are placed 60 degrees apart, as indicated at D. The speed at which the armature of the magneto turns also varies with the number of cylinders. One- and two-cylinder forms turn at cam-shaft speed. The three-cylinder types when applied to a four-cycle engine turn at three-quarters the crank-shaft speed. The four-cylinder magneto armature is driven at crank-shaft speed, while that of the sixcylinder forms turn at one and one-half times crank-shaft speed. When used on two-cycle motors, the speeds given for four-cycle engines of the same number of cylinders should be doubled.

The important parts of a four-cylinder form of high-tension magneto are shown at Fig. 94, which is a view of a partially dismantled device. The armature assembly and one of the end plates by which it is supported are shown at the extreme left. Attached to the end of the armature shaft are the distributor drive pinion and the ebonite spool which carries the collector ring. The timer case and interrupter assembly are shown at the extreme right. Above it the distributor case is clearly depicted. When the device is assembled the end of the armature shaft protrudes through the housing at the lower part of the magnet assembly which is shown in the center of the group, with the end plate which carries the distributor gear and disk and one end of the armature in place. The distributor gear serves to drive a hard rubber plate in which the distributor segment is imbedded. When the distributor case is screwed in place, the carbon brushes, which are spaced around the interior of the distributor case, collect current from the revolving distributor segment and lead it to the spark plugs by suitable cables which run from the terminals at the top of the distributor casing.

Two systems of high-tension magneto ignition are used, one termed the true high-tension system, in which a current of high potential is delivered directly from the armature; the other is the transformer coil system, so termed because the current produced by the armature winding is of low tension and must be stepped up or increased in value before it is delivered to the spark plug by an induction coil similar in construction to that needed in batteryignition systems. In the former apparatus the high-tension current is produced by means of a secondary winding on the armature itself, and as the whole apparatus is self-contained it is much more

compact and simpler to install than those which need a separate transformer coil.

The simplified wiring system of a true high-tension magneto is shown at Fig. 95. The armature carries two windings, one indi

cated by the heavier lines at the bottom called the "primary"; the other, composed of finer conductor, is known as the "secondary." One end of the primary winding is grounded, the other is joined to the fixed contact screw of the contact breaker. This end is also joined to one end of the secondary winding and the free end of the

Fig. 96.-Wiring Diagram Outlining Method of Combining Remy Magneto and Transformer Coil to Form Ignition System for Four Cylinder Engines.

secondary winding is attached to the collector ring carried by the ebonite spool. When the contact points separate, a current is induced in the primary and secondary windings and is delivered to the center terminal of the distributor disk by the carbon brush which bears against the collector ring. The various segments of the distributor are connected to the spark plugs in the cylinders, and

every time the contact points separate a spark will be produced at one of the plugs because the revolving distributor brush will be in contact with one of the distributor segments.

The wiring of a four-cylinder magneto which employs a transformer coil is shown at Figs. 96 and 97. A set of batteries is pro

Fig. 97.-Typical Transformer Coil-Magneto System for Four Cylinder

Ignition.

vided to furnish current for starting, as it is sometimes difficult to turn the motor sufficiently fast by hand to generate the proper amount of magneto current to insure prompt starting. The hightension wire from the spark coil or transformer is led to the center of the distributor and the current is commutated to the plugs just as though the high-tension current had been produced in the magneto itself instead of in the transformer.