next thing is to make sure that the contact breaker points are in contact when the bell crank lever is out of contact with the cam in the sides of the breaker box in the type Bosch DU-4 or away from the fibre cam rollers in the type D-4. It is also important that the platinum points are separated by the proper distance, about .5 millimeter, where the lever C F at A, Fig. 124, is in contact with the cam. If the points are too far apart they should be brought nearer together by loosening the lock nut on the ad

Fig. 124.-Construction of Bosch Contact Breaker Made Clear at A. B-How to Clean Contact Breaker Points. C-Bosch Contact Breaker Assembly Removed from Armature. D-The Remy Contact Breaker.

justing screw shown at C, and screwing it up to lessen the difference, or to screw it back and open the gap if it is not sufficient. The platinum contact points must also be cleaned, any dirt or oil being easily removed, as shown at B, by gasoline

squirted on them from a small hand oil can. In case the contacts are uneven, pitted or blackened, they must be smoothed with a jeweler's fine cut file. After continued use, if the platinum points have worn down the platinum-pointed screw must be renewed. It is also important to make sure that the high tension current collecting brush is in contact with the collector ring, and that the

conducting pencil makes proper contact with the brush, against which it bears. The interior of the distributor must be clean and free of metallic or carbonaceous matter. The distributing brush must bear positively against the distributor section and the interior of the distributor should be smooth and all contacts clean and bright.

Mention has been previously made of making sure that the screw which keeps the contact breaker assembly in proper relation with the armature shaft is tight, which calls for careful examination. If this screw is loose, the contact breaker assembly will not move in proper timed relation with the armature; in fact, it may not move at all, which will prevent the contact point from separating and which will also result in failure of the ignition. If everything appears to be all right about the magneto, the timing should be verified to make sure that the spark is occurring at the right time in the engine cylinders. It is easy to tell if the magneto is producing a spark of proper intensity by uncoupling a spark plug conductor and holding it a short distance away, not more than " from the terminal. If a magneto is functioning properly a spark will jump the air gap thus created.

At Fig. 124, D, the contact breaker and distributor construction of the Remy magneto is shown. It will be observed, in this case, that the contact breaker assembly does not rotate, as in the Bosch, but that a rotating two-point cam is attached to the armature shaft and interrupts the contact between the points P by bearing against the end of the bell crank CF. The instructions given for care of the Bosch magneto apply just as well to this device. Realizing the importance of having the gap between the contact breaker points of the proper amount, the magneto manufacturers furnish gauges which are to be used for testing this gap. That shown at Fig. 126, A, is for use with the Eisemann magneto. With the contact breaker removed, as indicated at B, the contact points C-4 should be together as indicated. When the gauge is inserted in the hole. C-7 it will indicate the correct amount the point should be separated. The gauge at Fig. 126, C, is merely a piece of thin sheet steel of the proper thickness which is used as indicated when the points are separated by the bell crank lever riding on the cam block.

Recharging Weak Magnets.-After a high tension magneto has been in use for a time the magnets lose their strength and it is necessary to recharge them in order to restore the magneto to its full efficiency. When magnets are weak the resulting secondary

spark will also be weak and the motor will not run regularly, no matter how carefully the device is adjusted. If the motor does run without misfiring it will not develop its full power if the magnets are weak. An electro-magnet designed to operate on 110-volt current is shown at Fig. 127, A. The core is of soft iron, 1′′ in diameter and 81⁄2" long. They are drilled at the bottom for a retaining screw, which is intended to keep them in contact with a base plate of steel 41⁄2" x 9". Two blocks of steel 134" x 2" x 4" are drilled to receive the cores, and have set screws in the side so they can be clamped tightly against the core to form polepieces. A brass tube about 16" thick at the side, having flanges at each end projecting over to hold fiber insulating plates as shown, may be turned to the dimensions indicated in a lathe or may be made up of sheet stock if desired. The hole through the center of the brass spool is of such size as to permit the core to fit freely in its interior. Besides this equipment, 22 lbs. of No. 20 B. & S. gauge insulated copper wire will be needed. Eleven pounds is wound around each brass tube, winding one coil in one direction and the other the opposite way. Leave about 6′′ of wire when starting to wind the coil in order to make a connection between them. After both coils have been wound shellac them thoroughly and wind insulating tape over the outside. The cores are then fastened to the iron base plate, the coils are slipped over the cores and the pole pieces attached to keep the coils in place. The view of the completed magnet is clearly shown in the assembly. This can only be used with 110 volts direct current.

Before recharging the generator magnet it is important to test the polarity of the electro-magnet, as the north pole of the magnet to be charged must be brought in contact with the south pole of the electro-magnet and vice versa. It is not difficult to ascertain the polarity by using an ordinary compass or magnetic needle, the marked pole of which will point toward the north. Once the polarity has been determined the poles may be marked in any desired way, usually by stamping the north pole N and the south pole S. Another magnet-charging device, which was described in the Commercial Motor, utilizes storage batteries as a source of magnetizing current. The magnets are composed of soft iron core