pieces about 6" long and 1" in diameter. The base is constructed of mild steel plate, the cores being fastened to the plates by screws or by turning down the end of the core and threading it to fit the hole in the base plate. Before screwing down the core pieces they are wound with No. 22 gauge insulated wire, the ends being left

SPRING
BALANCE

MAGNETOMETER

free. The wires are connected up to a pair of storage batteries, as shown, and the latter are so connected up that the polarity of the soft iron cores are north and south respectively. Enough of the wire is wound on to have coils of about 2" in diameter. If the core shows signs of overheating, low-voltage lamps should be placed in the circuit to introduce some resistance. The voltage of the lamp to be used depends entirely upon the voltage of the battery used to energize the magnet. It is stated that the magnets will be charged if they are merely placed in contact with the energized cores until they have absorbed sufficient magnetism to enable them to sustain a weight of 20 lbs., after which they are ready to be replaced on the magneto. This is shown at Fig. 127, B.

The illustration at C, Fig. 127, shows the

Seanor garage magnet

ARMATURE

--

B

MAGNET

Methods of Testing Magnet
Fig. 128.
Strength After Recharging. A-With
Spring Balance. B-With Magnetometer.

charging outfit, which is claimed to charge the magnet in one minute. From the exterior view of the device it will be evident that it consists of a base upon which are mounted two solenoid coils carried in square boxes. The magnets to be charged are inserted through the center of these coils during the energizing process. In order to accommodate a horseshoe magnet of any spread, one of the coil boxes is mounted so the distance between the

two openings is altered if desired. As ordinarily constructed, the windings are wound for 6 volts and 20 amperes. In charging a magnet the ends of the horseshoe are brought up against an iron core of the coil in such position that the magnet is attracted and not repelled by the core. The magnet is then pushed through the

apertures in the centers of the coil boxes, taking the place of the iron core, which is slowly pushed out. The current is then connected for merely the length of time required in touching one of the terminals of the wire to the binding post two or three times. A keeper is then laid across the part of the magnet arch which projects beyond the coil boxes, and with the keeper still in place the magnet is replaced on the magneto. It is stated that a freshly charged Tungsten steel magnet of a large magneto will lift in the

Fig. 129.—How to Test Magneto with Spark neighborhood of 20 lbs.

Plugs Under Air Pressure.

as ordinarily energized

by the magneto manufacturer. It is stated that with this device' the magnet pull can be increased to 30 lbs., which, of course, means a stronger magnetic field when reassembled on the magneto.

The strength of a repaired magneto can be easily tested by the simple device shown at Fig. 129. Spark plugs are screwed into an air-tight box with glass cover and air is pumped into the box so that a pressure of 100 pounds is shown on gauge. The spark plugs are

connected to the distributor contacts. The armature is revolved by any suitable means and sparks should jump the spark plug air gaps.

Application of Typical Magneto Forms.-The usual method of installing a magneto is to place it on a bracket fastened to the

engine base so the contact breaker and distributor will be handy for immediate inspection or adjustment. It is desirable to place the device on the inlet side of the engine and as far away from the exhaust piping as possible, because of the excess heat which exists at this point is liable to injure the insulation of the windings.

Methods of installation which are typical of conventional practice are shown at Fig. 130. At A the magneto is placed on a cast bracket formed integral with the top half of the engine base and is driven from the timing case at the front of the engine by a length of shaft. At B the magneto is also housed at the rear end and is carried on a base plate formed integrally with one of the crank-case supporting arms. The drive is by an extension of the pump shaft, that member being driven by suitable gearing in the cam-shaft timing gear casing.

Gear drive is the best method of driving a magneto armature and direct spur-gear connection is better than either bevel or spiral gear trains because it is the best wearing form of gearing. Silent chains may be used for driving if some form of adjustment is provided to compensate for chain stretch. When a magneto is driven by a shaft, as shown at Fig. 132, A and B, it is customary to provide some sort of a universal joint or Oldham coupling between the armature and the driving member in order that any inaccuracies in alignment of the driving shaft will not stress the ball bearings supporting the armature. It is desirable to protect the instrument from oil or water by placing it in a case of fiber or leather, and in modern types the contact breaker and distributor housings are closed by easily removed and yet practically dust-tight coverings.

Metallic or carbon particles and dirty oil may cause internal short circuiting and it is desirable to have the contact-maker case and the distributor cover arranged in such a way that they may be easily reached for cleaning. Modern magnetos are usually secured in some way that will permit a ready removal. In that shown at A, Fig. 130, a number of through bolts are screwed from the under side of the bracket into the magneto base and it is necessary to remove these before the magneto can be lifted off its support. The method shown at Fig. 130, B, is preferable as the ignition device may be removed from the base by slackening one nut on the hinge bolt which keeps the metallic strap tight, thus holding the magneto in place.

Various other methods of utilizing strap members are shown at Fig. 133. In that shown at A the strap is made in two pieces and is held together at the top by a clamp bolt. The method of securing