A very popular type of magneto used on early model single cylinder gasoline engines was the reciprocating armature induction type magneto that is so difficult to locate these days.
This magneto was so simple in design that very little could go wrong with it. The only moving parts on the magneto were the armature and contact points (see Fig. 1). The armature moved about 1/4 inch back and forth. The contact points moved about 1/16 inch.
Referring to figures 1, 2 and 3 for illustration, the parts of the magneto consists of items shown in the numbered lines below:
- This magneto operates on the basic principles of all magnetos concerning magnetism and electricity. The theory is that any time a magnetic line of force is interrupted, changed or collapsed, an electric current is created.
1. A laminated bar called the armature. (K, fig. 1 and 2)
2. Lower contact point connected to the armature. (P fig. 1 and 2)
3. A condenser (fig. 2), one terminal connected to the upper contact point, (UP, fig. 3), and the other terminal connected to ground, (B, fig. 3) with the primary lead wire terminal.
4. Spark plug wire terminal (SP, fig. 1)
5. A set of magnets. (M fig. 3) (NS fig. 2)
6. Two soft iron cores. (A, fig. 2 and 3)
7. Primary and secondary windings. (fig. 2)
8. Brass cover around main frame (D, fig. 1)
9. Machine screws attaching brass cover and side plates. (E, fig. 1) 10. Guide rod for armature (GR, fig. 3)
This electric current for the WICO EK Magneto was created by pulling the armature away from the magnet coil cores. The armature was connected to a rocker arm that was activated by a sliding bar. (see fig. 4)
This armature movement created a current in the windings around the magnet cores. The collapse of this current was created by separating the contact points in this magneto. The contact points were connected to the armature. The collapse of this primary winding circuit induced a high voltage build up in the secondary winding. This surge of high-voltage current caused the spark at the spark plug.
The voltage produced by this magneto was not equal to the high tension spark of 20,000 volts produced by rotating armature magnetos of later design. To test this EK magneto, a spark that would jump a 1/8-inch gap was considered sufficient to ignite the mixture in these low compression engines.
In order for this magneto to function properly, it was very important to make precise measurements for the point opening. The contact points were also critical in that they had to be in perfect condition, clean and dry. There is an adjustment for the points on the machine screw that attached to the armature. With the magneto removed from the engine, and the brass cover removed to expose the contact points the procedure to adjust them on the type drive illustrated, (fig. 4) is:
- The spring that returns the contact points to their seat should also be free and active. While the armature was removed from the core, clean the contact surface of the armature and core, use sandpaper or fine cut file to clean the surfaces. Be careful not to round off the surfaces, they must remain flat.
1. Pry the armature (K, fig. 2) from the core (A, fig. 2) with a screwdriver.
2. Insert a 3/32 inch drill bit between the core and the armature and return the armature to rest against the drill bit. (Gap G, fig. 2)
3. Adjust the machine screw for the contact points so that the lower contact has just unseated from the upper contact, perhaps 0.004 inch, which should be visible to the eye. Be sure the upper contact point is insulated from frame.
4. Remove the 3/32 inch drill bit and assemble the unit.
This magneto could be tested quite easily. It is quite doubtful that the magnets would lose their magnetism, the effort required to pry the armature from the core would indicate the effective magnetism. Some instructions manuals say the magnets should hold a ten pound weight.
There were two coils in this magneto with primary and secondary windings. They were connected by a short lead between the two coils. A tune-up service station that could check ignition coils could also check these two coils. They have primary lead wires and secondary windings the same as any conventional coil. They could be checked separately or togetherwithout removing the coil from the frame. The condenser is almost identical to an automotive condenser except for outward appearance. The tune-up service station around the corner could also check this condenser which is easily removed from the frame. They would be checking the condenser for leakage, capacity and series resistance.
To time the magneto to the engine we will refer to fig. 4, for one of three types of drive mechanism. The parts illustrated are shown below.
- To time this magneto on the 1-1/2 HP Economy engine and similar engines, the rocker arm, (RA) should be set to latch off when the spark line on the outer surface of the flywheel is adjacent to the push rod that opens the exhaust valve. This position is also when the piston and connecting rod are at the end of their compression stroke. Refer to fig. 4 for latch off position. The trip finger latch travel must be set on the push rod drive to provide a 1/4-inch movement of the armature from the core before it is released.
1. The rocker arm that moves the armature (RA)
2. The spring that returns the armature to the core through the rocker arm action. (RS)
3. The trip finger latch, attached to the cam actuated push rod. (TL)
4. The latch off screw that trips the rocker arm for return of the armature. (LO)
5. The drive spring for the trip finger latch. (DS)
6. The advance lever to retard and advance the spark, shown in advance position. (AL)
7. The latch block on the rocker arm. (LB)
For further information on this magneto, Jean Metcalf has reprints of the original instruction manual of the WICO EK magneto.