Dwell is the amout of degrees of distributor rotation that the points are closed. Dwell is usually close to 50% of the allotted time for each cylinder. The larger the dwell (kettering) the longer the coil is turned on and the greater the saturation of the buildup of magnetism in the coil body. As RPM increases, the time allotted, in milliseconds, decreases. If 8 cylinders in a car turning 4500 rpm are discussed we can see that the saturation time per spark goes way down. But !!! the % of on time remains the same at about 50%. Thus the coil heat buildup is the same at all speeds except stopped. When stopped, the coil is almost always on if the key is on. Thus burning up the coil because its duty cycle is 50%, not 100%. Mags need rotor speed to make sufficient voltage when hand cranked (essentially no rpm) and thus must have an impulse coupling to hold back, then release the rotor so it spins as fast as the tractor Idle speed or more. at that RPM the energy is saturating the primary windings and coil very well. Thus the magnetism is sufficient to build magnetism in the coil laminations and throughout the secondary windings such that when the points break, the collapse is sufficient to build voltage till the resistance of the gaps is overcome. Remember that at higher RPm the time for saturation buildup is reduced for both Kettering and mag systems. I hope this helps. Jim
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Today's Featured Article - My Ford Golden Jubilee - by Troy Estes. This article is about my '53 Ford Jubilee and a story that starts with taking the tractor to my brother's Starter/Alternator Rebuilding shop for a wiring fix. The generator was shot as well as all the wiring. I dropped off the tractor expecting a transformation from a 6 volt to a 12 volt system utilizing the original generator housing, and a total rewiring of the whole tractor. The front end center pin bushing was worn also so I ask that they replace it if they had time. Well, that’s wha
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