magnetos

A magneto is a compact, self-contained electrical generator that uses permanent magnets to produce electricity through electromagnetic induction. In engines and machinery, magnetos are commonly used to provide a timing-coordinated ignition spark and, in some designs, to supply power without relying on an external electrical source. They have been widely used in aircraft, motorcycles, lawn and garden equipment, and early automobiles.

Construction and operation: A magneto consists of a rotor with permanent magnets, a stationary core with windings (stator), and a breaker mechanism to interrupt current. As the rotor spins, changing magnetic flux induces voltage in the windings. In ignition magnetos, the breaker points periodically open and close the primary circuit; when opened, the collapsing magnetic field generates a high-voltage pulse in the secondary winding that fires the spark plug. Timing is controlled by mechanical advance/retard mechanisms and, in some designs, impulse couplers.

Types and configurations: Magnetos can be designed to deliver high-voltage pulses directly to spark plugs (high-tension magnetos) or to provide a low-voltage output to an external ignition coil (low-tension magnetos). Aircraft magnetos are typically built for redundancy and reliability, often installed in pairs, and may include impulse starters for cold starts. Some modern refinements integrate ignition components within the magneto or adapt to electronic ignition alternatives, but the core device remains a magnet-based generator.

Applications and history: Magnetos were a primary ignition source in many engines during the early to mid-20th century, valued for independence from batteries and consistent performance. Today they remain standard in many light aircraft and in some small or vintage engines, where reliability and simplicity are prioritized. They are less common in modern automotive engines, which favor electronic ignition systems.