As the inductors approach position A, the magnetism through the winding is increasing and as they leave that position the magnetism begins to decrease, without changing its direction. The direction of the induced electromotive force is reversed as the inductors pass through position , and is again reversed when they pass through position C. As the inductors approach position B, the magnetism through the winding is from front to back and decreasing, but after they have passed this position, it is from back to front and increasing, resulting in no reversal of the electromotive force. This is also true of position D.
Although the current from an inductor magneto may be utilized in the same manner as that from any other alternating current magneto, the above sets forth the conditions existing in the Remy magneto. This instrument generates a low-tension current and requires an outside coil to step up the current to the high potential required at the spark plugs.
In the K.W. inductor type of magneto (Figs. 59 and 60) there are four inductors as illustrated made of soft iron laminations. Two of these inductors are placed 180 degrees to each other and the other two in a plane at right angles.
The windings, which are concentric with the inductor shafts are mounted between the inductors and stand absolutely still. The inductors collect the magnetism from one pole piece and conduct it through the center of the windings to the opposite pole piece. The primary winding is surrounded by the secondary winding. The primary current passes through the circuit breaker and at the moment of interruption a powerful surge of current is generated in the secondary winding, which is distributed to the spark plugs, thus producing a high-tension current without the aid of external coils. This is one type of inductor magneto generating a high-tension current. The Pittsfield magneto (Fig. 61) offers another example of a high-tension inductor type magneto; however, it differs materially from the above. The usual primary and secondary windings are used, however, they are not incorporated with the inductor shaft, but are located at the rear of the magneto.
The three illustrations show a longitudinal section through the entire instrument, cross section through the magneto and pole pieces and end view of the interrupter.
The magnetic field contains four poles, two (4-1) of which are the poles of the permanent magnet as illustrated, the other two poles (4) and the iron core (5) of the coil compose the field. The rotation of the inductor shaft (1) generates in the windings of the coil (6) an alternating current which attains a maximum four times during each revolution of the inductor shaft, which means, that for each 90 degrees rotation of the inductor shaft, ignition may he obtained. One end of the primary winding is connected to the field by a contact (8) and its other end is attached to a contact block (9) which is screwed on the field and insulated by a hard rubber bushing and plate. Connection from this plate to platinum contact block (9) and screw is made by a brass contact strip. The latter is insulated from the interrupter plate (11), which is in metallic connection with the field or ground.
The platinum screw (13) on the interrupter lever (12) is held against the platinum screw (1) in the insulated block by means of a spring (14). The current generated in the primary winding is therefore short circuited as long as the two platinum screws are in contact.
The primary current is interrupted when the core (15) actuates the lever (12) separating the platinum points. A condenser (16) protected by a housing (17) is connected in parallel to the interruption of the platinum points. One end of the secondary winding is connected to one end of the primary winding and the other is led to a conductor by means of a metal bridge (19). The secondary current is led from this bridge members to the distributor (23) by means of insulated conductors (18), which are connected by means of a carbon brush and spring. In the distributor plate (23) are socket inserts connected to distributing inserts which take the high-tension current from the revolving conductor (21) in proper rotation and from socket inserts in the distributor plate (23) cables are connected to the spark plugs in the cylinders.
The safety spark gap consists of a short pointed brass rod set on the metal bridge (19) connecting the high-tension terminal (26) on the coil (6) with the high-tension conductor bar (18), and should there be any interference with the circuit normally provided through the spark plugs, the safety gap provides a point of discharge.
The timing of the spark is generally accomplished by opening the interrupter earlier or later, and with the unavoidable result that if the position of the pole pieces in the magnetic field remains stationary, the relative position of inductor shaft and field at the moment of the break must vary. The quality of the spark, or, in other words, the heat value, depends among other factors upon the particular position of the inductors in relation to the field poles at the moment the spark is produced.
The changing of the timing is effected in the Pittsfield magneto in a unique way. The results obtained are ideal in that the same efficient spark is obtained, when the spark is either advanced, retarded or in any intermediate position. This is accomplished by means of a four-segment sleeve (no. 27), one for each pole of the machine, which sleeve is fitted with a lever with which the sleeve, with interrupter, can be advanced or retarded, giving early or late ignition.
The inductor type of magneto is also made in the dual type; in fact, in the Remy, the same transformer coil, interrupter and distributor as is used for the magneto current. With the K.W. it is necessary to employ an external coil.
The Pittsfield dual system is somewhat different from the other types explained, and owing to the unique construction it is very simple. It does away with the high-tension coil and wires from the magneto to the switch, the dual system being self-contained.
The design and constructional details of the dual machine differ from the independent type, as previously described, by insulating both ends of the primary circuit instead of one end. One end of the primary winding is connected to the interrupter as in the independent type, the other to the lever of a specially constructed switch, so that when the switch lever is on the side marked "Magneto," this primary lead is grounded, allowing the magneto to run as a straight high-tension machine. When the lever is thrown to the battery side of the switch the primary lead is then connected to the batteries, thus permitting the primary and secondary windings of the magneto to be used for either current.
Fig. 59. K.W. Inductor Shaft.
Fig. 60. K.W. High-Tension Inductor Magneto.
Fig. 61. Longitudinal Sectional, Cross-Station and End Views of Pitta-field Magneto.