A magneto is small generator formed from a permanent magnet, which uses electricity to give outputs such as pulses of high voltage. A magneto has a transformer, switch and distributor, which give alternating current the direction to the plug that produces sparks. Timing in magneto is the interval in which the breaking point occurs after producing the sparks. Therefore, the purpose of magneto timing is to actualize high voltage used to produce sparks at the right time. It is achieved through the internal and external timing. Internal timing takes place mechanically on a bench. There are two adjustments in a magneto to help in accomplishing its work. In this case, the magneto is located outside the engine and the opening of the point must occur at the right place during the rotation of the magneto, just as the E-gap. The opening is then set while the point gaps are placed adjacently to the rotor. If correct timing is done internally, the magneto should produce strong hot sparks. However, if the timing is done wrongly, the magneto achieves weak sparks and sometimes may not produce any sparks.
External magneto timing takes place mechanically and electrically. It cautions on the correct engine operation. It is specifically within certain degrees and checked after 100 hours. It starts with internal adjustment then the mounting of magnetos is done on the engine while maintaining the correct timing of ignition. A spark plug is removed in the cylinder while the crankshaft is rotated to achieve a top dead center position. Once the position is achieved, the crankshaft is rotated to a certain angle, mostly 20 degrees, before the top dead center position (Ashley & Franck, 2003). The new position becomes the firing position. The buzz box is used to get adjustment to ensure effective opening at every position, which is desired for firing. The adjustments are made through loosening the base clamps of the magneto while mounting the magneto on the engine pad through rotating until an opening of the points is achieved. Finally, the base clamps are tightened and the external timing is rechecked.
External magneto timing has several purposes. First, it helps in bumping the magneto. After checking the ignition timing after 100 hours cautiously, mostly a direction drift is witnessed. This is due to wear on frictional blocks and point erosion, which open the points and retard the ignition timing. This also makes drifting of the internal timing from E-gap thus, causing a decrease of the sparks quality produced by the magneto. The external timing gives a timing drift, which occurs since the setting of the E-gap. It helps in bumping the magneto thus bringing the time to specifications.
Secondly, it helps in starting an airplane. For an engine to start, two factors are considered. One of the factors is the way a magneto can be coaxed to produce enough energy used in firing spark plugs in a slow soothing speed. The other factor is the way to slow a spark to ensure successful cranking of the engine without backfiring. Only the external magnetos can be used to achieve the two factors through mechanical and electrical methods.
Thirdly, external magneto helps in impulse coupling. It is a unique mechanical way of solving occurring problem during ignition. It is contained in a hub attached to the shaft drive of a magneto that joins to the engine. When the engine starts, the hub catches on a stop pin and stops the magneto shaft from moving. When the engine starts to move, an impulse forms in the hub at an angle of 25 degrees to 35 degrees of the rotating engine until the tripping of the coupling body occurs (Podrapsky & Orova, 1980). This occurs successfully due to the use of an external magneto. Finally, it helps in preventing misfire in high-altitude areas when taking a flight. It is done through easing the formation of sparks where they should occur by tightening the gap in the spark plug or hardening its formation where it is not applicable by fitting engines with slick mags.
References
Podrapsky, J., & Orova, J. (1980). U.S. Patent No. 4,188,929. Washington, DC: U.S. Patent and Trademark Office.
Ashley, J., Rae, J. W., & Franck, S. J. (2003). U.S. Patent No. 6,587,292. Washington, DC: U.S. Patent and Trademark Office.
