when i went to ap school (2009), the books mentioned something in the design of a magneto called "safety gap". this apparently is a design feature in a traditional points fired magneto that allows all of the energy produced by the secondary coil to be dissipated if the normal electrical route to a spark plug' electrodes is broken or interupted for any reason. i have what i figure is all or most of the manufacturer's manuals for both the s-20 series (s4r/l) and sf series bendix mags, and have overhauled both, but have never seen any mention of a safety gap. maybe in the 40's this term hadn't been thought of yet. i've never worked on slick's so don't know if their manuals mention such a thing.
on the bendix sf mags (the old brick mags), there are two carbon brushes, the main one bringing energy from the coil to the cylinder for routing to the posts and onto the wires, but there is also a small one internal to the cylinder which fits in the end of the cylinder axle, and i've never been able to figure out what that brush is for. maybe if the normal path is interupted, the energy goes through the cylinder dielectric material to the inner brush for routing to ground on the mag case????? maybe that's a safety gap. on the bendix s4r/l series, i have no idea.
anyone know what would happen to your mag if say theoretically a plug wire fell off in flight and the wire tip was miraculously insulated from arcing to ground somewhere in the engine bay. would your mag arc and spark internally to dissipate that energy until destroyed????
so there's your brain teaser all you hobbyists, tinkerers, engineers and engineer wannabees, ap and ia's!!
on the bendix sf mags (the old brick mags), there are two carbon brushes, the main one bringing energy from the coil to the cylinder for routing to the posts and onto the wires, but there is also a small one internal to the cylinder which fits in the end of the cylinder axle, and i've never been able to figure out what that brush is for. maybe if the normal path is interupted, the energy goes through the cylinder dielectric material to the inner brush for routing to ground on the mag case????? maybe that's a safety gap. on the bendix s4r/l series, i have no idea.
anyone know what would happen to your mag if say theoretically a plug wire fell off in flight and the wire tip was miraculously insulated from arcing to ground somewhere in the engine bay. would your mag arc and spark internally to dissipate that energy until destroyed????
so there's your brain teaser all you hobbyists, tinkerers, engineers and engineer wannabees, ap and ia's!!
