Timer question

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Model T Ford Forum: Forum 2012: Timer question
Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Shirley on Monday, December 31, 2012 - 07:55 pm:

Why is the duration of the spark so long on a T? If the contact on the inside of the timer was a few thousandths long would it not save on the points and coils?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Matthew David Maiers on Monday, December 31, 2012 - 08:19 pm:

thats a loaded question. one that i have been learning about recently.

the model t ignition is designed to run on magneto, and when running on magneto the coil does not fire that entire duration, it only fires as the magnet passes by the winding on the magneto.

per cylinder the coil can spark in 3 places in relating to crank position and the timer essentially selects which position the coil will fire at.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Matthew David Maiers on Monday, December 31, 2012 - 08:21 pm:

did i do a good job Tom! lol


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tom Carnegie on Monday, December 31, 2012 - 08:22 pm:

I have a theory on this. I believe the duration is more or less a multiple of 22.5 degrees of crank rotation so that the contact and uncontact will be made when the current from the mag is as close to zero as possible. I think the designers wanted the contact to cover at least a couple cycles of the mag. I don't know the reason for this. One cycle should have been enough. Two cycles equals 90 degrees, which is the dwell of most timers.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tom Carnegie on Monday, December 31, 2012 - 08:23 pm:

You beat me Matthew.


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