at rest upon the stud, which is brought through the wall of the combustion chamber and terminates in a nut to which the wire from the magneto is attached. At the other extremity of is attached a small rod brought through the flange and connected to, which is capable of moving about a pivot. This pivot is in electrical