Practical Hand Book of Gas, Oil and Steam Engines / Stationary, Marine, Traction; Gas Burners, Oil Burners, Etc.; Farm, Traction, Automobile, Locomotive; A simple, practical and comprehensive book on the construction, operation and repair of all kinds of engines. Dealing with the various parts in detail and the various types of engines and also the use of different kinds of fuel.

by John B. Rathbun

(103) The Wico High Tension Igniter.

The Wico igniter produces a spark similar to that of the conventional high tension magneto except that the heat of the spark is independent of the engine speed. In other respects it is very different from the types described in the preceding pages for its motion is reciprocating instead of being rotary, and because all of the wire is stationary, the only movement being that of the iron core that passes through the center of the fields. The fact that the spark is of the same intensity at all speeds makes this device particularly desirable in starting the engine at which time the mixture is always of the poorest quality.

Fig. 113. Wico Igniter. High Tension Reciprocating Type.

It is very simple, and is without condensers, contact points or primary windings, and has no parts that require adjustment.

The current is generated by the reciprocating movement of two soft iron armatures shown as a bar across the bottom of the two coils, which move alternately into and out of contact with the ends of the soft iron cores. The movement of these armatures in the upward direction is produced by the motion of the engine and the speed of this movement is, of course, proportional to the speed of the engine. The downward movement, which produces the spark, is caused by the action of a spring, is much more rapid than the upward movement and entirely independent of the speed of the engine.

The magnets are made of tungsten steel, shown as two bars across the top of the coils, hardened and magnetized and are fastened by machine screws to the cast iron pole pieces, which serve to carry the magnetic lines of force from the poles of the magnets to the soft iron cores. The cores, which fit into slots milled in the pole pieces, are laminated or built up of thin sheets of soft iron, each sheet being a continuous piece, the full length of the core. Each core, extends from just below the top armature, down through the pole piece, and coil to just above the bottom armature.

Each armature consists of a number of laminations or sheets of soft iron mounted on a spool shaped bushing, which, in turn, is loosely fitted onto the squared end of the armature bar. The armature bar is supported with a sliding fit in a box shaped guide which is fastened in the case.

On the outer ends of the armature bar are spiral springs held in place by cup shaped washers and retaining pins, the combination making a self-locking fastening similar to the familiar valve spring fastening used almost universally on gas engines. These springs bear against the armatures and tend to force them against the shoulders of the armature bar.

The coils each have a simple high tension winding of many turns, thoroughly insulated and protected against mechanical injury. They are connected together in series by means of a metal strip, thus making one continuous winding. In the single cylinder igniter, one end of the winding is grounded to the case of the igniter, while the other end is connected to the heavily insulated lead wire. This lead wire passes out through a stuffing box, packed with wicking and thoroughly water tight, direct to the spark plug in the cylinder.

In the two cylinder machine no ground connection is used, but both ends of the winding are connected to lead wires passing out of the case to the spark plugs.

The action of the igniter is as follows:—As the driving bar, through its connection with the engine, is moved downward to its limit of travel, carrying the latch with it, the shoulder on the side of the latch snaps under the head of the latch block. As the motion reverses the latch carries the latch block and armature bar upward. The lower armature, being in contact with the stationary cores, cannot rise with the armature bar, but the lower armature spring is compressed between its retaining washer and the armature, while the bar rises and carries with it the upper armature, which bears against the upper shoulders on the bar.

As the driving bar continues its upward motion the upper end of the latch meets the lower end of the timing wedge and, as the wedge is held stationary by the timing quadrant, a further movement of the latch causes it to be pushed aside until the shoulder on the latch clears the latch block and releases it.

As the lower armature spring is at this time exerting a pressure between the armature bar and cores through the medium of the lower armature, the instant the latch block is released, the armature bar is quickly pulled downward, carrying the upper armature with it. Just before the motion of the upper armature is stopped by its coming in contact with the cores, the lower shoulders on the armature bar come in contact with the lower armature, and, as the bar has acquired considerable velocity, its momentum carries the lower armature away from the cores against the pressure of the upper armature spring, which thus acts as a buffer to gradually stop the movement of the armature bar. The armature bar finally settles in a central position.

The timing of the spark is accomplished by releasing the armature bar earlier or later in the stroke. This is done by shifting the position of the eccentric timing quadrant, which in turn varies the position of the wedge so that the latch strikes it earlier or later in the stroke. The timing quadrant is furnished with several notches into one of which the top of the wedge rests, thus holding the quadrant in the desired position.

The motion should preferably be taken from an eccentric on the cam shaft of a single cylinder four cycle engine, or the crank shaft of a single cylinder two cycle or a two cylinder four cycle engine. On a two cylinder four cycle engine, it is sometimes more convenient to drive the igniter from the cam shaft, using a two throw cam to produce the required number of sparks. In this case the shape of the cam should be such as to duplicate the motion of the eccentric. That is, it should start the driving bar slowly from its lower position, move it most rapidly at mid stroke and bring it to rest gradually at the upper end of the stroke, exactly as is done by the eccentric motion.

When an eccentric is already on the engine the motion may be taken from it to an igniter with a driving bar through a properly proportioned lever that will give the required length of stroke. Where a plunger pump is used on the engine the motion can usually be taken from the pump rod. Where an eccentric has to be provided especially for the igniter, the driving bar is generally used with its roller running on the eccentric.