Page:Motors and motor-driving (1902).djvu/186

154 shield of the magneto machine is moving at this point the side of the envelope moving from the armature  should be clear of the same by about one-sixteenth of an inch. The setting can be done by varying the length of the magneto driving rod if adjustment is provided there, or if not by loosening the nut at the end of the magneto spindle and gently tapping the edge of the armature till the correct setting is obtained. The final adjustment should be made on the tappet, which should strike the sparking lever's about one-sixteenth of an inch before reaching its lowest point, the exact distance being found by examining the spark (turning the motor smartly round for this purpose) and adjusting the tappet till the best spark is obtained. The lock-nut should then be screwed up.

.—As pointed out, in the Simms-Bosch system a mechanical interrupter is necessary in the combustion chamber, owing to the low pressure employed. To obviate this somewhat undesirable adjunct, Messrs. Dawson have introduced a high-pressure magnetic machine. The magneto itself generates electricity at low pressure, which is transformed by means of a special induction coil into a high-pressured current. An ingenious arrangement enables the current to be distributed to any number of cylinders without the necessity of more than one induction coil, and moreover allows the advancement of the spark throughout a complete revolution of the engine.

The machine is worked in conjunction with ordinary sparking plugs on the De Dion principle, and being self-contained can be quickly and easily fitted to any car. The magneto is driven off the main shaft of the engine, and at the same speed, by means of a chain.

The motion being rotary, much less wear should be experienced than with oscillating machines.

Owing to the short time this machine has been on the market, it has been found impossible to obtain data as to its reliability in actual practice.