Switchable systems Ignition system

switchable magneto ignition circuit, starting battery.

the output of magneto depends on speed of engine, , therefore starting can problematic. magnetos include impulse system, spins magnet @ proper moment, making easier starting @ slow cranking speeds. engines, such aircraft ford model t, used system relied on non rechargeable dry cells, (similar large flashlight battery, , not maintained charging system on modern automobiles) start engine or starting , running @ low speed. operator manually switch ignition on magneto operation high speed operation.

to provide high voltage spark low voltage batteries, tickler used, larger version of once widespread electric buzzer. apparatus, direct current passes through electromagnetic coil pulls open pair of contact points, interrupting current; magnetic field collapses, spring-loaded points close again, circuit reestablished, , cycle repeats rapidly. rapidly collapsing magnetic field, however, induces high voltage across coil can relieve arcing across contact points; while in case of buzzer problem causes points oxidize and/or weld together, in case of ignition system becomes source of high voltage operate spark plugs.

in mode of operation, coil buzz continuously, producing constant train of sparks. entire apparatus known model t spark coil (in contrast modern ignition coil actual coil component of system). long after demise of model t transportation remained popular self-contained source of high voltage electrical home experimenters, appearing in articles in magazines such popular mechanics , projects school science fairs late 1960s. in uk these devices commonly known trembler coils , popular in cars pre-1910, , in commercial vehicles large engines until around 1925 ease starting.

the model t (built flywheel) differed modern implementations not providing high voltage directly @ output; maximum voltage produced 30 volts, , therefore had run through spark coil provide high enough voltage ignition, described above, although coil not buzz continuously in case, going through 1 cycle per spark. in either case, low voltage switched appropriate spark plug timer mounted on front of engine. performed equivalent function modern distributor, although directing low voltage, not high voltage distributor. timing of spark adjustable rotating mechanism through lever mounted on steering column. precise timing of spark depends on both timer , trembler contacts within coil, less consistent breaker points of later distributor. however, low speed , low compression of such engines, imprecise timing acceptable.