There is an interest and much discussion about the Model T timer having a dwell time. With the introduction of the Model T in 1908, and the other Fords, and certain vehicles, of the period the roller timer was main part of the ignition. In 1909, Automobile Industries (January 7, 1909), A. Atwater Kent presented a paper and included a demonstration of an early "contact maker" ignition. In his presentation, and later patent, he discusses ignition reliability. He contrast, in his words, the duration of contact dwell of the roller timer and that of his contact maker (points). Was Kent wrong in his discussion about the dwell of the roller timer as found on Fords?
Without reading the article, I would assume the concept of dwell has to do with dry-cell battery life. Longer dwell causes the battery to have less life per mile. An Atwater-Kent distributor of the era had a special point arrangement that snapped open the points for a relatively fixed dwell time regardless of engine speed.
Kent made distributor type ignition conversions. His words are sales tactics designed to convince you to buy his expensive device to replace your inexpensive and utterly reliable Ford roller timer. His words are just words, intended to sell, not educate.
In short George there is no use for the term "dwell" when discussing the Model T ignition timer.
We could "dwell" on this subject for a long time!
I would concede to a point that the design of a roller timer, as in the Ford ignition (and others), does not conform to having dwell or a dwell. To have dwell, with an ignition system using points, the dwell is the motion during which the points are at rest. Yet dwell also implies a mechanism of sequencing when the roller or shoe makes contact to activate a coil. In a sequence of the firing order 1,2,3,4. The period between the firing sequence - inactivity of the coils - is a period of dwell.
Now you are making up a story to fit the conclusion that you desire.
Ignition system for explosion-engines.
US 915639 A Patented Mar. 16, 1909
""This invention relates to ignition systems for explosion' engines, and more particularly to an arrangement by which the duration of the primary circuit closure is varied with respect to the stroke of the engine.
"" The ordinary circuit-controlling device for an ignition system is driven by the engine and closes the circuits of an induction coil, or, more generally, a plurality of induction coils at fixed intervals and for a predetermined duration or "dwell." The longer the period of circuit closure or dwell, the more certain the ignition becomes, but on the other hand, a longer a circuit closure consumes excessive battery current, and in many cases uselessly, since the engine ordinarily operates properly with very short current duration.""
This was designed by Richard Varley, of the Autocoil Company, New Jersey. The circuit diagram, with the four induction coils, is similar to the design of the ignition system of the timer and Ford coils including magneto and battery.
This circuit for ignition - although battery powered - includes a timer with roller and four induction coils. The date is 1909. Included in the description is the word dwell describing that the coils are activated " (at) fixed intervals and for a predetermined duration."
Looks like Fred may be right, may the discussion continue. I think the timer roller dwells in the timer housing and the Model T coil points dwell on top of the coil . Most cows dwell in the country where the best Model T roads are found.
I remember asking my DAD close to 60 years ago when i found a Atwater Kent dist in the barn.He said the best thing about it was it got everything out of the dirt up where you could see it!! I wish my DAD could have seen my T's! Bud in Wheeler,Mi.