Зображення сторінки

The distributor on the four- and six-cylinder models (Fig. 6) consists of an insulating block with a short spindle at one end of which is a spring brush bearing on the contact quadrant P on the windings. The high-tension current passes from this point to a radial arm on the distributor face and so to the outer terminals of the instrument. A good feature is the shortness of the path for the current from the windings to the terminals. A safety spark gap is included in the high-tension circuit at the base of the windings, and the condenser is located on top.

In the circuit breaker (Fig. 106, C) it will be seen that nothing revolves except the cam attached to the shaft. By this construction it is possible to adjust the contact points while running as the contact bases are stationary. The grounding terminal is insulated on the end of the spring clip which holds the breaker cover in position and as it bears on the center of the cover the ground wire is also stationary while moving the timer arm.

The four- and six-cylinder instruments are identical in every respect except the distributor and timing gears. In the eightand twelve-cylinder models the shape of the rocking field and also the polar extensions are changed so that four sparks can be produced in each revolution. The laminated pole pieces embrace 50° each of the upper half of the tunnel, instead of 90°. In order to obtain the requisite number of magnetic reversals with these pole faces the main polar extensions are in the form of a cross, two ends being of N polarity and two of S.

The New Compound Distributor.-As it is practically impossible to obtain more than six contacts in a flat distributor disk of ordinary construction without a great risk of short-circuits caused by dangerously small electrical hazard distances, a particularly ingenious compound distributor (Fig. 106, E and F) has been designed for the eights and twelves in which the terminals are not arranged in one plane as in the four- and six-cylinder models, but in two parallel planes. In the compound distributor block on the eightcylinder instrument the high-tension current is led through the center of the block from the brush C in contact with the windings to the brush D which bears on the center of the cruciform contact plate S embedded in the distributor box. This plate has no con

nections with any terminals, but is a means of conducting the current in turn to the eight terminals as follows: In operation the plate S becomes “live” by contact with the brush Das before explained. Rotating over the ends of S are the two brushes Al

[graphic][subsumed][subsumed][ocr errors][subsumed][subsumed]

Fig. 108.—Forms of Dixie Magneto. A-Six Cylinder. B-Eight Cylin

der. C-For welve Cylinder Engines. -View with Cover and One Magnet Removed to Show Oscillating Coil and Pole Piece.

and B1 connected respectively to two similar brushes A2 and B2 in the side of the block. The path of the latter brush B2 includes the four contact pieces B connected to the four of the terminals, while the other brush A2 rotates in the path of the terminal plates A connected to the remaining four terminals. Now, since the two

brushes A1 and B1 are arranged 135o apart, it follows that eight sparks will be distributed to their respective terminals in one revolution of the distributor block in equal divisions of time. The timer gear is in the ratio of 2 to 1 so that this magneto runs at engine speed, an unusual feature of an eight-cylinder magneto. On the twelve the distributor gear ratio is 3 to 1, requiring a speed one and one-half times the engine speed.

The distributor for the twelves is identical in every respect except that the contact star at the base of the box is six-pointed instead of four, to supply the twelve terminals which are arranged in two layers, as shown in the external view (Fig. 108, C). By the use of the compound distributor block on the eights and twelves as many as 285 sparks of high intensity can be obtained per second. Owing to this high speed of spark production a double contact breaker having two breaker arms and contact points is used on the twelves.

Constructionally the Dixie magnetos are up to the present high standard of practice. The shaft runs on ball bearings, as shown at Fig. 107, tightly fitting brass side covers inclose the magnets and the whole instrument can be dismantled with no other tool than a screw driver. The magnet itself is in two parts and fits into place without bolting, having semi-circular notches which embrace the shaft bearing. Great accuracy has been used in the manufacture of the rotating pole extensions, the clearance between the ends and the stationary poles being brought down to the workable minimum. An interesting point in connection with the operation of these pole extensions is that end thrust is neutralized by the equal magnetic pull on both ends of the rotor. The compactness of the magnets can be realized from the dimensions which except in the height are practically identical in all models. The common width is 4.125 inches and the total length 8.375 inches. On the twelve the height of the magnet is 7.5 inches, being one inch more than the others so as to provide a stronger magnetic field.

The most popular form of magneto, if one can judge by the numbers of manufacturers using it, is the true high tension type with the revolving winding, though the low tension type using

transformer coils have also been used to a large extent. All mag. netos do not have rotating windings, three makes, the K. W., Splitdorf Dixie and early models of the Remy utilize a fixed winding and rotary inductor. The inductor pieces are used to conduct

[merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][graphic][subsumed][merged small]

Fig. 109.—Splitdorf Dixie Magneto Used on 1916 Overland Cars.

the lines of magnetic energy through the winding and produce the current by cutting the turns of wire. In the armature shown in the lower portion of Fig. 101 the windings revolve in the magnetic field and generate the current. Another form of magneto which is used on but one make of car, the Ford, but which enjoys a wide distribution, is shown at Fig. 110 in connection with the

complete ignition system of the car. Sixteen coils of coarse conductor are carried by a fixed plate, which is bolted to the engine crank case, as shown at Fig. 16. A number of horseshoe magnets, not shown in the illustration, are carried by the ends of the flywheel and revolve in front of the fixed coils, the space between the magnet poles and the cores of the windings being just. enough to provide clearance without danger of hitting the magnets. Owing to the large number of magnets and coils employed,

[graphic][subsumed][subsumed][subsumed][subsumed][subsumed][ocr errors][subsumed][subsumed][subsumed][subsumed]

Fig. 110.—Unconventional Transformer Coil-Magneto Ignition System

Used on Ford Cars.

a very strong current is obtained, which, while pulsating in character, is used in the same way as battery current would be through four individual vibrator coils, which are brought into circuit progressively by the rotary contact timer.

Transformer Coil Magneto Systems.—Methods of wiring typical transformer coil magneto systems are shown at Figs. 111 and 112 inclusive. At Fig. 97 all the parts of a system of this nature are clearly shown, and the wiring may be readily traced from the magneto or battery to the coil. It will be apparent that at the bottom of the single unit coil there are four primary terminals and one

« НазадПродовжити »